Common DC Source Research Articles

Enhanced proportional integral controller for DSTATCOM with particle swarm optimization algorithm in power system

Power system expansion planning is supported by using distributed generation (DG) instead of installing new main power system generators. The portability and autonomous operation of the DG make it capable of integrating into the distribution system. Power electronics devices for home loads, mainly electric vehicles, mobile phones, and laptops, introduce harmonics and related power quality issues to the distribution system. This load creates power quality issues like an increase in total harmonic distortion (THD) and a reduction in power factor. This paper uses the DG to supply important power electronics devices for the mitigation of power quality problems in distributed systems with non-linear loads, such as electric vehicles, called the “distributed static compensator (DSTATCOM)”. Wind and photovoltaic (PV) generators supply power to a common DC source. To improve power quality D-STATCOM powered by PV and wind energy systems at the DC link is incorporated. The direct axis/quadrature axis method (DQ method) controls the real and reactive components of the power. Proportional integral (PI) and particle swarm optimization (PSO) based PI controller parameter estimation are developed, and results are compared for power quality performance. In terms of improving power quality, the PSO-based parameter estimate of the PI controller performs better than the traditional PI controller.<br /><div class="extension_reset_css AnnotateNet_widget AnnotateReviewNotesButton" style="display: none; z-index: 2147483644;" data-id="ExtensionWidget"><div class="extension_reset_css AnnotateNet_widget annotateclickable" style="z-index: 8; display: none;" title="Resize" data-id="Widget"> </div></div>

A Five-Level Torque Controller Based DTC Scheme for Open-End Winding Five-Phase IM Drives With Single DC Source and Auxiliary Plane Harmonic Elimination

This article presents a new five-level torque hysteresis based direct torque control scheme for dual inverter fed five-phase induction motor drives with open-end stator windings. Three voltage levels required to implement the five-level torque hysteresis controller are generated by combining the appropriate voltage vectors of the two inverters. The proposed scheme ensures that the harmonic voltages in the nontorque producing auxiliary plane are nullified in every switching period. Since the switching voltage vectors are realized using adjacent and nonadjacent line voltages, the magnitude of the voltage appearing across the windings is much higher compared to the conventional star connected five-phase drive, for the same dc link voltage. This feature reduces the dc link voltage requirement substantially for a given motor voltage. The switching scheme employed prevents circulation of common mode currents even when a common dc source is used for feeding both inverters. The proposed scheme is experimentally verified on a five-phase induction motor drive with open end stator windings. The control scheme is implemented using TMS320F28335 digital signal controller.

Multimodule Boost-Converter-Based Pulse Generators: Design and Operation

In this article, three different types of pulse generators based on multimodule boost converter ringing circuit are presented, namely, interleaved, stacked, and interleaved–stacked with full design and operational concept. The interleaved version is advantageous in generating a burst of pulses with moderate voltage magnitude, where the used modules are fed from a common dc source. On the other hand, the stacked multimodule version can be used to generate high-voltage pulsed output from synchronized modules with a moderate voltage rating. This can be done by feeding the modules from isolated dc sources while connecting their outputs in series. Finally, the interleaved–stacked version can be used for generating a burst of pulses with high-voltage magnitude. The presented pulse generators are valid for resistive loads with exponential decay pulses. The suggested pulse generators are simple and require semiconductor devices with moderate voltage ratings. For given pulse specifications, a detailed design for the passive components of each version is presented in this article. The simulation and experimental results are used to validate the suggested topologies.

A 3D Wireless Charging Cylinder With Stable Rotating Magnetic Field for Multi-Load Application

This paper proposes a 3D wireless charging cylinder with improved compensation topology to generate a stable rotating magnetic field for charging multiple loads around it. The induced voltage of each receiver is kept constant against load variations when the distance between the transmitter and the receiver is fixed. The 3D charging cylinder has a simple configuration with two perpendicular LCL-compensated transmitter coils driven by separate power inverters sharing a common dc source. The system is fully analyzed with the maximum load limit determined, and design guidance is provided. Both theoretical and experimental results demonstrate that the transmitter currents remain constant against load variations when the total load is within the maximum load limit, and the transfer efficiency is increased with the increase of the total reflected impedance. Compared to the conventional series–series (SS) compensated WPT system, the proposed 3D configuration can maintain the transmitter currents to be constant within the maximum load limit so that multiple loads can be added without affecting each other. It has found that the transmitter currents of the proposed configuration are kept constant at their initial values when four loads with the resistance of $0.5~\Omega $ each are randomly placed at 21 cm from the center of the charging cylinder. By contrast, the transmitter currents of the SS compensated WPT system are obviously changed together with the load voltages.

