Decoupled control of a Unified Power Quality Conditioner based on a current source topology for fast AC mains disturbance compensation

The Unified Power Quality Conditioner (UPQC) is a custom solution for power quality problems. The equipment corresponds to the back-to-back connection of a series and a shunt active filter, so the topology acquires the characteristics of both filters. It has the ability to compensate for voltage disturbances while improving the power quality for both the client and the distributor. In the present work a topology and a control strategy is proposed for a UPQC based-on current source converters. The proposed topology has the advantage of using a first-order filter on the series compensator side that enables a rapid response to disturbances in the supply voltage and does not present resonance problems as in voltage source converters based UPQCs. This work also presents a control strategy that allows operating the UPQC with good capacity to compensate supply disturbances, a high utilization factor of the dc bus, and allows the systematic design of the parameters of the controllers.

I. Introduction

Power quality issues affect suppliers and customers. The first are affected by the appearance of unwanted components in the currents, which generate problems in their distribution lines, while the latter are affected by disruptions in the supply voltage which can cause malfunction or failure of critical loads. The development of shunt and series active filters based on PWM converters allowed to propose solutions to the above problems [1] [2]. Active filters can compensate problems associated with the supply voltage and the load power factor, in the case of series active filters; and harmonic currents and the load power factor, in the case of shunt active filters. The principle of the active filters is to use a controlled voltage source in series connection between the PCC and the load and a controlled current source in shunt connection between the PCC and the load, so that these sources inject voltage and current components to compensate for supply and load disturbances. On the other hand, the basic principle of theses active filters is based on a dc element as energy accumulator in a way that the waveform of current or voltage is modulated by the converter as needed.