Combining supercapacitors and power electronic devices, grid-forming static var generators (SVGs) can provide dynamic reactive power compensation while providing inertia support to the system, thereby enhancing the stability of renewable energy systems. However, challenges remain regarding the coordination between the inertia support from grid-forming SVG and the control actions of automatic generation control (AGC) units in renewable energy gathering stations. To address this issue; this paper proposes a coordinated control strategy that accounts for the state of charge (SOC) of supercapacitors, aiming to enhance the inertia support role of grid-forming static var generators (SVG) in renewable energy gathering stations and achieve their coordinated cooperation with the AGC system. By integrating the millisecond-level rapid response capability of grid-forming SVG and the second-level continuous regulation capability of AGC, this strategy establishes a multi-timescale active power support system: at the initial stage of a frequency dip, the grid-forming SVG independently provides rapid inertia support; subsequently, it implements coordinated power allocation with the station-level AGC while comprehensively considering the SOC of supercapacitors and the energy status of wind turbine units, thereby balancing transient frequency stability and the system's long-term continuous regulation capability. Finally, a controller-level hardware-in-the-loop test platform is established for renewable power plants. Tests under typical operating conditions demonstrate the effectiveness and superiority of the proposed strategy, indicating that it can provide enhanced support when frequency fluctuations occur in renewable energy gathering stations.

To address the issues of low system inertia and weakened disturbance resistance caused by the high proportion of renewable energy in the sending-end power grid, which in turn restricts the safe integration of renewable energy, this paper proposes an optimization method for grid-connected energy storage configuration considering safety and stability constraints. Firstly, the mechanism by which energy storage affects grid frequency stability and multi-station short-circuit ratio is analyzed. Secondly, with the objective of maximizing the total output of renewable energy in the sending-end power grid, an evaluation model for the ultimate acceptance capacity of renewable energy is established, incorporating constraints such as frequency stability, short-circuit ratio, and power flow balance. Thirdly, a comprehensive compensation demand index for short-circuit ratio is proposed to achieve targeted optimization for energy storage site selection and capacity determination. Finally, simulation analysis is conducted on two transmission modes of an actual power grid in a certain region using the MATLAB platform to verify that the proposed energy storage configuration method can enhance the acceptance capacity of renewable energy while ensuring the safe and stable operation of the system.

To address the problems of poor multi-scenario adaptability and slow transient overcurrent suppression response of traditional virtual resistance, this paper proposes a grid-forming fault overcurrent suppression strategy based on multi-scenario application and flexible virtual resistance regulation. First, a simulation model of the grid-forming converter system is established. The strategy achieves accurate multi-scenario adaptation by combining the short-circuit ratio, power output quality, and system damping ratio requirements of the application scenarios. Second, it deduces the virtual resistance value range based on fault ride-through standards and overcurrent theory to ensure parameter rationality. When a fault occurs, the adaptive regulation strategy based on the instantaneous current magnitude and its rate of change is effectively implemented to improve the dynamic adaptation capability of the virtual resistance to transient overcurrent and dynamically correct the virtual resistance value. Finally, a controller-level hardware-in-the-loop test platform based on a real-time simulator and an actual controller is built, and the effectiveness and superiority of the proposed control strategy are tested and verified through typical operating scenarios. This strategy improves scenario adaptability and dynamic regulation performance of virtual resistance, can quickly respond to transient overcurrent, effectively suppress fault overcurrent, and enhance the system's fault ride-through capability and operational stability.

The main features of new-type power systems include high penetration of renewable energy and power electronic devices, which may cause stability issues like wideband oscillations that threaten the systems’ security. Current technologies of oscillation suppression fail to adapt to the numerous operating conditions, high-dimensional system modelling, and time- varying modes of oscillations. Furthermore, electrochemical energy storage has limited practical applications in terms of stability control on short-time scales, whose utilization potential has not been fully realized. Consequently, this paper proposes new methods and equipment based on lithium battery energy storage to address the issues of wideband oscillations in new- type power systems. Firstly, this paper proposes a method of adaptive damping control, enabling accurate identification of oscillation features and adaptive calculation of damping control parameters. Secondly, this paper develops a module of battery storage-based embedded new-type power system stabilizer (BSE-NPSS), which collaborates with an existing electrochemical power conversion system (PCS), realizing three sub-functions (feature identification, parameter calculation, and stability control). Finally, this paper verifies the effectiveness of BSE-NPSS by combining the module with a simulation system which occurs subsynchronous or supersynchronous oscillations caused by series compensation in doubly-fed wind turbines.

