Abstract:To effectively promote renewable energy development and reduce carbon dioxide emissions, the new power system integrating renewable energy sources (RES), energy storage (ES) technology, and electric vehicles (EVs) is proposed. However, the generation variability and uncertainty of RES, the unpredictable charging schedule of EVs, and access to energy storage systems (ESS) pose significant challenges to the planning, operation, and scheduling of new power systems. Game theory, as a valuable tool for addressing complex subject and multi-objective problems, has been widely applied to tackle these challenges. This work undertakes a comprehensive review of the application of game theory in the planning, operation, and scheduling of new power systems. Through an analysis of 143 research works, the applications of game theory are categorized into three key areas: RES, ESS, and EV charging infrastructure. Moreover, the game theory approaches, payoff/objective functions, players, and strategies used in each study are thoroughly summarized. In addition, the potential for game theory based on artificial intelligence is explored. Lastly, this review discusses existing challenges and offers valuable insights and suggestions for the future research directions.

Abstract:In power systems with high proportion of variable renewable energy, the scarcity of inertia and primary frequency response (IPFR) becomes a critical issue. This evolution necessitates the emergence of corresponding markets. The increasing variety of markets and the diversity of market participants have led to more complex bidding behaviors than before, which need be thoroughly studied. This paper proposes a bi-level model to analyze the bidding behaviors of a renewable-storage system (RSS) acting as a price maker in multiple markets. The nonlinear relationship between IPFR and system frequency is modeled. To depict the characteristics of IPFR and future markets, the unit commitment (UC) process is embedded. To address the nonconvexity caused by the UC process in the proposed bi-level model, a solution approach based on penalty function and dual theory is presented. The proposed model and its solution method are applied to a case study based on the IEEE30-bus system and historical operational data from the California Independent System Operator. The case study results illustrate that the proposed model can effectively characterize the complex bidding behaviors of RSS in multiple markets and validate the efficacy of the solution method.

Abstract:Multiterminal hybrid HVDC systems, combining the advantages of conventional and flexible DC systems, are considered important development trends for future power networks. With the ability to suppress DC fault current, hybrid HVDC systems eliminate the requirement of current limiting reactors at both ends of DC lines. Thus, non-unit protection based on line boundaries is no longer applicable. In this paper, a non-unit protection scheme in cooperation with converter control is proposed to ensure protection speed, reliability, and sensitivity for multiterminal hybrid HVDC systems without line boundaries. In the proposed protection scheme, the protection criterion based on the transient energy of the DC voltage and the direction criterion based on the travelling wave are used to identify whether the fault occurs on the DC line. When the fault is detected as a DC-line fault, the relevant converter station is quickly blocked. After a specified hold-off duration, the converter station interfacing with multiple DC lines is prioritized for restart, while the remaining converter stations are restarted once the DC voltage is stabilized. Simulations based on PSCAD/EMTDC validate the feasibility of the proposed protection scheme and its superiority over competing approaches.

Abstract:With the rapid development of renewable energy, power system inertia is gradually decreasing, threatening the stability of system frequency. Grid-forming (GF)-based wind turbines (WTs) equipped with active inertia response are key to addressing the problem of low-inertia power systems. However, existing researches have focused on the inertia response of GF-based WTs in the maximum power point tracking (MPPT) range, while lacking the discussion on the control and implementation of inertia response in other operating ranges. Therefore, this paper proposes an inertia response control method for permanent magnet synchronous generator (PMSG)-based WTs across the full wind speed range based on inertia synchronization control (IsynC). By analyzing the characteristics of the inertia response and safe operating boundaries of the WT at different operational stages, a control method for the smooth speed transition of the WT across different operating ranges is proposed. By utilizing a composite judgment logic based on the DC voltage rate of change and rotor speed, an adaptive inertia response for different operating modes is achieved. Single and multiple PMSG-WT simulation models are built in PSCAD/EMTDC to simulate the proposed full wind speed range inertia response control and its operational characteristics. The results demonstrate that this method enables the selective inertia response of WTs across the full wind speed range, effectively enhancing the frequency support capabilities of renewable energy generation systems.

