Photovoltaic water pumps are also called solar water pumps, as shown in Figure 1. It is more and more recognized as the most attractive water supply method in the sun-rich areas in the world today, especially in remote areas without electricity . Under normal circumstances, photovoltaic water pumps (or solar water pumps) mostly refer to three-phase AC water pumps, recently named photovoltaic water pump systems.
Photovoltaic water pump system is an optical-mechanical-electrical integration system that has developed rapidly in recent years. It uses electricity from solar cells to drive high-efficiency DC water pumps through maximum power point tracking, conversion, and control devices to lift water from deep to the ground. For farmland irrigation or human and livestock drinking. Modern technologies involving electrical, mechanical, power electronics, computers and control from design to manufacturing provide extremely good means for the development of modern agriculture, energy conservation and environmental protection. This system has a good
Long-term economy, especially compared with common diesel engine pumping, has an overwhelming economic advantage. The development of this new type of environmentally friendly and energy-saving products will undoubtedly bring huge economic and social benefits to the development of industry and economy, especially the development of modern agriculture in arid areas. It is particularly in line with the construction of “resource-saving” and “environmentally friendly” “Society’s development strategy.
Solar photovoltaic water pumps are generally divided into DC photovoltaic water pumps, AC photovoltaic water pumps, and solar photovoltaic permanent magnet synchronous water pumps. DC photovoltaic water pumps are divided into brush DC photovoltaic water pumps, brushless DC photovoltaic water pumps (motor type) and brushless DC photovoltaic water pumps (magnetic drive isolation type). DC photovoltaic water pumps are mainly used in small or domestic water systems. It is characterized by high efficiency and simple structure. With the support of modern power electronic technology, the brushless DC motor enables the service life of the DC solar photovoltaic water pump to reach tens of thousands of hours. Its disadvantage is that the current power cannot be made relatively large.
AC photovoltaic pumps are mainly used in large and medium-sized systems. The photovoltaic pumps above kilowatts are still AC motors driven by solar photovoltaic pumps. The system mainly includes solar photovoltaic arrays, maximum power point tracking controllers, pumping inverters and water pumps. The working principle of the AC photovoltaic water pump is that the system uses photovoltaic components to directly convert solar energy into electrical energy. After a DC/DC boost, and then through an inverter with TMPPT function, it outputs a three-phase AC voltage to drive the AC asynchronous motor and the pump load. Water tower storage function.
(1) Solar photovoltaic array is composed of many solar cells in series and parallel, and its function is to directly convert solar energy into direct current form of electrical energy.
(2) The output volt-ampere characteristic curve of the solar cell module of the maximum power point tracking controller is strongly non-linear, and is closely related to meteorological conditions such as solar irradiance, ambient temperature, cloudy, sunny, rainy, and foggy. Its output varies with the surface of the sun. What changes is the direct current electricity, and as the photovoltaic water pump that the solar cell module loads, its drive motor is sometimes a direct current motor, sometimes an alternating current motor, and even other new types of motors, which also have non-linear properties. In this case, it is necessary to make the photovoltaic water vegetable system work in a relatively ideal working condition, and for any sunlight, the maximum potential of the output power of the solar cell module must be exerted. This requires an adapter to make the power supply and the load reach Harmonious, efficient and stable working conditions. The main functions implemented by the adaptor are the maximum power point eye tracker, inverter requirements, and some protection facilities.
(3) After the pumping inverter solar cell component passes the maximum power point tracking controller, the output is DC voltage. If the driving motor used for the water pump is a DC motor, of course, it can be directly connected when the voltage values of the two are matched. The electric motor will drive the water pump to raise water. Due to the relatively high cost of DC motors, regular maintenance or replacement of brushes is also required. In recent years, due to the advent of new speed control theory and new power electronic devices and technological advancements, AC speed control technology has made considerable progress, and its efficiency has been improved. Gradually catch up with the DC motor, but its convenience and robustness far exceed that of the DC motor. Therefore, the new drive method of the brushed DC motor is being eliminated, and the main replacement is the high-efficiency three-phase asynchronous Motors and brushless DC motors, occasionally permanent magnet synchronous motors or reluctance motors are used.
(4) Water pumps The water pumps of photovoltaic systems are mainly divided into two categories: centrifugal pumps and positive displacement pumps. Centrifugal pumps have a rotating impeller that allows water to flow radially toward the pump casing. Through the impeller, the kinetic energy of the water is increased, and then the energy is converted into potential energy by pressure; the positive displacement pump is another large type of commonly used water pump, especially in deep wells with low rate pumping. Positive displacement pumps include piston pumps, diaphragm pumps, and screw pumps, among which screw pumps are more popular.