Digital Simulation System Research Articles

A New FPGA-Based Real-Time Digital Solver for Power System Simulation

Considering the rational use of field programmable gate array (FPGA) resources, this paper proposes a new FPGA-based real-time digital solver (FRTDS) for power system simulation. Based on the relationship between the number of computing components, the operating frequency, and the pipeline length, the best selection principle is given. By analyzing the implementation method of the Multi-Port Read/Write Circuit, the computing formula of the Look-Up-Table (LUT) consumption was derived. Given the excessive use of LUTs in the original computing components, the computing components were assembled in a single typical arithmetic expression of the power system simulation program, as the basic computing formula was characterized by a subset of the typical computing formula and multiple uses of the same variable. Data communication between different computing components was realized by using Multi-Port Input Circuits that share some outputs of read controller, and Multi-Port Output Circuits, which share some outputs of computing cores. According to the test results of original FRTDS and new FRTDS, it was found that the solution proposed in this paper had a shorter ideal simulation time and a higher parallel computing capability, which was very suitable for real-time digital simulation of power systems.

Standardization of digital technologies of simulator systems as a method of ensuring reliability of conditions of service of power engineering facilities (part 1)

Matters are considered of standardization of digital simulator systems for ensuring reliability of service of various power engineering facilities. Definitions are given to such terms as reliability, functioning conditions anf safety.Industry-specific reference normative documents are presented regulating requirements to technical means for training power engineering personnel. Mandatory minimum requirements and criteria are presented to simulators of operating personnel of power generation enterprises according to the rates established. Existing regulatory technical documents and regulations on requirements to simulators of operating personnel are presented in an overview. Particular emphasis is put on creating technical specifications for certification of applied software tools of simulators of thermal power plants and networks, including compliance with requirements to identification characteristics of software tools, to functional characteristics, to data processing functions, as well as to compatibility and safety, and to user interface.Of considerable importance is the method of evaluation of the simulator, especially with consideration of today’s information technology requirements. The current state of most of developments in Russia’s simulator-building is considered in details, including: creating electronic lectures on description of technical characteristics of power engineering facilities and processes therein, generalized models of process devices, limited mode models, partial topology models (nodal models), shells for construction of process devices, integrated analysers of electric equipment, analytic software complexes and ACS.Based on detailed analysis of implementation of applied software tools in the field of simulator-building at power plants and network enterprises of Russia, substantiated conclusions are presented on the software products under consideration, which have positive references from customers and known for various reasons as “simulators”; these, though meeting the requirements stipulated by regulatory documents, do not feature to the full extent the properties necessary for full-fledged training, namely, full-scale applicability, compatibility with all modes and topological adequacy, which largely reduces the efficiency of their application in commercial operation.

Digital quantum simulation, Trotter errors, and quantum chaos of the kicked top

This work aims at giving Trotter errors in digital quantum simulation (DQS) of collective spin systems an interpretation in terms of quantum chaos of the kicked top. In particular, for DQS of such systems, regular dynamics of the kicked top ensures convergence of the Trotterized time evolution, while chaos in the top, which sets in above a sharp threshold value of the Trotter step size, corresponds to the proliferation of Trotter errors. We show the possibility to analyze this phenomenology in a wide variety of experimental realizations of the kicked top, ranging from single atomic spins to trapped-ion quantum simulators which implement DQS of all-to-all interacting spin-1/2 systems. These platforms thus enable in-depth studies of Trotter errors and their relation to signatures of quantum chaos, including the growth of out-of-time-ordered correlators.

