Ideal DC Research Articles

An Ideal DC Transformer for Active DC Distribution Networks Based on Constant-Transformation-Ratio DABC

This paper employs a single-phase-shift modulated dual-active-bridge converter (DABC), and establishes a small-signal model, which involves its voltage transformation ratio. Then, through a voltage transformation ratio feedback loop, which is feedforward compensated by the port voltages and currents, closed-loop control of the transformation ratio of the DABC is realized. The proposed controller can make the DABC operate in constant transformation ratio mode, and act as an ideal dc transformer in an active dc distribution network. Based on the bidirectional voltage support capability of the proposed dc transformer, the different buses of an active dc distribution network can mutually provide voltage support for each other. Besides, the proposed dc transformer can realize the normalized decentralized power coordination between the energy storage systems at different buses of the active dc distribution network. The feasibility of the proposed dc transformer is verified by several hardware-in-loop tests.

Analysis of armature inter‐turn fault in the multiphase synchronous generator‐rectifier system

The multiphase synchronous generator-rectifier system could provide an ideal DC power source for more electric aircraft (MEA). When the inter-turn short-circuit fault occurs in phase windings of the generator, a large short-circuit current would be introduced inside the armature windings, which could cause severe damages to the system for overheat in the windings and irons as well as huge electromagnetic forces on the end coils. To improve the reliability of the MEA, this study researches on the inter-turn fault of the multiphase generator-rectifier system including the theoretical analysis, numerical simulation and experiment verification. A 12-phase system is taken, for example, and a multi-loop mathematical model is built up to calculate all voltages and currents in the multiphase synchronous generator-rectifier system with armature inter-turn fault. Many factors are thoroughly considered in the model including the location and short turns of fault, space harmonics of the air-gap magnetic field and the changing circuit topology of the system. Moreover, the mathematical model is verified by fault experiment results. Moreover, the electric characteristics of the fault are summarised, which could provide a quantitative basis for early detection of the inter-turn faults in the multiphase generator-rectifier system.

ANN-based Maximum Power Point Tracking for a Large Photovoltaic Farm Through Wireless Sensor Networks

Background: A novel system for the usage of Maximum Power Point Tracking of an expansive Solar Photo Voltaic (SPV) farm subjected to conceivable incomplete shading is displayed in this paper. The SPV farm being spread over an expansive territory a remote sensor organize is utilized for checking the sun based protection in the region of each board. The motivation behind the remote sensor organize is to screen the sunlight based protection at various areas near each of the PV board from the tremendous region of the photograph voltaic homestead comprising of countless voltaic boards. The observed protection information is utilized by a prepared. Artificial Neural Network to locate the ideal DC terminal voltage to be kept up over the general DC terminals of the photograph voltaic ranch. All the PV boards are associated in arrangement association with the fundamental bye pass diodes. The DC control accessible at the yield terminals of the SPV cultivate is first DC to DC changed over with a Positive Output Luo Converter (POLC) and bolstered to a heap. A MATLAB Simulink based reproduction was created to approve the proposed system. Methods: Maximum Power Point Tracking based on Artificial Neural Network through wireless sensor networks. Results: As the result of the proposed idea and its implementation in MATLAB we have two sets of results. In either case the input is a vector of 40 elements and the output of the first segment of the work is the estimation of the threshold PV terminal voltage that will guarantees maximum power point operation. In the first case we have the MATLAB SIMULINK implementation of the basic configuration of the forty PV panels arranged in series connection and we have provided a facility to edit the solar insulation levels pertaining to the individual PV panels. In this first configuration we have set a continuously variable PV current for all the panels and the PV current for all the panel are the same. Using this setup, for any combination of solar insulation pattern of the forty panels the overall PV curve and the overall VI curve can be drawn in MATLAB. As the simulation runs the PV current is changed from 0 to the maximum or the short circuit current level in a slowly rising manner implemented using a ramp signal. </P><P> During this period the total power output and the terminal voltage of the PV farm are sent to the work space and the data is thus collected in the workspace of MATLAB. Using basic MATLAB commands the maximum power output and the PV terminal voltage corresponding to the maximum power output are obtained. The PV current at maximum power output condition, the corresponding PV farm terminal voltage, the maximum power output recorded at this condition all correspond to the present insulation vector condition. This way, by changing the elements of the insulation for all the forty panels in a random manner we obtain for each case the Ipmax[i], Pmax[i], Vpmax[i] and this corresponds to insulation[n,i]. Where n is the number of panels, in this case 40 and i the ith experiment. In each experiment the solar insulation level of all the forty panels can be changed and the parameters Vpmax[i], Ipmax[i] and Pmax[i] can be obtained. The value of the harvested power as found from the characteristics for any given set of insulation is denoted as the estimated power. The value of power as obtained from the proposed ANN SMC POLC combination is denoted as the Actual Power. Conclusion: A wireless network based insulation monitoring has been done. An ANN based MPPT algorithm has been developed that gives the reference MPP voltage. The sliding mode control scheme uses the reference voltage and produces the switching pulses for the POLC. The ANN had been trained with a number of combinations of different insulation values falling on each of the forty panels and the ANN gives the correct reference voltage for any combination of insulation levels that were not used while training. The sliding mode controller uses this reference voltage and gives the switching pulses to the POLC that harvests the maximum power output to the RL load. The proposed system has been implemented in the MATLAB SIMULINK environment and has thus been validated. The obtained results have been compared against the maximum power output values that could be derived from the characteristic curves obtained for the given combination of insulation levels. The proposed system gives results very close to the values obtained from the characteristics. As a future work the proposed idea can be validated using hardware based experimental setup.

