H bridge cascade active electric filter DC side capacitance-voltage equalizing controlling method

Abstract

This invention relates to a method for uniformly controlling capacity and voltage at the DC side of a bridge-H cascade active power filter, which first of all takes a harmonic current, a reactive current needed to be compensated by a power net and a load as a compensation current desired by the active power filter, takes the sum of the desired compensation current and a fundamental wave positive sequence active current absorbed from the power net as a reference current of the active power filter to obtain a desired output voltage of the active power filter through a current tracking controller so as to output a current by the active power filter for tracking the reference current; calculates a micro-tune volume of the output voltage of the bridge-H cascade unit through a capacity and voltage balance controller based on a capacity and voltage deviation of the bridge-H cascade unit and the output current of the active power filter, carries out micro-micro adjustment to the desired output voltage to adjust a charge and discharge time of an unit flying capacitor; takes the micro-adjusted desired output voltage as the reference voltage of the unit, after a pulse width modulation to obtain a trigger signal of the output voltage of the bridge-H cascade power device and drive the power device.

Description

technical field [0001] The invention relates to an H-bridge cascaded active power filter DC side capacitor voltage equalization control method. Background technique [0002] With the development of power electronics technology, various nonlinear power electronic devices have been widely used in power systems, industries (especially metallurgy, steel, chemical industry, etc.), transportation, building automation and households, and their device capacity is increasing The large and diversified control methods make the voltage and current waveform distortion in the power grid more and more serious, and the harmonic pollution in the power grid is becoming more and more serious. In order to overcome the shortcomings of passive power filter (PPF), an important trend of harmonic suppression devices is to use active power filter (APF) to meet the harmonic standards IEEE519-1992, GB / T14549-93 "Power Quality Public Grid Harmonics" requirements. Compared with PPF, APF has the follow...

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Problems solved by technology

[0012] Chinese patent 200310115393.2 and Chinese patent 03142679.4 both balance and control the DC side capacitor voltage of H-bridge cascaded multilevel inverters, both of which are controlled by an additional external The equipment enables the active power exchange between the H-bridge inverters to realize the balanced control of the capacitor voltage. This type of method requires additional equipment and its control, which increases investment and maintenance costs.

For APF, its compensation current is a harmonic current, which requires a high switching frequency, a large change in the pulse width of each H-bridge, and requires rapid capacitor voltage balance. The need for harmonic governance

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