Modeling and real‐time simulation of UPFC

We have developed a digital real‐time simulator of Power Electronics Controllers, so‐called FACTS (Flexible AC Transmission Systems) Controllers and/or Custom Power by using MATLAB^TM/SIMULINK^TM and dSPACE^TM System. This paper describes the modeling and the calculation accuracy of a UPFC (Unified Power Flow Controller) model. Hence, the developed simulator operates at a large time step, in order to improve simulation accuracy, a correction processing of the switching delay is implemented into the UPFC model. Calculation accuracy of the real‐time UPFC model is at the same level as EMTDC^TM results. We confirm stable operation of the developed UPFC model by connecting a commercial real‐time digital simulator (RTDS^TM). © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 155(1): 19–26, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20200     

Studies on the method of combining an analog simulator and a real‐time digital simulator for power system analysis

An advanced real‐time power system simulator consisting of a conventional real‐time analog simulator and a real‐time digital simulator has been developed. EMTP simulations were carried out to verify the advanced power system simulator concept and to evaluate the effects of various parameters. A prototype of the advanced power system simulator using the Bergeron method was tested. The test results confirmed the feasibility of the real‐time power system simulator. © 2001 Scripta Technica, Electr Eng Jpn, 136(3): 49–57, 2001     

Implementation of the symmetric doped double‐gate MOSFET model in Verilog‐A for circuit simulation

Recently we developed a model for symmetric double‐gate MOSFETs (SDDGM) that, for the first time, considers the doping concentration in the Si film in the complete range from 1×10¹⁴ to 3×10¹⁸ cm⁻³. The model covers a wide range of technological parameters and includes short channel effects. It was validated for different devices using data from simulations, as well as measured in real devices. In this paper, we present the implementation in Verilog‐A code of this model, which allows its introduction in commercial simulators. The Verilog‐A implementation was optimized to achieve reduction in computational time, as well as good accuracy. Results are compared with data from 2D simulations, showing a very good agreement in all transistor operation regions. Copyright © 2009 John Wiley & Sons, Ltd.     

Real-Time Implementation of a STATCOM on a Wind Farm Equipped With Doubly Fed Induction Generators

Voltage stability is a key issue to achieve the uninterrupted operation of wind farms equipped with doubly fed induction generators (DFIGs) during grid faults. This paper investigates the application of a static synchronous compensator (STATCOM) to assist with the uninterrupted operation of a wind turbine driving a DFIG, which is connected to a power network, during grid faults. The control schemes of the DFIG rotor- and grid-side converters and the STATCOM are suitably designed and coordinated. The system is implemented in real-time on a real time digital simulator. Results show that the STATCOM improves the transient voltage stability and therefore helps the wind turbine generator system to remain in service during grid faults.     

An application of Q‐value‐based dynamic programming with Boltzmann distribution to real‐world road networks

In order to alleviate traffic congestion and improve the efficiency of traffic systems from a global perspective, a dynamic traffic management model is proposed in this paper. The proposed model is applied to the large‐scale microscopic simulator SOUND/4U based on the real‐world road network of Kurosaki, Kitakyushu, Japan. All the vehicles in the simulator follow the direction from the route guidance of the dynamic traffic management model, in which the extended Q‐value‐based dynamic Programming with Boltzmann distribution (QDP‐BD) and the time‐varying traffic information are used to generate the routes from the origins to the destinations. The simulation results show that the proposed QDP‐BD can reduce traffic congestion and improve the efficiency of the whole traffic system effectively compared with the greedy method in the real‐world road network. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Development of a voltage sag detection method for nonutility generation systems

This paper deals with a new detection method based on three‐phase vector operation for voltage sag. The detection method is applicable to a protection system using a high‐speed interruption system which protects distributed generators and critical loads in a customer's facility. The algorithm and merits of this method are explained in detail. The detection characteristics are then analyzed using the ATP (Alternative Transients Program) and are confirmed using a real‐time digital simulator, and it is shown that the method is useful for detecting voltage sag. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(4): 34–41, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20117     

