Current feedback control for a power converter with multiple feedback loops

A control system for a power electronics converter comprising a valve arrangement and connected to a power grid, the control system comprising:

• processing circuitry;
• and
• data storage storing instructions executable by the processing circuitry to cause the processing circuitry to:
• run a first feedback control algorithm with an input based on a difference between a predetermined current reference and a first feedback current measurement of a current in the converter, wherein the first feedback control algorithm has a first control cycle time and includes at least proportional control using a proportional gain;
• run a third feedback control algorithm with an input based on the first feedback current measurement, wherein the third feedback control algorithm has the first control cycle time and acts on an output from the first feedback control algorithm after Safe Operating Area limits have been applied to the first feedback control algorithm output, the third feedback control algorithm including proportional control using the proportional gain but with a different polarity compared to the first feedback control algorithm;
• and
• run a second feedback control algorithm with an input based on a second feedback current measurement of the current, wherein the second feedback control algorithm has a second control cycle time and acts on an output from the third feedback control algorithm with the same polarity as the first feedback control algorithm and includes proportional control using the proportional gain, wherein the second control cycle time is less than the first control cycle time.

A method performed by a control system of a power electronics converter that comprises a valve arrangement and is connected to a power grid, the method comprising:

• providing a grid-side current controller for controlling power output from the converter to the power grid;
• as a first part of the controller, running a first feedback control algorithm with an input based on a difference between a predetermined current reference and a first feedback current measurement of a current in the converter, wherein the first feedback control algorithm has a first control cycle time and includes at least proportional control using a proportional gain;
• as a third part of the controller, running a third feedback control algorithm with an input based on the first feedback current measurement, wherein the third feedback control algorithm has the first control cycle time and acts on an output from the first feedback control algorithm after Safe Operating Area limits have been applied to the first feedback control algorithm output, the third feedback control algorithm including proportional control using the proportional gain but with a different polarity compared to the first feedback control algorithm;
• and
• as a second part of the controller, running a second feedback control algorithm with an input based on a second feedback current measurement of the current, wherein the second feedback control algorithm has a second control cycle time and acts on an output from the third feedback control algorithm with the same polarity as the first feedback control algorithm and includes proportional control using the proportional gain, wherein the second control cycle time is less than the first control cycle time.