Hybrid Controller for Wind Turbine Generators to Ensure Adequate Frequency Response in Power Networks

Abstract

Converter-interfaced power sources (CIPS) are hybrid control systems as they may switch between multiple operating modes. Due to increasing penetration, the hybrid behavior of CIPS, such as, wind turbine generators (WTG), may have significant impact on power system dynamics. In this paper, the frequency dynamics under inertia emulation and primary support from WTG is studied. A mode switching for WTG to ensure adequate frequency response is proposed. The switching instants are determined by our proposed concept of a region of safety (ROS), which is the initial set of safe trajectories. The barrier certificate methodology is employed to derive a new algorithm to obtain and enlarge the ROS for the given desired safe limits and the worst-case disturbance scenarios. Then critical switching instants and a safe recovery procedure are found. In addition, the emulated inertia and load-damping effect is derived in the time frame of inertia and primary frequency response, respectively. The theoretical results under critical cases are consistent with simulations and can be used as guidance for practical control design.Index Terms-System frequency response, deadband, hybrid system, inertia emulation, primary frequency support, safety verification, sum of squares decomposition, semidefinite programming, wind turbine generator.

Review on set-theoretic methods for safety verification and control of power system

“…This supervisory control can not only generate switching commands, but also provide real-time margin for a critical safe switching. The works in [16], [17], [40], [41] have taken this advantages.…”

Set Theory-Based Safety Supervisory Control for Wind Turbines to Ensure Adequate Frequency Response

“…From the theoretic aspect 1) Based on the definition of region of safety (ROS) in [35], this paper formally defines the largest ROS (LROS), and interprets the relation between the true backward reachable set and the LROS. 2) Based on the occupation measure and corresponding formulations in [36], where the time-dependent backward reachable set is estimated, this paper modifies the formulation to calculate the invariant backward reachable set, and first provides the geometric interpretation.…”

“…2) Based on the occupation measure and corresponding formulations in [36], where the time-dependent backward reachable set is estimated, this paper modifies the formulation to calculate the invariant backward reachable set, and first provides the geometric interpretation. The introduction of this theory guarantees L-1 norm convergence to the true LROS as a significant improvement from the framework in [35].…”

“…where s(t − t 1 ) denotes that the IE mode is activated at t 1 . response models can be found in [35]. The term k ie is the IE gain.…”

Coordinated Control of Wind Turbine Generator and Energy Storage System for Frequency Regulation under Temporal Logic Specifications

“…Line impedance (pu) Line charging (pu) 2-8 (2)(3)(4)(5)(6)(7)(8)(9) j0.01 0.0006625 7-8 (7)(8)(9) j0.04 0.0023 4-8 (4)(5)(6)(7)(8)(9) j0.03 0.0031 4-5 j0.03 0.0034 5-6 j0.03 0.0094 6-7 j0.02 0.0258 of the stochastic robust neighbourhoods in the dimension of the grid frequency variationδ i * 1,1 (δ i * 1,1 =δ i * 1,2 =δ i * 2,1 =δ i * 2,2 ) are much smaller than the outer bounds in the dimension of the wind turbine rotor speed variationδ i * 1,3 (δ i * 1,3 =δ i * 1,4 ). Aŝ δ k,i = ( √ r q i + √γ )/z k,i andγ = 100M q 0 (3, 3), minimizinĝ δ 1,1 can be achieved by minimizing M q i (3, 3) (i = 1, 2, 3) and maximizing z i 1,1 .…”