| The quality of power has always been the focus of national attention,so appropriate measures need to be taken to avoid grid pollution.The traditional diode rectification cannot meet the requirements of "green energy conversion" due to the injection of a large amount of harmonics and reactive current on the grid side.Nowadays,dual PWM converters have become a research hotspot.The inherent characteristics of high power factor and bidirectional energy flow make it play a huge role in many fields such as motor drive.In the traditional dual PWM motor drive control system,the rectification side has been widely studied as its main part.Traditional three-phase voltage-type PWM rectifiers are limited by the topology and other factors.The DC bus voltage can only be boosted based on540 V,so the adjustable range of the DC bus voltage is relatively small.Due to the addition of the quasi-Z source network,the dual PWM motor drive control system based on the bidirectional quasi-Z source can not only achieve high power factor and bi-directional power flow on the grid side,but also implement the function of stepping down the output voltage and expanding the DC bus voltage.The voltage regulation range is more suitable for the speed regulation of the motor.Firstly,this paper introduces the structure,working principle,and mathematical model of the dual PWM motor drive control system based on bidirectional quasi-Z source.Analysis of the working principle proves that the system is more superior.For the rectifier side,a mathematical model of the three-phase quasi-Z source rectifier is established,and the state space equation and small signal equation are derived based on the two working states of shoot-through and non-shoot-through.The principle analysis and model establishment are verified by Matlab simulation.For the inverter side,a mathematical model of the permanent magnet synchronous motor is established,which provides a theoretical basis for the following control.Secondly,the rectification side of the dual PWM motor drive control system based on bidirectional quasi-Z source is studied.A three-phase quasi-Z source rectifier control strategy is proposed.The three closed-loop control structure ensures good control performance.In order to ensure the control effect,a genetic algorithm is introduced on the DC side based on the PI controller to obtain the most suitable parameters.A six-segment shoot-through SVPWM modulation strategy is used to implement a buck conversion of the output voltage by adding a shoot-through zero vector to the traditional seven-segment SVPWM.Simulation results show that the three-phase quasi-Z source rectifier can realize the boost/buck conversion of the DC bus voltage,while maintaining good dynamic performance.Thirdly,the inverter side of a dual PWM motor drive control system based on a bidirectional quasi-Z source is studied.In traditional vector control,when the motor is in a low speed state,the change of the speed will cause the change of the back-EMF.If the DC bus voltage remains unchanged,it will affect the current control effect.In order to solve the above-mentioned problems,a method for dynamically adjusting the DC bus voltage according to the change of speed is proposed,and the correctness of the method is verified by simulation.Finally,an experimental platform based on the DSP28335 controller was built,and the controller program was written to establish a complete dual PWM motor drive control system based on a bidirectional quasi-Z source.The stability of the system was verified by experiments. |
