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Frequency is a useful parameter for ensuring the proper functioning of the power system operation, control, and protection. In this paper, a fast and accurate frequency estimator is developed using a Zero-crossing and a Peak, occurring in the buffered data instead of two Zero crossings, which is commonly used to measure the frequency. Prior to this, the signal is preprocessed using the Sliding Goertzel Filter (SGF) that mitigates the impact of undesirable features such as harmonics, noise, etc. from the signal. The two frequency estimators, with and without SGF, then work in parallel to form the hybrid estimator and named as $Z_{C}P_{k}-HFE$. The estimated frequency is chosen based on the minimum error computed from the two parallel estimators. The performance of the estimator is, then, validated using the simulated signals polluted with harmonics, noise, transients etc. Moreover, the evaluation results with the IEEE-13 Active Distribution Network (ADN) incorporated with Photovoltaic DG using and dSPACE1104 and Real Time Digital Simulator (RTDS), show its capability to estimate real-time frequency with satisfactory output.

With the integration of the large-scale wind farms, the conventional pilot protection is facing new challenges. It suffers from the performance degradation can even refuse operation for some extreme faut scenarios. To address this problem, this paper presents a novel pilot protection based on cosine similarity. The protection setting calculation and industrial application testing is investigated. The functional structure is described and the logic of the cosine similarity based protection is evaluated under different fault scenarios. Compared with the conventional differential protection, application of the proposed protection can greatly improve the relay performance. The proposed protection is embedded into an industry relay device, the standard hardware-in-loop tests are carried out using the real time digital simulator (RTDS) before the industrial application. Now the protection device based on cosine similarity is installed in the wind farms and put into operation in Inner Mongolia.

Distance relays are quite vulnerable to maloperation during dynamic stressed situations. The apparent impedance seen by the relay encroaches the zone-3 resulting in distance relay maloperation that can initiate cascading failures. This paper presents an enhanced scheme for wide area backup protection which implements improved protection algorithms to decide final relaying status. A machine learning tool namely Deep Neural Network is utilized to build those protective relaying decision logics: RDL-1 and RDL-2. Wide area information retrieved from phasor measurement units (PMU) is used to take real time decisions. RDL-1 is designed to detect if the system is operating in normal or stressed condition. During normal state, traditional zone-3 relay undertakes the relaying decision. However, under stressed situations, RDL-1 switches the decision-taking to RDL-2. RDL-1 also predicts whether the system is progressing towards an out-of-step situation so that appropriate remedial action can be undertaken. Proposed scheme was studied on IEEE-39 bus New England system using MATLAB/SIMULINK and validated on Real Time Digital Simulator platform and third zone mal-tripping are avoided. Performance of the proposed algorithm was compared with the conventional blinder and other data-mining techniques which show considerably high classification accuracy.

The main challenge of the microgrid is to design a suitable protection scheme due to the complexity of the architecture of the microgrid. The importance of the proposed protection technique is threefold. First, it presents a co-simulation platform to integrate between a simulated model on power system computer aided design (PSCAD)/real time digital simulator computer aided design (RSCAD) software's and physical devices schweitzer engineering laboratories (SEL) 421-7 relays to protect the microgrid that includes different resources connected based on inverter interface. Second, it presents a comprehensive hardware/software setup to test the protective relays in a closed loop system and shows how to configure the protective relay's International Electrotechnical Commission 61850 communications. Third, IEEE 1588 standard is used to provide sub nanoseconds latency between the simulated model that emulated on real time digital simulator (RTDS) and the external devices. Also, the measurement signals are synchronized between RTDS and the external devices using giga-transceiver synchronization card (GTSYNC) interface card and SEL-2488 satellite-synchronized network clock. The results showed that the co-simulation infrastructure introduces a highly dependable design, analysis, and testing environment for cyber and physical data flow in the system. Besides that, the voltages at ac/dc sides and frequency at fault condition were maintained due to the energy storage device contributions at different modes of operation.

The emerging trends in the microgrid development and the increasing penetration of distributed energy resources (DERs) in the distribution networks urge the modification in the existing conventional protection techniques. The integration of DERs changes the radial nature of the network, and thus, the schemes designed for such networks fail to operate for the microgrid system. Hence, a new fault detection technique is required for the microgrid system. In this article, a new fault detection scheme is developed for detecting the low-impedance faults (LIFs) as well as high-impedance faults (HIFs). The detection of HIFs is of major concern as these faults lead to a very low fault current value, which makes them undetectable by the conventional overcurrent relays. The proposed scheme uses the cumulative sum value of the differential negative-sequence impedance angle (DNSIA) as the fault detection parameter for generating the trip signal. The simulation results show that the proposed method effectively detects LIFs and HIFs accurately. The proposed scheme is independent of the type of faults, type of DGs, and the value of fault impedances. Furthermore, the proposed scheme also discriminates between the switching transients and faults effectively. The IEEE 13-bus test system is modeled and simulated on real time digital simulator (RTDS)/RSCAD platform. The method is further validated for the real-time implementation by developing the experimental setup for performing the control hardware-in-the-loop.

This article demonstrates the modeling of a real engine-generator set (genset) based on manufacturer data for use in controller-hardware-in-the-loop testing of microgrid control systems. The simulation environment used is RTDS Technologies’ real time digital simulator using PB5 cards. In addition, this article provides detail on integration of a commercially available controller with the simulator analog and digital inputs and outputs for control of the simulated genset. Testing of the developed model is performed to validate the standard parameters of the synchronous generator and the dynamic performance of the genset during starting, load acceptance, and load sharing between multiple gensets. By integrating controller hardware, time spent on modeling the genset frequency, voltage, and load sharing controls is avoided and valuable simulator processing capacity is saved. The result of this investigation is a genset model that exhibits the characteristics of real equipment and may be used in the validation of controller hardware and software for the derisking of microgrid control systems.

