Steady‐state operating points of islanded virtual synchronous machine microgrid

• Published in: Energy science & engineering Vol. 12; no. 5; pp. 2220 - 2235
• Main Authors: Kamilu, Sanusi Alabi, Beck, Hans‐Peter
• Format: Journal Article
• Language: English
• Published: London John Wiley & Sons, Inc 01.05.2024; Wiley
• Subjects: Algorithms; Buses; Distributed generation; droop control; Electric potential; Electrical loads; Frequency stability; islanded microgrid; load flow analysis; Stability analysis; Steady state models; steady‐state operating points; Synchronous machines; Systems stability; Time domain analysis; virtual synchronous machine; Voltage
• ISSN: 2050-0505; 2050-0505
• DOI: 10.1002/ese3.1739

Before starting stability analysis of the multivirtual synchronous machine (n‐VISMA) power system, it is necessary to obtain the steady‐state operating points (SSOPs) of all dynamic nodes in the network. Modified traditional iterative schemes using the concept of droop bus technique in an islanded microgrid are not feasible for load flow analysis of VISMA microgrid incorporating non‐control dynamics. This paper proposes closed‐form steady‐state, fundamental‐frequency models for islanded VISMA microgrids using the concept of virtual swing buses. In this technique, the virtual internal buses of all VISMAs in the network are governed by the swing equation. The voltage at all buses is variable except the virtual buses in which the pole wheel voltages are prespecified. The algorithm was extended by a droop control localized to each VISMA. The suitability of the proposed algorithm to obtaining SSOPs of VISMA was tested on IEEE‐9 bus system with VISMA replacing electromechanical synchronous machines and also on a low‐voltage distribution system. To validate the applicability of the proposed algorithm and prove its accuracy, the case study systems were also modeled in the SIMULINK environment for detailed time domain analysis. The algorithm was found to be computationally effective for a load flow analysis of the VISMA microgrid. The results also reveal that the addition of external droop control improves the frequency stability of the system. Virtual swing bus algorithm: The graphical s illustrate the virtual synchronous machine (VISMA) control scheme together with stationary operating points evaluation technique for an islanded microgrid. The novel concept employs the use of constant amplitude of virtual excitation and virtual torque localized to each VISMA unlike the droop bus approach that uses active and reactive power coefficients as major constant control parameters. The algorithm is modified accordingly when an outer power loop controller is added to improve the operational flexibility of the grid‐connected inverters.