# Menu 3 − Regen Set-up

Mode: Regeneration

Once the d.c. bus voltage has reached a suitable level the charge system is disabled. Then when the final drive enable is made active the system can measure the supply voltage and frequency with a short pulse test and then the system becomes synchronised for normal running. The pulse test is always used in grid-connected mode, is optional in grid-supporting mode, and is not used in grid-forming mode.

A monitoring system is provided to detect supply loss (either from the voltage at the output of the converter or from some other measured voltage), phase loss, phase imbalance or that the converter is connected to an islanded supply.

The diagram below shows how the current references are derived for grid-connected mode. For other grid modes see Menu 1.

Parameter | 03.001 Reactive Power
--- | ---
Short description | Reactive power measured at the converter terminals.
Mode | Regeneration
Minimum | −VM_POWER | Maximum | VM_POWER
Default |  | Units | kVAr
Type | 32 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 3
Coding | RO, FI, VM, ND, NC, PT

This gives the reactive power at the converter terminals. See Regen Sub-mode (01.003) for the polarity of this parameter.

Parameter | 03.003 Charge System Present
--- | ---
Short description | This should be set to zero if there is no charge system present in the system.
Mode | Regeneration
Minimum | 0 | Maximum | 1
Default | 1 | Units |
Type | 1 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW, BU

When a contactor is closed to connect the system to a live supply there is normally an inrush current while the d.c. bus capacitors are charged via the anti-parallel diodes in the system converter. To limit this current to a safe level that does not blow any fuses or damage the converter, a charge system is used. If the d.c. bus is already at a voltage higher than the rectified supply because of a power source connected to the d.c. bus or the system is being started on to a grid connection that is not live (i.e., Grid Mode (01.010) = 2 (Grid-forming)), then a charge circuit is not required. If this parameter is set to zero to indicate that there is no charge circuit, then Disable Charge System / Close Contactor (03.007) is still controlled but Charge System Disabled / Contactor Closed (03.008) does not need to be set to one by a system monitoring the charge circuit before the system can become enabled.

Parameter | 03.004 Regen Synchronisation Mode
--- | ---
Short description | Action taken by the system to synchronise to the supply.
Mode | Regeneration
Minimum | 0 | Maximum | 3
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | Re-synchronise
1 | Delayed Trip
2 | Immediate Trip
3 | Auto-synchronise

Synchronisation tests are carried out to measure the frequency, voltage and phase of the supply connected to the converter when it is enabled and connected to a live supply to minimise current transients on starting. The tests are carried out for different grid modes as given in the table below.

Grid Mode (01.010) | When tests are carried out
Grid-connected (default) | The system is always connected to a live supply, so the tests are carried out on every start or if synchronisation is lost after synchronising for the first time.
Grid-forming | The system is providing the supply, so tests are never required.
Grid-supporting | Start Mode (01.050) = 0 (Active Start): Always. Start Mode (01.050) = 1 (Black Start Once): Not on starting, but only if re-synchronising. Start Mode (01.050) = 2 (Black Start): Never.

The test does not start until the following conditions are met:

1. The d.c. bus voltage must be high enough so that the system is not in the under-voltage state. See Standard Under Voltage Threshold (06.065).
2. Either Charge System Present (03.003) = 0 (to indicate there is no charge system present) or Charge System Disabled / Contactor Closed (03.008) = 1 to indicate that the charge circuit has been bypassed.
3. Final Drive Enable is active (see Menu 6) and Drive Healthy (10.001) = 1.
4. If Supply Voltage Detection Mode (03.029) = 0 (Measured dc) the d.c. bus voltage must have stopped rising or falling. This voltage is used to estimate the supply voltage to preset the system but the measurement is only reliable when the d.c. bus voltage has settled to the rectified supply voltage after any previous actions that could have changed it from this level.
5. D.c. Bus Voltage (05.005) < Maximum d.c. bus voltage x (100% - Synchronisation Headroom (03.035)).
6. In grid-connected mode Faults Active (01.014) must be zero.

If the test is not to be performed the system simply becomes active if conditions 1 to 3 above are met. If the test is performed and is successful (i.e., the supply frequency can be measured and is within the limits defined by Minimum Supply Frequency (03.024) and Maximum Supply Frequency (03.025), and the estimated voltage and phase are correct) the system becomes active and operates in the required grid mode. The following conditions cause the system to become unsynchronised for each grid mode.

Grid Mode (01.010) | Conditions below this table that cause the system to become unsynchronised
Grid-connected (default) | All conditions.
Grid-forming | No conditions as the system cannot become unsynchronised.
Grid-supporting | Condition 1 only.

1. A supply transient is large enough to cause an over-current condition.
2. The supply frequency changes to within 5Hz of the allowed range defined by Minimum Supply Frequency (03.024) and Maximum Supply Frequency (03.025).
3. Supply Loss (10.015) = 1.
4. A phase is disconnected or there is a high level of supply imbalance and there is a reasonable level of current flow with the supply.

If grid-connected mode is active and Regen Synchronisation Mode (03.004) < 3 the system attempts to resynchronise or trips as described below. If Regen Synchronisation Mode (03.004) = 3 the system can attempt to remain in synchronism with the supply even if the supply voltages are not suitable for detecting the phase of the supply or for keeping the phasor representing the supply angle within the converter control rotating smoothly (i.e., there a high level of phase imbalance). This is done by simulating the phase angle of the supply based on its state before a fault occurs that distorts the supply. This simulation mode is triggered if Supply Loss (10.015) becomes active, or Action On Phase Imbalance (01.012) = 1 and Phase Imbalance (10.082) become active.

