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The use of distributed control systems for microgrid control has gained traction in recent years for their reliability and modularity. As part of microgrid control core functions, islanding is implemented to enhance power supply reliability during outages. This paper proposes a distributed multi-agent control system architecture for the management of microgrid assets. Specifically, it addresses the islanding problem, whereas three agent categories are designed to control distributed energy resources, loads and other assets. The proposed control approach is unique as it centrally sources critical commands while keeping the commands execution local and based on distributed coordination. Post-islanding transients are minimized and system stability is retained by implementing two distributed load shedding and load curtailment algorithms for unplanned and planned islanding events, respectively. A controller hardware-in-the loop real-time simulation on a modified CIGRE North American medium voltage distribution benchmark has been developed and used to demonstrate the effectiveness of the approach.

The gradually reduced inertia in powers system due to proliferation of renewable energy resource may lead to larger frequency deviation and change rate and thus fault protection triggering. Type-IV wind turbine generator (WTG) can provide inertia and damping via releasing the rotational energy by adopting virtual synchronous generator (VSG) control. However, the energy stored for inertia emulation depends on its machine side inertia and wind speed. To investigate its impact on inertia and damping emulation, linearized model of VSG-controlled type-IV WTG is established in the present research. It is revealed that lower machine-side inertia and higher wind speed will result in worse frequency response than the ideal VSG. An inverse control block is introduced to mitigate this effect. Supplementary control blocks are also added to limit the power and rotor speed of WTG and help damp the oscillation between synchronous generator and WTG. Comprehensive case studies demonstrated the effectiveness of the proposed control strategy.

Uncertainty associated with wind power generation in bulk power system operations requires increasingly systematic attention. As practical levels of wind power generation penetration keep on deepening in many power systems, it is now widely accepted that adequate supply of flexibility resources is essential to managing this uncertainty. This paper extends the notion of flexibility envelopes to network-constrained power systems and to systems with geographic wind power output correlation. Preliminary results indicate that flexibility envelopes are effective means of achieving flexibility adequacy.

A methodology for service restoration (SR) with an active management of cold load pick-up (CLPU) is developed in this paper. The proposed approach leverages remote control capabilities of most advanced metering infrastructure already deployed and seeks to limit feeder overloading by managing post-outage customer re-connections. Re-connection schedules for feeder customers are calculated through the solution of a mixed- integer linear programming (MILP) problem. Results of the proposed algorithm are compared against full feeder restoration.

This paper proposes an improved model predictive control (MPC) based approach for managing distributed energy resources (DER) of a microgrid. MPC based energy management systems are computationally intensive and can become too slow for online optimization. The main aim of this approach is to improve on the computational time and scalability of the current MPC based control schemes. This is done by decoupling the unit commitment (UC) and economic dispatch (ED) problems, and solving them separately. The control scheme takes into account the current and predicted prices of electricity, the forecasts of loads and availability of renewable energy. The proposed approach is compared to an MPC approach commonly found in literature. It performed better in terms of computation time and scalability, with a slight trade-off in cost minimization while respecting the constraints of the microgrid. The effectiveness of this approach is demonstrated using a mathematical model of a microgrid within the MATLAB environment.

This chapter brings together the modeling and validation of various components and control and communication schemes with their validation and implementation. It provides the data specifications and handling requirements, design criteria, required system studies, and applicable standards to consider for the design methodology to implement a microgrid. The chapter discusses the characteristic data that are required to perform loss and economic analyses of the microgrid design. The data are categorized into topology related characteristics; demand related characteristics; and economic/environment related characteristics. The chapter summarizes the recommended areas to define the microgrid design criteria. In microgrids, loads are broadly classified as critical or non‐critical loads, and therefore, can be prioritized according to their importance and functions. The chapter explains the four operational states of microgrids, namely, grid‐connected mode; transition to islanding mode; islanded mode; and reconnection to grid mode.

This chapter covers the information and communication systems requirements for the microgrids. The focus of the systems is on supporting seamless exchange of data and commands between participants in various transactions across the microgrid and the rest of the electric power system (EPS). Home area networks (HANs) provide a network for the non‐aggregated atomic nodes devices and enable communications within a home or end‐customer environment. Local area networks (LANs) provide a network backbone for the aggregated HANs via gateway applications and protocols like advanced metering infrastructure (AMI) and smart meters. The chapter classifies the available communication technologies into the physical media available for communications and then the technologies that can be implemented on the media. Several of the most common and applicable technologies for microgrid applications are discussed with their features, advantages, and disadvantages.

This chapter presents microgrid use cases that have been developed in terms of use case description, actor roles, information exchange and associations between objects of use case, and regulations. Only the use cases that have been identified as relevant for smart microgrid implementation are presented. The chapter covers three publicly available use cases, namely, the energy management system (EMS) functional requirements, protection, and intentional islanding as provided by the Oakridge National Laboratory (ORNL). The microgrid protection controller communicates with the microgrid supervisory control and data acquisition (MG SCADA) periodically to update the system status and determine the protection schemes and settings accordingly. Updated protection settings are distributed through communication links from the protection controller to all the protection devices with communication facilities. The microgrid controller initiates the process of intentional islanding transition by dispatching islanding transition commands to the actors of the microgrid.

