Voltage stability depends on the grid’s ability to maintain constant voltage across all nodes. Voltage variations, caused by reactive power imbalances, can lead to local or global instabilities. Solar and wind plants play a crucial role in reactive power management through modern compensation devices. This means that voltage is an important parameter in an electric power system that indicates an imbalance of reactive power in a specific area [12] as depicted below in Figure 2 . If we consider the conductors used for power transmission as a resistor in series with an inductance

The voltage drop can be expressed as Equation (1):

$\Delta V=V_s-V_g=\frac{R_L\cdot P+X_L\cdot Q}{V_g}$ (1)

P and Q are respectively active and reactive power.

For a power transport system, $X_L\gg R_L$ then Equation (1) becomes Equation (2):

$\Delta V=\frac{{\text{X}}_L\cdot Q}{{\text{V}}_g}$ (2)

Voltage variation is directly dependent on reactive power; it is an important parameter in an electric power system that indicates an imbalance of reactive power in a specific area. Therefore, there are local voltage stability problems (of each zone) and global voltage stability problems, caused by small or large disturbances [13] - [15] .

Voltage stability can be further divided into two categories:

We can see in Table 1 below some selected power outages in the world [21] .

Photovoltaic (PV) systems do not directly generate reactive power, but their inverters can be configured to supply or absorb it using capacitors/coils, stabilizing grid voltage. Senelec enforces a minimum power factor of 0.89 at injection points, requiring compensation devices to balance fluctuations. Wind turbines, equipped with in phases (2017-2019), regulate reactive power via a supervisory system based on Dispatching setpoints. Without external commands, it maintains 225 kV with a 4% static voltage drop, automatically adjusting turbine reactive power references and compensation equipment. Power Factor Control (PFC) and Voltage Control (VC) modes enable dynamic management, demonstrating how renewables enhance grid stability and efficiency despite intermittency.

Figure 3 defines the limits of the reactive capacities of Taiba Ndiaye Wind Park (PETN).

The startup speed of the wind turbines at the PETN power plant is 3 m/s, and the cut-out speed is 21 m/s. The maximum speed reached so far is 17 m/s. It is mainly during the rainy season that wind gusts are noted, often occurring with thunderstorms. These gusts are dangerous phenomena for the stability of the electrical system and require good anticipation in system operation. The effect of the gusts is primarily seen through rapid power surges, leading to over frequencies and overvoltage on the interconnected network.

Conversely, a sharp drop in wind turbine production leads to a decrease in frequency and voltage and sometimes results in manual or automatic load shedding.

Voltage fluctuations (voltage drops and phase imbalances) in the SENELEC network cause disturbances to solar power plants. When variations exceed +/− 10%, the solar plants island themselves. These fluctuations are due to the tripping of feeders connected to the busbar at the connection substation.

The absorption and provision of reactive power are carried out by wind turbines. Reactors and capacitors only intervene when the adjustment capacities of the wind turbines are exceeded.

Grid operators use active power reserves to keep the frequency stable (generally around 50 Hz in Senegal). These reserves are rapidly mobilized to compensate for imbalances and return the frequency to its nominal value.

Grid frequency (50 Hz in Senegal) reflects the balance between production and consumption. Renewable energies, being intermittent, increasing frequency variability, requiring active power reserves and advanced forecasting tools to maintain stability.

The variation in active power in an electricity network and the variation in frequency over time are linked by Equation (3) below [12] :

$\Delta P=\left(\frac{2H}{f_0}\right)\frac{df}{dt}$ (3)

$\Delta P$ being the active power difference in the power system, measured in watts (W).

$H$ (Inertia constant): a measure of the inertia of the electrical system, expressed in seconds (s). It represents the system’s ability to resist changes in frequency.

$f_0$ being the standard frequency of the electrical network, generally 50 Hz or 60 Hz, depending on the region.

$df/dt$ is the derivative of frequency with respect to time, indicating how quickly the frequency changes, measured in hertz per second (Hz/s).

Frequency stability can be classified in two forms:

This deals with frequency variations over longer periods, often caused by persistent imbalances between supply and demand.

Renewable energy sources are intermittent and variable, with production corresponding to natural flows, which are not permanently available and whose availability varies widely without any possibility of control.

Senelec interconnected network uses PV plants and wind energy, which are intermittent and variable.

