Dr Mark Davies

Team Leader System Performance

WG B4.62Connection of Windfarms to Weak AC networks

Experiences with low SCR connections

1. SVCs on long radial feeder

2. LCC HVDC with very low SCR (near 1 !!)

3. LCC HVDC with WTG interaction

4. VSC HVDC with WTG interaction

5. WTG with SCR < default requirement

Item 1: Risk - Understand & Define

• Generators that require a minimum SCR (e.g. HVDC or WTGs) by implication also create some system degradation.

Item 1 : Risk – Managing it• How can the system impact:

• be measured• extreme effects be mitigated and• a fair system of management be applied?

Item 2: Technical – The Challenges1. Make WTG synchronisation performance closer

to that of synchronous generators

2. Make WTGs behave more like synchronous voltage sources

Item 2: Technical – Improvements ?

• Due to their large ratings HVDC systems often operate with low SCR. Can WTG systems leverage off the experiences of these related power conversion devices?

• Two areas of synergy are:1. (re)synchronisation performance - (PLL delays)

2. fault current limitation