Protection and energy management of zero net electric energy clusters of buildings

This paper proposes the protection and energy management schemes for a smart dc micro-grid capable of 100% autonomous zero net energy in the cluster of buildings to facilitate a low-carbon sustainable electricity supply system. The proposed model comprises of house clusters with an autonomous communication developed for the residential area. Voltage droops and slope compensation peak current mode control techniques are employed for the bidirectional synchronous boost converter stages for energy storage systems (ESSs). The zone relaying device pertaining to dc protection is incorporated under set of rules related to current differential and overt current relaying schemes. The bidirectional converter stage for house clusters plays a pivotal role in stand-alone operation. In case a battery pack is laid off from any house cluster, the dc bus voltage still be stabilized due to the proximity bidirectional converter stages of other house clusters or community battery bank. The houses in the cluster comprise of permanent magnet synchronous generator (PMSG), solar photovoltaic (PV), battery bank and variable load. The proposed model is simulated on MATLAB/ Simulink environment and suffices the real time stochastic nature of wind, solar and load

Development of a multi-port DC-DC converter for a magnetically-coupled residential micro-grid

University of Technology Sydney. Faculty of Engineering and Information Technology.Over the last century, the global average air temperature at the earth surface has been raised for about 0.74ºC, which has generated serious concerns all around the world about the global warming and consequent environmental problems. The electricity generation as one of the major contributors to the environmental pollutions should undergo a fundamental change towards the clean energy sources. In the residential sector, one of the major electricity users, the demand for renewable energy sources is increasing significantly. This thesis presents an effort to develop a residential micro-grid, including multiple renewable energy sources, energy storage, and local loads with multiport power electronic converters capable of bidirectional power flow and intelligent algorithms for power converter and micro-grid controls. A topology of multi-port converter using a high frequency magnetic link is proposed for residential micro-grid applications. Using the magnetic link in the proposed multi-port converter can reduce the complexity and size of the entire micro-grid effectively. The micro-grid is designed to supply a 4.5 kW residential load from combined energy sources of a PV array, a fuel cell stack, and a battery bank. It is controlled by a Texas instrument DSP (C2000/TMS320F28335) at the device level and a PC system as the energy management unit (EMU) at the system level. A single phase bidirectional inverter is designed to link the proposed micro-gird to the main grid. The inverter is controlled by a second DSP at the device level and by the EMU at the system level. The proposed micro-grid is able to operate in different operation modes based on the power flow directions and energy management scenarios. The EMU defines the appropriate operation mode of the system based on the short-term and long-term predictions of PV generation, and load demand by changing the power flow directions between the sources, energy storage unit, and loads. Due to the importance of the magnetic link in the micro-grid performance and complexity of design of high-frequency multi-winding magnetic components, a major part of the research is focused on the design, development and experimental test of the magnetic link. The geometry of the magnetic link including the dimensions of magnetic core and windings are designed through numerical analysis by using the reluctance network model (RNM). The core loss and copper loss analysis of the magnetic link are carried out accurately considering the non-sinusoidal effect of voltage and current waveforms. The designed component is then evaluated for the thermal limits by using the thermal electric model. The last part of this stage is the prototyping, experimental tests, and measurement of the component parameters and performance. The second part of the research is mainly focused on the design and analysis of the converters as the device level analysis of proposed micro-grid. It contains the analysis of the three dc-dc converters in the steady and transient states, discussion on the modulation technique of each converter, power flow control techniques, small signal modelling, and closed loop control design. The converter steady state waveforms are simulated and the soft-switching operation range is discussed. The converter waveforms are experimentally measured and compared with the numerical simulation results. The third part of the research is dedicated to the system level control of the micro-grid and energy management analysis. In this section, the main operation modes of the system are defined for both grid-connected and isolated operation conditions according to the power flow directions in the system. An energy management strategy is proposed considering both the short- and long-term energy forecasts and the real-time operational data of the system. The proposed strategy is implemented in an energy management unit using MATLAB/GUI and is used to control the system operation modes considering different control objectives and scenarios

Architectures for smart end-user services in the power grid

Abstract-The increase of distributed renewable electricity generators, such as solar cells and wind turbines, requires a new energy management system. These distributed generators introduce bidirectional energy flows in the low-voltage power grid, requiring novel coordination mechanisms to balance local supply and demand. Closed solutions exist for energy management on the level of individual homes. However, no service architectures have been defined that allow the growing number of end-users to interact with the other power consumers and generators and to get involved in more rational energy consumption patterns using intuitive applications. We therefore present a common service architecture that allows houses with renewable energy generation and smart energy devices to plug into a distributed energy management system, integrated with the public power grid. Next to the technical details, we focus on the usability aspects of the end-user applications in order to contribute to high service adoption and optimal user involvement. The presented architecture facilitates end-users to reduce net energy consumption, enables power grid providers to better balance supply and demand, and allows new actors to join with new services. We present a novel simulator that allows to evaluate both the power grid and data communication aspects, and illustrate a 22% reduction of the peak load by deploying a central coordinator inside the home gateway of an end-user

Distributed multi-agent algorithm for residential energy management in smart grids

Distributed renewable power generators, such as solar cells and wind turbines are difficult to predict, making the demand-supply problem more complex than in the traditional energy production scenario. They also introduce bidirectional energy flows in the low-voltage power grid, possibly causing voltage violations and grid instabilities. In this article we describe a distributed algorithm for residential energy management in smart power grids. This algorithm consists of a market-oriented multi-agent system using virtual energy prices, levels of renewable energy in the real-time production mix, and historical price information, to achieve a shifting of loads to periods with a high production of renewable energy. Evaluations in our smart grid simulator for three scenarios show that the designed algorithm is capable of improving the self consumption of renewable energy in a residential area and reducing the average and peak loads for externally supplied power

Protection and energy management of zero net electric energy clusters of buildings

This paper proposes the protection and energy management schemes for a smart dc micro-grid capable of 100% autonomous zero net energy in the cluster of buildings to facilitate a low-carbon sustainable electricity supply system. The proposed model comprises of house clusters with an autonomous communication developed for the residential area. Voltage droops and slope compensation peak current mode control techniques are employed for the bidirectional synchronous boost converter stages for energy storage systems (ESSs). The zone relaying device pertaining to dc protection is incorporated under set of rules related to current differential and overt current relaying schemes. The bidirectional converter stage for house clusters plays a pivotal role in stand-alone operation. In case a battery pack is laid off from any house cluster, the dc bus voltage still be stabilized due to the proximity bidirectional converter stages of other house clusters or community battery bank. The houses in the cluster comprise of permanent magnet synchronous generator (PMSG), solar photovoltaic (PV), battery bank and variable load. The proposed model is simulated on MATLAB/ Simulink environment and suffices the real time stochastic nature of wind, solar and load