Research And Implementation Of 50kW AC Electronic Load With Dc Energy Feedback

At present,the power supply device is widely used in various industries.To ensure the performance,the power supply usually needs to be tested with load before leaving the factory.In view of the disadvantages of traditional load,such as low energy utilization rate,inconvenient load size adjustment and so on,this paper develops a 50 KW DC energy feedback AC electronic load for the test of a kind of inverter power supply.According to the characteristics of DC input of locomotive inverter power supply,the electronic load adopts modular parallel connection and the modular circuit adopts load simulation + DC energy feedback two-stage structure.Compared with the way of AC energy feedback to the power grid,the way of DC energy feedback is chosen to reduce the number of energy conversion and improve the energy utilization.PWM rectifier circuit is used in the front load simulation unit of the module to control the size and type of the analog load by controlling the amplitude and phase angle of the input current;phase shifted full bridge circuit is used in the rear energy feedback unit to maintain the stability of the intermediate DC bus voltage and feed the energy back to the input end of the inverter power supply.For load simulation unit,single current loop control is used.Firstly,the mathematical model of single-phase PWM rectifier is established,and the control strategy of PI control + power supply voltage feedforward is analyzed.In order to further eliminate the steady-state error,the port Controlled Hamiltonian with dispatch(PCHD)model of PWM rectifier is established,and the passive control strategy is studied and simulated.For the energy feedback unit,the control strategy of DC voltage outer loop and output current inner loop is adopted.Firstly,the small signal model of phase-shifting full bridge circuit is established,and then the PI controller is designed.In order to suppress the influence of the second harmonic component of the DC bus voltage on the system performance,a notch filter is added to the feedback channel.According to the technical specifications of the whole machine,the parameters of each component of the main circuit are designed,and the selection of components is completed.The control system is designed with DSP as the main chip and CPLD as the auxiliary chip.The software design and debugging of DSP and CPLD are completed according to the control requirements of the main circuit.Finally,the simulation in Matlab / Simulink verifies the feasibility of the design scheme;the experimental research is carried out on the 17 kw electronic load prototype,and the experiments are carried out under various working conditions,such as full load,half load,phase mutation,sudden load increase and load decrease,etc.the key point waveform is analyzed,and the results show that the dynamic and static performance of the electronic load is good.