DC Link Components Research Articles

High-Frequency Link Matrix Rectifier in Discontinuous Conduction Mode With Reduced Input Current Distortion

High-frequency link matrix rectifier (HFLMR) is advantageous in three-phase isolated ac–dc conversion due to its elimination of dc-link components. However, the input current distortion increases in an HFLMR when it operates in discontinuous conduction mode (DCM). The modulation scheme forms the high-frequency link current shape, which directly affects the input current distortion. Space vector pulsewidth modulation (SVPWM) is a popular modulation method for the matrix-type converter for its flexibility of arranging switching vectors. In this article, a new switching scheme based on SVPWM is proposed for the HFLMR to improve the current quality in DCM without adding complexity to the control. In DCM, the resonance between diode capacitance and transformer leakage inductance becomes a source of converter harmonics and instability. The method of shorting the transformer secondary is implemented to eliminate the voltage and current ringing in the discontinuous period. A 600-W lab prototype HFLMR that converts 115Vrms, 400-Hz three-phase input voltage to 270-V dc output voltage is implemented for experimental verification of the proposed switching scheme and converter topology. With the proposed switching scheme, the input current distortion is effectively reduced. With the proposed topology, the high-frequency voltage and current ringing are eliminated.

Analytic Spectral Analysis Technique for Converters Operating With Oscillatory DC-Link Voltage Components

Converters are playing an ever increasing role in electric power grids. To help facilitate a design of power grids that ensures stable and efficient transfer of power, the harmonic pollution injected by converters must be quantified. At present, analytic expressions used to describe modulated converter waveforms have been derived while assuming that the converter dc-link voltage contains only a dc component. This is a reasonable assumption in many converter applications. However, there is a large number of converters that operate with superimposed oscillatory dc-link components, such as single-phase and cascaded multilevel converters. Grid and/or load imbalance can also lead to oscillatory dc-link voltage components. Given this context, the main contribution of this article is to derive analytic expressions for converter output harmonics when oscillatory components are present in the dc-link voltage. Experimental verification of the proposed spectral analysis technique is performed on a $\text{1}\,\text{kVA}$ , 3-level, $\text{240}\,\text{V}$ single-phase full-bridge inverter.

High‐efficiency three‐phase bidirectional dc–ac converter for energy storage systems

This study presents a high-efficiency three-phase bidirectional dc–ac converter for use in energy storage systems (ESSs). The proposed converter comprises a modified three-level T-type converter (M3LT2C) and a three-level bidirectional dc–dc converter. The M3LT2C comprises two T-type cells to interface with a three-phase grid. By directly connecting the S-phase of the grid to a neutral point on the dc link, the active and passive components are required for only two grid phases, which reduces power losses, system volume, and production cost. A direct nominal voltage compensation control algorithm enables the converter to obtain high grid power quality. Also, the three-level bidirectional dc–dc converter enables low switching and conduction losses with reduced voltage stress across the switches. In addition, a simple dc-link voltage-balancing algorithm enables the balancing of two split dc-link capacitor voltages. To confirm the theoretical analysis of the proposed converter and assess its validity, a 10-kW prototype was implemented and tested.

A High-Frequency Link Matrix Rectifier With a Pure Capacitive Output Filter in a Discontinuous Conduction Mode

High-frequency link matrix rectifier (HFLMR) is an isolated single-stage three-phase ac–dc converter, which originates from the three-phase matrix converter and inherits the advantages of matrix rectifier such as no dc-link components. In this paper, an HFLMR for more electric aircraft system is proposed. The proposed HFLMR consists of a three-phase input LC filter, a matrix rectifier, a high-frequency transformer, a diode bridge rectifier, and a purely capacitive output filter. The elimination of output filter inductor clamps the output rectifier device off-state voltage to the output voltage and eliminates any RC snubber across the rectifier. A novel symmetric modulation scheme based on space vector modulation is implemented to regulate the switching sequences and provide selective natural zero voltage switching and zero current switching of the devices of the matrix bridge. The proposed converter is more power-dense since it eliminates the dc-link components, output filter inductor, and lossy snubber across the output rectifier devices. A TI digital signal processor TMS320F28379D is used to process the converter signals and generate the gating logic. The proposed converter is validated on a laboratory prototype powered by 115 $V_{{rms}}$ ac with frequency of 400 Hz. The isolated dc output voltage is regulated at 270 V dc and the maximum output power is 600 W.

