This article proposes a closed-loop (CL) high-starting torque (HST) scalar control scheme (SCS) for induction motors (IM). It endows the recently proposed HST-SCS with high-output torque capability beyond starting after using an outer speed control loop feeding an inner current control loop with adaptive controllers. Presenting a cascade normalized adaptive passivity-based controller (N-APBC) for nonlinear systems encompassing the IM allows obtaining this result. It extends the normalized adaptive controller for the cascade case. As a result, it keeps the HST-SCS simple control scheme without needing variable observers or parameter estimators and employing tuning information only from the motor nameplate and datasheet. Test bench experiments with a 10 HP motor validate the proposal’s effectiveness. Comparative experimental results show that the CL HST-SCS has a required stator phase voltage lower than HST-SCS. The CL HST-SCS applies the adaptive starting voltage curve for a more extend... [more]

Modular multilevel converters (MMCs) based on half-bridge submodules (HBSMs) are unable to prevent the AC side contribution to DC side fault currents, thus necessitating circuit breakers (CBs) for protection. A solution to this problem is using submodules (SMs) that are capable of blocking the flow of current from the AC grid to feed the DC side fault. The full-bridge submodule (FBSM) is one type of fault blocking SM where the presence of two extra switches ensures that in the event of a DC fault, the reverse voltage from the FBSM capacitor is placed in the path of the AC side current feeding the DC side fault through the antiparallel diodes. However, the additional semiconductor switches in the FBSMs increase the converter cost, complexity, and losses. Several SM configurations have been proposed in recent years that provide DC fault blocking capability with lower losses and device counts than those of FBSMs. Besides, many of the proposed hybrid converter configurations that combine d... [more]

The move towards a greener energy mix to fight climate change propels investments in converter-interfaced resources such as wind and photovoltaics, energy storage systems and electric vehicles. The ongoing evolution of the power system is occurring at a very fast pace, challenging transmission and distribution system operators to seek solutions that are not only adequate for this moment but also for future scenarios. Ongoing research in the fields of power electronics, power systems and control aims at developing control strategies that will help the energy transition to occur, while keeping a stable, secure and reliable power system. The objective of this paper is to present a critical review of the control strategies developed for grid-connected power converters found in renewable energy systems, energy storage systems and electric vehicles. The impact of grid-connected converters on the stability of power grids is also reviewed, highlighting the promising control strategies for enha... [more]

This paper aims to present the gained experience in modeling and simulating bottom-up power system restoration processes. In a system with low inertia, such as a restoration path, the Common Information Models for the regulation systems appear to no longer be suitable for the estimation of the frequency behavior, and thus a detailed model must be considered. On the other hand, due to the predominantly inductive behavior of the HV transmission network, the assumption of decoupling the power-frequency behavior to study the restoration stability seems to be licit. All these issues are discussed and justified in the paper by means of the use of different software packages and of the comparison with on-field recordings.

This numerical study investigates the effects of adding a small amount of ignition promoters for controlling the wedge-induced oblique shock wave (OSW) to oblique detonation wave (ODW) transition in a premixed hydrogen−air mixture at hypersonic speeds. The time-dependent two-dimensional compressible Euler equations for multiple thermally perfect species with a reactive source term are solved using adaptive mesh refinement and detailed chemical kinetics. The wedge with a fixed angle of 26° exhibits abrupt to smooth transitions for freestream Mach numbers 7−9 (speeds 2.8−3.2 km/s) at a pressure of 20 kPa and a temperature of 300 K. The small amount (1000 PPM by vol.) of H2O2 and O3 is found to be effective at significantly reducing the initiation length for the oblique detonation transition for all Mach numbers, which suggests a practical approach to increase the operating flight range for oblique detonation wave engine with a finite length wedge. At Mach number 8, the abrupt OSW to ODW... [more]

This paper proposes the implementation, analysis and comparison of the control techniques Proportional, Integral and Derivative, Nonlinear Predictive, Fuzzy control and Sliding Mode Control technique applied to the speed control of an independent excited DC motor driven by a three-phase fully controlled rectifier of six pulses. The methodology proposes the design of the bench, modeling of the real system by the system identification method and the adjustments of the parameters of the controllers using an optimization process. Comparisons are made between the techniques, highlighting their characteristics and performances when executed under similar conditions. The robustness of each control, when acting on a nonlinear system, is investigated. All control techniques are applied in three different tests: (i) reference signal of step type without load application, (ii) reference signal with amplitude variation without load application and (iii) reference signal of step type with load appl... [more]

