CN-122000970-A - Maximum power tracking discharge power distribution system and method for photovoltaic group string side energy storage

Abstract

The invention discloses a maximum power tracking discharge power distribution system and a maximum power tracking discharge power distribution method for photovoltaic string side energy storage, wherein an energy storage inverter is connected in parallel to the output end of a photovoltaic string and then connected to a grid-connected inverter, the grid-connected inverter realizes normal photovoltaic maximum power tracking to send electric energy into a power grid, the energy storage inverter adaptively adjusts an energy storage discharge power value according to photovoltaic output power and a battery discharge stage, photovoltaic and energy storage discharge flexible synchronous connection is realized, a P-V characteristic curve of the grid-connected inverter is given to keep photovoltaic curve characteristics, and energy storage maximum capacity discharge is realized while failure of photovoltaic maximum power tracking is avoided.

Inventors

• LIU JIANGNING
• ZHANG WEI
• FU JUNCHENG

Assignees

• 江苏百瑞自动化科技有限公司

Dates

Publication Date

20260508

Application Date

20260122

Claims (6)

1. 1. A maximum power tracking discharge power distribution system for photovoltaic string side energy storage is characterized by comprising a photovoltaic string, an energy storage inverter, a grid-connected inverter and a battery, wherein the output end of the photovoltaic string is respectively connected with the input ends of the grid-connected inverter and the energy storage inverter, the energy storage inverter is connected with the battery, The grid-connected inverter realizes photovoltaic maximum power tracking and electric energy feeding into a power grid, and the energy storage inverter performs a discharging method, namely, a virtual curve simulating photovoltaic P-V characteristics is generated according to photovoltaic output power and battery electric quantity, and output power values are adjusted in a self-adaptive mode, so that the output power of the energy storage inverter can be coordinated with the maximum power tracking requirement of the photovoltaic inverter under two modes of photovoltaic string operation and non-operation, and meanwhile, the maximum photovoltaic energy output and grid-connected inverter grid connection are met normally.
2. 2. The system for distributing maximum power tracking discharge power of side energy storage of a photovoltaic string according to claim 1, wherein when the energy storage inverter performs a discharge method, the energy storage inverter simulates the photovoltaic string output according to a preset energy storage discharge power calculation formula when the photovoltaic string does not work P 1 = 0 in a first mode, and the energy storage battery solely provides electric energy required by the grid-connected inverter.
3. 3. The maximum power tracking discharge power distribution system for photovoltaic string side energy storage according to claim 2, wherein when the energy storage inverter performs a discharge method, the energy storage inverter adopts periodic photovoltaic string maximum power point tracking real-time calculation and updates an energy storage discharge power distribution formula in combination with a photovoltaic output curve when the output power P 1 of the photovoltaic string is greater than 0 in a second mode, and the energy storage battery and the photovoltaic string jointly provide electric energy of the grid-connected inverter to realize coordinated release of electric energy.
4. 4. The photovoltaic string side energy storage maximum power tracking discharge power distribution system according to claim 2, wherein the mode one energy storage discharge power calculation formula is as follows: , Wherein P m is the maximum output power of the grid-connected inverter, epsilon is a power adjustment factor, V is the current voltage of the connection point of the photovoltaic string and the energy storage inverter, V 0 is the open-circuit voltage of the photovoltaic string, and V m1 is the rated power point voltage of the energy storage inverter.
5. 5. The photovoltaic string side energy storage maximum power tracking discharge power distribution system according to claim 3, wherein the mode two energy storage discharge power calculation formula is: , Wherein P m is the maximum output power of the grid-connected inverter, epsilon is a power adjustment factor, V is the current voltage of the connection point of the photovoltaic string and the energy storage inverter, V 0 is the open-circuit voltage of the photovoltaic string, V m is the current maximum power point voltage of the photovoltaic string, and P 1 is the current output power of the photovoltaic string.
6. 6. Discharge power distribution method applied to the maximum power tracking discharge power distribution system according to claims 1-5, characterized by the steps of: Step S1, judging the photovoltaic output condition, when P 1 = 0, the energy storage inverter enters a first mode, executing step SA1, when P 1 >0, the energy storage inverter enters a second mode, and executing step SB1; Step SA1, collecting the current voltage V of the connection point of the photovoltaic string and the energy storage inverter, substituting the current voltage V into a mode-one energy storage discharge power calculation formula to obtain energy storage discharge power P Modality one ; Step SA2, a fixed time T is spaced, and the step S1 is executed in a return mode; Step SB1, collecting the current voltage V of the connection point of the photovoltaic string and the energy storage inverter and the current output power P 1 of the photovoltaic string, substituting the current voltage V and the current output power P 1 into a modal two energy storage discharge power calculation formula to obtain energy storage discharge power P Mode two ; step SB2, a fixed time T is spaced, the system enters a short calibration period, and a time interval T k is set; step SB3, at the beginning time of T k , locking the discharge power of the energy storage inverter at the ending time of the last time interval T, recording the discharge power as a fixed value P (k-1), and discharging the energy storage inverter at constant power P (k-1) in the period of T k ; Step SB4, automatically tracking a new maximum power point in the period of the photovoltaic inverter T k , and recording the voltage V m (k) of the maximum power point at the moment; step SB5 receiving new regulatory factor (k), If there is no new adjustment factor, the last adjustment factor is used (K-1) updating V m and the regulating factor in the modal two-energy-storage discharge power calculation formula Step S1 is executed back.

