The rapid growth of the transmission networks has brought more uncertainties and new requirements in the transmission expansion planning (TEP) to the planners. The existing methods of solving TEP problem have a drawback since the DC load flow and the relaxed load flow models have been utilized to solve TEP problem. In this work, the TEP problem is solved based on mixed integer nonlinear non-convex programming model. A meta-heuristic algorithm by the means of differential evolution algorithm (DEA) is employed as an optimisation tool. An AC load flow model is used in solving the TEP problem, where accurate and realistic results can be obtained. Furthermore, the work considers the constraints checking and system violation such as real and power generation limits, possible number of lines added and bus voltage limits. The proposed technique is tested on Garver's 6 bus system and IEEE 24 bus system and has shown high capability in considering the active and reactive power in the same manner and solving the TEP problem. The method produced improved results for the test systems. In terms of minimising the cost and the solution quality, the proposed method obtained good and challenging results comparing to the previous works.

Electricity tariffs convey information on internal system operation to the actors involved. Electricity pricing is, then, of major importance both in liberalised and regulated systems. Most electricity consumers interact with the industry only through the price they pay for the service. Consequently, good tariff design reflects industry regulation as a whole and is the instrument used to provide consumers with the right signals. The objective of this study is to define the theoretical principles that regulation should pursue in electric distribution tariff design and introduce the reader to the most relevant practical approaches that have been proposed or implemented. Although distribution costs are usually the largest part of the access tariff (or use of system charge), there is not a universally accepted methodology for distribution pricing. The earliest attempts at cost allocation conformed what is now known as the accounting approach, based on business accounting. In recent years, the proposals have focused on two approaches: the application of long-term marginal (or incremental) costs and the cost-causality principle. Although the former aims to achieve a better economic signal, because of the difficulties surrounding its implementation, the most usual solution applied in practice draws more heavily from the causality principle.

The detection of the source and severity of disturbances is important as this allows network companies to respond faster and remediate the problem more quickly. After an event, knowledge of the severity of a disturbance at various busbars gives understanding of what equipment was subjected to and an indication of possible improvements needed to mitigate further events. Owing to the cost, it is impractical to fully monitor the network, however, with judicious selection of measurement points, and using state estimation techniques, allows information at unmonitored locations to be determined. Hence, a cost effective detection system can be developed. This study documents a new three-phase transient state estimation algorithm and demonstrates its performance with realistic background harmonic voltage distortion and with measurement error. The transient state estimation is based on the numerical integrator substitution method (Dommel's method for discretising the differential equations).

This study presents a systematic method which enables large-scale alternating current (AC)/direct current (DC) power systems to be modelled in the electromagnetic transient (EMT) domain. A physical equivalence based dynamic reduction technique is first proposed to reduce the AC/DC system, which retains the backbone network and important components such as high-voltage direct current (HVDC) links, whereas the low-voltage networks connected to the backbone network are reduced to simple networks composed of physical components. The reduction technique is based on the preservation of the support strength of the generators within the low-voltage networks to the backbone network (i.e. the short-circuit current contribution level), the power flows within the backbone network and the total generating output. Then, a technique to construct the EMT model of the reduced AC/DC systems is developed based on the data in the transient stability program format. The validity of the proposed method is verified with the case of South China power grid, which includes a multi-infeed HVDC system.

This study presents a general approach to identify dominant oscillation modes in bulk power system by using wide-area measurement system. To automatically identify the dominant modes without artificial participation, spectral characteristic of power system oscillation mode is applied to distinguish electromechanical oscillation modes which are calculated by stochastic subspace method, and a proposed mode matching pursuit is adopted to discriminate the dominant modes from the trivial modes, then stepwise-refinement scheme is developed to remove outliers of the dominant modes and the highly accurate dominant modes of identification are obtained. The method is implemented on the dominant modes of China Southern Power Grid which is one of the largest AC/DC paralleling grids in the world. Simulation data and field-measurement data are used to demonstrate high accuracy and better robustness of the dominant modes identification approach.

This study proposes a local and decentralised load management procedure to provide frequency control support in power systems, without a complex communication network. In this context, the authors aim is to design and develop a new and innovative control algorithm using iterated mappings. Iterated mappings are obtained by local frequency measurements and are proved to be strong tools in dynamical deterministic systems’ analysis. The proposed algorithm is capable of assigning relevant operational states to power system during power contingencies; control action will then be exerted on that basis, with a simple and easy to implement data processing procedure. Efficiency of the control method is then verified by simulations in MATLAB environment.

Hybrid AC–DC microgrid is introduced as the future distribution network to utilise both benefits of alternative and direct currents. In such hybrid microgrid, AC and DC loads, renewable-based distributed generators (DGs), controllable DGs and energy storage systems are connected through separate AC and DC links. An up–down operation model of such hybrid microgrid is proposed which consists of system- and device-level. In the system-level, a mixed integer linear model is suggested to balance the generation and load considering the interconnection of AC and DC subgrids for minimising total operating cost of the system in a 24-hour period. In the device-level, a controller is suggested for power converter-based resources (i.e. intergrid inverter and battery) for controlling the voltage variations in AC and DC subgrids. The effectiveness of the proposed up–down operation model is demonstrated through simulation studies on a test hybrid microgrid.

