Current Regulation Strategy Research Articles

Performance optimization study on the thermal management system of proton exchange membrane fuel cell based on metal hydride hydrogen storage

To compare the performance differences between proton exchange membrane fuel cell (PEMFC), metal hydride tank (MHT) and heat exchanger (HX) coupling configurations and optimize thermal management methods, this study investigates and compares three coupling systems, PEMFC-MHT-HX series, PEMFC-HX-MHT series, and PEMFC-MHT|HX parallel system. Results reveal that, under controlled load variables, all three systems achieve an energy efficiency of 48.1 % at the maximum net power of 41.99 kW, increased by 16.93 % compared to standalone PEMFC. Exergy efficiencies of the systems show little differences, with values of 43.65 %, 43.38 %, and 43.51 %, respectively. The PEMFC-MHT-HX system exhibits the highest hydrogen outlet pressure, which is suitable for high-pressure applications. Conversely, the PEMFC-MHT|HX system enables flexible hydrogen supply regulation through decoupled control of hydrogen outlet pressure and flow. Increasing the MHT heat transfer coefficient can enhance the outlet pressure, but this effect diminishes beyond 1500 W/(m2·K). Sensitivity analysis identifies current and stack temperature as pivotal factors, emphasizing the necessity of precise current regulation and effective thermal management strategies. Additionally, the proportion of PEMFC waste heat recovered by the MHT decreases from 36.8 % to 29.0 % as the current load rises from 100 A to 400 A, indicating potential for alternative waste heat recovery devices over HX.

Potential of Power Electronics to Improve the Power Quality of Network Grid

This study deals with voltage drop characterization of transmission systems by using power electronics circuits supplied from embedded generation. Many grid-connected power electronic systems, such as STATCOMS, UPFCs, and distributed generation system interfaces, use Voltage Source Inverters (VSI) connected to the supply network through a filter. This filter, typically a series inductance acts to reduce the switch harmonics entering the distribution network an alternative filter is an LCL network, which can achieve reduced levels of harmonic distortion at lower switching frequencies and with less inductance, and therefore has potential benefits for higher power application. However, systems incorporating LCL filters require more complex control strategies. This dissertation proposes a robust strategy for regulating the grid current connected via an LCL filter. The strategy integrates an outer loop grid current regulator with inner capacitor current regulation to stabilize the system. An asynchronous farm PI current regulation strategy is used for the outer grid current control loop. Linear analysis, simulation, and experimental results are used to verify the stability of the control algorithm across a range of operating conditions and finally, expressions for "harmonic impedance" of the system are derived to study the effects of supply voltage distortion on the harmonic performance of the system.

Multiple Synchronous Reference Frame Current Harmonic Regulation of Dual Three Phase PMSM With Enhanced Dynamic Performance and System Stability

This article proposes an improved multiple synchronous reference frame (MSRF) current harmonic regulation strategy for dual three phase permanent magnet synchronous machine drive system. A new vector space decomposition transformation combined with auxiliary currents is designed to decouple the current fundamental with current harmonics, and the auxiliary currents can be established by the π/9 phase shifting of the physical currents in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ABC</i> set and the π/18 phase shifting of the physical currents in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">XYZ</i> set. By employing the proposed current decomposition, it is easy to detect them using low pass filters in MSRFs. A generic complex vector proportional integral regulator is then employed to control the detected current harmonics to track the current harmonic references. Compared with the existing MSRF-based methods, the proposed method provides a new current harmonic detection with reduced delay effect, which contributes to enhancing the dynamic performance of current harmonic regulation, and also stabilizing the control system. Comprehensive experimental results are given to validate the effectiveness of the proposed control strategy.

