Entire Operating Region Research Articles

Online Multi-Parameter Observation of IPM Machine With Reconstructed Nonlinear Small-Signal Model Based on Dual EKF

Flux nonlinearity due to cross-coupling saturation is critical for interior permanent magnet (IPM) machine control. To obtain accurate parameters in real-time, this paper proposes a novel reconstructed nonlinear small-signal model which simplifies the observability analysis and design of the observer. Compared with traditional methods, the observability of the reconstructed small-signal model shows that all resistance and inductance parameters are observable under entire operation region. The flux cross-coupling saturation is also well considered. A Dual-Extended-Kalman-Filter (DEKF) based observer for the reconstructed model is introduced to achieve fast parameters convergence. The effectiveness of the proposed observer is experimentally evaluated with a 60kW IPM machine and verified by finite element analysis (FEA).

Fuzzy Gain Scheduling of the Fractional-Order PID Controller for a Continuous Stirred-Tank Reactor Process

In most chemical industries, continuous stirred-tank reactors (CSTRs) are essential for the production of chemicals. The CSTR process is highly nonlinear and has both stable and unstable equilibrium points. Control system engineers face a difficult issue when designing a single controller for temperature control in both stable and unstable areas. Due to these problems, implementing the conventional proportional-integral-derivative (PID) controller may lead to instability in controlled variables. Therefore, in this paper, the entire operating region is divided into three regions. The fractional-order PID controller as a local controller is designed in each operating region to control the temperature, and its parameters are tuned with a genetic algorithm by minimizing the integral of absolute error and control input change with a weighting factor. Then, a fuzzy gain scheduling scheme based on the Tagaki-Sugno fuzzy model is used to properly interpolate the outputs of the local controllers. A set of simulations are carried out to demonstrate the effectiveness of the proposed controller, and its performance is compared with that of an adaptive nonlinear controller and fuzzy gain scheduling of the PID controller.

Finding the LQR Weights to Ensure the Associated Riccati Equations Admit a Common Solution

This paper addresses the problem of finding the linear quadratic regulator (LQR) weights such that the associated discrete-time algebraic Riccati equations admit a common optimal stabilising solution. Solving such a problem is key to designing LQR controllers to stabilise discrete-time switched linear systems under arbitrary switching, or stabilise polytopic systems (e.g., Takagi-Sugeno fuzzy systems and linear parameter varying systems) in the entire operating region. To ensure problem tractability and reduce the searching space, this paper proposes an efficient framework of finding only the state weights based on the given input weights. Linear matrix inequality conditions are derived to conveniently check feasibility of the problem. An iterative algorithm with quadratic convergence and low computational complexity is developed to solve the problem. Efficacy of the proposed method is illustrated through numerical simulations of systems with various sizes.

A Low Q Three-Phase Series Resonant Converter for PV Applications

In this paper, a soft-switched three-phase resonant converter with a low quality factor (Q) design is proposed for Photovoltaic (PV) energy harvesting systems with a very wide range of operating conditions. Due to the low quality factor (Q ≤ 1), the voltage stress across the capacitors is drastically reduced. However, a major challenge of using a low Q design is the wide switching frequency range required for operation over a wide range of load and input conditions. In order to reduce the switching frequency range, this paper introduces a hybrid modulation technique employing asymmetric pulse width modulation (APWM) along with variable frequency modulation. The proposed modulation scheme also substantially extends the soft-switching range of the converter from full-load upto 10–35% load condition over a wide range of line voltages. To sustain soft-switching in the entire operating region of the converter, the converter is operated in a hybrid structure with single-phase and burst modes at light load conditions. A comprehensive time-domain analysis of the proposed converter is presented, which greatly improves accuracy over conventional frequency-domain modeling. Experimental results from a 1 kW prototype are presented to verify the performance of the converter and validate the theoretical analysis.

