Current-controlled Switching Research Articles

Analysis and control of the equilibrium position in bare electrodynamic tether systems

This study focuses on the calculation of the equilibrium position of the bare electrodynamic tether (BEDT) and the implementation of stable control during the de-orbiting process. A novel method for calculating the equilibrium position of the BEDT system is proposed, utilizing integral variable substitution. This approach provides an analytical expression for the equilibrium position, thereby addressing the limitations of numerical curve-fitting methods and facilitating further dynamic analysis and controller design. To address the influence of variations in geomagnetic field strength and electron density on the tether attitude during deorbiting, a sliding mode controller based on prescribed performance is designed to stabilize the BEDT around its equilibrium position by adjusting the tether length. This adjustment simultaneously regulates angular momentum and current on the tether. In contrast to conventional current switching methods, the proposed strategy effectively mitigates undesired transient responses and additional system disturbances, and accurately stabilizing the BEDT system around the equilibrium position. Numerical simulations show that the analytical equilibrium calculations closely match the nonlinear model, with an error margin of less than 5%. Additionally, the tether length adjustment strategy successfully stabilizes the system around the equilibrium position, achieving an angular deviation of less than 0.2 degrees and enhanced deorbit efficiency compared to the current switching control method.

Experimental Validation of Torque Ripple Reduction in MMC-Fed BLDC Motor Using the Proposed Phase Modulated Model Predictive Control

This paper presents the torque ripple analysis of a brushless DC (BLDC) motor. This torque ripple is generated by generating the ripple in the stator current. For reducing the ripple, a phase-modulated model predictive current control strategy has been implemented in an MMC-fed BLDC motor. The performance of the torque ripple of the BLDC motor is enhanced by using the proposed phase-modulated model predictive control (PMMPC) technique as compared to the model predictive control (MPC) and proportional-integral (PI) controller. Moreover, the performance of the torque ripple is enhanced by increasing the switching frequency for all controllers. A comparative analysis of the torque ripple of the BLDC motor is depicted for different current control and different switching frequency. A harmonic distribution is also shown for all control techniques at switching frequencies of 1, 5, and 10 kHz. The harmonic content is minimum for the PMMPC technique when compared to the other mentioned control technique. The experimental validation of simulation results has also been done here.

Efficiency Analysis and Design Considerations of a Hysteretic Current Controlled Parallel Hybrid Envelope Tracking Power Supply

This paper presents the realization of an Envelope Tracking Power Supply (ETPS), for a sinusoidal envelope input signal. A parallel hybrid topology is chosen for the implementation. In this topology, a voltage-controlled Class-AB linear amplifier stage and a current-controlled switching converter stage operate in parallel. A hysteretic current control scheme is employed to control the operation of the switching converter. Block-level implementation of the ETPS is done using Simulink 2017b, continuous mode simulation. Simulations are performed using a sinewave input envelope signal = 1.94+ 1.2 sin(ω∙t). The input frequency varied from 1MHz to 60MHz. As the input frequency is increased, the ETPS moves from the linear to the non-linear region of operation. During the transition, the slew rates of the load current and the switching current match at a particular input frequency of 2MHz while the efficiency peaks. The maximum obtained efficiency while tracking the sinewave input signal is 82.3%. The way the efficiency can be optimized by focusing on the matching of the slew rates of load and switching currents is explained. Also, an insight into the study of various circuit parameters and the trade-offs that the designer needs to consider while designing an ETPS, is provided.