0: Re-synchronise
This is the default mode and the system will continuously attempt to synchronise to the supply. If an over-current condition is detected it is reset.

1: Delayed Trip
The system operates in the same way as "Re-synchronise" mode except that a Line Sync trip is initiated after 30s if either the drive has lost synchronisation while active or if the drive has failed to synchronise to the supply after being enabled.

2: Immediate Trip
The system operates in the same way as "Re-synchronise" mode except that a Line Sync trip is initiated immediately if synchronisation is lost while active or after 30s if the drive has failed to synchronise to the supply after being enabled.

3: Auto-synchronise
This mode is only relevant to grid-connected mode. Synchronisation is not used in grid-forming mode and the "re-synchronise" option is always used in grid-supporting mode. The diagram below shows the sequence during a fault. At point A the fault occurs and if an over-current condition is detected it is reset. The time from point A ;to point B is between 0 and 4ms and during this period no current can flow. From point B the system will simulate the supply angle based on the supply conditions before the fault occurred. It is possible for reactive current to flow into the supply in the normal way, but the active current is held at zero. As the active current is held at zero the d.c. bus must be held at the required level by whatever is connected to the d.c. terminals of the system. Supply Loss Threshold (03.023) should be set to a level that is higher than the likely voltage seen at the inverter terminals due to any current being fed into the supply (e.g. 10% of nominal supply voltage) or else the system will attempt to synchronise to its own output voltage. Phase imbalance detection is only included if Action On Phase Imbalance (01.012) = 1, and if this is being used Phase Imbalance Threshold (03.040) should be set to a level where the converter can operate in a stable way.

After the supply loss or an imbalance fault is detected Faults Active (01.014) is non-zero and the supply simulation begins and remains active until the supply recovers (C), or the end of the ride-through period is reached as defined by Fault Ride-through Time (01.017) (D) and then the action specified in Action On Fault (01.015) is taken. If Action On Phase Loss (01.011) = 1 and Phase Loss (10.081) = 1, or Action On Island Detected (01.013) = 1 and Island Detected (10.083) = 1, then the action specified in Action On Fault (01.015) is taken immediately.

Parameter | 03.005 D.c. Voltage Set Point
--- | ---
Short description | Voltage set point for the d.c. bus controller.
Mode | Regeneration
Minimum | −VM_DC_VOLTAGE_SET | Maximum | VM_DC_VOLTAGE_SET
Default | See exceptions below | Units | V
Type | 16 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 0
Coding | RW, VM, RA

Voltage | Default Value
200V | 350
400V | 700

If Grid Mode (01.010) = 0 (grid-connected mode), Power Input Mode (03.012) < 2 and Active Current Reference Selector (04.010) = 0 the d.c. bus voltage controller is active and the system attempts to hold the d.c. bus voltage at the level specified by D.c. Voltage Set Point (03.005). This must always be higher than the peak of the line to line supply voltage if the unit is to operate correctly, i.e. greater than or equal to (Vllrms x √2) + 50V, where Vllrms is the r.m.s. line supply voltage. The default values can be used with most supplies giving a reasonable level of control headroom. However, with higher voltage supplies the set-point must be raised.

Parameter | 03.006 D.c. Voltage Controller Proportional Gain Kp
--- | ---
Short description | d.c. bus voltage controller proportional gain.
Mode | Regeneration
Minimum | 0 | Maximum | 65535
Default | 4000 | Units |
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, BU

When the d.c. bus voltage controller is active a PI controller is used to control the d.c. bus voltage to the set-point defined by D.c. Voltage Set Point (03.005). The proportional gain can be adjusted with this parameter but the integral gain is fixed. The power input parameters (Power Input 1 (03.010), Power Input 2 (03.013), Power Input 3 (03.014) and Power Input kW (03.018)) are provided to give a power feed forward term, at the output of the PI controller, from the motor drives connected to the d.c. bus. If possible the power feed forwards should be used so that the PI controller is simply providing a trim to the d.c. bus voltage. In most cases it is not necessary to change D.c. Voltage Controller Proportional Gain Kp (03.006) from its default value unless the total d.c. bus capacitance is lower than the expected nominal level or the response of the system to power transients needs to be modified (the latter is discussed below). The default gain is suitable if both the Regen drive and motor drive with their d.c. buses connected are standard Unidrive M products. However, if only the Regen drive is present it may be necessary to reduce D.c. Voltage Controller Proportional Gain Kp (03.006) to give stable operation. Also the d.c. bus capacitance of Digitax HD products is less than a standard Unidrive M product for the same full scale current (Full Scale Current Kc (11.061)), and so the gain is likely to need to be reduced if the Regen drive is a Digitax HD drive.

For the purpose of analysing the voltage controller response it is assumed that a power feed-forward term is not provided. If the power flow from the d.c. bus is increased (i.e. motor is accelerated by a motor drive connected to the d.c. bus) the d.c. bus voltage will fall, but the minimum level will be limited to just below the peak rectified level of the supply provided the maximum rating of the unit is not exceeded. If the power flow to the d.c. bus is increased (i.e. motor is decelerated by a motor drive connected to the d.c. bus) the d.c. bus voltage will rise. A rise in d.c. bus voltage also occurs if the motor drive is loaded with a motoring load and this drive is disabled but the Regen drive is not disabled. If the peak of the d.c. bus voltage reaches the over voltage level the regen drive will trip. A rapid transient where power into the d.c. bus is increased is shown below.

