Research On Multi-Channel Interleaved Single-Phase Power Factor Correctors

Along with the traditional energy crisis and the sustainable development problem, the power electronic technology has been developed rapidly. As a number of power electronic equipments have been connected to single-phase power grid to supply DC voltage or AC voltage, the remarkable economic and social benefits are obtained. However the harmonic current pollution brought by the devices, especially the switching power supply and AC-DC-AC converter with a rectifier bridge and electrolytic capacitor, is very serious. Power factor correction, especially active power factor corrention (APFC) has become an important method to solve the harmonic pollution. APFC employing analog control chip which has been widely used in industry applications, has obtained good correction effect. As the power stage of single phase equipment increases, in some applications such as high power air condition, its input current is close to 50A and its output power is close to 10kW, when PFC working under the rated input voltage. As a result, the control chips are required to support higher power. In addition, IEC61000-3-12 was established to restrict the harmonic current when the single phase current is more than 16A and less than 75A. In order to cater to this trend, many semiconductor companies have developed some analog chips based on different control principle, which can support higher power and overcome the disadvantages of single-channel APFC such as power components selection, cost, installation, power loss and EMI suppression. Multi-channel interleaved APFC should solve the load banlance problem between every channel. The existing analog control chips adopt appropriate strategy to solve this problem, and get a good effect. There are many areas worthing to study further.Based on the above considerations, this paper does a thorough research on multi-channel interleaved PFC at the sight of circuit design, current share method, control principle, circuit working characteristics and simulation experiment analysis. It has a great pratical and theoretical value.The main research work is as follows:(1) Do a detailed analysis on multi-channel interleaved circuit and establish the control circuit without output voltage sensing circuit based on open loop control theory. The nature of PFC control method is pointed out. The duty cycle is more than 1 at input voltage's zero point, but in practical the duty cycle must be less than 1, so single-phase APFC is a quasi-converter.(2) Do a research on the double closed loops control method, inductor current synthesis principle and relationship between the IGBT current and duty cycle. And design the current and voltage loop. Finally, a PFC with 3kW output power, 35kHz switching frequency and 350μH inductor is designed and realized based on UCC28070 developed by TI company. The results show that interleaved APFC employing double closed loops control and current synthesis theory is feasible.(3) Do a research on one cycle control method and four-channel interleaved PFC working characteristics. A four-channel interleaved PFC is designed and realized based on two control chips. The results show that current stress can be reduced greatly and the efficiency can be improved by 2%.(4) This paper establishes the EL (Euler-Lagrange) mathematical model of four-phase interleaved power factor corrector (PFC) which is working in continuous conduction mode (CCM) based on its power circuit. The passivity of four-phase interleaved PFC is proved and passivity-based controller using stated variables feedback, damping injection method is designed in this paper. The proposed control scheme which don't need proportion integral controller has strong robustness on disturbance of input voltage, load and parameters of system components. Especially in applications of wide range load, the dynamic response of input current is very fast and the output voltage almost has no changes so that the power factor correction and constant DC output functions of PFC are realized. Meanwhile, multi-phase interleaved PFC employing passivity-based controller has a good effect on current sharing. Simulation results show that the passivity-based controller has a superior performance and the method is feasible.