Real-time digital simulation of power electronics systems with Neutral Point Piloted multilevel inverter using FPGA

Most of actual real time simulation platforms have practically about ten microseconds as minimum calculation time step, mainly due to computation limits such as processing speed, architecture adequacy and modeling complexities. Therefore, simulation of fast switching converters’ instantaneous models requires smaller computing time step. The approach presented in this paper proposes an answer to such limited modeling accuracies and computational bandwidth of the currently available digital simulators.As an example, the authors present a low cost, flexible and high performance FPGA-based real-time digital simulator for a complete complex power system with Neutral Point Piloted (NPP) three-level inverter. The proposed real-time simulator can model accurately and efficiently the complete power system, reducing costs, physical space and avoiding any damage to the actual equipment in the case of any dysfunction of the digital controller prototype. The converter model is computed at a small fixed time step as low as 100 ns. Such a computation time step allows high precision account of the gating signals and thus avoids averaging methods and event compensations. Moreover, a novel high performance model of the NPP three-level inverter has also been proposed for FPGA implementation. The proposed FPGA-based simulator models the environment of the NPP converter: the dc link, the RLE load and the digital controller and gating signals. FPGA-based real time simulation results are presented and compared with offline results obtained using PLECS software. They validate the efficiency and accuracy of the modeling for the proposed high performance FPGA-based real-time simulation approach. This paper also introduces new potential FPGA-based applications such as low cost real time simulator for power systems by developing a library of flexible and portable models for power converters, electrical machines and drives.     

A 6.6‐kV transformerless cascade PWM STATCOM. Experimental verification by a three‐phase 200‐V, 10‐kVa laboratory system

This paper deals with a 6.6‐kV transformerless STATCOM cascading multiple single‐phase H‐bridge PWM converters in each phase. The AC voltage of the STATCOM is almost sinusoidal, so that it requires no harmonic filter. Each converter is equipped with a capacitor and a voltage sensor on the DC side, which are electrically isolated from each other. The STATCOM has the capability of self‐starting and voltage‐balancing without any external power supply or equipment. Experiments using a three‐phase 200‐V, 10‐kVA laboratory system, along with computer simulations, are carried out to confirm the viability and effectiveness of the STATCOM. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 170(1): 55–64, 2010; Published online in Wiley InterScience ( www.interscience.wiley. com ). DOI 10.1002/eej.20822     

Realization of arbitrary current transfer functions based on commercially available CCII + s

In this paper, a new topology for realizing arbitrary n^th‐order current transfer function (TF), consisting of only plus‐type second‐generation current conveyors (CCII+s), is suggested. The proposed TF simulator employs only grounded capacitors and is free from the passive element matching requirements. The developed TF simulator can be constructed directly with commercially available active components such as AD844s. It has low‐input and high‐output impedances, a feature which makes it fully cascadable with other current‐mode topologies. Moreover, the proposed simulator can provide gain at its outputs. Simulation and experimental test results for various filter examples are included to confirm the claimed theory. Copyright © 2012 John Wiley & Sons, Ltd.     

A new modeling approach for circuit‐field‐coupled time‐stepping electromagnetic analysis of saturated interior permanent magnet synchronous motors

This paper proposes a new modeling approach for circuit‐field‐coupled time‐stepping electromagnetic analysis of a saturated interior permanent magnet synchronous motor (IPMSM). To predict the drive performance quickly, the proposed approach consists of a dynamic simulator based on a new analytical model of the d‐ and q‐axis magnetization characteristics (λ‐i_d‐i_q‐θ). The model can take into account not only cross‐saturation but also the harmonics of the inductance distributions and EMF waveforms. The validity of the model is verified from suitable simulation results for the instantaneous current and torque waveforms of the IPMSM. The proposed analysis leads to a dramatic reduction in the computation time compared to circuit‐field‐coupled time‐stepping FEA, while maintaining analytical accuracy. The effectiveness of the proposed method is experimentally verified using a 10‐kW, 15,000‐rpm concentrated‐winding IPM motor. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 174(1): 49–58, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21024     

