Photovoltaic power generation systems, depending on their use sites, can be divided into two categories: space applications and ground applications. It can be used as an independent power source on the ground, or it can form a hybrid power generation system with wind turbines or diesel engines, etc. It can also be connected to the power grid to transmit power to the grid. Currently, the more widely used photovoltaic power generation system is mainly used as a ground independent power source. The usual independent photovoltaic power generation system mainly consists of solar cell arrays, batteries, controllers, and blocking diodes, whose roles are as follows.
1. PV cell array: The role of the array is to convert solar radiation energy directly into electrical energy, supplying the load to use. Generally by a number of solar cell components connected in a certain way, and then with the appropriate bracket and junction box composition.
2. Battery bank: The battery bank is the storage device of the solar cell array, its role is to store the excess electric energy issued by the array when there is sunshine, and supply the load for use in the evening or rainy days. In the photovoltaic power generation system, the battery is in the floating charge and discharge state, the summer sunshine is large, in addition to supplying load electricity, but also to charge the battery; in the winter sunshine is less, this part of the stored electricity gradually released, in this quarterly sectional cycle on the basis of a much smaller daily cycle, the array to the battery charging during the day, (while the array also to the load electricity), the load electricity at night all by the battery At night, the load power is supplied by the battery. Therefore, the self-discharge of the battery is required to be small, and the charging efficiency should be high, while also considering the price and convenience of use and other factors. Commonly used batteries are lead-acid batteries and silica gel batteries, more demanding occasions also have more expensive nickel-cadmium batteries.
3. Controller: In different types of photovoltaic power generation systems, the controller varies, and the number and complexity of its functions vary greatly, according to the requirements of the power generation system and the degree of importance to determine. The controller is mainly composed of electronic components, instruments, relays, switches, etc. In a simple solar cell, battery system, the role of the controller is to protect the battery, to avoid overcharging, over-discharge. If the photovoltaic power plant grid-connected power supply, the controller needs to have automatic monitoring, control, regulation, conversion and other functions. If the load is AC power, the load and battery should be equipped with inverters, the role of the inverter is to reverse the low-voltage DC power provided by the array and the battery into 220 volts AC power, supply the load.
4. Blocking diode: also known as reverse charge diode or isolation diode, its role is to use the one-way conductivity of the diode to prevent the battery from discharging through the solar array when there is no sunlight. The blocking diode requirements are that the working current must be greater than the maximum output current of the array, the reverse withstands voltage should be higher than the voltage of the battery pack. In the work of the array, there is a certain voltage drop across the blocking diode, usually 0.6V to 0.8V for silicon diode; Schottky or germanium tube 0.3V or so.
