11 research outputs found
Multi-harmonic Modeling of Low-power PWM DC-DC Converter
Modeling and simulation of switched-mode Pulse Width Modulated (PWM) DC-DC converters form an essential ingredient in the analysis and design process of integrated circuits. In this research work, we present a novel large-signal modeling technique for low-power PWM DC-DC converters. The proposed model captures not only the time-averaged response within each moving switching cycle but also high-order harmonics of an arbitrary degree, hence modeling both the average component and ripple very accurately. The proposed model retains the inductor current as a state variable and accurately captures the circuit dynamics even in the transient state. By continuously monitoring state variables, our model seamlessly transitions between the continuous conduction mode (CCM) and discontinuous conduction mode (DCM), which often occurs in low-power applications. The nonlinearities of devices are also considered and efficiently evaluated resulting in a significant improvement in model accuracy. With a system decoupling technique, the DC response of the model is decoupled from higher-order harmonics, providing additional simulation speedups. For a number of converter designs, the proposed model obtains up to 10x runtime speedups over transistor-level transient simulation with a maximum output voltage error less than 4%
Stability analysis of switched dc-dc boost converters for integrated circuits
Boost converters are very important circuits for modern devices, especially battery- operated integrated circuits. This type of converter allows for small voltages, such as those provided by a battery, to be converted into larger voltage more suitable for driving integrated circuits. Two regions of operation are explored known as Continuous Conduction Mode and Discontinuous Conduction Mode. Each region is analyzed in terms of DC and small-signal performance. Control issues with each are compared and various error amplifier architectures explored. A method to optimize these amplifier architectures is also explored by means of Genetic Algorithms and Particle Swarm Optimization. Finally, stability measurement techniques for boost converters are explored and compared in order to gauge the viability of each method. The Middlebrook Method for measuring stability and cross-correlation are explored here
Efficient and Robust Simulation, Modeling and Characterization of IC Power Delivery Circuits
As the Moore’s Law continues to drive IC technology, power delivery has become one
of the most difficult design challenges. Two of the major components in power delivery are
DC-DC converters and power distribution networks, both of which are time-consuming to
simulate and characterize using traditional approaches. In this dissertation, we propose a
complete set of solutions to efficiently analyze DC-DC converters and power distribution
networks by finding a perfect balance between efficiency and accuracy.
To tackle the problem, we first present a novel envelope following method based on
a numerically robust time-delayed phase condition to track the envelopes of circuit states
under a varying switching frequency. By adopting three fast simulation techniques, our
proposed method achieves higher speedup without comprising the accuracy of the results.
The robustness and efficiency of the proposed method are demonstrated using several DCDC
converter and oscillator circuits modeled using the industrial standard BSIM4 transistor
models. A significant runtime speedup of up to 30X with respect to the conventional
transient analysis is achieved for several DC-DC converters with strong nonlinear switching
characteristics.
We then take another approach, average modeling, to enhance the efficiency of analyzing
DC-DC converters. We proposed a multi-harmonic model that not only predicts the
DC response but also captures the harmonics of arbitrary degrees. The proposed full-order
model retains the inductor current as a state variable and accurately captures the circuit
dynamics even in the transient state. Furthermore, by continuously monitoring state variables,
our model seamlessly transitions between continuous conduction mode and discontinuous
conduction mode. The proposed model, when tested with a system decoupling
technique, obtains up to 10X runtime speedups over transistor-level simulations with a maximum output voltage error that never exceeds 4%.
Based on the multi-harmonic averaged model, we further developed the small-signal
model that provides a complete characterization of both DC averages and higher-order
harmonic responses. The proposed model captures important high-frequency overshoots
and undershoots of the converter response, which are otherwise unaccounted for by the
existing techniques. In two converter examples, the proposed model corrects the misleading
results of the existing models by providing the truthful characterization of the overall
converter AC response and offers important guidance for converter design and closed-loop
control.
To address the problem of time-consuming simulation of power distribution networks,
we present a partition-based iterative method by integrating block-Jacobi method with
support graph method. The former enjoys the ease of parallelization, however, lacks a
direct control of the numerical properties of the produced partitions. In contrast, the latter
operates on the maximum spanning tree of the circuit graph, which is optimized for
fast numerical convergence, but is bottlenecked by its difficulty of parallelization. In our
proposed method, the circuit partitioning is guided by the maximum spanning tree of the
underlying circuit graph, offering essential guidance for achieving fast convergence. The
resulting block-Jacobi-like preconditioner maximizes the numerical benefit inherited from
support graph theory while lending itself to straightforward parallelization as a partitionbased
method. The experimental results on IBM power grid suite and synthetic power grid
benchmarks show that our proposed method speeds up the DC simulation by up to 11.5X
over a state-of-the-art direct solver
Efficient and Robust Simulation, Modeling and Characterization of IC Power Delivery Circuits
As the Moore’s Law continues to drive IC technology, power delivery has become one
of the most difficult design challenges. Two of the major components in power delivery are
DC-DC converters and power distribution networks, both of which are time-consuming to
simulate and characterize using traditional approaches. In this dissertation, we propose a
complete set of solutions to efficiently analyze DC-DC converters and power distribution
networks by finding a perfect balance between efficiency and accuracy.