The consensus control method based on a multi-agent system has been widely applied in the distributed control and optimization of microgrids. However, the following drawbacks are still common in current research: (1) ignoring the influence of consensus control commands on the synchronization stability of the physical grid under primary control; (2) only focusing on improving one property ofcontrol performance, lacking comprehensive considerations of multiple properties. With the aim of solving these problems, in this paper we propose a weight-adaptive robust control strategy for implementing distributed frequency regulation of islanded microgrids. Firstly, the frequency synchronization stability of the physical layer is analyzed by means of a coupled oscillator theory and the design objectives of the controllable parameters for the information layer are formed. Subsequently, the relationship between the weight coefficients and the two important control performances of convergence speed... [more]

To better respond to the impact of power system-uncertain parameters on transient stability, a novel model named the parametric transient stability constrained optimal power flow (parametric TSCOPF) is proposed. It seeks the optimal control scheme of transient stability constrained optimal power flow (TSCOPF) expressed by the function of uncertain parameters in power systems. The key difficulty to solve this model lies in that the relationship between the parametric TSCOPF solution and uncertain parameters is implicit, which is hard to derive generally. To this end, this paper approximates the optimal solution of parametric TSCOPF by polynomial expressions of uncertain parameters based on the stochastic collocation method. First, the parametric TSCOPF model includes both uncertain parameters and transient stability constraints, in which the transient stability constraint is constructed as a set of polynomial expressions using the SCM. Then, to derive the relationship between the parame... [more]

This paper shows an increase in the robustness of a DFIG-based wind energy system when a predictive-repetitive controller in the dq reference frame is used for the control of the rotor current. This designing approach proposes a model predictive control with a receding horizon technique that uses the frequency decomposition of the reference signal as a filter. Furthermore, an augmented space-state model from the original plant model is obtained, and its implementation is addressed from the perspective of normal operating conditions of DFIG in wind energy systems. Additionally, this repetitive controller increases the robustness of the predictive control when a mismatch in machine parameters is considered. Experimental results presented in this paper endorse the advantages of this controller.

The high-dynamic permanent magnet (PM) motor servo system with high-bandwidth is the core equipment for industrial production, and the control bandwidth is also an important indexes to evaluate the performance of the servo system. The non-cascaded direct predictive speed control is an appropriate scheme to optimize the dynamic performance of the PM motor servo system. However, the high bandwidth of the non-cascaded control structure results in poor anti-interference ability, and it cannot effectively deal with the coupling relationship between current and speed, leading to poor control performance in the current limit region. Regarding the above problems, a nonlinear predictive speed control strategy combined with harmonic disturbance observer is proposed. In the proposed strategy, the disturbances of the servo system are separated from the mathematical model according to the nonlinear modeling theory, and the traditional disturbance observer is modified to estimate the harmonics. A no... [more]

This study evaluates the energy efficiency of pressure shock damping in a hydraulic lifting and leveling (HLL) module of a mobile robotic bricklaying system (RBS). The HLL module includes a servohydraulic actuator (SHA) and a hydraulic shock damper (HSD). The proposed adjustable HSD consists of a hydraulic accumulator circuit (HAC) and proportional damping valve. The frequency characteristics of the impedance and damping efficiency indices were used to evaluate the effectiveness of HSD damping. The dynamic responses of the SHA with and without HSD were analyzed based on a nonlinear state-space model. To control the damping of the pressure shock in the SHA-HSD system, a linear quadratic Gaussian (LQG) controller that follows two measurement signals was implemented. The LQG controller was adapted to the specific dynamic requirements of the SHA-HSD control system and nature of the RBS shock loads. The effectiveness of the LQG controller was evaluated during RBS operation under laboratory... [more]

The standalone microgrids with renewable energy resources (RERs) such as a photovoltaic (PV) system and fast changing loads face major challenges in terms of reliability and power management due to a lack of inherent inertial support from RERs and their intermittent nature. Thus, energy storage technologies such as battery energy storage (BES) are typically used to mitigate the power fluctuations and maintain a power balance in the system. This paper presents a model predictive control (MPC) based power management strategy (PMS) for such standalone PV/battery systems. The proposed method is equipped with an autoregressive integrated moving average (ARIMA) prediction method to forecast the load and environmental parameters. The proposed controller has the capabilities of (1) effective power management, (2) minimization of transients during disturbances, and (3) automatic switching of the operation of the PV between the maximum power point tracking (MPPT) mode and power-curtailed mode th... [more]

A symmetric single-source 7-level DC-AC converter with voltage gain of 3 and self-voltage balance is presented by combining the Class-D amplifier and the diode-clamped DC-AC converter. There is only one switch is switched for any time in this circuit. As a result, the conversion efficiency can be upgraded significantly as well as the control strategy can be simplified considerably. In the paper, the operation principle and circuit design of this converter are analyzed in detail, and its feasibility and effectiveness are verified by simulation and digital control, respectively.

