Inverters perform not only the conversion of direct current (DC) to alternating current (AC) but also serve to maximize the performance of solar cells and provide system fault protection. Key functions include automatic startup and shutdown, Maximum Power Point Tracking (MPPT), anti-islanding (for grid-tied systems), automatic voltage regulation (for grid-tied systems), DC detection (for grid-tied systems), and DC ground-fault detection (for grid-tied systems). This section provides a brief overview of the automatic startup/shutdown function and the Maximum Power Point Tracking (MPPT) function.
1. Automatic Startup and Shutdown: After sunrise, as solar radiation intensity increases, the output from the solar cells also rises. Once the output power reaches the threshold required for the inverter to operate, the inverter starts automatically. During operation, the inverter continuously monitors the output of the solar cell modules; as long as this output exceeds the required operating threshold, the inverter remains active-continuing to function even on cloudy or rainy days-until it shuts down at sunset. When the output from the solar cell modules drops and the inverter's input approaches zero, the inverter enters a standby state.
2. Maximum Power Point Tracking (MPPT): The output of solar cell modules varies based on solar radiation intensity and the temperature of the modules themselves (specifically, the cell temperature). Furthermore, because the voltage of a solar cell module decreases as the current increases, there exists an optimal operating point where maximum power can be extracted. Since solar radiation intensity is constantly changing, this optimal operating point also shifts. The process of continuously adjusting the operating point of the solar cell modules to ensure they remain at the maximum power point-thereby ensuring the system consistently extracts the highest possible power output-is known as Maximum Power Point Tracking (MPPT). A defining feature of inverters used in solar power generation systems is the inclusion of this MPPT functionality.