Off-grid solar inverters are crucial components of off-grid photovoltaic power stations or sources, which not only consider the efficiency and performance of the photovoltaic power source itself but also the efficiency and reliable operation of the entire system composed of the power source and the load.
Choosing off-grid solar inverters: Stability of output voltage and waveform distortion
Off-grid solar inverters convert the energy stored in the battery into 220V or 380V AC power. However, the output voltage of the battery usually varies widely due to its own charging and discharging, such as a nominal 12V battery whose voltage can vary between 10.8 and 14.4V.
Common off-grid solar inverters include square waves, quasi-sine waves (modified sine waves), or pure sine wave inverters. Pure sine wave inverters provide high-quality AC power and can drive any type of load, but the technical requirements and costs are high. Quasi-sine wave(modified sine wave) inverters can meet most of our electrical needs, with high efficiency, low noise, and moderate price. Square wave inverters are made using simple multi-harmonic oscillators but are technologically outdated and will gradually exit the market. Usually, for a general off-grid photovoltaic power station, pure sine wave inverters should be chosen, although they are more expensive, they are more versatile and can meet the normal operation of various loads.
Choosing off-grid solar inverters: Surge power
The surge power of off-grid solar inverters is also called overload capability. In practical applications, many loads require more current or power when starting up, such as various motors, refrigerators, air conditioners, washing machines, and water pumps. In the early days, TV sets also needed more current because they had demagnetizing coils inside. If the off-grid solar inverter does not have this surge capability, it may cause the inverter to trip. The inverter should have sufficient margin to ensure the reliable startup of the load.
Choosing off-grid solar inverters: Load power factor and inverter efficiency
The power factor of off-grid solar inverters when carrying inductive or capacitive loads is usually 0.7 to 0.9 for pure sine wave inverters. If the power factor of the inverter is low, not only does it need to choose an inverter far greater than the load capacity, but it also increases the reactive current in the AC circuit, causing system losses to increase and system efficiency to decrease. The efficiency of off-grid solar inverters refers to the ratio of output power to input power under specified working conditions, usually, the efficiency of photovoltaic inverters is measured under the condition of connecting 80% of resistive load.
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