Mitigation of Subsynchronous Interactions in Hybrid AC/DC Grid With Renewable Energy Using Faster-Than-Real-Time Dynamic Simulation

Abstract

Transmission line capacity enhancement by series compensation is commonly used in power systems, which consequently faces potential subsynchronous interaction (SSI). In this work, faster-than-real-time (FTRT) simulation based on the fieldprogrammable gate arrays is proposed to mitigate the disastrous SSI in a hybrid AC/DC grid integrated with wind farms. Dynamic simulation is applied to the AC system to gain a high speedup over real-time, and a detailed multi-mass model is specifically introduced to the synchronous generator to show the electricalmechanical interaction. Meanwhile, the DC grid undergoes electromagnetic transient simulation to reflect the impact of power converters' control on the overall grid, and consequently, the EMTdynamic co-simulation running concurrently due to FPGA's hardware parallelism is formed. As the two simulations are inherently distinct, a power-voltage interface is adopted to separate them which enables their coexistence in one program. It shows that following the detection of a contingency, the FTRT hardware platform can generate an optimum solution with precisely quantified power flow changes in advance to keep the hybrid AC/DC grid stable. The FTRT efficacy is proven by a number of cases where the accuracy is validated by offline simulation tool Matlab/Simulink.

Faster than Real-Time Simulation: Methods, Tools, and Applications

“…The minimum amount of load that needs to be shed is predicted leveraging FTRT simulations and a digital replica of the system. Researchers in [11] present a vulnerability named subsynchronous interaction (SSI) introduced by capacitive series compensation when boosting the capacity of transmission lines in longdistance power delivery. SSI can result in severe overvoltage events and trip the associated transmission facilities [19].…”

“…FTRT approach: The increased complexity of higher-order differential equations requires more iterations for solvers to reach accurate solutions. To address these issues, the authors in [11] utilize a 4th order Runge-Kutta model to solve high-order (> 9th) DAEs. To achieve FTRT execution times, researchers in [2] propose a parallel execution of the system model that introduces a processor parallelism method for the 9-machine power system.…”

“…Due to their benefits, FPGA-based systems have been extensively used in FTRT implementations [2], [7], [11], [24]. For instance, an integrated AC/DC grid simulation is performed on a parallel FPGA-based architecture in [2].…”

“…The test system is divided into 11 sub-systems, while transmission lines are further divided into sub-sub systems achieving efficient calculation of the admittance matrices. The authors in [11] demonstrate that the AC/DC grid can be divided into three modules, wind farm, 4-terminal HVDC grid, and AC grid, in order to minimize the execution time leveraging different time-steps for each module. Moreover, the tasks within one module can be computed in parallel (e.g., converter control (CNT), converter average value model (AVM),and HVDC network inside the HVDC module).…”

Comprehensive Real-Time Hardware-In-the-Loop Transient Emulation of MVDC Power Distribution System on Nuclear Submarine

“…However, GPU suffers from the communication time latency between simulator processors (about one microsecond), which makes its real-time capability unfeasible for the emulation. Differently, FPGA can conduct the real-time emulation in parallel with optimized block-to-block communication width and speed, which has been proven in the area of transportation electrification [11], renewable energy [12], power transmission and distribution [13], power electronic devices [14]- [16], etc.…”