# Menu 1 − Grid Control

Mode: Regeneration

In addition to providing an active 4-quadrant front end (AFE) for a drive supplying a motor connected to the d.c. terminals of the converter, regeneration mode can also be used for other d.c. to a.c. conversion applications where a power source (i.e., batteries, solar panels, etc.) is connected to the d.c. terminals. To support this, the system can operate in different grid modes selected by Grid Mode (01.010). When operating as an AFE the polarity of the power and reactive power relate to a load connected to the supply, but when operating as an d.c. to a.c. converter it is more convenient for the polarity of the power and reactive power to relate to a generator. Regen Sub-mode (01.003) can be used to select AFE or generator mode to adjust the polarity of the power and reactive power to suit different applications. The measured power and reactive power are calculated as shown below where Vd (05.086) and Vq (05.087) are derived from the location of the voltage feedback selected with Voltage Feedback Select (05.085), and Id (05.104) and Iq (05.105) are derived from the location of the current feedback selected with Current Feedback Select (05.103).

Grid-connected mode is used where the converter has a much smaller power rating than the entire power system to which it is connected. The frequency and a.c. voltage are defined by the power system. This mode is always used when the system is operating as an AFE. The control system is shown below for comparison with the other modes. Voltage feedback from the power system is not required because a sensorless method is used to synchronise to the power system voltages.

The system can be used to provide a grid in grid-forming mode where it defines the frequency and voltage as shown below. The d.c. bus voltage must be controlled by an external power source, for example batteries or solar panels. By default Converter Output As Feedback (01.038) = 1, and so the voltage at the output of the converter is used as feedback. This is always required if changing from grid-connected mode to this mode to form a local grid because the voltages measured from the grid are disconnected when Connect grid (01.018) is set to zero to disconnect the grid. The measured grid voltage can be used as voltage feedback if the feedback remains connected to the converter output. Compensation can be provided for the voltage drop in a transformer connected to the output of the system so that the voltage at its output is defined.

The system can be used to simulate an electro-mechanical generator in grid-supporting mode where the voltage and frequency are defined but with droop functions. Again, the d.c. bus voltage must be controlled by a power source. The defined frequency with droop controls the power flow and ensures correct power sharing with other sources on the power system. The defined voltage with droop controls the transfer of reactive power (VARs) and ensures correct sharing of reactive power with other sources on the power system. As with grid-forming mode the converter output voltage or measured grid-voltage can be used as feedback..

If grid-connected mode is active the fault detection system detects supply faults and can take appropriate action. The system can either trip, or try to ride through the fault and then after a defined time it is possible to change seamlessly into grid-forming or grid-supporting mode. When the change is made the local grid can be disconnected from the main grid and then the main grid can be monitored. If the fault is removed the system can resynchronise itself and then reconnect to the main grid.

Parameter | 01.001 Grid Power (P)
--- | ---
Short description | Power at point of selected voltage and current feedback.
Mode | Regeneration
Minimum | −VM_POWER | Maximum | VM_POWER
Default |  | Units | kW
Type | 32 Bit Volatile | Update Rate | 4ms Write
Display Format | Standard | Decimal Places | 3
Coding | RO, FI, VM, ND, NC, PT

Vd (05.086) and Vq (05.087) at the point defined by Voltage Feedback Select (05.085) are used in conjuction with Id (05.104) and Iq (05.105) at the point defined by Current Feedback Select (05.103) to give the power (Grid Power (P) (01.001)) and VARs (Grid VARs (Q) (01.002)) at the fundamental frequency at this point. The purpose of these parameters is to show the power and VARs at the point of common connection with the grid.

In grid-connected mode the converter can produce reactive current to cancel the current that would be taken by the filter capacitors from the grid (A.c. Filter Capacitance (05.025) is non-zero). If Id (05.104) is measured at the converter terminals, the cancellation current is subtracted from the measured reactive current as this should simply flow in the loop from the converter to the filter and not in the grid connection. The other grid modes inherently produce this current, and so it is also subtracted when these modes are active. If the reactive current is derived from external current measurement at the point of common connection with the grid, then this is not necessary.

