# Behaviour of Distribution Grids with the Highest PV Share Using the Volt/Var Control Chain Strategy

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Fundamentals of Volt/Var Control Chain Strategy

**s**econdary

**c**ontrol (VV

**SC**) schemas. The generalized form of volt/var control chain strategy [16] in the Y-axis of the holistic model “The energy supply chain net” that implies the L(U)+Q-autarky control ensemble [18] is shown in Figure 1. All relevant links are drawn in gold-coloured solid lines, while the neighbour grid-links are indicated by gold-dashed lines. Grid-links are set upon three classical levels: CP, LV and MV level. The automation and communication path is blue, while the power flow path is black.

**PC**s receive the set-points U* and Q* as in Table 1.

- (a)
- the voltage set-point for the primary control ${\mathrm{volt}\mathbf{PC}}_{\mathrm{OLTC}}^{\mathrm{MV}}$ of the supplying transformer and other transformers included in the MV_link-grid (e.g., 34.5 kV/11 kV, etc.) that have On-Load-Tap-Changer (OLTC);
- (b)
- the var set-points for the primary controls ${\mathrm{var}\mathbf{PC}}_{\mathrm{RD}}^{\mathrm{MV}}$ of all RDs included in the MV_link-grid;
- (c)
- the var set-points for the primary controls ${\mathrm{var}\mathbf{PC}}_{\mathrm{DG}/\mathrm{DSt}}^{\mathrm{MV}}$ of all DGs and Distributed Storages (DSt) connected to the MV_link-grid;
- (d)
- the var set-points for the Volt/var secondary controls ${\mathrm{VV}\mathbf{SC}}_{\mathrm{ngb}}^{\mathrm{MV},\mathrm{LV}}$ of all neighbour MV_ or LV_grid-links, while respecting the var constraint ${\mathrm{var}\mathbf{Cns}}_{\mathrm{MV}}^{\mathrm{HV}}$ at the border to the HV_link-grid.

- (a)
- the voltage and var set-points for the primary controls ${\mathrm{var}\mathbf{PC}}_{\mathrm{RD}}^{\mathrm{LV}}$ of all RDs included in the LV_link-grid;
- (b)
- the var set-points for the primary controls ${\mathrm{var}\mathbf{PC}}_{\mathrm{DG}/\mathrm{DSt}}^{\mathrm{LV}}$ of all DGs and DSts connected to the LV_link-grid;
- (c)
- the var set-points for the Volt/var secondary controls ${\mathrm{VV}\mathbf{SC}}_{\mathrm{ngb}}^{\mathrm{LV},\mathrm{CP}}$ of all neighbour LV_ or CP_grid-links, while respecting the var constraint ${\mathrm{var}\mathbf{Cns}}_{\mathrm{LV}}^{\mathrm{MV}}$ at the border to the MV_link-grid.
- (d)
- ${\mathrm{VV}\mathbf{SC}}^{\mathrm{CP}}$ calculates in real time
- (e)
- the var set-point for the primary control ${\mathrm{var}\mathbf{PC}}_{\mathrm{inv}}^{\mathrm{CP}}$ of the PV-inverter connected to CP_link-grid; while respecting the var constraint ${\mathrm{var}\mathbf{Cns}}_{\mathrm{CP}}^{\mathrm{LV}}$ at the border to the LV_link-grid.

#### 2.2. Model Description

#### 2.2.1. Customer Plant Model

#### 2.2.2. Distribution Grid Models

#### 2.3. Simulated Control Setups

**SC**is provided for the LV_grid-link, since only L(U) local controls (${\mathrm{var}\mathbf{LC}}_{\mathrm{L}\left(\mathrm{U}\right)}^{\mathrm{LV}})$ are connected at the end of some laterals: coordination is not relevant. The LV_grid-link is shown in gold-coloured dotted lines because its existence must be discussed also in terms of load-generation balancing. The latter is not within the scope of this paper. A grid-link is set up in the MV level. Here, the VV

**SC**is important to coordinate the Q-contribution of DGs, RDs and the neighbour grid-links with the voltage at the secondary side or OLTC position of the supplying transformer (STR) while respecting all constraints and optimizing the network performance at the same time.