Wide‐band modelling of CMOS interconnections and voiding damages with the lumped element LE‐FDTD method

This paper illustrates the application of a lumped element‐finite difference time domain (LE‐FDTD) simulator to the wide‐band modelling of CMOS interconnections. To achieve very accurate results the short‐open calibration (SOC) technique has been adopted. Specific parameters of a CMOS interconnection laterally screened by a stack of metal vias have been extracted in the two cases of an unperturbed and a purposely damaged metal line. The behaviour of void‐like defects in the metal line has been also studied using the fully three‐dimensional capabilities of the simulator. It has been demonstrated that, at least in the simulated cases, only the specific resistance is affected by damaging. Copyright © 2004 John Wiley & Sons, Ltd.     

Drain current model of double‐gate MOSFETs considering both electrons and holes

We present a rigorously derived current solution for undoped double‐gate (DG) MOSFETs with two carriers, which is based on surface potentials. The third‐order Newton–Raphson (NR) method is used to solve the surface‐potential equations resulting from the application of the boundary conditions to the general Poisson solution, with an initial guess very close to the true solution. The results demonstrate surface‐potential solutions for DG MOSFETs with 2–7 iterations to achieve an accuracy of 10⁻¹⁵. The drain current model for two carriers is presented as a benchmark to test the accuracy of one‐carrier current approximation. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Fault diagnosis of a simulated industrial gas turbine via identification approach

In this paper, a model‐based procedure exploiting the analytical redundancy principle for the detection and isolation of faults on a simulated process is presented. The main point of the work consists of using an identification scheme in connection with dynamic observer and Kalman filter designs for diagnostic purpose. The errors‐in‐variables identification technique and output estimation approach for residual generation are in particular advantageous in terms of solution complexity and performance achievement. The proposed tools are analysed and tested on a single‐shaft industrial gas turbine MATLAB/SIMULINK^® simulator in the presence of disturbances, i.e. measurement errors and modelling mismatch. Selected performance criteria are used together with Monte‐Carlo simulations for robustness and performance evaluation. The suggested technique can constitute the design methodology realising a reliable approach for real application of industrial process FDI. Copyright © 2006 John Wiley & Sons, Ltd.     

Discrete‐time model following control of inverter with rectifier load

Electronic apparatus, such as a computer, are a capacitor input type rectifier load for the power supply. The rectifier load causes distortions of the power source voltage waveform. Copyright © 2004 Wiley Periodicals, Inc. This paper describes the output voltage characteristic of the single phase PWM inverter controlled by a discrete‐time model following method and connected to a rectifier load. First, the rectifier load model of a discrete‐time system is considered. Next, the discrete‐time model following control system used for this load is described. Then, simulation and experimental results are examined. The simulation results show that this method has robustness to the load change. The experimental system consists of an inverter controlled by a digital signal processor (DSP) and a rectifier load. Experimental results confirmed the validity of the simulation result. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(2): 72–81, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20375     

A 0.008‐mm2, 35‐μW, 8.87‐ps‐resolution CMOS time‐to‐digital converter using dual‐slope architecture

This paper presents a high resolution time‐to‐digital converter (TDC) for low‐area applications. To achieve both high resolution and low circuit area, we propose a dual‐slope voltage‐domain TDC, which is composed of a time‐to‐voltage converter (TVC) and an analog‐to‐digital converter (ADC). In the TVC, a current source and a capacitor are used to make the circuit as simple as possible. For the same reason, a single‐slope ADC, which is commonly used for compact area ADC applications, is adapted and optimized. Because the main non‐linearity occurs in the current source of the TVC and the ramp generator of the ADC, a double gain‐boosting current source is applied to overcome the low output impedance of the current source in the sub‐100‐nm CMOS process. The prototype TDC is implemented using a 65‐nm CMOS process, and occupies only 0.008 mm². The measurement result shows a dynamic range with an 8‐bit 8.86‐ps resolution and an integrated non‐linearity of ±1.25 LSB. Copyright © 2016 John Wiley & Sons, Ltd.     