In grid-connected mode when using a power and VARs reference No-load Power Offset (05.026) is added to the power reference to account for an offset in the measured active current due to regen inductor losses etc.. If Iq (05.105) is measured at the converter terminals, then the power offset is subtracted from the measured grid power as this additional power does not flow between the converter and the grid. If the d.c. link is being controlled in grid-connected mode or one of the other grid modes is active with the grid this apparent grid power is inherent, and so it is removed from the measured grid power with these configurations as well. If the active current is derived from external current measurement at the point of common connection with the grid, then this is not necessary.

See Regen Sub-mode (01.003) for the polarity of these parameters.

Parameter | 01.002 Grid VARs (Q)
--- | ---
Short description | VARs at the point of selected voltage and current feedback.
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

See Grid Power (P) (01.001).

Parameter | 01.003 Regen Sub-mode
--- | ---
Short description | Current, power and reactive power polarity can be defined to look like an AFE or as a generator.
Mode | Regeneration
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | AFE
1 | Generator

This parameter defines the convention used for the direction of current, power and reactive power. The current components at the fundamental frequency are assumed to be same at the converter terminals and the point of common connection (on the grid side of the switching frequency filter inductor) when compensation is provided for the filter capacitor current and switching frequency related power offset. The voltage components at the measurement point defined by Voltage Feedback Select (05.085) are Vd (05.086) and Vq (05.087). These are slightly different at each measuring point. The power and reactive power at the converter terminals or the point of common connection are given by the following equations.

Grid Power (P) (01.001) = Vd (05.086) x Reactive Current (04.017) + Vq (05.087) x Active Current (04.002)

Grid VARs (Q) (01.002) = Vq (05.087) x Reactive Current (04.017) - Vd (05.086) x Active Current (04.002)

where Vd (05.086) and Vq (05.087) are the d and q-axis components of the measured or estimated voltage in a reference frame defined by the converter as shown below.

Reactive Power (03.001) and Output Power (05.003) are calculated in the same way but always use the voltage at the converter terminals.

AFE
This is the default setting and makes the system look like a load attached to the grid, and so positive current flows out of the grid and INTO the converter which has the following effects.

When Active Current (04.002) is positive, Grid Power (P) (01.001) is positive and the converter consumes power.
When Active Current (04.002) is negative, Grid Power (P) (01.001) is negative and the converter delivers power.

When Reactive Current (04.017) is positive, Grid VARs (Q) (01.002) is positive and the converter consumes reactive power. The converter looks like an inductive load and the current lags the voltage.
When Reactive Current (04.017) is negative, Grid VARs (Q) (01.002) is negative and the converter delivers reactive power. The converter looks like a capacitive load and the current leads the voltage.

Positive references in Power Input 1 (03.010) to Power Input 3 (03.014), Power Input kW (03.018) or Active Current Reference (04.009) will result in a demand for power to be consumed by the converter.
Negative references in Power Input 1 (03.010) to Power Input 3 (03.014), Power Input kW (03.018) or Power Input kW (03.018) will result in a demand for power to be delivered by the converter.

Positive references in Reactive Current Reference (04.008) or Reactive Power Input kVAR will result in a demand for the converter to consume reactive power making the converter look like an inductive load.
Negative references in Reactive Current Reference (04.008) or Reactive Power Input kVAR will result in a demand for the converter to deliver reactive power making the converter look like a capacitive load.

Generator
This is the setting and makes the system look like a generator, and so positive current flows OUT of the converter and into the grid.

When Active Current (04.002) is positive, Grid Power (P) (01.001) is positive and the converter delivers power.
When Active Current (04.002) is negative, Grid Power (P) (01.001) is negative and the converter consumes power.

When Reactive Current (04.017) is positive, Grid VARs (Q) (01.002) is positive and the converter delivers reactive power. The converter can supply reactive power to an inductive load connected to the supply and is like an over-excited generator.
When Reactive Current (04.017) is negative, Grid VARs (Q) (01.002) is negative and the converter consumes reactive power. The converter can supply reactive power to a capacitive load connected to the supply and is like and under-excited generator.