## 3. Results and Discussion

#### 3.1. Behaviour of Distribution Grids

_{crit}are listed. Simulations are made for different control setups; results are drown in different colours as follows: “no control“ in dashed blackline; “no CDs” in purple; “${\mathrm{CD}}_{\mathrm{MV}}^{\mathrm{STR}}$” in green; “${\mathrm{CD}}_{\mathrm{MV}}^{\mathrm{DTR}}$” in ocra yellow and “${\mathrm{CD}}_{\mathrm{LV}}^{\mathrm{DTR}}$” in red solid line. The behaviour of distribution grids is analysed using various parameters as:

- (a)
- the total reactive power consumption of all L(U)s included in the LV_link-grids, ${Q}_{\mathit{tot}\mathbf{,}\mathit{t}}^{\mathit{L}\mathbf{\left(}\mathit{U}\mathbf{\right)}}$;
- (b)
- the total reactive power contribution of all CDs included in MV_ or LV_link-grids, ${\mathit{Q}}_{\mathit{tot}\mathbf{,}\mathit{t}}^{\mathit{CD}}$;
- (c)
- the reactive power exchange between HV_ and MV_link-grid, ${\mathit{Q}}_{\mathit{MV},\mathit{t}}^{\mathit{HV}}$, at the STR primary side;
- (d)
- the active power losses of the distribution grid, ${\mathit{P}}_{\mathit{t}}^{\mathit{loss}}$, including losses of transformers, cables and overhead lines;
- (e)
- the STR loading, ${\mathit{Loading}}_{t}^{\mathit{STR}}$;
- (f)
- the mean loading of all DTRs, ${\mathit{Loading}}_{t}^{\overline{\mathit{DTRs}}}$, which is calculated as in$${\mathit{Loading}}_{t}^{\overline{\mathit{DTRs}}}=\frac{{\sum}_{\mathrm{k}=1}^{32}{\mathit{Loading}}_{k,t}^{\mathit{DTR}}}{32}$$
- (g)
- the voltage limit violation index, ${\mathit{VI}}_{\mathit{t}}$, which is calculated as in$${\mathit{VI}}_{t}=\frac{{\sum}_{j=1}^{{m}_{t}}\left({U}_{u,t}^{\mathit{upper}}{-U}_{\mathit{lim}}^{\mathit{upper}}\right)}{{U}_{\mathit{nom}}^{\mathit{LV}}}+\frac{{\sum}_{j=1}^{{n}_{t}}\left({U}_{\mathit{lim}}^{\mathit{lower}}{-U}_{v,t}^{\mathit{lower}}\right)}{{U}_{\mathit{nom}}^{\mathit{LV}}}$$

#### 3.1.1. Distribution Grid with Cable Conductors in MV Level

_{crit}for all cases. The lowest value of 2.07 Mvar is achieved when no CDs are applied, while the highest one of 3.60 Mvar is reached when CDs are installed at the secondary sides of DTRs.

#### 3.1.2. Distribution Grid with Overhead Conductors in MV Level

_{crit}for all cases. The lowest value of 2.11 Mvar is achieved when no CDs are applied, while the highest one of 4.40 Mvar is reached when CDs are installed at the secondary sides of DTRs.

#### 3.1.3. Effect of CD Placement

#### 3.2. Discussion

- (a)
- MV_ and LV_link-grids have the same operator and as a result they do not have external interfaces between each other [16];
- (b)
- No reactive power is exchanged between LV_link-grids and CPs because of the Q-autarky of the latter;
- (c)
- No distributed energy resources are foreseen to deliver reactive power to the LV_link-grids;
- (d)
- At each LV feeder with voltage limit violation potential is installed one locally controlled L(U).

^{MV}that coordinates the Q-contribution of DGs, RDs and the neighbour grid-links with the voltage at the secondary side or OLTC position of the STR while respecting the reactive power constraints, ${\mathrm{var}\mathbf{Cns}}_{\mathrm{MV}}^{\mathrm{HV}}$, on the HV-MV intersection points and optimizing the network performance at the same time. The HV-MV intersection points correspond in many cases with TSO-DSO intersection points. ${\mathrm{var}\mathbf{Cns}}_{\mathrm{MV}}^{\mathrm{HV}}$ is dynamic and therefore needs to be discussed and defined through real-time TSO and DSO cooperation in order to achieve an optimal solution, in both, transmission and distribution grids.