Traditional grid-following wind turbines lack active voltage support capabilities, while grid-forming units, adopting voltage source self-synchronizing control methods, possess the ability to autonomously establish voltage and frequency. Hybrid grid-following/grid-forming wind power stations can achieve both voltage stability and efficient power generation in wind farm aggregation areas, representing a key paradigm for constructing new-type power systems. However, significant differences exist between grid-following and grid-forming wind turbines in terms of response mechanisms, control modes, and support characteristics. The response coupling during dynamic regulation processes makes balanced reactive power and voltage control in hybrid wind farms particularly challenging. To address these challenges, this paper first analyzes the control structures and regulation characteristics of grid-following/grid-forming units, clarifying applicable scenarios for different device types. Subsequently, it investigates the reactive power-voltage distribution characteristics and voltage support requirements in wind farms, proposing a reactive power allocation strategy for hybrid wind farms that coordinates turbine terminal voltage control with smooth system-wide voltage regulation. This strategy achieves balanced voltage control across the wind farm. Finally, a simulation test platform for hybrid grid-following/grid-forming wind farms is established, validating the effectiveness of the proposed strategy.

The fast frequency response (FFR) provided by the battery energy storage system (BESS) is essential for maintaining the frequency stability of a power system. However, the voltage coupling effect (VCE) may negatively affect the FFR of the BESS in weak grids. The VCE, particularly when comparing grid-following (GFL) and grid-forming (GFM) control strategies, remains inadequately explored. This paper proposes a novel FFR modeling approach for the GFL & GFM BESS considering the VCE. The impacts of BESS converter parameters and system characteristics on the VCE are investigated. Comparative analyses between GFL & GFM control are performed to quantify the VCE differences and identify critical parameters affecting the VCE on the FFR. The proposed models and analyses are validated through electromagnetic transient simulations and control-hardware-in-the-loop (CHIL) experiments. It is revealed that the VCE emerges from the instantaneous voltage drop during step disturbances, leading to reduced active power support and delayed frequency recovery. The VCE increases significantly as the short circuit ratio (SCR) approaches 2, but can be mitigated through increased voltage droop coefficients or, in GFM control, through adjusting virtual impedance. With appropriately selected parameters, the GFM BESS demonstrates superior performance in weak grids with reduced capacity requirements compared to GFL BESS.

The Grid-Forming Doubly-Fed Induction Generator (GFM-DFIG) has attracted considerable attention due to its capabilities in voltage self-regulation and inertia support, although stability concerns persist. Transient stability is mainly governed by grid-forming control, whereas small-signal stability is more affected by both the grid-forming control and the current control loop. This paper offers a thorough investigation into how short-circuit ratio (SCR) and system parameters affect the stability of GFM-DFIG, combining transient stability and small-signal stability analyses. First, a full-order model of the GFM-DFIG is established, followed by a reduced-order transient model. Using the transient model, the transient stability limit voltage (TSLV) under permanent fault conditions is calculated, providing a key benchmark for evaluating the generator’s transient stability. A detailed quantitative analysis is then conducted to explore the effects of SCR and parameter variations on the transient stability boundary. Next, small-signal stability is assessed through eigenvalue trajectories and damping ratios, revealing the impact of various parameters. The findings show that optimizing parameter settings can enhance both transient stability and small-signal stability. Finally, simulations are performed to validate the accuracy of the theoretical analyses.

Against the backdrop of vigorously developing renewable energy across the country, the form of microgrids can achieve efficient application of distributed power sources. The AC-DC hybrid microgrid is relatively complex, with strong randomness in distributed clean energy sources such as wind and light, and flexible and variable electricity demand on the user side, which poses great challenges to the stable operation of the microgrid. In this paper, considering the uncertainty on both sides of the source and load, and introducing the demand side response to achieve optimal operation of the AC-DC microgrid. The first is to use multi-scenario analysis technology to simulate the uncertainty of wind, light and load, and then update the load forecasting level through demand-side response. Then, a multi-objective optimal scheduling model of microgrid including power generation cost and environmental cost is established, and multi-objective particle swarm optimization (MOPSO) is used to solve the model. Finally, an example is used to verify this method. The results show that the required economy and environmental protection can be guaranteed under certain constraints.

In recent years, new type of voltage fluctuation problem often occurs in the large-scale wind power system, and the traditional suppression strategy can not be applied, there is an urgent need to propose an effective strategy. This paper firstly explains the new transient voltage destabilization mechanism; then verifies the related discriminative methods; finally, the effects of active output and crossing threshold on transient voltage are investigated and verified by simulation.

