A Study Of Bi-directional Full-Bridge DC/DC Converter Based On Digital Control

Bi-directional DC/DC Converter (BDC) is the two-quadrant operating DC/DC converter. The power can flow in either direction between two DC sources. BDC performs as two DC/DC converters. With the development of the science and production, BDC is increasingly used in applications such as DC uninterruptible power supply, aerospace power supply, and auxiliary power supply of electric vehicles, etc. The employing of BDC can reduce the size, the weight, and the cost of power system. This thesis is concentrated on the research of the digital controlled Bi-directional, isolated, full-bridge DC/DC Converter. This converter is usally used in high power applications.In chapter one, the conception, creation of the bi-directional DC/DC converter are presented, and the bi-directional, isolated, full-bridge DC/DC converter is proposed. The converter is operated with dual full-bridges placed on each side of the isolated transformer. The high voltage (HV) side is connected to the dc generator supply, and the low voltage (LV) side is connected to the battery. In chapter two, the operating principle of the bi-directional full-bridge DC/DC converter is introduced. When power flows from the HV-side to the LV-side, the converter works in buck/charge mode to charge the LV-side battery, and the switching signal on HV-side is turned on, on LV-side is locked; otherwise, it works in boost/discharge mode to power the HV-side load, and the switching signal on LV-side is turned on, on HV-side is locked. Charge mode works as isolated full-bridge DC/DC converter, and the discharge mode works as isolated full-bridge boost converter. Chapter two also proposed some problems and the solved methods, such as the loss of duty ratio, voltage spike, startup controlling, etc. In chapter three, an extended state-space averaged model is developed to build the small signal model of the converter in both directions of power flow. A PID controller is designed to make the system has a satisfactory transient response against the disturbance.Finally, a 200W prototype has been built. The design of hardware and software, realization of digital PID controller, etc are introduced in detail. The experimental results of the converter are proposed to confirm the theory analysis.