**SC**

^{MV}is practically realized in real time in the frame of the industrial project Central Volt/var control in Presence of Distributed Generation (ZUQDE, Salzburg, Austria) [29,30]. The distribution state estimator was realized in a MV grid of European type with a symmetrical balanced behaviour. The ${\mathrm{VV}\mathbf{SC}}^{\mathrm{MV}}\left({\mathrm{volt}\mathbf{PC}}_{\mathrm{OLTC}}^{\mathrm{MV}}{,\text{}\mathrm{var}\mathbf{PC}}_{\mathrm{DG}}^{\mathrm{MV}},\text{}\mathrm{cos}\mathsf{\phi}{\mathbf{Cns}}_{\mathrm{MV}}^{\mathrm{HV}}\right)$ was successfully realized in closed loop. This project has indicated that the implementation of the proposed VVC chain strategy has great potential to be realized on an industrial scale.

## 4. Conclusions

**SC**

^{MV}, is industrially realized in real time in another project. Nevertheless, the industrial implementation of the entire VVC chain is the next step to prove the practical relevance of the results of this study.

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## Appendix A

**Figure A1.**Detailed one-line diagrams of the MV_link-grid models with different conductor types: (

**a**) cable; (

**b**) overhead line.

## Appendix B

## Appendix C

BLiN | Boundary link node | MV | Medium voltage |

BPN | Boundary producer node | OLTC | On load tap changer |

BSN | Boundary storage node | OpEx | Operational expenditures |

CapEx | Capital expenditures | PC | Primary control |

CD | Compensation device | PV | Photovoltaic |

CP | Customer plant | RD | Reactive device |

DG | Distributed generation | RPM | Reactive power margin |

DSO | Distribution system operator | SC | Secondary control |

DSt | Distributed storage | STR | Supplying transformer |

DTR | Distribution transformer | TSO | Transmission system operator |

HV | High voltage | VCRD | Voltage control reactive device |

ICT | Information and communications technology | VVC | Volt/var control |

LC | Local control | VVSC | Volt/var secondary control |

LV | Low voltage | ||

$\mathrm{cos}\mathsf{\phi}{\mathbf{Cns}}_{\mathrm{MV}}^{\mathrm{HV}}$ | $\mathrm{cos}\phi $ constraint at the border to the HV_link-grid | ${\mathrm{var}\mathbf{PC}}_{\mathrm{DG}/\mathrm{DSt}}^{\mathrm{LV}}$ | Primary controls of DGs and DSts connected to the LV_link-grids |

${\mathrm{var}\mathbf{Cns}}_{\mathrm{MV}}^{\mathrm{HV}}$ | Var constraint at the border to the HV_link-grid | ${\mathrm{var}\mathbf{PC}}_{\mathrm{RD}}^{\mathrm{LV}}$ | Primary controls of RDs included in the LV_link-grids |

${\mathrm{var}\mathbf{Cns}}_{\mathrm{LV}}^{\mathrm{MV}}$ | Var constraint at the border to the MV_link-grid | ${\mathrm{var}\mathbf{PC}}_{\mathrm{inv}}^{\mathrm{CP}}$ | Primary controls of PV-inverters connected to CP_link-grids |

${\mathrm{var}\mathbf{Cns}}_{\mathrm{CP}}^{\mathrm{LV}}$ | Var constraint at the border to the LV_link-grid | ${\mathrm{volt}\mathbf{PC}}_{\mathrm{OLTC}}^{\mathrm{MV}}$ | Primary controls of the STR or other transformers with OLTC included in the MV_link-grid |

${\mathrm{var}\mathbf{LC}}_{\mathrm{L}\left(\mathrm{U}\right)}^{\mathrm{LV}}$ | Local controls of L(U)s included in the LV_link-grids | ${\mathrm{VV}\mathbf{SC}}^{\mathrm{MV}}$ | VVSC of MV_grid-link |

