Search

Connection of an LC filter to the output of voltage source inverter (VSI) in squirrel cage induction motor (SQIM) drive converts the pulse-width modulated (PWM) voltages into smooth sinusoidal voltages. However, this connection may lead to closed-loop instability in the rotor flux-oriented (RFO) vector-controlled (VC) SQIM system. The closed-loop stability of the combined SQIM + LC filter (SQLC) system is complex and has not been analyzed properly in the literature. In this paper, a detailed closed-loop stability analysis of the SQLC system has been presented based on stability region (SR) and accordingly the PI gains of VC has been designed. The SR method is adopted to derive the common stability regions for the SQIM system and SQLC system. Thereby, the paper proves that connecting an LC filter in-between the VSI and the SQIM system does not always destabilize the closed-loop system. Further, for an SQLC system, the complete range of current controller gains is obtained at various operating points. The frequency-domain specifications have been used to select a proper stabilizing set and the effect of parametric variation of LC filter on the stabilizing set has also been discussed. The experimental results are provided to validate the analysis. [ABSTRACT FROM AUTHOR]

Light-emitting diodes (LEDs) are widely used in street lighting, landscape lighting, liquid crystal display (LCD) backlighting, healthcare, etc. As an important part of LED lighting products, LED driver plays a vital role in maintenance costs reduction, energy saving and lifetime prolongation. In this paper, a single-stage LED driver is proposed, which is integrated by a totem-pole bridgeless power factor correction (PFC) unit and several modular LCL-T resonant rectifiers. The totem-pole bridgeless PFC unit and the LCL-T resonant rectifiers are integrated by sharing switches, which can simplify the circuit and reduce the system cost. The output current can be regulated by applying the variable inductor control. Constant duty cycle and fixed switching frequency operation can be achieved as well. The operating principle and the performance of the proposed converter are analyzed in this paper. In addition, a precise parameter design method is proposed by considering the high-order harmonics. At last, an experimental prototype is established to validate the proposed parameter design and variable inductor control method. [ABSTRACT FROM AUTHOR]

This paper presents a simple pulse width modulation algorithm for control of an ultracapacitor based energy storage system used for source and load support applications. As opposed to dual loop control philosophy that is widely used for backup applications, this paper presents a simple single loop current control that is only useful for controlling the ultracapacitor based DC/DC converters used in source and load support applications. The proposed PWM blocking method necessitates the DC/DC converter to operate in five states and takes into consideration the essential operational limits associated with the ultracapacitors. The performance of the proposed algorithm is verified experimentally using a 24 V laboratory prototype setup. Further, the shortcomings of dual loop control when applied to source and load support applications are demonstrated. [ABSTRACT FROM AUTHOR]

When the permanent magnet synchronous motor (PMSM) works in the high-speed region with low carrier ratios, the performance of the rotor flux observer has a great influence on the loading capacity and stability of the speed sensorless vector control system. The problem of the adaptive compensation flux observer (ACFO) of the PMSM at low carrier ratios is analyzed in this paper, and an ACFO with a feedback delay component is presented. After retuning the PI regulator parameters, the new expression related to carrier ratio is obtained, which can improve the performance of the flux observer at low carrier ratios and make the torque and current loop response faster. Meanwhile, the stability of different Euler approaches of the integrator for ACFO in the discrete domain is analyzed, and a new Euler with a coefficient is proposed to combine the merits of the backward Euler and the trapezoid Euler. It shows better performance at low carrier ratios. Finally, the effectiveness of the discrete ACFO is verified by experiments. [ABSTRACT FROM AUTHOR]

An improved two-stage model predictive current control (MPCC) for three-phase three-level converters in the paper, which can simultaneously achieve common-mode voltage (CMV) reduction, effective dc-link capacitor voltage control, and decreased computational burden, is proposed. Compared to the other current control strategies, it has the capability of handling multiple control objectives and possesses a simple structure. Furthermore, it greatly reduces the CMV since the peak CMVs of all the candidate voltage vectors are constrained to be less than one sixth of the dc-link voltage. In addition, an optimal two-stage voltage vector selection mechanism is employed in the proposed method. It helps to significantly reduce the computational complexity. Simulation and experimental results are provided to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents Space Vector Modulation (SVM) sequences that reduce Common Mode Voltage (CMV) in Dual Three-phase Asymmetrical Induction Motor (DTAIM). At first, two existing SVM techniques such as Reference SVM (RSVM) and CMV1 are studied. Additionally, three new switching sequences are developed as CMV2, CMV3 and DCMV3, which reduce peak magnitude of CMV by 66.8% in comparison with RSVM technique. In SVM techniques, to obtain least CMV, zero vectors are usually replaced by two opposite large Active voltage Vectors (AV) with equal time duration. In such topologies like CMV1, total six AVs are utilized to synthesize the reference vector. The proposed SVM technique CMV2 utilizes only five large AVs to synthesize the reference vector and reduces CMV. Selection of five neighbouring AVs is reflected in reduction of harmonic flux trajectories and stator current ripple in proposed techniques. Additionally, two more switching sequences (CMV3 and DCMV3) are developed related to utilization of specific zero voltage vectors in all sectors (7 and 56) that produce zero CMV. These two switching sequences also provide easy implementation feature during the development of c-code program. In this study, CMV and stator current ripple are considered as performance parameters for different SVM techniques. All SVM techniques are analysed by analytical results, computer simulations, and using prototype test setup of DTAIM fed by Dual Three-phase Voltage Source Inverters (DTVSIs). [ABSTRACT FROM AUTHOR]

