# Distributed Generation and Renewable Energy Integration into the Grid: Prerequisites, Push Factors, Practical Options, Issues and Merits

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## Abstract

**:**

## 1. Introduction

#### Objectives and Methodology

## 2. The Concept of Distributed Generation (DG)

#### 2.1. Considerations of the Classification of DGs

#### 2.2. Push Factors in the Increasing Addition of DG in the Power System

#### 2.2.1. Environmentally Motivated Factors

#### 2.2.2. Economic Factors

#### 2.2.3. National/Regulatory Factors

#### 2.3. Grid Expansion through Distributed Renewables

#### 2.4. Location and Capacity of DG on a Power Network

## 3. Some Practical Options Used in DG to Grid Integration

#### 3.1. Vigorous Voltage Regulation at the Level of Substations

#### 3.2. Modified Grid Configuration

#### 3.3. The Use of the ‘N Minus Zero’ Regulation

#### 3.4. Reactive Power Control

#### 3.5. Creation of Express Feeders in the MV Network

^{2}) with the ability to transport large amounts of electricity to the consumers. The voltage drop on these lines is low due to the large cross-section, and, consequently, the reduced voltage drop can significantly increase the hosting capacity of the MV network [41]. This approach has proven to be economical in areas where voltage complications due to high renewable penetration are observed.

## 4. Issues Resulting from DG to Grid Integration

#### 4.1. Voltage Level Fluctuations

_{S}and Q

_{S}are the DG’s real and reactive power, and P

_{L}and Q

_{L}are the real and reactive power of the line load. R and X are the resistance and reactance of the line linking the DG to the substation. V is the line voltage at the point where the DG is connected. This scenario is illustrated in Figure 7 below.

#### 4.2. Effects on Power Line Losses

_{Loss}, over a complete cycle (T = 2π) is calculated as:

_{Loss}= average power loss in the line;

#### 4.3. Variability of Wind and Solar Resources

#### 4.4. Issues from an Economic Perspective

#### 4.5. Transient Voltage Changes

#### 4.6. Voltage Flickers

- $C\left({\phi}_{k},{v}_{a}\right)$ is the wind farm flicker coefficient obtained through a series of wind turbine tests;
- ${\phi}_{k}$ is the network impedance phase angle;
- ${v}_{a}$ is the annual average wind speed;
- ${S}_{n}$ is the wind farm rated power;
- ${S}_{k}^{\u2019\u2019}$ is the short-circuit power at the point of common coupling (PCC)

#### 4.7. Harmonics Distortion

#### 4.8. Grid Instability

#### 4.9. Increase in the Fault Level and Fragile Protection System

_{L}is the overhead transmission line current (A), R is the line resistance and ΔH is the heat transferred from the cable to the environment. When components are overloaded, there is a need for an upgrade of the equipment to a higher rating. Hence, when huge amounts of renewable energy are injected into the grid, the power system will need to be able to support this injected energy.

## 5. Review on Case Studies

#### 5.1. Case of South of England

#### 5.2. Case of Greece

#### 5.3. Case of Portugal

#### 5.4. Case of Pakistan

#### 5.5. Case of Maryland, USA

#### 5.6. Case Studies of DG Being Used to Resolve Grid Turbulence

#### 5.7. Review on Ideal Test Grid

#### 5.8. Lessons from Successful Countries Integrating Distributed Energy Sources

#### 5.8.1. Case of Italy

#### 5.8.2. Case of Germany

#### 5.8.3. Case of China

## 6. Merits of DG Integration into the Grid

#### 6.1. Peak Demand Curtailment

#### 6.2. Reduction of Power Losses in the Network

#### 6.3. Frequency Regulation

#### 6.4. Voltage Stabilization

#### 6.5. Less Risk of Terrorism

#### 6.6. Shelving of Network Upgrade

#### 6.7. Improved Reliability and Security of Supply in the Network

#### 6.8. Delivery of Ancillary Services

#### 6.9. Economic Viability of DG Projects

## 7. Discussion and Future Perspectives

## 8. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 2.**Classification of DG technologies [28].

**Figure 4.**Solar and wind electricity generation mix from the top 10 countries in 2018 [30].

**Figure 5.**Net annual additions in electricity production capacity of renewable and non-renewable sources between 2009 and 2019 [31].

**Figure 6.**Suggested allocation of voltage ranges [39].

**Figure 7.**Illustration of voltage profile of network before and after RE integration: (

**a**) Voltage profile at LV network with no distributed renewables; (

**b**) Voltage profile at LV network with distributed renewables.

**Figure 8.**Example of renewable energy power generation patterns [48].

**Figure 9.**Google map of substations with restrictions (red) and without restrictions (green) on the injection of renewable energy in Southampton, United Kingdom [60].

**Figure 10.**Voltage profile of the facility for 24 h. The green line shows the lowest voltages obtained, the large green dots indicate the voltage dips, the black line shows the medium voltages, and the red line represents the maximum voltages [62].

**Figure 11.**The voltage profile recorded in the second facility. The green shows the minimum voltages, the black shows the medium voltages, and the red signifies the maximum voltages [62].

**Figure 12.**Grid with overloaded transformers and lines in red [64].

**Figure 13.**Grid with injected PV System and replaced transformers and lines having no overloads [64].

**Figure 16.**Wind/solar electricity generation and curtailment in Italy [80].

**Figure 17.**Percentage curtailment of wind power in northeastern provinces of China within the first quarter of 2017 and 2018 [83].

Country/Institution | Capacity of DG | Location of DG | Mode of Operation |
---|---|---|---|

Sweden | ≤1500 kW | - | - |

New Zealand | <5 MW | - | - |

Australian Energy Market Operator | ≤30 MW | - | - |

International Council on Large Electricity Systems | <100 MW | Most often coupled to the distribution network | Not managed/dispatched centrally |

Bulgarian Energy Holding Company | <10 MW | Connected to the distribution network | Not managed centrally |

Electric Power Research Institute | ≤50 MW | Most often installed near load centers or distribution and medium-voltage (MV) substations | - |

Gas Research Institute | 25 kW ≤ X ≤ 25 MW | - | - |

England and Wales Electricity Markets | <100 MW | - | Not dispatched at a central point |

Estonian Power Markets | <50 MW | Connected to the distribution network | - |

Institute of Electrical and Electronics Engineering | ≤10 MW | Connected at any point within the power grid | - |

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**MDPI and ACS Style**

Iweh, C.D.; Gyamfi, S.; Tanyi, E.; Effah-Donyina, E.
Distributed Generation and Renewable Energy Integration into the Grid: Prerequisites, Push Factors, Practical Options, Issues and Merits. *Energies* **2021**, *14*, 5375.
https://doi.org/10.3390/en14175375

**AMA Style**

Iweh CD, Gyamfi S, Tanyi E, Effah-Donyina E.
Distributed Generation and Renewable Energy Integration into the Grid: Prerequisites, Push Factors, Practical Options, Issues and Merits. *Energies*. 2021; 14(17):5375.
https://doi.org/10.3390/en14175375

**Chicago/Turabian Style**

Iweh, Chu Donatus, Samuel Gyamfi, Emmanuel Tanyi, and Eric Effah-Donyina.
2021. "Distributed Generation and Renewable Energy Integration into the Grid: Prerequisites, Push Factors, Practical Options, Issues and Merits" *Energies* 14, no. 17: 5375.
https://doi.org/10.3390/en14175375