A novel center-tapped transformer based multilevel inverter with common DC source

In this paper, a novel multilevel inverter topology is proposed which uses lesser switches and anti-parallel diodes are eliminated in the circuit configuration of the multilevel inverter. Optimal switching strategy for the inverter using three different Space Vector Pulse Width Modulation (SVPWM) techniques is analyzed based on the power quality indices. The proposed model is simulated and tested using MATLAB/Simulink. Owing to the switching techniques used the harmonic content at the output of the inverter is mitigated which results in a lesser value of total harmonic distortion. Reduced number of power electronic switches results in lesser power loss. The performance of the proposed system is validated with simulation results of conventional multilevel inverters and pulse width modulation control methods. The results for various performance parameters such as efficiency, switching loss, voltage magnitude, and total harmonic distortion are analyzed.

Simultaneous DC Current Balance and Common-Mode Voltage Control With Multilevel Current Source Inverters

The current source converter (CSC) has been popular in high-power medium-voltage applications. To increase the system power capacity and reduce the output harmonics, parallel connection of CSCs with multilevel current output is a practical approach. There are mainly two types of parallel based configurations. The structure with an independent dc link for each paralleled CSC can be regarded as the first configuration, where the dc current flowing into each CSC can be controlled from the rectifier side independently. The second type is constructed with only one current source rectifier (CSR) on the grid side and paralleled current source inverters (CSIs) on the load side, which could potentially reduce the cost and size of the system. However, with a common dc source, the dc current for each CSC should be carefully controlled with proper modulation design. At the same time, the common-mode voltage (CMV), which increases the motor line-to-ground voltage and causes additional stress to the insulation system, should also be suppressed. In this paper, with a focus on the shared dc-link structure, we thoroughly analyze the dc-link current flow and common-mode loop circuit. We propose a multilevel modulation strategy of the parallel CSI system considering the requirement of dc current balancing and CMV reduction to improve the overall system performance. The effectiveness of the proposed method is verified by both simulation and experiment in a transformerless parallel CSC system.

Soft-Switched Interleaved DC/DC Converter as Front-End of Multi-Inverter Structure for Micro Grid Applications

An isolated four channel dc/dc converter with zero voltage switching is proposed as the front-end of multiple inverter structures to integrate renewable and other low voltage energy sources to micro grids. The interleaving technique is adopted to connect each module of proposed converter to a common dc source. This dc source can be a fuel cell stack, PV panels, battery, or any other low voltage dc source. All four channels are interleaved and a phase shift of 90° is provided between the gate signals of each channels, which reduces the input current ripple. The output port of the proposed converter provide four isolated and regulated dc voltages. These isolated dc sources can be connected in series or parallel or series-parallel manner to obtain required dc-link voltage of various inverter structure. Issues like capacitor voltage balancing of diode clamped multilevel inverters can overcome through the proposed converter. By incorporating a coupled inductor for isolation and energy storage along with voltage multiplier circuit, the proposed converter can achieve higher voltage step up with lower turns ratio and lower voltage stress at moderate duty ratio. Hence, mosfets of low voltage rating (low R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> (ON)) can be utilized to reduce conduction loss. A 2 kW prototype of the proposed interleaved dc/dc converter is developed and tested with diode clamped three-level inverter, five-level inverter, and three-phase two-level inverter to verify the design.

A Unipolar/Bipolar High-Voltage Pulse Generator Based on Positive and Negative Buck–Boost DC–DC Converters Operating in Discontinuous Conduction Mode

This paper presents a new high-voltage pulse generator, which is based on positive and negative buck-boost (BB) converters fed from a relatively low voltage dc supply. The proposed generator is able to generate unipolar or bipolar high-voltage pulses via operating the BB converters with series or parallel connected outputs respectively using a common input dc source. The components of each converter are rated at half of the pulsed voltage magnitude in the unipolar mode. The converters in the proposed pulse generator operate in discontinuous conduction mode. This enhances system efficiency, as the circuit only operates when it is desired to generate a pulsed output voltage, otherwise the circuit is switched to idle mode with zero current. Detailed illustration of the proposed approach is presented along with a full design of the system components for given output pulse specifications. Finally, simulation and experimental results are presented to validate the proposed concept.

