# Test and Modelling of Commercial V2G CHAdeMO Chargers to Assess the Suitability for Grid Services

^{*}

## Abstract

**:**

## 1. Introduction

## 2. The Need for Hardware Performance Assessment When Controlling EVs

- (i) Direction: The information if an EV can provide only uni-directional or bi-directional (V2G) power flow.
- (ii) Set-point linearity: The discreteness of the charging/discharging power set-point.
- (iii) Starting time and maximum activation time: The period between receiving the set-point and activating the flexibility.
- (iv-v) Ramp-up/ramp-down time: The up/downwards time between activation time and full service provision, and vice versa.
- (vi) Accuracy: The difference between the required and the delivered response, e.g., the acceptable response band.
- (vii) Precision: The variation of the delivered response for a given set-point.

## 3. Locally and Remotely Controlled EVs Performance Tests

#### 3.1. Outcome of Local Control Tests

#### 3.1.1. Calculation of Efficiency Map

_{ch}is defined as the ratio between the power flowing into the charger (AC power, P

_{AC}) and the power flowing out (DC power P

_{DC}). Similarly, the discharging efficiency η

_{dis}is defined as P

_{DC}/P

_{AC}. They are calculated as in Figure 4. Results are reported in Figure 4b, which shows that the large difference in the SOC has a negligible influence on the efficiency. The tests are performed only in the SOC range where the voltage changes linearly, so eventual difference in the results when operating in the extreme regions are not considered. However, it is not relevant considering the BMS limits in the usable range of the battery.

#### 3.1.2. Calculation of Activation Time

#### 3.2. Outcome of Remote Control Tests

#### 3.2.1. Calculation of Set-Point Linearity

#### 3.2.2. Calculation of Total Activation Time

#### 3.2.3. Calculation of Ramping Up/Down

#### 3.2.4. Calculation of Set-Point Accuracy

#### 3.2.5. Calculation of Set-Point Precision

## 4. Experimental Tests Discussion

## 5. Modelling of the Tested Hardware

_{SIM}, similarly to the real operation cases. The output signal is calculated by including appropriate actions that represent the charger’s real operation. In particular:

- the Activation time (iii) is modelled as a transport delay, equal to 4 s or 7 s in case of local or remote control, respectively;
- the Ramp-up/-down time (iv)–(v) is modelled with a rate limiter block, with the mean values 3.35 kW/s and 3.31 kW/s, respectively;
- the Set-point linearity (ii) is obtained by implementing Equation (1):$$out{}_{lin}=(linearity\ast in{}_{lin})\ast \mathbf{round}(in{}_{lin}/linearity),$$
_{lin}and out_{lin}are the non-rounded and the rounded power signals, respectively, whereas linearity is a constant parameter equal 400 W; - the Accuracy (vi) is implemented by adding to the power set-point the appropriate mean value of accuracy, i.e., 740 W, −440 W, and 420 W for negative set-point, positive set-point and zero set-point, respectively. The implementation is obtained according to Equation (2):$$ou{t}_{acc}=\left(\right)open="\{"\; close>\begin{array}{c}i{n}_{acc}+440W,\phantom{\rule{1.em}{0ex}}\phantom{\rule{1.em}{0ex}}if\phantom{\rule{1.em}{0ex}}i{n}_{acc}0\\ i{n}_{acc}+420W,\phantom{\rule{1.em}{0ex}}\phantom{\rule{1.em}{0ex}}if\phantom{\rule{1.em}{0ex}}i{n}_{acc}=0\\ i{n}_{acc}-740W,\phantom{\rule{1.em}{0ex}}\phantom{\rule{1.em}{0ex}}if\phantom{\rule{1.em}{0ex}}i{n}_{acc}0\end{array}$$
- the Precision (vii) is implemented by adding a uniformly distributed noise to the calculated set-point. On average, the noise has a an amplitude of 50 W and 6 W for set-point ≠ 0 and for zero set-point, respectively. The implementation is obtained according to Equation (3):$$ou{t}_{prec}=\left(\right)open="\{"\; close>\begin{array}{c}i{n}_{prec}+\mathbf{r}\ast (50/2W),\phantom{\rule{1.em}{0ex}}\phantom{\rule{1.em}{0ex}}if\phantom{\rule{1.em}{0ex}}i{n}_{prec}\ne 0\\ i{n}_{prec}+\mathbf{r}\ast (6/2W),\phantom{\rule{1.em}{0ex}}\phantom{\rule{1.em}{0ex}}if\phantom{\rule{1.em}{0ex}}i{n}_{prec}=0\end{array}$$
**r**is a random number uniformly distributed between −1 and +1 throughout the simulation.

## 6. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

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**Figure 3.**Active power test patterns: granular charging set-points modulation from 0 to −10 kW set-point with steps of 400 W utilized for the local control (

**a**), and one cycle of the remote control test pattern (

**b**).

**Figure 4.**V2G charger efficiency calculation (

**a**), and efficiency map for charging/discharging DC set-points from −10 kW to +10 kW with steps of 400 W (

**b**).

**Figure 5.**Analyses of the activation time for the local control test: time shift between the requested and the provided power (

**a**), and correlation between requested and provided power (

**b**). The correlation shows a maximum for a delay of 4 s, which can then be considered as the actual hardware response time.

