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Dynamic Load Management

EV Charging Station synchronization within an Electrical Capacity limitation

EV Charging Load Management Introduction

  • In the context of Electric Vehicle charging, Load Management refers to optimizing a property’s available electrical capacity to be able to manage discretionary controllable loads, such as EV Charging – when installed en masse.  As opposed to Load Sharing, which is the ability for an EV Charging Station to share it's total capacity across it's connector outlets.

  • There a number of different approaches to Load Management used in the market to ensure that the use of an EV Charger does not risk overloading and blowing the fuse of the property when used.  Each approach comes with its own advantages for a particular application, as well as potential constraints.  These approaches are summarized as follows. 

  • To assist with the explanation, imagine this scenario:

    • You are the Property Manager of an Apartment/Commercial building, and have been asked to implement EV Charging facilities in the building.

    • The building has four carparking floors, with 24 x carparking bays on each floor.  96 x bays total.

    • Today, there are 10 x EV already parked in the building, scattered around different floors.

    • The electrical switchboard for the Common Area building supply currently has a spare chamber and a 'confident' available electrical capacity of 250 Amps.  A load study, conducted by your Electrician (or Charge Hub), has identified that the building load peaks both in the morning and early evening.  Outside of these times, an electrical capacity of approx. 400 Amps could be available for EV Charging.

    • Through experience, a bit of Googling and industry advise, you understand that most currently available Electric Vehicles could charge on a three-phase AC 22kW station and receive approx. 11kW (16A) max, and take approx. 4 hours to charge.  You are also aware that the average EV has approx. 400km range on a full charge, therefore would only need to plug in once or twice per week.

Therefore, your various options to tackle the above scenario would be:

 

  • Static Load Limit:

    • A Static Load Limit is defined as a fixed current limit.  It could be as simple as setting a lower fixed limit on one or multiple EV Stations at the commissioning stage.

    • In the context using the above scenario, you could install 10 x 22kW AC Stations close to and connected with each other, with a Set Static Load Limit of 250 Amps.  Knowing that 10 x EV all charging together would only draw (10 x 16A) 160 Amps total, however the 250 Amp limit would be the safe limit.  15 x EV Stations could happily be installed and work all together under this Static Limit.  In reality, 30 x EV Stations could operate happily under this limit, as it would be rare for 50% or more of the Stations to all be operational at the same time.

    • The catch with using a Static Load limit is that your building will be restricted to the same OEM EV Station model - no choice.  Static Load Limit is usually an OEM feature, that is not controlled by measurements or an an external third party device.  i.e., EVBox BusinessLine can operate in a Hub / Satellite configuration with up to 20 x Stations per group. 

    • If your site requires consistency, has the available electrical capacity, and is unlikely to install more than 20 x Stations on site, then a Static Limit could be ideal.  Note however, that we could easily start with a Static Limit and move to a Dynamic Limit at a later date, as your EV uptake increases.  

 

  • Dynamic Load Limit:

    • A Dynamic Load Limit is defined as a moving/variable current limit.  i.e., 200 Amps is calculated to be available right now, but then 300 Amps is available in 10 mins, when other loads are switched off.

    • A 'Smart' EV Charging Station can have its output ramped up and down, either directly or via the connected OCPP (Open Charge Point Protocol) backend software, such as Charge Hub.

 

  • The fundamental approach for Dynamic Load Management is:

    • Ideally, connect the onsite EV Stations to OCPP software (such as Charge Hub), so that the Stations output can be monitored and managed.  Which requires a reliable internet connection.

    • Install a Dynamic Load Management Hardware device within the onsite electrical switchboard/s, which includes a measurement device/s (Current Transformer) to measure the incoming mains connection load, and the non-EV Station load.  A calculation is provided from the measurements to determine how much electrical capacity (Amps) remains for EV Charging.  The value is communicated directly to the EV Charging stations in a localized control, or back to the Charge Hub software, via a controller, and then relayed to the onsite Charging Stations.

 

Here is when we start getting into some detail:

 

  • OEM Specific Dynamic Load Management:

    • Many of the various EV Charging Station OEM have their own Dynamic Load Management device/system.  For example, a group of EVBox BusinessLine can be connected to a Smappee Infinity device for sending a dynamic load management signal to the Hub unit, that will then control the group of Satellites below it.   The Schneider Pro AC has the LMS device.

    • The limitation with this approach is that only the same OEM Stations can be managed by the same OEM load management device.  None can manage AC and DC Stations together under the same scheme.  Meaning that if the Schneider LMS system is installed in your premises, then you can only install Schneider EVLink Stations now and going forward.  

  • Agnostic Dynamic Load Management:

    • The alternative approach is to install an agnostic (open to all OEM Stations) Dynamic Load Management system.  Such as the Charge Hub FLEX.

 

  • The Charge Hub FLEX operates as follows:

    • Each installed EV Station is connected to the Charge Hub Backend.  