Impedance Modeling and Stability Analysis of the Converters in a Double-Fed Induction Generator (DFIG)-Based System

Harmonic stability of double-fed induction generators (DFIGs) now has become a significant topic because of its harmful impact on power quality issues of the system. Since the double pulse width modulation (PWM) converter is one of the main harmonic sources in DFIGs, it may cause harmonic instability with increasing harmonic contents. Thus, the modeling and stability analyses of PWM converters in DFIGs are essential steps to assess the harmonic stability of DFIGs. Aiming at dual PWM converters, which include the grid side converter (GSC) and the rotor side converter (RSC), this paper divides converters into two parts: circuit modules and control modules. Closed-loop input impedance models of each module are then derived by means of transfer functions. Hence, the stability of the system can be readily predicted through Nyquist diagrams. The contributions of parameters to the system’s harmonic stability are also identified. Finally, time-domain simulations are conducted in a real-time digital simulation (RTDS) system. Simulation results confirm that the established impedance model can effectively reveal the stability of the DFIG-based system and can give critical conditions for the occurrence of harmonic instability.

Voltage Support under Grid Faults with Inherent Current Limitation for Three-Phase Droop-Controlled Inverters

A novel nonlinear current-limiting controller for three-phase grid-tied droop-controlled inverters that is capable of offering voltage support during balanced and unbalanced grid voltage drops is proposed in this paper. The proposed controller introduces a unified structure under both normal and abnormal grid conditions operating as a droop controller or following the recent fault-ride-through requirement to provide voltage support. In the case of unbalanced faults, the inverter can further inject or absorb the required negative sequence real and reactive power to eliminate the negative sequence voltage at the point of common coupling (PCC) whilst ensuring at all times boundedness for the grid current. To accomplish this task, a novel and easily implementable method for dividing the available current into the two sequences (positive and negative) is proposed, suitably adapting the proposed controller parameters. Furthermore, nonlinear input-to-state stability theory is used to guarantee that the total grid current remains limited below its given maximum value under both normal and abnormal grid conditions. Asymptotic stability for any equilibrium point of the closed-loop system in the bounded operating range is also analytically proven for first time using interconnected-systems stability analysis irrespective of the system parameters. The proposed control concept is verified using an OPAL-RT real-time digital simulation system for a three-phase inverter connected to the grid.

Research on current‐mode damping impedance interface model based on adaptive impedance matching

With the development and progress of new energy electricity generation technology, a detailed study and test is required on new energy power generation equipment and micro-network system. As of the advantage of both numerical simulation and physical simulation, power connection type digital physical mixed simulation system could accomplish such research and tests. The simulation interface is the key to realise hybrid simulation. This paper proposes a current-mode damping impedance interface model based on adaptive impedance matching. The model is analysed from the interface stability, the accuracy and the dynamic response ability according to the structure of the interface model. Both theoretical analysis and simulation results show that current-mode damping impedance interface model based on adaptive impedance has high stability and accuracy, and also good dynamic response capability.

A New Differential Backup Protection Strategy for Smart Distribution Networks: A Fast and Reliable Approach

The integration of distributed generations (DGs) is transforming the traditional radial single-source distribution system into a complex multi-source one which requires its related protection is able to maintain proper coordination under bidirectional power flow conditions. Although the conventional backup protection methods are effective up to a certain level of DG penetration, they are incompetent for higher service demands such as high DG penetration and protective rapidity. To deal with such a problem, a fast and reliable backup protection strategy is presented on the basis of a proposed device detection method. In the proposed backup strategy, the device failure-related backup protection is started in advance to accelerate the fault isolation by locking the failed primary protection which can be predicted by the proposed device detection method. The presented strategy possesses an excellent performance on rapidity and stability. Particularly, the fault isolation area is only expanded to the upper level circuit breaker via our protection strategy. The performance of the proposed backup strategy has been validated by the realistic system and the real-time digital simulator (RTDS) system.

A distributed decision method for missiles autonomous formation based on potential game

The distributed cooperative decision problems of missiles autonomous formation with network packet loss are investigated by using the potential game based on formation principles. In particular, a dynamic target allocation method for missiles formation is provided based on the potential game and formation principles, after the introduction of cooperative guidance and control system of the missiles formation. Then we seek the optimization of a global utility function through autonomous missiles that are capable of making individually rational decisions to optimize their own utility functions. The first important aspect of the problem is to design an individual utility function considering the characteristics of the missiles formation, with which the objective of the missiles are localized to each missile yet aligned with the global utility function. The second is to equip the missiles with an appropriate coordination mechanism with each missile pursuing the optimization of its own utility function. We present the design procedure for the utility, and present a coordination mechanism based on spatial adaptive play and then introduce the idea of “cyclical selected spatial adaptive play” and “negotiation based on time division multiple address (TDMA) protocol formation support network”. Finally, we present simulations for the distributed dynamic target allocation on the comprehensive digital simulation system, and the results illustrate the effectiveness and engineering applicability of the method.

