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There are many effective techniques for virtual inertia emulation in DC microgrids that can help DC bus voltage stability through power exchange with virtual inertia injection. But one of the vexingly complicated challenges in virtual inertia emulation is the connection of unbalanced loads on the AC side of a DC microgrid. Unbalanced AC loads connected to a DC microgrid may cause severe fluctuations in DC bus voltage and battery power, as well as distorting AC side voltage. The need to solve this issue is very important because it can be a threat to the microgrid DC bus voltage stability and feed sensitive loads. One effective method to mimic the real inertia feature and dampen the unfavourable unbalanced conditions is to employ a virtual synchronous generator (VSG) equipped with a decoupled double synchronous reference frame (DDSRF) approach. The DDSRF can extract positive and negative components with high precision and create pure DC signals for the control system to improve accuracy and controllability. Hence, this paper investigates a combination of a VSG structure enhanced with a DDSRF technique to attenuate the fluctuations of DC bus voltage, battery power, and AC-side voltage caused by an unbalanced AC load in an islanded DC microgrid. The simulation results confirm that the unbalanced loads connected to the AC side of the microgrid are destructive for DC bus voltage, battery power, and also create voltage imbalances for AC loads. Furthermore, the proposed DDSRF-based VSG control system that has been implemented on the AC side of the microgrid can strongly dampen the fluctuations on the DC bus, battery, and AC loads. [ABSTRACT FROM AUTHOR]

Recently, owing to the high penetration of renewable power generations, random access to dynamical loads and wide application of power-electronic devices, the modern power systems exhibit new features such as high dynamics, low inertia and weak voltage and frequency support. As a powerful tool in revealing the dynamical evolution of the modern power systems, the dynamic state estimation (DSE) scheme gains a surge of research enthusiasms. Note that in actual power systems, various styles of power generations and mixed measurements generated by the supervisory control and data acquisition (SCADA) system and the phasor measurement unit (PMU) pose higher demands on the DSE. In addition, the measurements with anomalies such as gross errors, outliers and incomplete information are often encountered due to the unreliable measurement facilities, constrained communication resources and cyber-threats. Such anomalies, if not tactfully handled, would largely impair the DSE performance. In this paper, a systematic and timely review with respect to DSE for power systems is provided. First, several typical models for power systems include quasi-steady model, synchronous-generator-based multi-machine model and renewable power generation model are introduced. Then the measurement facilities of power systems and their features as well as the measurements with anomalies are reviewed, respectively. Subsequently, the DSE schemes are recalled and discussed from the perspectives of framework, methodology, anomaly-resistant ability and application, respectively. Finally, some possible future research topics are outlined for the DSE of power systems. [ABSTRACT FROM AUTHOR]

Recently, the transition from conventional to renewable energy sources (RESs), from internal combustion engine vehicles to electric vehicles (EVs), and from the main grid to microgrids (MGs) are essential goals to both reduce greenhouse gas emissions and ensure the stability of power systems. However, the transitions cause new concerns in the grid including technical challenges and financial viability. This study examines the RES-based MG under realistic conditions considering the uncertainty in fleet size of EVs, emergency generator capacity, solar irradiation, and wind speed in island mode. The work aims to provide effective solutions including conventional methods alongside today's trend namely doubly fed electrical generators (DFIG), vehicle-to-grid mechanism (V2G), maximum power point tracking controller (MPPT), voltage source inverter (VSI) with high switching frequency for technical challenges, and virtual synchronous generator (VSG) mechanism for financial viability. The paper provides a guide for resizing the emergency generators capacity depending on system instability. The observations verify that the control mechanisms reinforce the system to remain stable by decreasing the range of frequency fluctuation from 3.1 to <0.05 Hz, the peak point of frequency from 51.8 to 50.05 Hz, and the emergency generator capacity from 0.7605 to 0.3420 MVAr at MATLAB and Simulink. [ABSTRACT FROM AUTHOR]

This study aims to solve the problem of optimal performance parameter selection of the virtual synchronous generator (VSG) control strategy using an improved artificial jellyfish search (IMJS) algorithm. VSG technology helps the inverter to improve the anti-disturbance ability. The VSG control effect depends on the setting of its performance parameter values. The population initialization strategy and dynamic adaptive factor are used to improve the optimization ability of the artificial jellyfish search algorithm. The IMJS algorithm is used to optimize the VSG, and a control strategy for the VSG based on the IMJS (IMJS-VSG) is proposed to improve the control capability. The results show that the active power achieves smooth changes without oscillations under the IMJS-VSG control strategy when the system is running in grid-connected operation. The system voltage drop under the IMJS-VSG strategy is less than 40% of the VSG strategy when the system is in an islanded operation state. [ABSTRACT FROM AUTHOR]

The virtual synchronous machine (VSM) concept is emerging as a flexible approach for controlling power electronic converters in grid-connected and standalone applications. In this study, we have used the mathematical model of a Virtual machine with a virtual exciter and governor for the standalone inverter to optimize the parameter for small-signal stability. Firstly, the small-signal models of virtual synchronous generator with load have developed, and subsequently, the system eigenvalues were obtained by solving the state Jacobian matrix. Next, the sensitivity of the eigenvalue location on controller parameters has been studied. The parameters are optimized on the basis of the location of dominant eigenvalues using a genetic algorithm. Finally, the optimal controller parameters are used to test the system's dynamics by solving the model equations with Ordinary Differential Equation (ODE) solver. Moreover, our conclusions were also tested using the actual switching devices on Matlab/Simulink. The results indicate that the frequency stability can be enhanced drastically by optimizing a wide range of VSM parameters. The frequency stability sensitivity with respect to load variation has been improved. The transient settling time of system response for optimized values is 0.25 sec which is only 5% of that for general values. The results of this work are relevant for the VSM-based microgrid small-signal stability analysis. [ABSTRACT FROM AUTHOR]

The dwindling inertia of the power system due to the incorporation of renewable energy sources is a vital concern. This is the genesis of the frequency volatility in a system. A non-linear controller formulated on fuzzy logic has been developed for mimicking the operation of a synchronous generator. This non-linear controller is proficient in utilizing the energy present in the rotating blades of the wind turbine and nourishing the requisite quantity of inertia in the system ensuring the alleviation of the frequency variation issues. The system's improved behavior is evaluated with this innovative controller in comparison with a traditional PD/PID controller for various transients such as sudden addition, deletion of large loads, and faults. [ABSTRACT FROM AUTHOR]

