VRLA battery in photovoltaic system applications - Power Circuits - Circuits

Foreword China has a vast territory, uneven population distribution, and east and west. Due to the geographical environment and relatively backward economy, some areas have relatively scarce power. The national power grid cannot cover, cannot concentrate power supply, or the grid quality is unstable. The local economic development and the improvement of people's lives have created certain obstacles. Especially in China's north, northwest and other places, the problem is particularly prominent, and there is an urgent need for a stable and reliable power system suitable for use in the region. The commonly used separate power supply systems are generator sets, solar systems, wind power systems, and wind and solar hybrid systems.
The generator set uses primary energy as a power source to drive the internal combustion engine, the internal combustion engine drives the generator, and the generator performs magnetic line cutting motion to generate electric energy. The primary energy resources are becoming scarcer, the prices are getting higher and higher, and the natural environment is seriously affected.
Solar energy systems, wind power generation systems, and wind-solar complementary systems use the inexhaustible light energy and wind energy that are inexhaustible in nature as energy sources. They are converted into usable electrical energy through a certain replacement device. This energy is natural and environmentally friendly. The concept of energy saving, environmental protection and love of the earth. The ability of such power sources to continue to supply power requires energy storage equipment to provide protection. Currently, the main energy storage equipment used is nickel-cadmium batteries and VRLA batteries. However, due to cost, lack of raw materials, etc., nickel-cadmium batteries have gradually been replaced by VRLA batteries. Let's take the photovoltaic system as an example to introduce the application of VRLA battery in photovoltaic system.
Introduction to photovoltaic system. The working principle of the photovoltaic system Under the condition of good illumination conditions, the solar cell module generates a certain electromotive force, and the solar cell array is formed by series and parallel connection of components, so that the square matrix voltage reaches the requirement of the system input voltage. A part of the power supply system is used, and a part of the battery is charged by the charge and discharge controller, and the electric energy converted by the light energy is stored. When the lighting conditions are not met, the battery pack provides the power required by the power system through the inverter.
two. The photovoltaic system consists of a solar cell array, a battery pack, a charge and discharge controller, and an inverter. The role of each part of the equipment is:
(1) Solar cell array: In the case of light, the battery absorbs light energy, and the accumulation of different charges on both ends of the battery, that is, the "photogenerated voltage" is generated, which is the "photovoltaic effect". Under the effect of the photovoltaic effect, the two ends of the solar cell generate an electromotive force, which converts light energy into electrical energy, which is a device for energy conversion. Solar cells are generally silicon cells, which are classified into single crystal silicon solar cells, polycrystalline silicon solar cells, and amorphous silicon solar cells.
(2) Battery pack: Its function is to store the power generated by the square array of solar cells when exposed to light and to supply power to the load at any time.
(3) Controller: Automatically control the choice of power, choose between mains, solar power, and battery power to charge the battery.
(4) Inverter: A device that converts direct current into alternating current.

Analysis of battery performance requirements for photovoltaic systems. The working conditions of the battery for photovoltaic power generation system are in the environment of photovoltaic power station. When the lighting conditions are good (daytime), the solar cell module receives sunlight, outputs electric energy, some DC and AC loads work, and the other part supplies battery charging; the lighting conditions are not good. At night (night or rainy day), the solar cell module cannot work, the battery pack supplies power, supplies DC or AC load, and the battery is in a circulating state. Therefore, in this use environment, the life of the battery is the cycle life.
The operating conditions of the battery used in the photovoltaic system and the battery application are different in other working conditions. The main differences can be summarized as follows:
(1) The charging rate is very small. Due to cost, location space and other issues, the amount of solar cell input will be greatly limited. In order to ensure the normal use of the power system, the charging power that is often supplied to the battery becomes very limited, and the average charging current is It is generally 0.05C10 to 0.1C10, and rarely reaches 0.1C10A.
(2) The discharge rate is very small. The system can design the maximum load capacity, the longest backup time, and the configured battery capacity is large. In actual use, the load is much smaller than the design load, and the battery discharge rate is usually C20 ~ C240, or smaller.
(3) Due to the limitation of natural resources, the battery can only be charged when there is sunshine: that is, the charging time is limited.
(4) The battery cannot be charged according to the given charging rule.
two. Photovoltaic power generation system performance requirements for VRLA batteries The batteries in photovoltaic power generation systems are frequently in the repeated cycle of charge-discharge. Due to the instability of sunlight, the unfavorable conditions of overcharge and deep discharge sometimes occur, and the photovoltaic power generation system is large. Some are used in the western region, and the altitude is above 2500M. Therefore, the following requirements are imposed on the batteries in the photovoltaic power generation system:
(1) It has deep cycle discharge performance and long charge and discharge cycle life;
(2) Strong resistance to overcharging;
(3) Capacity recovery ability after overdischarge;
(4) Good charging acceptance;
(5) When the battery is used in a static environment, the electrolyte is not easily delaminated;
(6) Performance with no maintenance or less maintenance;
(7) It should have good high and low temperature charge and discharge characteristics;
(8) It can adapt to the use environment of high altitude (above 2500M above sea level);
(9) The batteries in the battery pack have good consistency.

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