Research On Control Strategy For High Power Factor VIENNA Rectifier

Prevailing of power electronics brings convenience to energy conversion and utilization on one hand and also causes harmonics and reactive power problems on the other hand. Therefore the study on green and clean PWM rectifier with high power factor and low input current distortion has become an important issue for the technology of power electronics application. VIENNA rectifier, i.e. three-level three-switch boost rectifier is prevailing due to its merits such as high power factor , low Total Harmonic Distortion (THD) of input current, few switch devices, low switch stress and high reliability. And research on the controlling of VIENNA rectifier has important theory significance and engineering merit.First, an improved Disposition Opposition Double Ramp Comparison Control (PDDRCC) method is proposed for the control of VIENNA rectifier. This modulation method effectively solves the problem of output voltage is not controllable with light load and no-load by the introduction of feedback mechanism to it. With state space method mathematic models of the rectifier are established on static coordinate system, two-phase static coordinate system and two-phase rotating coordinate system respectively. Analysis of Phase Disposition Double Ramp Comparison Control (PDDRCC) and PODRCC methods show that PODRCC method is easier to achieve and attains higher reliability. This is the foundation of the following researches.Second, an Enhanced Phase Locked Loop (EPLL) control strategy based on improved Adaptive Notch Filtering (ANF) is proposed, controller parameters are optimized using BF-PSO algorithm. In this method, particle swarm optimization (PSO) algorithm is introduced to Bacterial Foraging (BF) optimization algorithm as a mutation operator to enhance the global searching ability of optimization algorithm, obtaining a new BF-PSO hybrid optimization algorithm. On this basis, an improved adaptive notch filter based on BF-PSO hybrid optimization algorithm is given to solve the problem of obtaining synchronization voltage information of single-phase system under larger disturbances and noise. Then the stability of the improved adaptive notch filter is analyzed according to mean theory. Aiming at the input voltage imbalance of traditional three-phase PLL, three-phase EPLL is proposed based on improved ANF. The nonlinear model of EPLL is deduced under the condition of input voltage distortion. Then the stability and tracking ability of the model is analyzed according to Lyapunov's second method.Third, a current decoupling method is proposed based on Fuzzy Logic Proportional Resonant (FLPR), which can improve the tracking characteristics of the input current of VIENNA rectifier. Through the analysis of the current decoupling control method of VIENNA rectifier, it can be obtained that the current control of the rectifier can be decoupled successfully on two-phase static coordinate system. A proportional resonant controller based on internal model theory is used in current tracking control of the rectifier, by which the zero error tracking control of the VIENNA rectifier is realized. In order to improve the robustness and anti-interference ability of the control system a fuzzy regulator is designed, which regulates the parameters of the generalized integral controller real-timely according to system error, and validates the proposed method through simulation.Four, fractional order controller is proposed based on BF-PSO algorithm to improve the DC voltage control precision of VIENNA rectifier. The BF-PSO algorithm is introduced to solve the problem of parameters design fractional order controller. Furthermore, the method is used to control the DC bus voltage of the VIENNA rectifier, with enhanced control accuracy and system stability. Moreover, aiming at the inherent problem of capacitor neutral-point voltage fluctuation in three-phase converters, a neutral-point potential controller is designed based on BF-PSO amplitude limit factor, which can attain the balance adjustment of the neutral-point potential with high precision and reduce the effect of the adjustment on current THD.At last, a general design scheme is given according to the performance index and functional requirements of VIENNA rectifier. The power unit and control configuration based on DSP2812 is established. Based on this, outer voltage loop, internal current loop and balancing neutral-point potential controller is designed according to the proposed methods and realized. Experimental results show that the performance indexes meet the design requirements and the proposed control strategy is viable and efficiency.