This paper proposes a damping torque index (DTI) to determine the optimal installation location of the power system stabilizer (PSS) in the multi-machine power network. The proposed index is based on the classical damping torque analysis (CDTA) method for power system low-frequency electro-mechanical (LFEO) analysis. The selection criteria of the PSS location is the maximum magnitude of DTI under normal operating conditions. The CDTA method is used to design PSS, and the phase compensation technique subsequently adjusts the associated parameters. Furthermore, to analyze the power system's critical oscillation mode, a wide-area damping controller (WADC) is design for the synchronous generator where optimal location of PSS is install. The reduced-order model-based WADC includes time-varying delay in the wide-area signal. The WADC's input signals from the phasor measurement unit (PMU) and the location of the PMU are selected using geometric measures of observability and WADC parameters design based on the residue approach. The proposed approach is validated in two separate test systems, and modal analysis is carried out on MATLAB software. The simulated results have been validated on the real-time digital simulator (RTDS) RSCAD 5.012. Results obtained on RTDS show that the proposed approach efficiently damps low-frequency electro-mechanical oscillations. [ABSTRACT FROM AUTHOR]

A hybrid microgrid is an efficient technique to integrate renewable energy resources and allow energy exchange between ac and dc subgrids. Pf and QV droop controls are commonly employed in microgrid to deliver power demands while preserving voltage and frequency restrictions via interlinking converter (IC). When a microgrid is powered by renewable energy sources, due to the prevalence of impedance conflict traditional droop techniques offer an inappropriate response in power sharing. This study employs a predictive-based control scheme to ensure appropriate power sharing between both subgrids in the event of imbalancing on either side. Photovoltaic systems, battery storage, and a synchronous generator powered by wind turbines constitute a microgrid, which is connected via an interlinking converter. The MPC MPPT-based control approach dynamically dispatches power generated by wind and solar energy sources to the loads connected throughout the hybrid microgrid. The proposed control technique maintains power exchange between hybrid microgrids within an acceptable range, according to simulation and experimental results. [ABSTRACT FROM AUTHOR]

A model of a bistable speed bump vibration energy harvester (BSVEH) is designed by combining the buckling beam, rack and pinion, one-way clutch and speed bump with rotor alternator. One-way clutches are used to ensure the input shaft of rotor alternator to rotate unidirectionally during the up-and-down vibration of the speed bump. The coupled mechanical model of the speed bump energy harvester is established to study the power generation performance subjected to various structural parameters, that is, types of speed bump, types of vehicles, geometrical parameters of the buckling beam, speed increasing ratio and moment of inertia. Simulations show that the output power of the BSVEH (such as 148 J in 1 second) is larger than that of the speed bump energy harvester with linear spring (86 J in 1 second). Compared with the vehicle passing over speed bump energy harvester with linear spring, the vertical and pitch accelerations of a vehicle are decreased 9.3% and 16.5%, respectively when it passes over the BSVEH. Riding quality is also improved. The effect laws of the type and speed of the vehicle speed on the output power of the BSVEH are obtained. The maximum output power of SBVEH is 14.8 W at the vehicle speed 24 km/h. The maximum energy-efficiency of the BSVEH can reach 43.9%. And the maximum average electrical power can arrive at 12.7 W. The optimal parameters favoring the output power of BSVEH are determined. The advantages of power generation and riding quality, correctness of mechanical models and effectiveness of BSVEH are verified by simulation results. [ABSTRACT FROM AUTHOR]

The creation of optimization methods is relatively common and popular today for solving issues in engineering areas. In this paper, a new wild horse optimizer (WHO) method is adopted to design an optimal controller for a permanent-magnet synchronous generator (PMSG)-based wind turbine system (WTS). A control method consisting of two current control loops of the optimized controller is proposed for the control of the machine-side converter. The dynamic performance of PMSG can be improved during the different normal and abnormal conditions through effective tuning of the PI controller gains which enhances the overall response of the system parameters. This enhancement consequently results in the realization of the maximal power tracking during wind speed changes and the fault ride-through capability during faults and large-signal events. Furthermore, the power fluctuations due to the incoming wind speed variants can be smoothed by using the suggested controller. In addition, the proposed controller system employs an optimal torque control method and braking chopper system to help in achieving such tasks. MATLAB simulations of a 1.5 MW PMSG-WTS have been carried out and compared with the Ziegler Nichols-based PI controller in order to validate the feasibility and efficacy of the proposed controller. [ABSTRACT FROM AUTHOR]

Generators that have been used in direct-drive wind turbines could be produced with a permanent magnet between the power ranges of 1 kW to 1 MW. The cogging torque is the most significant problem of these generators. In this study, the pole grouping method is suggested to reduce the cogging torque of an axial flux permanent magnet (AFPM) synchronous generator with open slotted. The suggested method includes magnetic analyzes and experimental results of the 14-pole open slotted AFPM generator rotor poles that grouped as 7-7, 4-3-4-3, 3-2-2-3-2-2 and named A, B, C, respectively. Besides obtaining the cogging torque (Tc) data, the most considerable part of the study is to get total harmonic distortion (THDV) and output power (Pout) data in which show the electrical performance of the generator for different grouping angles. The optimum ranges for an AFPM generator were determined as 80% reduction for Tc, 15% reduction for Pout, and below 3% for THDV. The optimum grouping angles for A, B, and C were obtained by experimental studies as 32°, 32°, and 30°, respectively. Experimental results and the magnetic analysis have been shown that optimum values are obtained when the ratio of the pole angle to the grouping angle is α r = 0.75. [ABSTRACT FROM AUTHOR]