$Hourlysolarpower=P_{nom}\cdot \frac{I}{I_{STC}}\cdot \left\{\left(100\%\left(T-25\right)\cdot T_P\right)\right\}\cdot PR$ (4)

with:

$P_{nom}$ is the installed peak power and I_STC is the STC irradiance (standard conditions) = 1 kWh/m².

$T$ is the panel temperature, PR is the system performance ratio, which takes losses into account (typically between 0.7 and 0.8).

$T_P$ is the rate of losses induced if the actual panel temperature is different from the standard conditions (STC). The rate of power loss varies from −0.41% to −0.75% per degree Celsius for the different types of panels in the power plant.

The formula above shows that energy production depends considerably on the irradiation and temperature of the panels.

$P=\frac{1}{2}\cdot \rho \cdot S\cdot V^3\cdot C_p$ (5)

where:

$P$ is the power in watts (W),

$\rho$ is the density of the air in kilograms per cubic meter (kg/m³),

$S$ is the area swept by the turbine blades in square meters (m²),

$V$ is the wind speed in meters per second (m/s),

$C_p$ is the power coefficient of the wind turbine, which represents the efficiency of converting the wind’s kinetic energy into mechanical energy.

To ensure the stability of a grid, a good forecast of wind turbine production is essential. In general, an acceptable error rate for wind production forecasts is around 10% to 20%. The rate depends on the quality of the meteorological data, the technology used for the forecasts, and the specific characteristics of the wind farm site.

Reduced production costs:

In 2023, the variable cost of a kilowatt-hour (kWh) for the Inter Connected Network (ICN) was 83.18 F/kWh, and for the Non-Interconnected Network (NIN) it was 134.34 F/kWh. The contractual cost with renewable energy plants was around 65 F/kWh.

Incentives and subsidies:

These points show how the integration of renewable energy can not only reduce production costs, but also bring significant long-term economic benefits.

There are many effects related to the environment:

Carbon credits serve as a cornerstone of market-based mechanisms designed to reduce greenhouse gas (GHG) emissions. Each credit represents the equivalent of one tonne of CO₂ either avoided or sequestered through projects that replace fossil fuels with clean energy solutions (e.g., solar power plants). These credits operate within international frameworks such as the Kyoto Protocol or the Paris Agreement and are traded on two distinct markets:

The integration of renewable energy can have significant positive environmental effects, contributing to a more sustainable and healthier future.

The integration of renewable energy into power grids has been widely studied, but practical experiences in developing regions like West Africa remain limited. Key findings from existing literature include:

These renewable energies are sustainable, clean and do not generate greenhouse gases; moreover, their development can lead to a reduction in the overall cost of energy. By associating these renewable energies with new energy policies, it has become possible to inject the production of these renewable sources into the conventional electricity grid. This is known as integrating renewable energies into the electricity grid. This integration of renewable energies makes it possible to make up for production shortfalls in a number of countries, especially in Africa and Asia, and therefore makes a major contribution to the availability of electrical energy. Many countries are faced with electricity shortages. In Senegal, the national electricity company Senelec was unable to supply its customers because of a lack of production until 2017. But since 2017, Senegal, through its national electricity company Senelec, has been purchasing electricity produced by private company as: solar photovoltaic energy for around 344 GWh in 2023) and wind energy for around 382 GWh in 2023 [5] .

This integration presents technical and operational challenges [6] - [10] but also offers opportunities to improve the resilience and sustainability of electricity systems. This paper aims to explore feedback from the integration of renewable energies into the interconnected grid of Senegal in particular and the interconnected grid of West Africa in general. By analyzing specific case studies, we will highlight the successes, challenges encountered, and innovative solutions implemented. The aim is to provide valuable insights for engineers, researchers engaged in the transformation of energy infrastructures and policy makers.

This section highlights the gaps in literature, particularly the lack of detailed case studies from West Africa and positions this paper as a contribution to filling those gaps.

To assess economic impacts, we examined historical data from renewable energy plants by calculating the total cost per kWh (total incurred cost divided by energy produced). This same methodology was applied to conventional energy sources, where total costs (variable, fixed, and fuel-related) were divided by the energy generated. This comparative approach enabled us to determine precise production costs for each energy technology.

