Modular Embedded System Shortens Development Time in Static VAR Compensation System

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"We chose CompactRIO because of its FPGA performance, deterministic timing, networking capabilities, and associated supportability in an industrial-grade, off-the-shelf controller."

- David LaVine, Viewpoint Systems

The Challenge:
Designing a well-supported intelligent device for a T-Star new-generation static Volt Ampere- Reactive (VAR) compensator (SVC). T-Star wanted a highly reliable solution that minimized time to market and offered a highly predictable future migration path for higher-volume production. It also needed multichannel precision timing and high-speed logging in a device certified for operation in dirty industrial environments.

The Solution:
Developing a controller using a carefully constructed specification, we chose CompactRIO because of its FPGA performance, deterministic timing, networking capabilities, and associated supportability in an industrial-grade, off-the-shelf controller. The U.S. power grid is a large electrical circuit that has some amount of isolation between loads, but is interconnected at drop points (which is what customers care about most). SVCs are generally worth considering in scenarios that use large electric motors, such as mills, recycling plants, and mines. Here, problems such as voltage sag, voltage flicker, and current harmonics can cause reduced motor torque, flickering lights, and equipment damage. As the grid gains intelligence, smart/dynamic devices like the SVC will maintain power quality on a distributed basis throughout the power system.

Author(s):
David LaVine - Viewpoint Systems

Figure 1. Cabinets for an SVC Located at a Remote Mine in British Columbia

 

Figure 2. Inside an SVC

 

T-Star has significant domain expertise in stabilizing medium-voltage power systems. Viewpoint has significant domain expertise in measurement and control systems. Thus, T-Star selecting Viewpoint to develop the controller for its SVC was a natural fit.

System Overview

The SVC offsets highly dynamic loads, continuously injecting variable amounts of reactive power, “cancelling” the impact of the load on the power system. Voltage and current sensors feed a series of control algorithms that determine the voltage and current imbalance and calculate the proper amount of reactive power to inject into the power system. The algorithm uses high speed analog data to adjust the system cycle-by-cycle.

The NI-based hardware consists of:

  • An NI cRIO-9068 controller
  • An NI 9205 for voltage and current measurement
  • An NI 9403 for high-speed digital output
  • An NI 9403 for high-speed digital input
  • An NI 9375 for general-purpose status and command bits

Figure 3 illustrates the system makeup:

Figure 3. System Makeup

 

System Benefits

There are many benefits to this system:

  • The platform supports other future configurations outside the phase-one scope of this project
  • Time to market was critical for T-Star. The initial proof of concept was completed in weeks
  • The Linux OS, well-known in the embedded community, provides a rich ecosystem for enhanced usability (such as a network stack) and real-time operation
  • Secure access through a virtual private network with built-in firewall and user account control and permissions allows for remote diagnosis, health monitoring, and online information gathering capabilities
  • An FPGA offers deterministic timing and parallel processing
  • With commercial off-the-shelf 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 for marine applications and other challenging environments

Author Information:
David LaVine
Viewpoint Systems
800 West Metro Park
Rochester, NY

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