Coordination control of hybrid AC/DC building microgrid

• Main Author: Zhu, Dexuan
• Other Authors: Chan Siew Hwa
• Format: Theses and Dissertations
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Power electronics
• Online Access: http://hdl.handle.net/10356/71914
• Institution: Nanyang Technological University

Advantages such as environmental friendliness and flexibility have made microgrid an attractive option for in modern power systems. Microgrid is a localized grouping of distributed generators, storages and loads. Microgrid integrates with sustainable energy sources could reduce carbon emission. A microgrid can serve specific purposes, such as to enhance reliability, diversification of energy sources, and cost reduction. Therefore, microgrid has been introduced into building distributed networks as it makes both power generation and consumption more efficient. In order to obtain better power conversion and utilization efficiency, the configuration, control strategy, and energy management of building microgrid need to be further studied. This thesis introduces the overall configuration of building microgrid and the specific subsystem controllers in a building microgrid. Microgrid configuration, operation and control have been investigated for many years. Various microgrid configurations for building distributed networks have been proposed with each claiming some aspects of improvements. To achieve better energy efficiency, a novel hybrid building microgrid is introduced in this thesis. A building photovoltaic system (BPVS), a building motor drive system (BMDS) and a hybrid building energy storage system (HBES) are introduced respectively based on the common features among PV systems, motor driving circuits and various energy storages. The objective of the building hybrid microgrid (BHMG) is to improve building’s energy efficiency through reducing multiple reverse conversion loss in conventional building distributed networks (CBDN), to achieve more efficient connection of subsystems, and to reduce building energy consumption and peak power demand through power generation from BPVS and power regeneration in BMDS. In building microgrid, motor drives are essential devices and widely used in lifts, air-conditioning and water pumping systems. In a high rise commercial building, lift motors not only consume energy but also regenerate energy. A building’s lift system is proposed to classify and integrate all lifts together to improve the efficiency in the building’s energy utilization. A novel distributed lift control approach based on fuzzy logic and DTC is proposed in this chapter to integrate lift operating system optimization and motor control. The objective of the novel control system is to choose the lift which makes the waiting & riding time shorter and consumes less power, and it can even regenerate power and channel back into energy storage. The motor controller with self-tuning has a smaller ripple and shorter response and recovery time. By using this controller, the power efficiency in high rise multi story building can be improved. Another essential component in building microgrid is energy storage. Different types of energy storages with high power density and high energy density have to operate under different modes like voltage regulation and power exchange. An adaptive area droop control approach has been proposed to demonstrate an autonomous mode change and a stable operating performance for energy storage converters. The coordination control is introduced to reduce the battery charging/discharging times of miner cycle and discharge depth. Plug-in hybrid electric vehicle (PHEV) is gaining popularity in today's automotive market and more charge stations for PHEV are installed in commercial buildings. The conventional charge circuit can only produce an output DC voltage that is higher than the peak AC input voltage. An efficient single-phase PFC converter that features sinusoidal input current, three-level output characteristic and flexible output DC voltage is introduced to cater for variable voltage levels of the battery pack (50V-600V). The charging efficiency is improved since it is partially contributed by the reduced switching voltage in the PFC stage, and also partially by the reduced power conversion in the DC/DC buck stage. All design configurations and control algorithms have been thoroughly verified in MATLAB/Simulink and PLECS. Suitable experimental prototypes have been built in the laboratory for validating the practicalities of all theoretical findings.