What are the main challenges and opportunities for integrating VFDs with smart grids and microgrids?

Smart grids are the step forward to transitioning to connecting more distributed energy resources to the existing grid infrastructure in the short to medium term. The biggest challenge amongst this is either remaining a high inertia or transitioning to low inertia grid. Although smart grids can provide the necessary controls and protection to mix our energy resources, but for future economic sustainability a decisive decision should be made on the direction of our primary energy resources.

In agreement with these benefits, but caution should be taken with respect to harmonic loading on existing electrical infrastructures. The economic consequences in relation to adding more VFDs to electrical driven rotating plant needs to bring a balance and whole life cost payback. I feel, if the right initial Capital investments are made including filters and downstream systems designed for introducing more VFDs, the whole life costs in future investments will return quicker and offset the upfront capital expenditure with cost savings on the further downstream investments.

Need to be careful integrating VFDs into traditional protection schemes which rely on high levels of current to operate (e.g. instantaneous overcurrent). The way VFDs react to an output short circuit is to limit current by reducing voltage and/or frequency which may not be compatible with the way existing protection is meant to operate. Harmonic distortion can be mitigated these days. My preference is NOT to generate them (AFE rectifiers) rather than taking the cheaper option of diode rectifiers and then filtering the resulting mess but not all suppliers have the same view and the resulting problems with harmonic filters are well documented. VFDs work well with both synchronous and induction motors…not sure of the reason for this comment.

Yes, caution should be taken with respect to harmonic loading on existing electrical infrastructures. The economic consequences in relation to adding more VFDs to electrical driven rotating plant needs to bring a balance and whole life cost payback. I feel, if the right initial Capital investments are made including filters and downstream systems designed for introducing more VFDs, the whole life costs in future investments will return quicker and offset the upfront capital expenditure with cost savings on the further downstream investments.