# Real-Time Implementation of Robust Control Strategies Based on Sliding Mode Control for Standalone Microgrids Supplying Non-Linear Loads

^{*}

## Abstract

**:**

## 1. Introduction

_{2}emissions [5,6,7,8]. In [9], a hybrid wind-diesel system-based solution is proposed, and in [10,11] solar-wind-diesel hybrid systems are suggested. These solutions are effective from the point of view of fuel consumption but hard to implement in practice. Recently, in [12], many technical solutions with reduced number of power converters, are suggested to reduce the complexity of hybrid standalone system and achieve high performance from the available energy sources (ESs) in isolated localities.

- (1)
- Standalone microgrid -microgrid configurations with less power converters where SPVA and battery energy storage system are controlled using only one DC-DC buck-boost converter to connect and control the lead acid battery pack.
- (2)
- Using only one PI controller with anti-windup for the outer control loop for DC-link voltage regulation.
- (3)
- Replacing the PI controller by a SMC with boundary layer in the inner control loop for single-phase d-q control strategy, which is proposed for power quality improvement.
- (4)
- Developing a new control strategy based on sliding mode control for DC-DC buck boost converter where the system parameters are taken on consideration in equivalent control.
- (5)
- Achieving maximum power point tracking (MPPT) from SPVA by controlling only the DC link voltage.
- (6)
- Employing the boundary layer in SMC to reduce the chattering phenomena.

## 2. System Description and Operation Mode

## 3. Control System

#### 3.1. Control of the DC-DC Buck-Boost Converter

#### 3.1.1. Modeling of the DC-DC Buck-Boost Converter

_{bat}) controlled switches (S

_{8}and S

_{9}), inductor (L

_{b}), output voltage (V

_{dc}) and a capacitor (C

_{dc}). Depending on the state of the switches, the state-space equations of the DC-DC buck boost converter when the switch is ON are written as:

_{1}by i

_{bat}, and x

_{2}by V

_{dc}, then; $\dot{{x}_{1}}=\frac{d{i}_{bat}}{dt}$, $\dot{{x}_{2}}=\frac{d{V}_{dc}}{dt}$. The state-space equations, which are expressed in (1) and (2) are written as:

#### 3.1.2. Sliding Mode Control for the DC-DC Buck-Boost Converter

#### 3.1.3. Selection of the Sliding Surface

_{1}and β

_{2}represent the sliding gains and they should be positive.

_{PV}), which is selected equal to 350 V. As presented in Figure 3, V

_{PV}corresponds to the maximum extracted power from the SPVA for different solar irradiations. Therefore, by controlling the DC-link voltage, one can easily extract the maximum of power without using any MPPT method.

#### 3.1.4. Equivalent Control

#### 3.1.5. Stability Analysis

#### 3.2. Control of Three-Phase Voltage Source Converter

_{p}) is calculated as:

#### 3.2.1. Sliding Mode Current Controller

#### 3.2.2. Selecting the Switching Surface

#### 3.2.3. Stability Analysis

## 4. Results and Discussion

## 5. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 4.**Diagram of $\dot{{x}_{1}}=f\left({x}_{1}\right)$ with: (

**a**) ${\beta}_{1}=0.001,\text{}{\beta}_{2}=0.8$, and ${\beta}_{3}=0.05$, (

**b**) ${\beta}_{1}=0.01,\text{}{\beta}_{2}=0.8$, and ${\beta}_{3}=0.09$, and (

**c**) ${\beta}_{1}=0.001,\text{}{\beta}_{2}=0.8$, and ${\beta}_{3}=5$.

**Figure 7.**Dynamic performance under presence of balanced RL nonlinear load and solar irradiation change.

**Figure 8.**Zoom of waveforms of Figure 6 between (

**a**) t = 0.8 s to t = 1 s, (

**b**) t = 1.6 s to t = 1.8 s and (

**c**) between t = 2.7 s to t = 2.9 s.

**Figure 9.**Dynamic performance under presence of balanced and unbalanced nonlinear load (diode bridge +RL and RC loads) and solar irradiation change.

**Figure 10.**Zoom of the waveforms of Figure 6 between (

**a**) t = 0.8s to t = 1 s, (

**b**) t = 1.6 s to t = 1.8 s and (

**c**) between t = 2.7 s to t = 2.9 s.

**Figure 11.**Harmonics spectrum of the PCC voltage, DG current and load current with RL and RC nonlinear loads.

**Figure 13.**Dynamic performance under sudden variation of: (

**a**) balanced RL nonlinear load, (

**b**) balanced RC nonlinear load, and (

**c**) under switching on and off of RL nonlinear load.

**Figure 14.**Dynamic performance under fixed solar irradiation and load change. (

**a**) sudden increase and decrease of load; and (

**b**) sudden decrease and disconnect of load.

Parameters | Value | Parameters | Value |
---|---|---|---|

${v}_{DG}$ | 208 V | ${k}_{1}$, ${k}_{i1}$, | 0.1, 25 |

${f}_{r}$ | 60 Hz | ${F}_{sw}$ VSC | 10 kHz |

$\text{}{V}_{dc}^{*}$ | 350 V | ${C}_{dc}$ | 1000 µF |

${C}_{PV}$ | 100 µF | ${L}_{inv}$ | 5 mH |

${L}_{b}$ | 1.5 mH | ${R}_{inv}$ | 0.01 Ω |

${F}_{sw}$ DC-DC Converter | 10 kHz | ${R}_{c}$ | 5 Ω |

${\beta}_{1},{\beta}_{2}\mathrm{and}{\beta}_{3}$ | 0.001, 0.8 and 5 | ${C}_{c}$ | 10 µF |

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**MDPI and ACS Style**

Benhalima, S.; Miloud, R.; Chandra, A. Real-Time Implementation of Robust Control Strategies Based on Sliding Mode Control for Standalone Microgrids Supplying Non-Linear Loads. *Energies* **2018**, *11*, 2590.
https://doi.org/10.3390/en11102590

**AMA Style**

Benhalima S, Miloud R, Chandra A. Real-Time Implementation of Robust Control Strategies Based on Sliding Mode Control for Standalone Microgrids Supplying Non-Linear Loads. *Energies*. 2018; 11(10):2590.
https://doi.org/10.3390/en11102590

**Chicago/Turabian Style**

Benhalima, Seghir, Rezkallah Miloud, and Ambrish Chandra. 2018. "Real-Time Implementation of Robust Control Strategies Based on Sliding Mode Control for Standalone Microgrids Supplying Non-Linear Loads" *Energies* 11, no. 10: 2590.
https://doi.org/10.3390/en11102590