Research And Optimal Design Of Two-stage DC/AC Inverter With Hysteresis Current Control

With the extensive application of DC/AC inverters, it is urgently requested that DC/AC inverter should not only work in a stable way, but also realize high power density, high efficiency, low EMI and fast dynamic response to load. In this thesis, two-stage DC/AC inverter with hysteresis current control is studied and designed optimally. Its front stage comprises of two double-switch forward DC/DC converters with interleaved parallel, and its back stage is a DC/AC inverter with hysteresis current control.Compared with several other DC/DC circuits, the interleaved parallel double-switch forward DC/DC converter was chosen as the front part of two-stage DC/AC inverter with hysteresis current control. It was simulated and its operating principle was analyzed. By analyzing its control strategy and the principle of control circuit, and comparing the efficiency of the converter and its influence on the choice of components in back stage, it is determined to select open-loop control or closed-loop feedback control. For interleaved parallel double-switch forward DC/DC converter, the selection criteria of parameters and its design methods were introduced in detail.The back stage of the inverter employ hysteresis current control, in which is strongly nonlinear of its current internal ring, which can reduce the second-order oscillation link of the LC filters composed of the output filter and capacitance to the first-order to improve the stability of the system. And its external ring increases the accuracy of DC/AC inverter voltage output as well as the dynamic performance of the system. Through steady-state and dynamic simulation of the DC/AC inversion bridge, it is indicated that the inversion bridge's output voltage is low, its dynamic respond speed is fast, and it can adapt to a variety of load. When the input power or the load suffered mutation, the output voltage of the DC/AC inverter is basically not affected.The parameters selection of the current hysteresis control has a great impact on the circuit. Hysteresis widthΔI of the options will affect the quality of the output voltage waveform, the switching frequency of DC/AC inverter, the ripple of inductor current and the dynamic response speed. In addition to high efficiency, high power density, the inverter requires fast dynamic response and lower ripple voltage output, which is closely related to the design of the filter. Thus, the design of the filter inductance ensures and optimizes the quality of the waveform, with the dynamic properties of the system, the rate of load adjustment, volume, weight, audio, noise and other factors taken into account. The selection criteria and design method of the main circuit devices are introduced in details.Two 1 kVA prototypes of two-stage DC/AC inverter with hysteresis current control were developed and optimized on a same experiment platform:①220V±10%DC/ 115V50HzAC;②220V±10%DC / 220V50HzAC. By comparing the performance of two prototypes, it was discussed how the load current and output voltage of front stage (input voltage of back stage) influence on the efficiency of DC/AC inverter, then the basis for the circuit optimization was obtained. The experimental results demonstrate that two-stage DC/AC inverter with hysteresis current control has comprehensive performances such as high power density, high efficiency, small bulk and weight, high steady precision, fast dynamic response, and strong ability of anti-short-circuit and high reliability.