Photovoltaic inverters are a major component and crucial part of solar photovoltaic (PV) power generation systems. To ensure the proper operation of these systems, the correct configuration and selection of photovoltaic inverters is essential. In addition to determining the inverter configuration based on the overall technical specifications of the PV power generation system and referring to the manufacturer's product catalog, the following technical specifications should generally be considered.
1. Rated output power
Rated output power indicates the ability of a photovoltaic (PV) inverter to supply power to a load. A PV inverter with higher rated output power can handle a larger electrical load. When selecting a PV inverter, sufficient rated power should be considered to meet the power requirements of the equipment under maximum load, as well as system expansion and the connection of temporary loads. When the electrical equipment is a purely resistive load or has a power factor greater than 0.9, the rated output power of the PV inverter is generally selected to be 10%-15% higher than the total power of the electrical equipment.
2. Output voltage adjustment performance
Output voltage regulation performance indicates the voltage stabilization capability of a photovoltaic (PV) inverter's output voltage. Most PV inverter products specify the percentage deviation of the output voltage when the DC input voltage fluctuates within its allowable range; this is commonly referred to as the voltage regulation rate. High-performance PV inverters should also specify the percentage deviation of the output voltage when the load changes from zero to 100%; this is commonly referred to as the load regulation rate. A high-performance PV inverter should have a voltage regulation rate of less than or equal to ±3%, and a load regulation rate of less than or equal to ±6%.
3. Overall machine efficiency
Overall efficiency indicates the magnitude of power loss within the photovoltaic inverter itself. For larger capacity photovoltaic inverters, efficiency values under full load and low load operation should also be provided. Generally, inverters below 1kW should have an efficiency of 80%~85%; 10kW inverters should have an efficiency of 85%~90%; and inverters with even higher power outputs must have an efficiency of 90%~95% or higher. Inverter efficiency significantly impacts the effective power generation and cost reduction of photovoltaic power generation systems. Therefore, when selecting photovoltaic inverters, it is essential to compare different models and choose products with higher overall efficiency.
4. Startup performance
Photovoltaic inverters should be guaranteed to start reliably under rated load. High-performance photovoltaic inverters can perform multiple consecutive full-load starts without damaging power switching devices and other circuits. For their own safety, small inverters sometimes employ soft-start or current-limiting start measures or circuits.
The photovoltaic industry has become a hot sector from Europe and Australia to China. In just a few years, domestic photovoltaic inverter manufacturers have sprung up like mushrooms after rain. However, there are still certain standards for choosing a solar inverter.
The first consideration is the scale of the photovoltaic power station—whether it's for a household or a business. However, building solar photovoltaic power stations in China is still relatively rare, mainly due to limitations such as building structure, which prevent the installation of solar panels. Factories and businesses still have a significant advantage. Small-scale household photovoltaic power stations are primarily targeted at villas abroad.
Secondly, efficiency is a key consideration. Simply put, efficiency is directly linked to power generation. Therefore, more and more photovoltaic inverter manufacturers are focusing their research and development on inverter efficiency as a major technological advantage. Omnik's micro-inverters ranked first in Europe in Photon's efficiency tests in Germany. See the Photon test comparison results.
Finally, reliability must be considered. A grid-connected photovoltaic (PV) power generation system converts the direct current (DC) generated by solar cells into alternating current (AC) that is in phase and frequency with the grid voltage, enabling it to both supply power to the load and generate electricity for the grid. A grid-connected PV power generation system mainly consists of a photovoltaic array, a grid-connected inverter, a controller, and relay protection devices. The photovoltaic array is the main component of the system, directly converting received solar energy into electrical energy. Currently, PV arrays used in engineering applications are generally composed of a certain number of crystalline silicon solar cell modules connected in series and parallel according to the system's required voltage.
The grid-connected inverter is the core of the entire photovoltaic grid-connected power generation system. It converts the electrical energy generated by the photovoltaic array into a 220V/50Hz sinusoidal current and feeds it into the power grid. Voltage-source inverters mainly consist of power electronic switching devices, providing power to the grid in the form of pulse-width modulation. The controller typically uses a microcontroller or DSP chip as its core component, controlling the maximum power point tracking of the photovoltaic array and regulating the power and waveform of the inverter's grid-connected current. Relay protection devices ensure the safety of both the photovoltaic grid-connected power generation system and the power grid.
Grid-connected photovoltaic (PV) power generation systems can be divided into two types according to their design requirements: non-dispatchable PV grid-connected systems, which do not include energy storage, and dispatchable PV grid-connected systems, which include energy storage. In non-dispatchable PV grid-connected systems, the grid-connected inverter directly converts the direct current (DC) generated by the PV array into alternating current (AC) with the same frequency and phase as the grid voltage. The grid connection time and power output are entirely determined by factors such as sunlight and ambient temperature. Its advantage is that the system can eliminate the need for batteries and use the grid as its energy storage unit.
When sunlight is intense, the excess electricity generated by the photovoltaic grid-connected power generation system is fed back to the grid, and the grid can supply electricity when needed. The dispatchable photovoltaic grid-connected power generation system incorporates an energy storage component. The system first charges the energy storage component, and then, as needed, the photovoltaic grid-connected power generation system can be used for grid connection or independently after inversion. The system's operating time and grid-connected power output can be manually set. When a power outage or other fault occurs in the grid, the inverter automatically disconnects from the grid. It can also choose to perform independent inversion as needed to continue supplying power to local loads.
