250w micro grid-connected inverter

A high-level block diagram of a grid-connected solar microinverter system is shown in Figure 4. The term, “microinverter”, refers to a solar PV system comprised of a single low-power inverter module for each PV panel.

This application note describes the implementation of a 250 W grid connected DC-AC system suitable for operation with standard photovoltaic (PV) modules. The design is associated to the STEVAL-ISV003V1 demonstration board which demonstrates the possibility of implementing a full microinverter solution (MIC) using STMicroelectronics products.

The inverter is interfaced to the grid via an LCL filter. A relay is used to connect and disconnect the inverter from the grid whenever required by the application. The schematic in Figure 11 shows the filtering and relay schematic section.

The term, “microinverter”, refers to a solar PV system comprised of a single low-power inverter module for each PV panel. These systems are becoming more and more popular as they reduce overall installation costs, improve safety and better maximize the solar energy harvest. Other advantages of a solar microinverter system include:

Figure 38. Figure 39. This application note describes the design and performance of a dual stage 250 W microinverter characterized by maximum power point tracking and active and reactive power control capability. This is the main reason why the power conversion is based on a dual stage topology rather than the more common single-stage one.

When the grid is removed, the microinverter will see the local load. In the event that the local load resonates near the operating frequency before the grid was removed, the microinverter will see a small change in active and reactive power, and will not be able to detect that the grid has shut down.