The increase in the number of new energy sources connected to the grid has made it difficult for power systems to regulate frequencies. Although battery energy storage can alleviate this problem, battery cycle lives are short, so hybrid energy storage is introduced to assist grid frequency modulation. In this paper, a hybrid energy storage system composed of battery energy storage and super-capacitor energy storage systems was studied, and a comprehensive control strategy was proposed. Firstly, by setting the frequency dead zone of the energy storage to be smaller than that of the thermal power unit, the frequent action of the thermal power unit was avoided. Secondly, virtual inertial control and virtual droop control were effectively combined. Then, the state of charge of battery energy storage and super-capacitor energy storage was considered so that they could operate in harmony. Finally, a simulation model was built in MATLAB/SIMULINK, and case studies were conducted to verify the... [more]

The reduction or elimination of selected torque and current harmonics is widely used in multilevel inverter fed induction motor drives. A wide range of methods are employed to achieve this goal. Those modes of operation allow the avoidance of certain torque and current harmonics that may lead to disturbance and even mechanical and electrical resonance. In this paper, the selective harmonic elimination technique (SHE-PWM) is employed to reduce the chosen torque harmonics in a three-level NPC inverter-fed induction motor drive. The proposed method is compared with the synchronized carrier pulse width modulation technique (SCPWM). For both schemes of control simulation, a model is proposed using Simulink software. Furthermore, laboratory stand experiments are carried out to verify the correctness of torque harmonics formation.

Low-voltage dc distribution offers high efficiency for grid integration of dc-based technologies such as photovoltaic and battery storage systems and new loads such as charging stations for electric vehicles due to reduced number of conversion stages. However, the selection of protection devices, protection coordination and selectivity is still subject to research. This work proposes to use a two-layer protection technique utilizing the control capability of power converters in case of a short-circuit fault at branch level of a low voltage dc feeder. The first layer is limiting the bus current using a virtual resistance in the droop control to avoid tripping of the grid-forming converter. The second layer implements a soft fuse tripping technique for selectivity. The control concept is presented and the system stability is analyzed using impedance-based stability analysis. Experimental results on a hardware-in-the-loop setup verify the findings.

A full-bridge diode-clamped multilevel LLC resonant converter suitable for power conversion systems that use high input voltage, such as railway vehicles, is proposed in this paper. In order to eliminate the voltage deviations of the capacitors connected in series to the high voltage input DC link, a novel modulation strategy referred to as multi-neighboring reference vector discontinuous pulse-width modulation (MNRV DPWM) is proposed. Unlike the existing two-level resonant converter that varies the operating frequency to hold the output voltage constant, the proposed multilevel resonant converter modulates the amplitude of the fundamental wave input to a resonance tank while fixing the operating frequency at the resonance point. Therefore, the design of passive elements becomes easier, and stable operation is possible over a wide operating range with only one power conversion stage. In this paper, the control algorithm and operation characteristics of the newly proposed full-bridge di... [more]

Model Predictive Control (MPC) based on Discrete Space Vector Modulation (DSVM) has the advantages of simple mathematical model and fast dynamic response. It is widely used in permanent magnet synchronous motor (PMSM). Additionally, the control performance of DSVM-MPC is influenced by the accuracy of motor parameters and the select speed of optimal voltage vector. In order to identify motor parameters accurately, model predictive control for PMSM based on discrete space vector modulation with recursive least squares (RLS) parameter identification is proposed in this paper. Additionally, a method to preselect candidate voltage vectors is proposed to select the optimal voltage vector more quickly. The simulation model of RLS-DSVM-MPC is established to simulate the influence of different parameters on PMSM performance. The simulation results show that model predictive control for PMSM based on discrete space vector modulation with RLS parameter identification has a better control performa... [more]

Water purification by non-equilibrium atmospheric pressure plasma has attracted much attention and is expected to be a next-generation method. However, general approaches to improve the energy efficiency of the water purification have not been revealed. Therefore, to investigate important factors for increasing its energy efficiency, we developed coaxial cylindrical plasma reactors where pulsed streamers were generated between a high-voltage electrode and running water film. To evaluate the performance of the plasma reactors, we measured hydroxyl (OH) radicals in solution based on a chemical probe method using disodium terephthalic acid (NaTA) and decolorized indigo carmine solution. Our experimental results showed that the production rate of the OH radicals was approximately 20 nmol/s and that the energy efficiency of the decolorization was on the order of 10 g/kWh. In addition, we found that controlling liquid flow based on the Coandă effect and introducing the intermittent operation... [more]