Faults in the power system should be detected as soon as possible. Otherwise, some defects in the protection system can result in imposing considerable destructive damage to the system equipment. The excitation system of a synchronous generator plays a significant role in the proper operation and control of the generator. Loss-of-excitation (LOE) may cause harmful effects on both the generator and power system. If LOE is not correctly detected, an unnecessary trip signal may be issued, resulting in the overloading of parallel generators and even a system blackout. Conventional techniques for detecting this fault are based on impedance measurement. Despite the simple structure of these techniques, they are sometimes unable to detect some faults correctly. The presence of flexible alternating current transmission system devices can significantly affect the impedance characteristic of the system and as a result, the operation of impedance relays. In this article, first, LOE and other bugs causing failures and errors in the protection of LOE are simulated in the presence and absence of a unified power flow compensator (UPFC), and parameters with different behavior are determined. Then, the most sensitive parameters are sorted using an intelligent method based on their sensitivity. Once the sort order table is obtained, the first two parameters are applied to a ground data handling neural network method, and LOE is detected. The simulation results show that the proposed algorithm is significantly reliable in detecting LOE faults. Moreover, LOE is detected very quickly in the presence or absence of the UPFC in the system by preventing the tolerance of electrical and mechanical stresses by the machine and system; thus, the maloperation of the protection system is avoided. [ABSTRACT FROM AUTHOR]

Owing to the rapid incorporation of doubly fed induction generator (DFIG)-based wind farms into the power system, the sustainability of the power system has been a major concern of system planners, operators, engineers, etc. This has necessitated a proper investigation to be implemented in the stability of the power system. The small-signal stability analysis can be used to predict the dynamic behaviour of the power system and the sustainability of energy with the application of DFIGs. The state-of-the-art of DFIG, its impacts on small signal stability and the potential effects are proposed in this paper. The control techniques on DFIG to enhance damping qualities of the power system are also presented. This paper reviews the small-signal stability analysis of wind power system integrated with DFIG-based wind farms. The developments that have been made till-date towards attaining models of DFIG-based wind farms will give a definitive conclusion about small-signal stability. The prediction methods and impacts of integrating DFIG-based wind power into the power system are reported together with their limiting factors. Lastly, the techniques that have been presented in the paper will improve the small-signal stability and guarantee the future sustainability of power supply. [ABSTRACT FROM AUTHOR]

By figuring out the best numbers for the inductor, capacitor, and duty cycle of the boost converter, this method makes it possible to match the PV system to the configuration of the DC/AC converter. The suggested numerical antenna model shows good agreement with the performance of the built antenna prototype within the human muscle-mimicking liquid phantom. This paper "Multi -objective Naked Mole -Rat Algorithm for UWB Antenna Design", introduces a novel multi-objective naked mole-rat (MONMR) algorithm for the optimization of two printed monopole patch antenna structures for ultrawideband (UWB) applications. In "Improved Switched-Capacitor Switched-Inductor Z-source Inverter for Increasing Boost Factor and Decreasing Voltage Capacitors Stress", the authors uses a switched-inductor Z-source inverter to improve a switched-capacitor inductor ZSI. [Extracted from the article]

The loss of excitation (LOE) is a very common fault in synchronous machine operations and can be caused by a short circuit in the field winding, unexpected operation of the field breaker. Several methods are proposed to detect LOE, but most of them are impedance-based. It is possible that these methods will not be able to identify between LOE and stable power swing (SPS). In this paper, a new method for LOE fault detection is presented, which is designed based on the derivative of the terminal voltage and the derivative power angle of the synchronous generator. According to the proposed idea, complete simulation studies have been performed by considering different fault modes in the synchronous generator and the different conditions governing it to check the accuracy of the performance. These studies show that the proposed algorithm is faster and more accurate in detecting LOE fault. It also has higher security in distinguishing LOE fault from SPS. [ABSTRACT FROM AUTHOR]

Power systems are becoming more complex than ever and are consequently operating close to their limit of stability. Considering its significance in power system security, it is important to propose a novel approach for enhancing the transient stability, considering uncertainties. Current deterministic industry practices of transient stability assessment ignore the probabilistic nature of variables. Moreover, the time-domain simulation approach for transient stability evaluation can be very computationally intensive, especially for a large-scale system. The impact of wind penetration on transient stability is critical to investigate, as it does not possess the inherent inertia of synchronous generators. Thus, this paper proposes a risk-based, machine learning decision-making approach, for probabilistic transient stability enhancement, by replacing circuit breakers, including the impact of wind generation. The IEEE 14-bus test system was used to test and validate the effectiveness of the proposed approach. DIgSILENT PowerFactory and MATLAB were utilised for transient stability simulations (for obtaining training data for machine learning), and applying machine learning algorithms, respectively. [ABSTRACT FROM AUTHOR]

DFIG-based wind turbine has significantly reduced the power rating, cost of the converter and enables subsynchronous and super synchronous operation but it has largely suffered in maintaining the transient stability and power balance between the generator and grid panel when grid faults has occurred. Formerly, the methods such as PID controller, fuzzy controller, PI controller could maintain the stability to the certain extent only since the nature of the wind power plant is unpredictable and also grid faults can occur at any time so this DFIG-based wind turbine is in need of predictive controller for anticipating faults in grid side. To normalize this situation, this work has proposed a (Stochastic dynamic Programming) (SDP) based Non-linear model predictive controller (NMPC) where nonlinear load would be linearized by min-max normalization algorithm and then voltage profile would be analyzed using support vector regression; consequently, based on the analyzing result, dynamic programming based on stochastic would take the action dynamically. By this way, the proposed system has been maintaining the transient stability and power balance between the generator and the grid optimally. [ABSTRACT FROM AUTHOR]

In this article, a novel robust strategy is proposed for concurrent control of the synchronous generator's voltage and frequency in a single machine infinite bus plant. The methodology is based on infinity norm and Mu analysis and synthesis to prepare the robust function of the power system stabilizer, automatic voltage regulator, and load frequency control systems. Ten real structured uncertainties have been considered for the K1, K2 and K4to K6 coefficients of the Heffron–Phillips generator model, inertia constant, damping coefficient, the governor speed regulation coefficient, and the amplifier and exciter gains. Each uncertain parameter has a nominal value in the generator operating point with 25% tolerance excepts to amplifier and exciter gains where their tolerances are 12.5%. The proposed strategy efficiency lies in the strict converting of all ten real parametric uncertainties into the generalized structure of µ synthesis and the formation of efficient weighting functions. Based on the proposed strategy and H∞ norm optimization, µ-synthesis D-K iteration procedure and loop-shaping manner, three controllers have been obtained whose robust performances (RPs) are guaranteed. The supremacy of the offered controllers is shown by comparing their functions in four scenarios and three patterns. The simulation results reveal the good RP of the designed controllers. Also, for a benchmark problem as a single machine connected to a 230 kV network, the capabilities of the designed robust controllers have been shown. [ABSTRACT FROM AUTHOR]