A Switched Inductor Quasi Z source-H-bridge Multilevel Inverter for Soft starting Control of Induction Motor using Direct Torque and Flux Control

An impedance source multilevel inverter schemes applied for traction and industrial drives application. Because it has unique merits ofharmonics less, transformer less drives control application and also soft start capability of induction drives. This paper proposed a reduced source z source Hbridge multilevel inverter and it is applied for induction motor drive control. In order to improving performance of induction motor performance, the torque and speed control is achieved using Direct Torque and Flux Control (DTFC)via phase voltage and current magnitude control. The proposed control scheme of Direct Torque and Flux Control (DTFC) is calculated through phase voltage and phase current sensing and then stator torque and flux is to be calculated byseparate estimation scheme. In reduced source Z source H-bridge multilevel inverter schemes, z source circuit gives a soft start capability across induction motor drive by controlling power magnitude across DC-Link. Reduced source is achieved using capacitor balancing circuit using a common DC-source. A single carrier and multi-reference of Phase Opposition and Disposition (POD) pulse width modulation topology is uses for proposed reduced source z source Multilevel Inverter for soft start control of induction motor.

Improved Power Decoupling Scheme for a Single-Phase Grid-Connected Differential Inverter With Realistic Mismatch in Storage Capacitances

A single-phase differential inverter consists of two elementary dc–dc converters, sharing a common dc source and a common ac output terminal. The other ac terminals of the two converters are connected to the grid in the case of grid-connected applications. The differential inverter has subsequently been shown to have a differential flow path for power transfer and a common-mode path for shifting the usual second-order power oscillation away from the dc source. This capability is referred to as power decoupling, which when implemented properly, may prolong the lifespan of the dc source. Existing studies related to power decoupling using a differential inverter have however focused on developing control schemes with equal storage capacitances assumed for the two elementary converters. This is unquestionably not realistic since the two capacitances will vary in practice. It is therefore the intention of this paper to quantify ac and dc imperfections experienced by the differential inverter when storage mismatch occurs. A simple improved scheme is then proposed for raising performance of the differential inverter (or the differential rectifier where desired). Simulation and experimental results provided have verified the computation and control scheme developed.

A Space Vector PWM With Common-Mode Voltage Elimination for Open-End Winding Five-Phase Drives With a Single DC Supply

Open-end winding three-phase drive topologies have been extensively investigated in the last two decades. In the majority of cases supply of the inverters at the two sides of the winding is provided from isolated dc sources. Recently, studies related to multiphase open-end winding drives have also been conducted, using isolated dc sources at the two winding sides. This paper investigates for the first time a five-phase open-end winding configuration, which is obtained by connecting a two-level five-phase inverter at each side of the stator winding, with both inverters supplied from a common dc source. In such a configuration it is essential to eliminate the common-mode voltage (CMV) that is inevitably created by usual PWM techniques. Based on the vector space decomposition (VSD), the switching states that create zero CMV are identified and plotted. A space vector pattern with large redundancy of switching states is obtained. Suitable space vectors are then selected to realize the required voltage reference at the machine terminals with zero CMV. The large number of redundant states enables some freedom in the choice of switching states to impress these space vectors. Out of numerous possibilities, two particular switching sequences are chosen for further investigation. Both are implemented in an experimental setup, and the results are presented and discussed.

A single-phase embedded Z-source DC-AC inverter.

In the conventional DC-AC inverter consisting of two DC-DC converters with unipolar output capacitors, the output capacitor voltages of the DC-DC converters must be higher than the DC input voltage. To overcome this weakness, this paper proposes a single-phase DC-AC inverter consisting of two embedded Z-source converters with bipolar output capacitors. The proposed inverter is composed of two embedded Z-source converters with a common DC source and output AC load. Though the output capacitor voltages of the converters are relatively low compared to those of a conventional inverter, an equivalent level of AC output voltages can be obtained. Moreover, by controlling the output capacitor voltages asymmetrically, the AC output voltage of the proposed inverter can be higher than the DC input voltage. To verify the validity of the proposed inverter, experiments were performed with a DC source voltage of 38 V. By controlling the output capacitor voltages of the converters symmetrically or asymmetrically, the proposed inverter can produce sinusoidal AC output voltages. The experiments show that efficiencies of up to 95% and 97% can be achieved with the proposed inverter using symmetric and asymmetric control, respectively.