A monopole polarisation diversity antenna for high density packaging MIMO applications

Purpose This paper aims to propose a single element, dual feed, polarisation diversity antenna. The proposed antenna operates from 2.9 to 10.6 GHz for covering the entire ultra-wideband (UWB) frequency range. The antenna is designed for usage in massive multiple input multiple output (MIMO) and closed packaging applications. Design/methodology/approach The size of the antenna is 24 × 24 × 1.6 mm3. The radiating element of the antenna is derived from the Sierpinski–Knopp (SK) fractal geometry for miniaturization of the antenna size. The antenna has a single reflecting stub placed between the two orthogonal feeds, to improve isolation. Findings The proposed antenna system exhibits S11 < −10 dB, S21 < −15 dB and stable radiation characteristics in the entire operating region. It also offers an envelope correlation coefficient < 0.01, a diversity gain > 9.9 dB and a capacity loss < 0.4 bps/Hz. The simulated and measured outputs were compared and results were found to be in similarity. Originality/value The proposed UWB-MIMO antenna has significant size reduction through usage of SK fractal geometry for radiating element. The antenna uses a single radiating element with dual feed. The stub is between the antenna elements which provide a compact and miniaturized MIMO solution for high density packaging applications. The UWB-MIMO antenna provides an isolation better than −20 dB in the entire UWB operating band.

Analytical approximation of surface potential and analysis of C–V characteristics of bulk MOSFETs at cryogenic temperatures

In this paper, we present an accurate analytical approximation of the surface potential for bulk MOSFETs, starting from its transcendental relation with respect to the gate voltage, valid from room temperature to deep cryogenic temperatures, encompassing the entire operating region. The results obtained from the proposed analytical model for the surface potential have very high accuracy, with the maximum absolute error of the order of nanovolts, when compared with the results of numerical calculations. We also investigate and present the temperature dependence of the semiconductor charge density and its physical implications on the C–V characteristics. A kink is observed in the C–V characteristics near flatband, due to dopant freeze-out at cryogenic temperatures. We have also been able to develop a model for the C–V characteristics, that captures this kink accurately, over a wide temperature range. The results obtained from this model are compared with both TCAD simulations as well as with experimental data, and the match is found to be excellent.

Speed Range Extension of Dual-Stator PM Machine Using Multi-Mode Winding Switching Strategy

In this paper, a novel winding switching (WS) strategy is proposed for the speed range extension of a dual-stator permanent magnet machine (DS-PMM), which can achieve simple and effective dynamic mode conversion over an entire operating region. Two types of WS circuits with an inverter and two switch groups were first designed to enable the winding reconfiguration of the machine, which could operate in three modes. The WS principle was then elucidated by introducing simplified equivalent circuits. Besides, the torque–speed curves of the machine under different operating modes were analyzed, based on the mathematical model. A speed-based WS controller was, subsequently, designed to generate the WS control signal and realize the multi-mode operation according to real-time operating conditions. The feasibility of the proposed WS strategy for extending the speed range of the DS-PMM was, finally, verified by experiments.

Selective Harmonic Elimination Technique for a 27-Level Asymmetric Multilevel Converter

In this paper, we present an implementation of selective harmonic elimination modulation technique in a 27-Level asymmetric multilevel converter. The main issue in this kind of converters is the generation of the gating patterns to obtain an optimized AC voltage waveform. State-of-the art solutions use deep mathematical analysis in the frequency domain by means of the Fourier series, but they are mainly applied for two-level or symmetric multilevel converters. On the other hand, the modulation for asymmetric multilevel converters is mainly focused on nearest level control or nearest vector control. In this work, we propose a novel modulating technique that takes advantage of the switching angles optimization for a 27-level waveform. In fact, different set of solutions are obtained and presented in order to define the modulation index as well as the value of the switching angles for the multilevel waveform. A modulation index sweep was performed for the entire operating region of the converter, where it can be observed that the number of levels decreases when the modulation index is low, which are calculated in order to minimize the total harmonic distortion (THD) of the resulting voltage waveform. In order to validate the proposal, these results for different modulation indexes values are simulated, obtaining a THD < 5% for a modulation index 0.75<M<1.0. Finally, a small scale proof-of-concept prototype is implemented in order to validate the proposal.

