Large Current Ripple Research Articles

Simple flux‐based Lagrangian formulation to model nonlinearity of concentrated‐winding switched reluctance motors

Practical applications of switched reluctance motors (SRMs) require control techniques that can solve large torque ripple and large current ripple in power supply. To promote development of these techniques, a simple Lagrangian formulation for flux-based nonlinear SRM models is proposed. This formulation can be analysed in combination with Lagrangian circuit models of motor drivers. The properness of the formulation is supported by an example of the analysis of the operation of a simple SRM driving system.

Dead-Time Compensation Method Based on Current Ripple Estimation

This paper discusses the voltage error caused by the dead time in voltage-source PWM converters. The theoretical analysis in this paper derives the nonlinear voltage error paying attention to the parasitic output capacitance in each switching device. The analytical result reveals that the turn-off current or the switching current ripple strongly affects the voltage error. In addition, it is clarified that the conventional compensation methods based on linear and three-level approximation are suitable under small and large current ripple conditions, respectively. A simple calculation method of current ripples in three-phase PWM converters is also developed to estimate the turn-off currents. Turn-off transition compensation method which is a new compensation method based on the analysis is developed and compared with three different conventional methods in experiments using a 200-V, 5-kW three-phase grid-connection converter. The proposed method exhibits a good compensation performance having a lower voltage THD than the conventional methods in all over the operating range.

Torque Ripple Minimization in Direct Torque Control of Brushless DC Motor

This paper mainly proposes a direct torque control strategy to minimize torque ripple in brushless DC (BLDC) motor. BLDC motor has large current and torque ripple when one voltage vector applied in one cycle due to its low inductance. Hence, this paper proposed a hysteresis torque control with PWM mode to control the resultant torque. Moreover, when the direct torque control system is operating during the two-phase half-bridge <TEX>$120^{\circ}$</TEX> conduction mode, large torque ripple in commutation area appears every 120 electrical degree. Based on analyzing the root of torque ripple in detail, lookup tables of switching devices states for new half-bridge modulation mode in the positive and negative reference torque put forwarded. Finally, simulations by MATLAB software and experiment results from DSP are presented to verify the feasibility and effectiveness of the proposed strategy operating in four-quadrant operation.

Dynamic Sliding Mode Evolution PWM Controller for a Novel High-Gain Interleaved DC-DC Converter in PV System

Considering the disadvantages of the traditional high-gain DC-DC converter such as big size, high voltage stress of switches, and large input current ripple, a novel high-gain interleaved boost converter with coupled-inductor and switched-capacitor was proposed correspondingly and the operation principle together with the steady-state analysis of this converter was also described. Besides, a new control approach-dynamic sliding mode evolution PWM controller (DSME PWM) for the novel topological converter based on both dynamic evolution and sliding mode control was also presented. From the simulation results and experimental validation the proposed converter can fulfill high-gain boost, low ripple of both the input current and the output voltage. Furthermore, MPPT technique can be also achieved in a short time by simulation. The efficiency and stability of the converter proposed in this paper can be improved.

Impact of Current Ripple on Li-ion Battery Ageing

The aim of this paper is to investigate the impact of the current ripple, originating from the dc-dc converter of e.g. a PHEV powertrain, on the ageing of Li-ion batteries. Most research concerning batteries focuses on very low (μHz) to low (Hz) frequencies and low current ripples to create very accurate battery models which can determine e.g. the State of Charge of the battery. On the other hand the design of dc-dc converters tries to reduce the current ripple by using multiple phases with interleaving technique and capacitors in parallel with the battery. The interaction between the current ripple of the dc-dc converter and the battery has received little attention so far. A test set-up is build with two identical 304 V , 12 kWh Li-ion batteries and two 100 A dc-dc converters. The dc-dc converter can be connected to an LCL-filter or solely to the primary inductor of this filter, such that the battery current contains a small or large current ripple respectively. The batteries are discharged and charged to simulate the circumstances in which a plug-in hybrid electric vehicle is used. After each month, during which the battery either experiences a small or large current ripple, characterization tests are performed to establisch the ageing of the batteries. Based on the test results, the current ripple does not appear to have a measurable impact on the battery resistance and the Discharge and Regen Power. There is an increase of the resistance and a decrease of the Discharge and Regen Power, but this is to be expected as the battery packs are submitted to 3 months of Combined Cycle Life Testing. The temperature of the battery turns out to be far more important for the resistance and attained power levels of the batteries. The absent effect of the current ripple on the ageing of the batteries may be due to the intrinsic double-layer capacitor. This capacitor at the surface of the electrodes carries part of the current ripple and reduces the current ripple as experienced by the actual charge transfer reaction which carries the dc-part of the current.

