Pulse width modulation method for maximum boost and minimum switching frequency of diode-assistant buck-boost inverter

Abstract

The invention discloses a pulse width modulation method for maximum boost and minimum switching frequency of a diode-assistant buck-boost inverter. The pulse width modulation method comprises the following steps of: controlling a voltage average value of an intermediate DC side within a switching period (T<s>) to an instantaneous maximum value of an envelope line of three-phase AC output phase voltage, namely line voltage, and thus, the equivalent switching frequency of a power semiconductor device in an inverter bridge can be reduced to 1 / 3f<s> (f<s> is equal to 1 / T<s>). By the method, the voltage gain of the diode-assistant buck-boost inverter is further increased, the voltage stress and the switching loss of a switching device are reduced, and the power conversion efficiency of a converter is improved. Moreover, with the adoption of the modulation method disclosed by the invention, the inductance current and the capacitance voltage of the DC side of the inverter contain low-frequency ripple wave which is six times of fundamental frequency. By the modulation method, the diode-assistant buck-boost inverter is simultaneously applicable for distributed power supply systems such as 400-800Hz middle-frequency airborne and boat.

Description

【Technical field】 [0001] The invention belongs to the field of distributed power generation such as new energy photovoltaics and fuel cells, and specifically relates to a control method for high-gain, high-efficiency power conversion of a buck-boost inverter, especially a type of diode-assisted buck-boost inverter with maximum boost and minimum voltage. switching frequency pulse width modulation method. 【Background technique】 [0002] In new energy power generation, photovoltaics and fuel cells have broad application prospects. However, their obvious feature is that the DC power supply voltage is low, the voltage varies in a wide range, and the drop is obvious. Therefore, power electronic converters must be used to adjust the voltage amplitude and frequency to obtain relatively high AC power required by the grid or electrical equipment. The peak value of the output AC voltage of the traditional three-phase voltage source inverter is less than half of the input DC power sup...

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Problems solved by technology

Typical pulse width modulation strategies have the disadvantage of low DC voltage utilization. The existing literature [2] "Y. Zhang, J. J. Liu, and C. Y. Zhang, "Improved pulse-width modulation strategies for diode-assisted buck-boost voltage source inverter", IEEE Trans. PowerElectron., vol .28, no.8, pp.3675–3688, Aug.2013." An improved pulse width modulation strategy was proposed to improve the utilization rate of DC voltage and reduce the voltage stress of switching devices

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