1. Didden, M BE Session 2 – Block 3 Barcelona 12-15 May 2003 1 Considerations to choose the appropriate voltage sag mitigation device M. Didden, K.U.Leuven - Energy Institute marcel.didden@mech.kuleuven.ac.be

2. Didden, M BE Session 2 – Block 3 Barcelona 12-15 May 2003 2 Introduction -If process modifications are not possible, mitigation equipment between process and grid can be considered -General guideline before comparing different options: C inv initial investment per kVA, f annual outages due to sags, p prev percentage of outages being prevented, f·p prev annual mitigated outages, C sag outage cost per sag per kVA, p mnt annual maintenance costs per kVA as a percentage of C inv, idiscount factor, nproject time (a).

3. Didden, M BE Session 2 – Block 3 Barcelona 12-15 May 2003 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. Didden, M BE Session 2 – Block 3 Barcelona 12-15 May 2003 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. Didden, M BE Session 2 – Block 3 Barcelona 12-15 May 2003 5 Conclusions The techno-economic best solution: - Flywheel/ - On-line UPSif all sags have to be mitigated for - DVR with energy reserve/ - DVR without energy reserveif no DC-bus - Statcom/ - Shunt connected SMno DC-bus + other PQ issues - Boost Converterif DC-bus, no other PQ-issues - Active Front Endif DC-bus, other PQ-issues - Transformerless series injectorno DC-bus, no other PQ-issues