It is important to note that, when scaling production units to meet demand, operational decisions prioritize variable energy costs, as fixed costs for power plants are assumed to be systematically covered. This explains why some conventional units (with low variable costs) may appear more cost-competitive than renewables under standard operating conditions. However, our analysis focuses on the full production cost per kWh (incorporating all expenses) to reflect the comprehensive economic reality of each technology.

To assess voltage stability, we examined historical data from interconnection points before and after the introduction of intermittent energy sources. This analysis enabled us to observe the evolution of voltage stability over time.

The methodology ensures a comprehensive understanding of the impacts of renewable energy integration, providing actionable insights for policymakers and engineers

The quantification of emissions avoided by renewable energy relies on a comparative analysis with the local energy mix. The key steps are as follows:

Electricity production by source: Coal, gas, solar, etc., expressed in MWh or GWh.

Emission factors (EF) by technology: CO₂ emissions per kWh for each energy source (e.g., 0.95 kg CO₂/kWh for coal).

1) Emissions per source:

$Emissions\left(kg{\text{CO}}_{\text{2}}\right)=\mathrm{Pr}oduction\left(kWh\right)\times EF\left(kg{\text{CO}}_2/kWh\right)$ (6)

2) Total grid emissions:

$TotalEmissions={\displaystyle \underset{i}{\sum }\left(Emissionsfromsourcei\right)}$ (7)

3) Average grid emission factor

$AverageEF\left(kg\text{CO}/kWh\right)=\frac{TotalEmissions\left(kg{\text{CO}}_{\text{2}}\right)}{TotalEnergy\mathrm{Pr}oduction\left(kWh\right)}$ (8)

Renewable energy avoids emissions equivalent to those that would have been produced by the local energy mix. Thus:

$Credits\left(tonnes{\text{CO}}_2\right)=AverageEF\left(tonnes{\text{CO}}_2/MWh\right)\times \mathrm{Re}newableEnergy\mathrm{Pr}oduction\left(MWh\right)$(9)

To quantify CO₂ emissions avoided by renewable energy sources (solar, wind, hydro) in Senegal and assess carbon credit valorization, the methodology comprised three key steps. First, annual production data from renewable power plants within the SENELEC grid network and local emission factors (EFs) from fossil fuel-based generation were collected. Second, the grid’s average emission factor (EF) was calculated and benchmarked against international frameworks—including ADEME’s Base Carbone® (France-specific carbon database), IPCC guidelines (for national GHG inventories), and Bilan Carbone® (corporate carbon accounting)—to contextualize its carbon intensity relative to global standards. Finally, avoided emissions were determined by multiplying renewable energy production (MWh) by the average grid EF (tCO₂/MWh), with results disaggregated by energy source and year.

Significant voltage variations were observed before and after the integration of renewable energy sources. These fluctuations primarily occur at the injection points of solar and wind power plants, characterized by overvoltage peaks during periods of maximum production and voltage drops during intermittencies.

Production from solar and wind power plants has been consumed locally and has helped to mitigate the overvoltage observed since 2014.

Figure 5 shows the positive impact with the improvement of the voltage plane. The Taiba wind power plant, with its capacity to absorb and inject reactive power into the grid, has made it possible to maintain the voltage on this Tobène node at +/− 5% ranges of 225 KV.

The average monthly voltage at DAGANA has fluctuated over the years, peaking in 2016 (229.22 KV) and showing a notable decrease in 2019 (222.82 KV).

The voltage variations can be attributed to the integration of renewable energies and the management of the load on the network.

Strengthen reactive power regulation to mitigate instability and leverage its reactive power supply potential.

The average monthly voltage at SAKAL has remained relatively stable, with slight increases in 2015 and 2016, followed by stability around 225 KV.

The average monthly voltage at TOBENE showed an upward trend until 2017, followed by a slight decrease and stabilization around 228 KV.

The integration of renewable energy has significantly impacted voltage stability in Senegal’s grid:

PETN compensation is essential for maintaining stability [18] .

Proposed Solutions are:

a) Enhance reactive power regulation using synchronous compensators or battery storage systems.

b) Optimize plant locations to minimize grid imbalances.

The increase in renewable energy production has contributed to frequency variability, requiring adjustments to maintain network stability. Renewable integration has led to more frequent frequency deviations, particularly outside the optimal range of 49.8 Hz < F < 50.2 Hz.

Figure 6 below shows the variation in presence time from 2016 to 2024.

