Series-parallel inverter combined optical storage microgrid structure and control method

Abstract

The invention provides a series-parallel inverter combined optical storage microgrid structure and a control method. The whole optical storage microgrid system is formed by an energy storage subsystemand a photovoltaic subsystem which are mutually connected in parallel, wherein the energy storage subsystem and the photovoltaic subsystem supply power for an equivalent regional load concurrently through respective line impedance. The energy storage subsystem and the photovoltaic subsystem are respectively formed by cascading a plurality of inverter modules which are mutually connected in series, and realize improvement in voltage level and power capacity. Compared with the traditional hybrid optical storage microsource, the system structure provided by the invention can realize flexible control for a single energy storage and photovoltaic unit and improve the conversion efficiency of the whole system. In addition, the invention provides an MPPT algorithm based droop control method in order to realize the maximum utilization ratio of renewable photovoltaic energy; and the invention provides an SOC algorithm based upper droop control strategy in order to realize supply and demand power balance of the system and the charge state balance between the series energy storage modules, and reasonable power flow and stable voltage frequency of the off-grid system are achieved without communication.

Description

technical field [0001] The invention belongs to the field of distributed power generation, power electronic control technology and micro-grid technology, and specifically relates to a structure and control method of an optical-storage micro-grid combined with series-parallel inverters. Background technique [0002] Due to the advantages of low environmental pollution and high conversion efficiency, renewable energy power generation is one of the effective components of the future third-generation integrated energy network system, attracting more and more researches by scholars and engineers. Among them, photovoltaic power generation, as one of the main distributed power generation, has been more and more applied due to the gradual reduction of its own cost and the widespread existence of solar energy. In order to reasonably integrate photovoltaic power generation, a series of collaborative control and optimization technologies based on photovoltaic microgrids have been propo...

AI Technical Summary

Problems solved by technology

[0004] Due to the inherent low voltage and small power capacity characteristics of a single photovoltaic module and energy storage module, a two-stage converter is generally required, the front-stage DC-DC converter performs boosting work, and the latter stage performs DC-AC inverter work. The energy storage unit is flexibly controlled, but the two-stage converter reduces the conversion efficiency and increases the system cost

In order to overcome the low-voltage and small-capacity characteristics, inverters can be connected in series, but as the number of cascades increases, a single centralized controller will need to deal with exponentially increased sampling variables, control variables and control objectives, and the control system It will become extremely complicated, seriously affecting the development prospects of tandem photovoltaics

[0005] In the existing technology, there is no solar-storage microgrid structure and control method combined with series-parallel inverters. While considering the low-voltage characteristics of solar-storage units, centralized energy storage configuration is performed. At the same time, in order to meet the control The demand for high reliability and plug-and-play characteristics of the system also urgently requires the development of a method based on decentralized control of individual modules to achieve stable operation of the system and reasonable power flow in an environment that does not require inter-module communication at all.

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