Grid side inverter system arranged for controlling current injection when a phase locked loop controller is misaligned

An electric power generating system comprising:

• a grid side inverter system, comprising:
• a grid side inverter;
• a phase locked loop controller arranged to determine a phase of a dq-frame dependent on a monitored grid voltage vector in the dq-frame and a reference grid voltage vector in the dq-frame;
• a current reference decision controller arranged to generate a reduction of at least one of an active and a reactive current reference, wherein a decision to generate the reduction is based on an electrical parameter relating to a phase difference between a grid phase of the monitored grid voltage vector and the phase of the dq-frame;
• a current controller arranged to determine control signals for the grid side inverter for controlling generation of active and reactive power) to the grid dependent on the active and reactive current references and monitored active and a reactive grid currents in the dq-frame;
• a power source;
• and
• wherein the generation of the reduction comprises reducing at least one of the active and reactive current references to a predetermined current reference or references.

A method for controlling a grid side inverter connected to a power grid during a grid event such as a low voltage grid event, the method comprising:

• determining a phase of a dq-frame dependent on a monitored grid voltage vector in the dq-frame and a reference grid voltage vector in the dq-frame;
• generating a reduction of at least one of an active and a reactive current reference, wherein a decision to generate the reduction is based on an electrical parameter relating a phase difference between a grid phase of the monitored grid voltage vector and the phase of the dq-frame;
• determining control signals for the grid side inverter for controlling generation of active and reactive power to the grid dependent on the active and reactive current references and monitored active and a reactive grid currents in the dq-frame;
• and
• generating the reduction further comprising reducing at least one of the active and reactive current references to a predetermined current reference or references.

A computer program product comprising code which, when executed by one or more computer processors, perform an operation to control a grid side inverter system, the operation comprising:

• determining a phase of a dq-frame dependent on a monitored grid voltage vector in the dq-frame and a reference grid voltage vector in the dq-frame;
• generating a reduction of at least one of an active and a reactive current reference, wherein a decision to generate the reduction is based on an electrical parameter relating a phase difference between a grid phase of the monitored grid voltage vector and the phase of the dq-frame;
• determining control signals for the grid side inverter for controlling generation of active and reactive power to the grid dependent on the active and reactive current references and monitored active and a reactive grid currents in the dq-frame;
• and
• generating the reduction further comprising reducing at least one of the active and reactive current references to a predetermined current reference or references.