December 2012
Doc ID 022934 Rev 1
1/53
AN4070
Application note
250 W grid connected microinverter
By Rosario Attanasio
Introduction
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.
In fact, both the components used to implement the power, control and communication
section belong to the product portfolio offered by STMicroelectronics.
The design is based on two power stages, namely, an interleaved isolated boost DC-DC
converter and a mixed frequency DC-AC converter. The control section is based on an
STM32F103xx microcontroller which ensures proper maximum power point tracking
(MPPT) on the input side of the system and decoupled control of the active and reactive
power on the output. The control algorithm has been developed to allow system operation
both with 230 V AC, 50 Hz grids and with 240 V AC, 60 Hz without any hardware
modifications. The connection to a 120 V AC, 50/60 Hz grid requires few hardware
modifications to ensure the best system performance. An image of the STEVAL-ISV003V1
demonstration board is shown in
Figure 1
.
Figure 1.
Image of the 250 W MIC
www.st.com