Research on application of FDNE based on RTDS and comparison analysis of fault transient of Shanghai Sijing power grid

As a most widely applied real-time digital simulation system, real time digital simulation (RTDS) is however quite limited on scale of simulation by the number of hardware purchased. Through frequency-dependent network equivalent (FDNE), scale of simulation of RTDS could be largely increased by frequency equivalent on limited hardware. Based on basic principles of FDNE, function limitations and problem are analysed, taking the Shanghai Sijing district power grid as an example; detailed simulation model and FDNE equivalent module are built, transient characteristics under faults before and after FDNE equivalent are analysed. Furthermore, the fault characteristics of high-voltage direct current (HVDC)-Sijing power grid is also studied, which provides a realistic means for real-time digital simulation of AC–HVDC hybrid power grid with limited hardware of RTDS.

The impacts of ergonomics/human factors of wheelchair/user combinations on effective barrier-free environments design: A case study of the Chinese universal rail coach layout

Adequate barrier-free environments for all people have become a pressing concern in several societies. This paper explores the riding tasks, key riding motions, routes, and impacts of other passengers on wheelchair users traveling by rail as well as typical riding therbligs to support the development of universal rail coach layouts appropriate ways to evaluate their efficacy. We present 3 studies. The first examines 15 typical riding therbligs of wheelchair/user combinations obtained through experiments and behavioral observation; the second focuses on 15 segments and 9 electromyograms of typical riding therbligs obtained from motion capture and electromyography experiments; the third used 15 typical riding therbligs of wheelchair/user combinations and modeled them in digital human model simulation systems. In all three studies both wheelchair and wheelchair user characteristics were examined. The subsequent analyses determined that the ideal barrier-free environment with an all-inclusive design demanded no instrumental or service auxiliary elements because users were able to accomplish all tasks with ease. Moreover, the research showed that a universal rail coach layout should provide a unified design of functional and reversible routes for the wheelchair/user combinations to move within the space, strive for the reduction of the entire distances that wheelchair/user combinations must travel, minimize the physical effort required to perform typical riding therbligs. Additionally, the 3D design scheme should match the typical digital riding therbligs. Finally, we summarized the key aspects recommended for Chinese universal rail coach layout and proposed two layout schemes. Findings from these studies may provide useful guidelines and suggestions for layout design of universal rail coaches.

RESEARCH ON THE DIGITAL SIMULATION FOR THE WHOLE PROCESS OF MARS EXPLORATION

Abstract. China has paid considerable attention to space exploration and made great strides in the field. The first Chinese Mars Exploration Mission will be carried out in 2020. Digital simulation has been proved to be an effective and efficient means for planning and deduction in many fields. Thus, it was introduced for the Mars exploration in this paper and key technologies was researched above three aspects. First of all, complicated time-space benchmark was combed to support the interplanetary simulation. Secondly, the multi-resolution pyramid model and indexing strategy were adopted to preprocess the geographical environment data, which ensured the efficiency of data loading, browsing, and querying. Then, the activity objects were abstracted and modelled based on four aspects, including property, ephemeris, geometry, and behavior. Therefore, a digital simulation system, called Sino-Mars, was developed. The architecture of Sino- Mars consists of five layers, including data collection, data processing, scenario modelling, visualization and application layer. Using the Chinese Mars Exploration Mission slated for 2020 as an example, we demonstrated the capabilities of Sino-Mars for data integration, visualization, process deduction, and auxiliary analysis.

