A single-phase power electronic transformer DC bus voltage equalization control method

Abstract

The invention discloses a voltage-sharing controlling method for a direct current bus voltage of a single-phase power electronic transformer. A power main circuit of a single-phase DC-AC power electronic transformer is composed of an isolation level and an inversion level. The isolation level comprises high frequency isolation type DC-DC convertors. The inversion level comprises DC-AC inverters. The input ends of all the DC-DC convertors of the isolation level are in series connection with a medium voltage or high voltage direct current voltage source. The output ends of the DC-DC convertors are connected with the direct current input ends of the corresponding DC-AC inverters of the inversion level. The alternating current sides of all the DC-AC inverters of the inversion level are in series connection with an output filter. The controlling method comprises the following steps: firstly, the voltage-sharing control is carried out on bus voltages of the direct current source side of the power electronic transformer; secondly, the voltage-sharing control is carried out on bus voltages of the output side of the isolation level of the power electronic transformer. According to the controlling method, the voltage-sharing control among cascading modules of the cascading type single-phase power electronic transformer can be achieved, and the method is simple. The correctness and the reliability of the method are verified through simulation results, and a good reference value is provided for the engineering application.

Description

Technical field: [0001] The invention relates to the application of power electronics technology in power systems, in particular to a voltage equalization control method for DC bus bars of single-phase power electronic transformers. Background technique: [0002] Traditional power transformers are simple in structure, high in efficiency and high in reliability, and are widely used in power systems. However, the low operating frequency makes the traditional transformer bulky and heavy, and the use of mineral oil, epoxy resin, and flame retardant oil as insulation or cooling medium has potential hidden dangers of fire and environmental pollution. In addition, it can usually only achieve relatively single functions such as electrical isolation, voltage level conversion, and bidirectional power transfer, but has no functions such as grid-side power quality adjustment, harmonic transfer isolation, overload and fault protection, and load voltage regulation. These weaknesses of tr...

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Problems solved by technology

[0004] The purpose of the present invention is to provide a DC bus voltage equalization control method for single-phase power electronic transformers to solve the problem of unbalanced DC bus voltage in the existing cascaded modules

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