Photovoltaic power generation plus energy storage system

The existing energy storage systems are mainly divided into five categories: mechanical energy storage, electrical energy storage, electrochemical energy storage, thermal energy storage and chemical energy storage. Energy storage batteries are not only used for PV energy storage, and the form of PV energy storage is not only limited to batteries. In fact, because China's current PV distribution and storage ratio and the length of the distribution and storage is still low, the growth rate of energy storage will also have a much higher potential than the new installed PV capacity.
Grid-connected photovoltaic power generation plus energy storage system architecture
Commonly, energy storage power plant (system) is mainly used for grid-connected photovoltaic power generation application. The whole system is a power generation system including PV module array, PV controller, battery pack, battery management system (BMS), inverter and corresponding joint control and scheduling system of energy storage power plant, etc.
(1) The PV module array converts light energy into electricity by using the photovoltaic effect of solar panels, then charges the lithium battery pack and converts the DC power into AC power for the load through the inverter.
(2) The intelligent controller constantly switches and regulates the working state of the battery bank according to the changes of sunlight intensity and load: on the one hand, the adjusted electric energy is sent directly to DC or AC load. On the other hand, the excess power will be sent to the battery storage. When the power generation cannot meet the needs of the load, the controller sends the battery power to the load, which ensures the continuity and stability of the whole system.
(3) The grid-connected inverter system consists of several inverters, which turn the DC power from the battery into standard 380V utility power and connect it to the low-voltage grid on the user side or send it to the high-voltage grid through the step-up transformer.
(4) The lithium battery pack plays two major roles in the system: energy regulation and load balancing. It converts the electrical energy output from the photovoltaic system into chemical energy and stores it for use when the power supply is insufficient.

Photovoltaic power plus energy storage system
Photovoltaic power plus energy storage system

The working modes of the energy storage unit are divided into four modes: grid-connected charging, off-grid charging, off-grid independent discharge and off-grid auxiliary discharge, according to the different operation modes of the PV power generation system.
Mode 1: Grid-connected charging mode. In grid-connected operation mode, when the battery capacity is insufficient, it is charged through the grid to provide energy reserve for the off-grid operation mode of PV power generation system.
Mode 2: Off-grid charging mode. In off-grid operation mode, when the battery capacity is insufficient and the PV unit has excess energy output, the battery is charged and controlled.
Mode 3: Off-grid independent discharge mode. In off-grid operation mode, when the PV power unit does not have enough energy to provide voltage and frequency support and stops working, the battery alone provides the required power to the load and supports the voltage and frequency on the AC bus of the PV system.
Mode 4: off-grid auxiliary discharge mode. Off-grid operation mode, photovoltaic power generation unit output power is not enough to meet the load demand for electricity, but can provide stable AC bus voltage and frequency, then the battery storage unit auxiliary discharge to maintain the energy balance of the system.
Application of energy storage technology in grid-connected photovoltaic power generation systems
Application in power peaking
Grid-connected power generation processors should make use of advanced processing technologies and use advanced technical processing processes to make the higher power grid load pressure lower when the power reaches peak hours are. At the same time, the personnel concerned should organically coordinate the processing of various types of energy storage technologies.

And make corresponding adjustments according to their needs. Store a large amount of energy when the load is low, and release the concentrated collected energy when the load is at its highest, to ensure the safety and stability of the system operation on the basis of effective discharge of load power supply.
Application in microgrid
In the process of transmission and distribution network development, microgrid grid connection is its main development mode. Scientific integration of relevant grid processing technology can improve the overall effect of the grid operation system and adopt the operation mode of silo classification, which separates the microgrid system and system organically, and the operation architecture of each subsystem is separated and processed. The configuration mode of energy storage system. The main modes of energy storage system configuration in PV power plant are DC-side energy storage system and AC-side energy storage system.

