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1 Mask and Parameters
2 Inputs, Outputs, and Signals Available for Monitoring
- 2.1 Inputs
- 2.2 Outputs
3 Description
- 3.1 Secondary Control Loop – Voltage
- 3.2 Secondary Control Loop – Frequency
4 Intellectual Property Disclaimer

Grid-forming converters pose a steady state error in voltage and frequency due to the operation of the primary controller and the secondary controller provides setpoints to the primary controller to compensate for such deviations. The controller measures the RMS value of the voltage and frequency at the point of interest and estimates the adjusted references for voltage and angular frequency for the Primary control loop. To keep the system safe from abnormal deviation of voltage and frequency, limits have been added for both parameters in this control block. In addition, the rate of change for voltage and frequency can also be controlled in the Secondary controller.

Mask and Parameters

The following information is required by the configuration mask of the Reference Generation block:

Parameter	Description	Units
Nominal Operating Voltage	Nominal line-to-line RMS voltage of the grid-forming converter	V
Nominal Frequency	Nominal frequency of the grid-forming converter	Hz
Secondary Voltage Controller Gains, Proportional Gain (Kp)	Proportional Gain of the Secondary Voltage Control Loop	pu
Secondary Voltage Controller Gains, Integral Gain (Ki)	Integral Gain of the Secondary Voltage Control Loop	Pu/s
Secondary Frequency Controller Gains, Proportional Gain (Kp)	Proportional Gain of the Secondary Frequency Control Loop	pu
Secondary Frequency Controller Gains, Integral Gain (Ki)	Integral Gain of the Secondary Frequency Control Loop	Pu/s
Upper Frequency Limit	Maximum Limit of the frequency. The secondary controller saturates to this value.	Hz
Lower Frequency Limit	Minimum Limit of the frequency. The secondary controller saturates to this value.	Hz
Upper Voltage Limit	Maximum Limit of the Voltage (L-L, RMS). The secondary controller saturates to this value.	V
Lower Voltage Limit	Minimum Limit of the Voltage (L-L, RMS). The secondary controller saturates to this value.	V
Maximum Rate of Voltage Change	Maximum rate at which the secondary controller can change the voltage reference	pu
Maximum Rate of Frequency Change	Maximum rate at which the secondary controller can change the Frequency reference	pu
Sample Time	Input sampling period	sec

Inputs, Outputs, and Signals Available for Monitoring

Inputs

Parameter	Description	Units
Frequency	Measured System frequency	pu
Voltage	Measured RMS voltage at the Point of Interest	pu
Reset	Reset Signal	-

Outputs

Parameter	Description	Units
Vref	Reference Voltage for the primary control loop	pu
Omega_ref	Reference Angular frequency for the primary control loop	pu

Description

The block contains secondary control loops for voltage and frequency adjustments. Brief descriptions of the adopted Outer Control Loop approaches are as follows.

Secondary Control Loop – Voltage

This loop takes the RMS value of the measured voltage and compares it with the reference. The error signal is then passed to a PI controller. To keep the system safe from abnormal deviation of voltage, a rate limiter and a saturation block are used. The control architecture of the Secondary Control Loop for Voltage control is shown below.

Secondary Control Loop – Frequency

This loop takes the measured frequency and compares it with the reference. The error signal is then passed to a PI controller. To keep the system safe from abnormal deviation of frequency, a rate limiter and a saturation block are used. The control architecture of the Secondary Control Loop for Frequency control is below.

Intellectual Property Disclaimer

Natural Resources Canada owns all intellectual property rights in the Smart Inverter Modelling Toolbox software and related products.

ARTEMiS User Documentation

Secondary Controller Three Phase