This chapter presents the modeling details identified as required to perform various kinds of studies on the microgrid. It also presents analysis and assessment of the modeling details along with their trade‐offs for the studies. Energy management studies are conducted to test various energy management system operating modes. Conducting voltage control studies requires testing the microgrid voltage control loops in both grid‐connected and islanded modes of operation. Frequency control studies are performed to evaluate the performance of the frequency control loops or curves for various primary sources in the microgrid. Transient stability studies for microgrids look at the phenomenon of the microgrid returning to a stable operating mode after a large disturbance. Economic feasibility studies are performed on microgrid models to evaluate the economic benefits and for the cost‐benefit analysis. The power quality studies in microgrids are mainly related with voltage flicker, voltage sag/rise, and harmonics.

This chapter presents the models of the assets that could be used to accomplish the modeling of a microgrid. The models allow the testing of assets for unit tests and in a microgrid environment. The chapter also presents the structure of two generic load models that can emulate the steady‐state and dynamic behaviors of different loads. Most of the distributed energy resources (DERs) in microgrids are interfaced to the AC network by a power electronic converter. These converters are conventionally single phase two level, three‐phase two level or three‐phase three level voltage source converters (VSCs). The chapter explores a realistic and application‐oriented modeling of a photovoltaic (PV) module. The wind turbine is modeled as a controllable current source connected to a grid connected power electronic converter through a Resistive/Inductive (RL) choke and additional filters. The model of an energy storage system consists of a grid‐tie inverter whose DC‐link is fed from a lithium ion battery.

This chapter completes the modeling process by integrating the modeling approaches. The complete microgrid exists as a multidimensional layered structure. The overall microgrid modeling approach is shown as a flow chart. The IEC 61850 standard allows for communication between devices, where a peer‐to‐peer model for generic substation events (GSEs) services is used for fast and reliable communication between intelligent electronic devices (IEDs). The real‐time hardware‐in‐the‐loop (HIL) set‐up comprises one real‐time simulator (RTS), communicating using the IEC 61850 generic object‐oriented substation event (GOOSE) messaging protocol. The RTS provides an interface to publish and subscribe to GOOSE messages as per the substation configuration language (SCL) file defining IED configurations and communication. The RTS also provides a host computer interface whereby the user can monitor the real‐time waveforms and pass new settings to the real‐time model, if required.

This chapter discusses testing procedures for the microgrids and their controllers. It presents validation results for the modeling, control, monitoring, and protection strategies. The chapter discusses four different implementations on a real‐live microgrid: energy management system (EMS) economic dispatch; voltage and reactive power control; microgrid islanding; and real‐time (RT) system using the International Electrotechnical Commission (IEC) 61850 communication protocol. It demonstrates the implementation of the design guidelines of the microgrid systems on the campus microgrid's Open Access to Sustainable Intermittent Sources (OASIS) subsystem. The IEC 61850 standard allows for communication between devices, where a peer‐to‐peer model for generic substation event (GSEs) services is used for fast and reliable communication between intelligent electronic devices (IEDs). One of the messages associated with the GSE services is generic object oriented substation event (GOOSE), which allows for the broadcast of multicast messages across a Local Area Network (LAN).

System case studies are required for the analysis and evaluation of various microgrid operating scenarios and contingencies, for real time operation, and energy management of the generation, storage, and loads within the microgrid, in islanded and grid‐connected modes. The studies can be categorized into eight different areas. This chapter briefly explains these areas, which include operational planning, economic and technical feasibility, policy and regulatory framework, power‐quality, stability, microgrid design, communication and SCADA system, and testing and evaluating studies. Operation, planning, and design studies require serious consideration when planning microgrid integration. Economic and technical feasibility studies are done to assess and verify the economic viability of the microgrid project for whichever business case it is being designed. Power‐quality studies are important for the microgrid to provide high‐quality power to the loads that may be critical. Stability studies provide designers with the points of operation that bring the system closer to, or push it toward instabilities.

This chapter covers several control monitoring and protection schemes and strategies that can be used in microgrids to meet the requirements and objectives for which the microgrid is designed. It describes an enhanced control strategy for electronically coupled distributed energy resources (EC‐DERs) that improves the performance of the host microgrid under network faults and transient disturbances. The chapter introduces a decoupled control strategy that enhances the transient performance and stability of a droop‐controlled microgrid. It discusses a strategy to mitigate the impact of EC‐DERs on the protections systems of a microgrid and presents a control and management strategy for the integration of DERs in microgrids. The multi‐DER control strategy provides a central power‐management system (PMS) and a decentralized, robust control strategy for the autonomous mode of operation of a microgrid that includes multiple DER units. The chapter explains a communication‐assisted protection strategy implementable by commercially available microprocessor‐based relays for the protection of medium‐voltage microgrids.