The paper on "Moving Average Filter-PLL-Based Voltage and Frequency Control of Standalone WECS" a phase locked loop (PLL) is presented to solve the issue of fast and accurate estimation of system frequency during distorted voltage in a wind energy conversion system. The algorithms are the particle swarm optimization, genetic algorithm, imperialist competitive algorithm and selfish herd optimization. The next paper titled "Effective Control of Voltage and Frequency in Microgrid Using Adjustment of PID Coefficients by Metaheuristic Algorithms" presents four evolutionary algorithms to optimize a PID controller's coefficients for use in frequency and voltage control of a microgrid. The paper presents study of performance evaluation of the algorithm for diseases in apple trees and rice crop and compares the performance with other techniques to make inferences about the efficacy of the algorithm. [Extracted from the article]

In this paper, two robust controllers have been designed to automatically regulate the synchronous generator voltage for an extensive domain of the system parameters in a single-machine infinite bus (SMIB) framework. These two controllers are based on the fuzzy set, and the type-2 fuzzy logic plus the proportional–integral (PI) operation, respectively. The Fuzzy and Type-2 fuzzy logic decisions are independent of the system parameters which increase the system robustness against the uncertainties and disturbances, and the PI controller can eliminate the terminal voltage steady-state error. The performance of the controllers has been optimized by adjustment of the four coefficients of each controller through Artificial Bee Colony, Imperialistic Competitive Algorithm, and Particle Swarm Optimization (PSO). Five scenarios with four different patterns for reference input and disturbances have been considered to show the competency of the designed controllers. The simulations which have been done by PSO optimization results show the higher robustness of these controlling combination against the load fluctuations, the sequence of the input voltage, and changes in the system parameters, such as the gains and time constants of the amplifier, exciter, and generator in contrast to optimized PID with metaheuristic algorithms. [ABSTRACT FROM AUTHOR]

Strength quality can reflect the physical quality, strength forging plays a positive role to maintain a strong body and abundant energy. The transmission system of traditional fitness equipment, such as electric treadmill and bicycle fitness device, are difficult to achieve the force training effect of simulating the rapid change of resistance like wind gust change and slope change automatically according to the pre-programmed curve changes in real time or speed. Combined with the current situation and existing problems of fitness equipment at home and abroad, this paper develops a self-generating power generation and electromagnetic damping control system that does not require external power supply, also has intelligent charge and discharge function, which can adjust the resistance output in real time. The system, which takes permanent magnetic synchronous generator as the resistance source, can replace the complex mechanical resistance structure and some electric resistance structure, and is widely used in the fitness equipment such as treadmill and bicycle trainer. [ABSTRACT FROM AUTHOR]

The assessment of transient stability of multi-machine power system, in a post-fault scenario, is a very challenging task due to highly non-linear nature of the system equations. In this work, the physical concept of maximum relative acceleration of a machine at a fault scenario is related with the boundary of stability region. This approach is extended to develop a quadratic Lyapunov function using singular perturbed modelling. Unlike the conventional energy function methods, this Lyapunov function candidate is a more general energy function and has a decaying nature around an equilibrium point. Moreover, with higher order corrections, an improved Lyapunov function candidate is presented with simulation results of power system examples. The decaying nature of Lyapunov function candidate remains similar even without higher order corrections. However, the relevance of inclusion of higher order corrections is brought out in the cases of faults occurring at other than generator buses. Also, the upper bound of singular perturbation parameter in the model is within allowable limits and ensures the accuracy of results. [ABSTRACT FROM AUTHOR]

Permanent-magnet synchronous generator (PMSG) associated with power electronics is a complex object to control due to the existence of nonlinearly coupled variables, and time-varying parameters. This paper presents a new passivity-based current controller (PBCC) design with flux orientation of a conversion system-based variable speed wind with PMSG connected to the grid through PWM converter with DC-Link. This technique is energy based and injects a damping term which ensures the stability and the convergence of the measured signals towards their references which forces the conversion system to operate at an optimal power point, to extract the maximum power produced. The main objectives of this study consist of two main parts: extract the maximum wind power through controlling the rotational of the PMSG and transfer this power to the grid-side converter, for this, a new controller is proposed. The second one is to maintain the DC-link voltage and the generated reactive power at their reference values, despite any possible constraints related to the machine-side converter (MSC), for this, a classical PI controller is investigated, that is to improve performances of the wind system. The obtained simulation results under MATLAB/Simulink address the high-performance and fast response of the proposed strategy. [ABSTRACT FROM AUTHOR]

This paper presents an approach to the calculation of unbalanced fault currents in shipboard power systems based on the application of Millman's theorem. A full analysis of the time-variant fault current produced by a synchronous generator in a typical marine power system is provided; three phase three wire for principal loads and four wire earthed neutral for hotel loads. Hand calculation results obtained using a Millman's theorem based approach are contrasted with results obtained by computer simulation and baselined against hand calculation results produced using conventional symmetric component methods. Results show that the Millman's theorem based approach calculates fault levels that are broadly comparable to those produced using symmetric component methods. The Millman's theorem based approach is however conceptually much simpler to apply than the conventional symmetric component method as it does not use the fictitious sequence components and networks employed by the symmetric component technique. [ABSTRACT FROM AUTHOR]

Synchronous generator parameters are an important subset of input data to various power system studies. These parameters influence steady-state and dynamic behavior of the generator. This paper presents a framework to derive the parameters of a synchronous generator from grid connection test measurements. An industry standard generator model has been adopted to accurately match test measurements and simulation results obtained with the derived parameters. The proposed framework optimizes the parameters of the model to a higher accuracy level contributing to the fidelity of simulation results. A practical study is presented to demonstrate the performance of the proposed framework. [ABSTRACT FROM AUTHOR]