Positive references in Power Input 1 (03.010) to Power Input 3 (03.014), Power Input kW (03.018) or Active Current Reference (04.009) will result in a demand for power to be delivered by the converter.
Negative references in Power Input 1 (03.010) to Power Input 3 (03.014), Power Input kW (03.018) or Power Input kW (03.018) will result in a demand for power to be consumed by the converter.

Positive references in Reactive Current Reference (04.008) or Reactive Power Input kVAR will result in a demand for the converter to deliver reactive power.
Negative references in Reactive Current Reference (04.008) or Reactive Power Input kVAR will result in a demand for the converter to consume reactive power.

Parameter | 01.004 Grid Power/VARs Filter Disable
--- | ---
Short description | Disables the filter applied to the grid power and VARs.
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

By default a 128ms filter is applied to the values given in Grid Power (P) (01.001) and Grid VARs (Q) (01.002) to give more stable values. To disable the filters this parameter should be set to zero.

Parameter | 01.010 Grid Mode
--- | ---
Short description | Currently active grid mode.
Mode | Regeneration
Minimum | 0 | Maximum | 2
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | 4ms Read/Write
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text | Description
0 | Grid Connected | The grid defines the frequency and voltage.
1 | Grid Forming | Creates a local grid by defining the grid voltage and frequency.
2 | Grid Supporting | Connects to a grid and shares power and VARs based on the settings for frequency and voltage droop respectively.

The following grid-modes can be selected:

Grid Mode (01.010) | Function
Grid-connected | Default mode used to provide an active front-end for a 4-quadrant drive or a d.c. to a.c. converter to connect a power source (i.e., batteries or solar panels, etc.) to a larger grid. The a.c. voltage and frequency are defined by the grid.
Grid-forming | Forms a local grid and defines the grid frequency and voltage. The d.c. bus voltage must be controlled by an external power source. The load can include imbalance but the converter will attempt to maintain balanced voltages, however as the level of load imbalance is increased the converter output voltages will include some imbalance.
Grid-supporting | Supports the grid and looks like a generator. The a.c. frequency and voltage are defined but include droop to regulate power and VARs sharing with other systems connected to the grid. The d.c. bus voltage must be controlled by an external power source. The load can include imbalance but the converter will attempt to maintain balanced voltages, however as the level of load imbalance is increased the converter output voltages will include some imbalance.

The following actions are taken when the system is enabled in each mode. See Regen Synchronisation Mode (03.004) for more details.

Grid Mode (01.010) | Actions on enable
Grid-connected | A synchronisation test is carried out. If Power Input Mode (03.012) < 2 and Active Current Reference Selector (04.010) = 0 the d.c. bus voltage is ramped to the set-point. The system operates with the required set-points.
Grid-forming | No synchronisation is required and the system starts to operate with the required set-points.
Grid-supporting | Synchronisation is carried out as defined for Start Mode (01.050). The system operates with the required set-points.

The system can automatically switch from grid-connected mode to grid-forming or grid-supporting mode when a fault is detected and then switch back when the fault is removed. The automatic changeover is implemented by the system writing to this parameter. See Action On Fault (01.015) and Action on Fault Recovery (01.016) for more details. When manual switching between modes is required, this parameter can be written directly. See Grid-mode Changeover State (01.020) for details of the changeover process.

Parameter | 01.011 Action On Phase Loss
--- | ---
Short description | Defines the action when a phase loss is detected.
Mode | Regeneration
Minimum | 0 | Maximum | 2
Default | 2 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | No Action
1 | Fault Detect
2 | Trip

This parameter is used to connect the phase loss indication (Phase Loss (10.081)) to the fault detection system. If this parameter is set to 2 (Trip) the system initiates a Phase Loss trip immediately if phase loss is detected. See Phase Loss (10.081) for more details on phase loss detection.

