Second Order Sliding-Mode Control Research For Buck Inverter

Inverter is a device which can convert DC to AC with the power switches turning on and turning off in regularly. With the rapid development of power electronic technology and the maturity of high power switches and integrated control circuit technology, inverter has been widely used in many applications. With the development of all kinds of industries, to the requirement of power quality is higher and higher. the output voltage waveform of the inverter should track the given reference voltage accurately in many fields. And inverter needs fast dynamic response. In order to e inverter can adapt to a higher applicate requirements, the paper does research on the second-order sliding-mode control of buck inverter to improve the fast dynamic responses and robustness against parameter uncertainties and load disturbances. The paper makes the research and design as follow:(1) Does research on the operation principle of buck inverter, build mathematical model of circuit. And propose a new control approach for buck inverter,that is second-order sliding-mode control with a simple state machine structure. Through establish the mapping relation between the effective state and the switch state of inverter main circuit, depending on condition of different and external switch, to realize the switch of the state-machine output control and regulate the output voltage of inverter.(2) Obtained the system optimal phase plane trajectory by analyze the phase plane trajectory of Buck inverter's output voltage and inductor current, and calculated the optimal switching point of power switch. Established the sliding surface of system, according the input voltage of inverter,the reference voltage and the sliding variable to deduce the adaptive parameter of second-order sliding mode controller. By introducing a hysteresis parameter to limit the switching frequency of inverter, combining with the adaptive parameters of controller to analyze the system the steady-state trajectory and voltage tracking performance. Through simulation, verified the validity and reliability of the algorithm.(3) Design the hardware circuit of Buck inverter control system, and built a 720 VA experimental prototype. Respectively under the condition of linear and nonlinear loads, do the experiment on the start process and load disturbances,the results verified the buck inverter control system obtained a better control effect.The simulation and experimental results indicate the second-order sliding-mode algorithm succeed in controlling the buck inverter in quickly and stably. To compare to the exited control algorithm, under without current sensing or any integral term, the proposed second-order sliding-mode control algorithm can regulate the output voltage of inverter, it can quickly track any initial voltage without overshoots. Under load disturbance after only one switching action in steady state. Under nonlinear load, the presented controller is also succeed in regulating the output voltage of inverter. So, the proposed SOSM controller improved the fast dynamic responses and robustness against parameter uncertainties and load disturbances.