Voltage Ripple Reduction Research Articles

Active Stabilization of Self-Excited Switched Reluctance Generator Supplying Constant Power Load in DC Microgrids

The voltage control problem of self-exited switched reluctance generator (SRG) supplying a constant power load (CPL) is investigated here. Due to the uncertainties in SRG dynamic and load, conventional linear controllers may not solve the problem and voltage oscillation inevitably appears at high load powers. This article describes a series-damped passivity-based control (PBC) scheme, considering the dynamic performance of SRG, in the presence of CPL. The main objective is to achieve a large-signal stabilization of the output voltage of generator taking into account the uncertainties of SRG. The time-varying nature of back electromotive force (EMF) of SRG is considered by calculating the bound of damping injection terms. By an adaptation mechanism to deal with the time-varying inductance and back EMF, together with the proposed PBC, a large-signal active damping adaptive-passivity-based controller (APBC) is obtained to reduce the output voltage oscillations. The effectiveness of the proposed control scheme in stabilization in SRG and CPL and voltage ripple reduction is demonstrated, using a four-phase, 8/6 pole drive system.

Fuzzy Logic Speed Control of Permanent Magnet Synchronous Machine and Feedback Voltage Ripple Reduction in Flux-Weakening Operation Region

Voltage feedback flux-weakening control has the advantages of simplicity and robustness against parameter variation. However, due to less voltage control margin in the flux-weakening region, the increased feedback voltage ripple could deteriorate the system performance in the flux-weakening region and may even cause oscillation. In this article, based on a nonsalient permanent magnet synchronous machine, the steady-state feedback voltage ripple in the flux-weakening region are analyzed first. It shows that the feedback voltage ripple caused by the current command ripple could dominate in some flux-weakening regions. Consequently, the speed bandwidth based on the conventional speed proportional-integral (PI) controller in the flux-weakening region can be hardly increased, which leads to poor dynamic performance. In order to obtain both fast speed dynamics and less steady-state ripple, especially in the flux-weakening region, an adaptive fuzzy logic (FLC) speed controller is designed and compared with the conventional speed PI controller. With the adaptive FLC, the dc-link voltage utilization can be increased and better flux-weakening capability can be obtained. Finally, the improved performances are verified by the experimental results.

Half-Bridge Modular Switched-Capacitor Multilevel Inverter With Hybrid Pulsewidth Modulation

In order to explore a single-phase microinverter with boosting ability, simple structure, low-cost, and high power density, a new structure of a multilevel inverter (MLI) is proposed in this article. With this structure, two half-bridge modular switched-capacitor circuits are arranged on both left- and right-sides of a dc source. Circuit configuration of this MLI can be bilaterally symmetrical and this benefits to modular design and the voltage stress reduction of inverting bridges. Additionally, in order to reduce voltage ripple of capacitors and total harmonic distortion of output voltage simultaneously, a hybrid pulsewidth modulation strategy is developed to improve the performance of this MLI. As a result, capacitors of this MLI can be replenished repeatedly when they are taken as voltage sources to generate different voltage levels. Circuit configuration, operation principle, modulation, power loss, and voltage ripple are analyzed in detail. Both simulation and experimental results are provided to demonstrate the effectiveness of the proposed MLI and modulation strategy.

Reduction of Half-Arm Current Stresses and Flying-Capacitor Voltage Ripples of Flying-Capacitor MMCs

In this paper, a new control scheme that can reduce the current stresses on switching devices, flying capacitors, and inductors for flying-capacitor modular multilevel converters (FC-MMCs) is proposed, which is based on redistribution of power difference between upper and lower arms through the flying capacitors. In addition, a way to determine the frequency range of the square-wave voltage to be injected into the FC-MMC is suggested, which is able to improve the current control performance and reduce the flying-capacitor voltage ripples. The effectiveness of the proposed control scheme has been verified for a 4160-V/1-MW simulation model and a 230-V/3-kW prototype of the FC-MMC.