${\mathrm{var}\mathbf{PC}}_{\mathrm{CD}}^{\mathrm{MV}}$ | Primary controls of CDs included in the MV_link-grid | ${\mathrm{VV}\mathbf{SC}}^{\mathrm{LV}}$ | VVSC of LV_grid-link |

${\mathrm{var}\mathbf{PC}}_{\mathrm{DG}/\mathrm{DSt}}^{\mathrm{MV}}$ | Primary controls of DGs and DSts connected to the MV_link-grid | ${\mathrm{VV}\mathbf{SC}}^{\mathrm{CP}}$ | VVSC of CP_grid-link |

${\mathrm{var}\mathbf{PC}}_{\mathrm{RD}}^{\mathrm{MV}}$ | Primary controls of RDs included in the MV_link-grid | ${\mathrm{VV}\mathbf{SC}}_{\mathrm{ngb}}^{\mathrm{MV},\mathrm{LV}}$ | VVSC of neighbour MV_ or LV_grid-links |

${\mathrm{var}\mathbf{PC}}_{\mathrm{CD}}^{\mathrm{LV}}$ | Primary controls of CDs included in the LV_link-grids | ${\mathrm{VV}\mathbf{SC}}_{\mathrm{ngb}}^{\mathrm{LV},\mathrm{CP}}$ | VVSC of neighbour LV_ or CP_grid-links |

${C}_{t}^{P,Z}$, ${C}_{t}^{P,I}$, ${C}_{t}^{P,P}$ | Active power ZIP coefficients for time-point t. |

${C}_{t}^{Q,Z}$, ${C}_{t}^{Q,I}$, ${C}_{t}^{Q,P}$ | Reactive power ZIP coefficients for time-point t. |

${E}_{\mathit{MV}}^{\mathit{HV}}$ | Active energy exchange between MV_ and HV_link-grid over the all-time horizon. |

${E}^{\mathit{loss}}$ | Active energy loss over the all-time horizon. |

${f}_{t}^{P,load}$ | Active power load profile factor at time-point t. |

${f}_{t}^{Q,load}$ | Reactive power load profile factor at time-point t. |

${f}_{t}^{P,PV}$ | Active power production profile factor at time-point t. |

${\mathit{Loading}}_{k,t}^{\mathit{DTR}}$ | Loading of the DTR k at time-point t. |

${\mathit{Loading}}_{t}^{\overline{\mathit{DTRs}}}$ | Mean loading of all DTRs at time-point t. |

${\mathit{Loading}}_{\mathit{avg}}^{\overline{\mathit{DTRs}}}$ | The average DTRs’ loading over the all-time horizon. |

${\mathit{Loading}}_{t}^{\mathit{STR}}$ | The STR loading at time-point t. |

${\mathit{Loading}}_{\mathit{avg}}^{\mathit{STR}}$ | The average STR loading over the all-time horizon. |

${m}_{t}$ | Number of LV_link-grid nodes that violate the upper voltage limit at time-point t. |

${n}_{t}$ | Number of LV_link-grid nodes that violate the lower voltage limit at time-point t. |

N | Number of conducted load-flow simulations per control setup and distribution grid model. |

${P}_{inv,i,t}^{CP}$ | Active power production of the PV-system of the CP i at time-point t. |

${P}_{load,i,t}^{CP}$ | Active power consumption of the loads of the CP i at time-point t. |

${P}_{PV,r}^{CP}$ | Module-rating of the PV-system of each CP. |

${P}_{CP,i,t}^{LV}$ | Active power flow from the CP i to LV_link-grid at time-point t. |

${P}_{nom,t}^{load}$ | Active power consumption of each CP’s load for nominal grid voltage at time-point t. |

${P}_{peak}^{load}$ | Peak active power demand of each CP’s load. |

${P}_{inv,t}^{MV}$ | Active power production of each PV-system connected to the MV_link-grid at time-point t. |

${P}_{PV,r}^{MV}$ | Module-rating of each PV-system connected to the MV_link-grid. |

${P}_{t}^{\mathit{loss}}$ | Active power losses of the distribution grid at time-point t. |

${P}_{\mathit{MV},t}^{\mathit{HV}}$ | Active power flow from the MV_ to HV_link-grid at time-point t. |