An Improved Voltage and Frequency Control for Islanded Microgrid Using BPF Based Droop Control and Optimal Third Harmonic Injection PWM Scheme

Droop control is commonly used for primary control of island microgrids at the expense of voltage deviations. Furthermore, voltage and frequency restoration can be achieved using droop control along with the communication line. However, system complexity increases and reliability decreases due to the communication delay and data loss. Also, overmodulated voltage source converters (VSCs) degrade the ac output in a converter-dominated islanded microgrid. In this article, an improved technique is proposed to control voltage and frequency for an islanded microgrid. The band-pass filter-based droop control (an equivalent secondary control without a communication line) is developed to control distributed inverters to enhance voltage and frequency regulation by reducing response time, overshoot, and steady-state error. Furthermore, a modified proportional integral derivative (MPID) controller is adopted for inner voltage and current loop control to handle the system response fluctuation subject to perturbation and eliminate further voltage quality deterioration. For optimal control action of MPID controller, the controller parameters are tuned using dynamic weighted salp swarm algorithm and validated by both bode plot and step response. Furthermore, an optimal third harmonic injection-sine pulsewidth modulation technique is proposed to reduce the harmonic generation for the entire operation region of the VSC. The proposed control technique is simulated in MATLAB Simulink, and its performance is compared with a state-of-the-art method. Also, the proposed control technique is validated on the OPAL-RT real-time simulator test bench. Investigation revealed that the proposed technique improved the voltage and frequency regulation and effectively minimized overshoots and steady-state errors of the system.

Modeling and Robust Coordinated Control of Turbocharged Natural Gas Engine with Genset Application

This paper describes a comprehensive framework for the development of a model-based robust coordinated control system, which is used to regulate the gas exchange processes of an advanced turbocharged natural gas engine with multifaceted control objectives. The natural gas engine involved in this study features a multi-input, multi-output structure and is highly-nonlinear. A robust coordinated control system is synthesized to realize desired performances of the engine over its entire operating region and is compared to a benchmark production control system in simulation. The comparison results explore the merits of coordinated control over decoupled control in the aspect of complex engine dynamics.

Novel Variable Switching Frequency PWM Strategy for a SiC-MOSFET-Based Electric Vehicle Inverter to Increase Battery Usage Time

In this study, a novel variable switching frequency pulse width modulation (VSFPWM) strategy is proposed to achieve improved electric vehicle inverter efficiency. The silicon carbide (SiC) MOSFET inverter has excellent switching characteristics, thus enabling pulse width modulation control with a high switching frequency. The high switching frequency can reduce the voltage ripples in DC-link capacitors, which enables their use at a reduced capacitance. The switching frequency is typically set to a level that is within the limits of the voltage ripple in the maximum output region. Given that the same switching frequency is applied to the entire operating region, there is a sufficient margin with respect to the limits of the voltage ripple in the low-to-medium output range. The proposed method is designed to consider the real-time minimum switching frequency by considering the voltage ripple of the capacitor during operation under loaded conditions, thereby minimizing the switching loss. In addition, the method is suitable for high-switching frequency control because the calculation time is short. Because it does not require additional hardware, it is easy to apply to the existing inverter. The validity of the proposed method was verified based on simulations and experiments.

Deep neural network model-based global calibration scheme for split injection control map to enhance the characteristics of biofuel powered engine

The work aims to optimally calibrate the diesel engine fuel injector control parameters powered by biofuel; it shows improved performance and emission behaviour for the entire operating region. Traditionally, these parameters are obtained through an enormous amount of trial and error experiments. To reduce these challenges, a new global model-based calibration scheme is proposed in this study for the development of optimum split injection control look-up map. The combinations of engine operating and control variable test conditions are framed through the I-optimal experimental design technique. Based on the experimentally measured responses, the response surface methodology (RSM) and deep neural network (DNN) estimation approaches are employed to set up a model between calibration parameters and the engine behaviour parameters. The multi-objective optimization using the desirability approach is carried in focus to equivalent importance of performance and emissions. The results showed that the DNN model has an excellent predictive performance than the RSM model. Therefore, based on the DNN model, the variation trend of the calibration parameters, the primary performance of the diesel and orange peel oil (20%) blend is examined. In comparison with the un-optimized map for OPO20 fuel, a simultaneous reduction of smoke and brake specific fuel consumption is achieved with a slight penalization in NOx emissions. The higher unsaturated hydrocarbons in OPO20 release higher smoke, it increases the injection pressure and timing advancement in the optimization process. The experimental validation of the optimized OPO20 map at 50% load improves the BTE of 14.06%. It also reduces the smoke to 85.67%, HC of 83.15%, CO of 11.3% and increases the NOX to 18.71% relative to the un-optimized map. The developed DNN model-based scheme can be used for any type of biofuel application to calibrate the split injection system lookup map aimed toward the engine performance and emission enhancement.

