Optimize Solar PV System with Micro Inverters

As to the optimization of the efficiency and reliability for solar PV system, a rather new means is to use micro inverters, which shall be connected to each solar panel. Equipping a separate micro inverter for each solar panel can make the system adapt to changing loads and weather conditions, thereby providing the best conversion efficiency for a single panel and the entire system.

The micro-inverter architecture can also simplify wiring, which means lower installation costs. By making consumer solar power systems more efficient, the time required for the system to get back the initial investment in solar technology will be reduced.

A key electronic component of the solar power generation system is power inverter. In commercial applications, these components are connected to photovoltaic (PV) panels, batteries that store electrical energy, and local power distribution systems or utility grids. The following figure shows a typical solar inverter. It converts the extremely low DC voltage output from the photovoltaic array into several voltages such as battery DC voltage, AC line voltage and distribution network voltage.

Micro inverter in solar power conversion system

Compared with the entire system using a solar inverter, each solar panel in the system is equipped with a micro inverter, which will once again improve the conversion efficiency of the entire system. The main advantage of the micro-inverter topology is that even if one of the inverters fails, energy conversion can still be performed.

Other benefits of using micro inverters include the ability to use high-resolution PWM to adjust the conversion parameters of each solar panel. Since clouds, shadows and back shadows will change the output of each panel, equipping each panel with a unique micro inverter allows the system to adapt to changing load conditions. This provides the best conversion efficiency for each panel and the entire system.

For example, large-scale solar photovoltaic power plants benefit from communication between panels to help maintain load balance and allow system administrators to plan in advance how much energy is available and what to do with that energy. Please note that the MCU must integrate on-chip communication peripherals (CAN, SPI, UART, etc.) to simplify the interface with other micro inverters in the solar array.Micro inverter for grid tie inverter for solar system

In many applications, the use of micro inverter topology can significantly improve the overall efficiency of the system.

Application Analysis

In small applications, each solar panel may face basically the same conditions of light, temperature, and shadow. Therefore, the role of micro inverters in improving efficiency is limited.

In order to make each solar panel work at different voltages to obtain the highest energy efficiency, it is required to use a DC/DC converter to make the output voltage of each panel unified with the operating voltage of the energy storage battery. In order to reduce the manufacturing cost as much as possible, the DC/DC converter and inverter can be designed into one module. In addition, DC/AC converters used for local power lines or connected to the distribution network can also be integrated into the module.

Solar panels must communicate with each other, which increases wiring and complexity. This is another point of contention over whether to include inverters, DC/DC converters and solar panels in the module.

The MCU of each micro inverter must still have enough capacity to run multiple MPPT algorithms to adapt to different operating environments.

In addition to meeting the requirements of the micro inverter itself, the MCU used must also handle most of the requirements of the entire system including AC/DC conversion, DC/DC conversion, and inter-panel communication. This can reduce the cost increase caused by using multiple MCUs.

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