This article proposes a novel optimal hybrid control framework to improve the voltage profile of highly unbalanced Distribution Grids (DGs) by coordinating the injection of reactive power from multiple off-board Electrical Vehicles (EVs) chargers. It exploits the time-synchronized measurements advantages, centralized control, and local controllers embedded into a hierarchical and scalable scheme, coordinated by the distribution system operator (DSO). The proposed framework is aimed to increase the modern electrical networks' flexibility, reliability, and stability. It is powered by the Eigensystem Realization (ER)-based system identification technique, a Linear Quadratic Gaussian (LQG) controller, the Distribution-level Phasor Measurement Units (D-PMUs), and a new aggregator agent that handles the EV chargers power injection to precisely and timely regulate the dynamic voltage response in a sub-area or the entire DG. The robustness and feasibility of the proposal are demonstrated by employing simulated scenarios with unbalanced faults, latency in communications, and highly unbalanced loads conditions on the IEEE 13 and 123 nodes test feeders, compensating the voltage variations accurately in less than 205 ms. The promising outcome of this study suggests a novel application for an emerging measurement-based control system in the operation of modern active DGs.
1 December 2019 in Electric Power Systems Research
Wide-area monitoring systems (WAMS) are spread in many power systems around the world, which demonstrate their significance and potential for power system operators. Thus, this paper emphasizes the use of synchronized-measurements-driven applications in power systems. To this end, two Matlab-embedded applications are developed using the graphical user interface (GUI) environment of Matlab. The former provides synchrophasor estimates that are processed and stored by means of a phasor estimation algorithm and a database, respectively; meanwhile the latter consists of a power system modal monitor application that is able to capture the modal information corresponding to low frequency oscillations (LFOs) in power systems. Also, the DIgSILENT PowerFactory environment is employed for running EMT simulations, whose results provide instantaneous signals to the phasor estimation stage in Matlab. Finally, results exhibit a WAMS simulator dealing with a LFO captured by PMUs, showing the performance of three traditional technique for identifyina electromechanical modes in power systems.
1 September 2019 in IEEE Latin America Transactions
The automation of biodigesters using programmable logic controllers (PLCs) is well established, yet mixing schedules are configured empirically, regardless of substrate characteristics. This study proposes a Substrate-Driven PLC Control (SD-PLC) methodology for fixed-dome biodigesters, in which every timing setpoint is derived from a measured substrate property: the homogenization pulse from the rheological mixing time (Metzner–Otto regime), the maintenance interval from a stratification and a substrate–biomass contact criterion, the duty-cycle ceiling from a net energy balance, and a safety gate from acid–base behavior (pH/EC). The methodology is instantiated on a 13.86 m3 fixed-dome biodigester in the Chillón Valley (Lima, Peru), co-digesting organic waste and guinea pig manure (30:70; theoretical methane potential 371 mL CH4 g−1 VS; field conversion ≈ 21%). The impeller operates in the transitional regime (–), the homogenization pulse is ≈22 min, and the reconciled duty cycle () remains a factor of four below the energy ceiling (). An influence × feasibility matrix identifies a low-cost sensor set (pH, electrical conductivity, temperature, level) that gates mixing. A reduced COD-based dynamic model shows that, under acid shock, continuous mixing suppresses methanogenesis through shear while the absence of mixing fails through contact deficit, so that only the stability-first strategy preserves the process. The principal contribution is the methodology itself—a reproducible mapping from substrate characterization to PLC timing design—rather than the hardware.