Synchronverters: Grid-friendly Inverters that Mimic Synchronous Generators
As discussed in Chapters 3 and 15–17, the current paradigm in the control of inverters associated with renewable energy sources is to extract the maximum power from the power source and inject it all into the power grid using current-controlled inverters; see for example (Busquets-Monge et al. 2008b; Carrasco et al. 2006b; Ekanayake et al. 2003). This is a good policy as long as such power sources constitute a negligible part of the grid power capacity. Indeed, any random power fluctuations of the renewable power generators in this case can be compensated for by the controllers associated with large conventional generators because some of these generators are dedicated to take care of the overall power balance, system stability and fault ride-through. When the penetration of renewable power generators reaches a certain level, such “irresponsible” behaviour will become untenable. In responding to the daily increasing share of electricity generated from distributed generation and renewable energy sources, it is important for these sources to feed power to the grid in the form of voltage sources instead of current sources, in a way similar to the conventional power generators (Brabandere et al. 2007; Loix et al. 2007; Piagi and Lasseter 2006; Sao and Lehn 2005). This is particularly true when the grid is weak or when an inverter or a microgrid works in the stand-alone mode.
In this chapter, the idea of ...