Offset Voltage and Output Voltage Ripple Reduction of an Operational Amplifier using Auto-zero Technique

Offset Voltage and Output Voltage Ripple Reduction of an Operational Amplifier using Auto-zero Technique

Instantaneous Pulse Power Compensator for High-Density Single-Phase Inverters

In this paper, instantaneous pulse power compensator (IPPC) method is proposed to achieve power pulsation decoupling function for single-phase inverter applications. A smaller capacitor is placed in series with the traditional dc-link capacitor, and this smaller capacitor voltage is controlled using pulse currents to cancel out the dc-link voltage ripple. Unlike twice-line-frequency power decoupling method, the proposed IPPC method can compensate the pulsating power with all the orders harmonics on the dc-link line, not only the second-order component. Both modeling and simulation results show that IPPC method can achieve nearly zero voltage ripple for the dc-link capacitor since the pulse current is fully compensated. Whereas twice-line-frequency power decoupling method has limit in voltage ripple reduction, especially in small dc-link capacitance conditions. The experimental results based on a full-bridge topology decoupling circuit and a single-phase inverter application show consistent results with simulation results. A 16% reduction of the prototype size, i.e., 16% higher power density with only ∼1% efficiency penalty can be achieved by the proposed IPPC method when compared to the second-order power decoupling method.

A DC-Link Capacitor Voltage Ripple Reduction Method for a Modular Multilevel Cascade Converter With Single Delta Bridge Cells

This article proposes a capacitor voltage ripple reduction method used for a modular multilevel cascade converter (MMCC) with single delta bridge cells (SDBC), by applying a third harmonic zero-sequence current. A practical case study on an 80 MVar/33 kV MMCC-SDBC-based STATCOM is used to demonstrate the method. The impact of the third harmonic zero-sequence current level of the capacitor ripple reduction and the electrothermal stresses on insulated gate bipolar transistor modules are analyzed. An optimal parameter of the current level is obtained by compromising the above-mentioned performance factors. The obtained result shows that the required capacitance, as well as the capacitor bank volume, is reduced by 20% without increasing the total power semiconductor losses by using the proposed method.

Energy Storage Requirement Reduction Using Negative-Voltage States of a Full-Bridge Modular Multilevel Converter

Utilization of negative-voltage states substantially reduces the energy storage requirements of a full-bridge submodule-based modular multilevel converter (FB-MMC). This study provides a detailed analysis of the capacitor voltage ripple and energy storage requirement reduction effects of the FB-MMC by utilizing negative-voltage states. The analytical expressions of capacitor voltage ripple following the change in negative-voltage state factor (NVSF) are derived. Results show that the capacitor voltage ripple reduction effects using negative-voltage states are strongly correlated with the operated power factor angle. In addition, the second-order ripple component must be considered to increase the accuracy in evaluating the voltage ripple reduction effects. This study defines the energy storage reduction factor (ESRF) to indicate the level at which the energy storage requirement can be minimized by selecting an appropriate NVSF for a given permitted operating range of the power factor angle. The curve of the ESRF following the change in the permitted operating range of the power factor angle was calculated. The analytical method and the evaluation results for the capacitor voltage and energy storage reduction effects of the FB-MMC using negative-voltage states are verified on the basis of the simulation and experimental results.

Optimum Boundary Inductance Control Concerning Limited PF for a DCM Boost PFC Converter

The discontinuous conduction mode boost power factor correction converter features zero-current turn- on for the switch, no reverse recovery in diode, and constant frequency operation. With traditional constant duty ratio control, the power transfer in each switching cycle exhibits great difference during a half-line cycle. Consequently, the peak and root mean square values of the inductor current are large, the same goes for the switch and diode. This increases not only the current stress of the power components but also the conduction and switching turn- off loss, and lowers the efficiency of the converter. Introducing third and fifth harmonics into the input current and varying the duty cycle correspondingly can reduce the aforementioned power transfer difference, and provide huge space for the increment of boundary inductance as well. An optimum boundary inductance control concerning limited power factor (PF) is proposed in this paper. For the maximum boundary inductance of the converter within wide input voltage range, the optimum harmonics amounts are analyzed and figured out. The proposed method brings about efficiency improvement, output voltage ripple reduction, and PF increase as well, especially at high input voltages. A prototype has been built and the experimental results are presented to show the validity of the scheme.

Simulated topology of doubly powered asynchronous motor with diode clamped inverter

This paper deals with the problem of modelling, control and analysis of a doubly-powered induction machine (DPIM) using a three-level three-phase voltage source inverter known simply as diode clamped inverter (DCI) with a three-phase diode rectifier and a DC link in between. A mathematical model of DPIM and the associated DCI circuit is developed. The stator circuit of the DPIM is supplied directly from an ac system network while its rotor side is supplied via a variable frequency DCI. A multi-loop nonlinear field controller is developed to meet an accurate motor speed, regulation of the mechanical load torque and the overall system power. The results obtained from the simulation in the environment of Simplorer 7 show that the proposed DCI inverter offers great optimisation, little overshoot, and reduced voltage ripples. Consequently, the dynamic behaviour of the motor and the energy efficiency of the overall system are progressively improved and a complete suppress of the influence of the variation in the motor load on the speed of the motor is achieved.