Parameter | 01.012 Action On Phase Imbalance
--- | ---
Short description | Defines the action when a phase imbalance is detected.
Mode | Regeneration
Minimum | 0 | Maximum | 2
Default | 2 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | No Action
1 | Fault Detect
2 | Trip

This parameter is used to connect the phase imbalance detection (Phase Imbalance (10.082)) to the fault detection system. If this parameter is set to 2 (Trip) the system initiates a Phase Imbalance trip immediately if phase imbalance is detected. (If the system is operating in grid-connected or grid-supporting mode and this parameter is set to "No Action" the system will become unsynchronised when this fault is detected. It will then repeatedly try to synchronise until the fault is removed.)

Parameter | 01.013 Action On Island Detected
--- | ---
Short description | Defines the action when an island is detected.
Mode | Regeneration
Minimum | 0 | Maximum | 2
Default | 2 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | No Action
1 | Fault Detect
2 | Trip

This parameter is used to connect the island detection (Island Detected (10.083)) to the fault detection system. If this parameter is set to 2 (Trip) the system initiates an Island.001 trip immediately if an island is detected.

An island can only be detected in grid-connected mode. When an island condition is detected Island Detected (10.083) remains set for 1s and if this parameter is set to "Fault Detect" the bit in Faults Active (01.014) remains set for 1s even if the grid mode changes from grid connected mode. Once the new mode is active the grid should be monitored on the grid side of the contactor controlled by Connect grid (01.018) (which will be open). While the supply is not present, which initially caused the island to form, supply loss is detected. This prevents fault recovery from occurring until the supply recovers.

Parameter | 01.014 Faults Active
--- | ---
Short description | Indicate which grid faults are active.
Mode | Regeneration
Minimum | 0 (Display: 0000) | Maximum | 15 (Display: 1111)
Default |  | Units |
Type | 8 Bit Volatile | Update Rate | 2ms write
Display Format | Binary | Decimal Places | 0
Coding | RO, ND, NC, PT

This parameter indicates which grid faults are active as follows:

Bit | Fault
0 | Supply loss
1 | Phase loss
2 | Phase imbalance
3 | Island detected

Supply loss is based on the magnitude of the phasor representing the supply voltage. As the supply imbalance increases, or a phase is lost, the variation in the phasor magnitude increases as it rotates through each cycle. The supply loss detector remains active for 100ms after supply loss is detected, and so high levels of imbalance or phase loss can cause the supply loss detector to be active. Unless Supply Loss Threshold (03.023) is set to a relatively low level it is likely the supply loss flag will be set if phase loss or a high level of phase imbalance occurs.

Parameter | 01.015 Action On Fault
--- | ---
Short description | Defines the action taken when a grid fault is detected.
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 | Description
0 | Trip | Trip
1 | Grid Forming | Change to grid-forming mode
2 | Grid Supporting | Change to grid-supporting mode

If Grid Mode (01.010) is set to a value other than Grid-connected Mode (0) or Regen Synchronisation Mode (03.004) is set to any value other than Auto-synchronise (3), the fault action system is disabled and Connect grid (01.018) is held at one.

If Regen Synchronisation Mode (03.004) is set to Auto-synchronise (3) and the system is operating in grid-connected mode, then when a fault becomes active (Faults Active (01.014) is non-zero) the system will begin a ride-through sequence at the grid frequency that was present before the fault occurred. The active current is held at zero but it is possible to inject reactive current into the fault by setting a non-zero value in Reactive Current Reference (04.008). For more detail on this sequence see Regen Synchronisation Mode (03.004). The end of the ride-through sequence occurs after a timeout defined by Fault Ride-through Time (01.017), and the action taken at this point is given in the table below. If the fault is removed before the timeout, the ride-through sequence is terminated and the system continues to operate normally in grid-connected mode. Note that Fault Ride-through Time (01.017) should be set to zero if the required action is to occur immediately a fault is detected. If an over-current trip occurs as a result of the fault, it is reset before the grid mode change begins even if Fault Ride-through Time (01.017) = 0. (Note that if Action On Phase Loss (01.011) = 1 and Phase Loss (10.081) becomes 1, or Action On Island Detected (01.013) = 1 and Island Detected (10.083) becomes 1 the ride-through sequence is terminated immediately and the action defined by Action On Fault (01.015) is taken immediately whatever the value of Fault Ride-through Time (01.017).)