Battery Energy Storage System Models for Microgrid Stability Analysis and Dynamic Simulation

With the increasing importance of battery energy storage systems (BESS) in microgrids, accurate modeling plays a key role in understanding their behavior. This paper investigates and compares the performance of BESS models with different depths of detail. Specifically, several models are examined: an average model represented by voltage sources; an ideal dc source behind a voltage source converter; a back-to-back buck/boost and bidirectional three-phase converter, with all models sharing the same control system and parameters; and two additional proposed models where the switches are replaced by dependent sources to help analyze the differences observed in the performance of the models. All these models are developed in PSCAD and their performances are simulated and compared considering various issues such as voltage and frequency stability and total harmonic distortion in a benchmark test microgrid. It is shown through simulation results and eigenvalue studies that the proposed models can exhibit a different performance, especially when the system is heavily loaded, highlighting the need for more accurate modeling under certain microgrid conditions.

Research on inter‐turn short circuit of armature windings in the multiphase synchronous generator–rectifier system

The multiphase synchronous generator–rectifier system could provide an ideal DC power source for more electric aircraft (MEA). When the inter-turn short-circuit fault occurs in phase windings of the generator, a large short-circuit current would be introduced inside the armature windings, which could cause severe damages to the system for overheat in the windings and irons as well as huge electromagnetic forces on the end coils. To improve the reliability of the MEA, this study researches on the inter-turn fault of the multiphase generator–rectifier system, including the theoretical analysis, numerical simulation and experimental verification. A 12-phase system is taken for example, and a multi-loop mathematical model is built up to calculate all voltages and currents in the multiphase synchronous generator–rectifier system with armature inter-turn fault. Many factors are thoroughly considered in the model, including the location and short-turns of fault, space harmonics of air-gap magnetic field and the changing circuit topology of the system. The mathematical model is verified by fault experiment results. Moreover, the electric characteristics of the fault are summarised, which could provide a quantitative basis for early detection of the inter-turn faults in the multiphase generator–rectifier system.

