A cross voltage-levels simulation approach for interaction analysis in converter-dominated distribution networks

Abstract:
The paper presents a concept for a cross voltage-level interaction study in the German distribution grid. The high-voltage network was modeled and simulated by P & M Power Consulting GmbH, the medium voltage level modeled and studied the TU Ilmenau electrical energy supply and power electronics and the low voltage level was modeled and analyzed by the Fraunhofer IOSB-AST Group Energy Systems and Components of the Energy Division. In a model of a typical high voltage distribution grid, the dynamic behavior of the subordinate edge network in the region of small signal excitations was simulated by means of transmission functions. This method enables dynamic, stress-spanning RMS simulations taking into account large equivalent edge networks with a relatively low calculation effort. This contribution illustrates an experimental method for determination of system stability as well as it shows the destabilizing effect on the system stability of a European medium voltage energy grid. It can be concluded that with an increased number of converters the overall system stability declines in form of a low damping factor, raising overshoot and settling time. The previous works about the instability that is induced by converters considered only the effects for investigations that have been focused on converter based level approaches. For die investigation in low voltage grids the converter based load and generator are modeled and simulated in commercial software DIgSILENT PowerFactory. The simulational study of low voltage grids shows, that specific parameters of grid components can increase the negative influences on Power Quality.