Action On Fault (01.015) | Action at the end of the ride-through sequence
Trip | Supply Loss (10.015) = 1 gives an Island.002 trip Phase Loss (10.081) = 1 gives a Phase Loss trip Phase Imbalance (10.082) gives a Phase Imbalance trip Island Detected (10.083) gives an Island.001 trip
Grid-forming | The system switches to grid-forming mode with a one-shot write to Grid Mode (01.010).
Grid-supporting | The system switches to grid-supporting mode with a one-shot write to Grid Mode (01.010).

Connect grid (01.018) is controlled as given in the description of Grid-mode Changeover State (01.020) to operate a contactor to connect the system to the main grid. The contactor is opened after a fault on the main grid is detected to form a local grid. The contactor is then closed again when the fault is removed if required to reconnect to the main grid.

Parameter | 01.016 Action on Fault Recovery
--- | ---
Short description | Action required when the fault is removed.
Mode | Regeneration
Minimum | 0 | Maximum | 1
Default | 0 | Units |
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW, TE

Value | Text
0 | Disabled
1 | Recover

If Grid Mode (01.010) is not set to Grid-Forming Mode (1) or Grid-Supporting Mode (2), Regen Synchronisation Mode (03.004) is set to any value other than Auto-synchronise (3), or Action on Fault Recovery (01.016) = 0 (Disabled), then the fault recovery system is disabled.

Fault recovery is intended to reconnect a local grid which has been created because of a fault detected while operating in grid-connected mode. The local grid will have been disconnected from the main grid because Connect grid (01.018) will have changed to zero and opened the contactor between the main grid and the local grid. For fault recovery to operate correctly Supply Voltage Detection Mode (03.029) must be set to Measured a.c. (2) and the feedback must be taken from a point of common connection on the main grid side of the contactor so that the main grid can be monitored while the contactor is open. If Regen Synchronisation Mode (03.004) is set to Auto-synchronise (3), Action on Fault Recovery (01.016) = 1, Grid Mode (01.010) is set to grid-forming or grid-supporting modes, and Faults Active (01.014) changes from a non-zero value to zero and remains at zero for one second, Grid Mode (01.010) is set to grid connected mode and the process described for Grid-mode Changeover State (01.020) is followed to switch the system back to grid-connected mode.

Clearly, fault recovery only occurs if the measured a.c. voltage at the point of common connection (Measured Grid Voltage (05.082)) is high enough so that Supply Loss (10.015) is not active, and the supply imbalance is low enough so that Phase Imbalance (10.082) and Phase Loss (10.081) are not active (if either of these are fed into the fault detection system). The island detector is only active in grid-connected mode, so if an island is detected which causes the automatic changeover from grid-connected mode, then Island Detected (10.083) will become inactive. When the main grid supply recovers, the local grid will reconnect and operate as part of the main grid in grid-connected mode until another fault is detected.

Parameter | 01.017 Fault Ride-through Time
--- | ---
Short description | Timeout period to remain in ride-through mode after a fault is detected.
Mode | Regeneration
Minimum | 0.0 | Maximum | 5.0
Default | 0.0 | Units | s
Type | 8 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 1
Coding | RW

Defines the time that the system should remain in the ride-through state when supply loss or supply imbalance is detected. See Action On Fault (01.015) for more details.

Parameter | 01.018 Connect grid
--- | ---
Short description | Control for a contactor between the local system and the main grid.
Mode | Regeneration
Minimum | 0 | Maximum | 0
Default |  | Units |
Type | 1 Bit Volatile | Update Rate | 4ms Write
Display Format | Standard | Decimal Places | 0
Coding | RO, ND, NC, PT

This parameter can be routed via a digital output to control the contactor between a local grid to which the system is connected and the main grid.

Parameter | 01.019 Grid Contactor Operating Time
--- | ---
Short description | Maximum time for the grid connecting contactor to open or close.
Mode | Regeneration
Minimum | 0 | Maximum | 500
Default | 100 | Units | ms
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW

This parameter should be set to the maximum time for the grid connecting contactor to change from open to closed, or from closed to open.

