PVCharge – Multifunctional power electronics for PV car parks: Genuine PV charging and grid-supporting functions through optimised hardware and intelligent control

By connecting a bidirectional charging point directly to the DC terminals of the PV system downstream of the MPP tracker (Fig. 1b), three key advantages could be realised: 

• By bypassing the inverter and rectifier stages in PV-driven DC charging, two conversion steps – and the associated losses – are eliminated. Together, these can easily amount to 3–5 per cent of the PV rated power, thereby making a significant contribution to energy and system costs. 
• Direct DC coupling eliminates the need to use the public AC grid, which can avoid grid charges where applicable and reduce the grid load at the connection point. This therefore has a positive impact on costs for end users as well as on the stability of the (AC) power system. 
• Connecting an entire PV charging string via an AC grid connection with an additional grid-forming function can have a positive impact on grid stability due to the combined energy output of the PV generator and the bidirectional charging systems, by providing inherent positive/negative control energy and reactive power. 

However, this dynamic PV-controlled charging requires an intelligent control system that determines the available solar power in real time and transmits this information to the electric vehicle’s charger. This ensures that self-generated solar power is utilised optimally and that the draw on the grid is minimised. This not only leads to a reduction in energy costs but also to a reduction in CO₂ emissions.

As part of this project, H-BRS is developing the MPPT converter, which acts as an MPP tracker whilst also ensuring stable operation of the DC distribution system. Furthermore, this converter is being further developed into a DC matching stage, as part of an RCP system. This is intended to replicate the behaviour of electric vehicles. This enables the simulation of various usage profiles and the investigation of their impact on the distribution system.