Abstract
With a shift towards 100% clean energy on a global scale, the face and structure of electric power systems are changing at a fast pace. The process of integrating renewable energy involves the usage of power electronic based converters called VSCs (Voltage Source Converters). As the share of generated power by directly connected synchronous machines becomes less, new perspectives over the definition and interpretation of “frequency” must be considered. Although in most cases, frequency of a bus (e.g., VSC’s bus) can be estimated by using PLL (Phase-Locked Loop), but this approach does not provide any knowledge on how the frequency of a voltage-source converter needs to vary to provide specific control. A novel method to control VSCs (voltage source converters) was proposed, which provides a clear definition for the frequency of these devices. Based on the proposed method, the frequency of the integrating bus of the converter is considered as an independent control input, which will be the “cause”, and not the “effect” of the control action. By this definition, the frequency of the converter can be limited within constraints when enough energy support does not exist from the DC side. Moreover, the use of PLL (phase-locked loop) to observe frequency will not be necessary, as it will be determined through the action of the controller. Textbooks and technical papers are referenced, and MATLAB, Simulink and SimPowerSystems software are utilized for simulation purposes.