CONTROL METHODS FOR VSC ACTIVE RECTIFIER/INVERTERS UNDER UNBALANCED OPERATING CONDITIONS

摘要

A discrete-time voltage-oriented control (DT- VOC) scheme for controlling a voltage source converter (VSC) active rectifier/inverter (2) involving the calculation of a discrete-time model of the active rectifier/inverter and load system for both balanced and unbalanced operating conditions.The active rectifier/inverter (2) will include a plurality of semiconductor switching devices operated in accordance with a pulse width modulation (PWM) strategy. The ac terminals of the active rectifier/inverter will be connected to a lo system such as an active filter (8) and a supply network, optionally via a transformer (10) and protective switchgear. The discrete-time model will be calculated in DT-VOC function block (14) of the digital controller (12) use active and reactive power references P* and Q*, respectively to derive modulation indexes. PWM controller (18) applies the gate drive command signals to control the semiconductor power switching devices to achieve desired levels of active and reactive power at the ac terminals of the active rectifier/ inverter that corresponds to the active and reactive power references P* and Q*.