Energy Storage Container
Energy Storage Container

DC-Side Energy Storage
Installed in DC systems such as photovoltaic power generation, the battery combination PV array is mated and regulated in the DC section of the inverter.
High system efficiency, power station generation output can be dispatched internally by the PV plant, which can achieve seamless connection.
Good output power quality and very small output fluctuation.
It can greatly improve the smoothness, stability and regulation performance of PV power output.
The inverter used requires special design and is not suitable for upgrading most of the installed PV power plants.
Lack of large power station internal power deployment function.
AC side energy storage
The use of a separate charge/discharge controller and inverter to charge or convert the battery is actually an external energy storage device for the existing PV power system.
Overcome the problem that DC side energy storage system can not carry out unified scheduling of excess power, the system charging and discharging point is completely controlled by intelligent control system or controlled by grid scheduling, not only can concentrate the excess power in the whole station to charge the energy storage system quickly and effectively, but even can schedule the cheap low valley excess power from the grid outside the station, which is more convenient and effective for the system operation.
It can be implemented not only on the new power station, but also for the already built power station can be easily modified and additional construction, and the circuit structure is clear, and the power generation field and the energy storage field can be built in separate places, with less direct correlation with each other, which is convenient for operation control and maintenance.
Since power generation and energy storage are independent of each other, the coordination and control between them requires an additional set of special intelligent control and scheduling system, which increases the cost.
Application of energy storage technology for photovoltaic power generation systems
In the PV power plant configuration energy storage mainly for the provision of new energy consumption, auxiliary implementation of a frequency regulation and other services. In addition, energy storage power plants can also participate in peak and frequency regulation and other power market transactions to obtain some of the revenue.
(1) The solution to the problem of light abandonment.
Photovoltaic power generation power volatility, especially in some remote areas, the grid will often be unable to wind power and photovoltaic power generation to completely consume the situation, the application of energy storage technology can reduce or avoid the abandonment of light.

Installing energy storage system on the side of renewable energy power station, once the power grid operation system is in the peak shortage of power or transmission channel abnormal conditions, some power generation conditions of power energy are affected by external objective environmental factors, the actual power generation conditions will be constrained, in the actual power generation process, the power quality and operation effect released by the power generation field can not reach the preset requirements.

Photovoltaic power plus energy storage system
Photovoltaic power plus energy storage system

(2)The improvement of the quality of electric power.
In the process of power transmission by various renewable energy sources, the power generation effect of wind power and other renewable energy sources will appear unstable, and the management personnel of the power generation department should adopt unique construction processing technology, conduct a comprehensive inspection of the internal structure of the power system and the specific power generation power, and formulate a perfect power generation design plan on the basis of a thorough analysis of the distribution of power energy.

So as to effectively alleviate the power grid In order to effectively alleviate the shortage of peaking pressure and system capacity of the power generation phenomenon, and promote the effect of renewable energy generation in the power grid. By deploying larger capacity energy storage in centralized renewable energy power generation sites, based on site power forecasting and storage charging and discharging scheduling, the joint power generation of the site and storage can track the power generation plan, smooth the power generation, meet the requirements of grid connection, and improve the grid friendliness of renewable energy power generation.
The role of energy storage system in PV power plant is mainly reflected in the following aspects.
(1) to ensure system stability. Photovoltaic power plant system, photovoltaic output power curve and the load curve there are large differences, and there are unpredictable fluctuation characteristics, through the energy storage system energy storage and buffering makes the system even in the case of rapid fluctuations in the load can still operate at a stable output level.
(2) Energy backup. The energy storage system can play a backup and transition role when the PV power generation cannot operate normally, such as at night or rainy days, when the battery array cannot generate electricity, the energy storage system plays a backup and transition role, and the amount of its energy storage capacity depends on the demand of the load.
(3) Improve power quality and reliability. Energy storage system can also prevent the load voltage spikes, voltage drops and other external disturbances caused by fluctuations in the power grid on the system, the use of sufficient energy storage system can ensure the quality and reliability of power output.
The development of new energy side energy storage is not only the development of new energy and efficient consumption needs, but also to ensure the safe and stable operation of the future grid needs, with inevitability and feasibility.

From the system level, large independent energy storage power station can better achieve the above goals, standardized construction standards can improve system reliability, grid unified scheduling management is more conducive to new energy power consumption, in addition to more conducive to the rapid opening of the new energy side storage business model space. The business model of "shared energy storage" can promote the maximization of economic and social benefits of light and storage projects.

Photovoltaic power  plus energy storage system
Photovoltaic power plus energy storage system

Boland Renewable Energy Co.,LTD As an integrated new energy power company, providing you with high quality integrated wind energy , solar energy and energy storage system solutions.Boland is now a subsidiary of CRRC, and is responsible for the overseas expansion of  CRRC's wind power & solar power business. We have a relatively complete internal supply chain, service network and excellent product quality and technology.

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