• Energy Research

Abstract Due to random connection of small-size single-phase rooftop photovoltaic (PV) generators in residential areas, low voltage distribution systems tend to have unbalanced PV integration across phases. In such situations, traditional reactive power compensation methods may cause unintended Voltage-Reactive Power responses across phases due to line coupling, which consequently affects their effectiveness on overvoltage mitigation. Such overvoltage problems significantly hinder the future integration of clean and renewable solar energy resources in power networks. In this paper, the limitations of traditional methods in PV imbalance scenarios are revealed and comprehensively analyzed by a voltage sensitivity method for the first time. On this basis, an innovative joint centralized-decentralized method is developed to overcome the PV imbalance-induced voltage regulation challenge. Specifically, the inverter’s reactive power response to PV power variations in different phases is adaptively scheduled in order to avoid adverse effect of inter-phase Voltage-Reactive Power interaction on voltage regulation. The effectiveness of the proposed method is validated by time-series simulations with recorded data and a real-life low voltage distribution system in Australia. With the traditional method (i.e. power factor droop control strategy), 93 minutes’ overvoltage can be observed in the case study, which will trigger overvoltage protection and disconnect PV inverters from the grid. While, the proposed method can always control the system voltage within the allowable range, and it consequently avoids PV disconnection. By solving this bottleneck issue, more PV systems can be integrated into distribution networks, which consequently contributes to CO2 emission reduction in future.

This paper studies social cooperation backed peer-to-peer energy trading technique by which prosumers can decide how they can use their batteries opportunistically for participating in the peer-to-peer trading. The objective is to achieve a solution in which the ultimate beneficiaries are the prosumers, i.e., a prosumer-centric solution. To do so, a coalition formation game is designed, which enables a prosumer to compare its benefit of participating in the peer-to-peer trading with and without using its battery and thus, allows the prosumer to form suitable social coalition groups with other similar prosumers in the network for conducting peer-to-peer trading. The properties of the formed coalitions are studied, and it is shown that 1) the coalition structure that stems from the social cooperation between participating prosumers at each time slot is both stable and optimal, and 2) the outcomes of the proposed peer- to-peer trading scheme is prosumer-centric. Case studies are conducted based on real household energy usage and solar generation data to highlight how the proposed scheme can benefit prosumers through exhibiting prosumer-centric properties. Single column, double space, 24 pages

Peer-to-peer trading in energy networks is expected to be exclusively conducted by the prosumers of the network with negligible influence from the grid. This raises the critical question: how can enough prosumers be encouraged to participate in peer-to-peer trading so as to make its operation sustainable and beneficial to the overall electricity network? To this end, this paper proposes how a motivational psychology framework can be used effectively to design peer-to-peer energy trading to increase user participation. To do so, first, the state-of-the-art of peer-to-peer energy trading literature is discussed by following a systematic classification, and gaps in existing studies are identified. Second, a motivation psychology framework is introduced, which consists of a number of motivational models that a prosumer needs to satisfy before being convinced to participate in energy trading. Third, a game-theoretic peer-to-peer energy trading scheme is developed, its relevant properties are studied, and it is shown that the coalition among different prosumers is a stable coalition. Fourth, through numerical case studies, it is shown that the proposed model can reduce carbon emissions by 18.38% and 9.82% in a single day in Summer and Winter respectively compared to a feed-in-tariff scheme. The proposed scheme is also shown to reduce the cost of energy up to 118 cents and 87 cents per day in Summer and Winter respectively. Finally, how the outcomes of the scheme satisfy all the motivational psychology models is discussed, which subsequently shows its potential to attract users to participate in energy trading. 7 Figures, 5 Tables, Accepted in Applied Energy

The installed capacity of wind generation and photovoltaics (PV) in many countries is going to dominate generation fleets in a bid to meet growing renewable energy targets. Synchronous inertia has never been problematic as there was more available than needed, but it is being significantly reduced due to the increasing integration of nonsynchronous renewable generation. When the low bidding priced generation of wind and PV becomes considerably large, conventional economic dispatch algorithms can result in less online synchronous inertia and put power system security at risk. However, the compromise of power system security due to synchronous inertia shortage is not well studied in the literature. This paper develops a synchronous inertia constrained economic dispatch algorithm to satisfy the minimum required synchronous inertia of frequency control. Synchronous condensers and wind reserve are economically allocated to alleviate any shortage of synchronous inertia and frequency control ancillary services (FCAS). A Gaussian particle swarm optimization algorithm is introduced to simultaneously co-optimize the dispatch of synchronous generators and their FCAS, wind reserve, and synchronous condensers.

In this paper, a nonlinear static var compensator (SVC) controller is proposed to improve power system voltage stability. A third order nonlinear dynamical description for the SVC system is developed and used in the controller design. Adaptive and robust control techniques are employed to deal with both constant and time varying uncertainties in a power system with SVCs. The effectiveness of the controller on voltage stability enhancement is demonstrated by a three-bus power system. The simulation results show that the time toward voltage collapse can be avoided which would otherwise happen without the controller. This validates the effectiveness of the proposed nonlinear robust adaptive controller in voltage stability enhancement.

This paper proposes a decentralized control strategy for higher penetration of photovoltaic (PV) units without violating system operating constraints. A systematic procedure is developed and a robust controller is designed to ensure both dynamic voltage and transient stability for a specific PV integration level. The change in the model due to the volatile nature of PV generations is considered as an uncertain term in the design algorithm. Simultaneous output-feedback linear quadratic controllers are designed for PV generators. This designed control scheme is robust with respect to intermittency and enhances the integration level in a sub-transmission and distributed system. The effectiveness of the proposed controller is verified on a 43-bus industrial meshed distribution system under large disturbances. It is found that the designed control scheme enhances stability and increases the renewable integration levels.

Abstract A new demand response (DR) scheme from the retailers’ point of view is presented in this paper. The proposed DR scheme allows a retailer to decide how to buy DR from aggregators and consumers. Various long-term and real-time DR agreements are proposed, where they are considered as energy resources of retailers in addition to the commonly used providers. These innovative agreements include pool-order options, spike-order options, forward DR contracts and reward-based DR. A stochastic energy procurement problem for retailers is formulated, in which pool prices and customers’ participation in the reward-based DR are uncertain variables. The feasibility of the problem is assessed using a realistic case of the Queensland jurisdiction within the Australian National Electricity Market (NEM). The outcomes indicate the usefulness of the given DR scheme for retailers, particularly for the conservative ones.

This paper presents the development and application of an analytical method for formalizing the dependence of the behavior of a large power system under fault conditions on the equivalent impedance presented by a single generator. After selecting an appropriate generator model, it is demonstrated that network-wide fault behavior can be expressed as a rational function of the equivalent impedance presented by a single generator under fault conditions. This representation simplifies the identification and depiction of constraints imposed by system configuration on the ability of a generator replacement or augmentation to affect fault behavior. The effectiveness of the proposed method is confirmed by considering the three-phase fault currents produced in a six-bus test system. In addition, the new analytical method is extended to obtain a numerical estimate of the maximum possible change in fault behavior that could result from a generator replacement or augmentation. Overall, the new approach aids in the evaluation of the suitability of generator modification or augmentation schemes.