Active current ripple cancellation in parallel connected buck converter modules

Parallel connection of converters has become a popular method of improving efficiency. This study first presents a design technique for a buck converter with two parallelly connected power modules (PMs), where one PM is designed with large current ripple for high efficiency. This study then demonstrates an active current ripple cancellation technique, where the current waveform of the second PM is shaped to be the exact opposite to that in the first PM, to reduce the current ripple as seen by the output capacitor. The factors that affect the overall efficiency in a parallel connected converter and the calculation of the parameters that determine the effectiveness of the ripple cancellation are reported. A prototype parallel converter is designed based on the proposed converter design technique and the current ripple seen by the output capacitor is successfully reduced by 66% with the proposed ripple cancellation technique, under different line and load conditions.

3상 PWM 정류기의 경부하시 입력전류 THD 저감을 위한 d축 전류리플 저감 PWM 방법

In this paper, a new PWM method is proposed to reduce the input current harmonics of 3 phase PWM rectifier. In the conventional carrier comparison PWM method, a triangular wave is generally used as the carrier wave. However, the large d-axis current ripple by the triangle carrier wave may be a source of large input current THD(Total Harmonic Distortion). In this paper, a new carrier comparison PWM method with saw tooth wave is proposed. Depending on the sector where the voltage command vector places, one of the rising or falling saw tooth wave is selected. To reduce the switching losses of the saw tooth carrier PWM, the discontinuous PWM is also presented. The proposed PWM method can reduce the d-axis current ripple as well as the switching losses. The performance of the conventional and proposed PWM methods is verified by the simulation and experimental results.

High Step-up Boost Converter Integrated With a Transformer-Assisted Auxiliary Circuit Employing Quasi-Resonant Operation

Stacking an auxiliary step-up circuit on top of a boost converter is one of the most attractive structures for nonisolated high step-up applications. In this paper, in order to avoid the large input current ripple of coupled-inductor-based circuits, an auxiliary step-up circuit is integrated via an additional transformer and its balancing capacitor. A voltage-doubler is adopted as an auxiliary step-up circuit, which is inherently suitable for high-voltage applications due to its simple structure and low-voltage stress. Moreover, the transformer leakage inductor and the balancing capacitor constitute a resonant tank so that the quasi-resonant operation makes the current sinusoidal. As a result, a reduced switch turn-off loss and reverse recovery of the diode can be expected. The proposed converter is verified with a 24 V input, 160 W - 200 V output prototype.

Novel PWM Method with Low Ripple Current for Position Control Applications of BLDC Motors

BLDC Motors are widely used in various speed control applications due to their ease of control and low cost. Generally, the unipolar PWM method is used for speed control applications. However, the unipolar PWM method has a current spike problem in the braking operation which can be a problem in speed reversal which generally happens in position control applications. However, the current spike problem can be solved by the conventional bipolar PWM method. Although the current spike problem can be solved, the conventional bipolar PWM method has the problem of a large current ripple. In this paper, a novel bipolar PWM method is proposed to solve this problem. The current ripple and the current spike problems are analyzed in this paper for the unipolar and bipolar PWM methods. At last, the merits of the proposed bipolar PWM method are proven by experiment.

Design Method of Digital Optimal Control Scheme and Multiple Paralleled Bridge Type Current Amplifier for Generating Gradient Magnetic Fields in MRI Systems

This paper deals with a digital control scheme of multiple paralleled high frequency switching current amplifier with four-quadrant chopper for generating gradient magnetic fields in MRI (Magnetic Resonance Imaging) systems. In order to track high precise current pattern in Gradient Coils (GC), the proposal current amplifier cancels the switching current ripples in GC with each other and designed optimum switching gate pulse patterns without influences of the large filter current ripple amplitude. The optimal control implementation and the linear control theory in GC current amplifiers have affinity to each other with excellent characteristics. The digital control system can be realized easily through the digital control implementation, DSPs or microprocessors. Multiple-parallel operational microprocessors realize two or higher paralleled GC current pattern tracking amplifier with optimal control design and excellent results are given for improving the image quality of MRI systems.

