Reactive power controller

A reactive power controller for a reactive power output from a self-commutated inverter having controllable rectifier elements, connected to an AC system power source via an AC reactor, the inverter alternatively acting as a capacitor or a reactor, comprising:

• first means for producing a DC reference voltage for the inverter from a reference signal of the reactive power to be controlled and a system voltage of the system power source to make equal the reactive power output from the inverter to the value of the reference signal of the reactive power;
• second means for producing a control signal for the inverter by conducting a differential operation between a DC voltage of the inverter and the DC reference voltage;
• and
• third means for comparing a phase of the voltage of the system power source with the control signal to output firing pulses for the controllable rectifier elements of the inverter, in which an output AC voltage of the inverter is controlled by varying a supply of an active power from the inverter or the system power source to the latter or the former via the AC reactor so that the DC voltage of the inverter may be equal to the DC reference voltage, and in which the variation of the active power supply is controlled by the control signal.