Power quality assessment and event detection in hybrid power system

Renewable energy (RE) sources when integrated to utility network to form hybrid power system pose challenges in terms of stability and power quality. A method based on Stockwell's transform (S-transform) is presented in this paper for power quality (PQ) assessment and detection of islanding, outage and grid synchronization of renewable energy sources. Voltage signals are decomposed using multi-resolution analysis (MRA) of S-transform and features extracted are realized to assess the power quality disturbances associated with various events. Operational events are detected with the help of features extracted from the S-transform based decomposition of negative sequence component of voltage. A power quality index is proposed to rank the various operational events based on power quality. Proposed algorithm has been tested successfully on IEEE-13 bus test system with necessary modifications to integrate wind and solar PV generators to form the hybrid power system. Simulation results are validated in real time environment with the help of real time digital simulation (RTDS) system.

Coordinated secondary control for autonomous hybrid three-port AC/DC/DS microgrid

This paper presents a coordinated secondary control (CSC) strategy for distributed power management for an autonomous hybrid three-port AC/DC/DS microgrid. The proposed CSC is on top of a generalized primary control (GPC), which consists of local power sharing (LPS) control within an individual AC or DC subgrid, global power sharing (GPS) control throughout the AC/DC subgrids, and storage power sharing (SPS) control in a distributed storage (DS) network. The CSC along with the GPC uses the local frequency/voltage deviations and offers decentralized power management with enhanced overall reliability. To eliminate the inherent frequency/voltage deviations in GPC and restore to their nominal values, a secondary control is normally applied to all distributed generators (DGs), which would degrade the performance of decentralized power management. To overcome this concern, a CSC strategy is proposed to concurrently restore frequency/voltage and re-establish a distributed power management by means of limited information exchange through the low-bandwidth communication links. The proposed control scheme has been verified by both simulations and controller hardware-in-the-loop (CHIL) experiments in an OPAL-RT digital simulator system.

Measuring the reliability of a natural gas refrigeration plant: Uncertainty propagation and quantification with polynomial chaos expansion based sensitivity analysis

The practical quantification of a model's ability to describe information is extremely important for the practical estimation of model parameters. Hence, in this study, a complex sweet natural gas refrigeration chemical process was selected for uncertainty quantification (UQ) and sensitivity analysis (SA). A computer code was generated to create a hybrid digital simulation system (HDSS) to connect two commercially important software programs, namely Matlab and Aspen Hysys. Monte Carlo (MC) and Halton based quasi-MC (QMC) methods were used for uncertainty propagation (UP) and uncertainty quantification (UQ). A surrogate model based on the polynomial chaos expansions (PCE) approach was applied for SA. Sobol′ sensitivity indices were evaluated to identify influential input parameters. The proposed PCE methodology was compared with a traditional MC based approach to illustrate its advantages in terms of computational efficiency and acceptable accuracy. The results indicated that UQ and SA help in an in-depth understanding of the chemical process determining the feasibility and improving the operation based on reliability and consumer demands. This study used in the robust design by evaluating the bounds and reliability based on confidence levels and thereby increasing the reliance of the process at hand.

Harmonic Analyzing of the Double PWM Converter in DFIG Based on Mathematical Model

Harmonic pollution of double fed induction generators (DFIGs) has become a vital concern for its undesirable effects on power quality issues of wind generation systems and grid-connected system, and the double pulse width modulation (PWM)converter is one of the main harmonic sources in DFIGs. Thus the harmonic analysis of the converter in DFIGs is a necessary step to evaluate their harmonic pollution of DFIGs. This paper proposes a detailed harmonic modeling method to discuss the main harmonic components in a converter. In general the harmonic modeling could be divided into the low-order harmonic part (up to 30th order) and the high-order harmonic part (greater than order 30) parts in general. The low-order harmonics are produced by the circuit topology and control algorithm, and the harmonic component will be different if the control strategy changes. The high-order harmonics are produced by the modulation of the switching function to the dc variable. In this paper, the low-order harmonic modeling is established according to the directions of power flow under the vector control (VC), and the high-order harmonic modeling is established by the switching function of space vector PWM and dc currents. Meanwhile, the simulations of harmonic a components in a converter are accomplished in a real time digital simulation system. The results indicate that the proposed modeling could effectively show the harmonics distribution of the converter in DFIGs.

