Abstract: A phase adjustment circuit for sensing the phase of the signal at the output of an inverter and for providing a signal to the control circuits of the inverter whose phase has been offset by a preselected amount. The phase adjustment circuit includes a zero crossover detector for sensing the crossover points of the inverter output voltage. A phase-locked loop includes a phase comparator which receives the signal indicating the zero crossover points and a feedback signal from a phase shifter. The output of the phase comparator is an error signal which is integrated and presented to a voltage controlled oscillator to change the phase of its output signal. The phase shifter combines the phased waveform out of the voltage controlled oscillator with a command signal indicating the desired phase offset to form a feedback signal for presentation to the phase comparator closing the feedback loop.

Abstract: A control circuit for a force-commutated inverter connected intermediate a regenerative DC power source and a power grid, the power source/inverter combination operative to supply AC electrical energy to, or receive AC electrical energy from or adjust the power factor of, the AC electrical energy of the power grid. The control circuit of the present invention varies the real power component and the reactive power component of the electrical energy flowing between the electrochemical cell and the power grid through the use of two feedback loops with separate time constants. The first feedback loop allows for the independent control of the magnitude and direction of both the real power component and the reactive power component of the AC electrical energy flowing to or from the power grid. The first feedback loop also has a relatively slow time constant so that the power flow between the DC source and the power grid is substantially unaffected by transients.

Abstract: A method for controlling a force-commutated inverter coupled between an electrochemical cell and a power grid for adjusting the magnitude and direction of the electrical energy flowing therebetween. Both the real power component and the reactive power component of AC electrical energy flow can be independently varied through the switching waveform presented to the intermediately coupled inverter. A var error signal is derived from a comparison of a var command signal with a signal proportional to the actual reactive power circulating between the inverter and the power grid. This signal is presented to a voltage controller which essentially varies only the effective magnitude of the fundamental voltage waveform out of the inverter, thereby leaving the real power component substantially unaffected. In a similar manner, a power error signal is derived by a comparison of a power command signal with a signal proportional to the actual real power flowing between the electrochemical cell and the power grid.