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    How to Choose a off grid system?

    Mar 10,2023 | Daxtromn power

    Off-grid photovoltaic (PV) inverters are crucial components of off-grid PV power stations and sources, as they not only consider the performance and efficiency of the PV power source itself but also the effectiveness and reliability of the entire system composed of the power source and load.

    Voltage stability: Off-grid inverters convert the energy stored in batteries into 220V or 380V AC electricity. However, batteries are often influenced by self-discharge, leading to a wide fluctuation range in output voltage. For instance, for a nominal 24V battery, the voltage value can vary from 22V to 28V.

    Output voltage waveform distortion: Common off-grid inverters include square-wave, quasi-sine wave, and sine wave inverters. Square-wave inverters are widely used due to the advantages of a simple circuit, low price, and high efficiency for simple resistive loads, such as ordinary light bulbs, various energy-saving lamps, electric heaters, electric kettles, irons, computer, and phone chargers with switch frequency circuitry. However, the waveform distortion of a square-wave inverter is serious and includes a large amount of high-order harmonics. When a capacitive or inductive load is connected to the circuit, the high-order harmonic current output by the inverter will result in additional losses and serious overheating of the load parts, which seriously affects the operating efficiency of the system and potentially causes damage to electrical equipment. Usually, a sine-wave inverter is the preferred option for a general off-grid PV power station, even though it has a higher price, since it is more versatile and well-equipped to handle various loads for normal operation.

    Output frequency stability: The working frequency of the power grid in China is 50 Hz, and loads containing motors and other inductive loads, as well as devices that require high-frequency requirements, such as washing machines, refrigerators, and electronic clocks, will produce heat if the frequency is too high or too low, which will reduce the system's operating efficiency and lifespan. Therefore, the output frequency of the inverter should be relatively stable.

    Surge resistance capability: The surge resistance capability of the inverter, also known as overload capability, is essential as many loads draw significant electrical currents or power upon start-up. Such loads include various motors, refrigerators, air conditioners, washing machines, and water pumps. Previous generation television sets, for example, also required a significant amount of power upon start-up due to the internal demagnetizing coils. If the inverter cannot withstand the surge, it may trip. The inverter should, therefore, have sufficient margin reserve to ensure reliable load start-up.

    Load power factor: The power factor of an inverter, when handling inductive or capacitive loads, is typically between 0.7 and 0.9 for a sine-wave inverter. A lower power factor necessitates the selection of an inverter with a capacity much greater than that of the load, which may cause the alternating current circuit to produce more reactive current, resulting in an increase in system losses and decreased efficiency.

    Inverter efficiency: Inverter efficiency refers to the ratio of output power to input power under specified operating conditions, with the PV inverter's efficiency usually being measured under the condition of 80% resistive load.

    Protection function: A good inverter should also be equipped with comprehensive self-protection functions, including input undervoltage protection, input overvoltage protection, overcurrent protection, output short-circuit protection, input reverse protection, lightning protection, over-temperature protection, and even a recharge function using the grid electricity to charge the batteries.

    Although the inverter have many protection function, But when using DAXTROMN POWER inverters, we recommend that: (1) the minimum cut-off voltage should not be set too low to avoid damaging the battery; (2) ensure that the solar PV panel is within the nominal voltage range and not less or greater than the maximum number; (3) properly connect the solar panels using a series or parallel connection method; (4) ensure that the load is within the specified range; (5) when connecting the battery, confirm the positive and negative polarity several times; (6) install a lightning breaker to better protect your inverter and equipment; (7) keep it away from damp places, dust, and places where there are many insects.