A new high-performance AC/DC power factor correction switching converter based on one-cycle control technology and active floating-charge technology

A new family of converters,high-performance AC/DC power factor correction(PFC) switching converters with one-cycle control technology and active floating-charge technology,was derived and experimentally verified.The topology of a single-phase CCM and DCM Boost-PFC switching converter was also analyzed.Its operating prniciples and control methods were expounded.Based on these,a new type of AC/DC switching converter circuits for PFC combined with one-cycle control technology was presented herein.The proposed AC/DC switching converter significantly helps improve the converter efficiency and its power factor value.

Stability analysis of linear/nonlinear switching active disturbance rejection control based MIMO continuous systems

In this paper,a linear/nonlinear switching active disturbance rejection control(SADRC)based decoupling control approach is proposed to deal with some difficult control problems in a class of multi-input multi-output(MIMO)systems such as multi-variables,disturbances,and coupling,etc.Firstly,the structure and parameter tuning method of SADRC is introduced into this paper.Followed on this,virtual control variables are adopted into the MIMO systems,making the systems decoupled.Then the SADRC controller is designed for every subsystem.After this,a stability analyzed method via the Lyapunov function is proposed for the whole system.Finally,some simulations are presented to demonstrate the anti-disturbance and robustness of SADRC,and results show SADRC has a potential applications in engineering practice.

Model predictive control of three-level active front-end converter with low switching frequency

In medium voltage-high power(MV-HP)applications,the high switching frequency of power converter will result in unnecessary energy losses,which directly affect efficiency.To resolve this issue,a novel finite control set-model predictive control(FCS-MPC)with low switching frequency for three-level neutral point clamped-active front-end converters(NPC-AFEs)is proposed.With this approach,the prediction model of three-level NPC-AFEs is established inα-βreference frame,and the control objective of low average switching frequency is introduced into a cost function.The proposed method not only achieves the desired control performance under low switching frequency,but also performs the efficient operation for the three-level NPC-AFEs.The simulation results are provided to verify the effectiveness of proposed control scheme.

Optically Activated Charge Domain Model for High-Gain GaAs Photoconductive Switches

A model for theoretical analysis of nonlinear (or high gain) mode of photoconductive semiconductor switches (PCSS's) is proposed.The switching transition of high gain PCSS's can be described with an optically activated charge domain. The switching characteristics including rise time,delay and their relationship to electric field strength,optical trigger energies are discussed.The formation and radiation transit,accumulation of the charge domain are related with the triggering and sustaining phases of PCSS's,respectively.The results of the mathematical model on this mechanism agree with experimental results.

Vibration Control of a Composite Beam Using Self-sensing Semi-active Approach

Structural vibration control was an active research area for the past twenty years because of their potential applications in aerospace structures,civil structures,naval structures,etc.Semi-active vibration control methods based on piezoelectric actuators and synchronized switch damping on inductance（SSDI） techniques attract the attention of many researchers recently due to their advantages over passive and active methods.In the SSDI method,a switch shunt circuit is connected to the piezoelectric patch to shift the phase and amplify the magnitude of the voltage on the piezoelectric patch.The most important issue in SSDI method is to control the switching actions synchronously with the maximum vibration displacement or maximum strain.Hence,usually a displacement sensor is used to measure the vibration displacement or a collocated piezoelectric sensor is needed to measure the strain of the structure near the piezoelectric actuator.A self-sensing SSDI approach is proposed and applied to the vibration control of a composite beam,which avoids using a separate sensor.In the self-sensing technique,the same piezoelectric element functions as both a sensor and an actuator so that the total number of required piezoelectric elements can be reduced.One problem in the self-sensing actuator,which is the same as that in the traditional collocated piezoelectric sensors,is the noise generated in the sensor signal by the impact of voltage inversion,which may cause extra switching actions and deteriorate control performance.In order to prevent the shunt circuit from over-frequent on-and-off actions,a simple switch control algorithm is proposed.The results of control experiments show that the self-sensing SSDI approach combined with the improved switch control algorithm can effectively suppress over-frequent switching actions and gives good control performance by reducing the vibration amplitude by 45%,about 50% improvement from the traditional SSDI with a separate piezoelectric element and a classical switch.

Open-circuit fault diagnosis and fault tolerance for shunt active power filter

The open-circuit fault of the power switches in shunt active power filter(SAPF) would exacerbate the harmonic pollution of power grid, and degrade the reliability of the devices and system. A fault diagnosis method is proposed based on reference model and an over-modulation strategy under hardware fault tolerance for SAPF. First, a mathematic model is established for SAPF. Second, the residuals are generated by comparing the outputs of reference model and those of actual model, and open-switch fault is detected and diagnosed by residual evaluation. After that, hardware fault tolerance is performed with the three-phase four-switch(TPFS) topology to isolate the faulty phase. Finally, the over-modulation strategy is proposed to increase the voltage transfer ratio of the TPFS topology. Simulation and experimental results verified the feasibility and effectiveness of the proposed method.

