Edward Christopher

Investigating the effects of dynamic demand side management within intelligent Smart Energy communities of future decentralized power system

This paper firstly discusses the benefits of transforming conventional power system into decentralized systems which are composed of clusters of smart energy communities, supplied mainly by renewable energy sources. Application of Demand Side Management within such communities has been identified as a necessity to account for the required degree of active management in such dynamic systems. The intelligent Smart Energy Community project and its concepts have been discussed. An electricity demand model has been created and used to firstly determine the appropriate size of a community for implementation of an effective and non-disturbing load shifting demand side management. The model is then utilized to quantify the potential benefits of applying load shifting demand side management with a variable severity level.

Coordinated optimal dispatch of distributed energy resources within a smart energy community cell

A hierarchical control structure for optimal dispatch of distributed energy resources within different levels of the distribution network has been presented and a deterministic optimization and agent coordination algorithm has been proposed for optimizing the operation of flexible resources at the community cell level. Coordinated optimal dispatch of resources ensures that only the required number of loads/resources are dispatch at every moment, which contributes towards alleviating simultaneous load reconnection which would otherwise occur if all loads/resources were dispatched independently (in an uncoordinated manner). It has also been shown in this paper how number of cold loads and a community storage unit, could be dispatched in a coordinated and cooperative manner to contribute towards the objective function of maintaining the communitys power flow below a pre-specified threshold.

Fault location in a zonal DC marine power system using Active Impedance Estimation

Momentum is gathering on the development of dc power systems for naval platforms. However, the necessary accurate location and isolation of faults within the zonal distribution system remains a challenge. The method of “foldback” is an example of a technique which has been developed to exploit the fast control of the supply power converters to maintain bus currents to within acceptable levels. Techniques such as this need to be supported by equipment which can classify and localize the fault, so the fault can be cleared and the system can be reconfigured. A new technology - active impedance estimation - is presented which offers benefits to future marine power systems, and its application to dc zonal distribution systems is discussed. Experimental results from a dc system demonstrator show the potential of the new technique for fault location.

Series Arc fault studies and modeling for a DC distribution system

Electrical arcs are of great concern for power electronic systems. Modeling of arc faults to represent and predict arc characteristics and transient responses within the power system is now receiving considerable research attention. In this paper, a series DC arc fault demonstration rig is designed to generate series arcs by moving one electrode away from a stationary one with a stepper motor. Experimental results presented and analyzed to obtain the arc fault characteristics. The arc voltage, arc current and arc power can be predicted using the Zeller model within a wide range of supply voltage, load conditions and different test conditions, such as electrode material. The verification of this model is important as it can now be included in simulations of complex power systems to aid the development and testing of robust arc fault detection and location strategies.

Real-time battery management algorithm for peak demand shaving in small energy communities

One of the solutions to tackle the problems of high peak demand and grid instability due to high photovoltaic (PV) power penetration is to deploy a battery storage system. This paper presents a real-time battery management algorithm (BMA) for peak demand shaving in small energy communities with grid-connected PV systems. The BMA aims to control the charge/discharge of the community battery storage using measurement of the instantaneous power consumption of the community. Historical data records of community daily energy consumption and available renewable energy are taken into account to manage the charge/discharge of the battery. Simulation results show the effectiveness of the BMA which is able to reduce the peak energy consumption by 35%, increase PV self-consumption by 47% and reduce transmission line losses during the peak period by 56% when compared to a PV system without the battery storage.

Microgrid unbalance compensator - Mitigating the negative effects of unbalanced microgrid operation

A shunt connected three-phase four-leg power electronic-based compensator is proposed which allows the microgrid to behave as a “good citizen” from the viewpoint of the utility even though the microgrid itself is operating under highly unbalanced conditions. The same compensator when interfaced to a synchronous generator-based micro-generation unit can also be utilized to significantly reduce the double system frequency (100 Hz) power oscillation component arising due to unbalanced loading which can accelerate generator wear. This paper presents the compensation strategies, control algorithm and structure of the compensator. In addition, experimental results are presented which validate the compensator design.

Energy management research using emulators of renewable generation and loads

A laboratory based microgrid test facility is described which uses emulation systems to represent a variety of renewable generation and load types. The emulation systems use real time data from a small housing estate and a 9kW wind turbine to provide a safe, versatile and realistic testbed for the development of energy management techniques for small communities. The paper describes the facility and also two control techniques for energy and power quality management within an energy community.

Fault location for a DC zonal electrical distribution systems using active impedance estimation

One of the most important issues that need to be resolved before DC power systems are feasible to be introduced as architectures for naval marine power systems (MPS) is the protection of the system against faults. Techniques are being developed to control fault current levels by fast acting control using power electronic systems. These techniques need to be supported by a system that classifies and localizes the fault, so the fault can be cleared and the system reconfigured. Active Impedance Estimation (AIE) can be used to provide information on both fault severity and fault location such that the power system can be correctly reconfigured. This paper describes a 50kW five zone, two bus, DC system demonstrator and presents initial results which show how AIE can be used to inform a MPS reconfiguration algorithm to achieve system “self healing” in the event of bus faults.

A DC distribution demonstrator incorporating Active Impedance Estimation for marine applications

A small scale laboratory demonstrator has been constructed to represent a zonal DC distribution system as proposed for future naval vessels. This paper describes how the demonstrator has been used to validate a proposed fault location strategy — Active Impedance Estimation (AIE) — under experimental conditions. The practical processing algorithms required to reduce the effect of noise and the background supply harmonics are presented. The experimental results validate the AIE approach and confirm its robustness and accuracy.

Voltage Balance Control for a Multilevel Interface for Renewable Energy Systems

This paper presents a new method to balance the DC link voltages in a 3 level Diode Clamped Rectifier, even in the presence of unbalanced loads which cause a non-zero neutral point current. The method employs an offset which is added to each of the inverter modulation waves. This offset causes a zero sequence voltage which can drive the desired neutral point current whilst maintaining balanced DC link voltages. Simulation and experimental results confirm the method.