1. Function of the inverter
Inverters are an important application aspect of power electronics technology. Power electronics technology is a comprehensive technology in which various technologies such as electricity, electronics, automatic control, computers and semiconductors penetrate and combine organically.
As we all know, the function of the rectifier is to rectify the 50Hz alternating current into direct current. An inverter is the exact opposite of a rectifier, its function is to convert direct current to alternating current. This reverse process, which corresponds to rectification, is called “inversion”. Solar cells generate direct current under sunlight, however systems powered by direct current have significant limitations. For example, fluorescent lamps, TV sets, refrigerators, electric fans, etc. cannot be directly powered by DC power, and the same is true for most power machinery. In addition, when the power supply system needs to increase or decrease the voltage, the AC system only needs to add a transformer, while the buck-boost technology and device are much more complicated in the DC system. Therefore, except for special users, inverters are required in solar photovoltaic power generation systems. The inverter also has the function of automatic voltage regulation or manual voltage regulation, which can improve the power supply quality of the solar photovoltaic power generation system. In addition, solar photovoltaic power generation will eventually achieve grid-connected operation, which requires the use of AC systems. In summary, the inverter has become an indispensable and important supporting equipment in the solar photovoltaic power generation system. TYCORUN provides solar photovoltaic power generation system suitable for lithium battery purchase – go now.
2. Technical requirements for inverters of solar photovoltaic power generation systems
The solar photovoltaic power generation system using AC power output is composed of four major parts: photovoltaic array, charging efficiency controller, battery and inverter (the grid-connected power generation system can generally save the battery). The technical requirements of the solar photovoltaic power generation system for the inverter are as follows.
(1) It has high inverter efficiency. Due to the high price of solar cells at present, in order to maximize the utilization of solar cells and improve the efficiency of the system, we must try to improve the efficiency of the inverter.
(2) It has high reliability. At present, solar photovoltaic power generation systems are mainly used in remote areas, and many power stations are unattended and maintained. This requires the inverter to have a reasonable circuit structure, strict component selection, and requires the inverter to have various protection functions, such as input DC polarity reverse protection, AC output short circuit protection, overheat protection and overload protection.
(3) The DC input voltage has a wide range of adaptation. Since the terminal voltage of the solar cell varies with the load and solar irradiance, the battery has a clamping effect on the voltage of the solar cell. However, since the voltage of the battery fluctuates with the change of the remaining capacity and internal resistance of the battery, especially when the battery is aging, the terminal voltage of the battery has a large variation range. For example, the terminal voltage of a 12V battery can vary between 10-16V, which requires the inverter to work normally within a large DC input voltage range and to ensure the stability of the AC output voltage.
(4) In medium and large-capacity solar photovoltaic power generation systems, the output of the inverter should be a sine wave with less distortion. This is because in medium and large-capacity systems, if a square wave is used for power supply, the output will contain more harmonic components, and high-order Noble waves will generate additional losses. The loads of many solar photovoltaic power generation systems are communication or instrumentation equipment, which have high requirements for power supply quality. In addition, when medium and large-capacity solar photovoltaic power generation systems are connected to the grid, in order to avoid power pollution to the public grid, the inverter is also required to output a sinusoidal waveform with a required distortion degree.