Method for optimizing voltage control and photovoltaic power generation system

Abstract

The invention discloses a method for optimizing voltage control and a photovoltaic power generation system, and particularly relates to a photovoltaic optimizer with a photovoltaic module level or a battery piece cascade level in the power generation system, which recommends to set inverter direct current bus reference voltage and a reference duty ratio of a corresponding power optimization module by setting a judgment unit according to a system transformation state. Various power generation mismatch losses of various photovoltaic modules can be avoided, meanwhile, the input voltage of a direct current bus can be stabilized within a very small change range, the voltage impact of power grid disturbance can be balanced, and the high-voltage ride-through requirement can be met; the inverter is maintained at a relatively high input voltage, so that the power generation capacity of a series body can be increased, the alternating current output voltage can be improved, and the alternating current line loss of the inverter, a boosting transformer, a cable and the like can be reduced; the method is suitable for a large-scale centralized power generation system, and the power optimizer is comprehensively and efficiently utilized to improve the power generation efficiency of a photovoltaic power station and reduce the construction cost.

Description

technical field [0001] The present invention relates to the field of photovoltaic power generation, in particular to the field of centralized photovoltaic power generation systems, and in particular to a method for optimizing voltage control and a photovoltaic power generation system provided with a photovoltaic module-level or cell string-level photovoltaic optimizer in the power generation system. Background technique [0002] Photovoltaic inverter is a DC / AC conversion device that connects photovoltaic modules or photovoltaic strings and obtains its power, usually with a maximum power / power tracking circuit (MPPT); photovoltaic power optimizer is connected to photovoltaic modules or substrings of modules Also with MPPT DC / DC converter. [0003] In terms of photovoltaic inverters, the photovoltaic inverters currently on the market are mainly string inverters, centralized inverters and distributed inverters. Among them, the string inverter is mainly multi-channel photovolt...

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Problems solved by technology

[0010] The former solution requires the input voltage of the PV inverter to be configured within a wide range. In daily operation, the input voltage of the inverter will change with the operating power, and in extreme environments, the PV string will have a negative impact on the inverter. The inverter forms an extreme current or voltage impact, which can solve the problem of component mismatch, but it will also cause an impact on the photovoltaic inverter system

The latter solution can solve the mismatch problem of photovoltaic modules and can also obtain a relatively stable input current of the inverter, but it puts forward high requirements for real-time and fast communication between the photovoltaic power optimizer and the photovoltaic inverter

Especially for large-scale photovoltaic power plants, the number of photovoltaic modules and photovoltaic strings is huge, and the accuracy and speed of the input voltage and current of the power optimizer, and the convenience of adjusting the duty cycle response speed are not enough to meet the requirements

In particular, the latter scheme adopts a buck-boost topology to deal with the problem of low voltage caused by large-area shading. It can be seen that it is not suitable for large-scale centralized power generation systems with a large number of strings.

Therefore, in the photovoltaic power generation system, in the face of problems such as component array mismatch and AC grid-connected disturbance, it is difficult to adjust the conflict between the inverter and the power optimization system.

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