Unified power flow controller (UPFC) is one of the multipurpose flexible AC transmission system devices which controls the transmission line parameters independently and simultaneously. This study presents a novel power flow controlling method based on terminal sliding mode control (TSMC) method using UPFC. The proposed controller has the advantages of finite-time convergence and chattering-free properties. A chattering-free state variable controller is designed and employed to address the problems of reference tracking, robustness against uncertainties and disturbances performance of the proposed controller is compared with an existing sliding mode controller (SMC) and a PI controller. Chattering phenomena and discontinuity of the sliding mode controller are also eliminated. Another objective of the proposed control scheme is to use only locally-measurable states, and to avoid remote long distance measurements. An adaptive observer is used to estimate the receiving end bus voltage, to avoid the data transfer problems over long distances, and to fulfil advantages such as fault detection and isolation. The presented observer could also be used to estimate the measurable states of the system. Simulation results demonstrate the efficiency of the proposed controllers. It is shown that the convergence time of the proposed TSMC is lower than those of the SMC and PID controllers’. Stability of the proposed controllers is mathematically proved. The performance of the presented adaptive observer, in the noisy environment, is also evaluated by simulation. Finally, simulation results of the suggested controllers under transient states and faulty conditions are presented.

The decomposition of locational marginal price obtained from AC optimal power flow is disputable because of its dependency on the choice of energy reference. The dispute arises because the difference of congestion component, on which the Financial Transmission Rights (FTR) payments are made, is not constant and depends on the energy reference. Prior art aimed at obtaining reference-independent decomposition. The authors look at this dispute as a fairness issue and formulate the decomposition as a fairness problem. The fairness issue is addressed by invoking max–min fairness criteria which ensures that the FTR payment (FP) received (made) is not at the expense of other ill-positioned FTR holders. Max–min fairness algorithm is used to arrive at an energy reference choice that aims at maximising the FP of each FTR. This in turn ensures that revenue received (payment made) is the maximum (minimum) possible under the set of constraints, without adversely affecting the FP of other FTR holders. Results on PJM 5 bus and IEEE 30 bus systems indicate that a fair solution is indeed possible.

Gas turbines inherently depict unique frequency response characteristics compared with other conventional synchronous generation technologies as their active power output is not entirely determined by the governor response during frequency deviations of the power network. Thus, gas turbine dynamics significantly influence on system stability during frequency events in power networks. Power system and power plant operators require improved understanding of the gas turbine characteristics during various frequency events in order to mitigate adverse impact on power system. Therefore a comparative analysis has been performed between combined-cycle gas turbines (CCGTs) and open-cycle gas turbines (OCGTs) in order to characterise the dynamic behaviour considering different types of frequency events in power networks. Study has shown that CCGTs result in significant frequency variations in power networks in comparison with OCGTs because of the temperature control action performed by the fast acting inlet guide vanes at the combustor. In particular, they are susceptible to lean blowout during large frequency increase events such as short-circuit faults in power networks. Furthermore, a case study was developed based on the New England-39 bus system in order to illustrate the impact of gas turbine dynamics on network frequency during short-circuit events in power networks.

This study investigates the physical mechanism of ferroresonance and its control. Based on this mechanism, a flexible control method for ferroresonance is proposed, and its control mechanism is discussed. High-frequency controllable switches are used in the control module proposed in this study, and several parameters of the control module can be adjusted according to ferroresonance types identified by the comprehensive identification system and saturation degrees of the ferroresonance. The control module is then switched into the secondary circuit of the potential transformer, and ferroresonance can be controlled. Simulation and experimentation show that ferroresonance of various types and saturation degrees can be restrained.

A novel approach of transmission tariff allocation (TTA) is proposed in this study. TTA comprises scheduled incremental cost (SIC) and unscheduled interchange cost (UIC) components. This approach demonstrates the use of proposed SIC and UIC components of tariff in incremental revenue reconciliation along with the provision of heavy penalty to maintain the grid discipline against extreme unscheduled withdrawal. SIC has been allocated to users of transmission network for their scheduled injections or withdrawals. UIC take care of excessive unscheduled interchange (UI) in load or generation. Incremental power flow in MVA is used to asses and allocation of these components. The scheduled increment (SI) in load or generation is associated with planned load growth rate whereas the UI in load or generation may arise intermittently. All generating units are participating to generate both active and reactive power as per their generation participation factor to match the SI and UI demands. The SIC component may be added to the nominal TTA to user. The UIC component of tariff is an additional burden or penalty imposed on users because of extreme unscheduled withdrawal. The results are obtained for SIC and UIC components of TTA by using 6 bus and IEEE 14 bus systems.