Views:97 Author:Site Editor Publish Time: 2020-02-20 Origin:Site
In the off-grid photovoltaic system, the function of the solar photovoltaic system is to store the electricity from the photovoltaic module in the battery after transformation. Besides, it also has the functions of protecting the battery and preventing the battery from overcharging. At present, there are two main technical routes of the controller: pulse width debugging (PWM) and maximum power point tracking (MPPT). Each mode has its advantages and disadvantages, which can be selected according to different scenarios.
Early photovoltaic controllers were all PWM, which had simple electrical structure. The controller consisted of a power main switch and capacitor, as well as drive and protection circuit. The output voltage was controlled by the duty cycle of the PWM of the switch.
The PWM controller has only one switch connected between the solar array and the panel. As the battery is gradually filled and the battery voltage rises, the PWM controller will gradually reduce the amount of power supplied to the battery. The photovoltaic output will be output at the maximum power. The PWM controller has the function of battery charge and discharge management, which can prevent the battery from overcharging and discharging.
Because the pwm solar charge controller has only one switch connected between the solar module and the battery and there is no voltage dividing device such as an inductor in the middle, the voltage of the component is about 1.2-2.0 times of the voltage of the battery. For example, for a 24V power supply, the component input voltage is between 30-50V, and only one component per string can be used. For a 48V power supply, the component input voltage is between 60-80V, and only two components per string can be used.
MPPT controller is the second generation solar controller. Compared with PWM controller, MPPT controller has one more inductor and power diode, so its function is more powerful.
First, it has the maximum power tracking function. During battery charging, the solar module can output the maximum power unless the battery reaches saturation state. Second, the voltage range of the photovoltaic module is wide, and there is a power switch and inductance circuit in the controller. The voltage of the module is 1.2-3.5 times the voltage of the battery. If it is a 24V power supply, the component input voltage is between 30-80V, each string can be equipped with one or two components. If it is a 48V power supply, the component input voltage is between 60-110V, each string can be equipped with two to three components.
The choice of the scheme depends on the design characteristics, cost and external environment of solar photovoltaic arrays. When choosing, it should be considered the following factors:
The PWM method is mature, the circuit is simple and reliable, and the price is cheap, but the utilization rate of components is about 80% or more. MPPT solar charge controller refers to the solar controller with maximum power point tracking function. There is a step-down circuit between components and battery, and the utilization rate of components is about 90%.
The solar power system under 2kW is mainly used in poor and non-electric areas, such as remote mountainous areas and some poor countries in Africa. Just in order to solve the lighting demand, it is recommended to use PWM controller. This method is simple in structure, high in efficiency, convenient in user wiring, and very cheap in price. It also has no problem in driving light bulbs, small TVs, and small fans. For solar power system above 2kW, it is recommended to use MPPT controllers, which has high component utilization, high efficiency, and flexible component configuration.
All in all, PWM and MPPT controllers have their own unique advantages and disadvantages. You should follow the advice of experts to ensure that the right controller is chosen to meet your needs.