| With the continuous advancement of the green economy development mode,energy saving has become the main mode of energy reform.AC motors are the main power equipment for electrical energy consumption,and are widely used in electric vehicles,heavy machinery,urban rail transportation,and various largescale lifting devices.In the actual operating conditions of AC motors,there are frequent braking states,which will generate a lot of braking energy,and traditional energy-consuming braking will cause greater waste.Therefore,the AC motor energy recovery system that can realize braking energy recycling is widely studied.The bidirectional DC/DC converter is used as an intermediate link between the AC motor and the energy storage device in the system,which can realize the bidirectional flow control of energy.The research on its control can ensure the efficient and reliable operation of the system,which is of great significance.Firstly,determining the overall plan of the system and selecting the interleaved parallel structure as the main circuit structure of the converter.According to the designing requirements of the current ripple and voltage ripple of the converter,the parameter was calculated and designed for the energy storage inductance of main circuit,the high and low voltage side filter capacitors,and the switch tube are performed.At the same time,relevant auxiliary circuit design is carried out.According to the different working states of the converter,the working principle of the main circuit in Buck and Boost modes is specifically analyzed.Using the state space averaging method to model the small signal of the interleaved parallel bidirectional DC/DC main circuit.Determine the control strategy of low-voltage side tracking DC bus power with current limiting charging in Buck mode and high-voltage side constant voltage output in Boost mode.Then calculating the PI parameters of the controller in both modes.Collecting the analog output of AC motor inverter,monitoring the speed change of AC motor in real time,and design the control system of braking energy generation.The voltage and current sampling circuit were designed to collect the required control amount,designing the voltage and current double closed-loop controller in Buck mode and the voltage controller in Boost mode.At the same time,the switching control design of the converter working mode is made.PWM drive signal is outputed to control the converter.Control Desk was used to realize online monitoring of system parameters.Completed the construction of the experimental platform of the AC motor energy recovery system based on the d SPACE controller.Based on this,the bidirectional DC/DC converter verification experiment was made.The bidirectional DC/DC converter was controlled to work in Buck and Boost modes by switching mode.Charging and discharging of the super capacitor are realized,and the braking energy of the AC motor is recovered and reused.The experimental results show that the high and low voltage side voltage and current achieve good dynamic and static control performance. |
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