In this article, a fault ride-through controller is proposed with the use of proportional-integral compensator and electronic sensors for riding-through alternative current faults in a wind power plant collection grid connected with a permanent magnet synchronous generator. Three parallel-connected wind energy conversion units supplying a direct current (DC) load are simulated and discussed. It is found that the sub-module will directly adjust the transmission of power and protect the generator from overheating, which can occur due to voltage fluctuation. Furthermore, a DC voltage controller is designed to ensure a stable closed-loop system, and the system stability is verified using bode plots. The dynamic response of the system is demonstrated with the use of power simulator (PowerSim, Rockville, USA) software to verify the reliability of the proposed rectifier topology. [ABSTRACT FROM AUTHOR]

The battery charging control within wind turbine applications is the most important challenge in standalone exploitation mode because of the random nature of wind energy and irregular use of electricity. Within this problematic, this paper deals with monitoring and control of a permanent magnet synchronous generator voltage for battery charging. In the proposed topology, the output direct drive PMSG is linked to the battery through a vector-controlled pulse modulated (PWM) rectifier. Most wind energy conversion systems are based on precise knowledge of the wind speed, which makes the adjustment of the charge voltage relatively complicated, and degrades the powers captured with erroneous measurements of this wind speed. In this context, all the efforts of this work are meant to simplify and improve the dynamic performance of the system. The technique used in this work is devoid of wind measurement. By neglecting different losses, the approach adopted leads us to the reference electromagnetic torque, assuming that the wind speed and consequently the rotational speed of the turbine vary slowly in steady state. Using the load current and voltage measures, the proposed controllers calculate permanently the power reference that corresponds to the fixed battery voltage. A vector control approach is adopted to achieve decoupled power control on the supply side power converter by generating the direct and quadrature control voltages. These voltages are necessary to generate the corresponding duty cycles of the PWM active switching devices. Hence, the PWM rectifier maintains the battery voltage at a fixed value by balancing both the rectifier output current and the load input current. To activate the vector control, two dynamic controllers are designed, simulated, and compared. The first controller is based on simple PI regulators. Meanwhile, the second one, which is a sliding mode technique, is applied to control the battery voltage. In order to assess the effectiveness of the used techniques, simulation models have been subjected to critical conditions of changing in speed and load. Simulation results revealed a poor accuracy of the first technique during transients and its close correlation under load disturbance. Whereas the sliding mode controller has high precision and strong robustness in steady state and during transient phases. The system simulation is performed using MATLAB/SIMULINK. [ABSTRACT FROM AUTHOR]

In this paper, we propose a new control scheme for a wind energy conversion system connected to a solid-state transformer-enabled distribution microgrid. The system consists of a wind turbine, a permanent magnet synchronous generator, a rectifier and a load which is connected to the distribution grid dc bus. The scheme combines a classical PI placed, in a nested-loop configuration, with a passivity-based controller. Guaranteeing stability and endowed with disturbance rejection properties, the controller regulates the wind turbine angular velocity to a desired value – in particular, the set-point is selected such that the maximum power from the wind is extracted – maximising the generator efficiency. The fast response of the closed-loop system makes possible to operate under fast-changing wind speed conditions. To assess and validate the controller performance and robustness under parameter variations, realistic simulations comparing our proposal with a classical PI scheme are included. [ABSTRACT FROM AUTHOR]

Dynamic security assessment (DSA) is a vital part of power system planning and operation. Although various phenomena, such as line thermal loading, voltage stability, and frequency stability, are of interest in DSA, this paper particularly focuses on transient rotor angle stability of conventional synchronous generators in a transmission system. Integration of large wind and photovoltaic (PV) farms to the bulk power systems has brought various challenges to the conventional rotor angle transient stability of synchronous generators. It is, therefore, of immense importance to examine and comprehend the impact of various renewable generations and their penetration levels on the probabilistic transient stability. This paper uses time-domain simulation approach to analyse these impacts in terms of probability of system instability, based on the transient stability index (TSI). Various case studies are conducted on the IEEE 39-bus test system, considering the probabilistic nature of parameters (faulted line/bus, fault type, fault location, and fault duration). The results obtained indicate that hybrid renewable energy integration is the best choice for achieving the highest probabilistic dynamic security, considering (N-1) and (N-2) line and (N-1) bus faults. [ABSTRACT FROM AUTHOR]

In this study, we aimed to optimize 3000 kVA synchronous generator (SG) stator design to obtain the desired magnetic flux density distribution and efficiency. We used Maxwell simulations for experiments on some design parameters of stator (slot height and teeth width). Then second-order regression models are calculated that represent the relations between the factors (design parameters) and the measured performance criteria (called as the responses: stator-teeth flux density, stator-yoke flux density, and efficiency). These regression models are used at the multiobjective optimization phase. Bat algorithm (BA) is used for performing the multiobjective optimization. By combining Maxwell with regression modeling and BA, the efficiency of the SG is increased to 96.84% from 96.5% with a more acceptable magnetic flux density (between 1.65 and 1.70 T ranges). The stator-teeth flux density and stator-yoke flux density are calculated as 1.9 T and 2.07 T for the current SG, whereas these values are reduced to 1.647 and 1,634 T, respectively, for the optimized SG. Results of this study show how the numerical simulation can be successfully combined with the BA to improve the efficiency of the SG by providing the desired magnetic flux density distribution. [ABSTRACT FROM AUTHOR]

The power converter-based wind energy conversion systems (WECS) connected to weak AC networks may cause subsynchronous interactions that can potentially lead to instability. The interaction between the WECS converters and a nearby turbine-generator (TG) may lead to severe torsional vibrations. This article investigates the impact of a fully rated converters-based permanent magnet synchronous generator WECS (PMSG-WECS) on the subsynchronous torsional interactions (SSTI) of a nearby multimass TG connected to series compensated transmission line. A simple but effective systematic approach of modal analysis using open-loop systems is proposed. The proposed approach is used to evaluate the impact of PMSG-WECS on SSTI. Further, the impact of PMSG-WECS is analyzed through the damping torque, eigenvalue analysis and transient simulation under various control modes of PMSG-WECS converters. The results demonstrate that the inclusion of PMSG-WECS increases the subsynchronous resonance frequency of the network, thereby reduces the damping of the torsional modes in the high-frequency range of subsynchronous resonance frequency. The negative damping effect of PMSG-WECS significantly reduces the damping of subsynchronous network mode, thereby can destabilize the system. Also, the negative damping impact of PMSG-WECS significantly reduces the damping of high-frequency torsional modes. As a result, the torsional interactions aggravate at lower compensation levels. [ABSTRACT FROM AUTHOR]

