Zhang Chunpeng

A series voltage compensator based on thyristor-controlled transformer

Series compensation is an important way to improve transmission capability and power controllability of long-distance power delivery systems. Since typical series compensators have some limitations, this paper proposes a novel series voltage compensator based on thyristor-controlled transformer. By special configurations of transformer windings and thyristor converters, it is capable of injecting voltage phasors with adjustable magnitudes and phase angles. Taking the advantage of power semiconductor devices, this compensator responds much faster than mechanical compensators and permits frequent regulations. A SMIB system with two parallel transmission lines are taken as a study case. And simulation results show the injected voltage and regulated power by the compensator, which proves its effectiveness.

Virtual neutral point selection for three-leg railway power quality conditioner

With the development of series connection of IGBTs, the transformerless high-voltage converter becomes an important type utilized in power quality improvement applications. Electric railway is a kind of unbalanced load and the compensators based on three-leg converters are potential solutions for it. This paper proposes a modeling method for three-leg railway power quality conditioner, by means of selecting a virtual neutral point. This method, compared with conventional ways, replaces the two higher actual phase voltages by three lower virtual ones, which helps the converter lower the requirement of dc-link voltage level and the number of series-connected devices by about 30%. Simulation results prove that the control strategy based on this new model represents satisfying performances.

Power electronic zigzag transformer for experimental voltage generator

This paper presents a mid-voltage experimental voltage generator used for the testing mainly of distribution power equipment, high-power drives and renewable power generation. It utilizes thyristor-controlled zigzag transformer as its primary circuit. Based on the analysis of the operation mechanism, the voltage equations are derived and control strategy is proposed. This power electronic zigzag transformer is capable of providing various experimental voltage conditions, including voltage swell, voltage sag and phase angle change. It has more rapid and accurate response than impedance-type voltage regulators and has lower cost and less footprint than back-to-back voltage source converter. Simulation model is developed with PSCAD software and simulation results validates the proposed schemes.

Transformerless power router used as load balancer and uninterruptible power supply for auto-passing neutral section

This paper proposes a transformerless power router used in high-speed electric railway. Its primary circuit is based on a four-leg high-voltage converter which provides multiple power flow paths. Its voltage equations are established with a relocated neutral point. And a matching control strategy is presented which is helpful to lower the converter scale. This power router is capable of reducing the negative sequence currents injected into utility power system as well as providing uninterruptible power supply to the neutral section. Simulation results validates both the circuit topology and the control strategy.