| The performance of relay protection is directly related to the safe operation of power system,so it is necessary to make various performance tests for relay protection device before they are put into operation. In new century, China's power industry enters a period of rapid development, with new type relay protection device widely used in power system, relay protection test technology must update constantly.Power amplifier is an important part of relay protection testing device.It is used to export high-power voltages and currents,and then drive the relay protection equipments. Conventional power amplifiers amplified analog signals directly,and the switches must work in linear area.So the conventional power amplifier has low distortion and large loss.This research discusses current amplification technology in relay protection test and Adopts the combination of switching power supply + switching power amplifier. In order to solve the inherent problem of higher harmonic component in switching power amplifier, this paper puts forward a kind of digital control method based on DSP (TMS320F2812) multi-objective control, it calculates output pulse-width timely and controls output voltage of switching power supply, then generates bipolar wave called SPWM, the SPWM waveform drivers the inverter switches , the current which is collected by CT is adjusted in the form of PI after input into AD model of DSP by regulate circuit, so output current can be controlled by this way.Finally this thesis presents the design of system , implementation of the program's control thought of software processes, programs of the simulation and experimental validation. At last, it summarizes all above and points out paper's strongpoints and shortcomings. |
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