V2G optimized power control strategy based on time-of-use electricity price and comprehensive load cost

Electric vehicles (EVs), as a nascent industry, have seen significant advancements in technology and policy, allowing for a clearer development trend and promising future prospects. The integration of EVs with the energy sector is becoming a key focus, with vehicle-to-grid (V2G) technology and efficient collaboration serving as major areas for technical breakthroughs. This paper begins by analyzing the impact of disordered charging of EVs on the power grid. Given that EVs can function as mobile energy storage units, they have the potential to provide flexible support for the secure operation of the power grid. Building upon this, the paper proposes an optimized V2G power control strategy that is based on time-of-use electricity pricing and comprehensive load cost optimization. The principle behind this proposed control strategy is elaborated upon in the subsequent sections. To validate the effectiveness of the proposed V2G optimized power control strategy, the paper provides simulation results. These results serve to demonstrate the practical feasibility and benefits of the proposed strategy in leveraging the capabilities of EVs and promoting grid stability and efficiency

Analysis on the inertia and the damping characteristics of DFIG under multiple working conditions based on the grid-forming control

The rapid development of wind power not only provides clean energy, but also brings new challenges to the reliable operation of power system, the high proportion of wind power connected to the grid has caused significant changes in the power supply composition structure of the power system. The wind power has become the major power sources of the power system, which brings great challenges to the dynamic process and stability of the system. In order to deal with the problems of inertia reduction, system frequency dynamic deterioration and stability reduction caused by the grid connection of wind turbines under the traditional PLL control, the wind turbines based on the grid-forming control can realize synchronous operation with the power grid without relying on the phase-locked loop. Providing active support for power grid and other excellent characteristics are being widely studied and applied in academia and industry. The dynamic characteristics of the grid-forming control wind turbine will gradually become an important factor determining the dynamics of power system. The influence of the inertia and damping characteristics on the performance of the grid-forming wind turbines is significant. Therefore, the research on the dynamic characteristics of the grid-forming wind turbine and its influence on the system dynamic process has important significance and value. Taking the DFIG based on the grid-forming control as the research object, this paper analyzes and studies the modeling, inertia characteristics and damping characteristics of the grid-forming DFIG under multiple working conditions. The simulation results show that there is a coupling relationship between the inertia and the damping, the inertia and the damping under different working conditions have different characteristics

Study on fault ride-through control of islanded wind farm connected to VSC-HVDC grid based on the VSC converter AC-side bus forced short circuit

Wind farms integrated to an AC power system through a voltage source converter-based high-voltage direct current system (VSC-HVDC) are viewed as islanded wind farms. The wind farm side converter of VSC-HVDC maintains a constant frequency of the wind farm collection network and also controls its voltage. However, the transient responding time of VSC-HVDC is very short, and its fault responding feature is at the millisecond (ms) level. As a result, under grid fault conditions, the VSC station could be overloaded and even operation could be quitted because of blocking if islanded wind farms fail to limit their power generation in time. This study proposes a fault ride through control method for VSC-HVDC connected with islanded wind farms based on the forced short circuit of the AC-side bus of the VSC station. When there is a fault in the VSC-HVDC and the protection equipment is not able to cut off the excessive power at the ms level, the short-circuit resistance installed on the AC side of the VSC station would be switched to make a forced short circuit. That would activate the low-voltage ride through mode of islanded wind farms, and therefore reduce the power flowing into the VSC quickly. The HVDC fault and short circuit on the AC side would be cleared at the same time. The VSC-HVDC system accomplishes fault ride through

Power oscillation coordination damping control strategy of DFIG for fault ride through after clearing the fault

Wind turbines should have fault ride through capability, and also it can provide damping for the power grid by improving the control strategy. However, the currently corresponding control strategy is designed independent for the fault voltage through control and damping control. If the fault ride through control and damping control of a converter is uncoordinated under the grid fault, the output of the two control branches can be superimposed, which will affect the output power dynamic performance of doubly fed induction generator (DFIG) after clearing the fault. At the same time the overcurrent and other issues may occur in serious cases, and even lead to DFIG trip off. Based on the dynamic process analysis of DFIG after clearing the fault, an additional damping controller in the rotor side converter control of DFIG is designed, which damps the system low-frequency oscillation by modulating the rotor active current component. A coordination damping control strategy of DFIG based on a fault ride through control and damping control is proposed for damping the power oscillation after clearing the fault, the correctness of the proposed control method has been verified through time-domain simulation