The example shown is for a very rapid load change where the torque reference of the motor drive has been changed instantly from one value to another. The proportional term in the controller limits the peak in the d.c. bus voltage, and the maximum transient is given by

ΔVdc = ΔpOut x (400 x VdcFullScale / √3) / (D.c. Voltage Controller Proportional Gain Kp (03.006) x Full Scale Current Kc (11.061) x VSupply)

ΔVdc = ΔpOut x K / (D.c. Voltage Controller Proportional Gain Kp (03.006) x Full Scale Current Kc (11.061) x VSupply)
K = 400 x VdcFullScale / √3

Drive Rated Voltage (11.033) | VdcFullScale | K = 400 x VdcFullScale / √3
200V | 415V | 95840
400V | 830V | 191680
575V | 990V | 228630
690V | 1190V | 274819

For example using a 400V, 7.5kW drive with D.c. Voltage Controller Proportional Gain Kp (03.006) = 2000 on a 400V supply, then a 7.5kW power transient gives

ΔVdc = 7500 x 191680 / (2000 x 38.222A x 400) = 47V

The recovery time constant for the d.c. bus voltage is given by

τ = D.c. Voltage Controller Proportional Gain Kp (03.006) / 30400

So far the discussion has been related to the d.c. bus voltage controller gain, however, the controller provides the active current reference to the regen drive current controllers, and so the current controller gains affect the response of the voltage controller. If the default voltage controller gain is used and it is possible to obtain a stable response from the current controllers with their default gains, then the voltage controller response will be stable. However, in some cases it will be necessary to reduce the current controller gains to make these controllers stable, in which case it is likely that the voltage controller gain will need to be reduced to make this controller stable.

It is possible to disable the d.c. bus voltage controller. See Active Current Reference Selector (04.010). It should be noted that if D.c. Voltage Controller Proportional Gain Kp (03.006) is set to zero, this will disable the proportional term of the PI controller that controls the d.c. bus voltage, but not the integral term. Therefore Active Current Reference Selector (04.010) should be used to disable the d.c. bus voltage controller.

Parameter | 03.007 Disable Charge System / Close Contactor
--- | ---
Short description | Routed via a digital output to control the charge system contactor.
Mode | Regeneration
Minimum | 0 | Maximum | 1
Default |  | Units |
Type | 1 Bit Volatile | Update Rate | 4ms write
Display Format | Standard | Decimal Places | 0
Coding | RO, ND, NC, PT

When a contactor is closed to connect the system to a live supply there is normally an inrush current while the d.c. bus capacitors are charged via the anti-parallel diodes in the system converter. To limit this current to a safe level that does not blow any fuses or damage the converter, a charge system is used as shown below. The charge circuit can be resistor based or the thyristor charging system in the drive. The sequencer provides an output which is used to disable or enable the charge system (Disable Charge System / Close Contactor (03.007)) and this is routed via a digital output, so that when Disable Charge System / Close Contactor (03.007) = 0 the charge system is connected between the supply and the system. When Disable Charge System / Close Contactor (03.007) = 1 the charge system is bypassed and the converter terminals are connected to the supply. To allow the state of the charge system to be monitored so that the system does not attempt to synchronise or run with the charge system active an auxilliary contact on the contactor is routed to Charge System Disabled / Contactor Closed (03.008). Synchronised (03.009) is routed to the enable of the motor drive to prevent it from being active until the regen system is fully active. If a charge system is not being used Charge System Present (03.003) should be changed to zero so that Charge System Disabled / Contactor Closed (03.008) does not need to be active to allow the system to become fully active.

As an alternative to disabling the motor drive during supply-loss, auto-synchronisation can be used and Hold Supply Loss Active (06.051) in the motor drive can be used to keep the drive in the supply loss condition until the ride-through condition is no longer active as shown below. When the supply loss occurs the regen system will stay active and indicate to the motor drive that supply loss must stay active until 100ms after the supply has recovered.

Parameter | 03.008 Charge System Disabled / Contactor Closed
--- | ---
Short description | Routed from a digital input to feedback the state of the charge system contactor.
Mode | Regeneration
Minimum | 0 | Maximum | 1
Default |  | Units |
Type | 1 Bit Volatile | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 0
Coding | RO, ND, NC

See Disable Charge System / Close Contactor (03.007).

Parameter | 03.009 Synchronised
--- | ---
Short description | Indicates that the system is active and synchronised to the supply, or is providing a supply
Mode | Regeneration
Minimum | 0 | Maximum | 1
Default |  | Units |
Type | 1 Bit Volatile | Update Rate | 2ms write
Display Format | Standard | Decimal Places | 0
Coding | RO, ND, NC, PT

This parameter is active when the system is enabled and synchronised to the supply or completed a black-start as appropriate.

Parameter | 03.010 Power Input 1
--- | ---
Short description | Power feed-forward 1 from an analogue input.
Mode | Regeneration
Minimum | -100.0 | Maximum | 100.0
Default | 0.0 | Units | %
Type | 16 Bit Volatile | Update Rate | 250µs read
Display Format | Standard | Decimal Places | 1
Coding | RW, NC

See Power Input Mode (03.012).

Parameter | 03.011 Current Trim Mode
--- | ---
Short description | Controls whether current trimming is carried out once at power-up or each time the system is enabled.
Mode | Regeneration
Minimum | 0 | Maximum | 2
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | Power-up
1 | On Enable
2 | Disconnect Mode

A current feedback trimming routine runs before the system is enabled to minimise offsets in the current feedback. If Current Trim Mode (03.011) = 0 (Power-up) the current offset trim is only carried out once when the drive comes out of the under voltage state and is not repeated unless the supply is removed and reapplied. The current offset trim is only carried out when the charge system is enabled (contactor open) as this minimises current flowing into the inverter terminals due to noise on the supply that may disturb the current offset trimming.