PART2: using adaptive resonance theory for web caching prefetching

As the Web becomes the major source for information and services, fast access to relevant Web objects is a critical requirement for many applications. Various methods have been developed to achieve this goal. Web page prefetching is a commonly used technique that is highly effective in reducing user perceived delays. In this paper, we propose a new prefetching model pART2, which is based on the adaptive resonance theory (ART) for data clustering. A corresponding cache replacement policy (Probability-Based Replacement) is also proposed and developed. The new policy matches with the prefetching scheme and therefore produces a higher cache hit ratio compared with some of the traditional algorithms. To evaluate the new model, we conduct a series of experiments using data sets collected from a digital library system and Monte Carlo simulation techniques. Sensitivity of the parameters and statistical analysis are also presented. The proposed model using ART-type networks provides a promising avenue for constructing accurate caching prefetching systems that are flexible and adaptive.

Key techniques in real time digital simulation for closed-loop testing of HVDC systems

This paper introduces several key techniques in realtime digital simulation for closed-loop testing of high voltage direct current (HVDC) systems, including line commutated converter (LCC) HVDC valve group models, modular multilevel converter (MMC) HVDC models, phase domain frequency dependent transmission line models, and switchable filter models. Various issues such as background, algorithms, implementations, applications, and validation of these models are introduced. These techniques represent the most advanced technology in modelling HVDC systems on a real time simulator. The models have been implemented on the RTDS Simulator, a comprehensive real time power system digital simulation tool.

Research on Intercepting Strategy of Multiple Kill Vehicle in Midcourse Defense Based on Multi-Sensors Fusion Method

The multiple kill vehicle (MKV) interceptor consists of a carrier vehicle and some small kill vehicles which can intercept multiple targets independently. According to the mission of midcourse interception for multiple warheads of long-range ballistic missile, this paper focused on the design and optimization of cooperative detection and guidance strategy. Based on multi-sensors fusion technology, the method of high-accuracy position measurement and view expansion of infrared sensors are proposed. The terminal guidance law is analyzed based on the data obtained by the methods. A digital real-time simulation system is developed to verify the feasibility of the method.

Analysis and Simulation of Multi-target Echo Signals from a Phased Array Radar

The construction of digital radar simulation systems has been a research hotspot of the radar field. This paper focuses on theoretical analysis and simulation of multi-target echo signals produced in a phased array radar system, and constructs an array antenna element and a signal generation environment. The antenna element is able to simulate planar arrays and optimizes these arrays by adding window functions. And the signal environment can model and simulate radar transmission signals, radar internal noise, clutter and jamming signals. These signals are combined linearly to generate the radar echo signal. The simulation results indicate that multi-target echo signals are completely overwhelmed by other signals, satisfying the needs of subsequent signal processing and data processing.

A Novel Cloud-Based Platform for Implementation of Oblivious Power Routing for Clusters of Microgrids

There has been an increasing demand for connectivity of the clusters of microgrids to increase their flexibility and security. This paper presents a framework for implementation, simulation, and evaluation of a novel power routing algorithm for clusters of microgrids. The presumed cluster is composed of multiple direct current (dc) microgrids connected together through multi-terminal dc system in a meshed network. In this structure, the energy is redirected from the microgrid with excessive power generation capacity to the microgrid which has power shortage to supply its internal loads. The key contribution of this paper is that each microgrid in the cluster is unaware of the current state and other flows of the cluster. In this approach, the optimal power flow problem is solved for the system while managing congestion and mitigating power losses. The proposed methodology works for both radial and non-radial networks regardless of the network topology, scale, and number of microgrids involved in the cluster. Therefore, it is also well suited for large-scale optimal power routing problems that will emerge in the future clusters of microgrids. The effectiveness of the proposed algorithm is verified by MATLAB simulation. We also present a comprehensive cloud-based platform for further implementation of the proposed algorithm on the OPAL-RT real-time digital simulation system. The communication paths between the microgrids and the cloud environment can be emulated by OMNeT++.