Power generation from marine-turbines offers a vast potential for raising the contribution of renewable energy sources to the electricity grid. Typically, marine-turbine power units comprise marine-turbines that receive mechanical excitation from sea currents or tidal streams and synchronous or asynchronous generators that are finally connected to the electricity grid. Due to connection to the same transmission lines, interactions between the excitations of the individual generators appear. To achieve stabilization of the generators' functioning, as well as synchronization to the grid's frequency the generators' control has to compensate for such interactions. The article proposes a nonlinear optimal control approach for distributed marine-turbine power units that use synchronous generators. First, the dynamic model of the distributed power system undergoes approximate linearization around a temporary operating point which is re-computed at each time-step of the control algorithm. The linearization relies on first-order Taylor series expansion and on the computation of the associated Jacobian matrices. For the approximately linearized model of the distributed power system a stabilizing H-infinity (optimal) feedback controller is designed. To compute the controller's feedback gains an algebraic Riccati equation is repetitively solved at each time-step of the control method. The global stability properties of the control scheme are proven through Lyapunov analysis. The proposed control method retains the advantages of optimal control, that is fast and accurate tracking of the reference setpoints, under moderate variations of the control inputs. Among the advantages of the proposed control method one can note: (i) the presented nonlinear optimal control method has improved performance when compared against other nonlinear control schemes that one can consider for the dynamic model of the distributed marine power system (actually other control methods are neither of proven optimality, nor of proven global stability), (ii) avoids complicated state-space transformations and the related appearance of singularities in the computation of the control inputs which are applied to the nonlinear model (iii) minimizes the consumption of energy by the control system of the distributed marine-turbine generators, thus also reducing the functioning cost of such power units. [ABSTRACT FROM AUTHOR]

Magnetic nanocomposite UIO-66-NH2-MnFe2O4-TiO2-TiNT was synthesized for synchronous and selective adsorption of Cd(II) heavy metal and Methyl orange (MO) dye pollutants in the textile wastewater. XRD, SEM, FT-IR, BET and VSM techniques were used. The best conditions were obtained for the independent variables in the synchronous adsorption of Cd(II) and methylene orange (MO) dye for the initial metal concentration, initial MO concentration, pH, adsorbent amount and acid-promoted molar ratio 500 (mg/l), 146.8 (mg/l), 5.5, 0.159 (gr) and 46 respectively. After the adsorption, the adsorbent was removed from the solution well with an external magnetic field. [ABSTRACT FROM AUTHOR]

DC-DC converter plays a major role in microgrid and energy storage system using operational stability and synchronised power delivery. In this paper, an energy management control algorithm is proposed based on closed-loop proportional-integral (PI) to solve and analyse the issues of unstable DC link voltage. During grid-connected mode, a hybrid energy storage system (HESS), i.e. super-capacitor (SC) and battery units are charged from different hybrid energy resource, i.e. solar and wind. In the absence of energy resources (solar or wind), the energy storage units (supercapacitor and battery) need to supply the grid, which is the main aim of this work. Initially, the energy management control is used to control the generated power from wind and solar for the stability requirement. The MPPT technique has been considered here to make system flexibility and compatibility with different PV cell and wind energy. This proposed system successfully tracked the maximum power, which is analysed using the combined development of galactic swarm optimisation (GSO) based incremental conductance (IC) algorithm. Using GSO in MPPT should reduce the steady-state oscillation and get high convergence rate. The whole work is implemented in Matlab/Simulink platform and the performance of proposed is compared with existing algorithms. Abbreviation: HESS: Hybrid Energy Storage System; MPT: Maximum PowerPoint; PWM: Pulse Width Modulation; SOC: State of Charge; PMSG: Permanent Magnet Synchronous Generator; PI: Proportional Integral; AC: Alternating Current; DC: Direct Current; GSO: Galactic Swarm Optimization [ABSTRACT FROM AUTHOR]

The load angle of a synchronous generator connected to a power grid has an eigenfrequency that depends on the operating conditions. The existence of an eigenfrequency can make the generator sensitive to electrical and mechanical disturbances and motivates the use of damper windings and power stabilizing systems. Another reason for keeping load angle oscillations small is that they increase the eddy current losses in the stator core and clamping structure due to axial leakage flux. This is shown with transient finite element analyses and can be explained by a loss model derived from a phasor model of the eddy current loss density. [ABSTRACT FROM AUTHOR]

This paper develops a mathematic model to calculate the power losses and efficiency for an onboard three-level brushless synchronous generator (TLBLSG) which consists of pilot exciter (PE), main exciter (ME), and main generator (MG). A back-iteration algorithm which combines an analytical model of the MG stator loading with a three-phase diode bridge rectifier (TPDBR) and a capacitor, an equivalent circuit model of the MG, and a model of steady-state excitation current based on the open circuit characteristic (OCC) is employed to determine the electrical parameters in the MG. Besides, both ME rotor and PE stator currents are calculated by the model of induced electromotive force loading with a TPDBR and an inductance. All the obtained electrical parameters can reflect the influence of rotating speed and load change as well as the saturation effect. Finally, changing laws of the electrical parameters and power losses as a function of speed and load are simulated and discussed in detail. Moreover, efficiencies under different speeds and loads are analysed. The TLBLSG is suggested to be operated in a relatively high-speed range (from 15,000 to 25,000 r/min) and a relatively large load (from 25 to 65 kW) for a high efficiency. [ABSTRACT FROM AUTHOR]

Integration of the doubly-fed induction generators (DFIGs) changes the existing low frequency oscillation (LFO) modes of power systems and introduces the LFO modes, which may be damped by the power system stabilizer (PSS) installed at the synchronous generators, or recently at the DFIGs. In this article, the state space equations including the transfer function of the DFIG-PSS are derived, based on which, the analytical expression of the functional eigen-sensitivity model is proposed. To improve the accuracy of the existing functional eigen-sensitivity, the eigenvalue increment is introduced to the iterative calculation of the transfer function increment. The optimization model of the DFIG-PSS parameters is formulated based on the functional eigen-sensitivity, which is solved by the interior point method. Finally, the damping effect of the DFIG-PSS on the critical modes is provided to validate the accuracy of the functional eigen-sensitivity model. [ABSTRACT FROM AUTHOR]