In this article, power converters are used in the integrated wind farms and can change the fault characteristics of the power system. The conventional pilot protection suffers from low sensitivity, or even the risk of maloperation. In order to address these problems, the fault features of the transient current of various power sources are analyzed and a novel pilot protection based on cosine similarity is proposed. To validate the proposed protection, the real time digital simulator hardware-in-loop tests are carried out to verify the proposed method. In addition, a field short-circuit test is conducted in a real wind farm to examine the performances of the proposed protection. The results demonstrate that the proposed method can be potential option for industrial applications.

Parallel operation of distributed power converters is used to realize high rated power and low current ripples with low rated power devices. It is also being preferred since central compensators fail to identify power quality problems reflected on low voltage levels, especially with the new structure of microgrids. This article proposes a novel parallel operation between modularized distributed transformerless unified power quality conditioner (TL-UPQC) for low voltage distribution networks. The operation is intended to improve the grid voltage profile while considering the connected modules rated capacity. The proposed methodology is suitable for smart grid applications where multiple renewable energy sources are integrated with the network. An advanced control technique that allows monitoring, wireless communication and coordination between the connected modules is presented. The proposed control methodology allows modularity and operation flexibility. System characterization has been studied to evaluate the influences of communication delays on overall system stability. The system has been evaluated by controller hardware-in-the-loop testing methodology. The power stage is simulated in a real time digital simulator, while the control algorithm is developed in a digital signal processor. Experimental results including random behavior of a photovoltaic system are presented.

Simulation has been widely adopted as a support tool for the validation and experimentation of distributed systems. It allows different devices and applications to be evaluated and analyzed without requiring the actual presence of those machines. Although the simulation plays an important role in investigating and evaluating the behaviors of devices, it results in a serious simulator building problem as the distributed systems become more and more complicated and dynamically data driven. Most of the existing simulators are designed and developed to target a specific type of application, lacking the capabilities to be a configurable and standardized tool for researchers. To solve the adaptability and reusability problems of simulators, this paper proposes a new approach to design and implement a configurable real-time digital simulator for hardware devices that are connected via data buses in distributed systems. First, the proposed simulator uses a logic automaton to simulate the activities of a real device, and generates the incentive data for tested equipment according to the predefined XML-based files. Then with a virtual bus, the simulator can receive, handle, and send data in various network environments, improving the flexibility and adaptability of a simulator design. Experimental results show that the proposed simulator has a high real-time performance, and can meet the increasing requirements of modern simulations of distributed systems.

This paper presents an efficient power management, voltage balancing and grid synchronization control strategy to increase the stability and reliability of distributed energy resources (DERs)-based microgrid. The microgrid is composed of Photovoltaic, Double Fed Induction Generator-based wind and diesel generator with critical and non-critical loads. The system model and the control strategy have been developed in Real Time Digital Simulator. The coordination and power management of the DERs in both grid connected and island operation modes is implemented. One distinct challenge of microgrid operation in island mode is the stable control of frequency. A controller is proposed and implemented in the island mode for the diesel generator equipped with the required inertia to maintain the microgrid rated frequency by operating in the isochronous mode. To restore the microgrid back to the utility, the voltage, frequency and phase angle of the islanded microgrid should match with that of the grid network within specified limits to avoid transient instability. Switched capacitor banks are connected at the point of common coupling to balance the voltage for microgrid synchronization. The CIGRE medium voltage test bench system is used to implement the DERs and their controller. The proposed control approach has potential applications for the complete operation of microgrids by properly controlling the power, voltage and frequency in both grid and island modes. The real time digital simulator results verify the effectiveness and superiority of the proposed control scheme in grid connected, island and grid resynchronization scenarios.

In this study, a passive islanding detection technique based on the variation in the angles of superimposed sequence components of voltage and current is proposed. The pre- and post-islanding voltage and current superimposed components are derived using the corresponding voltage and current phasors. The angle between the positive and negative sequence voltage and current and the superimposed components of these quantities are derived to take further action. Furthermore, decisions obtained from the angles of different superimposed components are combined using a voting technique to take the final decision with more reliability and accuracy. The scheme does not require the establishment of any threshold and completely relies on the rule base obtained through a simulation study. A microgrid with multiple connection points is simulated using a real-time digital simulator (RTDS). A hardware-in-the-loop test bench is arranged using a dSPACE DS1104 and RTDS. Numerous test cases are simulated to assess the performance of the proposed technique.

The wide application of power electronic component in power system with renewable energy sources has changed the fault characteristics of conventional power system, resulting in the performance degradation of conventional protection, and even the risk of maloperation and rejection. This brings challenges to the security and stability of the power grid. Therefore, in order to solve these problems, a novel principle of pilot protection based on structural similarity and square error method is proposed. The structural similarity criterion makes use of the difference of fault characteristics between renewable sources and synchronous generators to identify internal faults, while the square error auxiliary criterion is used to solve abnormal calculation of the existing similarity based protection. The detailed model of grid-connected renewable energy power plant is built in Real Time Digital Simulator (RTDS) and the proposed protection algorithm is solidified in the industrial protection device. The effectiveness of the proposed principle is verified by hardware-in-loop dynamic simulation experiments. Compared with conventional differential protection, the proposed protection shows excellent performance in speed and reliability during various faults. In addition, a field short-circuit test is carried out in a real wind farm to verify the effectiveness of the proposed protection scheme. It is proved that this proposed method has the prospect for industrial application.