Parameter | 01.020 Grid-mode Changeover State
--- | ---
Short description | Shows the state as the system changes mode.
Mode | Regeneration
Minimum | 0 | Maximum | 4
Default |  | Units |
Type | 8 Bit Volatile | Update Rate | 2ms Write
Display Format | Standard | Decimal Places | 0
Coding | RO, TE, ND, NC, PT

Value | Text | Description
0 | Connected | Grid-connected mode fully active.
1 | From Connected | Changing from grid-connected mode to either grid-forming or grid-supporting mode.
2 | Forming | Grid-forming mode is fully active.
3 | Supporting | Grid-supporting mode is fully active.
4 | To Connected | Changing from grid-forming or grid-supporting mode to grid-connected mode.

When the Grid Mode (01.010) is changed the sequence shown below is used to give a smooth transition between grid-connected mode and one of the other modes. Grid-mode Changeover State (01.020) shows the progress through the sequence. While grid-mode is active the final voltage and frequency references are aligned to the grid voltage and frequency, and then after the change to another mode the offset reset ramp rates are used to change the voltage and frequency references to the required levels. When changing back to grid-connected mode the offsets are used to align the final voltage and frequency references with the grid voltage and frequency, and then the phase of the converter output is aligned with the grid phase using a rate of change of phase of 60o per second until the phase difference is within 0.5o. A change between grid-forming and grid-supporting modes simply involves changing from providing compensation for a transformer at the output of the converter to providing voltage and frequency droop characteristics, or vice versa, and so the change is made without using the sequence shown below. If a change of grid-mode is made when the system is not synchronised the change is again made without using the sequence below but the system is switched back to the disable state, and so it must restart its synchronisation sequence.

Parameter | 01.030 A.c Voltage Set-point
--- | ---
Short description | A.c. voltage set-point for grid-forming and grid-supporting modes.
Mode | Regeneration
Minimum | 0 | Maximum | VM_AC_VOLTAGE_SET
Default | See exceptions below | Units | V
Type | 16 Bit User Save | Update Rate | 2ms Read
Display Format | Standard | Decimal Places | 0
Coding | RW, VM, RA

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

Grid-connected Mode:
This parameter has no effect.

Grid-forming Mode:
The active voltage controller controls the active current reference to give the the level of active voltage defined by this parameter in line to line r.m.s.volts at the required point in the system. The reactive voltage controller controls the reactive current reference to give zero volts at the required point in the system. The point in the system where the voltage is controlled is defined by the feedback point selected with Voltage Feedback Select (05.085) as given below.

Voltage Feedback Select (05.085) | Reason for selection
Converter output | The voltage drop in the regen inductor and switching frequency filter inductor are not important.
Measured Grid | Accurate control of the voltage at the point of common connection is required and voltage feedback is available. Compensation for the reactance drop in a transformer connected between the output of the switching frequency filter and the connection to a different voltage grid can also be compensated by including the equivalent inductance giving the transformer voltage drop referred to the side of the transformer to which to the converter is connected.

Grid-supporting Mode:
This simulates an electro-mechanical generator using a voltage droop characteristic.

To allow sufficient headroom for the converter to operate in grid-forming or grid-supporting mode the required converter output voltage should not be higher than (Vdcmin - 50V) / √2, where Vdcmin is the minimum expected d.c. bus voltage.

Parameter | 01.031 Transformer Inductance
--- | ---
Short description | Equivalent inductance of a transformer between the system output and the point where the voltage should be controlled.
Mode | Regeneration
Minimum | 0.000 | Maximum | 50.000
Default | 0.000 | Units | mH
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 3
Coding | RW, BU

Compensation for the reactance drop in a transformer connected between the output of the switching frequency filter and the connection to a different voltage grid can be provided in grid-forming mode. This parameter should be set to the equivalent inductance giving the transformer voltage drop referred to the side of the transformer to which to the converter is connected. This parameter has no effect in grid-connected or grid-supporting modes.

