The Research Of A High Frequency High Voltage Pulse Power Supply For Cable Fault Detection

The operating performance of the power cables directly related to the safe and stable operation of the power system. When cable faults occur, it is urgent to use the cable tester to locate the exact fault point rapidly, avoiding serious economic losses. High-voltage pulse power supply, as the main part of the cable tester, is responsible for producing a certain energy high-voltage pulse at the end of the faulted cable and determining the exact fault point. However, the existing widely-used high-voltage pulse power supplies have the following shortcomings:bulky, low-efficiency, inconvenient to carry and transport. Therefore, the main work of this paper is to develop a small-size, light-weight, high-efficiency High Frequency High Voltage (HFHV) pulse power supply which is applied in power cable fault detection. The specifications of the HFHV pulse power supply are as follows:rated operating voltage:35kV±3%, rated operating current:100mA, maximum discharge energy:2450J.This paper first analyses the working process of the LCC resonant converter, conducts the steady-state modeling and small-signal modeling. Then the corresponding relationship between loads and the duty cycle/frequency is obtained through different graphs, though which the parameters of the LCC resonant converter are derived, thereby laying a theoretical foundation for soft-switching of the HFHV generator. On the basis of this, the main circuits of the HFHV pulse power supply are described, focusing on hardware design and parameter selection of the high-frequency converter, drive circuit, HFHV transformer, voltage doubler rectifier circuit and charge-discharge circuit. What’s more, through modeling of HFHV transformer, its distribution parameters are utilized to achieve resonance. After that, the paper presents the control circuit based on dsPIC33F to realize digital and integrated control. The main function includes the PWM waveform generation; Real-time sampling and fault protection for primary and secondary voltage and current of the HFHV transformer; PI controlling of the output voltage and achieving soft-switching when load changes. As to the software, this paper devises the assembler based on dsPIC33F processor, the main flow chart and the configuration for registers of each control module are given, the programming ideas are also presented. Finally, after debugging and a series of experiments of the whole power supply, we get the key experimental waveforms and analyze them at length. Then the paper summarizes the merits and demerits of the power supply which presented in this paper and indicates the further improvement and development combined with the newly developed insulation test for the power cable.The paper has achieved the digital and integrated control of the whole power supply based on dsPIC33F, completing the design and debug of the entire HFHV pulse power supply. Experiments results show that the powe supply designed in this paper can be applied in cable fault fetection.