Efficiency and Stability in Electrical Power Transmission Networks: a Partition Function Form Approach

The users of electricity networks are organized into groups where the production and consumption of electricity is in balance. We study the formation of these balancing groups using a cooperative game in partition function form defined over an ideal (lossless) DC load flow model of the power grid. We show that such games contain widespread externalities that can be both negative and positive. We study the stability of certain partitions using the concept of the recursive core. While the game is clearly cohesive, we demonstrate that it is not necessarily superadditive. We argue that subadditivity may be a barrier to achieve full cooperation.

Magnetising inductance of multiple‐output flyback dc–dc convertor for discontinuous‐conduction mode

This study presents the following: (i) detailed derivation of the expressions for the maximum value of the magnetising inductance of the ideal and lossy two-output flyback dc–dc convertor operating in discontinuous-conduction mode, (ii) a method to appropriately select the duty cycle for the metal–oxide–semiconductor field-effect transistor based on the rated output dc voltages of the two stages, and (iii) a design approach for a three-winding transformer with a gapped core used in the two-output flyback convertor. The expressions derived and the proposed design technique can be extended to flyback convertors with more than two output stages with equal or unequal load voltages. A universal power supply (ac line adapter) employing a flyback dc–dc convertor with output voltages 15 and 32 V, supplying a rated output current of 0.563 and 0.533 A, and operating at a switching frequency of 85 kHz is designed using the proposed methodology. Simulation and experimental results are presented to validate the theoretical predictions.

Elimination of torque dips due to back EMF non-ideality in brushless AC motors with surface-mounted magnets

Permanent magnet synchronous motor may have back electromotive forces with flattened peaks, hence its torque undergoes considerable dips with pure sinusoidal excitation. The approach used for eliminating torque dips in brushless DC motor by the author in a previous paper is extended here to brushless AC motor. Establishing a normalised current reference to eliminate the dips is a centre piece in this approach. Some light is shed on what is called a brushless motor continuum. At the low end of this continuum, there exists the ideal brushless DC motor and at the high end there exists the ideal brushless AC motor. Despite being hypothetical, the brushless motor continuum brings some interesting insights into how these machines are differentiated when they are ideal and how they converge as they lose ideality. A unified approach for fixing the consequences of non-ideality seems worthy in light of the severe difficulty of building a perfect brushless motor.

RTDS-Based Modeling and Simulation for Control System of HVDC

To analyze response of control system for HVDC during steady-state operation and transient process accurately, an electromagnetic transient model of the actual control system is built based on the platform of RTDS. The rectifier side applies constant current regulator of variable gain, and pole power control/voltage dependent current order limiter. Under the condition of considering no-load DC voltage and nonlinear control design for firing angle, the combination of current regulator and alphamax inverter control is designed. At the same time, transformer tap control on both sides is constructed to match with control of firing angle, including some functions of regulating ideal no-load DC voltage, DC voltage and firing angle. By the analysis of various running conditions and dynamic process, the results show that the model can simulate the characteristics of Ud-Id for HVDC system.

Optimal Design of High Frequency Transformer for 150W Class Module-Integrated Converter

Recently, the module-integrated converter has shown an interest in the photovoltaic generation system. In this system, the high frequency transformer should be compact and efficient. The proposed method is based on the correlation characteristic between the copper and core loss to minimize the loss of transformer. By sizing an effective cross-sectional area and window area of core, the amount of loss is minimized. This paper presents the design and analysis of high frequency transformer by using the 3D finite element model coupled with DC-DC converter circuit for more accurate analysis by considering the nonlinear voltage and current waveforms in converter circuit. The current waveform in each winding is realized by using the ideal DC voltage source and switching component. And, the thermal analysis is performed to satisfy the electrical and thermal design criteria.

