PV inverter and solar inverter

A photovoltaic inverter (PV inverter or solar inverter) is an inverter that converts the variable DC voltage generated by photovoltaic (PV) solar panels into AC power at the mains frequency, which can be fed back to commercial transmission systems or used for off grid power grids. Photovoltaic inverter is one of the important system balancing (BOS) components in photovoltaic array systems, which can be used in conjunction with general AC powered equipment. Solar inverters have special functions that complement photovoltaic arrays, such as maximum power point tracking and islanding protection.

Energy inverters can be divided into the following three categories: 1. Stand alone inverters: used in independent systems, photovoltaic arrays charge batteries, and inverters use the DC voltage of batteries as the energy source. Many independent inverters also integrate battery chargers, which can charge the battery with AC power. Generally, this type of inverter does not come into contact with the power grid, so it does not require islanding protection function. 2. Grid tied inverters: The output voltage of the inverter can be fed back to a commercial AC power source, so the output sine wave needs to be in the same phase, frequency, and voltage as the power source. The grid connected inverter will have a safety design, and if it is not connected to the power source, it will automatically shut down the output. If the power supply of the grid trips, the grid connected inverter does not have the function of backup power supply. 3. Battery backup inverters are a special type of inverter that uses a battery as its power source and, in conjunction with a battery charger, charges the battery. If there is excessive power, it will be recharged to the AC power source. This type of inverter can provide AC power to designated loads when the grid power supply trips, so it needs to have islanding protection function.

Maximum Power Point Tracking Broadcast Editor's Main Article: Maximum Power Point Tracking Photovoltaic inverters use Maximum Power Point Tracking (MPPT) technology to extract the maximum possible power from solar panels. There is a complex relationship between solar irradiance, temperature, and total resistance of solar cells, resulting in nonlinear changes in output efficiency, known as the current voltage curve (I-V curve). The purpose of maximum power point tracking is to generate a load resistor (of the solar module) based on the output of the solar module in various environments to obtain the maximum power. The fill factor (FF) of a solar cell, combined with its open circuit voltage (Voc) and short-circuit current (Isc), determines the maximum power of the solar cell. The shape factor is defined as the ratio of the maximum power of a solar cell divided by the product of Voc and Isc. There are three different algorithms for maximum power point tracking: perturb and observe, incremental conductance, and constant voltage. The first two are often referred to as "hill climbing", which follows the curve of voltage versus power. If it falls to the left of the maximum power point, the voltage is increased, and if it falls to the right of the maximum power point, the voltage is decreased.

Micro photovoltaic inverter broadcast editor Micro photovoltaic inverter is a photovoltaic inverter that only operates with a single solar module, converting the DC power of the solar module into AC power. Its design allows multiple micro photovoltaic inverters to operate independently and in parallel in a modular manner. The advantages of micro photovoltaic inverters include the ability to optimize power for a single solar module, the ability for each module to operate independently, improved installation methods and fire safety, the lowest system design cost, and the ability to minimize inventory. In 2011, a study conducted by Appalachian State University in the United States found that under unshielded conditions, individual inverters can generate 20% more electricity than series connected devices using only one inverter, while under shielded conditions, they can generate 27% more electricity.

Grid connected inverter Grid connected inverter Solar grid connected inverter feeds back electrical energy to the grid. If the grid loses power, it is necessary to quickly cut off the power supply lines to the grid. This is a requirement of the National Electrical Code (NEC) in the United States to ensure that the grid connected inverter will also shut down in the event of a power outage, in order to avoid injury to personnel repairing the grid. At present, there are many different technologies used in grid connected inverters on the market, including the use of newer high-frequency transformers, traditional power frequency transformers, or transformerless architectures. High frequency transformers do not directly provide 120V or 240V AC power, but have a computer-controlled multi-step program that converts the power supply into high-frequency AC power, then into DC power, and finally into the voltage and frequency required by the power supply. In the past, there were some doubts about systems without transformers that had to supply power to the grid, mainly because there was no galvanic isolation between the DC and AC circuits. If there was a fault at the DC end, a large current would flow to the AC end. However, since 2005, the National Electrical Code of the National Fire Protection Association (NFPA) has allowed inverters without transformers. VDE 01261 and IEC 6210 also allow and define the security mechanisms required for such systems. Firstly, residual current or grounding circuit is required to detect abnormal short circuits, and insulation testing should also be conducted to confirm the separation between DC and AC circuits. Many solar inverters are designed to be connected to the grid, and if the grid is not detected, the inverter will not operate. This type of inverter also has special circuits that accurately match the output voltage, frequency, and phase with the power supply.

Solar charging controller, which can be used in conjunction with solar panels and devices that use direct current. The charging controller can provide stable DC power output, store excess energy in the battery, and monitor the battery level to avoid overcharging or overdischarging. If some more expensive modules can also support MPPT. The inverter can be connected to the output of the solar charging controller, and then the inverter can drive the AC load.

Solar pump inverter can convert the direct current generated by the solar module into alternating current to drive the submersible pump, without the need for batteries or other energy storage devices. Combined with MPPT (Maximum Power Point Tracking), the solar pump inverter can adjust the output frequency to control the pump speed and avoid damage to the motor driving the pump. Solar pump frequency converters generally have several interfaces that allow the solar module array to provide DC current, one interface to output AC voltage, and possibly an interface to connect to a water level sensor input.