34,637 research outputs found
A New Dual- Input Hybrid Buck DC-DC Converter
No full textThe proposed dual input hybrid buck C/hybrid buck L (HBCL) DC-DC converter, is suitable for power conversion in renewable energy, automotive and telecom power systems. It extends the use of the hybrid DC-DC converters in a dual-input structure, with high voltage-conversion ratio. Operation modes, analytical description, digital simulations and test results, in good correspondence, are presented and discussed in this paper
EMT simulation of an MTDC system integrating Modular Multilevel DC/DC converter with DC voltage control
No full textThe increasing demand to utilize renewable energy necessitates the transmission of power over long distances. HVDC technology has emerged as the optimal solution for this purpose due to fewer losses and good economic factors. Multi-terminal DC (MTDC) systems are being more focused nowadays, as they offer more advantages over Point to Point (P2P) HVDC scheme because the MTDC network adds more reliability and flexibility to the system. DC/DC converters are emerging as an important device for future MTDC transmission systems. They are required to interconnect HVDC links with different system characteristics such as different DC voltage levels, grounding schemes, and technologies. In addition to this, DC/DC converters are capable of providing additional features in the system like grid protection, DC voltage control, and power flow control. The majority of studies in the literature on DC/DC converters are predominantly focused on the context of either exploring different DC/DC converter topologies or their control and operation in constant power mode for interconnecting HVDC links, suitable for future MTDC grids.
This paper presents an MTDC test case integrating a DC/DC converter where the converter is working with a DC voltage controller and participating in the DC voltage management system. The influence of voltage-controlled DC/DC converter is studied by introducing power disturbances in the MTDC system. The system is modeled and simulated in EMTP software. The droop control technique known for the VSC converter for DC voltage control is extended to obtain a dual droop controller which is used with a DC/DC converter for controlling both DC grid voltages simultaneously. However, this control approach involves designing two droop coefficients for their respective DC grids, complicating the examination of their interaction. Another possibility is to use a new technique called “virtual resistance DC voltage control” which requires tuning only one parameter. The objective is to control DC grid voltages and establish a link between the interconnected networks. The control approach is validated through electromagnetic transient (EMT) simulations. Through the virtual resistance DC voltage control, the interconnected DC grids can share the power disturbance in the system and maintain the DC voltages under their specified limits. This makes the MTDC system more reliable and reduces the stress on the DC voltage management system. Modular multilevel converter (MMC) based topologies are used for DC/DC converters, namely F2F-MMC (front-to-front MMC) which can provide galvanic isolation between the two links and MMC-DC (M2DC) which does not provide galvanic isolation. A comparison analysis has also been made to compare their behavior with a virtual resistance controller. All converters are modeled using reduced order modeling methodology and the DC cables are modeled with wideband models.
The observations in this paper indicate that by employing the virtual resistance DC voltage controller, a connection has been established between interconnected networks, enabling HVDC links to actively participate in and share the power disturbances within the MTDC system. Apart from this, the virtual resistance control behavior remains consistent regardless of the topology of the DC/DC converter, thus demonstrating its robustness as a DC voltage controller
A novel digital PID controlled dc-dc converter
No full textThis paper presents the relationship between the dynamic characteristics and sampling frequency of digitally controlled dc-dc converter with a novel control method. In the proposed method, the calculation process of P and I-D controls is parallel. The sampling interval and points for I-D control are same to the conventional method. However, the sampling point for P control is quickly. The A-D converter can sample the output voltage during the short interval because the calculation process of P control is very simple and to important for transient response. The only sample data near the turn-off timing of PWM pulse is used. The simulation and experiment results of the output voltage against the step change of the load and changing the P control sampling frequency are discussed. As a result, it is revealed experimentally that the good transient response is obtained.2010 International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM 2010) : Pisa, Italy, 2010.06.14-2010.06.1
Common Mode Currents in DC Power Routers
No full textThe grid reinforcement and energy redirection needs have led to the emergence of Back-To-Back Voltage Source Converter (BTB-VSC) based dc power routers. This paper investigates the low frequency Common Mode Currents (CMCs) that arise in the system if the employed BTB-VSCs have an un-isolated ac path connected in parallel to their output ports. Simulation results are presented to show a sensitivity analysis of lower order harmonics in CMC with respect to the operating active and reactive power of the dc router, dc link voltage, link resistance, modulation method and pole capacitance. Experimental results are shared to show existance of lower order CMC in 3-wire ac link operating in parallel with the dc power router and these are mitigated using zero sequence controller
Modeling, Control, and Operation of an M-DAB DC-DC Converter for Interconnection of HVDC Grids
No full textFuture high-voltage direct-current (HVDC) networks based on voltage source converters (VSCs) will have different structures (asymmetric monopolar, bipolar, or symmetric monopolar), voltage levels, control, and protection schemes. Therefore, dc-dc converters are needed to interconnect those VSC-HVDC grids and several technical issues on their control and operational systems must be adequately addressed. A dc-dc converter based on a modular-dual active bridge (M-DAB) converter is suggested to reach a desirable interconnection of the HVDC grids and regulate power flow (PF) between them. A dynamic averaged model is proposed for the M-DAB converter and its stability is analyzed using the Lyapunov function. Moreover, a new local controller based on nonlinear control theory is proposed for the M-DAB. The new M-DAB local controller is integrated with the energy management system (EMS), by updating the PF equations, to create a complete control structure. Considering the CIGRE DCS3 HVDC test system and the studied M-DAB, static, dynamic simulation, and experimental studies are conducted and the dc-dc converter and the performance of the designed controllers and the EMS are examined and validated.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Intelligent Electrical Power Grid