Current Trim Mode (03.011) should be set to 1 (On Enable) if the current offset trim is required each time when the regen drive is enabled. To ensure that the current offset trim is not disturbed by noise on the supply, the charge system is enabled before the current offset trim and then disabled again before the system goes into its active state. This causes the charge system contactors to switch each time the system is enabled.

If Current Trim Mode (03.011) is set to 2 (Disconnect Mode), then the charge circuit is opened on disable and the current trim sequence is carried out as described for "On Enable" mode. If the charge system contactor is connected between the supply and the switching frequency filter capacitors, then this mode can be used to minimise the fundamental current taken from the supply when the converter is disabled.

Parameter | 03.012 Power Input Mode
--- | ---
Short description | Selects power feed-forward or the power set-point.
Mode | Regeneration
Minimum | 0 | Maximum | 2
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | Feed-forward
1 | kW Feed-forward
2 | Power kW

See Regen Sub-mode (01.003) for the polarity of Power Input 1 (03.010) to Power Input 3 (03.014) and Power Input kW (03.018).

Feed-forward:
The d.c. bus voltage controller is active and uses the active current to control the d.c. voltage. Power Input 1 (03.010) to Power Input 3 (03.014) can be used as power feed forwards to assist the voltage controller during transient change in a system connected to the d.c. bus, such as a motor drive. If Power Output (07.033) from a motor drive is routed to an analogue output with unity scaling it produces full scale output when the power is equal to 3 x (VM_DC_VOLTAGE[MAX] / 2√2) x Full Scale Current Kc (11.061). If this signal is connected to an analogue input on this regen drive, the input is routed to Power Input 1 (03.010) and Power Input 1 Scaling (03.015) is set to the ratio of the current scaling values for the motor drive and regen drives (i.e. motor drive Full Scale Current Kc (11.061) / regen drive Full Scale Current Kc (11.061)), then the correct power feed-forward term will be provided. The default value for Power Input 1 Scaling (03.015) is 1.000, and so unless the regen and motor drives are the same size this parameter will need to be adjusted. Up to 3 motor drives connected to the regen drive d.c. terminals can use this system to provide power feed-forward as each of the power inputs are summed to give the final power feed-forward term.

kW Feed-forward:
If more than 3 motor drives are connected to the d.c. terminals of the regen drive, or a digital power feed-forward system is required, then Power Input kW (03.018) should be used. The power in kW can be transferred from each motor drive using fast synchronous communications to an application module in the regen drive. The total power in kW should be calculated by the applications module and then written to the Power Input kW (03.018). For the power feed-forward to be effective data should be transferred every 250μs with the minimum delay (i.e. 500μs) and the total power written to Power Input kW (03.018) every 250μs.

Power kW:
The d.c. bus controller is disabled and the active current reference can be calculated from Power Input kW (03.018) and Reactive Power Input kVAR (03.020). If both the active and reactive current references are not being derived from Power Input kW (03.018) and Reactive Power Input kVAR (03.020), then Vd (05.086) is assumed to be zero and the active reference is derived from Power Input kW (03.018) alone. This does not give the best accuracy if Vd (05.086) and Vq (05.087) are being derived from measured voltages, and so it is preferrable to derive both current references from Power Input kW (03.018) and Reactive Power Input kVAR (03.020).

Parameter | 03.013 Power Input 2
--- | ---
Short description | Power feed-forward 2 from an analogue input.
Mode | Regeneration
Minimum | -100.0 | Maximum | 100.0
Default | 0.0 | Units | %
Type | 16 Bit Volatile | Update Rate | 250µs read
Display Format | Standard | Decimal Places | 1
Coding | RW, NC

See Power Input Mode (03.012).

Parameter | 03.014 Power Input 3
--- | ---
Short description | Power feed-forward 3 from an analogue input.
Mode | Regeneration
Minimum | -100.0 | Maximum | 100.0
Default | 0.0 | Units | %
Type | 16 Bit Volatile | Update Rate | 250µs read
Display Format | Standard | Decimal Places | 1
Coding | RW, NC

See Power Input Mode (03.012).

Parameter | 03.015 Power Input 1 Scaling
--- | ---
Short description | Scaling for power feed-forward 1.
Mode | Regeneration
Minimum | 0.000 | Maximum | 4.000
Default | 1.000 | Units |
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 3
Coding | RW

See Power Input Mode (03.012).

Parameter | 03.016 Power Input 2 Scaling
--- | ---
Short description | Scaling for power feed-forward 2.
Mode | Regeneration
Minimum | 0.000 | Maximum | 4.000
Default | 1.000 | Units |
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 3
Coding | RW

See Power Input Mode (03.012).

Parameter | 03.017 Power Input 3 Scaling
--- | ---
Short description | Scaling for power feed-forward 3.
Mode | Regeneration
Minimum | 0.000 | Maximum | 4.000
Default | 1.000 | Units |
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 3
Coding | RW

See Power Input Mode (03.012).

Parameter | 03.018 Power Input kW
--- | ---
Short description | Power feed-forwards or set-point in kW.
Mode | Regeneration
Minimum | −VM_POWER | Maximum | VM_POWER
Default | 0.000 | Units | kW
Type | 32 Bit Volatile | Update Rate | 250µs read
Display Format | Standard | Decimal Places | 3
Coding | RW, VM, NC

See Power Input Mode (03.012). See Regen Sub-mode (01.003) for the polarity of this parameter.