Application of PCCS Method to PV Generation System with Half Bridge Inverter

A Power Conditioning System (PCS) for a PV power generation system obtains the maximum power from a photovoltaic (PV) array by Maximum Power Point Tracking (MPPT), but losses in the inverter are a factor in lowering the power obtained by the MPPT. The generation of harmonic currents is also a problem for PCS. This paper proposes the application of the Peak Current Control Switching (PCCS) method in PCS for PV Generation System using a half bridge inverter. The half bridge inverter improves efficiency by reducing the number of switching elements and further suppresses harmonic currents by controlling them using the PCCS method. In this paper, a comparative simulation of the conventional Hysteresis Current Control (HCC) method and the proposed PCCS method is performed using a half bridge inverter. The results of harmonic analysis and comparative simulation of total harmonic distortion (THD) show that the PCCS method generates harmonic components near the switching frequency, and that the proposed PCCS method always has a lower distortion rate than the conventional HCC method.

An Improved Charge-Based Method Extended to Estimating Appropriate Dead Time for Zero-Voltage-Switching Analysis in Dual-Active-Bridge Converter

This paper presents a comprehensive analysis of zero-voltage-switching (ZVS) realization with an improved charge-based method by considering both voltage dependency parasitic capacitance and dead time in dual-active-bridge (DAB) converters, when the voltage ratio between the primary and secondary sides does not match the turn ratio of the transformer. For this purpose, a unified equivalent circuit is proposed to represent the switching motions at all possible switching instances under the condition of one-leg manipulation. The combinations of switching cases can be presented in a table to build the corresponding equivalent circuit for ZVS analysis. Combined with the improved charge-based method, the common solutions of the minimum required switching current and the appropriate dead-time range for each equivalent circuit to realize ZVS are deduced. The allowable range of the dead time for ZVS as a function of the switching current is analyzed to determine the appropriate dead time. Once the switching current and dead-time range are derived, the model-based lowest switching current control method can be used to achieve ZVS by using the appropriate amount of both factors. Experiments using a 4 kW DAB prototype were conducted to verify the theoretical analyses.

Compliance current controlled volatile and nonvolatile memory in Ag/CoFe2O4/Pt resistive switching device

We report on the resistive memory effects of a Ag/CoFe2O4/Pt device and a deterministic conversion between volatile and nonvolatile resistive switching (RS) memory through the tuning of current compliance (I CC). For the smaller I CC (10−4 A) the device exhibits volatile RS behavior with an atomically sized conducting filament showing the quantum conductance. For an intermediate I CC (10−2 A) nonvolatile bipolar RS behavior is observed, which could originate from the formation and rupture of filament consisting of Ag ions. The high resistance state (HRS) of the device shows a semiconducting conduction mechanism, whereas the low resistance state (LRS) was found to be Ohmic in nature. The temperature dependent resistance studies and magnetization studies indicated that the electrochemical metallization plays a dominant role in the resistive switching process for volatile and nonvolatile modes through the formation of Ag conducting filaments. For higher I CC (10−1 A) the device permanently switches to LRS. The irreversible RS memory behaviors, observed for higher I CC, could be attributed to the formation of a thick and stable conducting channel formed of oxygen vacancies and Ag ions. The compliance current controlled resistive switching modes with a large memory window make the present device a potential candidate to pave the way for future resistive switching devices.

Field-free spin\u2013orbit torque perpendicular magnetization switching in ultrathin nanostructures

Magnetic-field-free current-controlled switching of perpendicular magnetization via spin–orbit torque (SOT) is necessary for developing a fast, long data retention, and high-density SOT magnetoresistive random access memory (MRAM). Here, we use both micromagnetic simulations and atomistic spin dynamics (ASD) simulations to demonstrate an approach to field-free SOT perpendicular magnetization switching without requiring any changes in the architecture of a standard SOT-MRAM cell. We show that this field-free switching is enabled by a synergistic effect of lateral geometrical confinement, interfacial Dyzaloshinskii–Moriya interaction (DMI), and current-induced SOT. Both micromagnetic and atomistic understanding of the nucleation and growth kinetics of the reversed domain are established. Notably, atomically resolved spin dynamics at the early stage of nucleation is revealed using ASD simulations. A machine learning model is trained based on ~1000 groups of benchmarked micromagnetic simulation data. This machine learning model can be used to rapidly and accurately identify the nanomagnet size, interfacial DMI strength, and the magnitude of current density required for the field-free switching.

