Virtual Machine Concept Research Articles

Source‐load cooperative frequency regulation based on virtual synchronous/asynchronous machine concept

AbstractDue to the absence of inertia, the high proportion of electronic power equipment is a great threat to the stability of the power system. Previous studies have proposed the virtual synchronous machine (VSM) control method for the inverter‐based distributed generators (DG). However, due to the capacity limitations of DG, the capability of the inverter to provide the inertia action is limited. At the same time, some controllable loads also have the ability to provide inertial support but are still not fully utilised. To get a better grid frequency response, this paper proposes a source‐load coordination strategy based on the VSM and virtual asynchronous machine (VAM) concept. For that purpose, a detailed VAM model is firstly derived for the rectifier on power demand side. Not only the virtual inertia and frequency oscillation damping can be provided, but also the synchronisation units are not needed to obtain the unknown grid frequency. After that, a distributed consensus‐based secondary control is present to regulate the frequency to converge to a reference value based on VSM and VAM. Compared with the existing frequency regulation method, the proposed scheme makes full use of the ability of the load side to participate in frequency modulation. Finally, some numerical simulations are performed to validate the feasibility of the proposed method on MATLAB/Simulink.

Operation Strategy Optimization of Energy Storage Virtual Synchronous Machine Using Big Data Analysis Technology

With the increasing combination of energy with the power grid, energy storage systems play a crucial role in maintaining grid stability and ensuring reliable power supply. In recent years, the concept of energy storage virtual synchronous machine (VSM) has emerged as an effective and flexible method for mimicking the behavior of synchronous generators in energy storage systems. This paper presents a new approach to optimize the operation strategy of energy storage VSM using big data analytics techniques. The proposed method utilizes data analysis to enhance the performance and efficiency of energy storage systems, contributing to overall grid reliability and resilience. Neural networks are employed as an efficient big data analytics technique, and in this study, they are applied to evaluate and optimize the operation strategy of energy storage VSM. Firstly, this paper evaluates the operation strategy of energy storage VSM using a deep belief network (DBN) as the underlying network. Secondly, an improved whale optimization algorithm (WOA) is proposed. IWOA initializes the initial population by employing a mapping strategy, laying the foundation for global search. Furthermore, IWOA introduces a nonlinear strategy to balance the global and local exploration capabilities, while avoiding premature convergence based on diversified mutation strategies. IWOA demonstrates significant improvements in search speed and convergence accuracy, with a strong ability to escape local optima. Thirdly, this paper utilizes IWOA to initialize the weights and thresholds of the DBN network, constructing IWOA-DBN. The network is then utilized to evaluate and optimize the operation strategy of energy storage VSM based on the evaluation results. The feasibility and correctness of IWOA-DBN are validated through systematic experiments.

Dual-Core PLC for Cooperating Projects with Software Implementation

Development of a general-purpose PLC based on a typical dual-core processor as a hardware platform is presented. The cores run two cooperating projects involving data exchange through shared memory. Such a solution is equivalent to a single-core PLC running two tasks by means of a real-time operating system. Upgrading to a typical programming tool involves defining which of the global variables are shared, and whether a variable in a particular core is read-from or written-to the shared memory. Extensions to core runtimes consist of read-from at the beginning of the scan cycle and write-to at the end, and of an algorithm for protecting the shared memory against access conflicts. As an example, the proposed solution is implemented in an engineering tool with runtime based on a virtual machine concept. The PLC prototype is based on a heterogeneous ARM dual-core STM32 microcontroller running different projects. The innovation in the research lies in showing how to run two projects in a dual-core PLC without using an operating system. Extension to multiple projects for a multi-core processor is can be accomplished in a similar manner.

