Inertia compensation scheme for wind turbine simulator based on deviation mitigation

Abstract

Wind turbine simulator (WTS) is an important test rig for validating the control strategies of wind turbines (WT). Since the inertia of WTSs is much smaller than that of WTs, the inertia compensation scheme is usually employed in WTSs for replicating the slow mechanical behavior of WTs. In this paper, it is found that the instability of WTSs applying the inertia compensation scheme, characterized by the oscillation of compensation torque, is caused by the one-step time delay produced in the acceleration observation. Hence, a linear discrete model of WTS considering the time delay of acceleration observation is developed and its stability is analyzed. Moreover, in order to stably simulate WTs with large inertia, an improved inertia compensation scheme, applying a first-order digital filter to mitigate deviation response induced by the time delay, is proposed. And, the criterion for selecting the filter coefficients is established based on the stability condition analysis. Finally, the WTS with the proposed scheme is validated by simulations and experiments.

Optimal torque control based on effective tracking range for maximum power point tracking of wind turbines under varying wind conditions

“…It includes a direct current motor (DCM) driven by a DCM drive, a flywheel, and the simulation program running in a Beckhoff programmable logic controller (PLC). The simulation program mainly contains the scaling transform for scaling down WPGS's operational quantities to the motor scale [23], the aerodynamic simulation algorithm for calculating aerodynamic torque, and the rotor inertia compensation algorithm for mimicking the slow mechanical dynamics of real wind rotors [25]. By combining the deployment of flywheel [24] and the simulation program, the aerodynamic behaviour and wind rotor dynamics of the CART3 turbine with large inertia can be simulated by the WTS. Electrical part which is the same as for the WPGS, consists of a permanent‐magnet synchronous generator (PMSG) and its grid‐connected convertor (including generator‐side rectifier and grid‐side inverter).…”

Inertia compensation scheme of WTS considering time delay for emulating large‐inertia turbines

“…kΔt and (k + 1)Δt. Substituting 10into 9, acceleration in the compensation loop is actually calculated by [5] α comp (k) = α(k − 1) .…”

“…Without consideration of the communication delay, an inertia compensation scheme utilising a first-order filter is proposed [5] and accordingly the stability boundary of a closed-loop WTS employing this scheme is theoretically derived as [5]…”

“…The slow response of WT to wind speed fluctuation is caused by its high rotor inertia. Since this exerts a significant influence on the design and operation of control strategies in WECS such as maximum power point tracking (MPPT) control [1, 2] and active power control [3], the WTS should replicate the mechanical behaviour of a real WT [4–7]. However, because the moment of inertia of WTS (denoted by ) is much smaller than the one for emulating WT dynamics (denoted by ), an inertia compensation scheme is usually implemented in WTS to simulate the slow mechanical behaviour of a real WT [6–8].…”

“…Stability is necessary for a practical WTS. However, it has been revealed that when simulating real turbines with high rotor inertia, the WTS with the inertia compensation scheme is unstable, resulting in the oscillation of compensation torque [4–7]. To avoid instability, the ratio of to () should be less than a critical value, which is proved to be 2.0 when applying the conventional inertia compensation strategy [4].…”