The bulldozer is a mobile earthmoving machine with a differentially steered mobile base and an onboard manipulator used for soil cutting and transportation. Grading the ground to match a desired contour is an end-effector path-following task, with required joint rates dependent on mobile base motion. The offline planning of travel velocity profiles that respect the available hydraulic flowrate limits is difficult due to uncertainties in the machine−soil interactions. Hence, we propose a flow-bounded velocity controller enabling accurate automatic grading with online velocity scaling. The capacity of hydrostatic transmission and manipulator actuators, as well as the desired velocity, are considered when deciding the commanded velocity reference for the mobile base. Our dynamic simulation results show that, with the proposed controller, a desired ground profile is cut accurately when the machine operates at its performance limits. Comparison to constant velocity driving shows that errors... [more]

For boost power factor correction (PFC) converters operating in critical conduction mode (CRM), charge compensation strategies are utilized to improve input current distortion. However, since massive calculations are required under complex working conditions, it is difficult to achieve accurate charge compensation with limited real-time computing resources. To solve this issue, this paper proposes an adaptive charge-compensation-based variable on-time (ACVOT) control strategy. The ACVOT controller calculates the required switching on-time by adding a fundamental value and an extended on-time. The fundamental value is adjusted by the loop compensator in each half-line cycle to provide a basic bias. The extended on-time is calculated based on partial charge compensation equation in each switching cycle to reduce the distortion. Compared with conventional digital variable on-time (VOT) control, the proposed strategy improves the input current total harmonics distortion (THD) and reduces t... [more]

The objective of this article was to determine, in practice, whether the break time tw of safety fuses can impact the security level provided by electronic security systems (ESSs) that utilize the aforementioned elements as their components. This was the purpose of the conducted destructive testing aimed at estimating the break times for a certain random number of glass tube, miniature 5 × 20 (mm) fuse links with rapid operating characteristics, without a quenching medium and with a rated overcurrent intensity of 0.5 (A) by the selected manufacturers. For this purpose, a dedicated measuring attachment that enables forcing the flow of overcurrents with selected intensities in the range of 1.5 ÷ 11.5 (A) through the studied fuse links has been developed. The obtained results showed that the ratio of the break times between the best and the worst products in the entire tested range of overcurrents ranges from 5.41 (for 3.5 (A)) to 7.80 (at an overcurrent of 9.5 (A)). Statistical analysis... [more]

Cenozoic extension rates were calculated based on 20 seismic profiles across the Qiongdongnan Basin, South China Sea. The results confirmed that the Cenozoic rifting in the Qiongdongnan Basin exhibited multistage extension and spatiotemporal variation. In terms of the N−S striking seismic profiles, the structural forms of the northern and southern sags of the basin were characterized by narrow half grabens, while the structure at the center sag of the basin was characterized by wide and gentle grabens. The fault strikes in the west of the basin were mainly northeast−southwest trending, whereas those in the east of the basin changed from northeast−southwest trending to nearly east−west trending. The extension rate in the east sag was higher than that in the west area. The extension rate in the middle part was lower relative to the east and west sags. This was because the rifting was controlled by the distribution of the main boundary fault along the basin. Temporally, the Cenozoic exten... [more]

The focus of this study is on the grid-forming operation of the Energy Router (ER) based on Model Predictive Control (MPC). ER is regarded as a key component of microgrids. It is a converter that interfaces the microgrid (s) with the utility grid. The ER has a multiport structure and bidirectional energy flow control. The ER concept can be implemented in Nearly Zero-Energy Buildings (NZEB) to provide flexible energy control. A concept is proposed where the ER works as a single grid-forming converter. The challenge is to keep the predefined reference voltage and frequency inside the NZEB in all possible modes, including the idle operation mode, current sources, and nonlinear load control. To gain stability and output voltage quality, the MPC is proposed. The design of the modified MPC algorithm with improved dynamics performance is explained. PLECS software is utilized to verify the proposed algorithm. The results demonstrate the suitable performance of the proposed control method in te... [more]

This paper proposes a fault diagnosing system for the Ice-Storage Air-Conditioning System (ISACS) to supervise the operation conditions of the brine chillers. Combining the Radial Basis Function Network (RBFN) and Robust Quality Design (RQD), an Enhanced RBFN (ERBFN) is proposed to pursue fast and accurate fault diagnosis. The RQD method is used to adjust the parameters in the RBFN training stage to improve the searching ability, and good performance with a close spike tracking capability can be seen. The efficiency of the brine chiller in the ISACS was considered as the quality characteristics, the values measured by all instruments were considered as control factors, and noise factors were abnormal variable control factors in the system. ERBFN can improve the efficiency of the ISACS and prevent the equipment from being damaged without warning. ERBFN is used for fault diagnosis to ensure the ISACS performance is normal. Experimental results are provided to show the effectiveness of th... [more]