Advanced Control of Switched Reluctance Motors (SRMs): A Review on Current Regulation, Torque Control and Vibration Suppression

With the increasing environmental concerns, a paradigm shift towards electric and hybrid electric vehicles is expected. Switched Reluctance Motors (SRMs) have emerged as a viable competitor to other established electrical machines. SRMs are known for their simple construction, robustness, inherent fault tolerant structure and low production and maintenance costs. Moreover, the machine has gained interest due to the absence of permanent magnets or windings in the rotor structure, which significantly reduces production costs when compared to other electric motors. The SRM, however, present some known drawbacks, such as increased torque ripple and acoustic noise production, as well as a highly nonlinear behavior. Through the use of adequate control strategies, however, the main challenges of the machine can be overcome. Thus, this paper presents a state-of-the-art review of the advanced control of SRMs, encompassing current regulation strategies, torque control strategies and vibration suppression techniques. First, two categories of current controllers are reviewed: model-independent and model-based. Next, indirect and direct torque control methods are explored. Then, three approaches to vibration suppression are discussed, namely active cancellation, current profiling and direct instantaneous force control. Lastly, a summary of each topic is presented and suggestions of future research topics are listed.

Emergency C-section, maternal satisfaction and emotion regulation strategies: effects on PTSD and postpartum depression symptoms

ABSTRACT Objective This cross-sectional study aimed to investigate the relationship between a mother’s current emotion regulation strategy (antecedent-focused vs. response-focused), her satisfaction with childbirth, and posttraumatic and/or depressive symptoms after unplanned C-section. Background The mother’s and baby’s health is considered a priority during childbirth. As a result, situations in which an unplanned C-section is required may not allow mothers to express their needs and emotions. This may lead to feelings of dissatisfaction regarding the childbirth experience. Methods Fifty French participants aged 18–35 (M = 27.10; S.D. = 3.99) who had a C-section were recruited on social networking groups and completed four self-report measures online, up to two years after childbirth. These measures assessed emotion regulation strategies currently used, birth satisfaction, postpartum depression symptoms and PTSD symptoms. Results Main results indicate (1) Mothers who use expressive suppression, a response-focused strategy, are less satisfied with childbirth. (2) Emotion regulation, when combined with maternal satisfaction, shows a negative association with posttraumatic stress score and depression score. Conclusion This study provides interesting data for further research. Follow-up studies about emotion regulation, postpartum depression and posttraumatic stress symptoms should be conducted in the future in order to provide clinical recommendations.

Bidirectional Power Flow Control of a Multi Input Converter for Energy Storage System

The objective of this paper is to propose a multi-input DC-DC converter with bidirectional power flow control capability. Compared to the traditional power converter, the multi-input converter (MIC) can save on the number of components and the circuit cost. Under normal conditions, the MIC is able to transfer energy from different input sources to the load. However, if the battery module is adopted, both the charging or discharging features should be considered. Therefore, the bidirectional power flow control of the MIC is necessary. On the other hand, because of the inconsistency characteristics of batteries, unbalanced circuit operation might occur whereby the circuit and the battery might be damaged. Therefore, dynamic current regulation strategies are developed for the MIC. Consequently, the proposed MIC circuit is able to achieve the bidirectional power flow control capability as well as control the input currents independently. Detailed circuit analysis and comprehensive mathematical derivation and of the proposed MIC will be presented in this paper. Finally, both simulation and experimental results obtained from a 500 W prototype circuit verify the performance and feasibility of the proposed bidirectional multi-input converter.

Emotions as context: Do the naturalistic effects of emotion regulation strategies depend on the regulated emotion?

Researchers have examined how several contexts impact the effectiveness of emotion regulation strategies. However, few have considered the emotion-to-be-regulated as a context of interest. Specific emotions are important contexts because they may require particular responses to internal and external stimuli for optimal regulation. Ninety-two undergraduates completed 10 days of ecological momentary assessment, reporting their current mood, recent emotions, and emotion regulation strategies three times per day. The frequency with which certain emotion regulation strategies were used (i.e., acceptance, positive refocusing, reappraisal, problem-solving, and other-blame) differed by the specific emotion experienced. Acceptance and positive refocusing were associated with better mood regardless of emotion, while substance use was associated with worse mood regardless of emotion. Reappraisal was associated with better mood in response to anger than anxiety or sadness, while emotional suppression and other-blame were associated with worse mood in response to anger. These results suggest some emotion regulation strategies exhibit emotion-invariant effects while others depend on the emotion-to-be-regulated.

