Reducing input/output current ripple for driving converter by multiple technology

To improve the vehicle dynamic performance and ultra-capacitor operating circumstance,this paper studied the multi-current-two-quadrant converter applied to drive high power DC motor in ultra-capacitor electric bus(UCEB).Compared with normal current-two-quadrant converter,the multi-current-two-quadrant converter can reduce the motor armature current ripple and the ultra-capacitor current ripple.Moreover,it improves power capabilities,reliability and fault tolerant capability of driving system.After analyzing the structure and working principle of the multi-current-two-quadrant converter,the expressions of armature current ripple and the quantitative relationships between the ultra-capacitor power loss and duty cycle were derived.The simulation and experimental results showed that the multi-current-two-quadrant converter has great advantages in reducing the armature current ripple and ultra-capacitor power loss,which can improve the vehicle performance and overall efficiency.

Efficient Power Conditioner for a Fuel Cell Stack-Ripple Current Reduction Using Multiphase Converter

Integration of fuel cell stack with an inverter is complex in nature. A number of factors have to be taken into account in designing the inverter as well as during the integration. One of these factors is ripple current which could affect the life of the fuel cell stack if there is fuel and/or oxidant starvation. In this paper an inverter topology is investigated which significantly reduces or even nullifies the ripple content in the fuel cell system. The investigations have been carried out using indigenously developed 1 KW PEMFC stack and a 4 kW PEMFC stack with single and multi phase inverter. The results are presented here.

Design of Digital Linear Power Supply with Low Current Ripple

A linear power supply is a circuit architecture directly driven by AC. Multiple high-voltage LEDs (light-emitting diodes) are connected in series to withstand the input voltage. The LEDs are divided into multiple segments through a segment switching mechanism to adapt to the pulsating DC changes after bridge rectification. Due to imperfect switching between control signals, there may be signal overlap or misalignment, which reduces circuit performance and component lifespan. Firstly, signal overlap occurs when the next segment opens before the previous segment is about to close. This state causes overlapping intervals where two segments of current combine, resulting in a high combined current that can lead to significant power losses and generate heat, potentially reducing the lifespan of the components. Secondly, signal misalignment occurs when the next segment prepares to open after the previous segment has completely closed. In this state, there is a time gap with no current flow, resulting in reduced output power and exacerbating LED flickering. Both of these undesirable phenomena introduce ripple into the LED output current. In this paper, a digitalized design is proposed to precisely compensate for the timing between alternating signals, significantly reducing output current ripple. This approach helps enhance power supply performance, extend component lifespan, and reduce LED index flicker.

Constant Ripple Current Control for Switching DC-DC Converter

The adapted DC-DC converters should be smaller in size and have a small output current ripple to meet the increasing demand for low voltages with high performance and high density micro processors for several microelectronic load applications. This paper proposes a DC-DC converter using variable on-time and variable switching frequency control enhanced constant ripple current control and reduced magnetic components. The proposed converter is realized by making the turn-offtime proportional to the on-time of the converter, according to the input and output voltage, thereby reducing the corresponding current ripple on output voltage in the continuous conduction mode. A Buck DC-DC converter using the proposed control strategy is analyzed in detail, along with some experimental results to show the performance and effectiveness of this converter.

Research on Torque Ripple Under Healthy and Open-Circuit Fault-Tolerant Conditions in a PM Multiphase Machine

In this paper,research into torque ripple production has been undertaken for both the healthy and open-circuit faulttolerant conditions of a five-phase permanent magnet(PM)machine by using the instantaneous power(I-Power)approach.When only the fundamental component of the phase currents is applied to the phase windings,it has been shown that the 9th and 11th harmonics of the back-electromotive force(back-EMF)causes torque ripples in a five-phase PM machine and its frequency is ten times the frequency of the fundamental phase currents.When the combined fundamental and third harmonic components of the phase currents are applied to the phase windings,it has been shown that the 7th and 13th harmonic of the back-electromotive force(back-EMF)causes additional torque ripples in a five-phase PM machine.These torque ripples under fault-tolerant conditions have been analyzed analytically,as well.It has been proven that there are interactions between the fundamental component of current and the third harmonic component of the back-EMF and vice versa.These interactions cause torque ripples.A finite element analysis(FEA)model of the five-phase PM machine has been done to validate the analytical results.

