REACTIVE POWER COMPENSATOR FOR COMPENSATING A REACTIVE CURRENT COMPONENT IN AN AC NETWORK

摘要

1. Reactive-power compensator for compensating a reactive-current component in an alternating-voltage system, comprising a) a current converter bridge circuit (1 - 4 ; 27, 28) having an alternating-voltage input (19) which is to be connected to alternating-voltage system (18) and a direct-current output (20), b) forced-commutation current converter rectifiers (1 - 4) in all branches of the current converter bridge circuit, which rectifiers are arranged in such a manner that a defined current direction is produced at the direct-current output (10), c) a capacitor (9) which is connected in parallel with the alternating-voltage input (19), and d) a smoothing choke (10) as termination at the direct-current output (20), e) a drive unit (11) for driving the forced-commutation current converter rectifiers (1 - 4) and f) a pulse-width modulator (12) which is connected to this unit and which g) outputs, with a put se frequency (f) which is greater than the frequency of the alternating-voltage system (18), h) width-modulated, approximately rectangular current pulses (I, I1 , I2 ) for controlling the commutation process as determined by a control voltage (Us ) dependent on the magnitude and phase of the reactive-current component (IB ) to the drive unit (11) in such a manner that the fundamental oscillation of the compensation current (I) is identical in frequency and amplitude with respect to the reactive-current component (IB ) but shifted in phase by 180 degrees, characterized in that i) for the purpose of generating a sinusoidal control voltage (US ), a first multiplier (13) is provided which multiplies a reference voltage (UR ), which is phase-shifted by an angle of 90 degrees with respect to the system voltage (UN ) of the alternating-voltage sytem (18), or amplified reference voltage (a. UR ) by a multiplication factor (M), the magnitude of which is proportional to the magnitude of the reactive-current component (IB ) and which changes its sign when the reactive-current component (IB ) changes between the inductive and the capacitive range.