Horst Schulte

The increasing penetration of converter-interfaced generation raises critical concerns for power system stability, especially during rapid transients and system split events that are not yet adequately addressed in current grid code compliance tests. This paper assesses the resilience of a Virtual Synchronous Machine (VSM) compared with a grid-following photovoltaic (PV) inverter using a combined framework of standardized benchmark tests and realistic system-split scenarios. In benchmark testing, the VSM provided synthetic inertia by delivering a transient power burst from 0.30 p.u. to 0.545 p.u. under a -0.4 Hz/s frequency ramp, corresponding to an equivalent inertia constant of approximately 15s. With the Limited Frequency Sensitive Mode-Underfrequency (LFSM-U) function enabled, it sustained additional active power up to 0.61 p.u. once the frequency fell below 49.8Hz. The PV inverter, by contrast, demonstrated compliance with conventional grid requirements: it curtailed power through LFSM-O during overfrequency conditions. It injected 0.25 p.u. of reactive current during a fault ride-through (FRT) event at 1.129 p.u. voltage. In system-split tests, the VSM absorbed surplus PV generation, stabilizing frequency after a transient rise to 52.8 Hz and preventing voltage excursions exceeding 1.2 p.u. During imbalance stress, it absorbed 1.266 MW against its 1.0~MW rating, corresponding to a 26.6 % overload. These results demonstrate that while the PV inverter contributes valuable voltage support, only the grid-forming VSM maintains frequency stability and ensures secure islanded operation. The novelty of this study lies in integrating standardized compliance tests with system-split scenarios, thereby providing a comprehensive framework for evaluating grid-forming controls from both regulatory and resilience-oriented perspectives and informing the evolution of future grid codes.

This paper proposes a non-invasive method for the detection of parameter variation in DC-DC buck power converters. It is computationally efficient and only requires the usual current and voltage sensors. The method is presented in several steps. First, a generic buck converter model is presented. Then, the general design of a sliding mode observer is described as well as its method of fault reconstruction. This sliding mode observer is then adapted to detect parameter changes of the buck converter model. Finally, simulations are performed to validate the observer design.

In this paper, a model-reference control scheme for wind turbine systems in the Takagi-Sugeno framework is proposed. This work deals with the model reference control approach to provide wind turbines’ fast frequency response (FFR) in fluctuating wind conditions. The proposed scheme is applied to a generic wind turbine model for the partial and full-load region. The controller coefficients are calculated using a set of proposed Linear Matrix Inequality (LMI) conditions. The design process is described in detail, including a controller performance in the wind turbine’s partial and full load region.

This paper presents a model-reference control approach for nonlinear systems in the Takagi-Sugeno form and applies it to photovoltaic power plants to provide instantaneous reserve. The proposed scheme is applied to a photovoltaic power plant with two stages separated into an aggregated photovoltaic array and DC/DC converter. The coefficients of the modelreference controller are calculated using a set of proposed linear matrix inequality (LMI) based conditions. In addition to the LMI constraint for the model reference design, the paper also introduces region constraints. It is shown how a suitable combination of the proposed constraints can specifically improve the controller performance. Simulation studies verify the applicability of the design approach.