This study develops an energy management platform for battery-based energy storage (BES) and solar photovoltaic (PV) generation connected at the low-voltage distribution network. The sewage treatment plant of Gujarat International Finance Tec-City located in the Gujarat state is considered as a testbed. The contribution of this case study is twofold: (i) Formulation and lab-scale implementation of an optimal scheduling algorithm to charge/discharge BES while minimising the net energy purchase cost. (ii) Development of a fuzzy logic-based speed control strategy for aeration blower to enhance the process efficiency. A stochastic optimisation problem was formulated as mixed-integer linear programming to achieve the charging and discharging schedules of BES. The simulation study on speed control of aeration blower was carried out to demonstrate the air injection control for optimal dissolved oxygen level in the aeration basin at the testbed. Simulation results of the case study and lab-scale hardware realisation (through real-time digital simulator interfaced with modular hardware) were presented to validate the demand- and supply-side energy management platform.

The performance of salient-pole synchronous generators protection is of great importance for the stability of power systems, as they are present in large hydropower plants, subject to various abnormal operating conditions such as three-phase or two-phase faults, electromechanical disturbances and loss-of-excitation. In this context, this work proposes a testing philosophy of salient-pole synchronous generators, in order to define more accurately the setting of the protections and controls of this asset. Thus, in the developed methodology, the admittance plan (G-B) proves applicable to analyze the coordination between the loss-of-excitation protection and the underexcitation limiter, as an alternative to the power (P-Q) and impedance (R-X) planes, normally employed in literature. In modeling the problem, real data for both the hydrogenerators and the electrical network are used. The simulations were performed in a hardware-in-the loop scheme integrated by a Real Time Digital Simulator and a physical relay. Thus, analyzes are made for situations of stable power swing and partial and total loss-of-excitation. The results are useful to prove, through the monitoring of relevant variables of the hydrogenerators, the feasibility and accuracy of the G-B plane in the coordination between the protection and the control of the synchronous machine.

Standalone DC microgrids (SDCMGs) are emerging as prominent solutions to remote customers. As these SDCMGs mainly depend on renewable energy sources to curb carbon emission, reliability of the system is lessened due to their intermittent nature. The battery could offer a solution to this problem as it is inherently enclosed by DC grid for power balancing, but the purpose may not be served completely due to high capital cost and maintenance. Thus, the diesel generator (DG) becomes a major alternative to overcome this issue because of low investment, high compatibility, and flexibility. However, DG inhibits with cranking delay, sluggish response and low fuel efficiency under frequent switching and variable loading scenarios. To suppress the issues, a new power management strategy (PMS) is developed to ensure proper coordination between different sources, storage devices and loads in SDCMG. In addition to this, an effective control scheme is also proposed to achieve seamless regulation of DC bus voltage even under extreme conditions. In this study, different SDCMG configuration is considered for testing and simulation of system is carried out in real-time digital simulator to prove their viability. A scaled prototype is developed to validate simulation results and authenticate proposed PMS and control scheme.

In view of the complex correlation between Doubly Fed Induction Generator (DFIG) internal components and control links which makes it difficult to locate the oscillating source in the equipment level, a DFIG equipment-level oscillating source locating method based on dynamic energy flow is proposed. Firstly, the energy correlation topology network of DFIG internal components and control links is constructed. On this basis, the analytical expressions of dynamic energy flows of DFIG internal components and control links are derived. And then, through Partial Directional Coherence (PDC) analysis, the values of causality between dynamic energy flows of DFIG internal components and control links are calculated, and the diagram of DFIG internal oscillation transmission causality is depicted. Thus according to the distribution pattern of causality values in the causality diagram, the oscillation transmission route is identified and the oscillating source is located. Finally, simulation tests in Real Time Digital Simulator (RTDS) of IEEE 10-machine 39-bus system verify that, the proposed method can quantitatively describe the intensity of interaction between dynamic energy flows of DFIG internal components and accurately identify the oscillation transmission route and the oscillating source in the equipment level. The proposed method can accurately track the original control link/physical component that causes the system to oscillate. Therefore, this paper will facilitate research on DFIG parameter tuning and oscillation suppression measures for low-frequency oscillation in power system.

This article presents a new approach for classification and localization of voltage sags triggered by symmetrical and unsymmetrical faults in electricity networks. The proposed method utilizes five unique parameters of three-dimensional (3-D) polarization ellipse (PE) obtained from the mapping of three-phase voltage signals in 3-D coordinates. The decision boundaries, which are set by the parametric equations exploiting the five ellipse parameters, namely, elevation, azimuth, tilt angles, semi-major axis, and semi-minor axis, are used to classify the fault-initiated sags. The localization of faults is conducted from the parametric equations demonstrating the variation of ellipse parameters with respect to distance from the fault-location. These parametric equations would be helpful to make decision faster and thereby, eliminate the uncertainty in decision-making process. The applicability of the proposed method is tested and validated using real data measured by DOE/EPRI, the recorded waveforms of IEEE 1159.2 Working Group, and the data extracted from the simulation of faults at several feeders of IEEE 14-bus test system using RSCAD and Real Time Digital Simulator (RTDS) platform.