This paper describes the characteristic investigation of the Novel Dual-stator V-Shape Magnetic Pole Six-Phase Permanent Magnet Synchronous Generator (NDSVSMPSP-PMSG) for wind power application. The proposed generator has V-shaped embedded magnetic pole in the rotor and six-phase winding in both the stator. The proposed generator has high-power density and high efficiency. For emphasizing the significance of the proposed generator, the characteristics of the NDSVSMPSP generator are analyzed and compared to one of the traditional generators, i.e., the Dual-stator Surface Mounted Six-Phase Permanent Magnet Synchronous Generator (DSSMSP-PMSG). For the design and characteristic investigation of both the generator, Finite Element Method (FEM) is chosen because of its high accuracy. Two modes of FEM analysis are considered, namely magneto-statics and transients. The magneto static analysis is used for the study of flux line and flux density distribution, while the transient analysis is considered for the generator's characteristic investigation. The performance characteristics such as generated Electromotive Force (EMF) for both inner and outer stator, Percentage Total Harmonic Distortion (THD) of developed voltage, Developed EMF vs rpm, terminal voltage vs. current, developed rotor torque vs time, percent (%) ripple content in torque, and percent efficiency vs current for both generators are investigated. As a result, it can be stated that the power density and reliability of the proposed generator is higher than that of the traditional generator. [ABSTRACT FROM AUTHOR]

This paper develops a universal Real-Time Graphical User Interface for the first time for low-voltage energy Harvesting. The proposed GUI is built in LabVIEW with NIUSB 621 DAQ that synchronized the data to perform real-time analysis through the use of power electronics. A hybrid Vertical Axis Wind Turbine adapted to a 200 W Permanent Magnet Synchronous Generator is used for incorporating the supercapacitor-based battery charging energy harvesting system. The GUI displays the real-time energy harvesting output readings both graphically and digitally along with wind speed and angular velocity of the turbine. The model is built in such a way so that it could be used as a universal GUI for both wind and solar energy harvesting with minimal adjustment. [ABSTRACT FROM AUTHOR]

Security and economy of a power system are optimised by controlling of reactive power dispatch from synchronous generators and var sources like SVCs installed in the system. Generator bus voltages, transformer tap positions and SVC settings are the control parameters in optimal reactive power dispatch (ORPD) problem. Generally, population-based optimisation algorithms are used for optimising the values of control variables. In this work, a hybrid version of bio inspired algorithm of firefly optimisation algorithm (FFA) is suggested for reactive power optimisation. This proposed DE/FFA-based algorithm mimics the mating behaviour of fireflies. The exploration capability of basic FFA is poor and is enhanced by hybridising with the differential evolution algorithm (DE). The strength of this algorithm is tested by comparing its performance with that of the other bio inspired algorithms like Biogeography Based Optimisation (BBO). The new method is tested on the IEEE-14 bus, IEEE-30 bus and IEEE-57 bus test systems. The results obtained are much encouraging. [ABSTRACT FROM AUTHOR]

Winding fault diagnosis and failure prognosis technique has been developed based on d-q model of brushless synchronous generator (BLSG) considering actual winding insulation degradation curve of machine in inter-turn fault, damper bar and field currents for various severities of inter-turn winding faults have been estimated using extended Kalman filter. For validation of damper bar currents, 2 D transient electromagnetic analyses using finite element method have been done, and 2nd harmonic component of damper bar currents for various severities of inter-turn fault in stator windings have been computed by Fourier transformation. The winding insulation degradation curve of machine has been determined by accelerated life test, and used for estimation of remaining useful life of machine under inter-turn fault, assuming a pre-defined failure threshold. Actual and predicted life of the BLSG has been compared. Wireless sensors using rotor telemetry system have been mounted on the rotor of BLSG for experimental validation of field currents under winding faults. The 2nd harmonic of damper bar currents increase with increase in severities of winding faults and do not get affected by diode failures in rotating rectifier, hence this can be used as a robust fault indicator for diagnosis and prognosis of inter-turn winding fault in BLSG. [ABSTRACT FROM AUTHOR]

—Subsynchronous resonance (SSR) is an undesirable phenomenon in series compensated power system which tries to menace the stability of both electrical and mechanical system. This paper researches the effect of static synchronous compensator (STATCOM) for mitigation of SSR in a single machine infinite bus system. The mathematical modeling is presented in the form of linearized equations, which can be used for eigenvalue analysis of SSR. A novel control technique based on unit template algorithm is incorporated in STATCOM for alleviation of SSR and it proves to be ingenious in damping out all the oscillations. Furthermore, frequency scan and fast Fourier transform (FFT) analysis are presented, that provide resonant frequencies at different levels of compensation and dominant modes of oscillations respectively. To examine and authenticate the efficacy of the proposed controller, the IEEE second benchmark model on SSR is simulated in MATLAB/Simulink environment and the results are analyzed to illustrate the potency of the proposed control strategy. [ABSTRACT FROM AUTHOR]

This article examines the modal condition under which a grid-connected PMSG may cause the sub-synchronous oscillations (SSOs) in a power system. The examination is based on a closed-loop interconnected model of the power system, wherein, the PMSG and the remainder of power system (ROPS) are modeled as two separate but interconnected open-loop subsystems. The model condition being examined is that an SSO mode of the open-loop PMSG subsystem is close to an SSO mode of the open-loop ROPS subsystem on the complex plane. Analysis in the article indicates that the modal condition is the near strong open-loop modal resonance (NSOMR), under which damping of one corresponding closed-loop SSO mode may very likely degrade. The damping degradation can be estimated by an SSO index derived in the article. Hence, study presented in the article reveals the mechanism about why the SSOs may be caused by the grid-connected PMSG from the perspective of the NSOMR. In addition, it is proposed that by applying the modal analysis to the open-loop subsystems, the SSO instability risk brought about by the PMSG can be detected and the risk-contributing PMSGs and synchronous generators in the power system can be identified. [ABSTRACT FROM AUTHOR]