In this paper, we apply a flexibility based operational planning paradigm to microgrid energy dispatch. The classic energy dispatch problem with energy storage and dispatchable thermal generation assets requires the solution of mixed-integer optimization problems. Such approaches are not amenable to most remote microgrids and practical field microgrid implementations, where controls are rule-based and typically implemented by programmable logic controllers. Albeit such rule-based dispatch controls are always feasible, they cannot optimize fully over the availability of renewable generation and asset capacities of microgrids, especially energy storage. In this paper we propose a systematic method to generate the microgrid dispatch rule base with the objective of matching as much as possible the control performance obtained by full mixed-integer optimization. To achieve this we develop a rigorous control mapping method based on decision trees. The numerical results demonstrate that the decision tree-based dispatch strategy can provide feasible and near optimal dispatch decisions for microgrids. Its computational efficiency is very high, a feature promising for real-time in-field implementation.

This paper presents an intelligent protection scheme for microgrid using combined wavelet transform and decision tree. The process starts at retrieving current signals at the relaying point and preprocessing through wavelet transform to derive effective features such as change in energy, entropy, and standard deviation using wavelet coefficients. Once the features are extracted against faulted and unfaulted situations for each-phase,the data set is built to train the decision tree (DT), which is validated on the unseen data set for fault detection in the microgrid. Further, the fault classification task is carried out by including the wavelet based features derived from sequence components along with the features derived from the current signals. The new data set is used to build the DT for fault detection and classifi- cation. Both the DTs are extensively tested on a large data set of 3860 samples and the test results indicate that the proposed relaying scheme can effectively protect the microgrid against faulty situations, including wide variations in operating conditions.

This paper proposes a quasi-steady-state modeling approach for an approximation of long-term frequency dynamics in power systems. A specific phenomenon of concern is an onset of frequency swings during load/generation imbalance scenarios. The effects of system voltage characteristics, system inertia, and, more importantly, damping controllers are explained and quantified using the described quasi-steady-state models. Application of the methodology to a 14-generator benchmark system demonstrates that described models are suitable for simulation of different disturbance scenarios that can trigger frequency instability. Moreover, linearization of the proposed models can provide convenient means for impact assessment and coordinated design of damping controllers. To demonstrate this, coordinated tuning of multiband power system stabilizers to improve frequency dynamics has been performed and validated through nonlinear simulations using a commercial transient stability software.

This paper proposes a dual three-level, T-type, neutral-point clamped (T-NPC) inverter fed dual permanent magnet synchronous motor topology for low-voltage, high-power traction applications. The switching pulses of the T-NPC inverters are interleaved and controlled, such that they produce equal and opposite three-phase currents at their output. This maintains balanced dc-link voltages in steady-state and transient conditions, even with slight mismatches between two sets of three-phase loads. Thus, the proposed configuration decouples the modulation strategy from the capacitor balancing control. Simulation and experimental results demonstrate that in comparison to the conventional single T-NPC inverter, the proposed topology reduces dc-link capacitors’ voltage deviation and current stress by more than 90% while avoiding additional switching instances to balance capacitor voltages.

This study proposes a methodology based on multivariate analysis and data mining techniques that credibly captures the signature of the DG-islanding phenomenon under adverse operating conditions and network faults. This methodology produces decision trees which determine the tripping logic, protection handles and thresholds for each DG-islanding relay within the distribution network under study. Case study results indicated that the intelligent islanding relay (IIR) produced by the proposed methodology is consistently high-level performance in terms of dependability and security, and features reduced non-detection zones compared with the currently used islanding devices. It is also demonstrated how to determine adaptive settings to accommodate entire ranges of system operating conditions applicable to different ranges of power mismatches (overbalance, underbalanced and near balanced) at the point of common coupling bus. Experimental validation for prove-of-concept of the proposed IIR using hardware-in-the-loop has been conducted which was consistent with the off-line test results.

In this paper, we propose a decentralised algorithm for coordinating the charging of multiple plug-in electric vehicles (PEVs) and extend it to a hybrid version by including the PEV's charging strategies into the optimisation function. Going one step further, we also consider coordinated workplace charging integrating PV panels. The main focus of our work is to conduct a comparative study between a centralised benchmark algorithm, and the proposed decentralised and hybrid approaches from both communications and power perspectives. All algorithms are co-simulated over a converged fiber-wireless communication infrastructure of 342 residential customers. Power system results prove the efficiency of the proposed algorithms providing up to 19% peak shaving while meeting drivers' requirements. Communication results of the decentralised algorithm compared to a centralised benchmark scheme provided better performance, measuring an upstream traffic rate of 1.28?Mbps with a maximum delay of 0.629?ms. Compared to the decentralised algorithm, the hybrid algorithm showed a promising improvement for large fleets of PEVs accompanied with an overhead communication cost that is significantly less than that of the centralised algorithm.

