Flexible LV Grid Interface for Controllable PV Production and EV Charging

The future of electricity distribution systems will become increasingly interconnected with the demand for heat  and transportation. Nowadays, two thirds of Europe’s heat demand at residential and service sector buildings are met by the combustion of fossil fuels (petroleum, natural gas, etc.). However, in  the future it is expected that Heat Pumps (HPs) will play an important role to meet the consumer heat demand thanks to its high “electricity to heat” efficiency. When it comes to energy demand  for transportation, 73% of all oil imported by EU member states is consumed by the transport sector. The European Commission forecasted that gradually replacing oil with cleaner transportation  alternatives could significantly cut down its oil import and CO2 emission. Adoption of cleaner mobility alternatives, such as Plug-in Electric Vehicles (PEVs), will lead to a low-carbon future transportation scenario. While the future energy demand from heat and transportation sector is expected to be supplied by electricity, the successful transition towards a sustainable, reliable and  affordable energy future is dependent on the clean energy production, such as renewables. A future electrification scenario is therefore envisaged in the LV network where renewable energy is produced by roof-top Photovoltaic (PV) panels, and consumer heat/transportation demand is satisfied by HPs and PEVs.

To cope with the envisaged future development in the LV network, where a high penetration of distinctive technologies (PVs, PEVs, and HPs etc.) appear in the LV feeders, a back-to-back converter concept, shown in Figure 1, is proposed to offer not only continuous voltage control capability but also additional control functions needed for the future. The concept itself provides LV and MV network decoupling, on the one hand it isolates the LV network from the MV network background harmonic distortion, and on the other hand the LV network can be supplied by DC storage device during MV network disturbances. In addition to active power regulation, the grid side converter can regulate the reactive power output and provide active filtering function on demand. Besides continuous voltage regulation capability, feeder side converter also possess frequency regulation capability,  which is essential for controllable PV production and EV charging. When resonance occurs in the LV network, feeder side converter can provide active damping and stable the LV network.

With the proposed control interface concept in Figure 1, a case study will be conducted in simulation software Powerfactory® to demonstrate the mechanisms and benefits of controllable PV production and EV charging. Depending on the progress of experimental work, more measurement/test results of the proposed flexible LV grid interface will be shown during the conference.