An artificial neural network (ANN) architecture for real-time estimation of available transfer capability (ATC) has been reported in this study. The real-time data obtained from phasor measurement unit (PMU) is utilised to generate target output (ATC) using the pattern search optimisation-based method. The set of information provided as input to the pattern search-based ATC optimiser along with its output forms the input and target output for ANN training. The input information consists of active and reactive power injected along with voltage and current vectors measured at PMU buses. The ATC optimiser is functional as long as ANN is under training. Once the ANN is trained, it receives input set directly from PMU and produces ATC values. PMU emulation is employed for archiving the PMU data. The proposed method is tested on modified IEEE 24-bus, IEEE 30-bus, and IEEE 118-bus test system. The proposed method has also been implemented on real-time digital simulator.

Fractional Frequency Transmission is a competitive technology for offshore wind power transmission. Modular Multilevel Matrix Converter (M3C) plays a key role in a Fractional Frequency Transmission System (FFTS) as the frequency changer. M3C is broadly considered as the AC–AC converter for the future with its attractive advantages in high voltage and high power applications. Due to the lack of a DC link, electrical quantities at different frequencies from two AC systems couple in M3C, resulting in a complex harmonic condition. Harmonics can lead to stability issues and its analysis is of great importance. This paper focuses on the harmonic analysis of M3C. The arm capacitor voltage ripples and the harmonic currents are analyzed at various frequencies. Major factors influencing the harmonics magnitude are discussed. Analysis is conducted on sub-module capacitance and arm inductance selection. A zero-sequence current mitigation controller for M3C is implemented and tested. It is found that for a FFTS, some current harmonics flow into AC systems even though the system is balanced, while the others circulate within the converter. The theoretical harmonic analysis is verified by simulations in Real Time Digital Simulator (RTDS) of a M3C system where each arm consists of forty sub-modules.

This paper presents a new adaptive technique to restore coordination between recloser and fuse of a distribution network in presence of distributed generations (DGs). The proposed technique is based on the derivation of modification factor (MF) which is defined as the ratio of the preset value of positive sequence impedance seen by a recloser $(Z_{1preset})$ to its calculated value $(Z_{1cal})$ . Based on the value of MF, the recloser fast time–current characteristic is altered. The value of $Z_{1cal}$ is obtained by acquiring samples of currents and voltages at the location of the recloser. Performance of the proposed scheme has been evaluated by modeling IEEE 34-bus network in real time digital simulator (RTDS)/RSCAD environment. At the same time, appropriateness of the proposed scheme has been verified on a practical setup developed in the laboratory. The results obtained from simulations as well as from the laboratory prototype indicate that the proposed scheme is able to restore coordination between recloser and fuse with a high as well as a low penetration of DG. At the end, a comparative analysis of the proposed scheme with the previously published schemes proves its superiority in restoring the recloser–fuse coordination.

During the life span of an instrument transformers (IT), non-catastrophic and typically undetected problems may degrades the overall performance of the instrumentation system. Synchrophasor provides high resolution synchronized data compared to the Supervisory Control and Data Acquisition (SCADA) systems. In the proposed non-intrusive method, time-series Phasor Measurement Units (PMUs) data are processed using three step approach for real time condition monitoring of IT at the control center. Bad data are filtered or flagged using MLE based ensemble method before applying density-based spatial clustering of applications with noise (DBSCAN) to detect clusters, changing over time within each time window. In the third step, a decision logic diagram is developed using additional data and system information to categorize the observed anomalies into different types of malfunction, failure, event or degradation. The proposed method has been validated using IEEE test system modeled in the Real Time Digital Simulator (RTDS) interfaced with industrial hardware PMU device. Detecting equipment failures at an early stage will result in improved system reliability and reduced maintenance cost. Several test cases demonstrate superiority of the proposed method for detecting incipient failures in the IT, and provides early warning mechanism for preventing full blown faults resulting in major impact on the power grid.

With the increasing size and complexity of power systems, it is crucial to have an effective protection system in place to ensure its reliability. One of the important components of the protection system are relays. It is important for a relay to operate dependably and securely so that any fault can be cleared in time to minimize damages to the power network. However, it is important to test a relay in a realistic environment before commissioning it to the network. Testing a relay in the actual network can be expensive with limited fault scenarios. Hence, Hardware-in-the-Loop (HIL) testing is an efficient method to perform closed-loop testing of a relay since numerous fault cases can be simulated to provide a realistic operating environment for the relay under test. This paper sheds light on the HIL testing done for protective relays using a sample distribution system using RTDS. Two SEL-351 relays have been used in this experiment, and proper settings for the relays are calculated for coordination. The paper also describes the procedure of configuring the relay and other RTDS components crucial for interfacing of the relay with RTDS. After test setup, a pre-fault, fault, and post-fault analysis was done for the system. The results obtained from these analyses are cross-checked with the event history of the two SEL-351 relays, obtained with AcSELerator Quickset software. This paper provides thorough information for researchers to replicate the presented study or to develop new HIL experiments. It can also help in developing a fundamental understanding of the HIL testing setup that can be further applied to a more complex power system.

This paper presents a platform for conducting Power-hardware-in-the-loop (PHIL) testing of an electric vehicle (EV) motor controller implementing field oriented control (FOC). A fast-switching power-electronics-based amplifier is used to achieve the required transient response speeds necessary for emulating a three phase AC motor with a high fundamental frequency. A field programmable gate array (FPGA) is used to implement the bidirectional high-speed fibre-optic interface, communicating signals between the physical system and a real time digital simulator (RTDS) platform. This allows for a 1 microsecond simulation timestep and a total delay less than 4 microseconds. Using RTDS allows for the simulation to be developed through a traditional circuit simulator interface, rather than requiring a specialized simulation developed to run on an FPGA. Separately from the power amplifier, a resolver emulator system has been developed, allowing for all sensing systems of an EV motor controller to be validated before connecting a physical motor.