Drain Current Modeling of Tunnel FET using Simpson’s Rule

Tunnel Field Effect Transistor can be introduced as an emerging alternate to MOSFET which is energy efficient and can be used in low power applications. Due to the challenge involved in integration of band to band tunneling generation rate, the existing drain current models are inaccurate. A compact analytical model for simple tunnel FET and pnpn tunnel FET is proposed which is highly accurate. The numerical integration of tunneling generation rate in the tunneling region is performed using Simpson’s rule. Integration is done using both Simpson’s 1/3 rule and 3/8 rule and the models are validated against numerical device simulations. The models are compared with existing models and it is observed that the proposed models show excellent agreement with device simulations in the entire region of operation with Simpson’s 3/8 rule exhibiting the maximum accuracy.

Step length estimation with wearable sensors using a switched-gain nonlinear observer

This paper focuses on step length estimation using inertial measurement sensors. Accurate step length estimation has a number of useful health applications, including its use in characterizing the postural instability of Parkinson’s disease patients. Three different sensor configurations are studied using sensors on the shank and/or thigh of a human subject. The estimation problem has several challenges due to unknown measurement bias, misalignment of the sensors on the body and the desire to use a minimum number of sensors. A nonlinear estimation problem is formulated that aims to estimate shank angle, thigh angle, bias parameters of the inertial sensors and step lengths. A nonlinear observer is designed using Lyapunov analysis and requires solving an LMI to find a stabilizing observer gain. It turns out that global stability over the entire operating region can only be obtained by using switched gains, one gain for each piecewise monotonic region of the nonlinear output function. Experimental results are presented on the performance of the nonlinear observer and compared with gold standard reference measurements from an infrared camera capture system. An innovative technique that utilizes three sensors is shown to provide a step length accuracy nearly equal to that of the four-sensor configuration.

Fuzzy modeling and control of a class of non‐differentiable multi‐input multi‐output nonlinear systems

AbstractThis paper presents a new approach in modeling and control of multi‐input multi‐output (MIMO) systems that have non‐differentiable operating points. A circle criterion is introduced at the non‐differentiable operating points to divide the entire operating region into two parts. Takagi‐Sugeno fuzzy models are developed in each part, and a switching framework is introduced to model the operating region. Accordingly, a sliding mode controller (SMC) is developed. The proposed modeling and controller are implemented on the benchmark quadruple tank process (QTP). It is demonstrated that the proposed modeling and controller design provides simplicity and universality in a set of nonlinear systems; it is robust with respect to various internal and external disturbances and model uncertainties which allows for accurate regulation and tracking; and it converges in finite time, is capable of controlling nonlinear systems with coupling dynamic, and enables fuzzy modeling of continuous‐time systems without imposing differentiability.

Design and analysis of a novel compact spanner‐shaped ultra‐wideband antenna for MIMO systems

SummaryIn this communication, a novel compact spanner shaped ultra‐wideband (UWB) antenna is designed for multiple input multiple output (MIMO) system applications. The proposed structure of size 24 × 32 mm2 (0.24λ0 × 0.32λ0, λ0 is calculated at lower band frequency) is designed and fabricated on widely available FR4 dielectric material with a dielectric constant of 4.4 and loss tangent of 0.02. The proposed structure comprises two spanner shaped antennas, a defected T‐shaped stub and a pair of small vertical strips. The defected T‐shaped stub and vertical strips are used for getting a complete UWB bandwidth and good isolation between two elements. It is performing from 3.0 to 11.0 GHz with isolation more than 20 dB in most of the operating region. The parametric studies have been done for the required parameters and figured out the surface current distribution at different resonant frequencies within the working region. The MIMO antenna diversity performance is confirmed with low values of envelope correlation coefficient (ECC < 0.005), channel capacity losses (CCL < 0.04 bits/s/Hz), acceptable mean effective gain (MEG ≤ −3 dB, MEG ratio = 0 dB), and total active reflection coefficient (TARC ≤ −10 dB) values. The peak gain values are varying from 1.5 to 6.0 dBi, and the radiation efficiency values are above 83% for the entire operating region. The simulated and measured values are well matched.

