Photovoltaic off-grid inverter with high conversion efficiency and control method thereof

Abstract

The invention discloses a photovoltaic off-grid inverter with high conversion efficiency. The inverter comprises a lithium battery pack, a direct-current input reverse connection prevention circuit, a direct-current input voltage sampling circuit, a direct-current bus switching current waveform correction circuit, a control unit, a full-bridge framework MOS tube circuit, a high-frequency rectangular pulse wave generation circuit, an output voltage and frequency detection circuit, an alternating-current output filter circuit and an output current detection circuit. The invention further discloses a control method thereof. The inverter is simple in structure, low in cost, high in practicability and high in stability, the conversion efficiency of the inverter is improved through the full-bridge framework MOS tube circuit and the high-frequency rectangular pulse wave generation circuit, meanwhile, the inverter self-loss current in a no-load state can be effectively reduced, the discharge current of a lithium battery pack is reduced under the same load condition, and the service life of the lithium battery pack is prolonged.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a photovoltaic off-grid inverter with high conversion efficiency and a control method thereof. Background technique [0002] Photovoltaic off-grid inverter power supply, because it is far superior to high-frequency inverters in load compatibility, it is very good in load compatibility, and has been widely used in various power supply occasions, such as in computer Equipment, home appliances, lighting places and various industrial electricity places. Nowadays, with the rapid development of the new energy industry, the combination of solar charge controllers and power frequency inverters is widely used in off-grid photovoltaic systems. The photovoltaic inverters currently on the market generally have low inverter efficiency, which is far lower than the high-frequency inverters with a conversion efficiency of more than 90%. The reason is that the existing power frequency...

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Problems solved by technology

The reason is that the existing power frequency inverter is designed with isolated magnetic core material, so that the DC energy generates a large loss on the magnetic core during the process of converting AC energy, so it is better to use a high frequency inverter In order to solve this problem, the existing high-frequency inverters have less loss in the process of AC-DC energy conversion, and the overall inverter efficiency is higher, but the existing high-frequency inverters are used during the process of using There are still the following defects: 1. The inverter efficiency is low, and the average efficiency is only 80%; 2. The no-load current of the transformer in the existing inverter is large, reaching 3% of the rated DC terminal current. The load power consumption causes a great waste of battery energy, which reduces the endurance performance of the inverter and affects the subsequent use efficiency; 3. Due to the high junction temperature and large heat generation of the power switch tube during operation, a large area of ​​aluminum is required The profile radiator and larger fan are used for forced air cooling, which increases the volume and weight of the inverter, making it impossible to carry out portable installation and use

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