Safe Automation supports “Zero Emission Mobility”

Fast charging is the goal and the challenge

Elec­tric vehi­cles (e‑vehicles) are shaping today’s urban land­scape. Charging sta­tions are now more common on com­pany premises and in shop­ping cen­tres. Elec­tric charging is also part of the green vision of the future for HGV fleets. The common goal: to reduce emis­sions. The common chal­lenge: how to imple­ment a modern parking system, including charging sta­tions, which is safe and effi­cient for everyone involved? And what automa­tion and safety tech­nology must be behind it?

To charge e‑vehicles, you need elec­tricity – that’s log­ical. How­ever, when it comes to the ques­tion of whether to use alter­nating cur­rent (AC) or direct cur­rent (DC), tech­nical opin­ions vary. One thing is absolutely clear: both work. Nev­er­the­less, DC charging has some key advan­tages over AC charging. The main argu­ment: faster charging in higher power ranges. A safe cir­cuit, con­sid­er­a­tion of all safety com­po­nents and modern con­trol tech­nology are all pre­req­ui­sites. The safety con­cept must also include all pos­sible safety aspects and the safety require­ments must relate to both the DC cur­rent net­work and the AC cur­rent net­work.

DC charging has consequences for safety

This is where Pilz, the automa­tion and safety tech­nology expert and long-standing partner of W.E.B, joined the party. In the “MADELAINE” demo system (Multi-Adap­tive DC Elec­tric Vehicle Charging Infra­struc­ture Net­work), the PSSuni­versal PLC con­troller from the automa­tion system PSS 4000 acts as the cen­tral instance for safety. One of the main argu­ments for using it was the option to use the Struc­tured Text pro­gram­ming lan­guage in the safety sec­tion. The PSSuni­versal PLC also offers two basic func­tions: it min­imises the like­li­hood of errors occur­ring in the system and, in the event of a mal­func­tion, ensures that the system is brought to a safe state. Both are essen­tial aspects when charging e‑vehicles. This safety con­cept reli­ably ensures that the safety devices take into account the charging mod­ules on both the AC net­work side and the DC side.

Control all-rounder guarantees safety

In the MADELAINE parking charging system, the PSSuni­versal PLC also mon­i­tors the power dis­trib­utor: it is needed to con­nect the switching matrix in such a way that the defined, selected charging mod­ules for charging are con­nected to the cor­rect charging points. In addi­tion to estab­lishing these cor­rect power con­nec­tions, the safety PLC must also manage the other safety devices, such as the emer­gency stop cir­cuits.

The aim of the parking charging system is to pro­vide a future charging solu­tion, which will allow charging to be as flex­ible as pos­sible via a large number of delivery points, i.e. charging sta­tions. Secure switching of the DC con­nec­tions is a core ele­ment of the MADELAINE project. The spe­cial factor: the five charging mod­ules used in the parking charging system can be con­nected in par­allel and the respec­tive charging mod­ules can be oper­ated indi­vid­u­ally. This means that five parking spaces can be charged with 10 kW each. It should be remem­bered that behind each charging module that is con­nected in par­allel, there must be a DC con­tactor. PSSuni­versal PLC is on board for exactly this pur­pose: it can be used to con­trol the switches safely.

Going “green”, step-by-step

MADELAINE had sev­eral project stages: the first saw the devel­op­ment of the entire net­work archi­tec­ture and asso­ci­ated wiring, plus an analysis of the optimum ratio between the number of charging mod­ules and parking spaces. A demon­stra­tion system with five charging mod­ules and ten charging points at the W.E.B site was the next stage, where the planned size of a charging module was based on a DC output capacity of 10 kW. By con­necting five charging mod­ules in par­allel, up to 50 kW can be pro­vided on a single parking space. The demo oper­a­tion focused on load man­age­ment and opti­mi­sa­tion of the site’s own require­ment. Then an exten­sive test phase for the parking system under lab­o­ra­tory con­di­tions was started in 2023. Firstly, testing was car­ried out without power, i.e. only the soft­ware was tested. Then switching enables were pro­vided and par­allel oper­a­tion was exam­ined under power. The data was logged, analysed and doc­u­mented within the frame­work of the project require­ments. Finally, at the end of Sep­tember 2023, the first charging oper­a­tion could be car­ried out with the vehi­cles.

Another essen­tial fea­ture in this con­text is a ded­i­cated charging app. The automa­tion system PSS 4000 solu­tion scored points here too, because the PSSuni­versal PLC con­troller can be pro­grammed in the stan­dard­ised IEC EN 61131 automa­tion tech­nology lan­guages, so that users don’t have to learn a new lan­guage. That really makes the work easier, the project team at W.E.B con­firms.