Development Of Single-phase Digital APFC Dedicated For Inverter Air Conditioner

With the promote of power semiconductor technology,microelectronic technology and control technology, power electronicstechnology has quickly developed. It provides power supply and powerconditioning for a variety of applications. Efficiency, environmentallyfriendly process, green transformation and precise power supply hasbecome the mainstream development of power electronics field.In the field of single-phase AC-DC power converters, because ofuncontrolled diode rectifier-bridge as the former circuit and electrolyticcapacitor filter circuit as the post circuit, this AC-DC converter showsnon-linear load characteristic at mains side. Since the displacement factorand distortion factor less than1, the power factor is low and harmoniccurrent is formed at mains. These worsen EMC indicators.Inverter-fed air conditioner is mainly application for single-phase ACpower supply. The basic circuit is as follows: a single-phase AC-DCconverter—three-phase voltage source inverter—PMSM compressorfrequency control system. In order to pass "3C" certification or CEcertification, power factor correction as one of the essential functions insingle-phase AC-DC converter, i.e. single-phase active power factorcorrection (APFC) is highly demanded. With the development ofInverter-fed air conditioners, the following application characteristics ofsingle-phase active power factor corrections for inverter-fed air conditionerhave been developed:(1) Expanded power high limit, exceeding5kW and reaching10kW;(2) Expanded switching frequency high limit, reaching40kHz;(3) Miniaturized boost inductor, easy to be installed on board; (4) Modular power circuit with enhanced power density;(5) Diverse power circuit, supporting more power output;(6) Simplified and digitized control strategies, output voltage applingfollowing control.Based on the development trends of inverter-fed air conditionersingle-phase APFC, this paper proposes the research content and researchobjectives, and introduces new control strategies, digital control and5kWAPFC power module. The theoretical and simulation has been analyzed,and experimental has been studied. The academic achievements havetheoretical significance and practical value.The main work is listed below:(1) The small-signal model of single-phase APFC and transferfunction of power circuits have been established, and traditionaldouble-loop control theory has been analyzed.(2) The double-loop control theory which is a notch filter outer loop,PR controller inner loop has been analyzed. In terms of this control theory,the mains current keeps in good sinusoidal waveform.(3) The novel current quasi-inner loop of single-phase APFC has beenproposed. The theoretical and simulation analysis shows that the novelcontrol strategy has fast dynamic response;(4) Based on PD78F1213, single-phase digital APFC power moduleis achieved by means of the aforementioned two control strategies. Therated output power is5kW, the switching frequency is35kHz, and theinductance is350H. APFC has good effects on power factor correctionand is cost-effective, which makes output voltage follows the input voltageand output power (which can reduce electrical stress of power devices),and also has hysteretic control function under light load (which canimprove efficiency at light load). These functions fully meet thedevelopmental characteristics of single-phase APFC for inverter-fed airconditioner; (5)This paper proposes a new single-phase M level and N powerdevices in parallel APFC which is driven by shift phase control method.Then, the EL (Euler-Lagrange) mathematical model of MN APFC powercircuit which is working at CCM is established. In the proof of thepassivity of MN APFC, the passivity-based controll is designed in thispaper. The control strategy doesn’t need proportion integral controller hasstrong robustness on disturbance and the parameter configuration is simple.Meanwhile, this control strategy can maintain a stable DC voltage, and hasfast dynamic response of input current. The APFC with multiple switchesin parallel appling passive control strategy has a good effect on currentsharing. The simulation results show that APFC has a superior correctioneffect with passive control strategy and suitable for inverter-fed airconditioner.