General Method to Foresee the Behavior of Virtual Synchronous Machines Working With Distorted and Unbalanced Voltage Conditions

To make photovoltaic and wind power plants able to provide grid services (i.e., inertial behavior, grid support and harmonic compensation), several control algorithms have been proposed in the literature during the last years. The most promising ones make the power electronic converters behave as conventional alternators, using the concept of Virtual Synchronous Machine (VSM). Several VSM models are available in the literature, some of which can improve the voltage quality at the point of connection with the grid behaving as harmonic and unbalance sinks under non–ideal grid voltage conditions. However, the literature lacks a general method to foresee the behavior of a generic VSM configuration in such conditions along with a well–established definition of the needed features to make VSMs able to work as harmonic or unbalance sinks. Therefore, this paper proposes a simple and general method to foresee the behavior of different VSM configurations under non–ideal grid voltage conditions before any experimental verification. The proposed method accurately foresees the VSMs behavior, as experimentally demonstrated on five VSM models available in the literature, working with fifth harmonic and inverse sequence voltage distortions. Moreover, the method identifies which VSM configuration can feature a beneficial harmonic and unbalance compensation.

Dead–Time Effect on Two–Level Grid–Forming Virtual Synchronous Machines

The concept of Virtual Synchronous Machine (VSM) is a promising solution to integrate renewable energy sources into the grid. Thanks to this approach, renewable energy sources can provide grid services (e.g., inertial behavior), grid support during faults and island operation. Moreover, VSMs can enhance the voltage quality at the point of connection to the grid by behaving as harmonic and unbalance sinks under non–ideal conditions (i.e., grid harmonic distortion and unbalance). However, the inverter dead–time affects the harmonic and unbalance sink capability of grid–forming VSMs with no closed loop current control. Although the literature contains several papers concerning the dead–time issues, the negative influence of the switching dead– time on the harmonic and unbalance sink capability of VSMs has not been analyzed. Therefore, this paper demonstrates through experiments that: (1) the inverter dead–time effect limits the harmonic and unbalance sink capability of grid–forming VSMs under non–ideal grid voltage conditions and (2) a dead–time compensation is mandatory to make grid–forming VSMs behave according to the theoretical analysis. A first experimental test shows that both the dead–time and its compensation do not influ- ence the VSM response under normal operating conditions (i.e., symmetrical and sinusoidal grid voltage). Next, two experimental tests under a 5% grid voltage unbalance and a 10% grid voltage fifth harmonic distortion validate the negative influence of the dead–time and the beneficial effect of its compensation.

Small-Signal Stability Modeling, Sensitivity Analysis, and Parameter Optimization of Improved Virtual Synchronous Machine Based Standalone Inverter

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.

A Newly Proposed Prospective and Robust Computer Networking Model Architecture Based on the Infrastructure of Cloud Computing Contrivance

Abstract: Computer Networking Play’s a major role for data communication or data sharing and data transmissions from one location to another, which are geographically differ, but in today’s scenario where the main and primary major concerns are not to data transfer but also utilize all resources with greater efficiency and also preserves the confidentiality and integrity of the messages with respect to speed and time with lower Bandwidth and also consume a very low computational costs with low power supply and redirect to optimality. Cloud Computing also play’s a significant role to access data at geographically different locations. So In this paper we create a fusion of Computer Networking Architecture and Cloud Computing Architecture and released a very much superior fundamentally strong Cloud computing based Computer Networking model, which works on the concepts of ‘Virtualization’. Because when the number of hardware components (Servers) drastically increases all factors which are responsible to make possible networking among nodes are also consume each resources at extreme level, and networking becomes complex and slow, that’s why we used the concept of Virtual Machine. In this paper we proposed a Computer Networking model using the concepts of Cloud Computing. This model also suitable for data transmission but also take concern the most significant feature of Computer Networking, which is Data Security. This model also used some Proxy servers/ firewalls to take concern some security mechanisms. In this paper we also proposed Communication Oriented model among the Intercluster domains that how one node which belongs to another CLOUD cluster make possible communication among other InterCLOUD clusters with respect to data security measures. In this paper we proposed three models related to this networking model, which is CLOUD Networking Infrastructure, Connection Oriented model, Communication Oriented model. The detailed description of all three models are in the upcoming sections of this paper. Keywords: Cloud computing based computer networking model, A virtual model for computer networking, Computer Networking model based on virtualization, Virtualization based computer networking model.