On the Coexistence of Multiple Limit Cycles in H-Bridge Wireless Power Transfer Systems With Zero Current Switching Control

This paper deals with the analysis of limit cycle oscillations in H-bridge wireless power transfer resonant inverters under primary-side Zero Current Switching (ZCS) control. The limit cycles are computed by solving their initial value problem. If this problem is not dealt with properly, erroneous results may be derived and ghost or physically inadmissible limit cycles may be obtained. A complementary condition must be added to obtain only real limit cycles that can take place in the system. The stability analysis of these real cycles is performed using Floquet theory. For the case of the series-series compensated topology, the resulting monodromy matrix reveals that these cycles are stable whenever they exist and the load resistance is larger than a critical value. On the contrary, for load resistance smaller than this critical value, coexistence of different real stable limit cycles is also possible. While one of the limit cycles always exists for the whole range of load resistance values, two of them are created/destroyed through a cyclic fold bifurcation. The boundary of this bifurcation is determined. Numerical simulations corroborate the theoretical predictions and some experimental measurements are presented to validate some of the theoretical and simulation results.

Vector Control Algorithm Based on Different Current Control Switching Techniques for Ac Motor Drives

A comparative analysis of vector control scheme based on different current control switching pulses (HC, SPWM, DPWM and SVPWM) for the speed response of motor drive is analysed in this paper. The control system using different switching techniques, are comparatively simulated and analysed. Ac motor drives are progressively used in high-performance application industries due to small size, efficient performance, robust to torque response and high power to size ratio. A mathematical model of ac motor drives is presented in order to explain the numerical theory of motor drives. The vector control technique is utilized for efficient speed control of ac motor drive based on independent torque and air gap flux control. The study compares the total harmonic distortion contents of phase currents of ac motor drive and speed response in each case. The simulation result shows that total harmonic distortion across the phase current in SVPWM is less as compared to other switching techniques while the rise time in speed response across SVPWM technique is faster as compared to other switching methods. The simulation result of ac motor drives speed control is demonstrated in Matlab/Simulink 2018b.

The dynamic processes in second generation HTS tapes under the pulsed current and magnetic impact

This paper presents the results of complex multiphysical modelling of non-equilibrium states arising in high-temperature superconducting composites under current, magnetic, and combined control switching impacts types. The simulation and analysis of the dynamics of electrophysical and thermal processes occurring in the HTS composites layered structure taking into account the influence of local thermal processes in the composite structure, in particular, heat generation bursts during a pulse, has been performed. The HTS composite switching times from the superconducting to the normal state have been investigated for various current pulses amplitudes in homogeneous magnetic fields. An experimental verification of the numerical model has been carried out.

An Improved Sliding-Mode Current Control of Induction Machine in Presence of Voltage Constraints

This article proposes a novel approach to design sliding-mode control (SMC) for an induction motor (IM) in the presence of operational constraints. Different from the traditional techniques in SMC, the proposed method assumes the existence of a constant input disturbance and incorporates it in the switching current control law. Effectively, this leads to integral action through disturbance estimation together with an antiwindup mechanism naturally occurring when the control signal reaches its operational limits. The finite-time convergence of the SMC law is established through a Lyapunov analysis. Experimental evaluations are performed on an industrial-sized IM, where the current dynamics of the motor are controlled using SMC, and a velocity proportional–integral (PI) controller is used for the outer-loop control system. Experimental results reveal that the proposed sliding-mode current control systems provide much improved closed-loop control performance over the traditional SMC system. Further comparative experimental studies with well-designed PI current controllers provide insight into the characteristics of the proposed current control systems.