Simulated topology of doubly powered asynchronous motor with diode clamped inverter

This paper deals with the problem of modelling, control and analysis of a doubly-powered induction machine (DPIM) using a three-level three-phase voltage source inverter known simply as diode clamped inverter (DCI) with a three-phase diode rectifier and a DC link in between. A mathematical model of DPIM and the associated DCI circuit is developed. The stator circuit of the DPIM is supplied directly from an ac system network while its rotor side is supplied via a variable frequency DCI. A multi-loop nonlinear field controller is developed to meet an accurate motor speed, regulation of the mechanical load torque and the overall system power. The results obtained from the simulation in the environment of Simplorer 7 show that the proposed DCI inverter offers great optimisation, little overshoot, and reduced voltage ripples. Consequently, the dynamic behaviour of the motor and the energy efficiency of the overall system are progressively improved and a complete suppress of the influence of the variation in the motor load on the speed of the motor is achieved.

Passivity-Based Control of Switched Reluctance-Based Wind System Supplying Constant Power Load

This paper presents a passivity-based control (PBC) scheme for the switched reluctance generator (SRG) in small-scale wind energy conversion systems for dc microgrid applications. The main objective is to stabilize the output voltage in case the system supplies constant power loads (CPLs) and operates with maximum power point tracking (MPPT). Stability improvement and dc-link ripple reduction in the presence of CPLs is achieved using system-level modeling of SRG-based dc microgrid through the Euler-Lagrange system (ELS) from the viewpoint of the machine physical structure. Compared with other control methods, the proposed MPPT method based on passivity-based speed controller employs the back electromotive force (EMF) in the generation process as a position-dependent voltage source to overcome the major challenge of SRG complicated uncertain dynamic model. To deal with the time-varying inductance and back EMF of SRG, an adaptation mechanism is incorporated in the proposed adaptive PBC and the control design is constructed by using the Lyapunov theorem where the closed-loop stability is ensured. The effectiveness of the proposed method in avoiding instability effects of SRG and CPL with voltage ripple reduction and precise wind turbine speed tracking is investigated with simulation results and validated with experimental by using a four-phase, 8/6 SRG drive system.

Coordinated control of power loss and capacitor voltage ripple reduction for AC voltage boosted FBSM MMC with second harmonic circulating current injection

Reducing the converter loss, sub-module voltage ripple and handling DC short-circuit faults in high-voltage direct current systems are crucial for the economical and reliable operation of modular multilevel converters (MMCs). This study proposes a coordinated control method of power loss reduction and capacitor voltage balancing for AC voltage boosted full-bridge sub-module (FBSM)-MMC by controlling the second harmonic component in the circulating current. The relationship between converter loss and second harmonic circulating current (SHCC) is firstly derived for AC voltage boosted FBSM-MMC. From the analysis, it can be seen that the converter loss and ripple can be optimised by injecting the SHCC into the arm current when compared with SHCC elimination. Simulation results of an AC voltage boosted FBSM-MMC with typical parameters using PSCAD/EMTDC confirm the feasibility and validity of the proposed loss and ripple reduction method.

Hybrid-modulation-based control technique for reduction of output voltage ripples in frequency-modulated switch-mode power converters

<span>In this paper a novel control technique for switching-frequency-modulated switch-mode power converters (SMPC) operating in discontinuous conduction mode is proposed. The use of the technique leads to significant reduction in peak-to-peak output voltage and peak currents increased due to straightforward application of switching frequency modulation (SFM). The technique is based on hybrid modulation scheme in which both switching frequency and duty ratio are modulated simultaneously by the same modulation signal. Theoretical analysis and experimental verification of the proposed technique are presented in details. Both computer simulations and experiments show that switching-frequency-modulated SMPC with the proposed control technique in comparison to SMPC without SFM has appreaciably lower conducted electromagnetic emissions, at the cost of slightly increased peak-to-peak output voltage and peak currents.</span>

Reduction of Torque and Voltage Ripple in a Doubly Salient Permanent Magnet Generator

Large torque and voltage ripple are inherent drawbacks of doubly salient generators. This paper first introduces torque sharing function (TSF) into the application of a dual-channel three-phase 12/8 poles doubly salient permanent magnet generator (DSPMG) to reduce torque and voltage ripple. Based on the principle of copper losses minimization, a new TSF is proposed through theoretical analysis and numerical computation. The proposed TSF is compared to conventional TSFs according to three evaluation criteria. In order to achieve satisfying and consistent steady state and dynamic performances over the whole operation range, gain scheduling PI controller is adopted to overcome the highly nonlinear characteristic of the DSPMG. Besides, with compensators of back-EMF, cogging torque and losses adopted as feed-forward, a dual closed-loop generation control system is detailed designed. Both simulation and experimental results verify the effectiveness of the proposed control system and the copper losses minimization TSF in reducing torque and voltage ripple.

