| Because the electric power system harmonics have badly been polluting the electric environment, all nations are rather concerned about the harmonics and enter the research of harmonics actively. The electric power system harmonics simulator rig is one of the basic tools which are used to study harmonics. Therefore, it is very important to design a set of electric power system harmonics simulator rig.This dissertation introduces harmonics' notion, characteristics and harm in detail, illuminates the significance of studying the electric power system harmonics simulator rig.The deferent voltage virtual value range of the electric power system harmonics simulator rig is 0～100V and deferent current virtual value range is 0～3A , which accord with the PT. The electric power system harmonics simulator rig is required to be of high power, high efficiency and little waveform distortion. Compared with other current power amplifiers, the switching power amplifier is chosen. In course of the development of the switching power amplifier, it is mainly applied to the audio field, and rarely in the high-power and high voltage fields. The switching power amplifier can endure high power, high voltage and high current, and has the advantages of little waveform distortion, digital control, free waveform generating, high power, little bulk, light weight, etc. These characteristics can satisfy the needs of the electric power harmonics simulator rig.In this dissertation, all kinds of power amplifier are analyzed and compared, and the switching power amplifier' operating principle is mainly analyzed which is for the use of the electric power system harmonics simulator rig. Because the electric power system harmonics which are in the 50Hz～31×50Hz range are mainly studied, the electric power system harmonics simulator rig may adopt the SPWM control mode. By the analysis of the influence of carrier ratio dn and modulation wave' starting point on the output voltage, and the influence of the dead-band time on the amplitude, phase and waveform distortion of the output voltage, the modulation scheme has the theoretic base and is decided.The PWM wave from the switching power amplifier needs to be demodulated by a filter to eliminate higher harmonics and avoid distortion. This dissertation analyzes the characteristics of single stage LC filter, two-stage LC filter, and resonance filter respectively. Because it needs to filter the harmonics whose frequencies are in the neighborhood of the switch frequency and the low order harmonics which are produced by dead-band time, these harmonics' frequencies should exceed the highest order harmonics' frequency in the electric power harmonics. By comprehensive consideration, the single stage LC filter is selected and the theoretic base is confirmed that the resonance frequencyω0 must exceed the highest order harmonics' frequency in the electric power harmonics. The control circuit is required to be simple, robust and easily controlled. The dissertation introduces the TMS320LF2407, which is the control core of the electric power harmonics simulator rig with powerful operating ability and abundant interior resources. If it is used in the electric power harmonics simulator rig, it can realize digital control .By analyzing the errors between the natural sampling method and the regular sampling method, it is proven that the TMS320LF2407 with 30MIPS can produce very high carrier frequency, and the errors between the natural sampling method and the regular sampling method may be ignorable. So it can provide the DIP-IPM PS21245 which is used as the dc-to-ac inverter with exact SPWM waves. Closed loop feedback adopts PID control rule to insure the stabilization of magnification times.By analyzing the results gained by emulation experiment and the actual device experiment, the design scheme is proven to be valid and feasible.
|
PDF Full Text Request