Connecting multiple microgrids to form interconnected microgrids can improve power distribution systems resiliency and reliability. However, there is uncertainty of balanced power sharing among multiple microgrids while interconnecting the microgrids. To address this issue, in this paper an intelligent module for interconnecting multiple microgrids with self-healing capability is developed by considering the power mismatch between distributed energy sources generation capacity and load demand of all the microgrids. The advantage of the proposed module is its circuitry is simple, flexible and real-time implementation is easy. To validate the performance of the interconnecting module, two microgrid testbeds are considered in this study and real time simulations are carried using real time digital simulator. The results obtained have ensured the efficacy of the developed intelligent interconnecting module.

Introduction: the frequency and capacity control, as well as the maintenance of electric energy systems rely on the choice of the items of equipment that comprise a particular electric energy system. Generators are the core items of equipment comprising traditional electricity systems, while in off-grid electricity systems this function is assumed by the power-driven converter equipment coupled with energy accumulation systems. The main problem of these systems consists in a fast response generated by the power-driven converter equipment to the changing environment. Excessively fast responses, given by the controllers, make the whole off-grid electricity system unstable.Methods: the resolution of the problem of an unstable off-grid electricity system requires the use of algorithms for the control over inverters and frequency converters, designed according to the principle of a virtual synchronous machine that applies voltage and frequency droops. The model of an electricity system has been produced. It has six key elements: a basic balancing inverter, two generators, lithium-oil battery simulation, an interface converter and a real time digital simulator (RTDS). The model was used to perform an experiment to implement two-way data transmission from RTDS to converting facilities and to verify the performance capability of the algorithm and the electricity system as a whole.Results and discussion: as a result of this experiment, the contact was made between RTDS, Generator 1, Generator 2 and the basic balancing inverter through interface converters. This electricity system is resilient and failure-free.Conclusion: data communication was organized between the real time module of digital simulation and Generator 2. Control commands were delivered from the digital simulation module through interface converters, and their execution monitoring was used as a feedback. The operation of grid-forming and grid-filling converters of a self-contained electricity system was stand tested at the MIPT Centre for Engineering, and optimization algorithm performance results were obtained in respect of a battery used in the course of the application of virtual synchronous machines.

The large-scale penetration of intermittent Renewable Energy (RE) sources such as wind and solar power generation may cause a problem of frequency aberration of interconnected Hybrid Power System (HPS). This occurs when the load frequency control of interconnected system is unable to compensate the power balance between generation and load demand. Also owing to the enhancement of future transport, the Plug-in Electric Vehicle (PEV) plays a significant role to customer at demand side. Thus, the PEV can act as a power control to compensate the power balance in Renewable Energy integrated power system. This paper presents a physics inspired Atom Search Optimization (ASO) algorithm for tuning the parameters of Fractional Order Proportional-Integral-Derivative (FOPID) controller for Automatic Load Frequency control of HPS. In this proposed work, an attempt has been made to analyze the frequency stability of HPS using Matignon's theorem. The interconnected HPS consists of reheat thermal power system, RE sources such as wind and solar thermal power generation associated with energy storage devices namely aqua electrolyzer, fuel cell and electric vehicle. The gain and fractional terms of the controller were obtained by minimizing the Integral Time Absolute Error of interconnected system. The robustness of ASO-tuned FOPID controller is tested on two-area HPS that was modelled using MATLAB/Simulink. The results obtained were then compared with other fractional order and classical integer order controllers. From the simulation results, it is inferred that the proposed ASO-tuned FOPID controller gives superior transient and steady-state response compared with other controllers. Moreover, the self-adaptiveness and robustness of the controller was validated to account for the change in RE power generations and system parameters. Furthermore, the effectiveness of the method is proved by comparing its performance with the recent literature works. The real-time applicability of proffered controller is validated in hardware-in-the-loop simulation using Real Time Digital Simulator.

In the conventional distribution network mostly overcurrent (OCR) relays are in use, however, in case of microgrid the direction of power changes with operating conditions, the need of directional ...

Modular multilevel converters (MMCs) are a realistic alternative to the conventional voltage source converters for medium-voltage (MV) and high-voltage direct current (HVdc) applications. The number of submodules (SMs) per arm of the MMC can be as high as 512 to achieve desired high dc voltage levels required for HVdc with a very low total harmonic distortion (THD) (e.g.

This study proposes a synchrophasor measurement-based approach for online available transfer capability (ATC) evaluation. It utilises an expression which correlates the nodal power injections to the line flows. A new set of measurement-dependent injection distribution factors (MDIDFs) has been computed using this expression. The measurements, obtained from optimally placed phasor measurement units, are used to carry out linear state estimation (LSE). The voltage phasors of all system buses, obtained by LSE, are required to compute the MDIDFs. ATCs for bilateral and multilateral transactions are directly evaluated using these MDIDFs for system intact and N − 1 contingency cases. If required, the MDIDFs can also be used to directly compute AC power transfer distribution factors and line outage distribution factors without factorising the Jacobian of AC power flow (ACPF). The proposed approach has been validated in real-time digital simulator at different system operating points of WSCC 9-bus and IEEE 14-bus systems. Simulations are also performed on an Indian 246-bus Northern Regional Power Grid system to demonstrate the effectiveness of the proposed approach. The results thus obtained, when compared with those evaluated through repeated ACPF-based approach, prove the efficacy of the proposed approach.