For distributed renewable energy devices that can operate in both grid connected and island mode, and can switch between the two according to demand, The key issue in the switching process is the pre-synchronization of voltage amplitude, frequency and phase. In recent years, the emergence of decentralized microgrid structures which has relatively independent power sources rendered traditional pre-synchronization technology obsolete. An independent pre-synchronization scheme was proposed that completes parallel pre-synchronization functions of multiple machines without the need for intercommunication. Based on the MATLAB/Simulink platform, a power simulation model containing multiple distributed photovoltaic virtual synchronous machines was constructed, and a pre-synchronization control unit and control parameters were designed. The influence of pre-synchronization control parameters on the dynamic power circulation during the pre-synchronization process was analyzed, and control performance under different conditions were obtained, verifying the excellent performance of the proposed pre-synchronization grid connection strategy, and suggestions were proposed accordingly.

通过模拟同步发电机的机械运动方程,建立电压控制型虚拟同步发电机,设计原动机调节和励磁调节控制策略,并模拟同步发电机的转动惯量,提高新能源机组对电网稳定运行主动支撑能力.提出有功-负荷系数、有功调频系数、无功调压系数、一次调频稳定时间和无功调压稳定时间5个控制特性评估指标,构建基于Matlab/Simulink的电压控制型虚拟同步发电机控制特性电磁暂态仿真验证模型,重点分析小扰动下不同关键控制参数对电压控制型虚拟同步发电机有功调频和无功调压性能的影响,定量分析关键指标变化趋势和规律,给出有功控制环虚拟惯量、阻尼系数以及无功控制环积分系数和下垂系数工程化应用优化参数区间.最后,通过建立多台电压控制型虚拟同步发电机并联并网模型,研究电压控制型虚拟同步发电机间交互振荡机制,分析得出接入大电网振荡临界参数、振荡频率及多机并联振荡模式.

BeiDou Navigation Satellite System (BDS) has effectively improved management efficiency and significantly reduced operating costs in the intelligent agricultural production, smart traffic management and epidemic prevention. Based on the research of BeiDou technology, an intelligent condition monitoring mode of power system is proposed for the demand of environmental condition monitoring of power transmission lines and substation equipment, combined with big data and artificial intelligence technology. The monitoring effectiveness of transmission and substation application scenario monitoring mode is elaborated to provide useful reference for condition monitoring.

In this paper, an integral-type half-tangent phase locked loop (IHtan-PLL) is presented for power systems with harmonic disturbances. Compared with the traditional Synchronous Reference Frame Phase-Locked Loop (SRF-PLL), the proposed IHtan-PLL has the following advantages: (1) when the frequency occurs a large variation, the SRF-PLL has plenty of oscillations, and a considerable prolonged transient response. Whereas, the IHtan-PLL shows the faster trends, and on oscillation emerges; (2) the IHtan-PLL has a better filtering effect in terms of steady-state when the power system contains harmonic disturbances. Simulation tests are presented to demonstrate superior performance of IHtan-PLL.

By simulating the operating dynamics of synchronous generators (SGs), the use of virtual synchronous generators (VSGs) can help overcome inverter-based generators’ shortcomings of low inertia and minimal damping for grid-forming applications. VSGs’ stability are very important for their solar and wind electricity applications. Currently, the related research primarily focuses on VSGs and their applications for microgrids. There has been little research to explore how VSGs effect low frequency oscillations in power transmission systems. This paper describes a small-signal model of a VSG-SG interconnected system, which is suitable for studying low frequency oscillation damping in a power transmission grid. Based on this model, the effects of VSGs on low frequency oscillations are compared with the effects of SGs to reveal the mechanism of how VSGs influence damping characteristics. The influence of each VSG control loop on oscillations is also analyzed in this paper. Then, the low frequency oscillation risks with different types of VSGs are described. Finally, experiments on a real-time laboratory (RT-LAB) platform are conducted to verify the small-signal analysis results.

Through simulating the mechanical motion equations of synchronous generator, applying the synchronous generator mathematical model for converter control strategy and formed the voltage controlled virtual synchronous generator. This paper proposed the prime motor regulation and excitation regulation algorithm, and simulating the inertial of synchronous generator. As a result, the voltage controlled virtual synchronous generator has the function of active power frequency regulation and reactive power voltage regulation, and solving the problems of impendences and damping is low under grid-connected with power grid, also supporting the power grid safe and stable operation. By building the Matlab/Simulink models, this paper validates the voltage controlled virtual synchronous generator is able to simulate the operation characteristics of synchronous generator. In addition, this paper analysis the different parameters of virtual inertial, damping, integration and droop effects the control ability by simulation, and proposed the optimal parameters range for engineering application.