The implementation of finite-control-set model predictive control (FCS-MPC) in voltage source inverters (VSIs) can make the system suffer from poor current harmonics performance, which may complicate the design of the required AC filter. To overcome this shortcoming, a carrier-based modulated model predictive control (CB-MMPC) strategy is proposed in this paper. This method enables the utilization of existing PWM modulation techniques with FCS-MPC, where a modulation waveform with zero-sequence signal injection is generated and compared to a triangular carrier wave, while optimizing the selection of the switching states. As it is shown, the studied CB-MMPC strategy not only considerably improves the current total harmonic distortion (THD) but also attains the performance of fast current dynamic response and robustness as the traditional FCS-MPC. Herein, the detailed implementation of the CB-MMPC control strategy is given, while considering its application to the current feedback control loop of a three-phase three-wire two-level VSI modulated at constant switching frequency. Finally, PLECS circuit simulation and a 3-kW VSI prototype are used to verify the superiority and the effectiveness of the presented CB-MMPC strategy. This is also benchmarked to the FCS-MPC and dead-beat based controllers. [ABSTRACT FROM AUTHOR]

This paper proposes a novel dual input nine-level inverter (DINLI) topology which requires only seven controllable devices. The dual inputs are un-identical DC voltage sources in the ratio 1:3. A simple control scheme is derived by appropriately modifying the phase disposition pulse width modulation technique to generate high-quality 9-level output from the DINLI topology. At any given instant, a maximum of four switches conduct out of which only a maximum of two switches operate at high frequency, bringing down the switching and conduction losses significantly and improving the overall system efficiency. The bidirectional DINLI (BDINLI) topology with reactive power capability can be realized by replacing the unidirectional devices with the controlled switches (i.e., total nine switches). In addition, the proposed DINLI topology does not require extra voltage balancing circuits which further improves the efficiency. The DINLI operation is verified through MATLAB simulations for grid-connected applications and its extension to an n-level, 3-phase application is also investigated. Experiments performed on a 1KVA laboratory prototype to validate the theoretical claims. [ABSTRACT FROM AUTHOR]

A power systems of wearable application requires high power conversion efficiency and bidirectional power flows to obtain the compatibility with various power sources and loads. The conventional flyback converter has a simple structure and bidirectional power conversion capability. However, it shows poor power conversion efficiency caused by hard-switching operation, high DC offset current on the transformer, snubber losses, and large peak current. In this paper, a current-fed CLLC resonant converter is proposed to obtain the high power conversion efficiency and the bidirectional power conversion capability. The soft-switching operation, zero DC-offset current, and small peak current can induce high power conversion efficiency. The asymmetric pulse width modulation (APWM) regulates the bidirectional power flows and the output voltage. The design methodology of the proposed converter is analyzed by introducing its operational principles. The performance of the proposed converter is experimentally verified with a 20 W prototype. [ABSTRACT FROM AUTHOR]

This paper presents an investigation into sideband vibro-acoustics suppression of the permanent magnet synchronous motor (PMSM), associated with several periodic signal-based dithering modulations. Mathematical derivations of four typical periodic signal-based schemes are deduced with the power spectral density (PSD) method. The individual modulation parameters, such as bandwidth and modulation ratio, are determined the values to minimize the sideband vibro-acoustics. The frequency distributions of the sideband components are discussed by the analytical derivations. The relationship between the electromagnetic components and mechanical responses is reconstructed by coupling with temporal features. For verification, the experimental tests with a prototype PMSM are introduced under different operational conditions. According to the results and figures, both magnitude suppression and frequency distribution are accurately correlated with sideband harmonic components as well as vibro-acoustic responses. This investigation thus clearly holds promise for the evaluation and optimization in powertrain used by electric vehicles. [ABSTRACT FROM AUTHOR]

A new transformer-less three-level grid-tied inverter is proposed in this article. By employing the switched-capacitor (SC) modules, a new topology is derived. The proposed topology has some features which are high efficiency, the capability of voltage boosting without utilization of any additional boost stage, and suppressing the leakage current by using common grounded strategy. In this article, a peak current control is employed to generate the gate pulses of power semiconductor switches and adjustment of both active and reactive powers. By doing so, the grid injected current is controlled and adjusted to have a proper quality. The operation modes, design consideration, and a comparison with some recently proposed grid-connected topologies are done through this paper. Finally, the performance and feasibility of the proposed inverter are confirmed with a 500 W experimental prototype. [ABSTRACT FROM AUTHOR]