In this paper, rotor angle and voltage dynamics decoupling in a synchronous generator connected to an infinite bus using a partial feedback linearization-based nonlinear voltage regulator (FBLAVR) is described. It is well known that the fast voltage regulation using static excitation system introduces negative damping in the system. If this coupling can be eliminated then one can simultaneously achieve fast voltage regulation and desired damping performance. This paper identifies such a decoupling behavior using an FBLAVR and shows that the damping with the FBLAVR only depends on the inherent damping of the machine. The necessity of a power system stabilizer (PSS) is identified even with the FBLAVR, if the natural damping is not sufficient. Thus motivated, an FBLAVR + PSS control scheme is proposed and compared with a linear automatic voltage regulator (AVR) + PSS control scheme. It is shown that the generator-exciter-power system [GEP(s)] characteristics with FBLAVR does not change with the system operating conditions. The superiority of the proposed control scheme is validated over a wide range of operating conditions on a single machine infinite bus (SMIB) power system. [ABSTRACT FROM AUTHOR]

In the paper, a combined strategy of moth–flame optimization (MFO) algorithm and fuzzy logic controller (FLC) for incipient fault diagnosis of the synchronous generator is proposed. The motivation behind the proposed topology is to analyse the beginning issues exhibited by an asynchronous generator under different situations like healthy and unhealthy conditions. Initially, a synchronous generator is assessed in the ordinary condition and from that point onwards, fault is made in the synchronous generator and the framework practices are checked and signals are measured which can be viewed as mis-shaped waveforms. For the collection of data-set from the input current signal, MFO is presented which extracts the signal and structures the possible data-sets. In light of the fulfilled data-set, the FLC performs and diagnoses the kind of fault that has happened in the stator winding of the synchronous generator. In order to evaluate the effectiveness of the proposed method, the incipient faults are analysed. The proposed technique is implemented in MATLAB/Simulink platform and this is approved utilizing execution measures, for example, accuracy, precision, recall, and specificity. Likewise, the proposed method is analysed with factual measures, for example, the root mean square error, mean absolute percentage error, mean bias error, and consumption time; and the execution is evaluated by utilizing the examination at various strategies like artificial neural network, fuzzy, and adaptive neuro fuzzy inference system techniques. [ABSTRACT FROM AUTHOR]

Based on non-linear systems described by multibond graphs, a procedure designed to present symbolic linearization of these multibond graphs, is presented in this paper. Firstly, a junction structure of a multibond graph with multiport gyrators that represent Eulerian junction structures is proposed. In addition, non-linear multiport resistors are considered. By knowing the non-linear causal paths and loops of the non-linear multibond graph, the linearization is obtained by two steps: (1) The original multibond graph on the nominal operating point is evaluated; (2) New and additional paths based on the non-linear causal paths and loops are included. The state space representation of the linearized multibond graph using the corresponding junction structure is presented. An advantage of this methodology is its ability to allow the user to define a nominal operating point in which the linearization will be carried out. In order to apply the proposed methodology, two physical systems are modelled and linearized by multibond graphs: a synchronous generator and a two degrees of freedom PUMA. Simulation results of these non-linear and linearized systems are shown. [ABSTRACT FROM AUTHOR]

Distributed generators using power electronic converter interface have no inherent inertial response similar to that from the rotating mass of conventional synchronous generators. Virtual synchronous generator (VSG) emulates the behavior of the synchronous generator including system inertia to improve system dynamic performance. Unlike a real synchronous generator, using VSG with proper design, the equivalent inertia of the distributed generator can be controlled in a wider range. In this paper, a flexible virtual synchronous generator (FVSG) control strategy is proposed, with adaptive inertia contributing to a fast and smooth inertial response. The frequency change rate is designed as an adaptive inertia coefficient to flexibly accommodate system inertia with frequency fluctuation rate. Compared with the conventional VSG control, based on fixed inertia coefficient, both inertia support and oscillation suppression are achieved in the proposed control scheme. Moreover, the principles of control parameters design are analyzed in details. Thus, the dynamic response of the system frequency can be substantially improved by the FVSG. Both Matlab/Simulink simulations and prototype tests are implemented to validate the proposed FVSG control strategy on improving system dynamic frequency performance. [ABSTRACT FROM AUTHOR]

In this paper, virtual synchronous generator (VSG) model based control of photovoltaic power generations (PVs) for power system stability improvement is proposed. Different from other studies on VSG, a large-scale power system is the main target of the proposed control. Therefore, digital simulations are conducted using the IEEJ WEST 10-machine System Model, which is a typical large-scale power system model in Japan. In this power system, the system stabilization effect of the control is verified. In addition, the storage capacity of the energy storage device in PV required for achieving the control is evaluated. The simulation results show that the proposed control is more effective for the system stability improvement than the constant power control of the PV. In addition, it is shown that AVR function of the VSG model based control is necessary in the power system with poor voltage stability. [ABSTRACT FROM AUTHOR]

Automatic voltage regulator (AVR) system is an important device to regulate synchronous generator output voltage. Controllers are used to provide better stability and faster response for AVR system and this article shows two types of controllers: proportional-integral-derivative (PID) and proportional-integral-derivative-acceleration (PIDA) controllers. Harmony search algorithm (HSA), local unimodal sampling (LUS), and teaching learned based optimization (TLBO) are the optimization techniques used to tune each controller parameters. Integrated square error (ISE) is used as an objective function to minimize error in voltage for better stability and response. Transient response, root locus, and bode diagram are calculated for each controller using the three optimization techniques. The results are compared with other optimization techniques to find out the best performance and stability for an AVR system. The results show also which controller is better. Robustness analysis is made on the best system to check terminal voltage response with respect to load variation to ensure that this system can be applied for the AVR of synchronous generator in power system. [ABSTRACT FROM AUTHOR]

To ensure the proper operation of power system, some independent system operators have specified that wind power plants should be able to manipulate power output for frequency control. This article presents a combined control scheme which exploits the self-capability of permanent magnet synchronous generator-based wind turbine to provide primary frequency response. Under normal condition, the wind turbine operates in de-loading mode to obtain the power reserve. Once frequency deviation is detected, the proposed control strategy can not only make use of the power reserve for frequency regulation by adjusting the rotor speed, but utilize the kinetic energy in rotor to provide frequency response as well. Besides, the energy stored in DC capacitor is also employed for frequency support. The simulation results reveal that the wind turbines with the proposed method can improve frequency performance under both constant wind speed condition and variable wind speed condition. [ABSTRACT FROM AUTHOR]