| With the advantages of high efficiency,high reliability and high power density,the permanent magnet motor is widely used in the field of the household appliances.In recent years,the electrolytic capacitor-less drive technology has become the research emphasis in the household appliance.The electrolytic capacitor-less driver with small film capacitors can achieve high power factor at the grid side without power factor correction circuit.At present,the research on the electrolytic capacitor-less drive control technology has made important progress.However,there are still some core technical problems in the application of the inverter air-conditioner,including the resonance phenomenon between the line inductance and the DC-link capacitance,the large significant position observation error,and high torque control complexity.According to the industrialization requirements,the above research directions have been deeply studied in the dissertation,and the theoretical and technical support are provided for the application of single-phase electrolytic capacitorless compressor drive control technology in the air-conditioner.Due to the reduction of the DC-link capacitance and the influence of the negative impedance characteristics of the motor,the electrolytic capacitor-less drive system is prone to the resonance between the line inductance and the DC-link capacitance,resulting in the current distortion on the grid side and affecting the stability of the drive system.For this problem,a resonant suppression strategy based on the DC-link voltage harmonic estimation is proposed in this dissertation.Based on the motor-side model and the digital delay of the drive system,the impedance model is established and the resonant principle of the electrolytic capacitor-less drive system is illustrated.Aiming at the difficulty of extracting the resonant information with the small DC-link capacitance and the inductance value,a method of reconstructing the DC-link voltage resonance component using the rectifier output current is studied.And the feedback loop based on the harmonic estimation of the DC-link voltage is established to improve the damping characteristics of the system.According to the input impedance transfer function with the active damping control,the influence of the active damping controller gain and the current controller parameters on the stability and harmonic suppression ability of the system is stated,and then the optimal matching parameters of the control system are obtained.The experimental results show that the proposed method can suppress the harmonics in the grid current and DC-link voltage effectively.Then the power quality of the compressor drive system can be improved.The DC-link voltage fluctuation of the electrolytic capacitor-less drive system can cause the harmonics in the extended back electromotive force,which can lead to the observation error of the rotor position,and then affect the operating quality and stability of the system.In order to realize the accurate decoupling control of the system,the position observation method based on the cross-decoupling complex filter is proposed.According to the analysis of the influence of the harmonics on the position observation,the harmonic and position error characteristics of the extended electromotive force are announced.The fundamental components of the extended electromotive force are extracted by the first-order complex filter,and the rotor position observer for the crossdecoupling filter is built.Then,the discretization and parameter of the complex filter are matched.The performance of the complex filter can be enhanced by cross decoupling.The model of the complex filter after cross decoupling is established,and the effect of the filter on eliminating the compressor position error and improving the operation stability can be verified using the frequency characteristics and pole-zero analysis.The experimental results show that the proposed control method can suppress the rotor position error effectively caused by the DC-link voltage fluctuation and improve the rotor position observation accuracy of the electrolytic capacitorless compressor drives.The load of the single rotor compressor for air-conditioner applications can lead to the fluctuation which is double frequency with the mechanical period,resulting in the significant impacts on the output torque and operation speed of the compressor.In addition,the large fluctuation of the DC-link voltage in the electrolytic capacitor-less drive system can further aggravate the fluctuation of torque and speed,and affect the stability of the system.Therefore,an optimal control strategy of compressor torque based on the acceleration reconstruction and DC-link voltage regulation of the compressor rotor is proposed.Firstly,the mechanism of compressor torque and speed pulsation of the electrolytic capacitor-less compressor drive system is analyzed.In order to suppress the negative effects of the periodic pulsation,an improved feedforward compensation strategy is studied to suppress the speed fluctuation by extracting the rotor acceleration information.The DC-link voltage closed-loop control scheme is constructed to suppress the DC-link voltage pump rise caused by the load torque fluctuation.The DC-link voltage control strategy based on PIR controller is analyzed,which can suppress the torque and speed fluctuations and improve the control performance of the closed-loop system.In turn,aiming at the problem of the limited speed regulation range in the electrolytic capacitor-less permanent magnet compressor drive system,a magnetic-weakening control strategy based on the cross-axis voltage feedback is studied,which can effectively broaden the operating range of the speed and improve the operation stability of the airconditioner system.Finally,a prototype of the electrolytic capacitor-less permanent magnet compressor driver is developed,and the control strategy is integrated to realize the digital control system.The operating condition test of refrigeration and heating is carried out in the electrolytic capacitor-less permanent magnet compressor driver system in the inverter airconditioner,including power quality operating efficiency test on the grid side,and performance test of the air conditioner.The experimental results show that the system can meet the requirements of harmonic,power factor,vibration,noise and energy efficiency of the air conditioner,and verify the effectiveness of the electrolytic capacitor-less drive control strategy.The work provides significant support for the development of new frequency conversion air-conditioner applications based on electrolytic capacitorless permanent drives. |
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