Parameter | 03.019 Reactive Power Input Mode
--- | ---
Short description | Reactive power set-point select.
Mode | Regeneration
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

It is possible to control the reactive component of current from the a.c. terminals of the system. See Regen Sub-mode (01.003) for the polarity of the reactive current. Reactive component control can be used even if the d.c. bus voltage controller is active, because the voltage controller only affects the active current component. If Reactive Power Input Mode (03.019) = 0 the reactive current can be defined with Reactive Current Reference (04.008). If Reactive Power Input Mode (03.019) = 1 the reactive kVAR can be specified with Reactive Power Input kVAR (03.020). For the most accurate result when using measured voltages to derive Vd (05.086) and Vq (05.087), both the reactive and active current references should be derived from Reactive Power Input kVAR (03.020) and Power Input kW (03.018).

Parameter | 03.020 Reactive Power Input kVAR
--- | ---
Short description | Reactive power set-point in kVARs.
Mode | Regeneration
Minimum | −VM_POWER | Maximum | VM_POWER
Default | 0.000 | Units | kVAr
Type | 32 Bit User Save | Update Rate | 250µs read
Display Format | Standard | Decimal Places | 3
Coding | RW, VM, NC

See Reactive Power Input Mode (03.019). See Regen Sub-mode (01.003) for the polarity of this parameter.

Parameter | 03.021 Harmonic Reduction Enable
--- | ---
Short description | Enables harmonic reduction controllers to minimise phase imbalance and 5th and 7th current harmonics.
Mode | Regeneration
Minimum | 0 | Maximum | 2
Default | 1 | Units |
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | Disabled
1 | Imbalance Only
2 | All

Even with the optimum d.c. bus voltage and current controller set-up it is possible for supply voltage distortion to cause harmonic distortion in the a.c. currents between the supply and the converter. Additional control systems are provided to reduce phase imbalance, 5th harmonics and 7th harmonics in the a.c. currents. Harmonic Reduction Enable (03.021) defines the type of distortion reduction required. It should be noted that the filter components between the converter and the supply absorb 5th and 7th harmonic currents if there is 5th or 7th harmonic supply voltage distortion. The reduction system cannot reduce this current, but can minimise the 5th and 7th harmonic current due to 5th and 7th harmonic voltage distortion between the supply and the converter.

Harmonic Reduction Enable (03.021) | Distortion reduced
0 (Disabled) | None
1 (Imbalance Only) | Due to voltage imbalance
2 (All) | Due to voltage imbalance, 5th and 7th harmonics

Each of the additional controllers used to minimise currents due to imbalance, 5th and 7th harmonic distortion have an integral controller similar to the controller for normal supply frequency currents. The gains for the 5th and 7th harmonic current control are at a fixed low level, however, the gain for minimisation of currents due to imbalance can be adjusted by the user with Negative Phase Sequence Current Gain (03.039). The default value is low, and so the response due to a change in supply imbalance is relatively slow. For most applications the gain can be left at the default level, but where a fast response is required, i.e. continued operation in the presence of an asymmetrical fault, the level should be increased. Negative Phase Sequence Current Gain (03.039) defines the gain used for control of currents due to imbalance as a proportion of Current Controller Ki Gain (04.014). Care should be taken when increasing this value as the system stability may be reduced particularly with a weak supply.

The following should be noted when using the harmonic reduction system:

1. The positive and negative phase sequence components Negative Phase Sequence Volts (03.038) and Positive Phase Sequence Volts (03.037) are derived from the harmonic reduction system if Supply Voltage Detection Mode (03.029) has a value of 0 (Measured dc) or 2 (User). If this is the case, then Harmonic Reduction Enable (03.021) must be set to a value of 1 (Imbalance Only) or 2 (All) for the phase sequence components to be measured and phase imbalance to be detected.
2. If Supply Voltage Detection Mode (03.029) has a value of 3 (Measured a.c.) the positive and negative phase sequence components are derived from the measured voltage at the point of common connection, and so the imbalance reduction system does not need to be enabled.
3. The harmonic reduction system applies a harmonic voltage at the regen system terminals to try and redcuce harmonic currents and imbalance. Care should be taken when attempting to remove 5th, and particularly 7th harmonic, distortion to ensure that the output does not saturate. Generally 5th and 7th harmonic voltages on the supply are usually small and do not require a large voltage to cancel their effect. However, if the headroom between the maximum possible regen system output voltage and the peak supply voltage is small it is advisable not to set Harmonic Reduction Enable (03.021) to 2 (All) to try and remove 5th and 7th harmonic current distortion.

Parameter | 03.022 D.c. Voltage Ramp Time
--- | ---
Short description | Rate at which the system increases the d.c. bus voltage when the voltage controller is enabled after the drive has synchronised to the supply
Mode | Regeneration
Minimum | 0.1 | Maximum | 100.0
Default | 1.0 | Units | V/ms
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 1
Coding | RW

If grid-connected mode is active and d.c. link control is active (Power Input Mode (03.012) < 2), then when the system is enabled and has synchronised to the supply, the d.c. bus voltage is at a level equal to the peak line to line voltage. The voltage controller is then enabled and attempts to raise the d.c. bus voltage to the set-point defined by D.c. Voltage Set Point (03.005) . The voltage reference is ramped up to the required level at a rate defined by D.c. Voltage Ramp Time (03.022) in V/ms. The default value of 1.0V/ms ensures limited over-shoot when the d.c. bus voltage reaches the required level. If a shorter synchronisation time is required then the ramp rate can be increased, however care must be taken to avoid over-voltage trips particularly if a high level is used for the d.c. bus voltage set-point. If a faster ramp rate and high set-point are required it may be necessary to increase D.c. Voltage Controller Proportional Gain Kp (03.006) to minimise over-shoot. If Power Input Mode (03.012) = 2 (kW), the d.c. link voltage control is not used, and so the power and VARs controllers become active immediately after the system becoes synchronised.