Load Sharing Scheme Incorporating Power Security Margins for Parallel Operation of Voltage Source Inverters

The interconnection of distributed energy resources (DERs) in microgrids (MGs) operating in both islanded and grid-connected modes require coordinated control strategies. DERs are interfaced with voltage source inverters (VSIs) enabling interconnection. This paper proposes a load demand sharing scheme for the parallel operation of VSIs in an islanded voltage source inverter-based microgrid (VSI-MG). The ride-through capability of a heavily loaded VSI-MG, where some of the VSIs are fully loaded due to the occurrence of an event is investigated. In developing analytical equations to model the VSI, the concept of virtual synchronous machines (VSM) is applied to enable the VSI mimic the inertia effect of synchronous machines. A power frame transformation (PFT) that takes the line ratios of the MG network into account is also incorporated to yield satisfactory transient responses of both network frequency and bus voltages in the MG network. A Jacobian-based method is then developed to take into account the operational capacity of each VSI in the VSI-MG. The resulting amendable droop control constrains the VSIs within their power capabilities when an event occurs. Simulation results presented within demonstrate the effectiveness of the proposed procedure which has great potential to facilitate efforts in maintaining system reliability and resiliency.

Inertia emulation with incorporating the concept of virtual compounded DC machine and bidirectional DC–DC converter for DC microgrid in islanded mode

Inertia emulation with incorporating the concept of virtual compounded DC machine and bidirectional DC–DC converter for DC microgrid in islanded mode

Privacy Preservation-Based Access Control Intelligence for Cloud Data Storage in Smart Healthcare Infrastructure

Cloud service providers emphasize the concept of virtual machines, wherein resources and services are accessed over a distributed network system. The loss of user privacy is indeed contempt in concern to any individual or organization, particularly concerning the Healthcare infrastructure. This research paper introduces a Euclidean L3P-based Multi-Objective Successive Approximation (EMSA) algorithm, an efficient measure of privacy in the Healthcare Cloud. The role-based encryption keys are the critical foundation for the storage of sensitive data in cloud environments is presented here. The proposed EMSA algorithm is the hybridization of the existing Euclidean L3P Distance algorithm, Multi-objective Optimization algorithm, and Successive Approximation Iterative Proximate algorithm. In addition, the performance of the proposed EMSA compared with Bat, PUBAT, TPNGS, WOA, and CIC-WOA algorithms based on performance metrics, such as fitness, privacy, and utility. The simulation shows that, comparison to the existing state-of-the-art algorithms, the proposed EMSA model achieves higher privacy values of 0.34, 0.42, 0.42, 0.35, and 0.30.

A High Current High Power Density Motor Drive for a 48-Volt Belt-Driven Starter Generator (BSG) System

A 48 V Belt-Driven Starter Generator (BSG) System is featured with high output current, high starting torque, and highly efficient thermal management. This paper firstly elaborates hardware design considerations of a high power density three-phase BSG inverter to address the challenges of even current distribution among paralleled MOSFETs, small drain-source voltage spike and good thermal dissipation. In order to satisfy the high-current requirement, a careful selection of MOSFET device with high-current rating and low on-resistance has been presented. In order to suppress circulating current among paralleled devices, individual gate resistors have been placed in the gate loop of each MOSFET. In order to provide good thermal dissipation, an Insulated Metal Substrate (IMS) board and single-layer layout technique have been implemented. Multiple low-profile electrolytic capacitors are used to increase the power density of the prototype. Moreover, the use of automotive gate driver IC TLE9180 and microcontroller TC1782 makes the prototype more readily accepted by industry. An improved Interior Permanent Magnet (IPM) motor control strategy and a pump-back system based on a virtual machine concept have been implemented to facilitate the validation of the prototype under rated condition without using a real motor. The control algorithm automatically adjusts the onset of field-weakening by using an additional inverter voltage loop and takes into account the nonlinearity of the stator flux linkage by using curve fitting technique, which makes the motor drive adaptive to machine parameter changes as well as DC bus voltage fluctuation. A three-phase BSG inverter prototype with a peak power of 12 kW has been built and tested. The prototype power density has reached 20.3 kW/L. Both PLECS simulations and hardware experiments show a continuous and stable operation with up to 200 A phase current and up to 600 Hz output frequency.