Spin-State Regulation of Perovskite Cobaltite to Realize Enhanced Oxygen Evolution Activity

Summary Perovskite electrocatalysts strongly rely on electronic structure regulation, especially for electron configuration (e g ) and conductivity. However, current regulation strategies inevitably involve ambiguous entanglement of crystals, electrons, and spin degrees of freedom. Here, we developed a spin-state regulation method to optimize oxygen evolution reaction (OER) activity by lattice orientation control of LaCoO 3 epitaxial films. The different lattice-oriented LaCoO 3 films bring different degrees of distortion of the CoO 6 octahedron, successfully inducing a spin-state transition of cobalt from a low spin state (LS t 2g 6 e g 0 ) to an intermediate spin state (IS t 2g 5 e g 1 ). X-ray absorption spectroscopy of Co L-edge and O K-edge provides experimental support of spin-state transition in different lattice-oriented LaCoO 3 films. As expected, LaCoO 3 (100) film possesses optimal e g electron filling, lower adsorption free energy, and higher conductivity, exhibiting better OER performance than the other two films. Our findings demonstrate that electronic state regulation will be a new avenue for the rational design of high-activity perovskite electrocatalysts.

Dynamic Optimal AC Line Current Regulation Method for Three-Phase Active Power Conditioners

The main feature of the three-phase back-to-back active power conditioner (APC) is to improve the power quality of the microgrid. During the large power variation transient, the severe voltage surge/sag on the dc-link of the APC may cause its malfunction. Therefore, the dynamic optimal ac line current regulation (DOCR) with flexible dc-link voltage slope (FDVS) is proposed in this paper. The proposed DOCR can determine the accurate input current reference value to regulate the dc-link voltage under the large power variation condition. On the other hand, the proposed FDVS can further mitigate the dc-link voltage variation during the large power variation transient. The mathematical equations of the proposed control strategy are derived thoroughly. Furthermore, procedures to determine the dc-link capacitance with the proposed DOCR are developed. Finally, the experimental results obtained from a 5-kVA back-to-back APC verify the feasibility and the performance of the proposed line current regulation strategies.

Torque-Ripple-Based Interior Permanent-Magnet Synchronous Machine Rotor Demagnetization Fault Detection and Current Regulation

To develop a reliable permanent-magnet synchronous machine (PMSM) controller for electric vehicle application, detection of permanent-magnet (PM) demagnetization conditions is of significance. This paper explores the use of torque ripple for online PM demagnetization fault diagnosis using continuous wavelet transforms (CWT) and grey system theory (GST). First, a torque-ripple-based rotor flux linkage detection model considering electromagnetic noises is proposed, which employs CWT filtering, wavelet ridge spectrum, and torque ripple energy extraction. This model is able to reveal the torque variation and eliminate the effect of electromagnetic interferences. Second, GST is employed to facilitate the detection of demagnetization ratios and torque ripple energy pulsations caused by demagnetization. Third, a current regulation strategy is proposed to minimize the torque ripples induced by PM demagnetization, which contributes to making the approach feasible to interior PMSM (IPMSM). Furthermore, the proposed real-time irreversible demagnetization detection approach can identify the demagnetization fault under different operating conditions. The proposed approach and current regulation strategy are experimentally verified on a down-scaled laboratory IPMSM.

Application of SMES in the Microgrid Based on Fuzzy Control

The concerns about the reliability of SMES have always been the obstacle to the practical application of SMES. In this paper, a fuzzy logic-based operating current regulation strategy, aiming at improving the reliability of SMES, has been proposed. In this control strategy, the current of SMES will be maintained in the best range during normal operation. When the temperature of magnet sharply rises after deep power exchange, the current of SMES will be down regulated to reduce ac loss and obtain more thermal stability margin. An application of SMES in microgrid is taken as an example to verify the control strategy. Simulation results based on MATLAB/Simulink demonstrate the feasibility and correctness of the control strategy.

