Dynamic properties of the virtual synchronous machine (VISMA)

Abstract

The increasing integration of decentralized electrical sources is attended by problems with power quality, safe grid operation and grid stability.The concept of the Virtual Synchronous Machine (VISMA) [1] discribes an inverter to particularly connect renewable electrical sources to the grid that provides a wide variety of static an dynamic properties they are also suitable to achieve typical transient and oscillation phenomena in decentralized as well as weak grids.Furthermore in static operation, power plant controlled VISMA systems are capable to cope with critical surplus production of renewable electrical energy without additional communication systems only conducted by the grid frequency. This paper presents the dynamic properties "damping" and "virtual mass" of the VISMA and their contribution to the stabilization of the grid frequency and the attenuation of grid oscillations examined in an experimental grid set.

Evaluation of Virtual Synchronous Machines With Dynamic or Quasi-Stationary Machine Models

“…Thus, the overall control systems presented in the literature are not directly comparable. For instance the reference frame used for the VSM implementation, the applied current control loops and also the implementation of the virtual swing equations differ between the control systems in [4], [5], [7], [8] and [22], [23], respectively. To ensure a fair comparison that can reveal the main implications of using DEM-and QSEM-based approaches for providing current references, the VSM implementations from the literature have been adapted to a common implementation, as fully revealed in the following sub-sections.…”

“…are adapted from [4], [5], [7], [8] and [22], [23] respectively, into a common framework for comparison. Linearized smallsignal state-space models of both alternatives are also developed, and their validity is verified by time-domain simulations.…”

“…1, a simple strategy for active damping according to [26], [27] is included in the current controller output voltage according to (6). The damping voltage v * ad , is given by (8), where the states φ represent low-pass filters implemented in the SSRF.…”

Comparison of methods for implementing virtual synchronous machine on inverters

“…Up to now the VISMA was implemented by using a voltage-tocurrent model on a hysteresis controlled inverter [1][2] [3]. This method will be called VISMA-Method 1 here.…”

“…These weaknesses can be compensated by using the VISMA concept and thus the power system quality will be improved. Furthermore, the penetration level of the DG sources won't be restricted any more.Up to now the VISMA was implemented by using a voltage-tocurrent model on a hysteresis controlled inverter [1][2] [3]. This method will be called VISMA-Method 1 here.…”