TransGrid Solutions collaborated with its client to develop an Automatic Voltage Setpoint Optimizer (AVSO) to improve the stability and efficiency of a radial wind farm transmission system known as Gen- Tie, to which multiple wind farms and a STATCOM with equipment from different manufacturers were connected. The AVSO automates routine voltage coordination tasks, reducing operator workload, lowering the potential for reactive power oscillations within the system. The AVSO achieves this by adjusting the voltage references to each wind farm and STATCOM, based on voltage deviations from the voltage setpoint of the root substation of the Gen-Tie.
The AVSO's operating parameters are highly customizable and modifiable at any time, and operators can define custom high and low limits for voltage regulation for each facility as well as the size of the discrete voltage step issued by the AVSO.
The RTDS hardware-in-the-loop (HIL) test setup included the RTACs that implemented the AVSO, the redundant AVSO, and other automatic voltage controllers that controlled the switched capacitor and reactor banks. All components were connected to the simulator using Ethernet. The communication protocol used was DNP3. A protocol translator was also required to match master-slave hierarchy requirements. The RSCAD simulation case included an equivalent model of the AC network, the transmission lines, each wind farm, and the STATCOM.
Extensive simulations of real-world operating scenarios were carried out under different conditions that covered voltage steps, power ramps, facility trips, line trips, energization, loss of signals, changeover between primary and back-up controllers, and a continuous 8-hour load profile test. The first phase of the project included adding more features and debugging the AVSO algorithm, using the insights gained into the power system. The second phase was performing live Factory Acceptance Tests to a witness panel that included system operators.
With the AVSO in service, the fixed capacitor banks saw an 83% reduction in switching operations. The AVSO has achieved its objectives including narrowing the voltage band at the root substation of the Gen Tie and improving the operating voltage profile on the facilities.
The entire project was carried out at the height of the COVID-19 pandemic. Instead of meeting in-person, the witness panels joined video conferences and witnessed the live tests. The AVSO project demonstrated how RTDS HIL tests allow to test the product at rare but critical system conditions, which give development teams better understanding of the controller algorithms in relation to the applied power system. The HIL testing established the confidence of the utility planners, and network operators on the ability of the AVSO in achieving the set objectives.
Akbo Rupasinghe, TransGrid Solutions