Distinct Roles of Emotion Reactivity and Regulation in Depressive and Manic Symptoms Among Euthymic Patients

Investigating differences in the ways that people react to mood-evoking stimuli and regulate subsequent emotions may help to elucidate important mechanisms underlying depressed or hypomanic mood states. Euthymic young adults with bipolar disorder (n = 23) or depression (n = 21) were recruited for a study of emotion and mood. Two mood inductions assessed for differences in mood reactivity. Participants completed measures of current symptoms and emotion regulation strategies. Maladaptive (B = 0.42, p = .021) and adaptive (B = −0.26, p = .011) emotion regulation strategies were significantly associated with depressive symptoms. Bipolar diagnosis (B = 5.51, p = .035), and threat mood reactivity (B = −0.26, p = .015) were associated with hypomanic symptoms. Interaction terms for mood reactivity and emotion regulation were not significant in either model, although net regression indicated significant differences in two trends. Depressed moods, associated with MDD or BD, may be initiated and maintained primarily due to poor choice of emotion regulation strategies. Elevated mood states are more specific to bipolar disorder, and may be triggered by mood reactivity, rather than regulation.

DC-Link Voltage Control Strategy for Three-Phase Back-to-Back Active Power Conditioners

The objective of this paper is to propose a three-phase back-to-back active power conditioner (APC) with dc-link voltage control strategies for microgrid applications. The demanded active and reactive powers of the APC via bidirectional power flow control can help to regulate the frequency and voltage of microgrids to achieve high stability. Moreover, the dc-link capacitor is the necessary component of the back-to-back APC for power decoupling and power flow balancing. In order to provide the ability to improve the power quality and stability of microgrids as well as to reduce the dc-link capacitance, two dc-link voltage control methods are developed: 1) optimal ac-line current regulation strategy and 2) dynamic dc-link voltage regulation (DDVR) strategy. Under steady state, the proposed optimal ac-line current regulation strategy is able to minimize the change of the input current variation as well as to achieve the dc-link regulation in one 60-Hz cycle. As soon as an abrupt or continuous power change occurs, the dc-link voltage of the APC will be changed dramatically, and the voltage protection could easily be triggered. Therefore, a novel DDVR strategy is proposed in order to prevent the false alarm as well as to reduce the required dc-link capacitance. Thorough mathematical equations corresponding to the proposed dc-link voltage control strategy are presented which can be used to determine the appropriate dc-link capacitance. Computer simulations and hardware experiments obtained from a 5-kVA prototype circuit demonstrate the feasibility and performance of the proposed APC.

Closed-Loop Current Control of Multilevel Converters Formed by Parallel Complementary Unidirectional Phase Legs

This paper presents a dual-loop current regulation strategy for coupled-inductor multilevel converters. The basis of the strategy is to recognize that the current in the coupled inductor can be decoupled into independent dc bias and ac load currents, which can be then regulated using separate feedback processes. This allows the system to enforce continuous conduction operation of the inverter phase legs by dynamically varying the dc bias current to track the ac load current. Design principles are presented to account for the different common- and differential-mode load dynamics and to maximize the closed-loop bandwidths of both feedback loops. This ensures that the dc bias current can follow rapid load transient events. Matching simulation and experimental results obtained for a five-level flying-capacitor coupled-inductor inverter are presented to validate the proposed control strategy.

Combine Evolutionary Optimization with Model Predictive Control in Real-time Flood Control of a River System

In order to establish successful flood control strategies to prevent or alleviate severe flood damages, real-time optimization-based control can be a supplementary strategy, besides setting operating rules (regulations) for the hydraulic structures. This research combines evolutionary optimization, by means of a Genetic Algorithm (GA), with the Model Predictive Control (MPC) technique to develop and test a real-time flood control method for the 12 gated weirs in the Belgian case study of the river Demer. The evolution of this method is also the main contribution of this study. The combination of GA with MPC allows coping with the highly nonlinear system behaviour and local minimum problems. The system searches for better control actions by minimizing a cost function while at the same time avoiding violation of the defined constraints. The optimization results testify that the system is able to assist the current regulation strategies that are based on fixed regulation rules (three-position controller).