Predictive-Fixed Switching Current Control Strategy Applied to Six-Phase Induction Machine

In applications such as multiphase motor drives, classical predictive control strategies are characterized by a variable switching frequency which adds high harmonic content and ripple in the stator currents. This paper proposes a model predictive current control adding a modulation stage based on a switching pattern with the aim of generating a fixed switching frequency. Hence, the proposed controller takes into account the prediction of the two adjacent active vectors and null vector in the ( α - β ) frame defined by space vector modulation in order to reduce the (x-y) currents according to a defined cost function at each sampling period. Both simulation and experimental tests for a six-phase induction motor drive are provided and compared to the classical predictive control to validate the feasibility of the proposed control strategy.

Suppression of Undesired Attractors in a Self-Oscillating H-Bridge Parallel Resonant Converters Under Zero Current Switching Control

Resonant converters under zero current switching control strategy can exhibit coexistence of attractors, making it difficult the startup of the system from zero initial conditions. In this brief, the problem of multiple coexisting attractors in parallel resonant converters is addressed. Appropriate modifications of the switching decision with the aim of converting undesired attractors into virtual ones are proposed. A suitable control signal is generated from the state variables of the system and used to adjust the switching decision. Numerical simulations corroborate the proposed solutions and the simplest one was finally verified by measurements from a laboratory prototype.

Nonlinear Dynamic Modeling and Analysis of Self-Oscillating H-Bridge Parallel Resonant Converter Under Zero Current Switching Control: Unveiling Coexistence of Attractors

This paper deals with the global dynamical analysis of an H-bridge parallel resonant converter under a zero current switching control. Due to the discontinuity of the vector field in this system, sliding dynamics may take place. Here, the sliding set is found to be an escaping region. Different tools are combined for studying the stability of oscillations of the system. The desired crossing limit cycles are computed by solving their initial value problem and their stability analysis is performed using Floquet theory. The resulting monodromy matrix reveals that these cycles are created according to a smooth cyclic-fold bifurcation. Under parameter variation, an unstable symmetric crossing limit cycle undergoes a crossing-sliding bifurcation leading to the creation of a symmetric unstable sliding limit cycle. Finally, this limit cycle undergoes a double homoclinic connection giving rise to two different unstable asymmetric sliding limit cycles. The analysis is performed using a piecewise-smooth dynamical model of a Filippov type. Sliding limit cycles divide the state plane in three basins of attraction, and hence, different steady-state solutions may coexist which may lead the system to start-up problems. Numerical simulations corroborate the theoretical predictions, which have been experimentally validated.

A Model Predictive Power Control Approach for a Three-Phase Single-Stage Grid-Tied PV Module-Integrated Converter

This paper presents the concept of three-phase module-integrated converters (MICs) incorporated in grid-tied large-scale photovoltaic (PV) systems. The current-source converter with dc voltage boost capability, namely the single-stage power conversion system, is proposed for the three-phase PV MIC system. A model predictive scheme with low switching frequency is designed to control the proposed topology in such a way that provides a certain amount of active and reactive power in steady-state operation and also provides a proper ratio of reactive power under transient conditions to meet the low-voltage ride through regulations. To predict the future behavior of current control values and switching states, a discrete-time model of the MIC is developed in the synchronous reference frame. It is demonstrated that the injected active and reactive power can be controlled by minimizing the cost function introduced in the predictive switching algorithm. The proposed structure is simulated in MATLAB/SIMULINK software. An experimental verification is provided to justify the performance of the proposed control method through a 300-VA laboratory prototype. The results verify the desired performance of the proposed control scheme for exchanging both active and reactive powers between the PV MIC and the grid within different operating conditions.

