Funded by the U.S. Department of Energy, the $98 million Clemson Wind Turbine Drivetrain Testing Facility will include a 15 Megawatt Electrical Grid Simulation Laboratory with full-power real-time hardware-in-the-loop (HIL) simulation capabilities. Under construction in Charleston, South Carolina, the facility will be the largest of its kind in the world, capable of testing enormous 7.5 and 15 megawatt power equipment and wind turbines under stressful conditions. The facility will enable the ability to test any large power source that interacts with electric grids, including wind turbine motor/generators and inverters, solar inverters, medium voltage motors and motor drivers. This includes the ability to simulate, in real-time, the response of the electrical grid and closed-loop dynamic interaction with the equipment under test included full power simulation of normal and abnormal grid conditions. This will enable companies to do in weeks or months what now requires years of testing in the field, and perform comprehensive validation and verification testing under controlled laboratory conditions that would be impossible to achieve in the field.
At the facility a dedicated substation feeds 23.9 kilovolts to both a 15 megawatt and 7.5 megawatt test stand, enabling hardware-in the loop testing capability up to the 15-megawatt level using the bi-directional power flow inverters that enable controlled power to flow in either direction. The simulated grid is also 23.9 kilovolts. We also have inductors that can provide a load for a variety of tests including low voltage and zero voltage ride-through testing.
At the heart of the system are 15 megawatt multi-level bidirectional inverters controlled by numerous National Instruments Single-Board RIO embedded systems with Xilinx Spartan-6 hybrid DSP/FPGA devices. These devices contain programmable logic fabric and 58 DSP cores all in a single integrated circuit, yielding 40 times higher performance-per-dollar than conventional monolithic DSP control systems. The control software is written using the LabVIEW FPGA graphical system design environment, which enables high level graphical programming with Megahertz control performance and efficiency on the hybrid DSP/FPGA device that rivals hand written VHDL or Verilog code. No knowledge of low-level hardware description languages such as VHDL and Verilog is required. Each multi-level inverter cabinet comprising the system has the capability to control 2.5 megawatts of bidirectional power flow. The 24 kV utility bus goes through 4160 V step-down transformers for feeding into one inverter port and the 24 kV simulated grid bus is connected to the second port on the inverters through step-up transformers.
In addition to fundamental tests for wind turbines like low voltage and zero voltage ride through testing, the grid lab will be able to do very sophisticated testing of inverters, motor/generators and other electrical equipment such as smart reclosers and sectionalizers.
The instrumentation capabilities at the facility are provided by National Instruments PXI chasses with NI high speed data acquisition boards and data capture to GE reflective memory hubs and 24 terabyte array drive systems that enable real-time data sharing between the PXI system and other computers with just 1 microsecond of latency. All data is sorted in the TDMS format, an open format endorsed by NI that is ideal for very large data sets. We will use NI DIAdem to retrieve and plot the data and export to other formats such as Excel. All data is stored with a GPS timestamp so that slow and high-speed data can be combined and enabling all systems in the laboratory to be fully synchronized.
The facility also provides the ability to build and validate simulation models for components used in new smart grid, digital energy and renewable energy systems such as solar photovoltaic (PV) farms, grid-level energy storage systems, wind farms and even new technologies under development that have not yet been deployed to the grid.
National Instruments is coordinating with SRNL and Clemson to bring next generation FPGA-based real-time power electronics and grid simulation technology to the lab involving a range of technologies in development that have not yet been publicly released.
Want to learn more? Watch the entire IEEE Spectrum webcast, "Real-Time HIL Simulation of Grid-Tied Switched-Mode Power Systems":
Joe Cordaro is an Advisory Engineer in the Research and Development Engineering Section of Savannah River National Laboratory (SRNL). He is the SRNL Project Lead for the 15 Megawatt Drive Train Test Facility and the 15 MW Electrical Grid Simulation Laboratory.
