Active power conditioner for reactive and harmonic compensation having PWM and stepped-wave inverters

A compensator for reactive power and harmonic distortion on an alternating current three-phase power line that supplies power to a load, comprising:

• (a) pulse width modulated inverter means coupled to each phase of the three-phase power line, for producing three harmonic distortion compensation signals, each of which compensate for a harmonic distortion caused by the load on a different phase of the three-phase power line;
• (b) a stepped-wave inverter that produces a reactive compensation signal to compensate each of the three phases for a reactance of the load coupled to the three-phase power line;
• and
• (c) means for coupling the pulse width modulation inverter means and the stepped-wave inverter to the three-phase power line, while decoupling the pulse width modulator means from the stepped-wave inverter, so that a switching frequency of the pulse width modulation inverter means is substantially greater than a fundamental frequency of an alternating current flowing in the three-phase power line, while a switching frequency of the stepped-wave inverter is substantially equal to the fundamental frequency of the alternating current flowing in the three-phase power line.

Apparatus for compensating an unbalanced reactive load on a three phase power line, comprising:

• (a) a stepped-wave inverter coupled to each phase of the three phase power line, said stepped-wave inverter including a switching network that is controlled to produce a reactive power compensation signal for each phase as required to compensate the unbalanced reactive load;
• (b) means for monitoring current and potential on the three phase power line and producing signals indicative of the reactive power compensation signal required for compensating each phase for the unbalanced reactive load;
• and
• (c) control means, coupled to receive the signals, for providing gating signals to the switching network at unequal time intervals to produce the reactive power compensation signals required for compensating the reactive power for each phase of the unbalanced load.