A modular multi-level photovoltaic grid-connected system and its control method

Abstract

The invention discloses a modularization multi-level photovoltaic grid connected system and a control method thereof. A three-phase six-leg topology structure is employed each leg is formed by connecting a half-bridge module SM, N assembly modules PM and one inductor L in series. Each SM is composed of two IGBT tubes T1 and T1, two diodes D1 and D2, and one capacitor C. Each PM is formed by connecting one photovoltaic assembly PV at the two ends of the capacitor C on the basis of each SM. The control method comprises maximum power tracking control, redundancy module control, voltage stabilization control and grid connected control. According to the invention, reliable working of an inverter and maximum power tracking of the photovoltaic assemblies can be realized under the condition of local shadow, a modularization multi-level structure reduces capacitor stress and an inversion output harmonic wave content, a DC transformation circuit is unnecessary, through the control method, the maximum power tracking of each PV assembly is realized, compared to a conventional array global maximum power control method, the output power is improved, and hardware investment is reduced.

Description

technical field [0001] The invention relates to a distributed power supply, in particular to a modularized multilevel photovoltaic grid-connected system and a control method thereof. Background technique [0002] In today's world, energy issues are becoming increasingly prominent. It has become an inevitable trend of energy development to seek new energy to replace the dwindling fossil fuels. Among all new energy power generation, solar power generation has a prominent position and obvious advantages. Solar energy is an inexhaustible source of energy with huge reserves, without mining and transportation links, solar power generation is clean and pollution-free, and does not emit waste gas, which is beneficial to environmental protection. Today, when the energy crisis is about to break out and the environment is gradually deteriorating, solar power generation technology has important research value and broad application prospects. [0003] Photovoltaic power generation is ...

AI Technical Summary

Problems solved by technology

Photovoltaic modules have low power and are difficult to apply in a wide range

Photovoltaic arrays are often located in complex environments. Under shadow conditions, it is easy to cause array power mismatch, decrease output efficiency, and conventional maximum power control methods fail. However, the global maximum power control method is complicated, which will increase costs.

The traditional two-level inverter has a small capacity, the switching device withstands a large voltage and current, the DC capacitor stress is large, and the output harmonic content is large, making filtering difficult

When using a DC modular photovoltaic system, although the anti-shading ability is enhanced, the conventional inverter is still used, and the effect is not good

Images