Coordinated control method for photovoltaic virtual synchronous generator based on common DC bus

Abstract

The invention discloses a coordinated control method for a photovoltaic virtual synchronous generator based on a common DC bus. The system studied in the method includes a photovoltaic assembly, a three-phase inverter, an energy storage battery and a bidirectional DC / DC converter, the maximum power point tracking algorithm is implemented through the bidirectional DC / DC converter, the inverter realizes the control for the virtual synchronous generator and the function decoupling of the photovoltaic assembly, the bidirectional DC / DC converter and the three-phase inverter, the energy storage battery carries out power balancing through the bidirectional DC / DC converter on the one hand so as to ensure the stable and reliable operation of the system, and stabilizes the DC-side bus voltage on the other hand. In addition, the maximum power output of the three-phase inverter in the invention lags behind that of the photovoltaic assembly through low-pass filtering with a large time constant, the requirements for coordinate control are reduced, and the influence of power fluctuation is reduced.

Description

Technical field [0001] The invention belongs to the technical field of distributed power generation and power electronics, and particularly relates to a photovoltaic virtual synchronous generator coordinated control method based on a common DC bus. Background technique [0002] With the deterioration of the environment and the aggravation of the energy crisis, new energy is playing an increasingly important role in economic development and social progress. However, the large-scale access of new energy to the grid has relatively reduced the proportion of traditional synchronous generators. At the same time, the power system has changed from centralized power generation to distributed power generation. However, the distributed power generation system lacks the inertia and damping of traditional synchronous generators. , Without frequency modulation capability, the power system is more susceptible to power fluctuations and system failures. [0003] As a result, virtual synchronous ge...

AI Technical Summary

Problems solved by technology

In this paper, a coordinated control strategy for a unipolar common AC bus photovoltaic virtual synchronous generator is designed, the energy storage unit and DC / DC converter on the DC side are removed, and the energy storage unit outputs through an independent inverter power, this method is beneficial to the scheduling control of the power grid and energy management system, and can well suppress photovoltaic power fluctuations, but this method is aimed at the structure of the common AC bus, and the control of each unit is relatively independent, this method is not suitable for Coordinated Control of Unipolar Photovoltaic Inverter System with Common DC Bus with Unclear Function Assignment

[0006] 2. The Chinese invention patent document (publication number CN 108134402 A) published "A Virtual Synchronous Generator System and Control Method Applied to Photovoltaic Power Stations" on June 8, 2018, the present invention proposes a The virtual synchronous generator system, the inverter completes the maximum power point tracking algorithm and the virtual synchronous generator control, and the energy storage part bears the difference between the power of the three-phase inverter and the power of the photovoltaic panel, realizing functional decoupling. However, the present invention requires a high-speed communication network between the energy storage part and the inverter part, which increases the complexity of the system and is not conducive to coordinated control

[0007] 3. The Chinese invention patent document (publication number CN 106549417 A) published on March 29, 2017, "A Virtual Synchronous Generator Control Method and Device for Photovoltaic# Energy Storage System", the present invention proposes a unipolar In the photovoltaic power generation system with a common DC bus, the energy storage part maintains a power and current double loop, and the power loop setting is changed from an indirect difference value setting to a direct setting, that is, the frequency modulation power is obtained through a virtual synchronization algorithm, which weakens the relationship between the energy storage part and the inverter. The communication connection between the inverters, but the present invention does not consider the influence of power fluctuations

[0009] 1. There is little research on the coordinated control method of photovoltaic virtual synchronous generators based on the common DC bus, and the existing control methods do not consider both coordinated control and suppression of power fluctuations. It is necessary to conduct in-depth research on this coordinated control strategy;

[0010] 2. The existing research on the control method of photovoltaic virtual synchronous generator based on the common DC bus, the energy storage system needs a coordinated control strategy among photovoltaic modules, energy storage equipment and inverters to compensate for the power difference, and the implementation is relatively complicated

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