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Research On The Control Strategy Of Three-Level PWM Rectifier

Posted on:2011-01-04Degree:MasterType:Thesis
Country:ChinaCandidate:B DuanFull Text:PDF
GTID:2132360305469789Subject:Power electronics and electric drive
Abstract/Summary:PDF Full Text Request
Diode-clamped three-level PWM rectifier has been widely used in middle and high voltage AC drivers, wind power generation and reactive power compensation for some reasons, such as its little voltage stress afford by power devices, low harmonic components in input current, perfect sinusoidal, alterable power-factor and bidirectional power flow.First of all, the theory of the three-level PWM rectifier was introduced in details, which were about the topology and working principles, in other words, constructing the high and low-frequency mathematical models under ABC stationary reference frame, aβstationary reference frame and dq rotation reference frame, and the three-level rectifier mathematical model was analyzed while considering the neutral point voltage unbalance. Through its mathematical model's establishment and analysis, several kinds of control strategies have been verified.The symmetrical three-section PWM without medium vectors was proposed according to the mathematical model of three-level pulse width modulation (PWM) rectifier and equivalent circuit topology of space voltage vector, and the influence of various vectors on neutral-point (NP) voltage in direct current (DC) side was analyzed. The results of simulation and experiment show that three-level PWM rectifier runs steadily in unity power factor, the proposed method is correct and efficient. Compared with traditional PWM, while the amplitude of line current changes rapidly, the effect of neutral-point voltage being balanced is still excellent. While, by analyzing four-quadrant mirror space voltage vector pulse width modulation algorithm. A new strategy based on Vαm,Vβm is derived. The algorithm is simple, including addition, subtraction, multiplication and other simple operations. The algorithm is help to achieve DSP programming.The structure of DSP+CPLD based on logical method is proposed in order to effectively achieve the modulation strategy of Symmetric three-section. Also, the thinking of achieving the logical method is given. The experimental results show that the algorithm is simple, correct and occupy the fewer logic units of the CPLD chip. At last, the experiment system based on congratulation DSP+CPLD had been built in which the core controller is DSP (TMS320LF2407A)and related research is accomplished.
Keywords/Search Tags:Three-level Rectifier, Symmetrical Three-Section, SVPWM, Neutral-point balance control, Medium space vector, DSP+CPLD
PDF Full Text Request
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