| High power rectifier has been widely employed in various fields of national economy. However, the strongly nonlinear and time-varying characteristics of the rectifying device makes high power rectifier become the main harmonic source of the grid. Multi-pulse rectifier technique is the main method of high power rectifier for harmonic suppression. The method can effectively suppress the low order harmonics in input current, but has no effect on high order harmonics. In order to further improve the capacity of Multi-pulse rectifier harmonic suppression, this paper combines the Multi-Pulse Rectifier(MPR) technology and harmonic suppression technology at DC link. A shunt 12-pulse rectifier with Boost converter is furthermore researched based on conventional 12-pulse rectifier with wye-connected autotransformer.In order to simulate wye-connected autotransformer in simulation software, A decoupled model of wye-connected autotransformer is built. First, by analyzing the relationship between input, output voltage phasor in wye-connected autotransformer, the winding configuration and turn ratio is obtained. Phase-Coordinate is used to analyze the relationship among branch voltage, branch current, node voltage, node current in the coupling circuit. A node admittance matrix about configuration of winding connection, electrical parameters is derived. Decoupled model of wye-connected autotransformer is obtained. Simulation and experimental results indicates that the 12 pulse rectifier based on wye-connected can be simulated effectively by such model.In order to restrain the input current harmonic of shunt 12 pulse rectifier at DC link, the harmonic suppression mechanism based on ideal 12 pulse rectifier is studied, and the influence of the asymmetry of the input voltage on harmonic suppression is analyzed. The relationship between input current and inductor current of rectifier are calculated by switching function, the inductor current waveform needed is analyzed when the input current is sinusoidal, and a realizable inductor current waveform is given. The input voltage asymmetry factor is introduced. The influence of such factor on three-phase input voltage, autotransformer output voltage is analyzed. The relationship between input voltage asymmetry factor and rectifier input current is obtained. Theoretical analysis indicates the Boost converter can effectively suppress the input current harmonic when the inductor curr ent meet certain requirements, The slight asymmetry of the input voltage has little influence on the harmonic suppression of the rectifier.In order to obtain good steady-state and dynamic characteristics for rectifier, an accurate model for shunt 12 pulse rectifier with Boost converter operating in current programmed mode is obtained. By this model, a design of feedback voltage compensation network is given. Influence of parasitic parameters in the component part is considered. A small signal model of the non-ideal Boost converter is built. The stable operation condition for rectifier operating in current programmed mode is studied. This paper also presents a design method of voltage compensation network. A design for the shunt 12 pulse rectifier with Boos t converter is given. A 2.25 k W prototype is presented. Simulation and experimental results indicates that the system can be characterized by good harmonic suppression performance, fast dynamic response speed, and low cost. |
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