Frequency management has become more complex with the increase in the penetration of renewable energies. Frequency fluctuations have increased, requiring additional efforts to stabilize the network.

The years 2020 to 2022 were particularly challenging, with optimal presence times below 40%, indicating significant challenges in frequency management.

Figure 7 shows that the presence rate decreases significantly when the penetration rate exceeds 6%.

Optimal frequency presence time dropped to 26.27% in 2022 but recovered to 84.25% in 2024 due to improved grid management.

Time within optimal range: Decreased from 98% (conventional system) to 89% (with 30% renewable penetration).

Direct correlation between renewable energy share and frequency instability.

Impact of Renewable Energy

The lack of inherent inertia in solar and wind systems complicates rapid frequency regulation, especially during abrupt load changes.

Proposed Solutions

a) Deploy energy storage systems (batteries, flywheels…).

b) Integrate advanced weather forecasting tools to anticipate production variations.

The integration of renewable energies into the electrical grid has shown a positive trend in terms of reducing costs compared to conventional energies. From 2016 to 2024, the costs of renewable energies (hydro, solar, wind) remained relatively stable, averaging 52.02 FCFA/KWH. In contrast, the costs of conventional energies fluctuated significantly, averaging 98.12 FCFA/KWH. This cost difference indicates that renewable energies are not only more economical but also more predictable in terms of costs.

This trend suggests that increased integration of renewable energies could continue to offer substantial economic benefits while contributing to the stability and sustainability of the energy grid as depicted in Table 2 .

Analyzing the data year by year, we observe that the gap between the costs of renewable and conventional energies has widened, particularly in 2022 and 2023, where the costs of conventional energies reached peaks of 135.74 and 121.82 FCFA/kWh respectively. In 2023, the cost of renewable energy per kWh was 65 F/kWh, significantly lower than the variable costs of the interconnected grid (83.18 F/kWh) and non-interconnected grid (134.34 F/kWh). Government subsidies, monetizable carbon credits, and local job creation further stimulate economic growth, while regional development initiatives, particularly in rural areas, attract investment and opportunities.

Economic Benefits

Government subsidies (covering 30% of investment costs) and carbon credits (10,000 F CFA/tonne of avoided CO₂) enhance project profitability.

Senegal’s renewable energy integration has achieved significant milestones, including a 40% reduction in CO₂ emissions (5.3 million tonnes avoided since 2002) and a strengthened grid capacity, with installed power rising from 855 MW (2011) to 1789 MW (2023). Renewables now constitute 28% of the energy mix, driven by solar, wind, and hydropower. While these advances bolster environmental sustainability and energy security, challenges persist in grid stability, particularly voltage fluctuations and frequency deviations during high renewable penetration (>6%). Proactive measures-such as deploying smart grid technologies (SCADA systems), fixed reactances, and energy storage-have improved reactive power management and real-time grid control. However, intermittent generation and infrastructure limitations underscore the need for continued innovation and adaptive planning to align with global decarbonization goals.

Senegal’s progress positions it as a regional leader in climate-resilient energy transitions. By addressing technical gaps through innovation, policy coherence, and strategic investments, the nation can achieve its 2035 renewable targets while advancing socio-economic development. This roadmap offers actionable insights for policymakers, engineers, and stakeholders to harmonize sustainability with grid reliability, ensuring a just and efficient energy transition.

While this analysis provides critical insights into renewable energy integration, certain methodological constraints must be acknowledged to contextualize the findings. Notably, the study relies on aggregated data due to confidentiality agreements with independent power producers, limiting granularity, and excludes real-time dynamic modeling, which may affect the precision of grid behavior simulations under transient conditions.

1) Grid Modernization & Technology

2) Policy & Investment

3) Regional Collaboration

4) Capacity Building

5) Research & Innovation

This paper not only provides a scientific analysis of renewable energy integration but also serves as a practical guide for future leaders. By learning from Senegal’s experience, other regions can accelerate their energy transition while avoiding common pitfalls. The references [6] [9] [10] underscore the importance of renewable energy in achieving sustainable development goals.

It is essential to continue investing in infrastructure and network management to maximize the benefits of renewable energies and meet the growing energy demand.

This study provides actionable insights for policymakers, engineers, and stakeholders to harness renewable energy’s full potential while addressing its technical and operational complexities. By aligning infrastructure development, policy support, and technological innovation, Senegal can serve as a regional model for sustainable energy transition.