Description

Maximum power tracking discharge power distribution system and method for photovoltaic group string side energy storage Technical Field The invention belongs to the technical field of photovoltaic power generation, and particularly relates to a maximum power tracking discharge power distribution system and method for photovoltaic string side energy storage. Background Solar photovoltaic power generation is a clean energy technology for directly converting solar energy into electric energy, and has the advantages of being renewable, pollution-free, sustainable and the like. In recent years, with global importance of environmental protection and sustainable development, solar photovoltaic power generation is increasingly widely applied and popularized. As the photovoltaic power generation starts to push peak-valley electricity prices, the electricity prices are lowest at the moment when the original sunlight is most sufficient, so that the economic benefit of the photovoltaic power generation is reduced, and energy storage devices are introduced into a plurality of photovoltaic power generation sites. The traditional net side energy storage mode has large energy storage capacity, so that the equipment is large in size, safety and other factors are considered, and the equipment cannot be placed in many places. Therefore, a string-side energy storage mode of the photovoltaic group is provided so as to realize a flexible and compact distributed energy storage mode. Although the photovoltaic string can output maximum power in strong light irradiation or low temperature environment, the maximum power output by the photovoltaic string can be obviously reduced in overcast and rainy days or high temperature environment, and the self-adaptive adjustment of the battery discharge power is needed to prevent the failure of tracking the maximum power of the grid-connected inverter. Therefore, a method for coordinating and distributing energy of the battery energy storage and inversion grid-connected self-adaption energy on the photovoltaic string side needs to be designed, so that the output power of the energy storage inverter can be coordinated with the maximum power tracking (MPPT) requirement of the photovoltaic inverter in two states of operation and non-operation of the photovoltaic string, and meanwhile, the maximum energy storage energy output is met and the failure of photovoltaic maximum power tracking is avoided. Disclosure of Invention In order to solve the technical problems, the invention provides the following technical scheme: The invention provides a maximum power tracking discharge power distribution system for photovoltaic string side energy storage, which aims at the problems existing in the prior art, and comprises a photovoltaic string, an energy storage inverter, a grid-connected inverter and a battery, wherein the output end of the photovoltaic string is respectively connected with the input ends of the grid-connected inverter and the energy storage inverter, the energy storage inverter is connected with the battery, The grid-connected inverter realizes photovoltaic maximum power tracking and electric energy feeding into a power grid, and the energy storage inverter performs a discharging method, namely, a virtual curve simulating photovoltaic P-V characteristics is generated according to photovoltaic output power and battery electric quantity, and output power values are adjusted in a self-adaptive mode, so that the output power of the energy storage inverter can be coordinated with the maximum power tracking requirement of the photovoltaic inverter under two modes of photovoltaic string operation and non-operation, and meanwhile, the maximum photovoltaic energy output and grid-connected inverter grid connection are met normally. Further, the method for performing discharging by the energy storage inverter generates a virtual curve simulating the photovoltaic P-V characteristic according to the photovoltaic output power and the battery electric quantity, and adaptively adjusts the output power value, so that the output power of the energy storage inverter can be coordinated with the maximum power tracking requirement of the photovoltaic inverter under two modes of operation and non-operation of the photovoltaic string, and the condition that the maximum photovoltaic energy output and grid-connected inverter are normally connected is met; Further, according to the maximum power tracking discharge power distribution system for the photovoltaic string side energy storage, the energy storage inverter is specifically divided into two working modes according to the electric quantity of the energy storage battery and the string output condition of the photovoltaic string; When the photovoltaic string does not work P 1 =0, the energy storage inverter simulates the photovoltaic string output according to a preset inverter power distribution curve, and the energy storage battery independently provides the el