PHEV
Plug-In Hybrid Electric Vehicle
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Use
The plug-in hybrid electric vehicle (PHEV) simulates the charging/discharging processes of the vehicle's battery and the use of the vehicle while driving. When is the vehicle at the charging station and when is it driving around? What is the state of charge on arrival?
Reality: In reality, there is AC and DC charging. The main difference between AC and DC charging is where the alternating current (from the power grid) is converted into direct current (for charging the batteries). With AC charging, the conversion takes place in the vehicle itself. Electric vehicles have a built-in converter, a so-called on-board charger, which takes the alternating current and converts it into direct current via several converters. When charging at a DC charging point, the on-board charger can be bypassed because there is a current transformer in the charging station itself.
Simulation: For the simulation, it is assumed that the entire charging technology is located in the charging station and not in the vehicle. The on-board charger is part of the charging station model and therefore the vehicle is only charged with direct current.
Difference to BEV: The PHEV is initially powered by the energy of the battery, and when the battery is empty, it is powered by the energy of the combustion engine.
Parameters and Connectors
Connectors
The vehicle can be connected to different charging station models (ACChargingStation, DCChargingStation, GB_ChargingStation). ▶DC is the direct current connection between the vehicle and the charging station and the charging station controls the charging process of the vehicle via ▶ControlBus.
▶Present and ▶Drive have to be supplied to the vehicle model. If ▶Present is True, the vehicle is connected to the charging station. If ▶Present is False, ▶Drive has to be True because the vehicle is driving.
Note: You can easily define a presence or driving profile, for example depending on the HourOfDay and DayOfWeek by using the results of the environment model Environment.
Parameters
Battery
For more information see the battery parameters of the BEV - battery electric vehicle.
Vehicle dynamics and electricity demand
When a vehicle drives it can logically not be present at a charging station. The electricity demand of electric vehicles can thus be calculated independently of the modeled building energy system. For this, it is only necessary to determine which state of charge (electricity demand) the vehicle's battery has, once the electric vehicle returns to the charging station.
In this regard, it is necessary to model how much energy is needed to drive the vehicle, the desired distance. Here a quasi-static approach is applied. Due to the building energy system behavior and vehicle energy demand for driving being independent of each other, the drive-cycle specific average velocity and electrical power demand are included in the PHEV-model as constant parameters. It is thus assumed that the vehicle moves with a constant average velocity vCycleAverage and electrical power demand PBattCycleAverage. These two values could be calculated in more detail during pre-processing using dynamic simulation or quasi-static calculation approaches. This assumption also helps to reduce simulation time which is a main requirement in model development.
Applying such an approach, allows for the inclusion of detailed drive-cycle data for electrical power demand, into the simulation process without increasing model complexity and resultant simulation time. To ensure correct simulation the time-dependent characteristics for vehicle ▶Present ('true' when present) at charging station and ▶Drive ('true' when vehicle is driving) have to be supplied to the model.
To determine fuel and electricity demand for PHEV-driving a characteristic drive-cycle includes influences for hybrid-vehicle power train architecture, operation strategy, power train components and longitudinal dynamics:
PHEVs return to the charging station with an SOC between SOCMinEV and 100%. If the capacity of vehicle battery is too low to fulfill mobility demand (i.e. simulated driven distance is longer than the maximum range for electric driving), the PHEV returns to the charging station with an SOC of SOCMinEV. It is thus assumed that either additional electrical energy is provided by external charging stations which do not interact directly with the modeled building energy system or that the additional distance is driven in the charge sustain mode. The charge sustain mode enables the PHEV to only use the internal combustion engine once the battery reaches the SOCMinEV. Important to note is that the additionally required electric energy (i.e. external charging) cannot be considered within the presented simulation model.
Air conditioning and heating
Besides the power demand for driving, interior air conditioning and heating are two of the most important influences on overall energy consumptions of vehicles. To consider this the vehicle cabin is modeled as thermal one-zone-model. Concretely, heat losses and gains through the shell via heat transmission (UVehicle) and ventilation (LVehicle) dependent on the ambient temperature, are considered and simulated. According to the temperature difference between low TLow and high THigh comfort temperatures the heating or cooling load is calculated.
PHEVs energy demand for heating and cooling can be provided by the electric motor or internal combustion engine depending on operating strategy and internal system states.
In general, the parameter BatteryHeatCoolRatio (i.e. statistical factor for heating and cooling energy supply ratio of battery) must be set to a value close to one as almost all needed energy for heating and cooling (besides using heat losses from EM and ICE) is provided by the battery. In the case of the usage of heat pump systems, the system efficiency etaHeatCool can be set to values greater than 1 (usually between 1 and 4, modeling the COP, coefficient of performance of heat pump system). The factor can also be set to a lower value (less than 0.3) in cases where energy is mostly provided by heat losses of the ICE or internal air conditioning system. These auxiliary heating and cooling systems can result in higher fuel demand. Such effects are considered through the definition of the parameter AuxRatioHeatCool with a value greater than 0 (e.g. 0.1 - 10% of the heating and cooling energy demand is additionally provided by the ICE and cause a higher fuel demand). Note that the sum of both parameters (AuxRatioHeatCool and BatteryHeatCoolRatio) must not exceed the value 1.
All other parameters that are not explained should only be adjusted if measured values are available. If no measured values are available, retain the default values.