Effect of PLL on transient performance of wind turbines generator under voltage phase jump

With the increasing proportion of wind power installed capacity, the influences of transient characteristics of wind turbines generator on safety and stability of power grid is becoming more and more important. The rotor side of doubly fed induction generator (DFIG) is connected to the grid through a back-to-back inverter, and vector control based on phase-locking synchronisation is used generally. Phase-locked loop (PLL) drive internal potential phase changes to achieve synchronous operation with the grid. Therefore, PLL has great influence on transient characteristics of DFIG. A dynamic model of PLL is built in this study. Phase-locking performance of PLL under voltage phase jump is studied by changing its parameters, and its impact mechanism on transient characteristics of DFIG is proposed. Simulation models are built with DIgSILENT/PowerFactory. The influence of parameters of PLL on phase-locking performance of DFIG under voltage phase jump is simulated

An Extended System Frequency Response Model Considering Wind Power Participation in Frequency Regulation

With increasing penetration of wind power into the power system, wind power participation in frequency regulation is regarded as a beneficial strategy to improve the dynamic frequency response characteristics of power systems. The traditional power system frequency response (SFR) model, which only includes synchronous generators, is no longer suitable for power systems with high penetrated wind power. An extended SFR model, based on the reduced-order model of wind turbine generator (WTG) and the traditional SFR model, is presented in this paper. In the extended SFR model, the reduced-order model of WTG with combined frequency control is deduced by employing small signal analysis theory. Afterwards, the stability analysis of a closed-loop control system for the extended SFR model is carried out. Time-domain simulations using a test system are performed to validate the effectiveness of the extended SFR model; this model can provide a simpler, clearer and faster way to analyze the dynamic frequency response characteristic for a high-wind integrated power systems. The impact of additional frequency control parameters and wind speed disturbances on the system dynamic frequency response characteristics are investigated

Improved active power control of virtual synchronous generator for enhancing transient stability

Abstract Virtual synchronous generators (VSGs) are widely used as grid‐forming control converters in the inverter‐dominated power system. Similar to synchronous generators (SGs), there would also be transient instability of VSGs under certain conditions. In this paper, the transient dynamics of VSGs during gird faults are fully investigated based on the large‐signal model. It is revealed that the significant deteriorative of active power control loop (APCL) is the main factor on the transient stability of VSGs. Thus, for enhancing transient stability during grid faults, an integrator‐based feedback loop is introduced for APCL. Then, an enhanced active power control of VSGs is presented with transient stability enhancement during grid faults. Moreover, the impacts of different integral parameters on the transient stability of VSGs are studied. Finally, the validity of the transient stability enhancement of VSGs is demonstrated by the hardware‐in‐loop (HIL) results

Dual-mode Switching Fault Ride-through Control Strategy for Self-synchronous Wind Turbines

The installed capacity of renewable energy generation has continued to grow rapidly in recent years along with the global energy transition towards a 100% renewable-based power system. At the same time, the grid-connected large-scale renewable energy brings significant challenges to the safe and stable operation of the power system due to the loss of synchronous machines. Therefore, self-synchronous wind turbines have attracted wide attention from both academia and industry. However, the understanding of the physical operation mechanisms of self-synchronous wind turbines is not clear. In particular, the transient characteristics and dynamic processes of wind turbines are fuzzy in the presence of grid disturbances. Furthermore, it is difficult to design an adaptive fault ride-through (FRT) control strategy. Thus, a dual-mode switching FRT control strategy for self-synchronous wind turbines is developed. Two FRT control strategies are used. In one strategy, the amplitude and phase of the internal potential are directly calculated according to the voltage drop when a minor grid fault occurs. The other dual-mode switching control strategy in the presence of a deep grid fault includes three parts: vector control during the grid fault, fault recovery vector control, and self-synchronous control. The proposed control strategy can significantly mitigate transient overvoltage, overcurrent, and multifrequency oscillation, thereby resulting in enhanced transient stability. Finally, simulation results are provided to validate the proposed control strategy