Optimal harmonic distribution SHEPWM switching angle calculation method and system

Abstract

The invention discloses an optimal harmonic distribution SHEPWM switching angle calculation method and system. The method comprises the steps of: S1, determining amplitude expressions of fundamental wave and various sub-controlled harmonics; S2, determining the modulation ratio and the error values of the various sub-controlled harmonics, furthermore, determining the equation of the fundamental wave and the equations of the various sub-controlled harmonics according to the modulation ratio and the error values of the various sub-controlled harmonics, and constructing a nonlinear transcendental equation; and S3, constructing an objective function by using the amplitude expression of the lowest-order uncontrollable harmonic, and searching the solution of the nonlinear transcendental equation through a genetic algorithm, so that a satisfied result is obtained. By means of the optimal harmonic distribution SHEPWM switching angle calculation method and system disclosed by the invention, dependence on initial value determination in the traditional newton iteration method can be overcome; the fussy initial value trial and error process is greatly reduced; the universality of the solving method is improved; furthermore, the uncontrollable high-order harmonic distortion increasing problem in the specific harmonic elimination PWM technology can be overcome; and, on the premise that low-order harmonic elimination satisfies engineering requirements, the amplitude of the high-order harmonic is reduced, so that optimal harmonic distribution of the total THD is reduced.

Description

technical field [0001] The invention relates to the field of inverter control, in particular to a calculation method and system for an optimal harmonic distribution SHEPWM switching angle. Background technique [0002] In order to improve the output power quality of inverters in the field of urban rail regenerative braking energy feedback, and better suppress grid-connected current harmonics, compared with SPWM technology, SHEPWM modulation technology has low switching frequency, no specific low-order harmonics, and output High waveform quality, low switching loss and other characteristics, so the selective harmonic elimination (SHEPWM) technology of power electronic inverters is more and more widely used. [0003] Since the mathematical model of the specific harmonic elimination technology is a set of nonlinear transcendental equations, it is difficult to solve and the solution process is complicated. Traditionally, the Newton iteration method is often used to solve it, and...

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Problems solved by technology

[0024] The technical problem to be solved by the present invention lies in: aiming at the technical problems existing in the prior art, the present invention provides a method that overcomes the dependence on initial value selection of the traditional Newton iterative method, greatly reduces the tedious initial value trial and error process, and improves the generality of the solution method. Adaptability, and can overcome the problem of uncontrollable high-order harmonic distortion increase of specific harmonic elimination PWM technology. When the low-order harmonic elimination meets the engineering requirements, reduce the amplitude of high-order harmonics to reduce the total THD Calculation method and system for optimal harmonic distribution SHEPWM switching angle

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