Parameter | 03.023 Supply Loss Threshold
--- | ---
Short description | Level below which the system detects a.c. supply loss.
Mode | Regeneration
Minimum | −VM_AC_VOLTAGE_SET | Maximum | VM_AC_VOLTAGE_SET
Default | See exceptions below | Units | V
Type | 16 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, VM, RA

Voltage | Default Value
200V | 75
400V | 150

If the supply voltage feedback selected with Supply Voltage Detection Mode (03.029) falls below Supply Loss Threshold (03.023) x 0.95 then supply loss is detected and Supply Loss (10.015) is set to one. The supply voltage must rise above Supply Loss Threshold (03.023) x 1.05 to remove the supply loss condition and for Supply Loss (10.015) to be reset to zero. The supply loss indication remains active for at least 100ms.

Parameter | 03.024 Minimum Supply Frequency
--- | ---
Short description | Frequency range detector minimum limit.
Mode | Regeneration
Minimum | 10 | Maximum | 195
Default | 40 | Units | Hz
Type | 8 Bit User Save | Update Rate | 2ms read
Display Format | Standard | Decimal Places | 0
Coding | RW, BU

The frequency limits are only applied in grid-connected mode. Frequency limits defined by Minimum Supply Frequency (03.024) and Maximum Supply Frequency (03.025) are applied to the frequency at the converter terminals. A margin of more than 5Hz should be allowed outside the likely supply frequency range to enable the system to operate. If the supply frequency is within approximately 5Hz of either limit for 500ms the system will not remain synchronised and attempts to re-synchronise. While the supply frequency remains within approximately 5Hz of either limit the system will not be able to synchronise successfully. The frequency limits are important if the supply is removed when the system is active, as the system could remain active, particularly if energy is fed into the d.c. bus, with an uncontrolled output frequency and voltage. If Minimum Supply Frequency (03.024) > Maximum Supply Frequency (03.025) - 5Hz, then the minimum is Maximum Supply Frequency (03.025) - 5Hz.

These limits are also used by the grid voltage measurement system when phase-loss occurs to prevent the measured frequency from becoming zero once the voltage phasor stops rotating due to the missing phase.This system functions correctly if the limits are set to cover the likely supply frequency range with a reasonable margin. The default settings are suitable for 50Hz or 60Hz supplies.

Parameter | 03.025 Maximum Supply Frequency
--- | ---
Short description | Frequency range detector maximum limit.
Mode | Regeneration
Minimum | 15 | Maximum | 200
Default | 70 | Units | Hz
Type | 8 Bit User Save | Update Rate | 2ms read
Display Format | Standard | Decimal Places | 0
Coding | RW, BU

See Minimum Supply Frequency (03.024).

Parameter | 03.026 Minimum Supply Voltage
--- | ---
Short description | Voltage range detector minimum voltage limit.
Mode | Regeneration
Minimum | −VM_AC_VOLTAGE | Maximum | VM_AC_VOLTAGE
Default | 0 | Units | V
Type | 16 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 0
Coding | RW, VM, RA

Supply voltage range detection is provided. If Maximum Supply Voltage (03.027) is set to its default of zero, then additional supply voltage checking is disabled. If Maximum Supply Voltage (03.027) is set to a non-zero value and the voltage is outside the range defined by Maximum Supply Voltage (03.027) and Minimum Supply Voltage (03.026) for more than 100ms a Voltage Range trip is initiated with sub-trip 1 for a voltage below the minimum threshold or sub-trip 2 for voltage above the maximum threshold. If Maximum Supply Voltage (03.027) ≤ Minimum Supply Voltage (03.026) then the trip is initiated repeatedly. If Supply Voltage Detection Mode (03.029) is set to 0 or 1 the converter output voltage is monitored but only when the system is synchronised. If Supply Voltage Detection Mode (03.029) is set to 2 the measured grid voltage is monitored whether the system is synchronised or not.

Parameter | 03.027 Maximum Supply Voltage
--- | ---
Short description | Voltage range detector maximum voltage limit.
Mode | Regeneration
Minimum | −VM_AC_VOLTAGE | Maximum | VM_AC_VOLTAGE
Default | 0 | Units | V
Type | 16 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 0
Coding | RW, VM, RA

See Minimum Supply Voltage (03.026).

Parameter | 03.028 Supply Voltage
--- | ---
Short description | Supply voltage level that can by used in the supply loss detector.
Mode | Regeneration
Minimum | −VM_AC_VOLTAGE_SET | Maximum | VM_AC_VOLTAGE_SET
Default | See exceptions below | Units | V
Type | 16 Bit User Save | Update Rate | 4ms read
Display Format | Standard | Decimal Places | 0
Coding | RW, VM, RA

Voltage | Region | Default Value
200V | All | 230
400V | 50Hz | 400
400V | 60Hz | 460

See Supply Voltage Detection Mode (03.029).

Parameter | 03.029 Supply Voltage Detection Mode
--- | ---
Short description | Method used to measure the supply voltage to detect supply loss and phase loss.
Mode | Regeneration
Minimum | 0 | Maximum | 3
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE, BU

Value | Text
0 | Measured dc
1 | User
2 | Measured dc
3 | Measured ac

This parameter defines the method used to measure the supply voltage to detect supply loss, phase imbalance and phase loss.