Assessment and performance evaluation of DC-side interactions of voltage-source inverters interfacing renewable energy systems

Abstract This paper presents a performance characterization and efficient modeling of the dc-side interactions between renewable dc resources and interfacing voltage-source inverters (VSIs). The VSI is considered in both grid-connected and islanded modes of operation. On the other side, the dc source is modeled by an equivalent and a detailed circuit. In the former, an ideal current-source in parallel to a dc capacitor is used to represent a non-dispatchable source whereas an ideal dc voltage source is used to represent a dispatchable dc source. In the latter, an additional dc/dc boost converter interfaces the dc source to regulate the input dc-link voltage of the VSI. In all topologies, computationally-efficient small-signal admittance-based models, i.e. transfer-functions, are thoroughly developed for the dc source as well as the VSI. Using the Nyquist stability criterion, it is shown that the dc-link voltage dynamics is negatively affected under some operating conditions. The worst performance is yielded when the dc source is modeled by an ideal voltage source where the dc-link voltage is not controlled by the VSI. On the contrary, the dc/dc boost converter enhances the system damping. The dc-link voltage-controlling VSIs show the most damped performance. In order to enhance the system damping, active stabilizing compensators are proposed and embedded in the conventional control structure of VSIs. Large-signal time-domain simulation model is implemented under Matlab/Simulink environment to validate the small-signal models and show the effectiveness of the proposed compensators.

Efficiency and Stability in Electrical Power Transmission Networks: A Partition Function Form Approach

The users of electricity networks are organized into groups where the production and consumption of electricity is in balance. This paper studies the formation of these balancing groups using a cooperative game in partition function form defined over an ideal (lossless) DC load flow model of the power grid. The study shows that such games contain widespread externalities that can be both negative and positive. The paper studies the stability of certain partitions using the concept of the recursive core. While the game is clearly cohesive, we demonstrate that it is not necessarily super-additive. We argue that sub-additivity may be a barrier to achieve full cooperation.

Modeling of the Power Factor Correction of 8/6 Poles Switched Reluctance Motors

In the traditional power topology structure of switched reluctance motor (SRM), the ideal DC bus voltage is supplied by the circuit which is composed by a rectifier bridge and a filter capacitor. The capacitor is usually large to reduce the torque ripple, so the conducting time of AC source is very short and the power factor is reductive. A novel power topology structure of SRM is presented in this paper, and it is applied to the traditional split-phase structure to carry out power factor correction (PFC). This paper sets up the two-phase simultaneous excitation of four phases 8/6 poles SRD based on MATLAB/SIMULINK, and analyzes the current, voltage, torque etc. of two-phase excitation. The simulation results proves that the novel topology is not only improving the power factor but also optimizing the motor starting performance and efficiency, and it provides a feasible way for the study of energy conservation and efficient SRM.

Design and Evaluation of Solar Inverter for Different Power Factor Loads

This paper analyzes and compares the performance of a new inverter topology with two types of input sources: 1) Solar PV source and 2) Ideal dc source (battery). The simulation is done in SIMULINK/MATLAB Software. It is shown that when the solar panel is connected, spikes are obtained in output voltage waveforms. These spikes are eliminated by inserting a capacitor. The capacitor is chosen for a particular power factor which is optimum with respect to cost, size and power quality. Total Harmonic Distortion, Active Power, Reactive Power, RMS Voltage and RMS Current are measured for different load power factor. Finally these results are compared with those obtained using battery with same input voltage magnitude. This Paper shows that for Solar Panel Circuit, THD, P and Q are less for 0.8 and above power factor, however below 0.8 PF, the THD, active and reactive power transfer are more. This means that the performance of Solar Panel in the proposed circuit topology is seen to be better as compared to the same circuit with battery within a range of power factor.

CMOS Integration Using Low Thermal Budget Dopant-Segregated Metallic S/D Junctions on Thin-Body SOI

As segregated PtSi contacts using implant-through-silicide technique have been studied. A thermal activation at 600°C gives a As pile-up at the PtSi/Si interface of 4x1020 cm-3 resulting in a Schottky barrier to electrons below 0.1 eV. As and B segregated PtSi contacts have been integrated in a low temperature CMOS process and functional 90 nm inverters have been demonstrated. Inverters with nearly ideal DC voltage transfer characteristics and large voltage gains have been obtained down to 0.5V of supply voltage with excellent noise margins (~VDD/2). This approach provides a low temperature S/D module suitable for a viable and low-cost manufacturing approach for future CMOS technology nodes.