A Novel Three-Level Hysteresis Current Regulation Strategy for Three-Phase Three-Level Inverters

This paper presents a new hysteresis current regulation strategy for the neutral point clamped and flying capacitor (FC) three-level inverters. The strategy uses the measured average of the switched phase leg output voltage to adjust the controller hysteresis band as the load back EMF varies to maintain a near constant phase leg switching frequency. The phase leg switchings are then fine tuned to a fixed frequency clock to further improve frequency regulation. Next, the zero-crossings of the measured phase leg average voltages are used to select between positive and negative switched output voltage levels, so that only one hysteresis current regulator is required for the full inverter switched output voltage range. For the FC inverter, a state machine is then added to select between redundant switching states to maintain balanced capacitor voltages. Finally, the controller is extended to a three-phase system by subtracting the common mode interacting current from the total phase leg current error before making any switching decision. The resulting controller achieves a line-to-line harmonic performance that is very close to open-loop phase disposition pulse width modulation, while retaining all of the dynamic benefits of hysteresis current regulation.

Automatic Standby Power Management Using Usage Profiling and Prediction

Reducing the standby power used by home appliances is critical in a household energy management system. Although significant effort has been made to minimize the standby power use of appliances, manual operation is still required to eliminate standby power usage. Additionally, the current regulation strategy of standby power typically focuses on real-power consumption, and it does not consider the apparent power and power factors. We propose an automatic standby power reduction system that is based on user-context profiling. Our system profiles and analyzes the occupancy pattern, as well as the appliance usage. The system then actively manages standby power utilization by predicting the probabilities of future appliance usage. We built a prototype smart meter to monitor and control the power lines. We also developed software that implements the proposed scheme. Our experiments, conducted for three to five weeks in four households, show that power consumption in standby mode can be reduced.

Libration dynamics and stability of electrodynamic tethers in satellite deorbit

This paper studies libration dynamics and stability of deorbiting nano-satellites by short and bare electrodynamic tethers. A critical aspect of satellite deorbit by an electrodynamic tether is to maintain the tether aligned with the local vertical and stable while subjected to external perturbations. The dynamics of electrodynamic tether system in deorbit application is divided into the orbital motion of the center of system’s mass and the tether libration motion relative to that center. Major space environmental perturbations including the current-induced electrodynamic force, atmospheric drag, oblateness effect of the Earth, irregularity of geomagnetic field, variable plasma density, solar radiation pressure, and lunisolar gravitational attractions are considered in the dynamic analysis. Quantitative analyses are provided in order to characterize the order of the perturbative torques during the deorbit process. A single index is derived from the libration energy to stabilize the libration motion by regulating the current in the tether through simple on-off switching. Numerical results show that the libration dynamics of an electrodynamic tether has significant impacts on the deorbit process and the electrodynamic tether cannot effectively deorbit satellites without libration stability control. The proposed current regulation strategy is simple and very effective in stabilizing libration motion of an electrodynamic tether.

Adaptive Control of a Solid Oxide Fuel Cell Ultra-Capacitor Hybrid System

Solid oxide fuel cells (SOFCs) offer a number of advantages beyond those of most other fuel cells. However, like other fuel cells, rapid load following is difficult, and can lead to fuel starvation and consequently fuel cell damage. Mitigating fuel starvation and improving load following capabilities are conflicting control objectives. However, the issue can be addressed by the hybridization of the system with an energy storage device. In this paper, a steady-state property of the SOFC, combined with a current regulation strategy, is used to manage transient fuel utilization and thereby address fuel starvation. Meanwhile, an overall system strategy is employed to manage energy sharing in the hybrid system for load following as well as for maintaining the state-of-charge of the energy storage device. This work presents an adaptive control algorithm that uses online parameter estimation to update the controller. The control design is validated on a hardware-in-the-loop setup and experimental results are provided.

High-Performance Current Regulation for Low-Pulse-Ratio Inverters

AC current regulation for low-pulse-ratio inverters is particularly challenging because the controller bandwidth is often comparable to the target fundamental frequency and this constrains the transient response. This paper presents an improved current regulation strategy to address this issue, using state feedback concepts to deterministically compensate for pulsewidth modulation (PWM) transport delay so that the controller gains can be significantly increased. Controller design principles are presented using discrete linear-quadratic-regulator theory, and an elegant strategy is applied to make the system more robust to PWM saturation. Experimental results for both 50-Hz and 400-Hz systems confirm the theoretical concepts and demonstrate the superior transient performance of the proposed strategy.