Torque Limit-based Inertial Control Method Based on Delayed Support for Primary Frequency Control of Wind Turbines

To avoid the secondary frequency dip caused by the steep drop of the electrical power of wind turbines(WTs)at the end of frequency support stage,the torque limit-based iner-tial control(TLIC)method sets the power reference as a linear function of rotor speed,rather than the step form for the step-wise inertial control.However,the compensation effect on the frequency nadir(FN)caused by the load surge is weakened as the TLIC power is no longer in the step form.Specifically,the maximum point of the frequency response component(FRC)contributed by TLIC occurs earlier than the minimum point of FRC corresponding to the load surge,so that the FN cannot be adequately raised.Therefore,this paper first investigates the relation between the peak and nadir times of FRCs stimulated by the TLIC and load power.On this basis,with the compensation principle of matching the peak and nadir times of FRCs,the improved TLIC method based on delayed support is proposed.Finally,the effectiveness of the proposed method is validated via the experiments on the test bench of wind-integrated power system.

A Temporary Frequency Response Strategy Using a Voltage Source-Based PermanentMagnet Synchronous Generator and Energy Storage Systems

Energy storage systems(ESS)and permanent magnet synchronous generators(PMSG)are speculated to be able to exhibit frequency regulation capabilities by adding differential and proportional control loops with different control objectives.The available PMSG kinetic energy and charging/discharging capacities of the ESS were restricted.To improve the inertia response and frequency control capability,we propose a short-term frequency support strategy for the ESS and PMSG.To this end,the weights were embedded in the control loops to adjust the participation of the differential and proportional controls based on the system frequency excursion.The effectiveness of the proposed control strategy was verified using PSCAD/EMTDC.The simulations revealed that the proposed strategy could improve the maximum rate of change of the frequency nadir and maximum frequency excursion.Therefore,it provides a promising solution of ancillary services for frequency regulation of PMSG and ESS.

Synchronization criteria for multiple memristor-based neural networks with time delay and inertial term

This present work uses different methods to synchronize the inertial memristor systems with linear coupling. Firstly, the mathematical model of inertial memristor-based neural networks(IMNNs) with time delay is proposed, where the coupling matrix satisfies the diffusion condition, which can be symmetric or asymmetric. Secondly, by using differential inclusion method and Halanay inequality, some algebraic self-synchronization criteria are obtained. Then, via constructing effective Lyapunov functional, designing discontinuous control algorithms, some new sufficient conditions are gained to achieve synchronization of networks. Finally, two illustrative simulations are provided to show the validity of the obtained results, which cannot be contained by each other.

Dynamic contribution of variable-speed wind energy conversion system in system frequency regulation

Frequency regulation in a generation mix having large wind power penetration is a critical issue, as wind units isolate from the grid during disturbances with advanced power electronics controllers and reduce equivalent system inertia. Thus, it is important that wind turbines also contribute to system frequency control. This paper examines the dynamic contribution of doubly fed induction generator （DFIG）-based wind turbine in system frequency regulation. The modified inertial support scheme is proposed which helps the DFIG to provide the short term transient active power support to the grid during transients and arrests the fall in frequency. The frequency deviation is considered by the controller to provide the inertial control. An additional reference power output is used which helps the DFIG to release kinetic energy stored in rotating masses of the turbine. The optimal speed control parameters have been used for the DFIG to increases its participation in frequency control. The simulations carried out in a two-area interconnected power system demonstrate the contribution of the DFIG in load frequency control.