Configuration strategy of modulation waves of cascaded H-bridge photovoltaic grid-connected inverter

Abstract

The invention discloses a configuration strategy of modulation waves of a cascaded H-bridge photovoltaic grid-connected inverter, belongs to a photovoltaic power generation technology in the field ofelectrical engineering, and aims to solve a problem that a system cannot normally operate due to serious power imbalance of transmission power between single-phase cascaded H-bridge photovoltaic grid-connected inverter modules. The method comprises the following steps: enabling a photovoltaic module corresponding to an H-bridge converter to work at a maximum power point; performing matching control on the transmission power of the N H-bridge converters; using a current regulator to control a power grid current; and calculating the modulation degrees of all the H-bridge converters, judging theworking mode of the system, and configuring all the H-bridge modulation waves by adopting different modulation wave calculation methods according to different working modes of the system. Compared with the prior art, by using the strategy of the invention, the linear modulation range of the cascaded H-bridge inverter is further expanded, and the capacity of the cascaded H-bridge inverter for coping with power imbalance is improved.

Description

technical field [0001] The invention belongs to photovoltaic power generation technology in the field of electrical engineering, and in particular relates to a configuration strategy for modulating waves of cascaded H-bridge photovoltaic grid-connected inverters. Background technique [0002] Single-phase cascaded H-bridge (Cascaded H-bridge, CHB) photovoltaic grid-connected inverter has multiple independent DC buses, which is easy to realize maximum power point tracking (Maximum Power Point Tracking, MPPT) It has obvious advantages in low-voltage and low-power household photovoltaic power generation occasions. Its multi-level output voltage can make the switching device work at a lower switching frequency, and the use of a smaller filter can ensure that the harmonic content of the grid current is small. In addition, the modular structure can make the output voltage of the AC side reach the grid voltage level by rationally configuring the number of H-bridge converters, ther...

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Problems solved by technology

[0009] 1. The hybrid modulation strategy can expand the linear modulation range of the H-bridge converter from 1 to 4 / π, but it will increase the fluctuation of the DC bus capacitor voltage of the H-bridge converter and reduce the power generation of the system

[0010] 2. The reactive power compensation strategy can deal with serious power imbalances, but this method will reduce the power factor of the system, and the actual application may be limited

[0011] 3. The third harmonic compensation strategy will not aggravate the fluctuation of the DC bus capacitor voltage of the H-bridge converter and can ensure the unit power factor operation of the system, but this method has a weak ability to deal with power imbalance

[0012] 4. The harmonic compensation strategy retains the advantages of the third harmonic compensation strategy, and further expands the linear modulation range of the H-bridge converter, but in the case of more serious power imbalances (for example, the modulation degree of some H-bridge converters greater than 4 / π), the harmonic compensation strategy will also fail

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