半波整流電流モードでのペルチェ電流リードによる熱侵入の低減

Experiments of Peltier current lead (PCL) were performed by the way of half-wave-rectified current (HWRC) for an evaluation of the PCL system in the drive with the large-rippled current. The current ripple of the HWRC is large, and we discussed the cooling capability of the current ripple. The experimental results revealed that the temperature difference of the thermoelectric-element (TE) increased with the magnitude of the current in the PCL system, despite the large current ripple. Calorimetric measurements revealed that the PCL reduced the heat leak of 60% for the peak current 90A. We compared the PCL systems of the direct current (dc) mode and the HWRC mode. The results showed that the current dependence of the temperature difference in the HWRC mode did not match that of the dc mode, but those of the heat leak matched well. The performance of the Peltier cooling in the HWRC mode is reduced to be 2/πtime of the Seebeck coefficient for the dc mode by using the time-average method.

A hybrid structure using phase-controlled rectifiers and high-frequency converters for magnet-load power supplies

Thyristor rectifiers are still the preferred choice for large magnet power supplies. However, large harmonic voltages, resulting in large current ripple, and slow dynamic response are major drawbacks of these converters. This paper presents a topology and a control technique for hybrid large-power high-precision magnet power supplies. The system consists of a phase controlled rectifier connected in series with a high-frequency PWM converter. The rectifier is designed to handle the main output power and the PWM converter is used only for harmonics cancellation and error compensation. A feedforward control scheme is proposed to ensure that the desired power sharing is maintained during both the steady state and transient operations. The operating principles of the proposed structure are discussed in the paper, and the results from a 1 kVA experimental setup are provided to validate the proposed topology.

Digital control of induction motor current with deadbeat response using predictive state observer

For a high-power induction motor drive, the switching frequency of the inverter cannot become higher than one kilohertz, and such a switching frequency produces a large current ripple, which then produces torque ripple. To minimize the current ripple, a method based on deadbeat control theory for current regulation is proposed. The pulsewidth modulation (PWM) pattern is determined at every sampling instant based on stator current measurements, motor speed, current references, and rotor flux vector, which is predicted by a state observer with variable poles selection, so that the stator currents are controlled to be exactly equal to the reference currents at every sampling instant. The proposed method consists of two parts: (1) derivation of a deadbeat control and (2) construction of a state observer that predicts the rotor flux and the stator currents in the next sampling instant. This paper describes a theoretical analysis, computer simulations and experimental results.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Deadbeat control of induction motor current using state observer with adaptive poles selection.

For a high power induction motor drive, the switching frequency of inverter can not become higher than several kHz, and such switching, frequency produces a large current ripple, which in turn, produces torque ripple. To minimize the current ripple, a new method based on deadbeat control theory for current regulation is proposed. The PWM pattern is determined at every sampling instant based on stator currents measurements, motor speed, current references and rotor flux vector, which is predicted by a full-order observer with adaptive poles selection, so that the stator currents are controlled to be exactly equal to the reference currents at every sampling instant.The proposed method consists of two parts: (1) derivation of a deadbeat control; (2) construction of a full-order observer which predicts the rotor flux and the stator currents in the next sampling instant. This paper describes a theoretical analysis and computer simulations under various system conditions.

Comprehensive diagnostics of argon plasmajet flows by means of Fabry-Perot interferometry

A comprehensive argon plasmajet flow diagnostic technique, utilizing a plane, pressure-swept Fabry-Perot interferometer with photoelectric detection is described in which all important flow properties are determined to ±10% or better. It is self-consistent in that no reliance is placed on any assumption of equilibrium, other than Maxwellian velocity distributions. High speed digital computer techniques permit emission spectral line width, shift and intensity data to be obtained as functions of jet position and plasmajet power supply current ripple. Radial property distributions obtained from the spectral data include heavy-particle (atom and ion) temperature and velocity, and electron temperature and density. From these results, and measurements of the jet static pressure, are derived the atom and ion densities, Mach number, and total enthalpy distributions. It is observed that for the conditions of these experiments, (1) significant departures from ionization equilibrium occur, in agreement with early theoretical work by Bray, (2) valid time-averaged data can be obtained in the presence of large (here up to 60% peak-to-peak) arc current ripple, and (3) flows with remarkably low radial and axial gradients can be produced by careful attention to the arc current, voltage, and flow rate, and the arc-head, nozzle-exit, and test-chamber pressures.