Active power conditioner for reactive and harmonic compensation having PWM and stepped-wave inverters
First Claim
1. Apparatus for actively compensating a reactive power load and a harmonic distortion on an alternating current power line, comprising:
- (a) a stepped-wave inverter that produces a reactive compensation signal for use in dynamically compensating the reactive power load;
(b) a pulse width modulation inverter that produces a harmonic compensation signal on its output terminals for use in compensating the harmonic distortion on the power line; and
(c) means for coupling the reactive compensation signal and the harmonic compensation signal to the power line, so that the reactive power load and the harmonic distortion on the power line are compensated by said signals, and so that a voltage level across the output terminals of said pulse width modulation inverter is substantially less than a voltage on the alternating current power line.
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Accused Products
Abstract
An active power quality conditioner for compensating reactive power and harmonic distortion in power systems. A pulse width modulated (PWM) inverter (70) for each phase is controlled to produce a harmonic distortion compensation signal that is coupled to an inductor. The inductor is connected in series between a stepped-wave inverter (84) and one phase of the power line. A current produced by the stepped-wave inverter compensates for the reactance of a load coupled to the power line. The PWM inverter operates at a frequency that is substantially greater than the fundamental frequency of the power line and is not exposed to the full power line voltage; it can be constructed using components of relatively low power and voltage rating. In contrast, the stepped-wave inverter, which is decoupled from the PWM inverter, operates at the fundamental frequency and is subjected to most of the stress. Both shunt coupled and series coupled compensators are described. Compensation for an unbalanced load is provided using a compensator (364) that includes a 24-pulse stepped-wave inverter (366).
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Citations
29 Claims
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1. Apparatus for actively compensating a reactive power load and a harmonic distortion on an alternating current power line, comprising:
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(a) a stepped-wave inverter that produces a reactive compensation signal for use in dynamically compensating the reactive power load; (b) a pulse width modulation inverter that produces a harmonic compensation signal on its output terminals for use in compensating the harmonic distortion on the power line; and (c) means for coupling the reactive compensation signal and the harmonic compensation signal to the power line, so that the reactive power load and the harmonic distortion on the power line are compensated by said signals, and so that a voltage level across the output terminals of said pulse width modulation inverter is substantially less than a voltage on the alternating current power line. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A compensator for reactive power and harmonic distortion on an alternating current three-phase power line that supplies power to a load, comprising:
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(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. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. Apparatus for compensating an unbalanced reactive load on a three phase power line, comprising:
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(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. - View Dependent Claims (27, 28, 29)
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Specification