Measured d.c. (0):
When the system is not synchronised Estimated Supply Voltage (03.036) is used as the supply voltage to detect supply loss and is calculated from the d.c. bus voltage assuming that this is the rectified supply voltage. Attempting to synchronise to the supply or being synchronised causes the d.c. bus voltage to rise above the rectified level of the supply, and so when the system is not synchronised Estimated Supply Voltage (03.036) is only updated when the d.c. bus voltage has stopped rising or falling. When the system synchronises Estimated Supply Voltage (03.036) is left at the value derived before synchronisation and will only be modified again when the system is not synchronised and the d.c. bus voltage is stable. When the system is synchronised the output of the inverter (Output Voltage (05.002)) is used to detect supply loss. Phase imbalance is detected from the phase imbalance reduction system, and so Harmonic Reduction Enable (03.021) ≥ 1 is required to enable this. Phase loss is not actively detected but if the converter is active with some load the system becomes unsynchronised and will be unable to re-synchronise until the missing phase is reconnected.

User (1):
When the system is not synchronised Estimated Supply Voltage (03.036) is used as the supply voltage to detect supply loss and this is derived directly from Supply Voltage (03.028). When the system is synchronised the output of the inverter (Output Voltage (05.002)) is used to detect supply loss. Phase loss and phase imbalance detection operate as described for "Measured d.c."" above.

Measured d.c. (2):
As Measured d.c. (0). Provided for legacy reasons so that if the parameters from older drives which had a default of 2 for this parameter are loaded they select measured d.c. mode.
Measured a.c. (3):
Supply loss, phase loss and phase imbalance are detected from the measured grid voltages. Phase loss is detected when the three supply phase voltages form a pulsating phasor which does not rotate (i.e. the supply frequency is zero). If the r.m.s. level of all three measured line voltages is above half of Supply Loss Threshold (03.023) and the supply frequency is less than Minimum Supply Frequency (03.024) the phase loss indication becomes active. This only functions correctly if the converter is disabled because the converter creates the missing phase voltage when active. When the converter is active with some load the system becomes unsynchronised and will be unable to re-synchronise until the missing phase is reconnected.

Whatever the setting of this parameter Estimated Supply Voltage (03.036) is used to pre-set the current controllers during synchronisation and resynchronisation after a supply fault in grid-connected and grid-supporting modes. Therefore the source selected with Supply Voltage Detection Mode (03.029) should give a reasonable estimate of the supply voltage. If the d.c. link voltage is defined other than through a rectifier connected to the supply and the d.c. link level differs substantially from the rectified supply voltage Supply Voltage Detection Mode (03.029) should not be set to zero during synchronisation in grid-connected or grid-supporting modes. If measured grid voltages are not available Supply Voltage (03.028) should be used and set or controlled to a value close to the actual supply voltage.

Parameter | 03.030 Island Detection Enable
--- | ---
Short description | Enables island detection.
Mode | Regeneration
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 1 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW

If Island Detection Enable (03.030) is set to one, then the detection system is enabled and injects a reactive test current with a frequency defined by Island Detection Injection Frequency (03.031). The measurement period is: one cycle for an injection frequency of 1Hz, three cycles for 2Hz and seven cycles for 4Hz. There is up to one cycle before a complete cycle is measured after an island condition becomes active, and so the detection period is always less than or equal to 2s. The Island Detection Level (03.032) shows the detection level with respect to a threshold of 2.5rad/s (03.98Hz), and if this reaches 100% Island Detected (10.083) becomes active and remains active for 1s. The island detection system complies with IEEE 1547 and VDE-AR-N-4105 in that it should detect an island within 2s.

Island detection is intended to prevent the system from self exciting a disconnected section of the grid which contains components that can resonant at a frequency close to the supply frequency. Island detection can be tested with an RLC circuit. An island is detected by the deviation of the frequency of the islanded supply. The peak deviation of the frequency is approximately Δω = (5% x Rated Current (05.007) / (Supply Line Voltage / √3)) / (2C), where C is the capacitance. For example Vsupply = 400V, IRated = 17.2A, C = 216uF, Δω = (0.05 x 17.2) / (400 / √3) / (2 x 216 x 10-6) = 8.62rad/s (1.37Hz).

Parameter | 03.031 Island Detection Injection Frequency
--- | ---
Short description | Frequency of the test current used for island detection
Mode | Regeneration
Minimum | 0 | Maximum | 2
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | 1Hz
1 | 2Hz
2 | 4Hz

See Island Detection Enable (03.030).

Parameter | 03.032 Island Detection Level
--- | ---
Short description | Percentage island detection level with respect to the threshold.
Mode | Regeneration
Minimum | 0 | Maximum | 1000
Default |  | Units | %
Type | 16 Bit Volatile | Update Rate | Background write
Display Format | Standard | Decimal Places | 0
Coding | RO, ND, NC, PT

See Island Detection Enable (03.030).

Parameter | 03.033 Island Detection Synchronisation Source Select
--- | ---
Short description | Clock source selected to derive the island detection test frequency.
Mode | Regeneration
Minimum | 0 | Maximum | 4
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | Converter
1 | Slot 1
2 | Slot 2
3 | Slot 3
4 | Slot 4

If Island Detection Synchronisation Source Select (03.033) is set to its default value of zero (Converter) then the frequency of the current injected to detect an island condition is defined by the converter control system. If Island Detection Synchronisation Source Select (03.033) is set to a non-zero value to select an option module, and the option module provides a suitable clock, then the injected current is synchronised to that clock. This allows the injected current from a number of systems to be synchronised to a master clock. If the option module does not provide a suitable clock, then the frequency is defined by the converter control system. The source being used is given in Island Detect Synchronisation Source (03.034).

