VIZIMAX has recently released a paper on wind farm controller called Voltage Master Control System for Wind Farms. Written by two VIZIMAX experts (Marc Lacroix Eng. M. Eng. and Michel Mont-Briant Eng.), in collaboration with EDF Canada (Francis Chartrand Eng. M. Eng.), this paper was presented this month at PacWorld Conference in Slovenia.

The wind farm POC is a 161 kV HV transmission line where the electrical
quantities are measured using a Phasor Measurement Unit (PMU). The PMU acquires a three-phase voltage (Vpoc) and three-phase current (Ipoc), extract and filters the nominal power signal to calculates its frequency, the rate of change of frequency (ROCOF) and the positive sequence voltage and current.

This paper, a portion presented here,  describes the Power Plant Controller (Voltage Master Control Systems) installed in a new wind farm commissioned during fall 2015. Renewable Energy power plants such as Wind and Solar farms are subject to utility grid code compliance especially in regards to voltage control. This control is done by either generating or absorbing reactive power (VAR) at the Point of Connection (POC).

This could mean installing complex and costly STATCOM (Static synchronous Compensator), Static VAR Compensators (SVC) and/or mechanically switched loads like capacitor banks and/or shunt reactors. Furthermore, some installations also have energy storage systems that could benefit integration with a unified control system. Some energy production sources rely on electronic inverters to convert asynchronous or DC generators to synchronous AC. By default, those inverters can act as reactive power generators to either supply or absorb VAR.

The installed PPC measures the active and reactive power generation at the point of connection and use the wind turbines inverters to perform voltage regulation. The PPC also controls the installed mechanically switched loads. To meet the stringent system performance requirements, the PPC uses a Phasor Measurement Unit (PMU) to precisely acquire the voltages and currents at the point of connection and calculate synchrophasor quantities. The substation automation controller receives those IEEE C37.118 phasor frames 120 times per second, twice the network frequency, and calculates the required compensation based on proportional-integral-differential (PID) loops.

The VAR set point calculated by the PPC is communicated to the wind turbines inverters via the turbine power management system. The extra reactive power that exceeds the wind turbines inverters production capacity can be obtained with the integration of low-cost MSR and MSC in the farm. The PPC is supplied with a local human-machine-interface (HMI) with animated graphics that displays the status of the regulation system. It also provides a means to set the PPC regulation strategy in voltage, VAR, or Power Factor regulation.

The PPC integrates a communication interface to exchange data with the wind farm and Utility SCADA systems using either MODBUS, DNP3, IEC60870 or IEC61850 protocols. To guarantee its maximum availability, the PPC hardware is fully redundant (hot standby configuration) allowing the equipment to be serviced while in live operation. The system will be tested with the TSO during spring 2016 to demonstrate that it can contribute to the control of the voltage at the Point of Connection (POC), in a dynamic, continue and reliable way, as required by the grid code.

For the rest of the paper: https://www.vizimax.com/media/files/OP049.pdf