In the solar power system system, the control part of the wind and solar hybrid power supply system, as the "brain" of the power supply system, directly affects the operation mode and return rate of the system. In the solar power system, the wind and solar hybrid power supply system, as the name suggests, the charge controller manages the charging of the battery pack. Its main function is to prevent the electric energy in the battery from returning to the solar module when the voltage output of the photovoltaic system at night is zero. In addition, it also plays a key role in preventing overcharging. Overcharging often causes the battery to be damaged due to gas and overheating.
At present, there are two mainstream technologies that dominate the solar photovoltaic system charge controller market: pulse width debugging (PWM) and maximum power point tracking (MPPT). Each technology has its own unique advantages and disadvantages, making them more or less suitable for different applications, which are closely related to variables such as solar output, cost and space, efficiency, and ambient temperature.
1.PWM mode
The PWM charging method in the solar power supply system is to charge the battery with a pulse current that automatically changes the duty cycle. Such pulse charging can make the battery safer and faster to fully charge the battery. During the disconnection period, the battery’s chemical reaction produces oxygen and The hydrogen has time to recombine and be absorbed, so that the concentration polarization and ohmic polarization are naturally eliminated, thereby reducing the internal pressure of the battery and allowing the battery to absorb more power. The pulse charging method in the solar power supply system enables the battery to have a sufficient response time, reduces the amount of gas evolution, and improves the battery's acceptance rate of the charging current. In addition, it can help reduce the battery cycle and extend battery life, so that the battery can be fully charged-many solar technicians call it a "floating charge."
2.MPPT mode
The MPPT controller uses the maximum power point tracking technology to extract the maximum power from the solar module to charge the battery in the solar power supply system. The maximum power point is tracked by the single-chip control program, and the method is completely automatic, without user intervention and adjustment. When the maximum power point of the module changes with environmental conditions, the controller automatically tracks the maximum power point of the module to ensure that the maximum energy is obtained from the solar module.
Both PWM and MPPT solar controllers have their own unique advantages and disadvantages. Which model to choose depends on the design characteristics, cost, and external environment of the solar system.
1. Efficiency comparison
Although the PWM controller is much more advanced than the "on/off" control method (used in traditional photovoltaic cell systems), its biggest disadvantage compared with the MPPT controller is efficiency. The PWM charge controller cannot use photovoltaic ( PV) The maximum power generated by the array is charged, and its overall efficiency is usually between 65-85%. On the other hand, the MPPT controller will ensure that the solar array is always in the best operating state. In some cases, such as when the weather is cold, the charging efficiency provided by the MPPT method is 30% higher than that of the PWM method.
2. The size and output comparison of solar modules
The overall size and output of the photovoltaic array have the most important influence on the choice of controller technology. Generally speaking, the PWM charge controller is a low-cost solution, suitable for small systems, and the temperature range of the solar charging unit is 45-75°C. On the other hand, the MPPT controller is a better choice for large systems (150-200W), and its higher efficiency means more considerable economic benefits. In addition, the MPPT controller supports users to obtain the maximum power from the photovoltaic (PV) array. When there is additional power demand and the space is limited, the size of the photovoltaic array cannot be expanded. In this case, the MPPT controller has obvious advantages.
In addition, factors such as cost and design characteristics must also be considered. However, in general, no technology is the best, so it is very important for users to consult the manufacturer and system design and installation personnel in time to ensure that the correct controller is selected to meet the specific requirements of the system.
