The Research On Voltage-Source Matrix Converter And Its Application As Unified Power Flow Controller

Unified power flow controller (UPFC), a typical and the most flexible controller of FACTS, could control the impedance, angle, and the real and reactive power flow of transmission line. Matrix converter is a direct AC-AC converter, which has competitive advantages that intput powe factor could be controlled, output voltage could be adjusted, and power could flow bi-directionally. Applying matrix converter in unified power flow controller is a focal research at present.This paper introduces the traditional bi-directional-nine-switch matrix converter about the circuit topology, safe switch control and converter control approaches, and then analyzes a novel voltage-source matrix converter deeply. Firstly, the mathematical models of voltage-source matrix converter in a-b-c coordinate system and d-q-0 coordinate system are set up. The analysis results on its switch modulate matrix indicate that the amplitude, phase and frequency of output voltage and input fundamental displacement factor of this converter could be controlled freely. Sequentially, a double closed-loop structure, which is composed of the outer object control loop and the inner current control loop, is presented to satisfy the control goals of voltage-source matrix converter. Applying the hysteresis current control strategy of current control voltage-source inverter in the voltage-source matrix converter, the whole control structure could be achieved. Simulation results show that input signal and the output signal are both sinusoidal, and they also indicate that the double closed-loop structure could reduce output harmonious waves, improve the current quality and speed converter dynastic response. In the last chapter, the UPFC performed by voltage-source matrix converter is studied. Its mathematics model and control structure are set up, and its operation principle is analyzed. Furthermore, the method of harmonious waves elimination of the converter is discussed. Simulation results verify that that the voltage-source matrix converter acts as UPFC in power ystem is feasible and correct.