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Control Of Boost Three-Level Chopper And Three-Level Diode Clamped Inverter In PMSG Based Direct-driven WECS

Posted on:2011-05-08Degree:DoctorType:Dissertation
Country:ChinaCandidate:X GuFull Text:PDF
GTID:1102330338989095Subject:Motor and electrical appliances
Abstract/Summary:PDF Full Text Request
This paper discusses the significance and development prospect of wind energy and wind power generation under the increasingly serious situation of energy security. A novel topology of power converter which is applied to direct driven wind energy conversion systems (WECSs) based permenant magnetic synchronous generators (PMSGs) is proposed to meet the demand of large capacity WECSs. The stator of generator is connected to a diode rectifier, a diode-clamped three level (TL) inverter is connected to the grid, and a boost TL chopper is set between the rectifier and the TL inverter. Based on this topology, the switch-signal phase-delay control (SSPDC) for the boost TL chopper is put forward to balance the neutrual point (NP) potential of the TL inverter. The NP potential is balanced by adjusting the phased delay betweent the two switching signals of the two power switches in the TL chopper, and the boosting feature of the TL chopper is not changed. The boost TL chopper under the SSPDC is modeled for its controller design.A parallel dual-PI control strategy is designed for the boost TL chopper, as the maximum power point tracking (MPPT) and NP balancing are achieved both by the TL chopper. This strategy is simulated in a typical large capacity WECS, and its feasibility is verified by simulation results. The validity of the proposed NP balancing method is verified furtherly by comparing with two redundant vector selection NP balancing methods which are both simulated in the same WECS. The modulation algorithm of the grid-side TL inverter is simplified a lot as the NP potential is balanced by the boost TL chopper.The main factors on which the operating mode of boost TL choppers depend are ananlyzed for guaranteeing the relationship between the input and output voltage of the TL chopper in the proposed topology. The formulas of critical boosting inductances are deduced according to the critical conditions between different operating modes. The capacitor voltage ripples are also analyzed under different operating modes. The validity of these ananlyses is verified by simulating and experimental results. Furthermore, these ananlyses could be generally used in guiding the design of boost TL choppers.In addition, the PI parameters tuning method for the controllers of the grid-side TL inverter is simplified according to the principle of internal model control (IMC). The ananlysis indicated that the tuning method is generally applicable when controlled plants could be regarded as first-order systems.
Keywords/Search Tags:wind power generation, permenant magnetic synchronous generator, boost three level chopper, diode-clamped three level inverter, switch-signal phase delay control, maximum power point tracking
PDF Full Text Request
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