Abstract:The limitation of fault currents from converter based distributed generators (CBDGs) in hybrid AC/DC islanded microgrids poses a significant challenge for microgrid protection. This paper presents a novel interharmonic current differential protection scheme for the AC side of hybrid AC/DC islanded microgrids supplied by CBDGs. During faults, the proposed scheme exploits the varying interharmonic components of the currents at both terminals of the faulted line, arise due to variations in the droop-based no-load frequency limits of the interlinking converters (ICs) and the CBDGs. By leveraging these variations, the scheme effectively detects and isolates internal faults within the AC sub-grid, enhancing system reliability. The effectiveness of the suggested scheme is assessed using an enhanced IEEE33-bus hybrid AC/DC microgrid modelled in PSCAD/EMTDC, demonstrating its ability to reliably detect and isolate faults under various operating conditions. Additionally, the scheme is further evaluated using a real-time hardware-in-the-loop experimental setup implemented on an RTDS platform, validating its practical applicability. The simulation and experimental results validate that the presented protection scheme accurately discriminates between normal and faulty conditions across various fault locations, types, and resistance values. This discrimination is achieved without requiring high-bandwidth communication, overcoming a key limitation of existing protection schemes and improving feasibility in real-world deployments.

Abstract:Partial discharge (PD) in covered conductors (CCs) indicates the risks of latent faults and significant insulation degradation. Precisely identifying PD patterns is vital for maintaining electrical systems. A framework for recognizing PD patterns in overhead CCs based on an automatic multi-scale feature learning network and a Transformer is introduced in this paper. First, the method effectively removes background noise via the periodic settings of a multi-seasonal time series decomposition algorithm. An automatic feature multi-scale learning network is then constructed to learn signal features, aiming to minimize the degree of manual intervention. It enhances time series data on the basis of three-phase signal features to address class imbalance problems. An innovative global multichannel pattern recognition framework utilizing a Transformer is designed, featuring positional encoders to identify intra-phase and inter-phase feature correlations and a dynamic gating mechanism for capturing complex data patterns. In experimental validations, the proposed algorithm achieves a detection accuracy of 98.6% and a specificity of 99.2%, representing an superior performance in this field. This research provides an accurate and highly generalizable solution for PD detection, offering solid theoretical support for the digital operations and maintenance of power transmission and distribution equipment.

Abstract:Addressing carbon reduction in the energy sector is crucial in the global fight against climate change. In response to this, a source-load coordinated optimization framework is proposed for distributed energy systems (DES). The high carbon-emitting power plants in the source side are transformed into carbon capture power plants to capture CO2 generated during power generation, thereby improving the power efficiency and decreasing the carbon emissions of the DES. On the load side, the low carbon demand response (LCDR) method is introduced to replace the traditional price-driven demand response. Governed by dynamic carbon emission factors, LCDR aims to facilitate a low carbon shift in end users' energy consumption patterns. An extensive analysis is conducted on the viability of the proposed source-load coordinated framework for low-carbon economic scheduling and an optimal optimization model is formulated by considering the comprehensive cost of the DES. The original problem is then transformed into a hierarchical Stackelberg game model with multi-leaders and multi-followers, which is further solved by an efficient quasi-potential game (QPG) algorithm. The practicality and scalability of the proposed work are validated through simulations conducted on the modified IEEE39-node and IEEE118-node test systems. The findings verify that the proposed framework is highly effective in improving power plant efficiency, optimizing the use of renewable energy, and substantially lowering carbon emissions.