This study describes a novel Islanding detection technique based on a discrimination factor (DF) which is derived from an auto-correlation factor (ACF) of the voltage signals acquired from the terminal of the distributed generator. The value of DF is calculated from the most affected lags of the ACF during various Islanding and non-Islanding conditions. Further, the validation of the presented scheme has been carried out by developing a hardware-in-loop laboratory setup. In this setup, a power distribution network has been modelled on a real-time digital simulator (RTDS/RSCAD) which is physically connected to the digital signal processor controller. Various non-Islanding and Islanding test scenarios have been generated. The proposed ACF-based technique is able to differentiate Islanding state with non-Islanding states even for perfect power equilibrium situation. The proposed approach can determine the Islanding state in a period of three cycles from the inception of Islanding. Finally, a relative assessment of the above algorithm with other existing methods shows its supremacy in terms of better stability during critical non-Islanding situations and lower non-detection zone in case of Islanding states.

In South Korea, a 154-kV single-phase superconducting fault current limiter (SFCL) system was developed and installed at the Gochang power test center of Korea Electric Power Corporation in 2016. Korea Electrotechnology Research Institute proposed a novel protection algorithm for the application of 154-kV SFCLs to a real power system and designed a protection scheme of the Gochang power test center. This paper verified the protection scheme using the hardware in the loop testing that a commercial protective relay system with the novel algorithm is tested by real time digital simulator.

This paper presents the testing of power transformer differential relay in a hardware-in-the loop using a Real Time Digital Simulator (RTDS) and Digital Signal Processor (DSP) for all possi...

This paper proposes the implementation of a multi-functional inverter, which was simulated with three ancillary functions. The first function is a Shunt Active Power Filter (SAPF) for harmonic content mitigation, the second is a Virtual Synchronous Machine (VSM) to show the effective regulation of voltage and frequency, and finally, power management in AC microgrids. The multi-functional converter is responsible for the integration of a PV-Battery system (distributed generation) on the AC grid. Furthermore, Real Time Digital Simulator (RTDS) and dSPACE have been used to analyze the performance and control of such multi-functional inverter when added to an AC microgrid. Results demonstrate the operation of the system and can be used as validation of the proposed control strategies through a Hardware In the Loop (HIL) simulation.

The parameter optimisation of designed controllers for power systems is always a big concern and needs a lot of effort of researchers especially when the electricity grid becomes larger and more complex. This study proposes a control parameterisation using genetic algorithms (GAs) for power oscillation damping (POD) incorporating synchronous condensers (SCs) via software-in-the-loop simulation to enhance the damping and frequency stability for low-inertia systems. A closed-loop interfaced setup among real-time digital simulator, MATLAB, and OLE for process communication running in real time is analysed and implemented to optimise the POD parameters of a SC. Furthermore, a Prony technique based on the system measurement is applied to find out the frequency and damping ratio of the dominant oscillation mode. The POD optimal parameters are determined by the GA objective function that maximises the damping ratio of the dominant oscillation mode. The effectiveness of the proposed method in damping power oscillations and frequency stability improvement is verified through simulation results of the future western Danish power system. Simulation results demonstrate that the proposed approach offers good performance for parameter optimisation of the POD.

Use of Battery in standalone system can offer number of benefits in terms of energy management, reduction of dependency on fossil source and voltage regulation. In this study, a power management technique considering conservation voltage reduction (CVR) along with droop control method is proposed for a standalone system supplied from Photovoltaic (PV) source and battery. The proposed power management scheme ensures that under all operating conditions, the battery is neither overcharged nor completely discharged. It further ensures that under no condition, the power limit of battery charging as well as battery discharging controller is exceeded. The proposed method also aims to minimize the size of overall Photovoltaic battery (PVB) system to reduce the total investment and operation cost considering energy saved achieved by CVR, while satisfying system operational constraints. The proposed method also reduces the number of charging/discharging operations of battery to enhance its life. The validity of the proposed power management scheme has been extensively tested on a European distribution system through PSCAD/EMTDC simulation studies as well as on real time digital simulator (RTDS). The simulation results indicate that the combination of CVR and Droop control can achieve appreciable energy savings.

This paper presents a protection scheme for cross-country faults and transforming faults in a dual-circuit transmission line of 400-kV Indian transmission network of Chhattisgarh state. An intelligent relaying scheme is designed for fault detection and classification of cross-country faults and transforming faults in a mutually coupled dual-circuit transmission line. The proposed scheme is a hybrid framework of discrete wavelet transform and artificial neural network (DWT–ANN) which is used to detect the fault, distinguish the faulty phase(s), and identify the type of fault in a dual-circuit transmission line. The cross-country faults and transforming faults are difficult to detect by the conventional scheme because the first involves faults at two different locations and the latter involves a change in the type of fault after a few cycles. A practical 400-kV power transmission network of Chhattisgarh state has been modeled and simulated in real-time digital simulator (RTDS) environment to reproduce real-time fault events and further analysis is carried out in MATLAB software. To examine the efficacy of the proposed protection scheme, a wide range of case studies have been done thereby varying different fault parameters, power system operating parameters, and typical fault scenarios. The results described that the proposed protection scheme based on the DWT–ANN algorithm is reliable and extremely responsive to various types of cross-country and transforming faults which are more complex in nature. The distinct advantage of the proposed protection scheme is that it accurately detects all types of cross-country faults and transforming faults in a dual-circuit transmission line by employing single-end data only.