GPS Synchronization of Smart Distributed Converters for Microgrid Applications

In this paper, a smart distributed DC/DC converter synchronization advanced technique and phase angle optimization algorithm are proposed using to reduce the DC bus overall ripple. A global positioning system-based scheme is used to synchronize the carrier among the distributed converters. The carrier phase angle optimization among the different converters is inspired by Carrier-Sense Multiple Access protocol. The proposed system is simulated and analyzed using Matlab/Simulink program. As a proof of concept of the proposed technique, two case studies have been investigated under equal and unequal load sharing among the distributed generators. The proposed algorithm shows a significant reduction in the DC bus voltage ripple. To prove the concept, a laboratory test-bed has been built and the proposed algorithm has been implemented to validate the theoretical and simulation results. The close agreement between the experimental and simulation results demonstrates the effectiveness and validity of the proposed algorithm.

추진장치 성능시험설비의 출력 전압 리플 저감 필터에 관한 연구

추진장치 성능시험설비는 추진 인버터와 모터의 조합인 시험체의 성능시험과 추진장치의 개발 또는 인증 단계에서 추진장치의 성능을 시험하고 검증하는 장비이다. 추진장치 성능시험설비는 교류전원설비에서 공급되는 교류를 변환하여 부하제어설비가 요구하는 직류전원을 제한된 범위 내에서 안정적으로 제어할 수 있어야 한다. 본 논문에서는 추진장치 성능시험설비의 동작 특성에 따른 출력전압 리플 신호의 크기를 분석하고, 이를 바탕으로 전압 리플 저감 필터의 설계 방법에 대하여 정립하고자 한다. 설계된 전압 리플 저감 필터는 컴퓨터 기반 시뮬레이션 결과와 실험을 통하여 검증한다.

A High-Frequency Three-Level Buck Converter With Real-Time Calibration and Wide Output Range for Fast-DVS

This paper presents a 50-MHz 5-V-input 3-W-output three-level buck converter. A real-time flying capacitor ( $C_{F}$ ) calibration is proposed to ensure a constant voltage of $V_{g}$ /2 across $C_{F}$ , which is highly dependent on various practical conditions, such as parasitic capacitance, time mismatches, or any loading circuits from $C_{F}$ . The calibration is essential to ensure the reliability and minimize the inductor current and output voltage ripple, thus maintaining the advantages of the three-level operation and further extending the system bandwidth without encountering sub-harmonic oscillation. The converter is fabricated in a UMC 65-nm process using standard 2.5-V I/O devices, and is able to handle a 5-V input voltage and provide a 0.6–4.2-V-wide output range. In the measurement, the voltage across $C_{F}$ is always calibrated to $V_{g}$ /2 under various conditions to release the voltage stress on the high- and low-side power transistors and $C_{F}$ , and to ensure reliability with up to 69% output voltage ripple reduction. A 90% peak efficiency and a 23–29-ns/V reference-tracking response are also observed.

Plug-and-Play Voltage Ripple Mitigator for DC Links in Hybrid AC–DC Power Grids With Local Bus-Voltage Control

In this paper, a straightforward plug-and-play voltage ripple mitigator (RM) is proposed. Unlike existing voltage ripple reduction methods, the proposed device can be attached to the dc link of a hybrid ac–dc power system without modifying the host system itself. In particular, a local bus-voltage control scheme is employed to achieve the plug-and-play operation. With the requirement of the dc-link voltage measurement only, this device can be operated as a standalone module. Theoretical analysis and experimental work on a boost-type power factor correction rectification system have been successfully performed to validate the effectiveness of the ripple-mitigating function, the hot-swap operation and the nonintrusive property of the RM. Practical results obtained from a 110-W miniature hybrid ac–dc power system comprising an ac/dc converter and two resistive loads are included to demonstrate some of the functions of the RM.

Landsman Converter Based Particle Swarm Optimization Technique

This paper proposes a novel control technique for landsman converter using particle swarm optimization. The controller parameters are optimized by pso algorithm,the proposed algorithm is compared with pid controller and the comparative results are presented. Simulation results shows the dynamic performance of pso controller. landsman converter reduction in output voltage ripple in the order of mV along with reduced settling time as compared to the conventional pid controller . The simulated results are executed in MATLAB/SIMULINK.