Nowadays, one of the challenges in transport electrification is the reduction of the components’ size and weight in order to improve the power density. This is often achieved by designing electrical machines with higher rotational speeds and excitation frequencies. In addition, the converter needs to control the machine over a wide speed range given by the mission profile. Therefore, copper losses can significantly increase due to the combination of high frequency excitation and the harmonics introduced by the converter. The winding arrangement design plays a key role in the minimization of the copper losses, thus towards a higher efficiency and/or an improved power density. Different winding topologies can be adopted for high speed electrical machines and amongst them random windings are still one of the most widespread types. This paper presents an in depth study on AC losses in random windings for high frequency motor applications. An analytical method is compared against 2-D Finite Element (FE) simulation results. These are then compared to experimental measurements taken on a custom motorette. Importantly, in order to take into account the random positions of each strand within the machine slots, an Experimental Statistic Method (ESM) is proposed. The ESM allows to define the probability distribution which is useful to evaluate the winding copper losses at the design stage. The contribution of the Pulse Width Modulation (PWM) effect is also considered and experimentally evaluated. [ABSTRACT FROM AUTHOR]

Permanent magnetsynchronous motors (PMSMs) are usually driven by the SVPWM technique, which leads to annoying sideband noise near the switching frequency. Traditional random modulation techniques increase the possibility of resonance with the motor structure. This study proposes a novel random pulse position modulation-based strategy to eliminate the current harmonics and electromagnetic noise at a specific frequency. The proposed method adopts a constant switching frequency. A unique design between the pulse position and duty ratio cancels the current harmonics and acoustic noise at the selected frequency. The results show that resonance can be avoided effectively if the chosen frequency is close to the natural frequency. It is concluded that the proposed method is beneficial at lower fundamental frequencies. The techniques can substitute classic random modulation techniques with variable switching frequency in the low speed applications. [ABSTRACT FROM AUTHOR]

To further improve the reliability of the open-end winding permanent magnet synchronous motor (OW-PMSM) and avoid the secondary damage caused by the common-mode voltage (CMV) in the event of bridge-arm failure, a CMV suppression technique is proposed. With the proposed technique, the reference voltages in three-phase stationary coordinate system are optimized to adapt the characteristics of OW-PMSM with five bridge arms. Further, an improved modulation scheme is proposed, in which the CMV is suppressed and the switching actions within every control cycle is reduced. The effectiveness of the proposed technique is validated through experimental results. [ABSTRACT FROM AUTHOR]

In order to better address the problem of many high-order harmonics’ concentration in the output voltage, a novel five-phase piecewise-random-switching-frequency space vector pulse width modulation (PRSF-SVPWM) strategy is proposed for a five-phase voltage source inverter. Compared to the conventional random switching frequency SVPWM (RSF-SVPWM), the entire fundamental period of this method is divided into two half-fundamental periods, so the original switching frequency in a single fundamental period is randomized in segments respectively. During this process, parameters named the offset frequency and random frequency are defined and assigned reasonably. In this way, high-frequency harmonics in one period are spread into a wider range. Subsequent simulation and experimental results verify that the proposed random modulation strategy can further reduce amplitudes of harmonics near switching frequency and its integer multiples, even though within a narrow switching frequency range, and a satisfactory effect of high-order harmonic dispersion is finally obtained, which contributes to the application and popularization of random pulse width modulation strategies. [ABSTRACT FROM AUTHOR]

This article proposes and investigates a control technique for vibration and acoustic noise reduction in Switched Reluctance Machines (SRMs). A large vibration generally occurs at the turn-off stage of SRM phase voltage due to a sudden decrease in the attraction force. The proposed technique is a smooth voltage Pulse-Width Modulation (PWM) method that utilizes the PWM technique to reduce the rate of change of voltage during the turn-off commutation angle. The aim of this proposed method is to control the vibration with high PWM frequency at the very beginning stage when the vibration is low before being developed into higher amplitude at the turn-off stage, without having to generate anti-phase vibration. Both simulation and experimental testing are implemented to confirm the capabilities and limitations of this technique. [ABSTRACT FROM AUTHOR]

In this article, we introduce an improved multi-sampling-based alternate current (ac) controller that can be applied to ac machine drives or grid-connected inverters. Unlike the classical multi-sampling controller, whose performance is restricted by the transport delays in the feedback acquisition chain, the improved internal model control-based controller can provide a high closed-loop bandwidth by shortening the averaging range and inserting a cascaded differential multiplier. The corresponding modified controller structure for embedding active resistance feedback could improve the disturbance rejection ability while maintaining unchanged closed-loop performance for tracking reference. Besides the common perspectives for current controller design, discussions about robustness to parameter variations, implementation issue concerning sampling noise immunity affected by the pulse-width modulation output method, the effect of execution time, and application with high fundamental frequency are also presented. Finally, the comprehensive experimental results are obtained from a platform with a three-phase inverter, digital controller, and a surface-mounted permanent magnet synchronous motor. The results verify that the proposed controller achieves a high closed-loop bandwidth of up to 20% of the sampling frequency without overshoots and oscillations. [ABSTRACT FROM AUTHOR]