Date: 2023-05-06 hits: 2064
In the process of building and operating a photovoltaic power station, the inverter in the electrical equipment plays a very important role. Like the photovoltaic power generation system technology, it continuously improves the operating efficiency and conversion power, and makes the best combination with photovoltaic modules and other power generation equipment. Efficient photovoltaic system.
In the process of building and operating a photovoltaic power station, the inverter in the electrical equipment plays a very important role. Like the photovoltaic power generation system technology, it continuously improves the operating efficiency and conversion power, and makes the best combination with photovoltaic modules and other power generation equipment. Efficient photovoltaic system. The following is a brief introduction to the inverter:
Usually, the process of converting AC power into DC power is called rectification, the circuit that completes the rectification function is called a rectifier circuit, and the device that realizes the rectification process is called a rectifier or a rectifier. Correspondingly, the process of converting DC power into AC power is called inverter, the circuit that completes the inverter function is called inverter circuit, and the device that realizes the inverter process is called inverter equipment or inverter. Inverters, also known as power regulators, can be divided into two types: independent power supply and grid-connected use according to the use of inverters in photovoltaic power generation systems. According to the waveform modulation method, it can be divided into square wave inverter, ladder wave inverter, sine wave inverter and combined three-phase inverter. For inverters used in grid-connected systems, they can be divided into transformer-type inverters and non-transformer-type inverters according to the presence or absence of transformers. There are many types of inverters, so special attention should be paid when selecting the model and capacity. Especially in solar power generation systems, the efficiency of photovoltaic inverters is an important factor in determining the capacity of solar cells and storage batteries.
An inverter is a power adjustment device composed of semiconductor devices, which is mainly used to convert DC power into AC power. It is generally composed of a boost circuit and an inverter bridge circuit. The boost circuit boosts the DC voltage of the solar battery to the DC voltage required for inverter output control; the inverter bridge circuit converts the boosted DC voltage into an AC voltage of common frequency equivalently. The inverter is mainly composed of switching elements such as transistors. By regularly turning the switching elements on and off (ON-OFF), the DC input becomes the AC output. Of course, such an inverter output waveform simply generated by on and off loops is not practical. Generally, it is necessary to use high-frequency pulse width modulation (SPWM) to narrow the voltage width near the two ends of the sine wave, widen the voltage width in the center of the sine wave, and always make the switching element move in one direction at a certain frequency within half a cycle, thus forming A pulse train (pseudo-sine wave). The pulse wave is then passed through a simple filter to form a sine wave.
The inverter not only has the function of DC-AC conversion, but also has the function of maximizing the performance of solar cells and the function of system fault protection. In summary, there are automatic operation and shutdown functions, maximum power tracking control functions, anti-solitary operation functions (for grid-connected systems), automatic voltage adjustment functions (for grid-connected systems), DC detection functions (for grid-connected systems), and DC grounding detection Function (for grid-connected system).
Automatic operation and shutdown function
After sunrise in the morning, the intensity of solar radiation increases gradually, and the output of solar cells increases accordingly. When the output power required by the inverter is reached, the inverter starts to run automatically. After starting to run, the inverter will monitor the output of the solar cell components all the time. As long as the output power of the solar cell components is greater than the output power required by the inverter, the inverter will continue to run; it will stop until sunset, even on cloudy and rainy days. The inverter also works. When the output of the solar cell module becomes smaller and the output of the inverter is close to 0, the inverter will form a standby state.
Maximum power tracking control function
The output of the solar cell module varies with the intensity of solar radiation and the temperature of the solar cell module itself (chip temperature). In addition, because the solar cell module has the characteristic that the voltage decreases with the increase of the current, so there is an optimal operating point that can obtain the maximum power. The intensity of solar radiation is changing, obviously the best working point is also changing. Relative to these changes, the operating point of the solar cell module is always at the maximum power point, and the system always obtains the maximum power output from the solar cell module. This kind of control is the maximum power tracking control. The biggest feature of the inverter used in the solar power generation system is the function of maximum power point tracking (MPPT).
The conversion rate of a photovoltaic inverter refers to the efficiency with which the inverter converts the electricity generated by the solar panel into electricity. In the photovoltaic power generation system, the inverter plays the role of converting the direct current generated by the solar panel into alternating current, and transmits the alternating current to the power company grid. The conversion efficiency of the inverter is high, and the electricity for self-use and sale can Increase.
One is that when converting DC current into AC sine waves, it is necessary to use a circuit using power semiconductors to switch the DC current. At this time, the heat of the power semiconductors will cause losses, but this loss can be reduced by improving the design of the switching circuit. reduced to a minimum.
The second is to improve efficiency by virtue of inverter control experience. The output current and voltage of the solar panel will change with the sunshine and temperature, and the inverter can optimally control the current and voltage so that it can reach the maximum amount of power, that is, it can find the best power in the shortest time. The higher the power point, the higher the conversion efficiency will be. The control characteristics of the inverter will vary with the products of various manufacturers, and the conversion efficiency will also be different.
