A control method for automatic optimization of charging and discharging circuits in hybrid inverters

Abstract

The invention discloses a control method for automatic optimization of a charge-discharge circuit in a hybrid inverter. Through the constant-voltage closed-loop control of the inverter circuit and the constant-current closed-loop control of the Buck / Boost converter, the bidirectional LLC resonant circuit works at the same time. In the reverse mode, the extreme value gain of the LLC circuit driving frequency search circuit is disturbed, and the output power is disturbed to find multiple extreme values, and the optimal frequency operating point of the charging and discharging circuit in the hybrid inverter is comprehensively determined. Based on the gain characteristics of the LLC circuit and combined with several control steps, the present invention can quickly and accurately determine the resonance frequency of the system, and can make the charging and discharging circuit work at the optimal frequency point, which can not only improve the efficiency of the circuit and reduce EMI interference, but also the frequency The gain of the point is fixed, which can simplify the circuit design process. No precise reference voltage source and additional wiring are required during the calibration process, and the resonant frequency correction procedure can be started during normal use of the device.

Description

technical field [0001] The invention relates to the technical field of power electronics application technology, in particular to a control method for automatic optimization of a charging and discharging circuit in a hybrid inverter. Background technique [0002] With the development of distributed energy resources, household hybrid inverters that include energy storage units and are based on self-generation and self-use modes are more and more widely used. The DC connection end of this inverter includes a photovoltaic array input port, a low-voltage (usually 48V and below) battery port, and the AC connection end includes a mains port and an off-grid emergency power output port. In order to output an AC voltage close to the mains voltage, the DC bus voltage is usually 8 to 10 times the battery voltage. The conventional bidirectional Buck / Boost circuit cannot efficiently and economically achieve the required boost ratio, so it is necessary to add a high The frequency transfo...

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Problems solved by technology

However, it is usually difficult to maintain the manufacturing accuracy of the capacitance and transformer leakage inductance that make up the resonant circuit, which will cause the deviation of the resonant frequency, especially when the capacitance and transformer leakage inductance are both in positive or negative deviations. The frequency operating point set by mass-produced hybrid inverters is usually fixed at the theoretical design value, which makes it difficult to ensure that all inverters operate at the optimal frequency point, and the manual calibration method is obviously unrealistic due to low efficiency , it is necessary to find a method to automatically find the optimal operating frequency point in this hybrid inverter

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