Dynamic inverse controller with Matrix Converter Drive Feed Three Phase Induction Motor

Dynamic inversion (DI) is a controller technique by which existing undesirable dynamics are cancelled out and changed by desirable dynamics. The application of induction motor drives with sinusoidal input currents a matrix converter combined with DI is used which directly connects a three-phase input voltage source to a three-phase (AC-AC converter) without dc-link components. This paper presents a novelty of using nonlinear dynamic inverse controller with matrix converter topologies on three phase induction motor. The efficiency of the converter and their modulation techniques for the implementation of the strategies is increased. The speed response tracking and torque ripple minimization is achieved. The robustness of the proposed method has been confirmed from simulation and experimental model.

Modelling and simulation of matrix converter under distorted input voltage conditions

Matrix converter is an energy conversion device which directly connects a three-phase voltage source to a three-phase load without dc-link components. Therefore, the output of the matrix converter is directly affected by the disturbance or imbalance in the input voltages. Many researchers have made an effort to overcome this problem in recent years. In this paper, the behaviors of the matrix converter controlled with the optimum-amplitude Venturini method are investigated and a novel compensation technique based on fuzzy logic controller is proposed to eliminate the undesirable influences of the input voltage under the distorted input voltage conditions. The proposed technique is based on closed loop control of the three-phase output current to enhance the output performance of the matrix converter. The mathematical model of the proposed system is developed. The simulation of the development model is performed in Matlab&Simulink. Some results demonstrating validity of the proposed compensation technique are presented.

입력 전원 외란 상황에서의 신경회로망 기반 전류 보상기를 이용한 매트릭스 컨버터의 출력 전류 개선

Matrix converter is an energy conversion device of controlled power semiconductor switches that directly connects the three-phase source to the three-phase load. With no dc-link components for energy storage in the matrix converter the input current depends directly upon the load currents and the switch state of the converter. Therefore the unbalanced and distorted input voltages can result in unwanted output harmonic currents. This paper presents a current compensator based on neural network to improving output current quality for matrix converter under abnormal input voltage conditions. The effectiveness and feasibility of the proposed technique has been proven through numerical simulations and experimental tests.

Relation between Overvoltage at DC Link and Parameters of AC Filter in Case of Overload Protection of a Converter without DC Link Components

Relation between Overvoltage at DC Link and Parameters of AC Filter in Case of Overload Protection of a Converter without DC Link Components

Study of dead time of PWM rectifier of Voltage-source inverter without DC-link components and its operating characteristics of induction motor

A voltage-source inverter without dc-link components is an ac-to-ac converter having dual bridges of a pulsewidth-modulated (PWM) rectifier and a PWM inverter that can be controlled independently. While conventional matrix converters have disadvantages, such as a complicated commutation scheme and necessity of a large-sized clamp circuit, commutation, and protection of our inverter can be implemented easily. In order to control the PWM rectifier and the PWM inverter independently, snubber circuits for the PWM rectifier are required to assure the path of load current during dead time. In this paper, analytical method of a snubber circuit and operating characteristics of a snubber circuit are described when a 0.75-kW induction motor is driven by our inverter.

A Zero current Switching Strategy of PWM Rectifier of Converter without DC Link Components for Induction Motor Drives

A converter without DC Link components needs snubber circuits, in order to assure the path of the load current during the dead-time period of the PWM rectifier section. In the snubber circuits, losses have been dissipated every time the switches of the rectifier section are turned on and turned off. During the zero voltage vector period of the inverter section, the load current does not flow in the PWM rectifier section. So if each switching operations of the PWM rectifier section are done in the zero voltage vector period, it is not necessary to assure the path of the load current. Therefore, snubber circuits are not necessary in the PWM rectifier section. In this paper, we describe a zero current switching strategy of the PWM rectifier section during zero voltage vector periods of the inverter section. The proposed strategy is verified by computer simulation and experimental test on an induction motor drive.