    • A DTM (Measurement Device) is installed, at a minimum, with one set of Rogowski coil CTS around the incoming main supply, and second set around the EV or non-EV load.  Note that the DTM must be connected to outside communications via either IOT Networks, 3/4G, Wi-Fi and Ethernet.

    • Controller - If there is only one EV Charger on the site to be load controlled, i.e., a large DC Station, then a FLEX Controller is not required.  However, a controller is required if there is more than one station on site to be managed together.

Charge Hub FLEX - Measurement Device

  • The Charge Hub FLEX is developed in partnership with WMAC Cloud.

  • A Charge Hub FLEX Measurement Device (DTM) consists of the measurement box (200 x 95 x 45mm), radio and up to 8 x sets of 1000A Rogowski CTs, all connected into the same device.  The DTM requires an internet connection.  Powered off the mains in the switchboard.  It communicates to the EV Controller via RS485.  Any allowable levels of phase imbalance and power quality measurements are also set as part of the initial installation.

  • The purpose of the DTM is to measure and monitor the electrical load at vital parts of the electrical infrastructure and provide a calculated 'load instruction' to the EV Charger Controller.

 

  • Understanding Electrical Utility Tariffs:

    • Fixed Charge - A fixed $/day charge applied to each energised connection point where energy or demand is recorded.  

    • Volume Charge - Is a flat or variable charge for energy consumed at a connection point, calculated in $/kWh:

      • Flat volume charge - A flat or single volume charge, meaning the same price is charged for energy consumed regardless of when the energy is consumed.

      • Time of Use (ToU) - A price charged for energy consumed that changes at different times of the day. Prices are lower during Day (Off Peak) Hours and higher during Evening (Peak) Hours. These charges are designed to reduce demand on the network during peak times by encouraging customers to switch non-essential electricity consumption to other periods.  

    • Demand Charge - A monthly demand charge calculated as a $/kVA/month or $/kW/month, for demand recorded at a connection point. Which could be a single peak recorded anytime in the month, or the maximum demand recorded within a peak demand window.  

  • Therefore:

    • The first set of DTM CTs are connected around the Main Building supply, to monitor and manage any potential increase in Demand Charges that may be caused by EV Charging.

    • The second set of DTM CTs are installed around the supply to the Common Area Metered Switchboard, that would then supply the new EV Switchboard.  

    • The third set of DTM CTs are installed around the supply to the EV Switchboard (EVDB).  Additional sets of CTs are installed on every individual EV Switchboard supply, if multiple are installed i.e., one EVDB per floor.

  • The DTM:

    • Takes all measurements and set points into consideration and communicate a total system allowable load value to an EV Controller on a regular basis.  

    • Can be set up to take instruction from the BMS (Building Management Systems), or directly from the local Electrical Utility, for intervention with temporary lower limits.

    • Will predict in advance possible load forecast, based on historical data.

    • Could also be installed on site from Day 1, to form part of the load study.  To then remain in place in its function as the measurement device for the Dynamic Load Management system.  

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Charge Hub FLEX - Controller

  • The Charge Hub FLEX EV controller is required as part of your installation if there are more than one EV Charging Station to be load managed on site.

  • The EV Controller connects to the DTM via RS485, and requires and internet connection.  Powered by a 240V plug or 12VDC.

  • The EV Controller then connects to each of the EV Charging Stations via ethernet or RS485.  Noting that an ethernet connection will require a cable from the multi-port switch in the EVDB to each Station.  Where a RS485 can loop between each Station, saving the additional cable run.

  • If a direct connection to the Charging Station is not available, then the EV Controller communicates to the charger via OCPP 1.6, via the Charge Hub software.

  • Each Station is programmed into the EV Controller, together with its details, ChargePointID and desired Charging Profile - i.e., peak demand periods to avoid etc.  Up to 200 stations.

  • The EV Controller can take an input from the Fire Panel to switch off all onsite EV Chargers, in the event of an alarm.

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Alternative EV Controller - Versinetic LinkRay

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  • The Versinetic LinkRay is a localised load balancing solution.

  • The LinkRay sits between the Charging Stations and backend CSMS (Charge Hub) to locally manage power consumption within the site installations.

  • LinkRay does this by reading, but not altering, the messages sent to the back office.

  • For each given charger you can apply limits of power.

  • The site installation limit will be shared across all chargers that are actively charging a vehicle, ensuring that everyone gets their fair share.

  • LinkRay can also act as a back-up load manager in case connections to the back office fail. In this instance, LinkRay will take over from the messages your back office would have provided to keep the chargers functioning.

  • The LinkRay connects to the Charge Hub FLEX DTM or onsite kWh meter (for simpler installations).

  • Can manage up to 32 x Stations (outlets).

Nationwide coverage, across Australia and New Zealand.

Based in Brisbane, Queensland, Australia.

AUS: 1300 98 67 67

NZ: 0800 608 138

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