A Combination Optimization Method of Phase Shift Variables Based on Double Phase Shift Modulation DC Converter

Abstract

The invention discloses a phase-shift variable combination optimization method based on a double-phase-shift modulation DC converter. The method comprises the steps: respectively setting dead zones on upper and lower pipe devices of the same bridge arm of the DC converter; employing a double-phase-shift mode; setting a phase-shift coefficient of a transformer secondary side device relative to a primary side device and a phase-shift coefficient between devices at the same side of a transformer; building a precise power follow model, considering the dead zones and a device conduction voltage drop factor, at the double-phase-shift working mode; and setting the minimum inductive current effective value, so as to optimize a targeted equation for obtaining the optimal variable combination. According to the invention, the precise power follow model, considering the dead zones and the device conduction voltage drop factor, is built, and the optimal variable combination is determined based on a rule of the minimum inductive current effective value. The method can avoid the impact from the dead zones and the device conduction voltage drop on output power, and the results of optimization can be directly used for control. Moreover, there is no need of dead zone compensation, and the method can precisely control the output power and improve the efficiency of the converter.

Description

technical field [0001] The invention relates to a direct current converter, in particular to a method for optimizing combination of phase shifting variables based on a double phase shift modulation direct current converter. Background technique [0002] As a necessary energy buffer link of smart grid energy storage system, energy storage system has been widely used. Energy storage units such as batteries, flywheels, and supercapacitors provide energy buffering through the power interface of bidirectional DC converters to improve power quality and energy utilization. The efficiency optimization of bidirectional DC converter is one of the key technologies of energy storage system. Especially considering the discharge depth of supercapacitors and energy storage batteries, the converter will work in a wide voltage and power range. Considering that the actual working power range is extremely wide, the full-bridge converter works in an extremely wide voltage and power range, res...

AI Technical Summary

Problems solved by technology

Considering that the actual working power range is extremely wide, the full-bridge converter works in an extremely wide voltage and power range, resulting in loss of soft switching characteristics, significant reactive power and circulating current, and reduced power conversion efficiency

[0003] Considering that the traditional phase-shift control has only one control variable, it is impossible to achieve efficiency optimization in the full voltage and power range, so it is necessary to increase the control variable, such as using two phase-shift variables

When using dual phase-shift control, non-ideal factors such as dead zone, device on-state voltage drop, circuit parasitic impedance, RC absorption circuit, and magnetic element air gap must be fully considered.

The experimental measurement found that the actual output power and the distribution of each working mode of the bidirectional full-bridge DC converter based on dual phase-shift modulation are quite different from the theoretical analysis results. Transient-induced phase shift angle drift, energy deadbands, and DC bias issues become more complex with the introduction of new phase shift and PWM variables

At present, the power flow models based on dual-phase-shift modulation are all ideal models, ignoring the device characteristics and switching transient process, resulting in the experimental measurement efficiency of the converter being far lower than the theoretical analysis. Therefore, it is necessary to establish a dual-phase-shift based The power flow model of the modulation strategy must take into account the influence of non-ideal factors, commutation transient process, various converter operating conditions and multiple variable combinations of dual modulation strategies

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