Voltage-Sourced Converters in Power Systems

3

Control of Half-Bridge Converter

3.1 INTRODUCTION

Chapter 2 introduced the four-quadrant DC/AC half-bridge converter and developed its dynamic model based on the averaging method. The half-bridge converter serves as a building block for the three-phase DC/AC voltage-sourced converter (VSC). Therefore, a clear understanding of the dynamics and control of the half-bridge converter is essential to a comprehensive treatment of the dynamics and control of a three-phase VSC system.

This chapter employs the averaged dynamic model developed in the previous chapter to study the control of the half-bridge converter. We introduce the structure of the controller, review the frequency-response approach to the controller design, and identify the controller requirements to ensure quality command following and disturbance rejection properties. Furthermore, we demonstrate the effectiveness of the feed-forward compensation technique in mitigating the dynamic couplings between the half-bridge converter and the AC system, improving the start-up transient of the converter system, and enhancing the disturbance rejection capability of the converter system. The insight gained from this chapter will be used in subsequent chapters for the control of the three-phase VSC.

3.2 AC-SIDE CONTROL MODEL OF HALF-BRIDGE CONVERTER

Hereinafter, for the sake of compactness, the overbar is dropped from the averaged variables throughout the rest of the book. However, we shall remember that the averaging operator is ...