Comparative Study of Conventional, Fuzzy Logic and Neural PID Speed Controllers with Torque Ripple Minimization for an Axial Magnetic Flux Switched Reluctance Motor

Three speed controllers for an axial magnetic flux switched reluctance motor with only one stator, are described and experimentally tested. As it is known, when current pulses are imposed in their windings, high ripple torque is obtained. In order to reduce this ripple, a control strategy with modified current shapes is proposed. A workbench consisting of a machine prototype and the control system based on a microcontroller was built. These controllers were: a conventional PID, a fuzzy logic PID and a neural PID type. From experimental results, the effective reduction of the torque ripple was confirmed and the performance of the controllers was compared.

Novel torque ripple minimization algorithm for direct torque control of induction motor drive

To elucidate the principles of notable torque and flux ripple during the steady state of the conventional direct torque control （DTC） of induction machines, the factors of influence torque variation are examined. A new torque ripple minimization algorithm is proposed. The novel method eradicated the torque ripple by imposing the required stator voltage vector in each control cycle. The M and T axial components of the stator voltage are accomplished by measuring the stator flux error and the expected incremental value of the torque at every sampling time. The maximum angle rotation allowed is obtained. Experimental results showed that the proposed method combined with the space vector pulse width modulation （SVPWM） could be implemented in most existing digital drive controllers, offering high performance in both steady and transient states of the induction drives at full speed range. The result of the present work implies that torque fluctuation could be eliminated by imposing proper stator voltage, and the proposed scheme could not only maintain constant switching frequency for the inverter, but also solve the heating problem and current harmonics in traditional induction motor drives.

Simulation analyzing of torque-ripple minimization for switched reluctance motor

Discusses the inevitability of torque ripple of switched reluctance motor (SRM) for its double saliency construction and switch power supply, and the minimization of torque ripple, under traditional current chopping control mode, and presents a varying current amplitude chopping control method with a linear control model of varying current amplitude chopping shown, and the simulation of torque profiles under two kinds of current chopping control modes to demonstrate the validity of decreasing torque ripple.

Dual Mode-Multiple Output SEPIC Converter Integrated with Passive Ripple Cancelling Circuit for Standalone PV Energy Harvesting System

This document addresses an exhaustive standalone Photovoltaic (PV) energy harvesting system considering two crucial issues: system efficiency and cost effectiveness. It contributes a compact resolution with a combined feature of Dual Mode-Multiple Output (DMMO) associated with input ripple reduction technique. Control strategy incorporates with aspect of Maximum Power Point Tracking (MPPT) and output voltage levels regulation. A theoretical analysis is conducted to evaluate the effect of ripple current on PV power. Proposed dual mode converter achieves efficiency of 98.36% and 97.76% respectively for mode-1 and mode-2 operation. However, simulation is performed applying MATLAB/SIMULINK tools to analyze the feasibility of the recommended system.

Reliability of DC-link capacitor in pulsed power supply for accelerator magnet

Capacitors are widely used in pulsed magnet power supplies to reduce ripple voltage,store energy,and decrease power variation.In this study,DC-link capacitors in pulsed power supplies were investigated.By deriving an analytical method for the capacitor current on the H-bridge topology side,the root-mean-square value of the capacitor current was calculated,which helps in selecting the DC-link capacitors.The proposed method solves this problem quickly and with high accuracy.The current reconstruction of the DC-link capacitor is proposed to avoid structural damage in the capacitor’s current measurement,and the capacitor’s hotspot temperature and temperature rise are calculated using the FFT transform.The test results showed that the error between the calculated and measured temperature increases was within 1.5℃.Finally,the lifetime of DC-link capacitors was predicted based on Monte Carlo analysis.The proposed method can evaluate the reliability of DC-link capacitors in a non-isolated switching pulsed power supply for accelerators and is also applicable to film capacitors.

大功率储能变流器功率模组DC-link电容器的试验研究

从满足最恶劣运行工况下纹波电流和满足动态响应的电容容值这两方面,对三相大功率储能变流器功率模组中的DC-link电容进行了计算设计。在简化模型下,定性分析了功率模组间连接铜排寄生电感对电容纹波电流的放大效应,并采取实验验证的方式在整机装置上进行了测试验证。测试发现,模组采用铜排连接方式的原有设计不合理,电容纹波电流放大明显,不能满足设计要求。针对该问题进行了改良设计,模组间更换采用叠排方式连接,改进后模组内DC-link电容的纹波电流放大现象得到了明显抑制,满足整机设计要求。

光伏逆变器中DC-link电容的选型计算

DC-link电容是光伏逆变器直流侧电路的重要组成部分,其设计选型对逆变器的性能、体积、重量及成本均有一定影响。以单级三相全桥拓扑的光伏逆变器为例,重点讨论了薄膜电容的额定电压、容量及纹波电流等参数所需满足的要求,进行了理论分析、计算和仿真,以期对实际应用中的电容选取提供参考。