Restructuring the existing medium voltage distribution grids using DC systems
No full textGreen Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.DC systems, Energy conversion & Storag
Cold cracking in DC-cast high strength aluminum alloy ingots: An intrinsic problem intensified by casting process parameters
No full textFor almost half a century the catastrophic failure of direct chill (DC) cast high strength aluminum alloys has been challenging the production of sound ingots. To overcome this problem, a criterion is required that can assist the researchers in predicting the critical conditions which facilitate the catastrophic failure of the ingots. This could be achieved at first glance by application of computer simulations to assess the level and distribution of residual thermal stresses. However, the simulation results are only able to show the critical locations and conditions where and when high stresses may appear in the ingots. The prediction of critical void/crack size requires simultaneous application of fracture mechanics. In this paper, we present the thermo-mechanical simulation results that indicate the critical crack size distribution in several DC-cast billets cast at various casting conditions. The simulation results were validated upon experimental DC-casting trials and revealed that the existence of voids/cracks with a considerable size is required for cold cracking to occur.Materials Science & EngineeringMechanical, Maritime and Materials Engineerin
Control of DC Motors
No full textA DC motor is an electrical motor that uses direct current to produce mechanical torque. Control of DC motors (i.e., control of shaft speed or position) is relatively easy. This makes the DC motors a good choice for many applications. This chapter shows how speed and direction of rotation of a permanent magnet brushed DC motor can be controlled. © 2024, The Author(s), under exclusive license to Springer Nature Switzerland AG
A Dynamically Reconfigurable Recursive Switched-Capacitor DC-DC Converter with Adaptive Load Ability Enhancement
No full textMultiple voltage conversion ratio (VCR) recursive switched-capacitor (SC) dc-dc converters, based on several basic 2:1 converters, are widely used for on-chip power supplies due to their flexible VCRs for higher energy efficiency. However, conventional multiple VCR SC converters usually have one or more 2:1 converters unused for some VCRs, which results in lower power density and chip area wastage. This article presents a new recursive dc-dc converter system, which can dynamically reconfigure the connection of all on-chip 2:1 converter cells so that the unused converters in the conventional designs can be reused in this new architecture for increasing the load-driving capacity, power density, and power efficiency. To validate the design, a 4-bit-input 15-ratio system was designed and fabricated in a 180-nm BCD process, which can support a maximum load current of \text{0.71}\,\text{mA} and achieves a peak power efficiency of 93.1% with 105.3\,\mu \text{A/mm} {2} chip power density from a 2-V input power supply. The measurement results show that the load-driving capacity can become 6.826×, 2.236×, and 2.175× larger than the conventional topology when the VCR is 1/2, 1/4, and 3/4, respectively. In addition, the power efficiency under these specific VCRs can also be improved considerably.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Instrumentatio
Design Automation for High-Efficiency Stacked Integrated DC-DC Converters
No full textembargoed_20280911The stacking of low voltage transistors brings several advantages for the
design of power management integrated circuits (PMICs). Process nodes
and, thereby, the I/O voltage of the core devices shrink down, while the
supply voltages of many applications cannot be reduced at the same rate.
The stacking of low-voltage devices is often more area- and energy-efficient
compared with using one high voltage transistor. Up to now, on the literature
is not present a unified model which describes the behavior of two stacked
transistors during the turn-on and turn-off transients, and able to estimate
the switching losses. Consequently, when it comes the time for an electronic
engineer to design a DC-DC converter with stacked topology, is always though
to find a good point of start in terms of devices parameters.
This leads to the idea at the base of this work: to develop a model able
to give an estimation of the total efficiency for a two-stacked buck converter
in function of many parameters, like transistors channel ́s length and width,
switching frequency, output current, supply voltage, and so on. The buck
model has been implemented through python code and uses interpolated
data from look-up tables (LUT), provided by the company and related to the
case-of-study technology. In order to validate the model, a statistical analysis
has been carried out, comparing model results with several different input
sets, with the results of simulations in a SPICE based environment. In the
future the model can be expanded including new input parameters, like the
bulk connection of the cascaded transistors.The stacking of low voltage transistors brings several advantages for the
design of power management integrated circuits (PMICs). Process nodes
and, thereby, the I/O voltage of the core devices shrink down, while the
supply voltages of many applications cannot be reduced at the same rate.
The stacking of low-voltage devices is often more area- and energy-efficient
compared with using one high voltage transistor. Up to now, on the literature
is not present a unified model which describes the behavior of two stacked
transistors during the turn-on and turn-off transients, and able to estimate
the switching losses. Consequently, when it comes the time for an electronic
engineer to design a DC-DC converter with stacked topology, is always though
to find a good point of start in terms of devices parameters.
This leads to the idea at the base of this work: to develop a model able
to give an estimation of the total efficiency for a two-stacked buck converter
in function of many parameters, like transistors channel ́s length and width,
switching frequency, output current, supply voltage, and so on. The buck
model has been implemented through python code and uses interpolated
data from look-up tables (LUT), provided by the company and related to the
case-of-study technology. In order to validate the model, a statistical analysis
has been carried out, comparing model results with several different input
sets, with the results of simulations in a SPICE based environment. In the
future the model can be expanded including new input parameters, like the
bulk connection of the cascaded transistors
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