Development and prototype validation of a novel Bidirectional Intelligent Conversion and Connection Unit (BICC) for grid-connected photovoltaic-storage systems

This paper presents studies and the implementation of a novel grid-connected PV system with storage. The goal of this project is to validate the operation and to determine the benefits and limitations of integrating storage with grid-connected PV systems. The objective is to evaluate the viability of using complementary electricity storage for meeting the local evening peak demands - “night-time peak shaving” in a typical load curve of CEMIG´s feeder. A novel and versatile control unit-the Bidirectional Intelligent Conversion and Connection Unit (BICC)-has been developed to control the flow of energy from the electricity sources (i.e., PV generator, battery bank, and electric-power grid). In designing this electronic system, we adopted a topology in which the inverter and the maximum power tracking (MPPT) optimize the available power by incorporating two separate and independent converters. In the first phase of the project, a prototype of the system that includes PV with storage and the BICC unit has been installed at GREEN Solar-IPUC in PUC Minas and been under test to evaluate its performance. These trials have been used to optimize system parameters in order to improve the BICC and its interfacing parameters and ensure safe operation of PV-storage system with the grid. This paper reports on the design and advantages of the BICC, the procedures used in the parameter optimization of the prototype, the effectiveness of the BICC in improving the control and connection, conformity to standards, and the viability of scale up for the second phase testing connected to the electric grid (for the utility CEMIG) with storage at the football stadium, Arena do Jacare, located in Sete Lagoas, Minas Gerais.