# SST-Based Grid Reinforcement for Electromobility Integration in Distribution Grids

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## Abstract

**:**

## 1. Introduction

## 2. Solid-State Transformer

#### 2.1. Topologies

#### 2.2. SST-Control

#### 2.3. Equivalent Steady-State Model

## 3. Simulation Methodology

- 1.
- Base case (BC) scenario: Base load profile with 0% EV penetration and without any voltage control;
- 2.
- Uncontrolled charging (UC) scenario: Grid operator does not control EV charging loads nor takes any control actions to prevent the violation of grid stability limits. EV users charge at their convenience;
- 3.
- Controlled charging(CC) scenario: EV users adhere to a charging schedule that is determined based on distribution grid constraints.

## 4. Results

#### 4.1. Medium-Voltage Distribution Grid

#### 4.1.1. Uncontrolled Charging Scenario

#### 4.1.2. Controlled Charging Scenario

#### 4.2. Low-Voltage Distribution Grid

## 5. Discussion

## 6. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## Abbreviations

AC | Alternating Current |

AFE | Active Frond-End |

BC | Base Case |

CC | Controlled Charging |

DAB | Dual-Active Bridge |

DC | Direct Current |

DSO | Distribution System Operator |

EU | European Union |

EV | Electric Vehicle |

EVCS | Electric Vehicle Charging Station |

IGBT | Insulated-Gate Bipolar Transistor |

LV | Low Voltage |

LVAC | Low Voltage Alternating Current |

MOSFET | Metal–Oxide–Semiconductor Field-Effect Transistor |

MVAC | Medium Voltage Alternating Current |

MV | Medium Voltage |

PLL | Phase-Locked-Loop |

RMS | Root Mean Square |

SST | Solid-State Transformer |

ToU | Time of Use |

THD | Total Harmonic Distortion |

UC | Uncontrolled Charging |

${P}_{set}$ | Active Power Set-point |

${Q}_{set}$ | Reactive Power Set-point |

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**Figure 1.**Exemplary grid topology with the SST used for grid reinforcement in addition to the distribution transformers.

**Figure 2.**Selected SST Topologies: (

**a**) Three-phase three-stage SST, (

**b**) Cascaded H-bridge based SST (only one phase is shown).

**Figure 4.**Simulation of the simplified SST inverter model with different realized active and reactive power set-points with ${G}_{\mathrm{tf}}$ being a low-pass filter with a corner frequency of 400 Hz, ${K}_{\mathrm{p}}=1.6$, ${K}_{\mathrm{i}}=0.1\times \frac{Kp}{{T}_{\mathrm{s}}}$ and ${T}_{\mathrm{s}}=100\phantom{\rule{3.33333pt}{0ex}}\mathsf{\mu}$s.

**Figure 5.**Modified CIGRE MV 14-node benchmark network. Reprinted with permission, from Ref. [36]. © 2006 IEEE.

**Figure 12.**Comparison of RMS node voltages for different EV penetration scenarios. Each color corresponds to a node in the grid.

**Figure 13.**Number of nodes with minimum RMS node voltage below threshold for different levels of reactive power injection.

Level of EV Penetration | Max. Loading of the Transformer TR1: Without SST | Max. Loading of the Transformer TR1: With SST | Max. Loading of the Transformer TR2: Without SST | Max. Loading of the Transformer TR2: With SST |
---|---|---|---|---|

30% | 102.25% | 92.10% | 83.53% | 93.64% |

50% | 108.05% | 97.83% | 88.07% | 98.24% |

80% | 116.86% | 106.53% | 94.94% | 105.19% |

Grid Parameters | 30% | 50% | 80% | |||
---|---|---|---|---|---|---|

Uncontrolled | Controlled | Uncontrolled | Controlled | Uncontrolled | Controlled | |

Maximum loading of transformer TR1 (%) | 102.25 | 87.60 | 108.05 | 89.00 | 116.86 | 91.00 |

Maximum loading of transformer TR2 (%) | 83.53 | 72.40 | 88.07 | 73.50 | 94.94 | 75.00 |

Grid Parameters | 40% EV Penetration without SST | 40% EV Penetration with SST | 50% EV Penetration without SST | 50% EV Penetration with SST |
---|---|---|---|---|

Maximum Transformer TR1 Loading (%) | 87.93 | 64.7 | 107.57 | 57.5 |

Maximum Transformer TR2 Loading (%) | 7.70 | 32.4 | 7.70 | 57.5 |

Number of nodes with Vmin* <= 0.9 p.u. RMS voltage | 88 | 85 | 116 | 115 |

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**MDPI and ACS Style**

Joglekar, C.; Mortimer, B.; Ponci, F.; Monti, A.; De Doncker, R.W.
SST-Based Grid Reinforcement for Electromobility Integration in Distribution Grids. *Energies* **2022**, *15*, 3202.
https://doi.org/10.3390/en15093202

**AMA Style**

Joglekar C, Mortimer B, Ponci F, Monti A, De Doncker RW.
SST-Based Grid Reinforcement for Electromobility Integration in Distribution Grids. *Energies*. 2022; 15(9):3202.
https://doi.org/10.3390/en15093202

**Chicago/Turabian Style**

Joglekar, Charukeshi, Benedict Mortimer, Ferdinanda Ponci, Antonello Monti, and Rik W. De Doncker.
2022. "SST-Based Grid Reinforcement for Electromobility Integration in Distribution Grids" *Energies* 15, no. 9: 3202.
https://doi.org/10.3390/en15093202