Modeling and optimization of a light-duty diesel engine at high altitude with a support vector machine and a genetic algorithm

The engine performances and emissions of light-duty diesel engines in plateau regions have attracted more attention due to the upcoming China VI emission regulations for light-duty vehicles. In order to obtain a superior performance for a diesel engine running at high altitude, in this research, multi-objective optimization was conducted in an entire operating region for a light-duty diesel engine operating at an altitude of 1960 m. A support vector machine (SVM) was employed to set up a surrogate model between the calibration parameters and the engine performance parameters. The multi-objective optimization of the fuel consumption and the emissions was carried out using a genetic algorithm with the premise of keeping the same power performance of the original engine within durability constraints and with a minimum smoke limit. The results showed that the SVM regression model had excellent predictive performance and generalization abilities, and that the model could accurately predict the various performance parameters of the diesel engine. The diesel engine running in the plateau region could achieve a good comprehensive performance with the proposed multi-objective optimization method. In comparison with the base engine in the plateau region, a simultaneous reduction of 52.92% for the brake specific NOx emission and 0.67% for the brake specific fuel consumption was achieved, with an acceptable increase of smoke emission.

A Retrofit Hierarchical Architecture for Real-Time Optimization and Control Integration

To achieve the optimal operation of chemical processes in the presence of disturbances and uncertainty, a retrofit hierarchical architecture (HA) integrating real-time optimization (RTO) and control was proposed. The proposed architecture features two main components. The first is a fast extremum-seeking control (ESC) approach using transient measurements that is employed in the upper RTO layer. The fast ESC approach can effectively suppress the impact of plant-model mismatch and steady-state wait time. The second is a global self-optimizing control (SOC) scheme that is introduced to integrate the RTO and control layers. The proposed SOC scheme minimizes the global average loss based on the approximation of necessary conditions of optimality (NCO) over the entire operating region. A least-squares regression technique was adopted to select the controlled variables (CVs) as linear combinations of measurements. The proposed method does not require the second order derivative information, therefore, it is numerically more reliable and robust. An exothermic reaction process is presented to illustrate the effectiveness of the proposed method.

IMPROVING THE REACTIVE POWER CAPABILITY OF GRID CONNECTED DOUBLY FED INDUCTION GENERATOR

Due to increasing wind power generation in the electric power system, the reactive power generation by the wind farms is a major concern during both steady state and faulty conditions. This work, first, presents the reactive power capability (RPC) curve of doubly-fed induction generator (DFIG) considering three limitations (rotor voltage, rotor current and stator current) for reactive power production/consumption, for the complete operating range which is obtained by optimal rotor speed employing maximum power point tracking (MPPT) algorithm. It is established that the total reactive power generation is limited by rotor voltage at low speeds and by rotor current at higher speed. However, the total reactive power consumption is limited by stator current, for entire operating region. Selection of partial rated converter rating is crucial in terms of cost, efficiency, operating speed range and reactive power capability. The effect of converters rating on the enhancement of RPC of doubly fed induction generation is analyzed. Complete capability curves of DFIG for different stator voltages are developed considering grid-side converter (GSC) contribution towards reactive power capability.

A Torque Angle-Based Fault Detection and Identification Technique for IPMSM

Condition monitoring of the stator and rotor problems such as interturn short fault (ITSF) and partial irreversible demagnetization fault (PIDF) in an interior permanent magnet synchronous motor (IPMSM) is essential for achieving high efficiency and reliability. This article presents a torque angle-based inverter-embedded technique for the online detection and identification of ITSF and PIDF. This technique monitors the deviation in the torque angle caused due to ITSF and PIDF at a certain operating point. In steady-state operation, the torque angle decreases from its original value (healthy state) due to ITSF while increases in the case of PIDF. This particular trend of torque angle is used for the detection and identification of ITSF and PIDF. In this article, the torque angle for a healthy IPMSM is first obtained using multivariate regression analysis over the entire operating region and then compared with the torque angle during operation for any potential variation. The proposed method is verified using a finite-element method-based simulation and experiment on a 400-W IPMSM. The results suggest that the proposed method can be a viable candidate for efficient ITSF and PIDF detection and identification in real time.