An Improved Active Miller Clamp Crosstalk Suppression Method for Enhancement-Mode GaN HEMTs in Phase-Leg Configuration

When using traditional drive circuits,the enhancement-mode GaN(eGaN)HEMT will be affected by high switching speed characteristics and parasitic parameters leading to worse crosstalk problems.Currently,the existing crosstalk suppression drive circuits often have the disadvantages of increased switching loss,control complexity,and overall electromagnetic interference(EMI).Therefore,this paper combines the driving loop impedance control and the active Miller clamp method to propose an improved active Miller clamp drive circuit.First,the crosstalk mechanism is analyzed,and the crosstalk voltage model is established.Through the crosstalk voltage evaluation platform,the influencing factors are evaluated experimentally.Then,the operating principle of the improved active Miller clamp drive circuit is discussed,and the optimized parameter design method is given.Finally,the effect of the improved active Miller clamp method for suppressing crosstalk is experimentally verified.The crosstalk voltage was suppressed from 3.5 V and-3.5 V to 1 V and-1.3 V,respectively,by the improved circuit.

The Modified Multiple Model Switching Tuning Control Application in AVC

In the complex mechanical vibration environment, the dominant frequency of the system varies remarkably and swiftly under various running conditions, which also characterizes uncertainty and time-variation. It is very impending and important to suppress or isolate the detrimental vibrations related to the above memtoned system with active vibration control (AVC) technology. This paper presented the improved linear quadratic gaussian (LQG) control scheme with a specified filter to realize broadband disturbance/noise attenuation and assure intensive suppression of vibration at the key vibration frequency, then applies and modifies the multiple model switching tuning (MMST) control method by disturbance observation to track the variation of dominant vibration component timely. The effectiveness and superiority of the presented control method were demonstrated by numerical simulation and AVC experiment on a flexible cantilever beam under sweeping excitation.

Analysis of Light Load Efficiency Characteristics of a Dual Active Bridge Converter Using Wide Band-Gap Devices

In this paper, the zero voltage switching (ZVS) region of a dual active bridge (DAB) converter with wide band-gap (WBG) power semiconductor device is analyzed. The ZVS region of a DAB converter varies depending on output power and voltage ratio. The DAB converters operate with hard switching at light loads, it is difficult to achieve high efficiency. Fortunately, WBG power semiconductor devices have excellent hard switching characteristics and can increase efficiency compared to silicon (Si) devices. In particular, WBG devices can achieve ZVS at low load currents due to their low parasitic output capacitance (Co,tr) characteristics. Therefore, in this paper, the ZVS operating resion is analyzed based on the characteristics of Si, silicon carbide (SiC) and gallium nitride (GaN). Power semiconductor devices. WBG devices with low Co,tr operate at ZVS at lower load currents compared to Si devices. To verify this, experiments are conducted and the results are analyzed using a 3 kW DAB converter. For Si devices, ZVS is achieved above 1.4 kW. For WBG devices, ZVS is achieved at 700 W. Due to the ZVS conditions depending on the switching device, the DAB converter using Si devices achieves a power conversion efficiency of 91% at 1.1 kW output. On the other hand, in the case of WBG devices, power conversion efficiency of more than 98% is achieved under 11 kW conditions. In conclusion, it is confirmed that the WBG device operates in ZVS at a lower load compared to the Si device, which is advantageous in increasing light load efficiency.

Performance Analysis for Dispensing Mechanism of Active Code

The dispensing mechanism of active code is a key technology in an active network. Conventional capsule and programmable switch approaches have their own shortcomings. The DCCAN(distributed code caching for active network) mechanism presented in this paper overcomes these shortcomings. In this paper, capsule and programmable switch approaches are introduced, and their shortcomings are analyzed. The principle of the DCCAN mechanism is described. The theory analysis in transmit width based on the DCCAN mechanism and capsule approach are described. The theory analysis shows that the DCCAN mechanism has many good characteristics and can improve the efficiency of an active network. Key factors which affect the transmit width based on the DCCAN mechanism are discussed. The using condition of the DCCAN mechanism is also discussed.

主被动调Q-锁模Nd∶YAG激光器的实验研究

对脉冲氙灯泵浦的调Q-锁模Nd：YAG固体激光器进行了实验研究.比较和分析了声光主动锁模、Cr^4＋ ：YAG晶体被动调Q-锁模以及这两种机制联合锁模情况下Nd：YAG激光器的输出特性.在Cr^4＋ ：YAG晶体被动调Q-锁模时得到了深度80%以上的锁模输出,但是锁模不完全,且波形和能量稳定性低,脉宽为1.9～3.6 ns.而主被动联合锁模克服了这一缺点,可获得幅值和能量抖动小于±5%、锁模深度100%、脉宽小于650ps、能量近300mJ的超短脉冲输出.

