Energy Conversion and Economics最新文献

Renewable energy is a key solution to address the challenges of energy shortages and climate change. Consequently, high-renewable-energy-penetrated power systems (HREPPS) have become a popular trend. This has led to the increasing use of voltage-source converters (VSCs) as renewable-energy interfaces. Meanwhile, other VSC-based applications such as flexible alternating current transmission systems (FACTS) are used for supporting the energy conversion of renewable energy. With the large integration of VSC-interfaced devices, there is a rising concern regarding their impact on the harmonic resonance of power systems. In this study, a new harmonically coupled impedance model is proposed to inspect the harmonic resonance caused by VSC-interfaced devices in HREPPS. The model is derived based on the penetration of a multifrequency harmonic, enabling it to fully reveal the frequency coupling effect in the system. Research has shown that frequency coupling plays an important role in harmonic resonance analysis. The correctness of the proposed harmonic impedance model and its effectiveness on harmonic resonance analysis were verified using time-domain simulations of a real-life photovoltaic integrated system.

The increasing popularity of electric vehicles (EVs) and the enhanced energy storage capability of batteries have made EVs adjustable resources in economic dispatching for power grids. The guidance and control of discharging EVs have become issues with ever-increasing concerns, and the EVs can be discharged to other entities in the grid, which is called vehicle to everything in the power grid (V2eG) technology. When V2eG technologies become widespread, EVs could be widely distributed, fully controllable, and marketable power sources. As ideal mobile power sources, EVs are geographically available all the time. In this paper, the application process of V2eG technology is first introduced, and the current research status of V2eG technology is discussed. The modelling technology involved in V2eG technology is next analysed and discussed in detail. Then, the applications of V2eG technology in economic dispatch are summarized. Furthermore, research on communication technology for V2eG technology is investigated. In addition, the policies and electricity market access criteria related to V2eG are discussed, and the corresponding trading mechanisms are analysed. Finally, the related V2eG technologies are summarized, and the future development direction of V2eG technology is prospected.

Participants in the supply and demand sides of electricity markets can potentially exercise their market power for their benefits. Hence, market power mitigation is an essential component of market management that physically and economically benefits operators by ensuring fairness in deregulated electricity markets. However, the mechanisms of mitigating market power in electricity markets pose several challenges in terms of market structure monitoring, market power evaluation, and market power mitigation. Therefore, this study provides a comprehensive analysis of market power mitigation mechanisms in electricity markets. First, a review of market structure monitoring and market power evaluation methods is provided to assess participants’ potential and degree of use/abuse of market power. Then, a detailed review of optimal bidding strategies in the supply and demand sides of electricity markets is provided. Accordingly, a systematic classification of market power mitigation is described. Finally, market power mitigation challenges and potential future research directions are discussed.

The transformation of the conventional power grid into a smart grid has revolutionised the power industry. However, this has also made the power grid vulnerable to various cyberattacks. This study evaluates the vulnerability of system states, which act as crucial inputs to other essential grid monitoring and control functions, against credible false data injection attacks on nonlinear AC state estimators. Accordingly, two approaches are proposed. The first maximises the yield of the attack, and the second reduces the number of physical meters to be manipulated to launch an attack. This study also develops an attack feasibility index, which can assist in quantifying the feasibility of an false data injection attack while considering various characteristics of a cyberattack. The attack feasibility index also aids in simultaneously comparing the effects of both approaches and assessing the vulnerability of the estimated states. The effectiveness of the proposed methods and the index are established by calculating the state vulnerability of the IEEE 39 bus and IEEE 118 bus test systems.

With the rapid development of renewable energy generation and multi-energy system technologies, reviewing and discussing the emerging power system restoration methods and key technologies suitable for renewable-dominated electric power systems and the Energy Internet are important. Based on this, the backgrounds of renewable-dominated electric power systems and the Energy Internet are first introduced here. Subsequently, the power system restoration process is divided into three phases: the black-start, network reconfiguration, and the load restoration phases; relative restoration strategy research on these three phases is reviewed. Moreover, the boundaries between these three phases are occasionally not sufficiently apparent or even cross in most cases owing to the severity of blackouts and other various factors. Therefore, the key technologies for power system restoration considering multiple phases are analysed in detail. Moreover, the major gaps between existing research and real-world applications and the outlooks on the restoration technologies under renewable-dominated electric power systems are discussed.

