Energy Management System for PV-Battery Integrated Module

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Abstract

Transition from fossil fuels to renewable sources is desired by both developed and developing countries due to the environmental concern and rapid technological developments. Governments, consumers, and investors have seen the prospect of Photovoltaic (PV) as a prominent technology to fulfill the electricity demand. For the residential-scale PV system,costs of the PV module(s) and the BoS (Balance-of-System) are usually the issue that discourage the consumers from installing PV system in their households. To tackle this issue, the concept of PV-Battery Integrated Module (PBIM) is developed. The operations of the PBIM are similar with typical operations of PV-battery system, which are controlled by the energy management unit. Energy Management System (EMS) is responsible for ensuring the safety of the electrical components and controlling the system operations to make it efficient. Therefore,implementing the suitable EMS is an integral part of establishing the PBIM system.

This research aims to implement a power flow management for the PBIM system to perform two energy management strategies, namely peak shaving and off-grid self-consumption. To achieve that goal, this research focus on selecting the PBIM system architecture, implementing control system and power flow management, and analyzing PBIM system performance on the applications of peak shaving and off-grid self-consumption strategies. Two case studies are introduced in this thesis, namely off-grid PBIM in Cambodia and grid-connected PBIM in the Netherlands.

The chosen system architecture for the PBIM is the DC couple architecture. The PBIM system consists of one PV module, one unidirectional boost converter to perform MPPT and curtail operation, one bidirectional buck-boost converter to handle charging and discharging operation, an inverter to connect the PBIM with an AC load, and a battery bank. There are seven modes of operation in the PBIM system, which are utilized to perform peak shaving and off-grid self-consumption strategies.

For the off-grid PBIM in Cambodia, a 265Wp module and 8 batteries are used. The PV curtail operation is performed mostly during dry season, due to high irradiance. The LLP during rainy season (4%-7%) is much larger than the LLP during dry season (1%-3%), due to big difference in the irradiance between those two seasons. The total LLP for one year operation is 2.6%.

For the grid-connected PBIM in The Netherlands, a 265Wp module and 8 batteries are also used. The peak shaving is performed in this case, hence the battery is being charged during off-peak hours, and the load is supplied by the grid. During peak-hours, the load is supplied by the PV, battery, and the grid. For one PBIM, the system autarky can only a maximum of 16%, hence multiple PBIMs are required to increase the PBIM system autarky for the grid-connected PBIM in the Netherlands.