${Q}_{inv,i,t}^{CP}$ | Reactive power production of the PV-system of the CP i at time-point t. |

${Q}_{load,i,t}^{CP}$ | Reactive power consumption of the loads of the CP i at time-point t. |

${Q}_{CP,i,t}^{LV}$ | Reactive power flow from the CP i to LV_link-grid at time-point t. |

${Q}_{nom,t}^{load}$ | Reactive power consumption of each CP’s load for nominal grid voltage at time-point t. |

${Q}_{tot,t}^{L\left(U\right)}$ | Total reactive power consumption of all L(U)s included in the LV_link-grids at time-point t. |

${Q}_{tot,t}^{CD}$ | Total reactive power contribution of all CDs included in MV_ or LV_link-grids at time-point t. |

${Q}_{MV,t}^{HV}$ | Reactive power flow from the MV_ to HV_link-grid at time-point t. |

${S}_{inv,r}^{CP}$ | Inverter-rating of the PV-system of each CP. |

${S}_{inv,r}^{MV}$ | Inverter-rating of each PV-system connected to the MV_link-grid. |

${U}_{i,t}$ | Actual voltage at the BLiN of the CP i at time-point t. |

${U}_{nom}^{LV}$ | Nominal voltage of LV_link-grids. |

${U}_{u,t}^{\mathit{upper}}$ | Voltage of the LV_link-grid node u with upper voltage limit violation at time-point t. |

${U}_{v,t}^{\mathit{lower}}$ | Voltage of the LV_link-grid node v with lower voltage limit violation at time-point t. |

${U}_{\mathit{lim}}^{\mathit{upper}}$ | Upper voltage limit. |

${U}_{\mathit{lim}}^{\mathit{lower}}$ | Lower voltage limit. |

${\mathit{VI}}_{t}$ | Voltage limit violation index at time-point t. |

${\mathit{VI}}_{\mathit{avg}}$ | Average voltage limit violation index over the all-time horizon. |

${t}_{\mathit{crit}}$ | Critical time-point, where the maximal PV production occurs. |

$\Delta t$ | Time-step used to sample the load and production profiles. |

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**Figure 1.**The generalized form of the volt/var control chain strategy implying the L(U)+Q-autarky control ensemble.

**Figure 4.**Simplified one-line diagrams of the MV_link-grid models with different conductor types: (

**a**) cable; (

**b**) overhead line.

**Figure 6.**Simplified form of the VVC chain strategy representing the setup with L(U)-control and CP_Q-autarky.

**Figure 7.**Simplified form of the VVC chain strategy representing the setup with L(U)-control, CP_Q-autarky and a CD at the STR MV-busbar.

**Figure 8.**Simplified form of the VVC chain strategy representing the setup with L(U)-control, CP_Q-autarky and CDs at the DTRs’ MV-busbars.

**Figure 9.**Simplified form of the VVC chain strategy representing the setup with L(U)-control, CP_Q-autarky and CDs at the DTRs’ LV-busbars.

**Figure 10.**Voltage profile of the MV_link-grid with cable conductors and the backmost LV_link-grid at ${t=t}_{\mathit{crit}}.$

**Figure 11.**Behaviour of the distribution grid with cable conductors in MV level for a 24 h time horizon and different control strategies: (

**a**) Q-consumption of L(U)s; (

**b**) Q-contribution of CDs; (

**c**) Q-exchange between HV_ and MV_link-grid; (

**d**) active power losses; (

**e**) STR loading; (

**f**) mean DTR loading.

**Figure 12.**Voltage profile of the MV_link-grid with overhead line conductors and the backmost LV_link-grid at ${t=t}_{\mathit{crit}}$.

**Figure 13.**Behaviour of the distribution grid with overhead line conductors in MV level for a 24 h time horizon and different control strategies: (

**a**) Q-consumption of L(U)s; (

**b**) Q-contribution of CDs; (

**c**) Q-exchange between HV_ and MV_link-grid; (

**d**) active power losses; (

**e**) STR loading; (

**f**) mean DTR loading.

**Figure 14.**Active energy exchange between MV_and HV_link-grid for different conductor types in MV level: (

**a**) cable; (

**b**) overhead line.

**Figure 15.**Qualitative representation of the criteria used for the evaluation of various CD placements on a distribution grid with different conductor types in MV level: (

**a**) cable; (

**b**) overhead line.

**Figure 16.**The most suitable setup of the VVC chain for a distribution grid with the highest PV share operated by one DSO.