Parameter | 01.033 A.c. Voltage Controller Gain
--- | ---
Short description | Sets the gain of the a.c. voltage controllers.
Mode | Regeneration
Minimum | 0 | Maximum | 1000
Default | 100 | Units |
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 0
Coding | RW

This parameter defines the gain of the voltage controllers used to control the converter output voltage so that the q-axis voltage is equal to A.c Voltage Set-point (01.030) and the d-axis voltage is zero.

Parameter | 01.034 Voltage Droop
--- | ---
Short description | Simulated AVR voltage droop used in grid-support mode.
Mode | Regeneration
Minimum | 0.00 | Maximum | 50.00
Default | 5.00 | Units | %
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 2
Coding | RW

An AVR is simulated in grid-supporting mode with voltage droop defined as follows. The droop reduces the the set-point if Grid VARs (Q) (01.002) is positive or increases the set-point if Grid VARs (Q) (01.002) is negative.

a.c. Voltage Droop = [A.c Voltage Set-point (01.030) x Grid VARs (Q) (01.002) / (√3 x A.c Voltage Set-point (01.030) x Rated Current (05.007))] x Voltage Droop (01.034) / 100%

As this is intended to simulate a generator the polarity of the reactive power is always taken as though Regen Sub-mode (01.003) = 1 (Generator).

This parameter has no effect in grid-connected or grid-forming modes.

Parameter | 01.035 Voltage Offset
--- | ---
Short description | Offset applied to the voltage set-point.
Mode | Regeneration
Minimum | -1000 | Maximum | 1000
Default |  | Units | V
Type | 16 Bit Volatile | Update Rate | 2ms Read
Display Format | Standard | Decimal Places | 0
Coding | RO, ND, NC

This parameter is used to provide a smooth transition between grid modes. See Grid-mode Changeover State (01.020) for more detail.

Parameter | 01.036 Voltage Offset Reset Rate
--- | ---
Short description | Rate at which the voltage offset is reduced to zero.
Mode | Regeneration
Minimum | 0.00 | Maximum | 100.00
Default | 1.00 | Units | s/100V
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 2
Coding | RW

Voltage offset reset ramp rate specified in seconds per 100V.

Parameter | 01.037 Voltage Set-point Ramp Rate
--- | ---
Short description | Ramp rate applied to the voltage set-point.
Mode | Regeneration
Minimum | 0.00 | Maximum | 100.00
Default |  | Units | s/100V
Type | 16 Bit Volatile | Update Rate | Background Read
Display Format | Standard | Decimal Places | 2
Coding | RW, ND

Defines the ramp rate applied to the A.c Voltage Set-point (01.030) in seconds per 100V. The output of the ramp is always set to A.c Voltage Set-point (01.030) on enable because a separate ramp is provided on enable for grid-forming mode, or for a black start in grid-supporting mode (see Black Start Voltage Ramp Rate (01.051)). If this parameter is set to zero the ramp is disabled.

Parameter | 01.038 Converter Output As Feedback
--- | ---
Short description | Forces the system to use the converter output as voltage feedback
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 this parameter has its default value of one the converter output is used to provide the voltage feedback in grid-forming and grid-supporting modes. If better accuracy at the point of common connection is required, then Measured Grid Voltage (05.082) can be selected by setting this parameter to zero. The default setting is always used when changing from grid-connected to grid-forming or supporting modes which involve disconnecting the conveter from the grid because the measured grid voltage is disconnected from the converter, and so the converter can no longer control it.

Parameter | 01.040 Frequency Set-point
--- | ---
Short description | Frequency set point for grid-forming and grid-supporting modes.
Mode | Regeneration
Minimum | -200.00 | Maximum | 200.00
Default | See exceptions below | Units | Hz
Type | 16 Bit User Save | Update Rate | 2ms Read
Display Format | Standard | Decimal Places | 2
Coding | RW

Region | Default Value
50Hz | 50.00
60Hz | 60.00

Defines the frequency set-point for grid-forming and grid-supporting modes. The output phase sequence is U-V-W for positive values and reverse for negative values.

