Research On High Power Constant Current AC Power Supply System For The Test Of The Low Voltage Electrical Apparatus

In the low voltage electrical equipment industry,the conclusion of the type tests of low voltage electrical apparatus is an important basis for the Identification of the performance of low voltage electrical apparatus.At present,the domestic small power high precision constant current source products have been mature,and high power,high current AC constant current source are relatively few,and taking into account the high performance and high power constant current source procurement need to spend huge cost of procurement,and due to the low pressure testing industry related national standards constantly updated,the design of constant current source in the hardware and software also need to be updated,and there will be late maintenance inconvenience,so the independent research and development of low noise,modular,high precision,Intelligent High-power AC constant current source system is also the trend.According to the relevant technical requirements of low-voltage electrical testing part type test,to study the existing high-power AC constant current source based,designed based on LPC1768 microprocessor high power constant current AC power supply system,given the specific hardware and software,control strategy design and system performance debugging results.The main contents are as follows:This paper introduces the basic working principle of high power AC constant current source,and its application in the detection of low-voltage electrical industry,analyzes the overall circuit structure of high power AC constant current source,focusing on the three-phase sampling LC filter controlled rectifier circuit,to maintain the stability of the DC bus voltage,single phase LCL filter the full bridge circuit is used to control the output current can be adjusted,and the drive circuit,communication circuit design process.Through the constant current control of high power AC constant current source as the research object,analysis of the output waveform control strategy on the driving waveform of SPWM full bridge inverter circuit and producing mechanism of AC power supply system,and the fuzzy PID controller was designed to establish the system simulation model using MATLAB and Simulink simulation software,and the results are compared with the traditional PID control,to verify the feasibility of the control scheme.In view of the characteristics of high power constant current power supply for low voltage detection,the LPC1768 main control circuit,power supply circuit,protection circuit,sampling circuit,phase locked loop circuit,communication and anti-jamming circuit are designed.In high power AC constant current source hardware based,complete system design and compilation of control software,including the main program,control buttons and display subroutine,current signal sampling / feedback procedure,SPWM wave control subroutine,man-machine interface display / control design.Finally,through the AC constant current source for low-voltage electrical test of temperature rise test and thermal cycling test to test the system,with different types and specifications of the AC constant current source to build several types of test platform,using rigid closed Rogowski coil current sensor to measure the current value and the external GEN2 i data acquisition recorder to capture transient output signal waveform.The test results show that the detection of low voltage electrical AC constant current source is stable,high precision,can effectively realize the parallel control,output parameters meet the design requirements,to further verify the rationality and validity of the design.