Linear and uniform swing dynamics in multimachine converter-based power systems

The increase in RES generation is replacing the classical synchronous generators (SGs), which has resulted in gradually losing the beneficial inherent properties of SGs for power system stability. In order to mimic the inertial behavior of SGs, the concept of Virtual Synchronous Machines (VSMs) has been proposed, but their interactions at different time-scales and their effect on system stability are not yet fully understood. Therefore, a new scientific basis for designing and regulating the system is required. This paper contributes by advancing the idea of Linear and Uniform Swing Dynamics (LSD). This concept can be used to shape the dynamic behavior of these VSMs by controlling the eigenvalues to be constant throughout its operating region. Consequently, the validity of small-signal stability analysis can be extended for larger disturbances. Existing approaches to achieve LSD for a Single-Machine – Infinite Bus (SMIB) system are analyzed and complemented, and extended for multi-machine systems. The stability analysis using system differential equations is presented. Time-domain simulation results in MATLAB/Simulink are presented to validate the concept.

Dynamic Analysis and Model Order Reduction of Virtual Synchronous Machine Based Microgrid

The concept of virtual synchronous machine (VSM) was proposed to deal with the shortcomings of low inertia and damping of traditional control strategies for power electronic converters. But what if all distributed energy resources and controllable loads in a microgrid adopt the VSM control strategy, and will it present better performance than conventional droop control-based microgrid (DMG)? In this paper, the VSM-based microgrid (VSMG) is analyzed. The small-signal modeling of the VSMG is studied at first. Then static stability and dynamic characteristics of the VSMG are analyzed and compared with the DMG in both frequency-domain and time-domain. With the growing scale of microgrids, their modeling and simulation are becoming significant computational burdens. Inspired by the participation factor analysis of the VSMG and the concept of coherency in power systems, the VSMG small-signal model is equivalent to a modified third-order synchronous generator (SG) model in this paper. The equivalencing involves gray-box system identification and is realized by estimating equivalent electrical parameters alternately and iteratively. The equivalent SG (EqSG) model is compared with three representative model order reduction methods to verify its effectiveness. Simulation results confirm the accuracy of the EqSG model substituting detailed VSMG model in time-domain simulations.

Centralized VSM control of an AC meshed microgrid for ancillary services provision

This paper proposes a centralized control strategy for distributed generation (DG) sources connected to an AC meshed microgrid (MG). Through the proposed strategy, power production of distributed generators is managed such that the injected active and reactive powers at the point of common coupling are equal to predefined set-points. Thus, the MG is able to provide the main ancillary services including frequency and voltage control. An extended load flow model is used to identify active and reactive power production of each DG unit such that the total power injected to the utility grid satisfies the required setpoints. Hence, from the point of view of the transmission system operator (TSO), the whole MG can be seen as a single entity that behaves as a «PQ» generator. This control is intended to facilitate the management of power systems including a large number of microgrids and DG sources in terms of stability analysis, optimal reactive power dispatch, optimal power flow, etc. Furthermore, since the centralized control allows to set «PQ» power production to any predefined value, it was proposed to operate the whole MG using the concept of Virtual Synchronous Machine (VSM). It has been shown that, through the proposed control, the MG can reproduce the behavior of conventional synchronous generators during normal conditions and during faults.

Virtual machine concept applied to uncertainties estimation in instrumented indentation testing

Abstract

Improved VSM control of PMSG-based wind farms for transient stability enhancement

This paper analyzes the optimal control strategy of PMSG-based wind farms during faults in order to improve the transient stability of a power system with a high penetration rate of wind power. The investigated control strategies are the unity power factor (UPF), reactive power control (RPC), and particularly the concept of virtual synchronous machine (VSM). The transient stability level is assessed using the critical clearing time index, which was calculated based on trajectory sensitivity analysis. In light of the obtained results, it was found that RPC gives the best transient stability level, followed by the classical VSM control. Hence, an improved VSM control was proposed based on the transient model of a synchronous generator. The improved VSM has shown a behavior similar to a real synchronous generator, which results in better transient stability performances.

