Grid Integration of a Dual Two-Level Voltage-Source Inverter Considering Grid Impedance and Phase-Locked Loop

Abstract

This paper proposes a dual two-level voltage-source inverter (DTL VSI) and its control to effectively integrate two dc sources into the multi-infeed ac/dc (MIACDC) power architecture of fully integrated power and energy systems (FIPESs). The current-controlled method is also synthesized and proposed to control the grid-connected DTL VSI. To this end, this article provides mathematical analyses comparing the DTL VSI with the conventional current-controlled grid-connected two-level VSIs (TL VSIs). The linearized state-space models of both systems are mathematically derived for analyzing the dynamics of both structures. These models reveal the salient feature of the proposed DTL VSIs used in grid integration. To this end, space-phasor analysis is employed, and the dynamics of the phase-locked loop (PLL) and the grid impedance are also considered. The proposed grid-connected DTL VSI (with the current-controlled algorithm) not only in weak grids (for normal grid conditions) but even after fault removal (for faulty grid conditions) stabilizes the active and reactive power dynamics with improved transient performance compared to that of its conventional counterpart. Therefore, it enhances the operation range of the VSIs integrating various entities in FIPES' MIACDC power architecture. This paper provides supportive simulation results and experiments generated by MATLAB and a scaled-down test rig, respectively.

A Novel IGDT-Based Method to Find the Most Susceptible Points of Cyberattack Impacting Operating Costs of VSC-Based Microgrids

“…Also, it has not contributed to the secondary control of multiple, connected converters so that few VSCs are needed to be examined either. If this work is related to either case stated above, with the currently owned devices (e.g., the pieces of equipment applied in [3], [7], [15]), it will be practicable to conduct the tests associated with those controls using either a single converter or multiple ones. Instead, this work has, however, researched tertiary controls and studied the cyberattack's impacts on the Moreover, in this research, it has been required to apply the per-unit numbers associated with operating costs-with the base of OC * (i.e., operating costs for "without"-cyberattack conditions) as per this paper's contributions and requirements, which have been described in the write-up.…”

“…All in all, it is impossible to achieve that system by physical devices considering our facilities. More importantly, based on this paper's scope, it is not required to arrange testing methods similar to what should be done for controlling a single converter or even a few (see [3], [7], [15]).…”

“…That is why they have been referred to as the general term of "VSC"s since their mode of operation is not required to be specified as per the scope of this research. In other words, VSCs may interface a dc subsystem to an ac subsystem-with either a unidirectional power flow [7], [15] or a bidirectional one [12]-depending on the required power flow. A converter is called a rectifier if the flow of average power is from the ac side to the dc side, while it is called an inverter if the average power flow is from the dc side to the ac side.…”

Virtual Inertia Implementation in Dual Two-Level Voltage Source Inverters

“…By utilizing two M level inverters in the dual inverter configuration, the output voltage level will be equal to a 2M-1 level inverter voltage level. It leads to a reduction in switching losses and lower switching frequency [15]. The advantage of implementing two isolated DC link voltage sources is the elimination of zero sequence current (ZSC) [14].…”

“…When a fault happens in one of the inverters, then another one can continue to work and inject its part of the power to the electrical grid. In the dual inverter configuration, the phase difference of voltage reference space vectors of the two inverters must be 180 o to reach the maximum output voltage [15]. The magnitude of their reference voltage space vectors is the same.…”