The emerging trend for electric utilities to install wind-based generation on a large scale into distribution networks, employing a doubly fed induction generator or full-converter turbine technologies is raising issues for distribution planning engineers with regard to flicker among other power-quality (PQ) issues. This paper investigates dynamic volt/var control, a viable flicker mitigation technique which exploits the reactive power capabilities of modern power-electronic interfaced wind turbine generators. Dynamic volt/var control essentially mitigates flicker by solely dispatching reactive power based on voltage fluctuations within the flicker frequency band. This technique can be incorporated as part of a wind farm multiobjective reactive power-control scheme, which facilitates regulating: 1) the voltage level at the point of common coupling (PCC), employing slow-acting voltage control or power factor control and 2) the flicker level at the PCC with fast-acting dynamic volt/var control. This two-level approach can reduce the wind farm flicker level up to 80% and maintains the voltage level at the PCC well within acceptable bands. The results presented in this paper focus on a typical 25-kV medium-voltage distribution feeder integrating wind-based generation on a large scale. The performance of the two-level controller was tested for varying levels of penetration and wind speed conditions. The applicable standards and utility grid-code requirements are considered throughout.

Rao S. Thallam Salt River Project 18.1 The Need for Reactive Power Compensation 18-1 Shunt Reactive Power Compensation . Shunt Capacitors 18.2 Application of Shunt Capacitor Banks in Distribution Systems—A Utility Perspective 18-2 18.3 Static VAR Control 18-3 Description of SVC . How Does SVC Work? 18.4 Series Compensation 18-5 18.5 Series Capacitor Bank 18-6 Description of Main Components . Subsynchronous Resonance . Adjustable Series Compensation . Thyristor Controlled Series Compensation . STATic COMpensator 18.6 Defining Terms 18-12

With the growing deployment of microgrids, it is urgent to standardize microgrid control system and the test procedure. In this paper, implementation and testing of a microgrid control system with transition and dispatch function is presented. To alleviate power fluctuations due to renewable energy and control the power at point of interconnection (POI) to zero for planned islanding, tie-line flow control is adopted in grid-connected mode. Voltage-frequency control applied to energy storage system can achieve stable frequency and active re-synchronization in islanded mode. State-of-Charge and power-limiting based dispatch rules are employed in both grid-connected and islanded mode to maintain power balance while reducing fuel consumption. Power balancing upon unplanned islanding is achieved by emergency dispatch. Technique for smooth transition is also adopted to reduce the impact on the breaker at POI and mitigate the disturbance of distributed renewable resources during islanding/reconnection. The control algorithm is implemented with controller hardware-in-the-loop (CHIL) test bench.

The rapid growth in renewable generation in distribution system is introducing significant uncertainties and technical challenges in the energy management of the grid. This paper develops the concept of flexibility envelopes for distribution systems. Flexibility envelopes provide bounds on uncertain power flows and bus voltages caused by renewable generation fluctuation with certain confidence levels. First, shift factors for the distribution network are derived based on a set of linearized distribution power flow equations. Flexibility envelopes are obtained based on these shift factors. We demonstrate the effectiveness of our approach on the IEEE-33 bus system.

The challenge of microgrid protection is associated with many factors, such as frequently changing conditions and topology, lack of established power flow direction, presence of inverter-interfaced generation, among others. To overcome the challenges faced by the conventional protection, the paper demonstrates the application of a synchrophasor-based state estimation algorithm for protection of microgrids. The approach is tested on a model of an existing microgrid/test feeder. The results show the inherent flexibility of the approach towards changing conditions of microgrid operation. It requires minimum coordination that ensures quick detection of various types of faults in different locations.

An improved dynamic state estimation (DSE) scheme is presented in this paper that estimates the states of generator as well as exciter field voltage and output mechanical torque from governor. Using the phasor measurement unit (PMU) signal connected to the nearest bus from generator, state variables of generators and controllers are estimated using Extended-Kalman filter (EKF) formulation. Also the overall model order for estimator has been kept at minimal while detailed model have been considered in simulation. Furthermore no assumptions have been made about exciter and governor model structure or parameters. Simulations have been performed on the benchmark New England test system which demonstrates the enhanced estimation performance of proposed technique.

In this paper, phasor measurements taken from stator and rotor terminals are used for dynamic state estimation of a doubly fed induction generator (DFIG) assuming a reduced order model (3rd order) with unknown mechanical input torque. The proposed estimator provides the advantage that the converter and associated controller dynamics as well as turbine and drive train need not be modelled. In addition the reduced order model reduces the computational complexity of state estimator significantly in comparison to previously reported DFIG models (15th order). Also this modeling of DFIG provides an additional benefit of minimal knowledge of system parameters i.e. only induction generator parameters are required to be known. Dynamic State Estimation has been performed using Extended Kalman Filter with Unknown Inputs (EKF-UI). Performance of proposed estimator has been demonstrated on a benchmark IEEE network modified by augmenting a wind farm consisting of multiple DFIG.