Cogging Torque of Brushless DC Motors Due to the Interaction Between the Uneven Magnetization of a Permanent Magnet and Teeth Curvature

This research investigates the characteristics of cogging torque in brushless DC motors due to the interaction between the uneven magnetization of a permanent magnet and the shape of the teeth. The excitation frequencies of the cogging torque are the harmonics of the least common multiple of the poles and slots in ideal brushless DC motors. However, this research numerically and experimentally illustrates that the uneven magnetization of a permanent magnet also generates the harmonics of slot number. Magnitudes of cogging torque are affected not only by the uneven magnetization of a permanent magnet but also by the shape of the teeth. The cogging torque can be effectively reduced by determining optimal teeth curvature once the range of uneven magnetization of permanent magnet in a brushless DC motor is identified.

Design, modelling, control and simulation of a three-phase DC–DC converter for high currents applications

In this study, a two-stage DC-DC converter for high current applications is studied. The converter consists of two three-phase full-bridge inverters connected through three AC coupled inductors. A switching-functions-based model of the converter is first established, and then a control scheme is designed for both inverters in order to ensure a high power factor at the AC stage, and a regulated voltage at the DC load. The performance of the proposed control system is verified through numerical simulations. First, an ideal DC source is considered in order to test the performance of the control system, then a proton exchange membrane fuel cell is applied as the DC source in order to highlight the usefulness of this converter in such applications.

Advanced Interchangeable Dynamic Simulation Model for the Optimal Design of a Fuel Cell Power Conditioning System

This paper presents an advanced dynamic simulation model of a proton exchange membrane fuel cell for the optimal design of a fuel cell power conditioning system (FC-PCS). For the development of fuel cell models, the dynamic characteristics of the fuel cell are considered, including its static characteristics. Then, software fuel cell simulation is realized using Matlab-Simulink. Specifically, the design consideration of PCS (i.e., power semiconductor switch, capacitor, and inductor) is discussed by comparatively analyzing the developed simulator and ideal DC source. In addition, a cosimulation between the fuel cell model and PCS realized using the PSIM software is performed with the help of the SimCoupler module. Detailed analysis and informative simulation results are provided for the optimal design of fuel cell PCS.

Exploration of Bifurcation and Chaos in Buck Converter Supplied From a Rectifier

The bifurcation phenomena in a current-mode controlled buck converter has been explored when the input of the converter is a rectifier having ripple in the output voltage instead of a regulated ideal dc power supply. A comparison between the two different input conditions shows a wide variation in most of the cases and it is difficult to predict the converter dynamics observing bifurcation diagram only. The mathematical model is developed in continuous conduction mode as well as in discontinuous conduction mode. The switching delay has been considered as its effect has great influence on bifurcation phenomena specially at higher switching frequency of the converter. The observed bifurcation phenomena have been verified experimentally.

Analysis of a PM DC motor model for application in feedback design for electric-powered mobility vehicles

Accurate modelling of Permanent Magnet (PM) DC motors is a prerequisite for expedient feedback design of electric-powered mobility vehicles. This paper identifies the parameters in the ideal equations for PM DC motors and considers the methods used to measure and calculate them accurately. However, the ideal PM DC motor equations' outcomes are rarely accurate compared with the actual results and measurements. The model inaccuracy arising from the existing theoretical model, which is often used in literature and by researchers, has been observed. The work discusses the method to increase the model accuracy, and analyse the model for the application in feedback design for a target vehicle. Tests have been conducted on the actual motors with a real-time data acquisition instrument. Results have been obtained and analysed to validate the improved PM DC motor model.