Solar pumping inverter controls and adjusts the operation of the photovoltaic water pumping system (solar water pump system), converts the direct current generated by the photovoltaic array into alternating current, drives the water pump, and adjusts the output frequency in real time according to the change of the sunlight intensity to realize the maximum power point tracking ( MPPT).
Solar water pump inverters are off-grid inverters that do not depend on the power grid and can work independently with load, but conventional off-grid inverters need to be equipped with batteries to work, and lead-acid batteries are expensive, accounting for 30% of the system cost around, the lifespan is short, only 3-5 years, which affects the investment income of the system.
The photovoltaic water pumping system does not need to be equipped with batteries. It works when there is sunlight. A water tower is built at a high place. When water is needed, water can be drawn from the water tower. The inverter itself will also be equipped with a water level switch, which is very convenient and practical. Its function is equivalent to an off-grid system. The cost of the water tower is much lower than that of the battery.
The motor is the most difficult load to carry in the off-grid system, because the motor needs a lot of energy to start. The starting power of the conventional motor is about 3 times the rated power, while the pump motor needs to pump the water to a high place, and the starting power is 5 times the rated power. If the conventional off-grid inverter needs to have a pump motor, it needs to be amplified by 5 times.
For example, a 2kW pump motor needs a 10kW off-grid inverter to drive it. During normal operation, the DC input should also be greater than 2kW, the motor can run continuously. This increases the system cost, and the photovoltaic pump inverter has added a special algorithm, generally only 20% of the power can be increased, such as a 4kW pump motor, it can be started with a 5kW pumping inverter. During operation, the photovoltaic input power does not require 4kW to run continuously, and about 1kW can also make the water pump run.
Why can the water pump inverter have such a function against the sky? It starts with the principle of alternating current. There are three elements in alternating current, voltage, current and frequency. Under normal circumstances, the frequency is the same as 50Hz. After 50 rotations, the power varies with the current and voltage, so we generally use the voltage and current to calculate the power.
But the motor is different, its power and frequency are related, the normal rated power is the power at the frequency of 50Hz, when the frequency drops, the power will also drop. The rated power of the motor = rated torque × rated rotation, as long as the rated torque remains unchanged, the motor can run, so when the frequency and voltage drop, the rated power and the speed or frequency drop in direct proportion.
The water pump inverter adds the inverter function to the inverter, which can change the frequency of the AC output. When starting, the frequency is reduced, and the speed is exchanged for power. After the motor starts, the frequency is increased and the speed is increased. The frequency can also change with the light, so that even a 1kW photovoltaic input can drive a 4kW pump to run, isn’t it amazing?
Since the function of the water pump inverter is so unbelievable, can they expand their application range? The answer is no, because the output voltage, current, phase and frequency of the water pump inverter change with the light, and many occasions can not be used.
Due to technical limitations, multiple water pump inverters cannot be used in parallel, and must be one inverter with one motor, so the maximum power will be limited; there is currently no water pump inverter that supports energy storage, DC coupling In some low-temperature areas in winter, the outside water tower will freeze, and the photovoltaic pumping system will also be limited; the pump inverter cannot be connected to the grid, because the grid requires frequency and voltage synchronization.
The load that the water pump inverter can carry is very limited. At present, except for the water pump motor, all loads with stable power and requirements for voltage and frequency cannot be carried. For example, the water pump inverter cannot directly carry lights, refrigerators, computers, washing machines. , Even inverter air conditioners can not be brought, only pure resistive load water heaters.