The phenomenon of three phase voltage imbalance frequently occurs in large-scale new energy grid connected areas in China; in severe cases, a large number of wind turbines will be disconnected from the grid. To solve the problem of the voltage imbalance at the point of common coupling (PCC), analyze the influence of generator parameters change on negative sequence voltage under the background of unbalanced power grid, a modeling method of base-frequency negative sequence impedance of doubly fed induction generator (DFIG) which including phase locked loop (PLL), rotor side converter (RSC) and grid side converter (GSC) is proposed. By establishing the negative sequence equivalent circuit of grid-connected system of DFIG, the relationship between the negative sequence voltage of PCC and the negative sequence impedance of DFIG is listed, and analyzing the sensitivity of control parameters link to base-frequency impedance, the parameter that has great influence on base-frequency negative sequence impedance of PCC is found out. Finally, the accuracy of impedance modeling and sensitivity analysis is verified by simulation studies.

Al-Li alloy stiffened panel is the main structural form of aircraft fuselage. Laser welding will produce welding deformation and residual stress, on the other hand, low velocity impact will also affect the residual bearing capacity of stiffened panel structure. In this study, the nonlinear finite element (FE) method is used to simulate the laser welding process of stiffened panel, and the welding residual stress is directly introduced into the subsequent impact after compression (CAI) process of stiffened panel. The effects of different impact positions and different impact energy on the residual CAI strength of stiffened panel are studied. The results show that the impact damage has the greatest effect on the residual compressive strength of stiffened panel when the punch impacts the stiffener, and the greater the impact energy is, the greater the influence is.

In this work, we develop a novel non-autoregressive TTS model to predict all mel-spectrogram frames in parallel. Different from the previous non-autoregressive TTS methods, which typically require an external aligner implemented by an attention-based autoregressive model, our model can be opti-mized jointly without sophisticated external aligners. Motivated by the CTC-based speech recognition, which is a simple and effective manner to achieve the frame-level forced-alignment between the speech and text, our main idea is to consider the aligner learning of TTS as a CTC-based speech recognition like task. Specifically, our model learns the alignment generator by adopting the CTC-loss, to provide supervision for the duration predictor learning on the fly. In this way, we are able to learn a one-stage TTS system by optimizing the aligner with the feed forward transformer jointly. In inference phase, the aligner is removed and the duration predictor is used to predict duration sequence for synthesizing speech. To demonstrate our method, we conduct extensive experiments on an open-source Chinese standard Mandarin speech dataset11https://www.data-baker.com/open_source.html. The results show that our method achieves competitive performance compared with counterpart models (e.g. FastSpeech: a well-known non-autoregressive with extra aligner) in terms of the synthesized speech quality and robustness.

Phase-locked loop (PLL) is widely used in voltage source converter (VSC) to synchronize with grid. This paper comprehensively analyzes the transient stability of the PLL-VSC and obtains the VSC’s instability characteristics similar to the synchronous generator. The instability of VSC is mainly caused by insufficient deceleration area and instability without equilibrium point. To improve the transient stability of VSC, a hybrid PLL is proposed. This method dynamically compensates the phase of the PLL to improve the transient stability performance of the system without obtaining the specific parameters of the grid line. The phase compensation of PLL creates new equilibrium points to solve the most problem of insufficient deceleration area or no equilibrium point. Time-domain simulations are given to verify the effectiveness of the theoretical analysis.

Droop controlled voltage source converters (VSCs) are very sensitive to overloading due to the low current capacity of switching devices, which implies that VSCs must switch from normal voltage control mode to current control mode at faults or load disturbance and therefore occur transient instability. This paper reviews current saturation phenomenon and reason of droop controlled VSCs. In particular, the boundary conditions between current saturation mode and normal mode are analyzed to express VSC’s static active power critical value at normal mode. Then, the influence of grid parameters and control parameters for current saturation is analyzed. Finally, the effectiveness of theoretical analysis is verified in MATLAB/Simulink and hardware-in-the-loop experiments based on RTLAB. The normal unsaturated VSC’s static active power critical value of theoretical calculation is basically consistent with the simulation.