Research On Control Of A Single Phase Bidirectional AC-DC Half Bridge Converter

With the development of economy and the progress of society, energy shortage is becoming more and more serious. Energy feedback reuse system has become a hotspot of researchers all over the world. Putting the energy feedback reuse system into use will significantly improve the efficiency of energy use, which will relieve or solve the problem of energy shortage effectively. Bidirectional AC-DC Converters serve as the bridge of bidirectional power flow in the energy feedback reuse system has drawn the attention of numerous researchers and been wide used. The energy feedback reuse system composed of bidirectional AC-DC converters, battery energy storage system, and other facilities, is being widely used in battery energy storage system of microgrid, lithium battery formation control system and alternating UPS system, which has great importance to the research of control schemes of the bidirectional AC-DC converters, better implement of bidirectional power flow, and the reuse of energy.This thesis gives a detailed discussion about the research prospects and significance of bidirectional AC-DC converter and the analysis of the indispensible role the bidirectional AC-DC converter plays in several common battery storage system. Then, several frequently-used control strategies for the bidirectional AC-DC converter are listed. At last, one-cycle control algorithm is selected as the key research subject. Furthermore, this thesis analyses the operational principle of single phase half bridge bidirectional AC-DC converter using one-cycle control algorithm, and builds both the large signal model and small signal model of single phase half bridge bidirectional AC-DC converter. Besides, the stability conditions of one-cycle control algorithm and the compensation design of outer voltage loop is analyzed. Afterwards, the unbalance of the bridge capacitor of the single phase half bridge bidirectional AC-DC converter is analyzed, and the corresponding solutions are proposed. On this basis, simulation that verifies the feasibility and stability of the implement of bidirectional power flow by using one-cycle control and balance of the bridge is run through the simulation software PSIM.To verify the practicability of one-cycle control algorithm, a digital control system of single phase half bridge bidirectional AC-DC converter using TMS320F28069 DSP controller is designed. In this thesis, the digitization and sampling method of one-cycle control algorithm is discussed in detail. At the meantime, the control program flow, the selection of key parameters, as well as the design of digital compensator are introduced. On this basis, a 400 W single phase half bridge bidirectional AC-DC converter experimental hardware platform is built, which includes selection of power devices, design of filter inductance, selection of bridge capacitors, design of drive circuit and protection circuit, and so on. Combined with the digitization design of one-cycle control and the establishment of the experimental platform, the experimental results verify the feasibility and stability of the one-cycle control algorithm applied in single phase half bridge bidirectional AC-DC converter.