Current Controlled Switching in Si/PS/a-Si Heterostructure

Current controlled switching has been observed in p-type crystalline Silicon (p-c-Si)/porous Si (PS)/n-type hydrogenated amorphous Silicon (n-a-Si:H) heterostructure. Mechanism of the switching is proposed consideringpresence of trapped carriers at the silicon nanocrystal-SiOx interface. A part of the trapped charges are considered to be bound near the n-a-Si:H/PS and PS/p-c-Si interface forming an additional coulomb barrier for the majority carriers. It is assumed that during the flow of current through the PS layer, the captured carriers get de-trapped by impact-excitation leading to breaking of the barrier after certain threshold value resulting in the switching. This model matches well with the experimental results.

Transformerless SoC-based current control switching battery charger for e-vehicle: design and analysis

Electric-based vehicles become a necessity in the future to dramatically reduce the effects of pollution. There are various devices involve in the operation of electric vehicles, one of which is a battery charger. This paper discusses the design steps, circuit and ripple performance analysis associated with building a battery charger system. The analysis shows the differences between RL and RC circuits in controlling the output voltage average and the ripples. It shows how RLC mixed circuit improve performance in both controlling the output voltage average and the ripple suppression.

A CPS Based Optimal Operational Control System for Fused Magnesium Furnace

Fused magnesia smelting for fused magnesium furnace (FMF) is an energy intensive process with high temperature and comprehensive complexities. Its operational index namely energy consumption per ton (ECPT) is defined as the consumed electrical energy per ton of acceptable quality and is difficult to measure online. Moreover, the dynamics of ECPT cannot be precisely modelled mathematically. The model parameters of the three-phase currents of the electrodes such as the molten pool level, its variation rate and resistance are uncertain and nonlinear functions of the changes in both the smelting process and the raw materials composition. In this paper, an integrated optimal operational control algorithm is proposed and is composed of a current set-point control, a current switching control and a self-optimized tuning mechanism. The tight conjoining of and coordination between the computational resources including the integrated optimal operational control, embedded software, industrial cloud, wireless communication and the physical resources of FMF constitutes a cyber-physical system (CPS) based embedded optimal operational control system. Successful application of this system has been made for a production line with ten fused magnesium furnaces in a factory in China, leading to a significant reduced ECPT.

Improved Direct Torque and Reactive Power Control of a Matrix-Converter-Fed Grid-Connected Doubly Fed Induction Generator

Doubly fed induction generator (DFIG) is the most popular variable-speed generator for wind energy application due to its superior performance, lower cost, and control flexibility. Instead of back-to-back converters, matrix converter (MC) can be a good alternative for connecting the DFIG rotor to the grid. This paper presents a novel lookup-table-based hysteresis controller for a variable-speed constant-frequency DFIG supplied from a direct MC. For the machine control, a modified direct torque controller (DTC) with reactive power and speed control in the outer loops has been used. The reactive component of the MC input current has been also controlled using a hysteresis controller considering all active switch states based on estimated input current and load power factor. This upgradation of the input current control switching table reduces the distortion in the grid-supplied current waveform. Overall, the performance of the DFIG with MC is experimentally shown to be superior while using the proposed controller compared with a standard DTC-based control or space-vector-pulsewidth-modulation-based vector control of MC-fed DFIG reported in the literature.

Boost Converter With Dynamic Input Impedance Matching for Energy Harvesting With Multi-Array Thermoelectric Generators

This paper presents a built-in input matching technique capable of handling a wide variation of multi-array thermoelectric generator (TEG) impedances ranging two decades, from 10 s to 1000 s of ohms. Maximum power point tracking (MPPT) control for a boost converter (BC) is introduced. The analytical expressions derived offer insight on the manner in which MPPT interacts with a BC to achieve best performance. The BC operates in a discontinuous conduction mode under pulse frequency modulation to minimize power consumption and maximize efficiency for light loads. Losses are minimized by implementing a pseudo-zero current switching control via the PMOS switch on/off time, and the output voltage is set using a global clocked comparator. A prototype was fabricated in 0.5 μm CMOS where efficiency measurements showed a maximum value of 61.15% for an R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TEG</sub> = 33.33 Ω, and quiescent power consumption was 1 μW.