Solar cells are encapsulated and protected in series to form large-area solar cell modules, which are then combined with power controllers and other components to form a photovoltaic (PV) power generation device. The entire process is called a photovoltaic (PV) power generation system. A PV power generation system consists of solar cell arrays, battery packs, charge/discharge controllers, solar photovoltaic inverters, combiner boxes, and other equipment.
Why are inverters used in solar photovoltaic power generation systems?
An inverter is a device that converts direct current (DC) to alternating current (AC). Solar cells generate DC under sunlight, and batteries also store DC. However, DC power systems have significant limitations; AC loads such as fluorescent lamps, televisions, refrigerators, and electric fans cannot be powered by DC. For photovoltaic power generation to be widely used in our daily lives, inverters that can convert DC to AC are indispensable.
As a crucial component of photovoltaic (PV) power generation, the primary function of a photovoltaic (PV) inverter is to convert the direct current (DC) generated by PV modules into alternating current (AC). Inverters not only perform DC-AC conversion but also maximize the performance of solar cells and provide system fault protection. Below is a brief introduction to the automatic operation and shutdown functions, as well as the maximum power point tracking (MPPT) control function of PV inverters.
1. Maximum Power Point Tracking (MPPT) function
The output of a solar cell module varies with the intensity of solar radiation and the module's own temperature (chip temperature). Furthermore, because the voltage of a solar cell module decreases as current increases, there exists an optimal operating point where maximum power can be obtained. Since solar radiation intensity is variable, the optimal operating point also changes. To keep the solar cell module's operating point at its maximum power point relative to these changes, ensuring the system consistently draws maximum power from the module, is called maximum power point tracking (MPPT) control. A key feature of inverters used in solar power systems is the inclusion of MPPT functionality.
2. Automatic start and stop functions
After sunrise, as solar radiation intensifies, the output of the solar cells increases accordingly. Once the output power required for the inverter to operate is reached, the inverter automatically begins operation. Once operational, the inverter continuously monitors the output of the solar cell modules. As long as the output power of the solar cell modules exceeds the inverter's required output power, the inverter continues to operate until sunset, even on cloudy or rainy days. When the output of the solar cell modules decreases and the inverter output approaches zero, the inverter enters standby mode.
In addition to the two functions mentioned above, photovoltaic inverters also have functions such as anti-standby operation (for grid-connected systems), automatic voltage regulation (for grid-connected systems), DC detection (for grid-connected systems), and DC grounding detection (for grid-connected systems). In a solar power generation system, the inverter's efficiency is a crucial factor determining the capacity of the solar cells and the battery.
