Research On VIENNA Rectifier With Double Ramp Comparison SPWM Control Strategy

Three-phase PWM rectifiers are widely used in aerospace, automotive electronics, communication system in recent years. As a result, it is developing towards high power density, high reliability, high power factor. Compared with traditional topology, three-phase three-level three-switch PWM rectifier, i.e. VIENNA rectifier is a research hotspot due to its merits such as high power density, no short circuit possibility, low voltage stress of power device, low harmonic of input current. VIENNA rectifier with DRC-SPWM control strategy is researched in order to improve the power density of three-phae PWM rectifier and meet the needs of small volume in medium and large power occasion.Firstly, the operational modal of VIENNA rectifier in the second sector is analyzed and the equivalent circuit is proposed. On this basis, the switching function is introduced, and the average model and small-signal linearized model of VIENNA rectifier in abc natural coordinate are established. As a consequence, the relationship between input current, output voltage, dc-link neutral point voltage and the controlled duty cycle is obtained. The product model of power device is chosen according to the parameters of the convertor, and the design procedure of input inductor and output capacitor are detailed introduced. Afterwards, the schematics of driving circuit, sampling circuit and power supply circuit of DSP is designed. The working principle of double ramp comparison sinusoidal PWM, i.e. DRC-SPWM is elaborated. In summary, the control strategy block diagram of VIENNA rectifier is proposed, and the current loop and voltage loop transfer function is deduced. Based on the bode diagram of controller, the crossover frequency and phase margin of the system are obtained. As a result, the rationality of the con trol loop is verified. The z domain control diagram is obtained according to the discretization of continuous control system. Afterwards, the program flow chart is proposed so as to introduce programming procedure.On the basis of theory analysis and controller design, the convertor is simulated using MATLAB/SIMULINK and PLCSE. A prototype is established to verify the ability of harmonic suppression, ripple of output voltage, the voltage balance of output capacitors and the stability of controller. Experimental results show that the VIENNA rectifier and the control system are feasible and effective.