Considerations to choose the appropriate voltage sag mitigation device

1

• Considerations to choose the appropriate voltage
  sag mitigation device
• M. Didden, K.U.Leuven - Energy Institute
• marcel.didden_at_mech.kuleuven.ac.be

2

• Introduction
• - If process modifications are not possible,
  mitigation equipment between process and grid
  can be considered
• - General guideline before comparing different
  options
• Cinv initial investment per kVA,
• f annual outages due to sags,
• pprev percentage of outages being prevented,
• fpprev annual mitigated outages,
• Csag outage cost per sag per kVA,
• pmnt annual maintenance costs per kVA as a
  percentage of Cinv,
• i discount factor,
• n project time (a).

3

• Considerations (1/2)
• Mitigation concept
• 1) Full protection during a sag, the load is
  completely fed by an external energy source
• 2) Relative protection the voltage is raised by
  a certain percentage, implying that the immunity
  of the equipment is enhanced by the same
  percentage
• 3) Absolute protection the process will be
  protected against sags of a certain depth.
• !!! It should be taken into account that the
  amount of reduced process outages using this
  protection highly depends on the initial immunity
  of the process

4

• Considerations (2/2)
• Price
• - Initial purchase price
• - Standby cost
• - Maintenance (moving parts, batteries)
• Other PQ-problems
• Some applications are able to solve problems such
  as voltage harmonics, current harmonics, flicker
  and controlling reactive power.

5

• Conclusions
• The techno-economic best solution
• - Flywheel /
• - On-line UPS if all sags have to be mitigated
  for
• - DVR with energy reserve /
• - DVR without energy reserve if no DC-bus
• - Statcom /
• - Shunt connected SM no DC-bus other PQ issues
• - Boost Converter if DC-bus, no other PQ-issues
• - Active Front End if DC-bus, other PQ-issues
• - Transformerless series injector no DC-bus, no
  other PQ-issues