**Figure 7.**Distribution of the observed granularities in terms of absolute and percentage observations. For the boxplots, the blue boxes indicate 50% of the observations, whereas the median is in red. Upper and lower quartiles (25% of the data) are located within the vertical black lines.

**Figure 8.**The correlation between requested and provided power for remote control shows a maximum for a delay of 7 s, which can then be considered the total activation time when the tested V2G equipment is controlled via the centralized remote control setup.

**Figure 9.**For each cycle of the performed performance assessment test, four events up and four events down are performed to calculate the ramping rate capability. For the step-wise portion, four cycles have been repeated.

**Figure 10.**For both accuracy and precision the calculation is done during the constant set-point levels of the step-wise portion of the tested cycles. This means at zero set-point at the maximum charging (−8.5 kW) and discharging power (+8.5 kW).

**Figure 13.**Analyses of the error between the simulated results and the real remote control test results: calculated error for 1 cycle in [kW] and in percentage with reference to the 10 kW size of the charger (

**a**), and statistical results for the entire test pattern (

**b**).

Cycle 1 | Cycle 2 | Cycle 3 | Cycle 4 | |
---|---|---|---|---|

up 1 | 8.84 kW in 3 s | 8.84 kW in 4 s | 8.82 kW in 3 s | 8.84 kW in 4 s |

up 2 | 9.03 kW in 4 s | 9.04 kW in 4 s | 9.03 kW in 4 s | 9.04 kW in 5 s |

up 3 | 17.87 kW in 6 s | 17.85 kW in 6 s | 17.88 kW in 4 s | 17.86 kW in 6 s |

up 4 | 8.84 kW in 4 s | 8.84 kW in 1 s | 8.83 kW in 4 s | 8.84 kW in 3 s |

Ramp-up AVG | 3.35 kW/s | |||

down 1 | 8.99 kW in 3 s | 8.79 kW in 4 s | 8.79 kW in 4 s | 8.99 kW in 3 s |

down 2 | 9.33 kW in 3 s | 9.16 kW in 1 s | 9.17 kW in 1 s | 9.16 kW in 4 s |

down 3 | 8.79 kW in 4 s | 8.98 kW in 3 s | 8.97 kW in 4 s | 8.99 kW in 4 s |

down 4 | 18.12 kW in 6 s | 18.14 kW in 7 s | 18.13 kW in 7 s | 18.14 kW in7 s |

Ramp-down AVG | 3.31 kW/s |

Attribute | Short Description | Unit | Target for Primary Reserve [14,26] | Test Result |
---|---|---|---|---|

(i) Direction | Support of bi- directional power flow | +/−/± | ± | ± i.e., V2G capable |

(ii) Set-point linearity | Supported set-point throughout the power range | [W] | Linear at 1% | <400 W (4%) (1 A @ 400V DC) |

(iii) Starting time and max. activation time | Time between set-point request and change in active power | [s] | <15 s | Local control: 4 s Remote control: 7 s |

(iv) Ramp-up time | Supported rate of change in power (increase) | [kW/s] | For the aggregate: 10–300 kW/s | AVG = 3.35 kW/s Max = 8.84 kW/s min = 1.81 kW/s |

(v) Ramp-down time | Supported rate of change in power (increase) | [kW/s] | For the aggregate: 10–300 kW/s | AVG = 3.31 kW/s Max = 9.17 kW/s min = 1.98 kW/s |

(vi) Accuracy | Difference between required and delivered response | [W] | ±5% of set-point & ±0.5% of rated pow. | Negative set-point: 740 W (+8.7% of set-point) (+7.4% of rated pow.) Positive set-point: −440 W (-5.2% of set-point) (−4.4% of rated pow.) 420 W @ zero set-point (4.2% of rated pow.) |

(vii) Precision | Variation of the delivered response | [W] | NA | ≈50 W (0.6% of set-point) (0.5% of rated pow.) 6 W @ zero set-point (0.06% of rated pow.) |

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**MDPI and ACS Style**

Zecchino, A.; Thingvad, A.; Andersen, P.B.; Marinelli, M.
Test and Modelling of Commercial V2G CHAdeMO Chargers to Assess the Suitability for Grid Services. *World Electr. Veh. J.* **2019**, *10*, 21.
https://doi.org/10.3390/wevj10020021

**AMA Style**

Zecchino A, Thingvad A, Andersen PB, Marinelli M.
Test and Modelling of Commercial V2G CHAdeMO Chargers to Assess the Suitability for Grid Services. *World Electric Vehicle Journal*. 2019; 10(2):21.
https://doi.org/10.3390/wevj10020021

**Chicago/Turabian Style**

Zecchino, Antonio, Andreas Thingvad, Peter Bach Andersen, and Mattia Marinelli.
2019. "Test and Modelling of Commercial V2G CHAdeMO Chargers to Assess the Suitability for Grid Services" *World Electric Vehicle Journal* 10, no. 2: 21.
https://doi.org/10.3390/wevj10020021