STEVAL-ISV003V1 #2: 250W Solar Microinverter, MPPT

The STEVAL-ISV003V1 is a demonstration board which implements the microinverter concept and is designed to optimize the power production of each single solar panel by means of DC/AC conversion. The conversion system is capable of both grid synchronization and Maximum Power Point Tracking (MPPT) thanks to the use of an advanced control algorithm implemented in the 32-bit STM32 microcontroller. The MPPT function is based on the perturb and observe (P & O) concept which seeks the best operating point of the panel, thus maximizing the energy produced under any environmental condition. The grid synchronization algorithm has the advantage over standard solutions of a decoupled control of active and reactive power. The STEVAL-ISV003V1 demonstration board uses a high-frequency (HF) isolated DC/DC converter with interleaved current and an optimized full-bridge DC/AC inverter. The typical solar panel voltage is first stepped up to about 400 V and then converted into AC to create a sinusoidal output.

An LED display provides a user-friendly interface for the end user which allows monitoring and/or modifying some of the main operating parameters. Two modes of operation are available and can be selected to allow either open-loop operation or closed-loop operation in synchronization with the grid.

In open-loop mode the sinusoidal reference is created internally by means of a standard lookup table, while in closed-loop mode, a sinusoidal voltage feedback, proportional to the grid voltage, is used. The system can be connected to either a 50 Hz or 60 Hz network, depending on local requirements. Finally, the RS-232 interface can be used for serial data transfer of specified voltage, current and current signals.

Features:

• 250 W power capability
  
• Input voltage range from 18 V to 45 V
  
• Output voltage Vout= 230Vac 50Hz -240Vac 60Hz
  
• Grid connection algorithm and MPPT capability
  
• MPPT efficiency (99%)
  
• Decoupled control of active and reactive power
  
• Overcurrent and anti-islanding protection
  
• RS-232 for communication
  
• Galvanic isolation between the panel and the grid