Abstract:When a single-phase to ground fault (SPGF) occurs near the main power source in an active distribution network, distance protection section II (DPS-II) located at the distributed generator (DG) side operates with a delay. In gap-grounded transformers, this delay can lead to gap breakdown due to neutral-point overvoltage, which adversely affects the operation of DPS-II on the DG side. To address this issue, this paper proposes an improved DPS designed for active distribution networks with gap-grounded transformers. First, the factors influencing the additional impedance are analyzed after gap breakdown. To mitigate the effects of the additional impedance on DPS performance, an improved DPS based on real short-circuit impedances is introduced for active distribution networks. This scheme utilizes the negative-sequence current distribution factor on the DG side to accurately calculate the additional impedance angle, ensuring reliable protection. Simulation results demonstrate that the proposed scheme effectively operates under forward faults across various DG capacities, fault locations, local loads, and fault transition resistances. In addition, it avoids tripping under reverse faults, thereby confirming its reliability and superiority.

Abstract:The rapid advancement of modular multi-level converter-based high-voltage direct current (MMC-HVDC) interconnection projects may lead to torsional vibrations in turbo-generator shafts, causing oscillations that pose operational risks to the power system. Impedance-based analysis is an effective method to evaluate the stability of power systems with power electronic components. However, conventional turbo-generator impedance models, such as the RL equivalent impedance model, only address the electrical aspects of turbo-generators and neglect the influence of shafting characteristics, potentially leading to inaccurate analysis results. To address this issue, a turbo-generator impedance model is introduced which incorporates shafting characteristics validated through frequency scanning methods. Focusing on the turbo-generator and MMC-HVDC interconnection system, the oscillation analysis results are compared using the developed and traditional impedance models. The findings indicate that the developed model exhibits greater applicability and accuracy for power systems incorporating electronic equipment. Furthermore, a virtual damping control strategy for MMC-HVDC based on modulation links is developed to mitigate oscillation issues. The efficacies of the proposed impedance model and control strategy are validated in the turbo-generator and MMC-HVDC interconnection system.

Abstract:This paper proposes an AI-based approach for islanding detection in active distribution networks. A review of existing AI-based studies reveals several gaps, including model complexity and stability concerns, limited accuracy in noisy conditions, and limited applicability to systems with different types of resources. To address these challenges, this paper proposes a novel approach that adapts the WaveNet generator into a classifier, enhanced with a denoising UNet model, to improve performance in varying signal-to-noise ratio (SNR) conditions. In designing this model, we deviate from state-of-the-art approaches that primarily rely on long short-term memory (LSTM) architectures by employing 1D convolutional layers. This enables the model to focus on spatial analysis of the input signal, making it particularly well-suited for processing long input sequences. Additionally, residual connections are incorporated to mitigate overfitting and significantly enhance the model's generalizability. To verify the effectiveness of the proposed scheme, over 14 000 islanding/non-islanding cases are tested, considering different load active/reactive power values, load switching transients, capacitor bank switching, fault conditions in the main grid, different load quality factors, SNR levels, changes in network topology, and both types of conventional and inverter-based sources.

Abstract:Similar to synchronous generators (SGs), symmetrical short-circuit faults can reduce the stability margin of grid-forming renewable power generation (GFM-RPG), thereby heightening the risk of transient instability. While existing studies primarily examine single-machine infinite-bus systems, this work explores transient stability challenges inherent in paralleled GFM-RPG systems. First, through rigorous mathematical derivation, it establishes that the transient characteristics of paralleled systems can still be effectively characterized by a second-order motion equation. Subsequently, by applying the extended equal area criterion (EEAC) and numerical solutions to differential equations, the study uncovers the governing principles behind the variations in the critical clearing angle (CCA) and critical clearing time (CCT) for the paralleled GFM-RPG system under various operating conditions. Finally, to mitigate potential instability risks, two corrective strategies, namely adaptive damping enhancement and power switching control, are proposed to improve the transient stability of the paralleled system during symmetrical faults. Simulation results confirm the accuracy of the theoretical analysis and demonstrates the effectiveness of the proposed strategy.