Consolidated schemes and philosophies have been developed for Wind Energy Conversion Systems (WECS) protection. Although various studies have addressed this topic, including the internal protection function, there is still room for improvement, for instance, concerning the use of differential logic under varying frequencies. An aggravating factor related to protection issues is the high penetration of electronic devices in recent topologies, which may result in different responses in the case of internal faults, depending on the control strategy. In this scenario, conventional protection may not work properly. Based on this and considering the increasing tendency towards using full-converter WECS, there is a need to standardize them as well as improve their protection schemes. Thus, this paper analyses the application of the differential function in order to detect internal faults in a full-converter wind turbine generator. A differential protection scheme based on Discrete Fourier Transform (DFT) using dynamic window was discussed in this paper. The main objective was to reduce the phasor estimation error caused by the stator frequency variation. A complete protection scheme was implemented and tested using fault simulations from a Real Time Digital Simulator (RTDS). Very promising results were obtained. Furthermore, it was demonstrated throughout the paper that the grounding configuration greatly influences the protection performance of such equipment.

A new internal fault detection and classification technique for the synchronous generators is presented. First, the presence of an abnormal/fault condition is detected based on the negative sequence component (NSC) of neutral end current. Thereafter, the internal fault and abnormal/external-fault conditions are discriminated by utilizing the instantaneous phase angle between the NSCs of the terminal voltage and current. Subsequently, the internal fault is classified based on phase angle between NSCs of terminal voltage and neutral end current along with the zero sequence component of the neutral end current. Efficacy of the proposed scheme has been verified on a phase domain synchronous machine model developed on the real time digital simulator (RTDS). The results derived from various fault datasets show that the proposed technique is able to effectively distinguish between internal and external faults including special cases, such as current transformer saturation, overloading, and unbalance condition. Further, it provides added capability of detecting and identifying inter-turn faults irrespective of the winding configuration of the generator. Comparative assessment of the proposed scheme in terms of detection time and incorporation of different types of faults with the existing techniques proves its superiority.

The maximum energy that can be harvested from a photovoltaic (PV) system at any instant depends on the effectiveness and response time of the maximum power point tracking (MPPT) algorithm used and related controllers. To facilitate proper controller design, a precise mathematical model of the system is required. This paper presents a comprehensive small signal model capable of describing the dynamics of the power stage and controllers. The power stage consists of a PV system and a dc–dc boost converter including the parasitic elements operating in inverse-buck mode. The MPPT and PV voltage controller constitute the control system. The steady state and transient responses of the system are evaluated by controller-hardware-in-the-loop approach where the power stage is simulated in a real time digital simulator and the control operations are performed in a digital signal processor. The frequency response is experimentally determined using a Gain-Phase analyzer. This unique approach allows control system designers to test and validate a control system design before implementing it with a laboratory scale hardware or any real-life application. This method adds an extra layer of design authentication on top of conventional offline simulations.

This study describes the hardware implementation of a fast adaptive single-phase auto reclosing algorithm based on voltage harmonic content measurement. The proposed algorithm classifies the fault type, preventing reclosing onto permanent fault, and identifies the arc extinction instant, adjusting dead-time to implement reclosing with granted success. The hardware was connected to the Real Time Digital Simulator (RTDS) to perform tests in hardware-in-the-loop (HIL) with a protective relay. The studied system is based on a 500 kV transmission line of the Brazilian electrical power system and eventually real case oscillograms were tested. The algorithm performance was validated with previous software development. However, in the present document we highlight the importance to implement hardware test, as operational limits can only be identified in this last testing stage. Robustness of proposed algorithm based on low-order voltage harmonic content was proved with oscillograms’ tests.

Modular multilevel converter (MMC) has been widely used in HVDC transmission projects because of its large- scale and cascaded topology. However, there are many problems in the control of internal circulating current and sub module capacitor voltage. As an effective method to solve the control problem of uncertain nonlinear systems, Active Disturbances Rejection Controller (ADRC) has been widely studied. Based on the existing control system, this paper introduces the idea of active disturbance rejection control, and designs a controller with faster response speed and stronger robustness, instead of the energy outer loop controller. Furthermore, PI + LESO controller is proposed to replace part of PI controller, and the control results are compared and analyzed. Real Time Digital Simulator (RTDS) is used to simulate the proposed control system. The results verify the correctness of the theoretical analysis and the effectiveness of the proposed method.

In a practical ±500 kV/3000 MW line commutated converter based high voltage DC (LCC-HVDC) transmission system, a sustained 5.5/105.5 Hz harmonic was observed in the voltage of the AC bus of inverter station. HVDC power limit function was triggered because of the action of AC filter resistance harmonic overload protection caused by the harmonic. To study the phenomenon, the real-time digital and physical closed-loop simulation platform based on real time digital simulator (RTDS) is first built and the harmonic instability phenomenon is reproduced. Then, its mechanism and impact factors are analyzed based on real-time simulation. Analyses results show that series resonance and core saturation are the main reasons of harmonic. AC/DC harmonic transfer characteristic through converter leads to the interaction of AC and DC network, and inappropriate AC/DC impedance results in the sustained harmonic. Bypassing the series capacitor is proposed as a temporary countermeasure and verified by on-site test. To solve the problem thoroughly, supplementary harmonic controller (SHDC) based on STATCOM is designed, whose validity is verified by simulation tests.