Device | Purpose | Set-Point for varPC | |
---|---|---|---|

RD | VCRD | Voltage control | U* |

CD | Var compensation | Q* |

**Table 2.**Behaviour of the distribution grid with cable conductors in MV level at ${t}_{\mathit{crit}}$ for different control setups.

Control Setup | ${\mathit{Q}}_{\mathit{t}\mathit{o}\mathit{t},{\mathit{t}}_{\mathit{c}\mathit{r}\mathit{i}\mathit{t}}}^{\mathit{L}\left(\mathit{U}\right)}$ (Mvar) | ${\mathit{Q}}_{\mathit{t}\mathit{o}\mathit{t},{\mathit{t}}_{\mathit{c}\mathit{r}\mathit{i}\mathit{t}}}^{\mathit{C}\mathit{D}}$ (Mvar) | ${\mathit{Q}}_{\mathit{M}\mathit{V},{\mathit{t}}_{\mathit{c}\mathit{r}\mathit{i}\mathit{t}}}^{\mathit{H}\mathit{V}}$ (Mvar) | ${\mathit{P}}_{{\mathit{t}}_{\mathit{c}\mathit{r}\mathit{i}\mathit{t}}}^{\mathit{l}\mathit{o}\mathit{s}\mathit{s}}$ (MW) | $\mathit{L}\mathit{o}\mathit{a}\mathit{d}\mathit{i}\mathit{n}{\mathit{g}}_{{\mathit{t}}_{\mathit{c}\mathit{r}\mathit{i}\mathit{t}}}^{\mathit{S}\mathit{T}\mathit{R}}$ (%) | $\mathit{L}\mathit{o}\mathit{a}\mathit{d}\mathit{i}\mathit{n}{\mathit{g}}_{{\mathit{t}}_{\mathit{c}\mathit{r}\mathit{i}\mathit{t}}}^{\overline{\mathit{D}\mathit{T}\mathit{R}\mathit{s}}}$ (%) |
---|---|---|---|---|---|---|

No control | 0.00 | 0.00 | −0.70 | 0.94 | 52.44 | 64.40 |

No CDs | 2.07 | 0.00 | −2.65 | 1.17 | 53.28 | 67.47 |

${\mathbf{CD}}_{\mathbf{MV}}^{\mathbf{STR}}$ | 2.63 | −3.17 | 0.00 | 1.23 | 50.95 | 67.74 |

${\mathbf{CD}}_{\mathbf{MV}}^{\mathbf{DTR}}$ | 3.03 | −3.67 | 0.11 | 1.25 | 50.81 | 68.11 |

${\mathbf{CD}}_{\mathbf{LV}}^{\mathbf{DTR}}$ | 3.60 | −4.24 | 0.11 | 1.33 | 50.35 | 60.74 |

**Table 3.**Behaviour of the distribution grid with overhead conductors in MV level at ${t}_{\mathit{crit}}$ for different control setups.

Control Setup | ${\mathit{Q}}_{\mathit{t}\mathit{o}\mathit{t},{\mathit{t}}_{\mathit{c}\mathit{r}\mathit{i}\mathit{t}}}^{\mathbf{L}\left(\mathbf{U}\right)}$ (Mvar) | ${\mathit{Q}}_{\mathit{t}\mathit{o}\mathit{t},{\mathit{t}}_{\mathit{c}\mathit{r}\mathit{i}\mathit{t}}}^{\mathit{C}\mathit{D}}$ (Mvar) | ${\mathit{Q}}_{\mathit{M}\mathit{V},{\mathit{t}}_{\mathit{c}\mathit{r}\mathit{i}\mathit{t}}}^{\mathit{H}\mathit{V}}$ (Mvar) | ${\mathit{P}}_{{\mathit{t}}_{\mathit{c}\mathit{r}\mathit{i}\mathit{t}}}^{\mathit{l}\mathit{o}\mathit{s}\mathit{s}}$ (MW) | $\mathit{L}\mathit{o}\mathit{a}\mathit{d}\mathit{i}\mathit{n}{\mathit{g}}_{{\mathit{t}}_{\mathit{c}\mathit{r}\mathit{i}\mathit{t}}}^{\mathit{S}\mathit{T}\mathit{R}}$ (%) | $\mathit{L}\mathit{o}\mathit{a}\mathit{d}\mathit{i}\mathit{n}{\mathit{g}}_{{\mathit{t}}_{\mathit{c}\mathit{r}\mathit{i}\mathit{t}}}^{\overline{\mathit{D}\mathit{T}\mathit{R}\mathit{s}}}$ (%) |
---|---|---|---|---|---|---|

