Balancing the active power between the generation side and the demand side to maintain the frequency is one of the main challenging problems of integrating the increased intermittent wind power to the smart grid. Although the energy storage system, such as battery energy storage system (BESS), has potential to solve this problem, the installation of the BESS with large capacity is limited by its high cost. This chapter investigates the frequency regulation of the smart grid working in the isolated mode with wind farms by introducing not only the BESS but also dynamic demand control (DDC) via controllable loads and the plug-in electric vehicles (PEVs) with vehicle-to-grid (V2G) service. First, modelling of a single-area load frequency control (LFC) system is obtained, which includes the wind farms equipped with variable-speed wind turbines, the simplified BESS, the air conditioner based DDC and the distributed PEVs. The LFC system contains traditional primary and supplementary control loops and three additional control loops of the BESS, the PEVs and the DDC, respectively. Then, state-space models of the closed-loop LFC scheme with/without communication delays in the control loops are derived, and the stability of the closed-loop system with time delays is investigated via the Lyapunov functional based method. Third, gains of proportional integral derivative (PID)-type controllers are tuned based on the H∞ performance analysis and the particle swarm optimization searching algorithm. Case studies are carried out for the single-area smart power grid through the MATLAB®/Simulink platform. Both the theoretical analysis and the simulation studies demonstrate the contribution of the DDC, the BESS, and the PEVs to frequency regulation, and the robustness of the designed PID-type LFC against the disturbances caused by the load changes and the intermittent wind power and the delays arising in the control loops via theoretical analysis and the simulation studies.

Chapter Contents:

• 8.1 Introduction
• 8.2 Dynamic model of smart grid for frequency regulation
• 8.2.1 Structure of frequency regulation
• 8.2.2 Wind farm with variable-speed wind turbines
• 8.2.3 Battery energy storage system
• 8.2.4 Plug-in electric vehicles
• 8.2.5 Controllable air conditioner based DDC
• 8.2.6 State-space model of closed-loop LFC scheme
• 8.3 Delay-dependent stability analysis
• 8.3.1 Delay-dependent stability criterion
• 8.3.2 Delay margin calculation
• 8.4 Delay-dependent robust controller design
• 8.4.1 Delay-dependent H∞ performance analysis
• 8.4.2 Controller gain tuning based on the PSO algorithm
• 8.5 Case studies
• 8.5.1 Robust controller design
• 8.5.2 Contribution of the DDC, BESS, and PEV to frequency regulation
• 8.5.3 Robustness against to load disturbances
• 8.5.4 Robustness against to parameters uncertainties
• 8.5.5 Robustness against to time delays
• 8.6 Conclusion
• Bibliography

Inspec keywords: smart power grids; load regulation; H∞ control; electric vehicles; secondary cells; Lyapunov methods; wind power plants; frequency control; three-term control; air conditioning; wind turbines; particle swarm optimisation

Other keywords: communication delays; closed-loop system stability; proportional integral derivative-type controllers; frequency regulation; wind farms; battery energy storage system; isolated mode; Matlab-Simulink platform; generation side; V2G service; Lyapunov functional based method; variable-speed wind turbines; particle swarm optimization; air conditioner; demand side; intermittent wind power; single-area load frequency control; dynamic demand control; H_∞ performance analysis; PEV; state-space models; active power balancing; vehicle-to-grid service; closed-loop LFC scheme; smart grid; plug-in electric vehicles

Subjects: Secondary cells; Wind power plants; Power system control; Secondary cells; Optimisation techniques; Optimisation techniques; Wind energy; Stability in control theory; Transportation; General transportation (energy utilisation); Optimal control; Frequency control; Control of electric power systems