The transformer-less modular multilevel converter (MMC) DC-DC converter can achieve direct DC-DC conversion without an intermediate AC transformer. In this paper, a transformer-less MMC DC-DC converter topology with bi-directional DC fault blocking capability is proposed. The proposed converter comprises half bridge submodules (HBSMs) and full bridge submodules (FBSMs). Use of FBSM eliminates the large AC filter which is normally required in the transformer-less topologies. Moreover, the proposed topology has the capability to block the DC fault at either DC side. Once an DC fault is detected, the switches in SM are blocked and the capacitors of HBSM in one DC side are inserted in the fault circuit path. The fault current charges the inserted capacitors and thus reduces to zero quickly. The performance of the proposed topology is validated in a study system using a real-time simulation tool.

Multi-band power system stabilisers (MB-PSSs) PSS4B (IEEE standard 421.5-2005) are advanced power system damping controllers that have evident advantages over conventional PSSs in damping low-frequency oscillatory modes. However, finding optimal settings for such controllers is challenging due to the increased complexity of the PSS4B structure. This study describes a methodology for MB-PSS parameter optimisation based on an improved modal performance index as a measure of the controller's stabilising effect. The tuning problem is formulated as a non-linear constrained optimisation search method: proposed modal performance index is chosen as an objective function to be minimised, while properly selected constraints ensure stability of the closed-loop system and robustness of the proposed design. The methodology is demonstrated on a benchmark system that is based on an existing network. Comparative analysis between the MB-PSSs with optimised settings and speed-based PSS1A-type stabilisers designed using the conventional methods show the practicality and effectiveness of the proposed methodology. The implemented approach has an advantage of being scalable and suitable for the model-based tuning of feedback controller of general structure. Additionally, several performance metrics and non-linear simulations in the ElectroMagnetic Transient Program (EMTP) software confirm superior characteristics of PSS4B.

Many benefits can be achieved through the implementation of a Microgrid controller, such as minimized cost, reduction in peak power, power smoothing, greenhouse gas emission reduction, and increased reliability of service. However, most Microgrid controllers found in the literature and in the industry optimize a single objective, which either exacerbates or does not solve the problems with integrating a high penetration of renewable energy. This paper presents a methodology of formulating a multiobjective optimization (MOO) so that each objective is quantified through valuation functions that can be specific to every Microgrid. The proposed approach attains a Pareto-optimal solution by directly comparing the quantified valuation functions and solving as if it were a single-objective optimization (SOO) problem. Three cases of controllers are presented and compared: 1)a base case system with no controller; 2)an SOO that optimizes the cost of energy; and 3)an MOO that optimizes five identified benefits. Results show that the proposed controller can mitigate the negative impacts of volatile generation to levels below that of the system load.

The small-signal stability of an interconnected source and load can be analyzed using the frequency-response methods of stability analysis. Existing frequency-response methods of stability analysis introduce artificial conservativeness and do not explicitly address stability robustness against load perturbations, that is, by how much the load can change such that the system will remain stable in the small-signal sense. This paper presents a frequency-response method of stability analysis which provides a less conservative stability condition compared to existing methods, in the sense of having less restriction on the control system; further, the proposed method establishes a robust stability margin in terms of perturbations in load parameters. The proposed method is based on μ analysis, and models the source-load dynamic interaction via a closed-loop system of impedances and admittances. The proposed method is used to examine small-signal stability of an islanded subnetwork extracted from a university campus microgrid, composed of a distributed energy resource (DER) unit feeding a load, providing a study with realistic parameter values. Two case studies are presented to show the features of the proposed method, namely, reduced conservativeness and the establishment of a robust stability margin. Another example is provided to show the application of the proposed stability analysis method in a multi-DER-unit network. The findings of the frequency-domain analysis are illustrated through time-domain simulations around the operating point on the system under study.

Wind power (WP) penetration in weak distribution networks is associated with adverse impacts on voltage quality. The installation of an energy storage system (ESS) is a possible voltage quality remedy in such milieus. This paper proposes a supercapacitor ESS for alleviation of voltage flicker resulting from WP integration. The proposed ESS control and management are tailored to that purpose such that the ESS offsets the flicker-producing fluctuations in the generated WP. The proposed power sizing of the ESS is defined by the estimated turbulence intensity and wind speed average at the installation site. A 2 MW wind generator of the doubly fed induction generator type is employed as a source of WP and simulations are conducted on a simplified test system, as well as a detailed 25 kV distribution network on which results are compared with acknowledged reactive power flicker mitigation approaches and verified by prototyping in a real-time simulation platform. The flicker measurement procedure is conducted per IEC Standard 61000-4-15.

