A micro-inverter that eliminates specific harmonics

Abstract

The present invention discloses a micro-inverter for eliminating certain subharmonics. The micro-inverter comprises a direct current (DC) power supply, an input capacitor, a primary-side switch tube, an auxiliary switch tube, an auxiliary diode, an auxiliary capacitor, an isolation transformer, a secondary-side switch tube, an intermediate DC bus capacitor, a first inverter bridge arm, a second inverter bridge arm, and a filter circuit. According to the technical scheme of the invention, an auxiliary circuit composed of an auxiliary switch tube, an auxiliary diode and an auxiliary capacitor is added in the DC transformation link of an inverter. In this way, certain harmonic current-secondary harmonic current on the input side of the DC power supply can be effectively eliminated. Moreover, electrolytic capacitors of large size and low reliability are not adopted. At the same time, a feedback path is supplied to the leakage inductance energy of a transformer.

Description

technical field [0001] The invention relates to a micro-inverter for eliminating specific harmonics, which belongs to isolation and micro-inverters, and uses an added auxiliary circuit to realize the elimination of the second harmonic current at the input side of a DC power supply. Background technique [0002] In new energy and other distributed power generation systems, in order to obtain the high-voltage AC power required by the load, the inverter generally has a front-stage DC converter. For this kind of system, the power pulsation component of twice the output frequency contained in the output power is fed back and transmitted to the DC input side, which causes the second harmonic current component to be introduced into the input current, which affects the service life of the input sources such as batteries and fuel cells, seriously It will affect the stability of the DC input power system. The traditional method uses large electrolytic capacitors to balance the power ...

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Problems solved by technology

Fukushima K, Norigoe I, Shoyama M, et al, "Input current-ripple consideration for the pulse-link DC-AC converter forfuel cells by small series LC circuit", Proceedings of IEEE 24th Annual Applied Power Electronics Conference and Exposition, 2009: 447 -451 proposes a solution by adding an LC series resonant circuit and designing its resonant frequency to twice the output frequency, as shown in the attached figure 1 As shown, the second harmonic current on the DC input side can be effectively eliminated, but the required inductance and capacitance values ​​are relatively large, which seriously reduces the power density of the system and limits the service life of the system

Kwon J, Kim E, Kwon B, Nam K, "High-Efficiency FuelCell Power Conditioning System With Input Current Ripple Reduction", IEEE Transaction on Industry Electronics, 2009, 56(3): 826-834 Harnessing High Frequency of Power Electronic Converters characteristics, control the duty cycle of the main power tube, add a variable duty cycle on the basis of the duty cycle required for voltage conversion, and effectively suppress the second harmonic current at the input side, which will be very effective It is conducive to improving the utilization rate and service life of fuel cells. figure 2 As shown, but the scheme requires high control precision and the control algorithm is complex

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