Optimal Switched Mode Control to Synthesize Dynamic Frequency Response from Virtual Synchronous Machine in Islanded Microgrid Operation

Abstract Islanded microgrids can experience severe frequency variation due to their inherently low inertia. Virtual inertia has been proposed in the literature to overcome this shortage. Virtual Synchronous Machine (VSM) concept has been the cornerstone of realizing virtual inertia from inverter connected energy sources. In this paper we propose and solve an optimal control problem to identify the optimal switching controls that achieve best dynamic frequency response from VSM. The results show that the optimal number of switching stages is independent of system parameters, and the optimal timing for switching between two control modes can be determined using local measurements alone, without having to perform complex computations.

A Hybrid Approach for Virtual Machine Migration in Cloud Computing Environment

A lot of research has been done in the field of cloud computing in computing domain. For its effective performance, variety of algorithms has been proposed. The role of virtualization is significant and its performance is dependent on VM Migration and allocation. More of the energy is absorbed in cloud; therefore, the utilization of numerous algorithms is required for saving energy and efficiency enhancement in the proposed work. In the proposed work, green algorithm has been considered with meta heuristic algorithms, ABC (Artificial Bee colony .Every server has to perform different or same functions. A cloud computing infrastructure can be modelled as Primary Machineas a set of physical Servers/host PM1, PM2, PM3… PMn. The resources of cloud infrastructure can be used by the virtualization technology, which allows one to create several VMs on a physical server or host and therefore, lessens the hardware amount and enhances the resource utilization. The computing resource/node in cloud is used through the virtual machine. To address this problem, data centre resources have to be managed in resource -effective manner for driving Green Cloud computing that has been proposed in this work using Virtual machine concept with ABC and Neural Network optimization algorithm. The simulations have been carried out in CLOUDSIM environment and the parameters like SLA violations, Energy consumption and VM migrations along with their comparison with existing techniques will be performed.

Integration of DC Microgrids as Virtual Synchronous Machines Into the AC Grid

A smart and autonomous integration concept for dc microgrids into the legacy ac grid is proposed based on the virtual synchronous machine (VSM) concept. It utilizes a dc–ac converter as a universal VSM-based interface (VSMBI) between the ac grid and various distributed energy resources (DER) connected on the dc side. The control strategy of it includes: 1) a frequency regulation improved from previous VSM works, which is suitable for the microgrid integration; 2) an improved dual droop control between the ac frequency and the dc side energy storages; 3) a power system stabilizer to enhance the system stability. Under this concept, the VSMBI integrates the DERs, loads and energy storages in the dc microgrid into a VSM. The VSMBI and the dc microgrid together will respond to short-term and long-term requirements of the grid frequency regulation, and achieve autonomous power management for the ac grid and the dc microgrid. It is therefore an important step forward in supporting high DER penetration. The concept, its design and small-signal analysis are presented in this paper. Its effectiveness and functions are verified by simulation and experimental results.

A High-Frequency High-Power Test Bench for 11 MW/595 Hz Drives With 1.25 MW Grid Capability

This paper presents a pumpback test bench for high-frequency high-power variable-frequency drives (VFDs) with 11 MW power rating and up to 595 Hz load frequency. A voltage combiner concept is applied to allow a high-frequency output from the two three-level neutral-point-clamped integrated gate-commutated thyristor bridges with minimum switching losses. The accordingly developed pumpback test bench applies a dc power coupling concept combined with a virtual grid concept that can achieve 11 MW test capability with only a 1.25 MW facility transformer. By applying a virtual machine concept, the pumpback test can be conducted without the need of high-frequency machines, while the circulating power losses in the pumpback loop are minimized as well. The virtual grid including the concept tradeoff, filter parameters, and modulation schemes is presented in detail. Moreover, design and installation guidelines for high-frequency components, especially the cables, are presented. The high-frequency high-power VFD and its pumpback test bench are both successfully built and experimentally validated at their rated operation points.