Multi-level converter specific harmonic elimination pulse width modulation fast implementation method
A specific harmonic elimination and pulse width modulation technology, which is applied in the direction of converting AC power input to DC power output, electrical components, output power conversion devices, etc., can solve the problem of unsatisfactory curve fitting effect and memory space of look-up table method Large size, large single-chip memory requirements, etc., to achieve the effect of ensuring rapidity, avoiding data storage, and improving accuracy
Inactive Publication Date: 2018-10-16
TIANJIN UNIV
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However, the memory space occupied by the look-up table method is huge, which requires a lot of memory in the single-chip microcomputer, and at the same time, the flexibility is not high; and for the case of unequal voltage and multi-level, the trajectory of the switching angle with respect to the modulation ratio presents a non-continuous nonlinear characteristic , the effect of curve fitting is not ideal
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[0019] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.
[0020] The present invention provides a specific embodiment of a rapid realization method of a unequal voltage multilevel inverter SHEPWM, so as to understand the present invention. Taking the number of unequal voltage sources as 3, namely E1, E2, and E3 as an example, the SHE equations are solved offline by using the PHC software package of MATLAB, and the online fast solution is realized by neural network and quasi-Newton algorithm.
[0021] Step S1 as figure 1 Shown is a schematic diagram of a quarter-cycle symmetrical unequal voltage seven-level output waveform. According to Fourier series theory, the voltage waveform can be expanded into the following sinusoidal series:
[0022]
[0023] Then the amplitude bn of the nth harmonic can be expressed as follows:
[0024]
[0025] Among them, E1=V dc e1, E2 = V dc · e2, E3 = V dc · e3...
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The invention relates to a multi-level converter specific harmonic elimination pulse width modulation fast implementation method. The method comprises the steps of establishing non-equal-voltage multi-level converter specific harmonic elimination equation sets; performing off-line traversal to solve the non-equal-voltage multi-level converter specific harmonic elimination equation sets of different modulation ratios through an algebraic method to obtain the modulation ratios and solutions corresponding to the specific harmonic elimination equation sets; establishing a BP neural network, forming a training sample which is composed of the modulation ratios and the solution corresponding to the specific harmonic elimination equation sets, taking the modulation ratios as the input of the neural network, taking the solution corresponding to the specific harmonic elimination equation sets as the output of the neural network, and training the BP neural network; generating an initial value ofthe specific harmonic elimination equation sets in an online manner; and performing online iteration on the initial value of the specific harmonic elimination equation sets in the step 4 by adopting anumerical iteration algorithm, so as to obtain a specific harmonic elimination equation set accurate solution
Description
technical field [0001] The invention belongs to the field of power electronic system modulation method and related control, and in particular relates to a method for quickly realizing pulse width modulation for specific harmonic elimination of a multilevel converter. Background technique [0002] In recent years, medium and high-power multilevel inverters have been widely used in motor drive, harmonic compensation, uninterruptible power supply, and AC flexible due to their advantages of large output capacity, high output voltage quality, and low current harmonic content. power transmission system etc. In these applications, the switching frequency will be limited by factors such as switching loss, heat dissipation, and electromagnetic interference, so that the switching frequency is usually relatively low, generally only a few hundred Hz. At low switching frequencies, the traditional sinusoidal pulse width modulation (Sinusoidal Pulse Width Modulation) , referred to as SPWM...
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IPC IPC(8): H02M7/483H02M7/5387H02M1/12
CPCH02M1/12H02M7/483H02M7/5387
Inventor 张国山郝君
Owner TIANJIN UNIV