H-bridge modular unit series combination single-phase high-voltage transformer and multi-level control method

Abstract

The invention provides an H-bridge modular unit series combination single-phase high-voltage transformer and a multi-level control method. The transformer comprises 2N H-bridge modular units and four bridge leg inductors, each H-bridge modular unit comprises four power switch elements with flyback diodes and a direct-current capacitor, the anode and cathode of the two power switch elements in the power switch unit of each phase are sequentially connected in series, and the series midpoint and the cathode are the output end. The anodes of the upper power switch elements of the power switch units of the two phases are connected, the power switch unit of one phase is chosen to be connected in parallel with the direct-current capacitor, wherein the anode of the upper power switch element is connected with the anode of the direct-current capacitor, and the cathode of the lower power switch unit is connected with the cathode of the direct-current capacitor. The bridge legs with the direct-current capacitors in the transformer can output 0, plus or minus E, plus or minus 2E, ellipsis, plus or minus NE levels, and the bridge legs without the direct-current capacitors can output 0 and plus or minus NE levels; by adopting the multi-level control method, single-phase alternating-current output voltage can present sinusoidal multi-level voltage, and harmonic waves are reduced.

Description

technical field [0001] The invention belongs to the field of power electronic converters or high-voltage applications, and relates to a single-phase high-voltage converter combined in series with H-bridge module units and a multi-level control method. Background technique [0002] Single-phase high-voltage converters are widely used in many industrial occasions. In recent decades, in-depth research on single-phase high-voltage converters has been carried out internationally, and many meaningful high-voltage topologies have been proposed. The main technologies for constructing topology include: 1. Direct series connection technology of power switching devices. Its advantage is that it can directly apply the existing topology. Consistency requirements are high, and device failures are prone to occur; 2. Multiple technology, its advantage is to achieve high voltage and low harmonic output through the coupling of multi-winding power frequency transformers, the disadvantage is th...

AI Technical Summary

Problems solved by technology

The main technologies for constructing topology include: 1. Direct series connection technology of power switching devices. Its advantage is that it can directly apply the existing topology. Consistency requirements are high, and device failures are prone to occur; 2. Multiple technology, its advantage is to achieve high voltage and low harmonic output through the coupling of multi-winding power frequency transformers, the disadvantage is that power frequency multi-winding transformers are required, cost, loss , Increased complexity, and DC magnetization phenomenon; 3. Multi-level technology, its advantage is that the DC side adopts series DC capacitors to realize voltage equalization of power switching devices, but the disadvantage is that the conduction current load of power switching devices is inconsistent, causing each DC capacitor The upper DC voltage is unbalanced, and the topology is more complex; 4. The module combined multi-level converter, that is, the MMC converter, has the advantage that it is composed of multiple identical modular power units and two bridge arm inductors in series, realizing In addition to high modularity, it has more obvious advantages than general multi-level technology in terms of device current stress, unbalanced operation, and fault protection. It is currently the preferred converter for high-voltage power conversion.

[0003] In addition, general single-phase high-voltage converters cannot achieve multi-level control well, and usually use PWM control, which requires power devices to work at high frequencies and has large switching losses

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