The ever-growing penetration of converter-interfaced distributed renewable energy sources (CI-DRES) combined with the presence of non-linear loads (NLLs) might generate serious power quality issues ...in distribution networks (DNs). Currently, numerous approaches have been proposed for CI-DRES voltage source converters (VSCs) to operate as active harmonic filters; however, most of them mitigate the problem locally without investigating which CI-DRES in the DN would be most appropriate to perform such service. In this paper, a sensitivity analysis is conducted, and a mathematical framework is formulated to assess and quantify the contribution of each CI-DRES to the decentralized harmonic filtering process in a low-voltage (LV) DN with the presence of NLLs based on the location and available capacity of each CI-DRES. The latter is a crucial element since, in the future, the CI-DRES may offer various services simultaneously, e.g., reactive power or virtual inertia. The proposed framework and analysis are verified via simulations in the time domain and via decoupled harmonic power flows considering the benchmark CIGRE LV DN and the IEEE European LV Test feeder under various mixtures of CI-DRES/NLLs. The conclusions will pave the way so that active filtering is treated as a new ancillary service that CI-DRES can offer and it can be introduced in relevant markets.
The ever-increasing penetration of distributed renewable energy sources, e.g., photovoltaics (PVs), poses new technical challenges, jeopardizing the reliable operation of power systems. For this ...reason, battery energy storage (BES) are situated alongside PV systems to provide ancillary services (ASs) to system operators. However, BES operation is often limited due to the restricted number of operating cycles. In this paper, a methodology for the assessment of the provision of voltage regulation and power smoothing services by PV-BES systems is presented, taking into account the capacity degradation of BES. The proposed framework involves quasi-static simulations incorporating the operating conditions of the distribution network. A battery aging model is used to estimate the BES capacity loss caused by both the calendar and the cyclic aging mechanisms. The updated BES capacity sets new constraints on its operation and consequently influences the efficiency of the provided ASs. A parametric analysis is conducted to investigate the impact of the most critical parameters on the BES capacity degradation.
The advent of distributed renewable energy sources (DRESs) has led to a series of technical issues affecting the secure and reliable operation of active distribution networks. Among them, ...under-/overvoltages, current overload, and voltage unbalance can be considered as the most important problems limiting the increase of DRES penetration. In this paper, a new control architecture is proposed to overcome these issues using the reactive power of DRESs and the active/reactive power of distributed battery energy storage systems (DBESSs). Its distinct feature is the implementation in the symmetrical components domain, allowing the efficient decoupling between under-/overvoltage and voltage unbalance mitigation techniques. Furthermore, a central controller is introduced to improve the system performance in terms of reduced network losses and effective DBESS utilization by coordinating the response of DRESs and DBESSs. The validity of the proposed control strategy is evaluated by performing time-domain and time-series simulations on the IEEE European LV test feeder.
•Unified control strategy for unbalanced low voltage distribution grids.•Voltage regulation, voltage unbalance mitigation and congestion management control.•Distributed generation and energy storage are used as the main control units.•Implementation of the control schemes in the symmetrical components domain.•Performance evaluation by conducting time-domain and quasi-static simulations.
The advent of renewable energy sources (RESs) has posed several technical challenges related to the operation of modern power systems. These can be classified into two main categories: (a) problems ...at the power system level, and (b) local problems at the distribution network (DN). To solve these issues, there is a strong need for the development of innovative control schemes that can be employed by converter-based network assets, e.g., battery energy storage (BES) systems and distributed RES. In this context, a unified control system (UCS) for the provision of ancillary services (ASs) by distributed RES-BES systems within a multi-services perspective is introduced in this paper. The proposed UCS comprises different algorithms to provide ASs related to voltage regulation, voltage unbalance mitigation and frequency support. The UCS is implemented in 3-phase, 4-leg converters (3Ph4LCs) to ensure the provision of ASs in unbalanced DNs. In addition, at the dc side of the 3Ph4LC a series dc–dc converter for BES support allows the implementation of the proposed UCS in weak DNs. The transient operational performance of the proposed UCS is evaluated by conducting time-domain simulations.
•A unified control system for the provision of ancillary services is introduced.•It employs voltage regulation, voltage unbalance mitigation and frequency support.•The proposed algorithms are integrated into a 3-phase, 4-leg converter.•A power oscillation damping technique is introduced to improve PLL performance.•Time-domain simulation results verify the performance of the proposed control system.
Power Flow of Islanded AC Microgrids: Revisited Kryonidis, Georgios C.; Kontis, Eleftherios O.; Chrysochos, Andreas I. ...
IEEE transactions on smart grid,
2018-July, 2018-7-00, Letnik:
9, Številka:
4
Journal Article
Recenzirano
In this letter, a new methodology is proposed to extend the applicability of conventional power flow methods to islanded microgrids (MGs), operating with the droop control method. A slack bus is ...considered to be connected at a random MG node. The operational conditions of this slack bus as well as of the rest MG nodes are determined through an iterative procedure. The objective of this procedure is to force the active and reactive power flowing through the slack bus to zero, representing the islanded MG operation. The proposed approach has a similar accuracy with time-domain simulations, while it reduces significantly the required computational burden.
•Smoothing line switching of Microgrids.•Minimization of line current.•Network reconfiguration of Microgrids.•Control of distributed generators.
This paper deals with a new smooth line-switching ...method that facilitates the network reconfiguration of islanded networks. Its distinct features include the ability to handle network asymmetries and to minimize the line current during the switching action. This is attained by developing a three-phase sensitivity-based method to determine the operating set-points of distributed generators (DGs) that minimize the current of the candidate line participating in the switching action. These set-points correspond to the positive-sequence powers as well as to the negative- and zero-sequence currents of DGs. Furthermore, the network constraints such as voltage limits and power limits of DGs are always satisfied. Simulations are performed in a balanced 33-bus islanded network as well as in the unbalanced IEEE 8500-node network to evaluate the performance of the proposed method.
A new perspective on the synchronverter model Kryonidis, Georgios C.; Malamaki, Kyriaki-Nefeli D.; Mauricio, Juan Manuel ...
International journal of electrical power & energy systems,
September 2022, 2022-09-00, Letnik:
140
Journal Article
Recenzirano
In this short communication, a modified version of the well-established synchronverter model is proposed, introducing improved control characteristics that allow the efficient integration of ...converter-interfaced renewable energy sources to the electrical grid. In the proposed model, the inertial response is decoupled from the primary frequency response. Furthermore, a condition for a critically damped provision of inertial response is proposed. The improved performance of the proposed model against the variants of the synchronverter model is assessed by performing time-domain simulations and stability analysis.
•Control algorithm that decouples inertial response from primary frequency response.•Closed-form formula for critically damped provision of inertial response.•Improved damping against the current state-of-the-art solutions.
The high penetration of renewable energy sources (RES) interfaced with power electronics together with new non-linear loads pose new challenges in the grid operation. In fact, power systems with ...reduced inertia and high harmonic distortion will be common in a near future. Recently, the grid-forming operation of voltage source converters (VSCs) has emerged to address these challenges, mimicking the contribution of synchronous generators to the system inertia. In addition, these grid-connected VSCs can be used at the same time for reducing the harmonic distortion by applying active filtering techniques. However, these harmonic compensation algorithms can generate VSC overloading. This paper proposes a method for dynamically adjusting the individual virtual impedance of the filtered harmonics to prevent the power converter overcurrent. For this purpose, the value of each harmonic virtual impedance is modified according to a priority which can be set by the final user according to the established power quality standard. The paper includes a theoretical stability analysis of the controller and experimental results to validate the proposed algorithm.