No control | 0.00 | 0.00 | −1.97 | 1.22 | 51.85 | 63.53 |

No CDs | 2.11 | 0.00 | −4.04 | 1.52 | 54.03 | 67.61 |

${\mathbf{CD}}_{\mathbf{MV}}^{\mathbf{STR}}$ | 2.79 | −4.66 | 0.00 | 1.60 | 48.93 | 67.90 |

${\mathbf{CD}}_{\mathbf{MV}}^{\mathbf{DTR}}$ | 3.80 | −4.52 | −1.08 | 1.63 | 49.04 | 69.42 |

${\mathbf{CD}}_{\mathbf{LV}}^{\mathbf{DTR}}$ | 4.40 | −5.11 | −1.06 | 1.72 | 48.50 | 58.49 |

**Table 4.**Criteria used for the evaluation of different CD locations within the distribution grid with cable or overhead conductors in MV level.

Conductor Type in MV Level | Control Setup | ${\mathit{VI}}_{\mathit{avg}}$ (-) | ${\mathit{E}}^{\mathit{loss}}$ (MWh) | ${\mathit{E}}_{\mathit{MV}}^{\mathit{HV}}$ (MWh) | ${\mathit{Loading}}_{\mathit{avg}}^{\mathit{STR}}$ (%) | ${\mathit{Loading}}_{\mathit{avg}}^{\overline{\mathit{DTRs}}}$ (%) | No. of CDs (-) |
---|---|---|---|---|---|---|---|

Cable | ${\mathbf{CD}}_{\mathbf{MV}}^{\mathbf{STR}}$ | 0.0000 | 6.5051 | 34.4286 | 17.9049 | 23.9071 | 1 |

${\mathbf{CD}}_{\mathbf{MV}}^{\mathbf{DTR}}$ | 0.0000 | 6.6000 | 34.0946 | 18.5570 | 23.9116 | 32 | |

${\mathbf{CD}}_{\mathbf{LV}}^{\mathbf{DTR}}$ | 0.0016 | 7.2863 | 33.8003 | 19.0885 | 23.5122 | 32 | |

Overhead | ${\mathbf{CD}}_{\mathbf{MV}}^{\mathbf{STR}}$ | 0.0000 | 8.3320 | 32.5502 | 17.4605 | 23.9019 | 1 |

${\mathbf{CD}}_{\mathbf{MV}}^{\mathbf{DTR}}$ | 0.1484 | 8.4739 | 32.3078 | 17.4682 | 24.1743 | 32 | |

${\mathbf{CD}}_{\mathbf{LV}}^{\mathbf{DTR}}$ | 0.8307 | 8.8536 | 31.9763 | 17.3888 | 22.3732 | 32 |

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Schultis, D.-L.; Ilo, A. Behaviour of Distribution Grids with the Highest PV Share Using the Volt/Var Control Chain Strategy. *Energies* **2019**, *12*, 3865.
https://doi.org/10.3390/en12203865

**AMA Style**

Schultis D-L, Ilo A. Behaviour of Distribution Grids with the Highest PV Share Using the Volt/Var Control Chain Strategy. *Energies*. 2019; 12(20):3865.
https://doi.org/10.3390/en12203865

**Chicago/Turabian Style**

Schultis, Daniel-Leon, and Albana Ilo. 2019. "Behaviour of Distribution Grids with the Highest PV Share Using the Volt/Var Control Chain Strategy" *Energies* 12, no. 20: 3865.
https://doi.org/10.3390/en12203865