For microgrids with multiple distributed energy storage units (ESU) operating in islanded mode, it is important to maintain desirable frequency and voltage performance while avoiding over-degradation of certain ESU. In this paper, a control strategy with State-of-Charge (SoC) balancing capability and improved dynamic performance is proposed. The washout-filter based power sharing gets rid of secondary control needed for voltage and frequency deviation due to conventional droop control. The SoC balancing is realized by adjusting the power reference instead of modifying the droop slope, so desirable frequency performance can be maintained. The transient virtual resistance (TVR) can increase damping of the system without introducing voltage deviation in steady state. Parameters of the washout filter, TVR and SoC balancing control are tuned based on small-signal analysis of the reduced model of microgrids. The proposed control strategy is verified with Matlab/Simulink simulation.

The Quebec government is boosting transportation electrification in their fight against climate change. An extensive network of fast charging stations is indispensable for the proliferation of electric vehicle (EV), as it provides a way to charge an EV in a short time. This paper focuses on operational planning and energy management in a fast charging station. First the statistical characteristics of charging demand and the forecast error of embedded station photovoltaic generation are modelled. An energy scheduling strategy of fast charging station is then developed based on the concept of flexibility envelope. In the proposed strategy, the parameters of flexibility requirements are adjusted according to the state of charge of station battery. The performance of the strategy is then evaluated in terms of the stations daily financial performance and customers' waiting time. Using these performance metrics, a set of case studies are conducted to verify the effectiveness of the proposed strategy.

A study of effect of parametric variability on dynamic state estimates of synchronous generator operating using terminal Phasor Measurement Unit has been conducted. Parametric variations have been modelled using Monte Carlo method and state deviation from actual ones has been presented using suitable metrics. In addition impact of individual parametric variations on all the states have been studied as well. Furthermore, two Kalman filter variants (Extended Kalman Filter with unknown inputs and Unscented Kalman Filter) has been considered to ascertain whether choice of Kalman filter affects state estimates when subjected to parametric variability. Initial results have been performed on a Single Machine Infinite Bus (SMIB) system and consistency of the results has been validated on an interconnected network using the benchmark IEEE 39 bus system.

Accelerated developments of renewable energy production technologies and their integration to existing AC microgrids have led to the emergence of several new inverters control schemes. The recently introduced proportional resonant (PR) controllers have the ability to precisely track AC quantities and are increasingly used in grid supporting inverters, especially for current control loops which are at the heart of power transfers. In this paper, the PR-controller action is analyzed and an enhancement is proposed. It is shown that the classical implementation is particularly sensitive to high frequency noises coming from measurements and relocating the proportional action (RPA) on the feedback path can overcome this issue. The proposed improvement was evaluated using bit-true simulations in the Matlab/Simulink® environment. Obtained results show good noise and overshoot suppression using the proposed PR-controller with RPA.

Real-time simulation is an important tool of validating the performance of the modular multilevel converter (MMC). By using the field programmable gates array (FPGA), MMC valves with hundreds of sub-modules and the large number of inputs and outputs can be simulated in real-time. In the traditional FPGA based real-time simulation, only the MMC valves are implemented on FPGA, while the rest parts including AC or DC grids and inductors are implemented on CPU. However, the subsystem simulated on CPU has slower dynamics than the subsystem simulated on FPGA. There is a delay of CPU time-step between these two subsystems, which may affect the accuracy of the results especially under fault condition. This paper presents a real-time simulation of modular multilevel converters, and DC grids fully based FPGA with sub-microseconds time-step. Benefitting from using the electric hardware solver (eHS), all the components including the MMC valves and DC grid system can be easily implemented on FPGA. Thus, the high-fidelity of the simulation is guaranteed. The results of the proposed FPGA based real-time simulation are provided.

Multi-rate (MR) simulation is necessary for a system which contains both large and small time constraints. In the traditional MR real-time simulation of MMC, only the MMC valves are implemented on FPGA with a small time-step, while the rest parts are implemented on central processing units (CPU) with a large time-step. This paper presents a fully FPGA based MR real-time simulation of two MMC terminals. The FPGAs are decoupled by the stubline, and are parallelly simulated. Each FPGA is assigned with one MMC terminal, and its time-step can be flexibly chosen. The decoupled FPGAs can run asynchronously with their own model, which only communicate via the stubline without the synchro between them. Thus, the real-time simulation of a multi-terminal MMC-HVDC grid can be easily achieved while the accuracy of the simulation is also guaranteed. The real-time simulation results of the proposed methodology are provided.

High impedance fault (HIF) is problematic in various distribution systems, specially in rural distribution feeders. The fault current of HIF is with low magnitude, non-linear, asymmetrical and random, therefore extracting useful detection features from HIF current and voltage is the key to solve this issue. This paper experiments with 246 conventional electrical features and their combinations and proposes an effective feature set (EFS) via a feature ranking algorithm utilizing simple signal processing technique of discrete Fourier transform and Kalman filter estimation. This EFS is tested in six types of distribution systems and exhibits a promising detection performance in terms of accuracy, dependability and security once a proper pattern recognition classifier is determined. Besides conventional batch learning algorithms, the proposed detection method demonstrates a significant performance in online machine learning environment. Therefore it shows the potential of processing instantaneous signals and updating its prediction model adaptively to detect more HIFs in future smart grid.