Research on Open-circuit Fault Tolerant Control of Six-phase Permanent Magnet Synchronous Machine Based on Fifth Harmonic Current Injection

This paper proposes a novel control approach for fault-tolerant control of dual three-phase permanent magnet synchronous motor(PMSM) under one-phase open-circuit fault.A modified six-phase static coordinate transformation matrix and an extended rotating coordinate transformation matrix are investigated considering the influence of the fifth harmonic space on fault-tolerant control. These mathematical models are further analyzed in the fundamental space and the fifth harmonic space after the fault and to eliminate the coupling between the d-q axis voltage equation in the fundamental wave space and the d-q axis voltage equation in the fifth harmonic space, a secondary rotation coordinate transformation matrix is proposed. To achieve the purpose of reducing torque ripple, the fault-tolerant control method proposed in this paper not only takes the minimum copper loss as the constraint condition, but also injects the fifth harmonic current. The experimental result of current and torque is used to verify the accuracy of fault-tolerant control.

DC-link纹波电流分析与研究

对DC-link电容寿命及使用稳定性起关键作用的是电容本身的温升,而温升与系统施加在电容两端纹波电流的大小有直接关系。通过理论计算、仿真验证、实测验证等方法,总结归纳DC-link纹波电流的计算方法,为工程人员合理选择DC-link电容、设计散热方式及计算散热能力提供依据。

Finite Control Set Model Predictive Current Control of a Five-Phase PMSM with Virtual Voltage Vectors and Adaptive Control Set

This paper presents an improved finite control set model predictive current control(FCS-MPCC)of a five-phase permanent magnet synchronous motor(PMSM).First,to avoid including all the 32 voltage vectors provided by a two-level five-phase inverter into the control set,virtual voltage vectors are adopted.As the third current harmonics can be much reduced by virtual voltage vectors automatically,the harmonic items in the cost function of conventional FCS-MPCC are not considered.Furthermore,an adaptive control set is proposed based on voltage prediction.Best control set with proper voltage vector amplitude corresponding to different rotor speed can be achieved by this method.Consequently,current ripples can be largely reduced and the system performs much better.At last,simulations are established to verify the steady and transient performance of the proposed FCS-MPCC,and experiments based on a 2 kW five-phase motor are carried out.The results have validated the performance improvement of the proposed control strategy.

车用DC-Link电容器的选择和主要电参数估算

本文通过分析车用DC-Link电容器的使用条件和对比不同电容器的特点,解释了车用DC-Link应用场合最终选择薄膜电容器的原因。并通过理论分析介绍了薄膜电容器的主要电参数的选择和估算。

Frequency Support from PMSG-Based Wind Turbines with Reduced DC-Link Voltage Fluctuations

Frequency droop control is widely used in permanent magnet synchronous generators(PMSGs)based wind turbines(WTs)for grid frequency support.However,under frequency deviations,significant DC-link voltage fluctuations may occur during the transient process due to sudden changes in real power of such WTs.To address this issue,a current feedforward control strategy is proposed for PMSG-based WTs to reduce DC-link voltage fluctuations when the WTs are providing frequency support under grid frequency deviations.Meanwhile,the desired frequency support capability of the PMSG-based WTs can be ensured.Simulation results verify the rationality of the analysis and the effectiveness of the proposed control method.

ON THE RESONANT GENERATION OF WEAKLY NONLINEAR STOKES WAVES IN REGIONS WITH FAST VARYING TOPOGRAPHY AND FREE SURFACE CURRENT

The effect of nonlinearity on the free surface wave resonated by an incident flow over rippled beds, which consist of fast varying topography superimposed on an otherwise slowly varying mean depth, is studied using a WKBJ-type perturbation approach. Synchronous, superharmonic and in particular subharmonic resonance were selectively excited over the fast varying topography with corresponding wavelengths. For a steady current the dynamical system is autonomous and the possible nonlinear steady states and their stability were investigated. When the current has a small oscillatory component the dynamical system becomes non-autonomous, chaos is now possible.

Analysis of Harmonic Current in Permanent Magnet Synchronous Motor and Its Effect on Motor Torque

The inverter is used as the power supply of modern permanent magnet synchronous motor (PMSM). The inverter may produce harmonics in inversion process and form harmonic currents in motor stator winding which can lead to factors against motor smooth operation such as torque fluctuating and winding heating. This article focuses on the harmonic currents formed in the motor stator winding by getting the harmonics frequency spectrum with software. The effect of harmonic currents to motor torque is analyzed with the finite element method (FEM).