In an islanded microgrid (IMG), droop control effectively shares real and reactive power demands among distributed generators (DGs), thereby regulating the frequency and voltage in high X/R ratio networks. However, there is a strong coupling between the real power voltage and reactive power frequency in medium- and low-voltage microgrids due to the low X/R ratio. For effective droop control, the coupling between the real power voltage and reactive power frequency should be eliminated through decoupling factors. Existing methods in the literature on decoupled droop control do not consider the effect of changing network conditions. This study proposes a decoupling method for improved power sharing among parallel-operated inverter-based DGs. Each DG injects a second-harmonic voltage, based on which a second-harmonic self-impedance is calculated at the DG terminal. With certain assumptions, the fundamental self-impedance is computed and used to determine the decoupling factors. The proposed method was implemented on two test cases and compared with existing droop methods. In comparison, the power-sharing ratio is close to the actual value of the proposed method. The simulation results clearly demonstrate that the proposed method improves power-sharing accuracy despite varying the load and network topology.

Under the background of carbon neutrality, distribution networks are facing many new challenges, including providing higher power supply reliability and power quality, additional power supply forms, and better information sharing. The traditional distribution network has difficulty coping with these challenges; thus, it is imperative to transform the traditional distribution network architecture. An energy router (ER) is a type of intelligent power electronic device, and has the potential to play a great role in the transformation of the distribution network. This paper proposes the basic architecture of an ER interconnection system (ERIS), where multiple ERs are gathered together to play a stronger role. Aiming for two different stages of the transformation process of the distribution network, two types of ERISs are employed for a single prosumer and multiple prosumers, respectively. The equivalent modelling, main control strategies, and energy management schemes of the two types of ERIS are respectively illustrated. Several ERIS simulation cases are investigated, and the results verify the advantages and satisfactory performance of the ERIS. The proposed ERIS provides an effective solution for building a new distribution network to adapt to the new challenges in a future carbon neutral era.

The modular multilevel converter (MMC) based high voltage DC (HVDC) system can be effectively used for bulk power transmission. The MMC topology for the voltage source converter (VSC) has several advantages. In this work, the transformerless operation of MMC is explored. The internal dynamic of MMC can induce a third-order zero-sequence harmonic current. Its effect on the system is analysed, including the adverse impacts on energy requirement per arm and power transfer capability. The internal dynamic equations of the transformerless MMC configuration are derived, and two different controllers: the proportional-resonant (PR) controller and proportional-integral (PI) controller, were applied to suppress the unwanted third-order current. The performance analysis of these controllers is presented and the results indicate that the controllers efficiently suppress the third-order harmonic current. Moreover, the electromagnetic transient (EMT) models of MMC under different configurations have been developed on the real-time digital simulator (RTDS) platform. An analysis of internal variables of the MMC is also included to ensure that the controller does not adversely affect the system. Lastly, the state-space model is developed, and the stability is analysed.

In this study, a novel coordinated market scheme is proposed, enabling the participation of distributed energy resources (DERs) in the wholesale as well as local energy market (LEM). First, a day-ahead energy market framework is proposed that is operated by a distribution system operator (DSO) in coordination with the transmission system operator (TSO). The DERs present in a distribution system have the freedom to select among the local or wholesale electricity markets (WEM) to offer their energy. The DSO aggregates all DERs' services and power demand to represent them in a WEM operated at the transmission level. The proposed model allows the DSO to select more economical ways of allocating the resources utilising the TSO-DSO coordination strategy. The objective is to maximise social welfare in light of network constraints. Furthermore, a practical method is developed for DSOs to redistribute any monetary surplus among different DERs participating in the WEM. Numerical simulations indicate the proposed model's economic effectiveness compared to the scenario where DERs are allocated only at the local market level.

The increasing integration of distributed energy resources (DERs) to power grids has fostered the emergence of advanced control technologies for energy management. This study focuses on distributed solutions to economic dispatch considering asynchrony and non-ideal communications. A distributed consensus-based algorithm is developed for general directed networks, where heavy-ball momentum is incorporated into the algorithm design to accelerate convergency. Subsequently, an asynchronous version is proposed based on a general asynchronous communication model with unpredictable, non-uniform, and bounded time delays. Without a global clock in conventional synchronous distributed algorithms, distributed generators (DGs) are allowed to exchange information through local communications at any moment and use out-sync information to execute new updates. Simulations are presented to demonstrate the performance of the proposed algorithm and verify its robustness against time delays.