In this paper, we evaluate a multi-objective-moving-horizon-optimization (MO-MHO) approach as an instrument for improvement of economic dispatch in microgrids. In particular, we investigate the effect of adaptation of the multi-objective optimization strategy used in the moving horizon framework on the end result of the economic dispatch. Power dispatch in microgrids is inherently a high-dimensional problem often cast as a mixed-integer stochastic program with conflicting objectives. Implied is the fact that exhaustive exploration of the whole Pareto front in a related multi-objective approach is not a computationally tractable decision tool. It is thus argued that it is preferable to represent the problem as a bi-objective optimization problem with the two costs grouping the least conflicting components. The solution method for the optimization problem over a window “looking into the future” can then be selected or adjusted in real time by employing an independent set of assessment functions evaluated along the trajectories of optimal multi-objective solutions already implemented over a window in the past. The proposed strategy is applied to a case study of a remote microgrid. Its performance is evaluated based on simulation results that suggest that choosing the compromise solution of the MO-MHO problem may be superior to the usual scalarization methods.

This chapter discusses data-mining-based catastrophe predictors using PMU-based WASI features. The study validates the performance of the black-box models such as SVM and RF through semitransparent data-mining models such as DT and transparent models such as DT_Fuzzy. It is observed from the extensive studies of the developed data-mining-based catastrophe predictors that while switching from the black box solutions to transparent and interpretable solutions, there is an unavoidable trade-off between accuracy, reliability, and security measures. The more transparent the predictor, the easier the implementation and maintenance by human actors. Overall, the fuzzy logic-based transparent solutions are preferred over black-box solutions to ease the implementation with improved robustness and enhance their suitability for auditing process, even sacrificing the predictive performance indices.

In this paper, we study the performance of multi-tier integrated fiber-wireless (FiWi) smart grid communications infrastructures based on low cost, simple, and reliable next-generation passive optical network (PON) with quality-of-service (QoS) enabled wireless local area networks (WLANs) in terms of capacity, latency, and reliability. We study the coexistence of human-to-human (H2H), e.g., triple-play traffic and machine-to-machine (M2M) traffic originating from wireless sensors operating on a wide range of possible configurations. Our analysis enables the quantification of the maximum achievable data rates of both event- and time-driven wireless sensors without violating given upper delay limits of H2H traffic. By using experimental measurements of real-world smart grid applications, we investigate the impact of variable H2H traffic loads on the sensor end-to-end delay performance. The obtained results show that a conventional Ethernet PON may cause a bottleneck and increase the delay for both H2H and M2M traffic. In contrast, by using a 10 G-EPON or wavelength division multiplexing (WDM) PON, the bottleneck arises in the wireless network. Furthermore, we study the interplay between time- and event-driven nodes and show that the theoretical upper bound of time-driven sensors decreases linearly as a function of the number of sensors, whereas with event-driven sensors, the upper bound decrease is nonlinear and more pronounced.

Feeder routing becomes more challenging as Distributed Generations (DGs) are increasingly embedded into the power distribution network. This paper presents a graph theoretic based feeder routing (a mixed non-linear integer optimization problem) in power distribution network including DGs. Graph theory is found to be much simpler and effective technique that significantly reduces the complexities of the search algorithms and provides the optimal radial path while minimizing the cost. The proposed technique has been extensively tested for different topologies of power distribution networks considering DGs and the results obtained for feeder routing is highly encouraging compared to the existing techniques. Also the reliability assessment is carried out to evaluate the reliability of the optimal radial networks including DGs.

The paper deals with developing and testing frequency-adaptive PMU algorithms with wider linearity range than specified in IEEE Std C37.118-1. This goal is achieved by means of three different concepts encompassing robust state-of-the-art design approaches: 1) FIR bandpass filtering, 2) extended Kalman filtering (EKF), and 3) discrete Fourier transform (DFT) demodulation with FIR low-pass smoothing. While FIR-based PMUs are linear phase with no overshoot in either phase or amplitude step responses, the adaptive EKF PMU is more computer-intensive but allows for a reduced group delay and better out-of-band interference rejection at the cost of a phase step response with overshoot. Frequency measurement performances of the various PMUs are assessed in detail. It turned out that FIR PMUs are best for meeting Std C37-118-1 metrics but they are outperformed by EKF under changing harmonics. Test results on three recent commercial PMU models further confirm that PMU algorithms meeting standard C37-118-1 can behave quite differently under dynamic conditions.

