M.R. Irving

A genetic algorithm for generator scheduling in power systems

This paper presents a genetic algorithm based approach to the scheduling of generators in a power system. All the usual unit commitment constraints including ramp rates are considered. An enhanced genetic algorithm incorporating a sequential decomposition logic is used to provide a faster search mechanism. The main advantage of the genetic algorithm formulation is that fairly accurate results can be obtained with a very simple algorithm. The algorithm has been tested on a power system with 26 generators.

Large scale unit commitment using a hybrid genetic algorithm

Abstract In the new competitive electricity supply industry, there is a renewed interest in algorithms that can provide savings in operation costs. An optimal scheduling of generators can provide substantial annual savings in fuel costs, but this highly constrained non-linear mixed integer optimisation problem can only be full v solved by complete enumeration, a process which is not computationally feasible for realistic power systems. In the recent past, evolutionary computation techniques have been applied to the solution of the unit commitment problem, but when implemented as stand alone systems, they suff er from computational time limitations, especially when the systems are scaled up. This paper proposes a hybridgenetic algorithm incorporating a priority list unit ordering scheme to solve the generator scheduling problem. Test results on networks with up to 110 generators are presented and the results demonstrate the viability of the hybrid GA method for unit commitment in realistic power systems.

Plug in to grid computing

This article discusses the potential benefits of grid computing for future power networks. It is also intended to alert the power system community to the concept of grid computing and to initiate a discussion of its potential applications in future power systems. Much like the Web, the grid can operate over the Internet or any other suitable computer networking technology. Grid computing offers an inexpensive and efficient means for participants to compete (but also cooperate) in providing reliable, cheap, and sustainable electrical energy supply. It also provides a relatively inexpensive new technology allowing the output of embedded generators to be monitored and, when necessary, controlled. Basically, the ability of grid-enabled systems to interact autonomously is vital for small generators where manned operation is likely to be viable.

Flow Batteries for Enhancing Wind Power Integration

Providing frequency response capability from wind farms is technically feasible, but relies on spilling the wind. Wind intermittency and the planned expansion in offshore wind power in the U.K. are expected to lead to increased requirements for frequency response capability. This may necessitate times where wind farms operate in a frequency sensitive manner and output only a proportion of the available power. Compensating for spilt wind energy would likely lead to increased costs of balancing the power system. This paper highlights the alternative to spilling wind to provide frequency response capability: using wind farm level energy storage. The Vanadium Redox Flow Battery is shown to be capable of providing this and other benefits to the wind farm. The work further demonstrates that ίow batteries could often be incorporated with reactive power compensation equipment such as a wind farm level IGBT SVC. The control of the power electronic interface of the battery is introduced and a control method for supporting the dc link under grid faults is developed and simulated. This control is shown to give the added benefit of supporting the fault current contribution through an extended and severe fault. The capability of the Vanadium Redox Flow Battery to enhance power and energy applications is then explored by considering integrated control with a wind farm to energy time shift and provide frequency response. A novel controller is introduced, which manages the state of charge of the ίow battery while providing some output smoothing to the wind farm and a variable level of reserve for the power system. The simulations of this controller also demonstrate that the energy store can be used to time-shift some of the wind farms energy to times of higher prices.

A Cost Allocation and Pricing Method for Reactive Power Service in the New Deregulated Electricity Market Environment

It is necessary to restructure the reactive power pricing framework. The exchange of real energy is the dominant intention of the electric power exchange and the reactive power has its inherent limitation, but the importance and stimulation effect of a effective reactive power cost structure is important also, especially to the performance of the power market, the quality of electric power exchange and the security of the power system. All this tell us that reactive power should be treated as more than a subsidiary factor

Supply restoration in distribution networks using a genetic algorithm

Abstract The distribution network supply restoration problem is to reconfigure the network, after a line removal due to fault, such that loss of supply to customers is minimised, while ensuring that current loading and voltage excursions do not exceed permitted levels, and minimising the network loss at minimum switch operation cost. A genetic algorithm is employed to solve this multi-objective constrained optimisation problem. Instead of the standard binary string, the ‘integer permutation’ encoding scheme is adopted with each integer representing one controllable switch. Graph theory is employed to decide the final status of each switch according to the radiality constraint. The objective function of the GA incorporates all the objectives and constraints required for the supply restoration scheme. A special gene is introduced to search for optimal load shedding in the situation where it is necessary. The proposed algorithm is tested on a 114-switch system that is part of a practical distribution system, and promising results have been obtained.

Coordinated voltage control for active network management of distributed generation

Existing approaches to the design, control and operation of 11 kV distribution networks often restrict optimal utilization. When confronting the increasing demand and growing amount of distributed generation being connected to the networks, it is essential for distribution system operators to employ new and more active network management practices. This paper presents and discusses a range of active voltage management schemes based on coordinated voltage control. These schemes can be used to improve the voltage profile in 11kV distribution networks and increase their ability to accommodate distributed generation. Technical limitations and commercial barriers are discussed. Two case studies based on EDF Energy distribution systems are presented. Both systems experienced voltage issues associated with the presence of distributed generation and innovative active control scheme trials have been installed. The functionality of each scheme is assessed based on a number of factors such as: ability of the scheme to increase network capacity, reliability and accuracy.

Novel application of detrended fluctuation analysis for state estimation using synchrophasor measurements

The phasor measurement unit (PMU), with its ability to directly calculate synchronized positive sequence voltages and currents (magnitude and phase), offers a more current and accurate view of the power system compared to that provided by traditional measurements and state estimation (SE). However, the high-resolution data, provided at rates of 50 Hz and 60 Hz (dependant on nominal frequency), capture any transient or dynamic events occurring on the network, potentially distorting the intended steady-state view at various points of the power system. In this paper we propose the use of detrended fluctuation analysis (DFA) to detect and isolate such events for alternative investigation. Comparisons are made between the state estimator and installed PMUs on the high-voltage transmission system of Great Britain.

An approach based on the strength pareto evolutionary algorithm 2 for power distribution system planning

The vast majority of the developed planning methods for power distribution systems consider only one objective function to optimize. This function represents the economical costs of the systems. However, there are other planning aspects that should be considered but they can not be expressed in terms of costs; therefore, they need to be formulated as separate objective functions. This paper presents a new multi-objective planning method for power distribution systems. The method is based on the Strength Pareto Evolu-tionary Algorithm 2. The edge-set encoding technique and the constrain-domination concept were applied to handle the problem constraints. The method was tested on a real large-scale system with two objective functions: economical cost and energy non-supplied. From these results, it can be said that the proposed method is suitable to resolve the multi-objective problem of large-scale power distribution system expansion planning.

Admittance matrix models of three-phase transformers with various neutral grounding configurations

Nodal admittance matrix models are obtained for wye-connected three-phase transformers with various grounding impedance configurations. The derivations have been performed using computational symbolic algebra, avoiding the necessity for simplifying assumptions. An original model for the general case of a wye-wye transformer, with grounding impedances on both primary and secondary neutrals, is given. It is shown that this model does not correspond to the simple combination of the previously known formulae for cases where neutral impedance occurs on either the primary side only or the secondary side only. It is also demonstrated that the new model simplifies to the well-known limiting cases for solid grounding and no grounding. A model is also given for multiple transformers sharing a single neutral grounding impedance.