Industrial Embedded – Equipment Control – VAR Compensator

Background

The U.S. power grid is a large electrical circuit that, although has some amount of isolation between loads, is certainly interconnected at drop points, which is what customers care about most.

SVCs are generally worth considering in scenarios where large electric motors are being utilized (e.g. mills, recycling plants, mines). Problems such as voltage sag, voltage flicker, and current harmonics can cause reduced motor torque, lights to flicker, and equipment damage.

Challenge

T-Star has significant domain expertise in stabilizing medium voltage power systems. Viewpoint has significant domain expertise in the realm of measurement and control systems. The team at T-Star needed a well-supported intelligent device for their new generation Static VAR Compensator (SVC). They wanted a highly reliable solution that had minimized the time-to-market and a highly predictable future migration path for higher volume production. They also needed multi-channel precision timing, and high speed logging in a device certified for operation in dirty industrial environments.

Solution

Viewpoint was asked to develop the controller for T-Star’s Static VAR Compensator (SVC) using a carefully constructed specification. The chosen controller platform is a National Instruments (NI) Compact RIO due to its modular feature set, networking capabilities, and associated supportability and quality that comes with an industrial-grade off-the-shelf controller. T-Star and Viewpoint have made very complementary GSD (Get Stuff Done) teammates.

As the grid gains intelligence, this class of smart/dynamic power quality system will likely become more critical.

Benefits

• The platform supports other future configurations that are outside the phase one scope of this project.
• Time-to-market is critical for T-Star. The initial proof of concept was completed in weeks.
• The Linux-based OS, well known in the embedded community, provides a rich ecosystem for enhanced usability (e.g. network stack), and real-time operation.
• Secure access through VPN with built-in firewall and user account control and permissions allows for remote diagnosis, health monitoring, and gathering of online information.
• An FPGA allows for deterministic timing and parallel processing.
• With COTS hardware, future upgrades are simplified with code base reuse and recompiling for new hardware.
• The NI platform provides a migration path to a lower-cost solution once hardware configurations are locked down and production volumes increase above a certain level.
• The NI control hardware is certified (certifications in the domains of CE, FCC, UL, etc.) for marine applications and other challenging environments.

System Overview

The SVC tunes a highly inductive load by dynamically injecting a variable amount of capacitance due to the measured load. Voltage and current sensors feed a series of control algorithms which determine the voltage and current imbalance in order to inject the appropriate amount of capacitance into the power system. This algorithm acts on a cycle-by-cycle basis. The figure below illustrates the system makeup.