This paper investigates cyber-attacks compromising the data integrity of inverter-based islanded microgrids featuring an energy storage system (ESS), a wind turbine generator (WTG), a photovoltaic system (PV) and controllable loads. The ESS operates as the isochronous generator, responsible for forming the microgrid voltage and frequency, whereas the WTG and PV distributed energy resources (DER) operate in maximum-power-point-tracking (MPPT) mode. Mitigation solutions in the form of supplementary power control loops, employed on the power-electronic interfaced DERs are proposed in order to enhance the resilience of the microgrid to large voltage deviations resulting from cyber-attacks compromising data integrity. In the event where the supplementary control is no longer capable of compensating for the cyber-induced power mismatch, a load management scheme is proposed to curtail non-critical loads and prevent the microgrid voltage from collapsing. Simulation results validate the effectiveness of the proposed schemes on a 25 kV inverter-based microgrid benchmark.

The present paper investigates the effective application of phasor measurement units (PMUs) with different technologies and filtering dynamics to the design of wide-area power system stabilizer (WAPSS). Two frequency-adaptive PMU algorithms shown to exceed the C37.118 class-M requirements based on FIR- and Kalman-bandpass filtering are selected for study. Their sharp dynamic differences are characterized using accurate fourth-order transfer functions derived from step responses using system identification techniques. While FIR-based PMUs have no overshoot in their phase and amplitude step responses, the adaptive Kalman filter allows for better out-of-band interference rejection at the cost of a phase step response with overshoot and a higher computational burden. These PMUs are implemented in Simulink and then embedded in electro-magnetic transients (EMT) simulations to experiment the realistic WAPSS behavior with the discrete-time devices in the loop. It is shown that WAPSSs with optimized settings can improve the damping performance of EMT models of a test system and a simplified Hydro-Quebec network including PMU filtering dynamics and transmission delays. However, WAPSSs based on EKF-PMUs yielded better performances, thanks to their shorter group delay compared with FIR-PMUs. PMU devices and algorithms meeting standard C37-118 can thus behave quite differently under stressed dynamics.

In this paper, an integrated vehicle-to-grid, grid-to-vehicle, and renewable energy sources (IntVGR) coordination algorithm is proposed. The focus of this work is to provide a multidisciplinary study on implementing the proposed IntVGR scheme over a broadband fiber-wireless communications infrastructure by co-simulating both power and communications perspectives. For the power systems perspective, results show that the scheme is able to achieve a 21% reduction in peak demand compared to uncontrolled charging, and a better performance in flattening the overall demand profile and maintaining network constraints in comparison to a benchmark scenario. The scheme has also been demonstrated to successfully coordinate PEVs to take maximum utilization of local renewable energy. For the communications perspective, the measured upstream traffic for executing the proposed IntVGR scheme on a residential area of 342 households is found to be 1-2 Mbps with an end-to-end latency level of 1 ms. The scheme has also been validated from both perspectives in a sensitivity analysis with a higher PEV adoption rate.

When wind farms are connected to weak distribution networks, significant flicker emission can be expected, and it might not comply with the enforced grid code limits. This paper investigates and analyzes the impact of the possible wind generator reactive power control modes on the produced flicker levels. A frequency-selective reactive power control scheme is also proposed that makes it possible to mitigate the wind generator flicker emission under any reactive power exchange mode of the machine with the grid while respecting the grid code power factor restrictions. A realistic short-term wind profile is used and simulations are conducted on a 2 MW DFIG unit. Flicker measurement is carried out per IEC Standard 61000-4-15.

For the first time, IEEE Std. C37.118.1-2011 now provides metrics for PMU dynamic performance in terms of classes P and M filter designs. This paper attempts to determine whether fulfilling these requirements makes the PMU inherently well suited for stability control applications such as wide-area power system stabilizers (PSSs). In this aim, we considered two different frequency-adaptive approaches for class-P and -M compliance to ensure operation over a wide frequency range. The first is based on a finite-impulse response (FIR) with no overshoot in either the phase or the amplitude step responses, while the second is Kalman filter-based (EKF), which allows for a more refined out-of-band interference rejection at the cost of a phase step response with overshoot. These two approaches are benchmarked against Hydro-Quebec`s existing PSS requirements and the conclusion is that the total vector error-based response time is not indicative of the phase lag within the frequency band of interest, nor of the 3-dB bandwidth under sinusoidal amplitude/frequency modulation phenomena, which are key criteria when specifying PSS PMUs. Using simulated and field-recorded network fault responses, we also show that a class-M PMU is unsatisfactory for wide-area stabilizing control, unless its performance is improved during the fault period, which is not covered by Std. C37.118.1-2011.

Islanding protection is an essential and one of the more challenging aspect of distributed generation interconnection protection. This article demonstrates how intelligent relays, employing multivariate analysis and data mining techniques, can be used for the islanding protection of synchronous distributed generation in the presence of high-speed reclosing. The developed methodology is outlined and its application is illustrated for a number of diverse system operating states. The performance of the intelligent relays is assessed and compared against currently used islanding protection devices.