Parameter | 01.041 Frequency Droop
--- | ---
Short description | Simulated governor droop used in grid-support mode.
Mode | Regeneration
Minimum | 0.00 | Maximum | 50.00
Default | 5.00 | Units | %
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 2
Coding | RW

A governor is simulated in grid-support mode with frequency droop as follows.

Frequency Droop = [Frequency Set-point (01.040) x Grid Power (P) (01.001) / (√3 x A.c Voltage Set-point (01.030) x Rated Current (05.007))] x Frequency Droop (01.041) / 100%

The droop system reduces the frequency when Grid Power (P) (01.001) is positive (exporting power) and boosts the frequency when Grid Power (P) (01.001) is negative (importing power). As this is intended to simulate a generator the polarity of the power is always taken as though Regen Sub-mode (01.003) = 1 (Generator).

This parameter has no effect in grid-connected or grid-forming modes.

Parameter | 01.042 Frequency Offset
--- | ---
Short description | Offset applied to the frequency set-point.
Mode | Regeneration
Minimum | -400.00 | Maximum | 400.00
Default |  | Units | Hz
Type | 32 Bit Volatile | Update Rate | 2ms Read
Display Format | Standard | Decimal Places | 2
Coding | RO, ND, NC

This parameter is used to provide a smooth transition between grid modes. See Grid-mode Changeover State (01.020) for more detail.

Parameter | 01.043 Frequency Offset Reset Rate
--- | ---
Short description | Rate at which the frequency offset is reduced to zero.
Mode | Regeneration
Minimum | 0.00 | Maximum | 100.00
Default | 1.00 | Units | s/100Hz
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 2
Coding | RW

Frequency offset reset ramp rate specified in seconds per 100Hz.

Parameter | 01.044 Frequency Set-point Ramp Rate
--- | ---
Short description | Ramp rate applied to the frequency set-point.
Mode | Regeneration
Minimum | 0.00 | Maximum | 100.00
Default | 1.00 | Units | s/100Hz
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 2
Coding | RW

Defines the ramp rate applied to the Frequency Set-point (01.040) in seconds per 100Hz.

Parameter | 01.050 Start Mode
--- | ---
Short description | Action taken when the system is enabled in grid-supporting mode.
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 | Active Start
1 | Black Start Once
2 | Black Start

Grid-connected mode
This parameter has no effect.

Grid-forming mode
It is assumed that the system is never enabled on to a live supply and so a black start is always required, and so this parameter has no effect. On enable the rate of rise of voltage set-point is always controlled by Black Start Voltage Ramp Rate (01.051). Black Start Voltage Ramp Rate (01.051) can be set to zero if no ramp is required. The diagram below shows how the ramps operate during a black start.

Grid-supporting mode
This parameter defines the action taken when the system is enabled or re-synchronises. See Regen Synchronisation Mode (03.004) for more information.

Active Start:
When the system is enabled or re-synchronises pulse tests are carried out to measure the supply frequency and voltage. The measured values are used to calculate values for Voltage Offset (01.035) and Frequency Offset (01.042) to give a transient free start. Black Start Voltage Ramp Rate (01.051) has no effect.

Black Start Once:
The system performs a black start when the system is enabled. If the system re-synchronises because a transient causes an over-current condition to be detected, then pulse tests are carried out to measure the supply frequency and voltage and the measured values are used to calculate values for Voltage Offset (01.035) and Frequency Offset (01.042).

Black Start:
When the system is enabled or re-synchronises it starts immediately using the method described above for a black start. Voltage Offset (01.035) and Frequency Offset (01.042) are set to zero.

Parameter | 01.051 Black Start Voltage Ramp Rate
--- | ---
Short description | Time to ramp up the voltage when a black start occurs.
Mode | Regeneration
Minimum | 0.00 | Maximum | 100.00
Default | 1.00 | Units | s/100V
Type | 16 Bit User Save | Update Rate | Background Read
Display Format | Standard | Decimal Places | 2
Coding | RW

Black start ramp rate in seconds per 100V.

Parameter | 01.052 Black-start active
--- | ---
Short description | Indicates if a black start is active and the voltage is ramping up to the reference level.
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

If a black-start is active to ramp the voltage to the reference level this parameter is one, otherwise it is zero.