Parameter | 03.034 Island Detect Synchronisation Source
--- | ---
Short description | Clock source actually being used to derive the island detection test frequency.
Mode | Regeneration
Minimum | 0 | Maximum | 4
Default |  | Units |
Type | 8 Bit Volatile | Update Rate | Background Write
Display Format | Standard | Decimal Places | 0
Coding | RO, TE, ND, NC, PT

Value | Text
0 | Converter
1 | Slot 1
2 | Slot 2
3 | Slot 3
4 | Slot 4

See Island Detection Synchronisation Source Select (03.033).

Parameter | 03.035 Synchronisation Headroom
--- | ---
Short description | d.c. bus voltage headroom used to prevent over-voltage trips during synchronisation.
Mode | Regeneration
Minimum | 0.0 | Maximum | 25.0
Default | 5.0 | Units | %
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 1
Coding | RW, BU

Each time a synchronisation attempt is made using test pulses the d.c. bus voltage is increased because of current that is built up in the inductors connected between the supply and the converter. As the current decays energy is transferred from the supply and the inductors to the d.c. bus capacitors. To prevent an over-voltage trip during synchronisation or re-synchronisation the system prevents this process from starting if the d.c. bus voltage is above the level defined by Maximum d.c. bus voltage x (100% - Synchronisation Headroom (03.035)). For example the full scale d.c. bus voltage for a 400V drive is 830V, so with the default setting of 5% the d.c. bus voltage must be less than 830V x 95% = 788.5V before the synchronisation process will begin. If the recommended components are connected between the supply and the converter the rise in the d.c. bus voltage during synchronisation requires less than 5% headroom. If alternative inductors are used that are significantly larger than the recommended values or the supply inductance is very high it may be necessary to increase the headroom.

Parameter | 03.036 Estimated Supply Voltage
--- | ---
Short description | Supply voltage that is derived when the system is not synchronised to derive the supply loss indication.
Mode | Regeneration
Minimum | −VM_AC_VOLTAGE | Maximum | VM_AC_VOLTAGE
Default |  | Units | V
Type | 16 Bit Volatile | Update Rate | 2ms Write (During Synchronisation)
Display Format | Standard | Decimal Places | 0
Coding | RO, FI, VM, ND, NC, PT

See Supply Loss Threshold (03.023).

Parameter | 03.037 Positive Phase Sequence Volts
--- | ---
Short description | Positive Phase Sequence Volts.
Mode | Regeneration
Minimum | −VM_AC_VOLTAGE | Maximum | VM_AC_VOLTAGE
Default |  | Units | V
Type | 16 Bit Volatile | Update Rate | 1ms Write
Display Format | Standard | Decimal Places | 0
Coding | RO, FI, VM, ND, NC, PT

The supply voltage at its fundamental frequency can be represented as a combination of positive, negative and zero sequence components. The supply voltage cannot contain any zero sequence components because there is no neutral connection. The negative phase sequence component is an indication of the level of supply imbalance. Positive Phase Sequence Volts (03.037) and Negative Phase Sequence Volts (03.038) show the positive and negative phase sequence components of voltage at the inverter terminals in r.m.s. line to line Volts. Note that Negative Phase Sequence Volts (03.038) is zero unless Harmonic Reduction Enable (03.021) > 0 (i.e., imbalance reduction is active).

Parameter | 03.038 Negative Phase Sequence Volts
--- | ---
Short description | Negative Phase Sequence Volts.
Mode | Regeneration
Minimum | −VM_AC_VOLTAGE | Maximum | VM_AC_VOLTAGE
Default |  | Units | V
Type | 16 Bit Volatile | Update Rate | 1ms Write
Display Format | Standard | Decimal Places | 0
Coding | RO, FI, VM, ND, NC, PT

See Positive Phase Sequence Volts (03.037).

Parameter | 03.039 Negative Phase Sequence Current Gain
--- | ---
Short description | Gain used by the imbalance reduction system.
Mode | Regeneration
Minimum | 0.00 | Maximum | 1.00
Default | 0.05 | Units |
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 2
Coding | RW

See Harmonic Reduction Enable (03.021).

Parameter | 03.040 Phase Imbalance Threshold
--- | ---
Short description | Defines the level of imbalance required for imbalance detected to become active.
Mode | Regeneration
Minimum | 0.0 | Maximum | 50.0
Default | 5.0 | Units | %
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 1
Coding | RW

Phase Imbalance (10.082) becomes active if Negative Phase Sequence Volts (03.038) / Positive Phase Sequence Volts (03.037) is greater than Phase Imbalance Threshold (03.040). Phase Imbalance (10.082) becomes inactive again when this value falls below Phase Imbalance (10.082) x 0.95. The supply imbalance indication remains active for at least 100ms.

Parameter | 03.041 Supply Loss Voltage
--- | ---
Short description | Final voltage used as the input to the supply loss detector.
Mode | Regeneration
Minimum | −VM_AC_VOLTAGE | Maximum | VM_AC_VOLTAGE
Default |  | Units | V
Type | 16 Bit Volatile | Update Rate | 2ms Write
Display Format | Standard | Decimal Places | 0
Coding | RO, FI, VM, ND, NC, PT

This parameter shows the supply voltage level at the input to the supply loss detector.