Hybrid cascade multilevel electronic power transformer

Abstract

The invention discloses a hybrid cascade multilevel electronic power transformer. The hybrid cascade multilevel electronic power transformer comprises A, B and C-phase electric energy transformation units with the same structure, wherein each phase electric energy transformation unit is formed by concatenation of M sub-units of the electronic power transformer, and M is not less than 2; each sub-unit of the electronic power transformer comprises a three-stage structure formed by series connection of a high-voltage stage, an isolation stage and a low-voltage stage; each high-voltage stage comprises a PWM (pulse width modulation) rectifier, each PWM rectifier is in concatenation with the PWM rectifiers of other sub-units in the same phase, each isolation stage comprises an isolation type DC-DC (direct current-direct current) converter, each low-voltage stage is of a voltage source inverter, and each voltage source inverter is in concatenation with the voltage source inverters of other sub-units in the same phase; and the alternating current input ends of the PWM rectifiers and the direct current output ends of the voltage source inverters are respectively connected with reactors in series. The hybrid cascade multilevel electronic power transformer disclosed by the invention can be used for improving the quality of electric energy by expanding the level number of output voltage; and furthermore, a used switching device does not need to be limited by the same frequency, thereby reducing the loss of a switch and a filter.

Description

technical field [0001] The invention relates to the application of power electronics technology in power systems, in particular to a hybrid cascaded multilevel electronic power transformer. Background technique [0002] Electronic power transformer is a kind of electric energy conversion and transmission equipment that adopts power electronic conversion technology, and it is a new type of power transformer. So far, domestic and foreign researchers have proposed a variety of specific implementation schemes. Such as: Holger Wrede, Volker Staudt, Andreas Steimel. Design of an Electronic Power Transformer. IEEE 200228th Annual Conference of the IECON. Scott D. Sudhoff, Steven F. Glover, Dudley. Galloway. Application of Power Electronics to the Distribution Transformer. Applied Power Electronics Conference and Exposition, 2000. And invention patent ZL 02139030.4. These solutions have their own advantages, but they all have a problem, that is, the bus voltages of all power conv...

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Problems solved by technology

These solutions have their own advantages, but they all have a problem, that is, the bus voltage of all power conversion subunits in the device is the same

In this way, the number of levels of the output voltage is limited, which does not help to suppress the harmonics of the output voltage; and the switching frequency of the switching device is also the same, which also limits the optional switching devices; therefore, in suppressing harmonics and improving power factor There is no advantage in reducing filter capacity and volume and reducing losses

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