MULTI-AGENT TRACKING OF A HIGH-DIMENSIONAL ACTIVE LEADER WITH SWITCHING TOPOLOGY

This paper considers a multi-agent tracking problem for a high-dimensional active leaderand variable interconnection topology. The state of the leader not only keeps changing but also maynot be measured. To estimate the state such a leader individually, a neighbor-based local controllertogether with a neighbor-based state-estimation rule is given for each autonomous agent. Then, theauthors prove that, with the help of a constructed common Lyapunov function (CLF), each agent cantrack the active leader with unmeasurable states. Finally, the authors explicitly construct a CLF foran active leader with unknown periodic input for illustration.

Preventing Hardware Trojans in Switch Chip Based on Payload Decoupling

Hardware Trojans in integrated circuit chips have the characteristics of being covert,destructive,and difficult to protect,which have seriously endangered the security of the chips themselves and the information systems to which they belong.Existing solutions generally rely on passive detection techniques.In this paper,a hardware Trojans active defense mechanism is designed for network switching chips based on the principle of encryption algorithm.By encoding the data entering the chip,the argot hidden in the data cannot trigger the hardware Trojans that may exist in the chip,so that the chip can work normally even if it is implanted with a hardware Trojans.The proposed method is proved to be effective in preventing hardware Trojans with different trigger characteristics by simulation tests and practical tests on our secure switching chip.

A Design of the Elliptic Switched Current Filter

In conformity with a fifth order RLC elliptic filter circuit prototype, it is easy to conceive the corresponding RC active filter circuit. Simple and feasible method presented here can be used to contrive the equivalent switched capacitor filter circuit and switched current filter circuit. Consulting the technique data manual, we can expediently design a specific RLC filter. Therefore, it is of great convenience to design the switched current filter, which has the same performances. Such a kind of technology is useful in the domain of analogue sampled data signal processing.

Hypomanic/manic switch after transcranial magnetic stimulation in mood disorders:A systematic review and meta-analysis

BACKGROUND Nowadays there is an increasing use of transcranial magnetic stimulation(TMS)both in neurological and psychiatric fields.After Food and Drug Administration approval of TMS for the therapy of treatment-resistant depression,TMS has been widely used in the context of mood disorders(MD).However,growing reports regarding the possibility of developing hypomanic/manic switch(HMS)have generated concern regarding its use in MDs.AIM To investigate the actual risk of developing HMS due to TMS in the treatment of MD.METHODS We led our research on PubMed,Scopus and Web of Science on March 22,2020,in accordance to the PRISMA guidelines for systematic review.Only double blind/single blind studies,written in English and focused on the TMS treatment of MD,were included.A meta-analysis of repetitive TMS protocol studies including HMS was conducted using RevMan 5.4 software.The assessment of Risk of Bias was done using Cochrane risk of bias tool.This protocol was registered on PROSPERO with the CRD42020175811 code.RESULTS Twenty-five studies were included in our meta-analysis:Twenty-one double blind randomized controlled trials(RCT)and four single blind-RCT(no.of subjects involved in active stimulation=576;no.of subjects involved in sham protocol=487).The most frequently treated pathology was major depressive episode/major depressive disorder,followed by resistant depression,bipolar depression and other MD.The majority of the studies used a repetitive TMS protocol,and the left dorsolateral prefrontal cortex was the main target area.Side effects were reported in eight studies and HMS(described as greater energy,insomnia,irritability,anxiety,suicidal attempt)in four studies.When comparing active TMS vs sham treatment,the risk of developing HMS was not significantly different between conditions.CONCLUSION Applying the most usual protocols and the appropriate precautionary measures,TMS seems not to be related to HMS development.

A NEW MULTIFUNCTION SWITCHED-CURRENT FILTER

A new switched-current(SI)biquadratic filter is presented which can simultaneouslyprovide the low-pass,high-pass and band-pass filters in a single building block.A symbol torepresent the universal SI integrator is also introduced.It can simplify the analysis and synthesisof SI networks.

SWITCHED-CURRENT FILTER DESIGN USING CASCADED SECTIONS

A new analogue sampled-data active device, named as a switched-current operationalamplifier (SIOA), is presented. The use of active circuit elements may simplify drawing the circuitdiagram significantly greatly and may permit easier analysis and synthesis of SI networks. Anumber of all pole and elliptic (second-or third-order) switched-current (SI) filters are derivedfrom the switched capacitor prototypes. These can be used as simple self-contained filters or asfilter sections in the cascaded realizations of a higher order transfer functions. To illustrate theapproach, a fifth-order low-pass filter is designed.

Experimental Research on Inhibition of Surface Flashover Based on High Power Gallium Arsenide Photoconductive Switches Triggered by Laser

Semi-insulating gallium arsenide （GaAs） photoconductive semiconductor switches （PCSS） have great potential for high voltage switching application, however, the utility is restricted by surface flashover which wouId result in breakdown. In this paper, a model of photo-activated charge wave was proposed based on the theory of photo-activated charge domain （PACD） in GaAs PCSS, and moderate suppression of PACD formation by loading the semiconductor surface with dielectric material was investigated theoretically and experimentally. Current as high as 3.7 kA was obtained at 28 kV, implying that this method can effectively inhibit the surface flashover and improve the service life of DC charged GaAs PCSS.