1,721,571 research outputs found
Electromagnetic Time Reversal Applied to Fault Location: On the Properties of Back-Injected Signals
Full text linkBy using the electromagnetic time reversal (EMTR) theory, the paper studies its properties in order to derive a new fault location method to be used in power networks. It is shown that, in the reversed-time stage, the current signal observed at the true fault location can be clearly distinguished since it appears as a time-delayed copy of the back-injected fault-originated transient signal. Then, based on this similarity property, a fault location method is derived. Finally, the method is numerically validated with reference to a reproducible simulated power network composed of an inhomogeneous multi-conductor transmission-line system.SCI-STI-FRDES
Model-less Measurement-based Computation of Voltage Sensitivities in Unbalanced Electrical Distribution Networks
Full text linkWithin the context of microgrids optimal voltage control, most schemes proposed in the literature either rely on (i) droop-control methods or (ii) methods involving the computation of explicit nodal power set-points as a solution to a given optimization problem. The first category of approaches is in general suboptimal as it relies on locally sensed measurements. The second category guarantees some level of optimality but requires an accurate and up-to-date model of the network that is, in general, not always available in low voltage grids. To overcome the aforementioned limitations, in this work we propose a methodology suitable for voltage control in generic low voltage 3-phase unbalanced grids. It can be used for the computation of either explicit power set-points or to define the droops of local voltage regulators. Its main characteristic is that it does not rely on the knowledge of the system model and its state. In particular, the goal is to compute linearized dependencies between voltage magnitude and nodal power injections, i.e., voltage sensitivity coefficients. The proposed method assumes availability of a monitoring infrastructure and the computation of the desired sensitivities involves the solution of an over-determined system of linear equations constructed solely using available measurements of nodal power injections and voltage magnitudes. The proposed method is also capable to account for the measurement errors and their time correlation. The performance evaluation of the proposed method is carried out using real measurements coming from a real low voltage feeder located in Switzerland equipped with an appropriate metering infrastructure.DES
An Adaptive Model-Based Real-time Voltage Control Process for Active Distribution Networks Using Battery Energy Storage Systems
Full text linkThe paper presents a centralized real-time adaptive and model-based voltage control algorithm for Active Distribution Networks (ADNs). Differently from the available literature, the proposed algorithm merely relies on the control of Battery Energy Storage Systems (BESSs). In this respect, an experimentally model-fitted two-time constant dynamic model of BESS is used. In particular, this model is used to compute the constraints of the BESSs in terms of DC active power at each controller iteration. These constraints are subsequently used in the central controller for the solution of the optimal voltage control problem. The performances of the proposed method are compared with those obtained for the case where BESSs are modeled as ideal energy reservoirs. Such an assessment is carried out using a numerical example referring to IEEE 13 buses distribution test feeder suitably adapted to include stochastic generation and BESSs.DESLDES
Siting and Sizing of Energy Storage Systems: Towards a Unified Approach for Transmission and Distribution System Operators for Reserve Provision and Grid Support
Full text linkThis paper presents a method to determine the optimal location, energy capacity, and power rating of distributed battery energy storage systems at multiple voltage levels to accomplish grid control and reserve provision. We model operational scenarios at a one-hour resolution, where deviations of stochastic loads and renewable generation (modeled through scenarios) from a day-ahead unit commitment and violations of grid constraints are compensated by either dispatchable power plants (conventional reserves) or injections from battery energy storage systems. By plugging-in costs of conventional reserves and capital costs of converter power ratings and energy storage capacity, the model is able to derive requirements for storage deployment that achieve the technical-economical optimum of the problem. The method leverages an efficient linearized formulation of the grid constraints of both the HV (High Voltage) and MV (Medium Voltage) grids while still retaining fundamental modeling aspects of the power system (such as transmission losses, effect of reactive power, OLTC at the MV/HV interface, unideal efficiency of battery energy storage systems) and models of conventional generator. A proof-of-concept by simulations is provided with the IEEE 9-bus system coupled with the CIGRE’ benchmark system for MV grids, realistic costs of power reserves, active power rating and energy capacity of batteries, and load and renewable generation profile from real measurements.DES
Accurate Parameter Estimation on Photovoltaic Modules Using Fisher Information Matrix and D-Optimal Design
Full text linkAccurate estimation of the equivalent circuit parameters of photovoltaic modules enables
comprehensive analysis of photovoltaic system’s electrical behaviour and facilitates the detection of
faults. This paper proposes a rigorous method for optimizing the current-voltage curve measurements by
minimizing the variance of the estimated parameters in the typical photovoltaic five-parameter equivalent
circuit model. Leveraging the Fisher Information Matrix and the D-optimal experiment design technique,
the proposed method aims to improve the accuracy of parameter estimation by optimizing the distribution
of current or voltage sampling points, reducing the overall parameter uncertainty as quantified by
the determinant of the inverse of Fisher Information Matrix. The study investigates both current and
voltage-based sampling approaches, showing that current sampling is preferable under partial shading,
while voltage sampling can be equivalently employed under uniform irradiance. The method is validated
through both numerical simulations and experimental data from five real photovoltaic modules under
both partial shading and uniform irradiance conditions. Experimental validation was conducted on five
commercial photovoltaic modules of different technologies, including monocrystalline, polycrystalline, HIT,
and TOPCon, confirming that the proposed optimization strategy consistently enhances estimation precision,
with variance reductions up to two orders of magnitud
Aggregation of Power Capabilities of Heterogeneous Resources for Real-Time Control of Power Grids
Full text linkAggregation of electric resources is a fundamental function for the operation of power grids at different time scales. In the context of a recently proposed framework for the real-time control of microgrids with explicit power setpoints, we define and formally specify an aggregation method that explicitly accounts for delays and message asynchronism. The method allows to abstract the details of resources using high-level concepts that are device and grid-independent. We demonstrate the application of the method to a Cigre benchmark with heterogenous and lowinertia resources.LCA2DES
Hardware-in-the-loop Validation of the Grid Explicit Congestion Notification Mechanism for Primary Voltage Control in Active Distribution Networks
Full text linkThe Grid Explicit Congestion Notification control mechanism (GECN) is a broadcast-based real-time demand- response mechanism designed for primary voltage control in Active Distribution Networks (ADNs) [1,2]. An extensive set of off-line simulations has indicated that GECN is a promising candidate for deployment in the real field. However, prior to the actual deployment of the control mechanism, it is crucial to validate its performance when controlling a real grid. For this purpose we design and develop a dedicated experimental Hardware-in-the-Loop (HIL) test platform for the real-time val- idation of GECN. The HIL architecture consists of a Real-Time Simulator (RTS) where a real distribution feeder is modeled, together with controllable loads and the associated measurement infrastructure composed by virtual PMUs. These virtual metering devices stream data, via Ethernet, to a local Phasor Data Con- centrator suitably coupled with a Discrete Kalman Filter State Estimator. The estimated network state is received by a GECN network controller. We close the control loop by transmitting the computed broadcast control signals back to the network buses in the RTS using a micro-controller. By using this experimental setup we are able to (i) assess the performance of the whole control process in terms of voltage optimality and time latencies in a realistic setting and (ii) implement the GECN controllers into dedicated equipment that with the proper ruggedization can be readily deployed in the real field.LCA2DES
- …
