One can define an energy system as a system that converts one or more energy fluxes into other energy fluxes of a different kind. This definition may describe a relatively small system, for instance, a power plant, a chemical plant, or the heating and cooling apparatus of a single-family house, as well as one covering larger energy needs, for example, those of a city, a country, or even a continent. As energy systems are developed through the centuries, the way we structure these systems goes through changes affected by contextual conditions. Recently, concerns about the availability of traditional fossil energy sources and their environmental effects are revolutionizing the way energy systems are planned, designed, and operated.

Power electronics based Medium-Voltage Direct Current (MVDC) Microgrids consist of several interconnected feedback-controlled switching converters. Such systems experience bus voltage stability challenges owing to the negative incremental resistance of Constant Power Loads (CPLs) and converter control loop interactions. To tackle the stability challenges, this paper presents the application of the Interconnection and Damping Assignment Passivity Based Control (IDA-PBC) approach to the Port-Controlled Hamiltonian (PCH) model of Dual Active Bridge (DAB) source-side converters in a MVDC Microgrid. For the DABs, a Fundamental Average Model (FAM) approach considering Phase Shift Modulation (PSM) is provided and used for deriving the corresponding IDA-PBC control law. We analyze the effectiveness of the controller on large signal scenarios considering disturbances such as load step up, and DAB disconnection. Hardware-in-the-Loop (HiL) experiments using Opal-RT and Labview FPGAs, as well as, low power prototype tests are carried out to demonstrate the validity and feasibility of the proposed approach.

This paper investigates the influence of control bandwidth on the stability of loads, which are interfaced through power electronic converters and are fed from a dc power source. When tightly regulated, these loads exhibit a constant power load (CPL) behavior. It is shown here that the ideal CPL assumption, prevalent in literature, may not represent the worst case in real-life applications. If the control bandwidth of the load is sufficiently high, the load behaves like a CPL, and the system stability margin decreases with the increase in output power. However, in a practical range, with a lower control bandwidth, the system stability margin is influenced critically by the converter’s characteristic impedance, as well as its output power. Under these conditions, the minimum stability margin may occur at a low-power range.

Power-electronics-based Medium-Voltage Direct Current (MVDC) shipboard power systems consist of several interconnected feedback-controlled switching converters. Such systems suffer from stability degradation owing to the negative incremental resistance of the Constant-Power Loads (CPLs). To tackle the stability problem, system-level stabilizing control methods were proposed acting on either the load-side or the source-side converters. In this paper, the three-phase dual-active bridge (DAB3) dc-dc converter is considered to realize the MVDC bus. A master-slave control approach is introduced which not only ensures system-level stability but also optimizes the load-sharing among the DAB3 converters. A nonlinear control technique for the master controller is compared with the PI controller with linearized feed-forward compensation. The comparison is performed through simulations in Matlab/PLECS.

This paper presents a new control method for power electronic interfaced distributed energy resources in DC grids. The proposed control method relies on a data-driven identification approach that is used in an adaptive control framework and does not require accurate models of the converters or offline training for control synthesis. In this paper, the proposed control method is able to guarantee a good performance and bus voltage stability without prior knowledge of the uncertainties. These uncertainties include measurement noise and network-induced phenomena from interactions with neighboring nodes, such as system reconfigurations resulting from converters connection/disconnection.

This paper presents measurement techniques for multipoint synchronized recordings in offshore wind farms (OWFs). Wind farms in the German North Sea are clustered and connected to the public grid via large-scale HVdc converters. One of the main risks for the OWF operators is the quality of the grid connection provided by the transmission system operator. Dynamic influences originated in the transmission system or neighboring wind farms cause power quality (PQ) disturbances, and may seriously affect the production of a wind farm up to damages of the equipment. This paper shows how to treat the challenges of continuous multipoint synchronized PQ recordings in the OWFs concerning the expected phenomena, meter placement, event source allocation, instrument transformer usage, and time synchronization. Furthermore, it describes the different device categories and how the records of continuous recording high-resolution PQ devices are compared to the ones of a common oscilloscope. After the description of the applied measurement method, with the product standard and the project specific requirements, the catalog of requirements for the measurement system is defined. Linking the PQ data with the theoretic active power production enables the wind farm operator to measure the influence of the grid connection on the yearly energy yield and therewith can figure out the technical and operational improvements.