GSDC: Grid-side Subsynchronous Damping Controller
It has become a great challenge to mitigate the unstable subsynchronous control interaction (SSCI) in practical series compensated wind power systems. A grid-side subsynchronous damping controller (GSDC) is developed, which consists of a subsynchronous damping controller (SDC) supplemented to a subsynchronous current generator (SCG). The GSDC utilizes bus voltages and line currents as feedback signals and injects currents at the subsynchronous frequency into the system to provide active damping. The parameters of the SDC and SCG are optimized for Guyuan wind power system. GSDC is the first of its kind SSO damper that has been installed in an actual system for suppression SSO. This work paved the way for the commissioning of a practical GSDCs in real-world systems experiencing unstable SSO.
RSDC: Rotor-side Subsynchronous Damping Controller
This work is based on the concept of reshaping the impedance response of type-3 wind turbines to provide positive resistance at the subsynchronous frequency. The proposed control scheme damps the unstable SSO caused by interaction between type-3 wind farms and series-compensated grids. A practical rotor-side subsynchronous damping controller (RSDC) is proposed. Its performance is not only verified through controller hardware-in-the-loop (CHIL) simulations but also demonstrated on actual four type-3 wind turbines in Lianhuatan wind farm in Guyuan wind power system. The results enhanced the practical confidence of the SSCI mitigation strategy based on RSC’s converter control modification.
INOSA: Impedance Network-based Oscillatory Stability Analyzer
Unstable subsynchronous oscillations (SSOs) may be excited due to adverse interactions between inverter-based resources (IBRs) and series-compensated or weak ac networks. The frequency-sweep impedance modeling and analysis method is widely used for scanning grid-tied IBRs against the risk of SSO. The stability of such a system is heavily influenced by system-wide parameters such as IBR dispatching conditions (input resource, and different dispatch scenarios), and network status (short-circuit and/or series-compensation levels). A MATLAB-based application package is developed, named impedance network-based oscillatory stability analyzer (INOSA). INOSA takes the available system parameters and frequency-scanned impedance data of each IBR device as input and processes it to carry out impedance network-based stability analysis under all operating conditions. The developed tool outputs key stability information such as damping and frequency of each oscillation mode, and a multi-dimensional security boundary/region plot that can be used to assess the risk of SSO.