# Hybrid PV-Wind, Micro-Grid Development Using Quasi-Z-Source Inverter Modeling and Control—Experimental Investigation

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## Abstract

**:**

## 1. Introduction

## 2. Hybrid PV-Wind Micro Grid Structure

#### 2.1. PVG Mathematical Model

#### 2.2. Wind Turbine Modeling

_{T.S}) curve is plotted for different β

_{P.B}(Pitch blade angle) in Figure 3.

_{Wind}), R

_{T}(Turbine radius) and C

_{PR}(Performance coefficient) as:

_{T.S}) can be described mathematically which is correlated with an angular velocity of the blade (ω

_{A.V}), V

_{Wind}and R

_{T}as:

_{T.S}and β

_{P.B}(Pitch blade angle) as:

#### 2.3. Electric Equivalent Circuit of the Battery Model

## 3. Power Electronic Converters used to Control the Proposed Micro Grid System. Description and Mathematical Modelling

#### 3.1. SEPIC Converter Model

#### 3.2. Modified Power Ratio Variable Step Based P&O MPPT

#### 3.3. Quasi Z-Source Inverter Mathematical Modeling

_{A}, L

_{B}, C

_{A}, C

_{B}components with impedance circuit. The considered Z-Source Quasi inverter has no filter requirement, better buck/boost characteristics, able to regulate the phase angle output, less size, continuous conducting mode working, less harmonic content, high efficiency and with better power performance over the conventional inverter as major advantages. The Quasi Z-source inverter operates in two modes of operation. In the non-shoot mode, the equivalent circuit has 6 active states with 2 zero states. The T

_{S}is the total switched inverter with T

_{A}and T

_{B}as the shoot through the state and the non-shoot through state, respectively. The duty ratio D

_{duty}of SEPIC converter is mathematically written as:

## 4. Experimental Setup Description and Results

#### 4.1. Description of the Experimental Setup

_{PV}and I

_{PV}respectively. The power factor coefficient and THD are evaluated using the power quality analyzer (FLUKE 43B), considering the main components of the converter: IGBT (IRG4PH50U), diode (Freewheel RHRG30120), driver circuit (HCPL 3120) etc. permanent magnet synchronous generator (PMSG) based wind emulator system is employed as the wind turbine generator and is mechanically coupled with the DC-motor. The switched mode power converter makes the wind turbine to have varying wind speed which produces the required mechanical torque by controlling wind turbine characteristics.

#### 4.2. Experimental Results and Scenarious Development

## 5. Conclusions

- (i)
- The MPRVS based P&O MPPT performance with SEPIC converter has been validated effectively, which delivers MPP achievement with low power oscillation for the PV system.
- (ii)
- The performance of the Quasi Z-source inverter has been evaluated experimentally as having better buck/boost characteristics with fast dc-link voltage regulation under different operating conditions.
- (iii)
- The proposed QZsi topology for a hybrid PV-Wind Turbine application in a micro grid enhanced reliability, good output power quality and efficiency improvements.
- (iv)
- Experimental results under dynamic conditions, such as step-changed in wind speed or solar irradiation, reveal that optimal power has been tracked through the PV-Wind renewable sources and proved the validity of the proposed solution.
- (v)
- The two-diode model-based PV Generator provides high power extraction when compared to the single diode model.

## Author Contributions

## Funding

## Conflicts of Interest

## Nomenclature

R_{SE} | Resistance in series |

R_{Parallel} | Resistance in parallel |

T_{STC} | Temperature at STC (Standard Test Condition) |

G_{STC} | Solar irradiance at STC |

K_{S} | Coefficient of short circuit current |

${I}_{Photon\_STC}$ | Photo current at STC |

${T}_{C}$ | Ambient temperature |

G | Solar irradiation |

I_{Short_STC} | Short circuit current at STC |

V_{open_STC} | Open circuit current at STC |

V_{Thermal} | Diode thermal voltage |

K_{VL} | Voltage temperature coefficient |

ρ_{a,d} | Air density ρ_{a,d} |

ω_{G} | Speed of generator |

ω_{GM} | Peak allowed generator speed |

η_{gear} | Gear ratio |

E_{B} | Battery fixed voltage |

V_{PO} | Polarized voltage |

Q_{Bat} | Capacity of battery |

I_{Battery} | Battery current |

A_{exp} | Amplitude of exponential zone |

B_{exp} | Inverse time constant exponential zone |

$\u2206{I}_{{L}_{A}}={I}_{{L}_{B}}$ | Current ripple |

∆V_{0} | Ripple voltage |

${f}_{switching}$ | Switched frequency |

${V}_{0}\left(N\right)\&{I}_{PV}\left(N\right)$ | Sensed voltage and current |

∆D | Step perturbation of duty ratio |

dT | Fixed step size |

K | Variable power ratio |

PI | Proportional Integral |

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**Figure 2.**Equivalent circuit model of a PV cell with double diodes and a series and parallel resistance.

**Figure 3.**CPR (Performance coefficient) Vs tip speed (λ

_{T.S}) curve is plotted for different β

_{P.B}(Pitch blade angle).

**Figure 10.**Developed experimental setup of the proposed hybrid micro grid system based on a real-time digital simulator-dSPACE platform.

**Figure 11.**Experimental results (

**a**) during a step-changed in wind speed; (

**b**) wind power; and (

**c**) Duty cycle of Cuk converter.

**Figure 13.**(

**a**) Capability of the proposed hybrid micro grid under varying wind velocity and constant solar irradiation; (

**b**) Behavior responses of the hybrid micro grid under varying solar irradiance and constant wind velocity.

**Figure 14.**The performance of the hybrid micro grid (

**a**) load cutting condition; (

**b**) Load removing condition.

**Figure 15.**The performance of the wind generator is evaluated under disconnecting operating conditions to the micro grid.

**Figure 16.**The performance of the wind generator is evaluated under reconnecting operating conditions to the micro grid.

SI. No. | Parameters | Value |
---|---|---|

1. | Inductors (${L}_{A}={L}_{B}$) | 0.42 mH |

2. | Capacitors (${C}_{A}$ = ${C}_{B}$) | 3.5 × 10^{−3} µF |

3. | Current ripple ($\u2206{I}_{{L}_{A}}$ = $\u2206{I}_{{L}_{B}}$) | 0.5 A |

4. | Voltage ripple ($\u2206{V}_{o}$) | 1 × 10^{−3} V |

5. | Switching frequency (${f}_{switching}$) | 20 Hz |

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## Share and Cite

**MDPI and ACS Style**

Priyadarshi, N.; Padmanaban, S.; Ionel, D.M.; Mihet-Popa, L.; Azam, F. Hybrid PV-Wind, Micro-Grid Development Using Quasi-Z-Source Inverter Modeling and Control—Experimental Investigation. *Energies* **2018**, *11*, 2277.
https://doi.org/10.3390/en11092277

**AMA Style**

Priyadarshi N, Padmanaban S, Ionel DM, Mihet-Popa L, Azam F. Hybrid PV-Wind, Micro-Grid Development Using Quasi-Z-Source Inverter Modeling and Control—Experimental Investigation. *Energies*. 2018; 11(9):2277.
https://doi.org/10.3390/en11092277

**Chicago/Turabian Style**

Priyadarshi, Neeraj, Sanjeevikumar Padmanaban, Dan M. Ionel, Lucian Mihet-Popa, and Farooque Azam. 2018. "Hybrid PV-Wind, Micro-Grid Development Using Quasi-Z-Source Inverter Modeling and Control—Experimental Investigation" *Energies* 11, no. 9: 2277.
https://doi.org/10.3390/en11092277