Comparison between 7-Level Cascaded and 7-Level Diode-Clamped Multilevel Inverters for Feeding Induction Motor

In this study, two types of multilevel convertors, cascaded multilevel inverter with separate DC sources and diode clamped multilevel inverter with common DC source are modeled and compared in the case of feeding of an induction motor. Here, SHEPWM technique is used as the switching strategy. Also a new variable torque feedback control on modulation index is presented, to preserve the induction motor in stable condition. Furthermore, the merits and demerits of each convertor from power quality point of view are compared. Outputs of simulations shows that despite of that feeding of loads using diode clamped multilevel convertors with common dc source is easier than cascaded converters from feeding inverters with DC sources point of view, even thought cascaded multilevel inverters has more robust performance in case of feeding variable torque induction motor loads. And our feedback controller works to improve outputs of multilevel inverter and parameters of induction motor in both cases.

비대칭 전압 제어를 이용한 단상 임베디드 Z-소스 DC-AC 인버터

In case of the conventional DC-AC inverter using two DC-DC converters with unipolar output capacitor voltages, for generating the AC output voltage, the output capacitor voltages of its each DC-DC converter must be higher than the DC input voltage. To solve this problem, this paper proposes a single-phase DC-AC inverter using two embedded Z-source converters with bipolar output capacitor voltages. The proposed inverter is composed of two embedded Z-source converters with common DC source and output AC load. The AC output voltage is obtained by the difference of the output capacitor voltages of each converter. Though the output capacitor voltage of converter is relatively low compared to the conventional method, it can be obtained the same AC output voltage. Moreover, by controlling asymmetrically the output capacitor voltage, the AC output voltage of the proposed system is higher than the DC input voltage. To verify the validity of the proposed system, a DSP(TMS320F28335) based single-phase embedded Z-source DC-AC inverter was made and the PSIM simulation was performed under the condition of the DC source 38V. As controlled symmetrically and asymmetrically the output capacitor voltages of each converter, the proposed inverter could produce the AC output voltage with sinusoidal waveform. Particularly, in case of asymmetric control, a higher AC output voltage was obtained. Finally, the efficiency of the proposed system was measured as 95% and 97% respectively in case of symmetric and asymmetric control.

2대의 임베디드 Z-소스 컨버터를 이용한 단상 DC-AC 인버터

In this paper, a single-phase DC-AC inverter using two embedded Z-source converters is proposed. The proposed inverter is composed of two embedded Z-source converters with common DC source and output AC load. The output AC voltage of the inverter is obtained by the difference of output capacitor voltages of each converter. The output voltage of each converter take shape of the asymmetrical AC waveform centering zero voltage. Therefore, the proposed inverter can generate the same output voltage despite low VA rating L-C elements , compared to the conventional inverter using high DC voltage with AC ripple. To verify the validity of the proposed system, the PSIM simulation was achieved under the condition of rapid increase of DC source (110[V]→150[V]) and R-load (50[Ω]→300[Ω]). For controlling the voltage of the inverter system, the one-cycle controller was adopted. As results, the proposed inverter output the constant AC voltage (220[V]rms/60[㎐]) for all conditions. Also, the R-L load and nonlinear diode load were adopted for the proposed inverter loads, and we could know that the its output voltage characteristics were as good as the pure R-load. Finally, the RMS and THD of output AC voltage were examined for the different loads, input DC voltages and reference voltage signals.

Circulating zero-sequence current control of parallel three-phase inverters

A novel circulating zero-sequence current-control method for common DC-source parallel inverter systems is proposed and implemented in FPGA. The follower inverter can closely track the three-phase discontinuous PWM modulation waveforms of the master inverter and the circulating current caused by asynchronous modulation waveforms can be reduced. The controller is implemented in FPGA, and the requirement of high-speed control and measurement can be satisfied without any extra burden added to the processor of the drive system. The theoretical analysis of the experimental results verifies the performance of the proposed circulating-current-control method.

Polyphase multivibrators

A new type of polyphase multivibrator is introduced in which saturable cores are the timing elements and transistors the switching elements. The basic units are like the multivibrators invented by Royer and others, but, in the new polyphase circuit, several single-phase multivibrators with a common dc source are constrained by a loop connection of windings on the cores in such a way that polyphase output voltages are obtained. Detailed analysis of a typical 3-phase circuit leads to conclusions regarding the frequency of oscillation and the output voltage waveforms which conform to experimental observations. Novel arrangements are presented by means of which 2-phase voltages can be obtained from a 3-phase multivibrator.