Dual Two-Level Voltage Source Inverter Virtual Inertia Emulation: A Comparative Study

Mohammad Ali Dashtaki,Hamed Nafisi,Amir Khorsandi,Mojgan Hojabri,Edris Pouresmaeil

doi:10.3390/en14041160

Abstract

In this paper, the virtual synchronous generator (VSG) concept is utilized in the controller of the grid-connected dual two-level voltage source inverter (DTL VSI). First, the topology of the VSG and the DTL VSI are presented. Then, the state-space equations of the DTL VSI and the grid-connected two-level voltage source inverter (TL VSI), regarding the presence of the phase-locked loop (PLL) and the VSG, are given. Next, the small-signal modeling of the DTL VSI and the TL VSI is realized. Eventually, the stability enhancement in the DTL VSI compared with the TL VSI is demonstrated. In the TL VSI, large values of virtual inertia could result in oscillations in the power system. However, the ability of the DTL VSI in damping oscillations is deduced. Furthermore, in the presence of nonlinear loads, the potentiality of the DTL VSI in reducing grid current Total Harmonic Distortion (THD) is evaluated. Finally, by using a proper reference current command signal, the abilities of the DTL VSI and the TL VSI in supplying nonlinear loads and providing virtual inertia are assessed simultaneously. The simulation results prove the advantages of the DTL VSI compared with the TL VSI in virtual inertia emulation and oscillation damping, which are realized by small-signal analysis.

Highlights

In order to prevent the growing disadvantages of fossil fuels, the idea of using clean energies has become more critical in recent years
The distributed generations (DGs) is connected to the grid, and due to the controller method introduced in the prior Section, the DG
VSI advantages in improving the power system stability and damping the system fluctuations while utilizing the virtual synchronous generator (VSG) controller were proven through the small-signal analysis and simulation results

Summary

Introduction

In order to prevent the growing disadvantages of fossil fuels, the idea of using clean energies has become more critical in recent years. Photovoltaic (PV) systems and the wind turbines are employed much more than other clean energies to generate the requested electric power. In conventional centralized power supplies, lots of enormous synchronous generators (SGs) are responsible for providing electric energy for the loads. One of the most important differences between the conventional centralized power generations and the distributed generations (DGs) such as PVs and wind turbines is that DGs have a low amount of inertia to damp the frequency fluctuations. In the current power system, which consists of an inevitable number of DGs, the power system’s total inertia could be lower than the conventional power system that all the demanded power is supplied by SGs. the higher the DG’s penetration rate in the power system, the more frequency deviations could happen during transient situations

Methods

Results

Conclusion