Physically based 2D compact model for power bipolar devices

The two‐dimensional (2D) physical compact model for advanced power bipolar devices such as injection enhanced gate transistor (IEGT) or Trench IGBT is presented in this paper. In order to model the complex 2D nature of these devices the ambipolar diffusion equation has been solved simultaneously for different boundary conditions associated with different areas of the device. The IEGT compact model has been incorporated into the SABER simulator and tested in standard double‐pulse switching test circuit. The compact model has been established to model a 4500V‐1500A flat pack TOSHIBA IEGT. Copyright © 2004 John Wiley & Sons, Ltd.     

Formation and properties of nitrogen‐rich phases in austenitic stainless steel by plasma‐based ion implantation

Surface modification of austenitic stainless steel by plasma‐based ion implantation at elevated temperatures below 450°C has been studied experimentally. The nitrogen depth profile at room temperature was similar to that obtained by TRIM code simulation, but the depth of nitrogen penetration increases with target temperature and reaches a few micrometers at a treatment condition of 450°C and an implantation time of 2 h. High‐dose nitrogen implantation exceeding 10¹⁸ cm^?2 at temperatures above 350°C results in the formation of expanded austenite phase (supersaturated f.c.c. phase) with little CrN precipitation, leading to remarkable enhancement of surface hardness without loss of corrosion resistance. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(4): 9–16, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10340     

Representation,methods, and circuits for time‐based conversion and computation

In this paper, we present an efficient representation of the analog signal using the inter‐pulse interval (IPI) time. Based on this representation, methods and circuits for conversion and computation have been developed. To validate these methods and circuits, a test chip has been fabricated using a 0.35µm mixed‐signal CMOS process. Together, the circuits occupy 59.52 × 10^?3mm² of chip area and consume 8.8 mW of power from a 3.2 V supply. Test results at 10 MHz and simulations results at 100 MHz show good accuracy over ±600mV range. Copyright © 2010 John Wiley & Sons, Ltd.     

The surface charging effects in three‐dimensional simulation of the profiles of plasma‐etched nanostructures

Particles and fields represent two major modeling paradigms in pure and applied science at all. Particles typically exist in a spatial domain and they may interact with other particles or with field quantities defined on that domain. A field, on the other hand, defines a set of values on a region of space. In this paper, a methodology and some of the results for three‐dimensional (3D) simulations that includes both field and particle abstractions are presented. In our studies, charging damage to a semiconductor structure during plasma etching is simulated by using 3D level set profile evolution simulator. The surface potential profiles and electric field for the entire feature were generated by solving the Laplace equation using finite elements method. Calculations were performed in the case of simplified model of Ar⁺/CF₄ non‐equilibrium plasma etching of SiO₂. Copyright © 2010 John Wiley & Sons, Ltd.     

A cascade‐connected neural model for improved 2D DOA estimation of an EM signal

This article proposes a neural network‐based approach to increase accuracy of two‐dimensional direction of arrival (DOA) estimation of an electromagnetic signal. The proposed method combines two neural networks developed using simulated and small amount of empirical data, respectively. The output of the simulation‐based neural network represents approximate information on DOAs. It is then considered as a priori knowledge for the small empirical network that is crucial for obtaining more accurate DOA estimates. The developed cascade‐connected model is validated using real data from a rectangular antenna array. Improvements in terms of accuracy and reliability are obtained and compared with the MUSIC algorithm. Copyright © 2015 John Wiley & Sons, Ltd.