Characteristics of New Current Controlled PWM Rectifier-Voltage Source Inverter without DC Link Components for Induction Motor Drive

The voltage-source inverters are normally equipped with an electrolytic capacitor in their DC link. The electrolytic capacitor has several disadvantage such as increasing size, limitting converter life and reliability. Therefore, several approaches for removing the DC link capacitor have been studied. This paper proposes a new strategy of the voltage source inverter without DC link components. To restrain the current resonance caused by LC filter of AC source side, rectifier of this inverter is controlled by current closed loop with di/dt feedback (di/dt; differenciation of AC source current). To improve AC source current waveform, feedback gain of di/dt and LC parameters are investigated by calculation for a 0.75kW induction motor driven by this inverter. Both the calculated and measured waveforms of AC source currents maintain nearly sinusoidal waveforms with a unity power factor.

PWM-rectifier/voltage-source inverter without DC link components for induction motor drive

Voltage-source inverters are normally equipped with an electrolyte capacitor in their DC link. A voltage-source inverter without DC link components is proposed to eliminate the electrolytic capacitor which has a short life compared with an AC capacitor (metalised polyester film, etc.). This inverter system requires an AC filter composed of L and C in the AC source side. In this case, the most important problem is the reduction of AC filter capacity. To achieve this reduction, the rectifier section is operated by PWM control. The waveform of the AC source current is also improved. Steady-state analysis, the calculated characteristics of the AC filter capacity and the waveforms of voltage and current are described for a 0.75 kW induction motor driven by the system. The AC filter capacity is reduced to about 38% of the rectifier without PWM. Measured waveforms are presented for a motor slip of 4%. The stability with, and without, DC link components, is also discussed.

Stability Analysis of Induction Motor Driven by Voltage Source Inverter without DC Link Components.

Stability Analysis of Induction Motor Driven by Voltage Source Inverter without DC Link Components.

SRM inverter topologies: a comparative evaluation

Several inverter power circuits suitable for switched reluctance motor (SRM) drives are analyzed and compared. Five inverter circuits are considered with the objective of establishing the most appropriate topology for an SRM drive. The comparison is based on the peak voltage and peak current ratings of the DC link components. Because the power converter choice depends on the motor design, the converter analysis and selection are done for a high-speed, 6/2 SRM suitable for a spindle drive and a high-torque 8/6 motor. Experimental results obtained for a high-torque drive are included.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Analysis and fundamental characteristics of induction motor driven by voltage‐source type inverter without DC link components

Analysis and fundamental characteristics of induction motor driven by voltage‐source type inverter without DC link components

Analysis and fundamental characteristics of induction motor driven by voltage source inverter without DC link components.

Analysis and fundamental characteristics of induction motor driven by voltage source inverter without DC link components.

An SMR Topology with Suppressed DC Link Components and Predictive Line Current Waveshaping

A new switch-mode rectifier (SMR) topology has been developed and presented in this paper. Its advantages over other SMR topologies include: high input power factor, minimum input current distortion, elimination of dc link bus electrolytic capacitors, and minimization of switching stresses of high-frequency inverter stage components.

Rectifier-Inverter Frequency Changers with Suppressed DC Link Components

Rectifier-inverter types of static frequency changers (SFC's) typically employ bulky dc link reactive components to establish the required dc bus voltage. The negative effects of these components on overall system performance and evolution have been the subject of many past research publications. It is demonstrated that these unwanted components can be eliminated through the use of suitable SFC power circuit topologies. Two such topologies (i.e.,SFC Structures 1 and 2) are investigated here. These converter structures employ state-of-the-art power semiconductor components and optimized rectifier-inverter switching schemes. Finally, theoretical and experimental results show that proposed converter structures offer significant performance improvements at the cost of only moderate power and logic circuit complexity.