Since increasing renewable sources are integrated to power system, dynamic behavior of power system turns complicated. This paper proposes a detailed direct-driven wind permanent magnet synchronous generator (D-PMSG) connected to power system simulation structure that combines Real Time Digital Simulator (RTDS) and an additional control device in LabVIEW using discretization to implement the control hardware-in-the-loop (CHIL) simulation. Feasibility demonstration of RTDS model using large-and-small time step are demonstrated in real time simulation. Control effect optimization of damping method is conducted based on case studies in CHIL testing.

This paper proposes a novel scheme to protect a Wind Generator (WG) with Energy Storage Systems (ESSs). In the scheme, data are dealt with in an iterative way to obtain the relay coordination considering both generator operating modes: grid connected and island. The proposition relies on conventional protection functions adapted to the operational system requirements. A set of well-known protection functions (under-voltage, over-current, differential and unbalance) operating together in an innovative arrangement, was the main objective of this research. In order to validate the proposed scheme, a Wind Energy Conversion System (WECS) with a Vanadium Redox Flow Battery (VRFB) as an EES was implemented in a real time digital simulator (RTDS®) to perform hardware-in-the-loop simulations. The simulation system consisted of a Wind Generator with grounded stator connected to the system through a DC link in order to investigate its behavior subjected to internal and external faults. Very promising results considering the proposed scheme are presented.

Voltage instability detection in good time has become highly demanded in the recent power system operations. This work is a step towards the voltage instability detection using the reactive power loss-based voltage instability detection index SQLVIDI proposed by the authors. This index is validated under real time for Western System Coordinating Council (WSCC 9) bus test system by considering all the dynamic components responsible for voltage instability using real-time digital simulator (RTDS). The proposed index is also compared with synchrophasor technology-based voltage instability monitoring index VIMI in real time. The RTDS results show that the index SQLVIDI is fast in detecting the voltage instability and can be used to monitor voltage stability in real-time power system applications.

With the increased penetration of power electronics based distributed energy resources (DERs), its control and automation in traditional grid gives rise to more complex operation of power system. It is difficult to realize such a multidisciplinary power system using a single real-time simulator. Co-simulation is a versatile technique to split the large system models into multiple subsystems and components. In case of limited capability of a single simulator, these components can be modeled in more than one simulators and can be solved in parallel. The technique is also useful to interconnect simulators of different make which utilizes propriety software tools. In this paper, a co-simulation based testbed is developed, which can facilitate a platform for validation of various power engineering algorithms. Two different make of real time simulators, Typhoon Hardware-In-Loop (HIL) and Real Time Digital Simulator (RTDS) have been interfaced using peer-to-peer and VILLASnode based UDP/IP socket communication. In this work, an Ideal Transformer model (ITM) based approach is utilized to couple the simulators where the information is exchanged using the dynamic phasors. An illustrative testbed of CIGRE low voltage distribution system is developed using both types of communication methods and the results are compared in terms of latency, jitter and round trip time. In addition, the effects of packet loss, data corruption and duplication on system transient are also presented in this paper. The results demonstrate the capability of the testbed to evaluate the controllers for microgrid, DERs and protective devices in the distribution network at different levels of deployment.

This paper proposes a simple framework for the detection of statistically crafted cyber-attacks, viz., random attacks, denial of service (DoS) attacks, False data injection(FDI) attacks, etc., in smart grids. A new cyber attack detector (CAD) is devised for this purpose which, in turn, is based on two statistical coefficients. The efficacy of the proposed framework is demonstrated on Real Time Digital Simulator (RTDS), along with its comparative assessments with another detector under various different attack scenarios.

When the grid voltage is unbalanced, the lifetime of the drive train is reduced because of the squirrel cage induction generator (SCIG) torque oscillations with double grid frequency. In this paper, the coordinated control strategy of a hybrid energy storage system (HESS) is designed, including the positive-and negative-sequence voltage coordinated control strategy of DC/AC converter, the control strategy of the lithium battery and supercapacitor. The objective of the positive-sequence voltage control strategy is to maintain the voltage of the point of common coupling (PCC) at the rated value, while the objective of the negative-sequence voltage control strategy is to control the negative-sequence voltage to zero. Therefore, the control strategy can eliminate the generator electromagnetic torque oscillations. The control strategies of the lithium battery and supercapacitor in an HESS are designed as well. A lithium battery is employed to stabilize the DC voltage of the DC/AC converter and a supercapacitor is used to absorb power fluctuations on the DC side of the inverter. Finally, the correctness and effectiveness of the control strategy are verified by the simulation work in the real time digital simulator (RTDS).

Power system transient simulation is an important approach to study the system's dynamic behaviors and guide its daily operation schedule. It can be classified into the following two categories based on the different scales of time step: electromagnetic transient (EMT) simulation and transient stability analysis (TSA). EMT has time step in microseconds, uses instantaneous value of electrical variables, and studies the transient phenomena caused by the interaction between electrical and magnetic fields. EMT is able to present the detailed switch process of power electronic devices in HVDC, achieving very accurate simulation. However, generally it is not suitable for large-scale system simulation because of its large computational burden due to complicated model and small time step. EMT is commonly used in detailed study of HVDC system in a relatively small scale. Currently there are several commercial EMT tools, such as PSCAD/EMTDC, EMTP, MATLAB®/Simulink®, Real Time Digital Simulator (RTDS), HYPERSIM, and RT-LAB. Particularly, some EMT tools can achieve the so-called real-time simulation, such as RTDS, by parallel computation hardware. This capacity makes it possible to connect real control/protect devices via power amplifiers, implementing hardware in loop simulation, which is quite valuable for in-factory tests.