Simplified Inverter Space Vector Modulation Algorithm Of Five Electricity

The traditional space vector pulse modulation algorithm is based on α-β coordinate system. In this coordinate system, the coordinate of voltage vectorcontains floating point numbers, and the rules of reference voltage vectorpositing are very complex. Besides this is an inefficient algorithm. Because itwill involves a large number of operation of trigonometric functions, whencalculating the holding time of synthetic vectors. With the increase of the levelnumber n, the number of basic vector and phase voltage combinations increasein a quadratic and cubic growth rate. Because of a lot of redundant vector, themodulation algorithm becomes extremely complex. Therefore, the traditionalspace vector pulse width modulation algorithm can not apply to the inverterwhose levels are greater than3.In this paper, we simplify the space vector pulse width modulationalgorithm by introducing g-h coordinate system. In the new coordinate system,we redefine the voltage vector, and establish a mapping between the voltagevectors in two kind coordinate systems, and deduce the coordinatetransformation matrix. In g-h coordinates, the coordinate value of thefundamental voltage vector are integers, reference vector positioning rules aresimple and are not sensitive to the number of levels. It becomes easier tocalculate holding time of synthetic vectors.There is still a large amount of calculation in the space vector pulsewidth modulation algorithm based on g-h coordinate system, when calculatingthe switch state of synthetic vectors. In order to solve this problem, this paperproposes an optimization algorithm. In this algorithm we design switch state ofthe reference voltage rang from0to π/3, then we can obtain the switch state ofthe whole rang of reference voltage by using the method of alternating phasesequence and inversion. This algorithm not only improves the efficiency of itsprogram, but also enhances the sinusoidal symmetry of the output.In order to verify the correctness and effectiveness of the algorithm, webuild a five-level inverter simulation model based on MATLAB tool, and conduct simulation experiments for several times. The simulation resultsindicate that: space vector modulation method has higher DC voltage utilizationratio than triangular carrier modulation method; phase sequence of alternatingnormalization method can improve the efficiency of the algorithm and improvethe harmonic performance of the inverter. The harmonic components of outputvoltage are effectively suppressed.Finally, a cased five-level invert is made, which uses DSP+CPLD ascontroller and uses MOSFET as switch. In this inverter, we have successfullyapplied the five-level space vector modulation algorithm.