An energy storage system with bi-directional inverter

• Main Author: Tan, Shao Jie.
• Other Authors: So Ping Lam
• Format: Final Year Project
• Language: English
• Published: 2012
• Subjects: DRNTU::Engineering::Electrical and electronic engineering
• Online Access: http://hdl.handle.net/10356/47705
• Institution: Nanyang Technological University

The demand for energy will continue to increase as long as world population increases and people continue to demand a higher standard of living. The challenge lies in providing this energy from dependable and sustainable sources while maintaining respect for the environment. Renewable energy currently faces several drawbacks due to its intermittent nature. An energy storage system is needed to work with renewable energy sources in order to counteract intermittent generation. A battery bank that stores and generates DC power consists of a bi-directional buck/boost converter for charging and discharging of battery bank, and an inverter that converts DC power to clean and reliable AC electricity. This project is to aims to investigate and build a scaled down battery energy storage system based on V2G (Vehicle to Grid) Technology for PHEVs (plug-in hybrid electric vehicles). The design was required to utilize power electronics to interface a battery bank with the grid. The system was required to operate in two modes, “discharge mode” and “charge mode”. In the “discharge mode”, power is drawn from the batteries and injected into the grid. In the “charge mode”, power is drawn from the grid to recharge the battery bank without making any hardware changes during a “charge mode” of operation. Using the V2G bi-directional grid-tied system with sources tied to high and low buses, the converter inductor current direction verified that power can be transferred to and from the battery side. The half bridge topology was used to model the bi-directional buck/boost converter to step up and down the DC voltage. The H-bridge topology was used to model the bi-directional DC/AC inverter. It was capable of converting DC to AC and AC to DC respectively. The V2G bi-directional grid-tied system was simulated by connecting the buck/boost converter, H-bridge Inverter and a low pass filter. The results showed the system was capable of bi-directional power flow.The driver circuitry of the hardware implementation was successful after much linking up of CMOS and parasitic components purchased from R-S components and Farnell. The PWM signal was amplified to cater for the gate input of the IGBT. However, the IGBT is not working correctly for the buck/boost operation. The output of the buck/boost operation follows the input voltage instead of stepping up or down respectively. Therefore, the hardware implementation of Bi-directional DC-AC H-Bridge Inverter cannot be tested and verified.