Three-phase multi-split transformer-based CHB (Cascaded H-Bridged) cascade photovoltaic inverter circuit

Abstract

The invention relates to a three-phase multi-split transformer-based CHB (Cascaded H-Bridged) cascade photovoltaic inverter circuit without changing a ground insulation voltage of the existing photovoltaic system device. Outputs of a high-power CHB cascade multi-level photovoltaic inverter are connected in series through magnetic coupling, and the high-power CHB cascade multi-level photovoltaic inverter can be safely and reliably operated in a photovoltaic power station. A low-voltage side winding is connected with a plurality of independent equipower inversion outputs, and the mode of using one split transformer is more economic, smaller in occupation and more convenient in maintenance and management compared with the mode of using a plurality of common transformers. According to the invention, flow resistance value of key devices is reduced, and IGBTs (Insulated Gate Bipolar Translators) are prevented from being connected in parallel.

Description

technical field [0001] The invention relates to a CHB cascaded photovoltaic inverter circuit, in particular to a CHB cascaded photovoltaic inverter circuit based on a three-phase multi-split transformer. Background technique [0002] At present, most inverter devices operating in high-power photovoltaic power plants adopt a two-level three-phase half-bridge inverter topology, and the output is connected to an isolation transformer circuit structure. The two-level three-phase half-bridge inverter topology is simple and easy to control, but it has the following disadvantages: 1. The harmonic content of the two-level output is high, and LC or LCL filters are required, which increases the volume and weight of the inverter device. The efficiency is lower than the multi-level inverter, and the phenomenon of LC resonance will appear. 2. High-power photovoltaic modules occupy a large area and are controlled by one MPPT. The mismatch of power supply of modules has a great impact on ...

AI Technical Summary

Problems solved by technology

The two-level three-phase half-bridge inverter topology is simple and easy to control, but it has the following disadvantages: 1. The harmonic content of the two-level output is high, and LC or LCL filters are required, which increases the volume and weight of the inverter device. The efficiency is lower than that of the multi-level inverter, and the phenomenon of LC resonance will appear

2. High-power photovoltaic modules occupy a large area and are controlled by one MPPT. The mismatch of power supply of modules has a great impact on the power generation efficiency of the system

4. After the insulation voltage of solar modules is increased, the withstand voltage value of key components IGBT and bus capacitors will increase accordingly, resulting in a significant increase in cost

The main limitation of photovoltaic inverters using CHB cascaded multi-level topology in power stations is that the insulation voltage of solar modules, cables, vacuum switches and other devices to ground is 1000V, which cannot meet the requirements of CHB cascaded multi-level Application conditions of photovoltaic inverter input high voltage

Significantly improving the insulation level of the system requires high costs and a long R&D and production cycle

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