To tackle the problem, we first present a novel envelope following method based on
a numerically robust time-delayed phase condition to track the envelopes of circuit states
under a varying switching frequency. By adopting three fast simulation techniques, our
proposed method achieves higher speedup without comprising the accuracy of the results.
The robustness and efficiency of the proposed method are demonstrated using several DCDC
converter and oscillator circuits modeled using the industrial standard BSIM4 transistor
models. A significant runtime speedup of up to 30X with respect to the conventional
transient analysis is achieved for several DC-DC converters with strong nonlinear switching
characteristics.
We then take another approach, average modeling, to enhance the efficiency of analyzing
DC-DC converters. We proposed a multi-harmonic model that not only predicts the
DC response but also captures the harmonics of arbitrary degrees. The proposed full-order
model retains the inductor current as a state variable and accurately captures the circuit
dynamics even in the transient state. Furthermore, by continuously monitoring state variables,
our model seamlessly transitions between continuous conduction mode and discontinuous
conduction mode. The proposed model, when tested with a system decoupling
technique, obtains up to 10X runtime speedups over transistor-level simulations with a maximum output voltage error that never exceeds 4%.
Based on the multi-harmonic averaged model, we further developed the small-signal
model that provides a complete characterization of both DC averages and higher-order
harmonic responses. The proposed model captures important high-frequency overshoots
and undershoots of the converter response, which are otherwise unaccounted for by the
existing techniques. In two converter examples, the proposed model corrects the misleading
results of the existing models by providing the truthful characterization of the overall
converter AC response and offers important guidance for converter design and closed-loop
control.
To address the problem of time-consuming simulation of power distribution networks,
we present a partition-based iterative method by integrating block-Jacobi method with
support graph method. The former enjoys the ease of parallelization, however, lacks a
direct control of the numerical properties of the produced partitions. In contrast, the latter
operates on the maximum spanning tree of the circuit graph, which is optimized for
fast numerical convergence, but is bottlenecked by its difficulty of parallelization. In our
proposed method, the circuit partitioning is guided by the maximum spanning tree of the
underlying circuit graph, offering essential guidance for achieving fast convergence. The
resulting block-Jacobi-like preconditioner maximizes the numerical benefit inherited from
support graph theory while lending itself to straightforward parallelization as a partitionbased
method. The experimental results on IBM power grid suite and synthetic power grid
benchmarks show that our proposed method speeds up the DC simulation by up to 11.5X
over a state-of-the-art direct solver
Design and Control of Power Converters 2020
In this book, nine papers focusing on different fields of power electronics are gathered, all of which are in line with the present trends in research and industry. Given the generality of the Special Issue, the covered topics range from electrothermal models and losses models in semiconductors and magnetics to converters used in high-power applications. In this last case, the papers address specific problems such as the distortion due to zero-current detection or fault investigation using the fast Fourier transform, all being focused on analyzing the topologies of high-power high-density applications, such as the dual active bridge or the H-bridge multilevel inverter. All the papers provide enough insight in the analyzed issues to be used as the starting point of any research. Experimental or simulation results are presented to validate and help with the understanding of the proposed ideas. To summarize, this book will help the reader to solve specific problems in industrial equipment or to increase their knowledge in specific fields
Maximum power point tracking algorithm for photovoltaic home power supply.
Thesis (M.Sc.Eng)-University of KwaZulu-Natal, Durban, 2011.Solar photovoltaic (PV) systems are distributed energy sources that are an environmentally friendly
and renewable source of energy. However, solar PV power fluctuates due to variations in radiation
and temperature levels. Furthermore, when the solar panel is directly connected to the load, the power
that is delivered is not optimal. A maximum peak power point tracker is therefore necessary for
maximum efficiency.
A complete PV system equipped maximum power point tracking (MPPT) system includes a solar
panel, MPPT algorithm, and a DC-DC converter topology. Each subsystem is modeled and simulated
in a Matlab/Simulink environment; then the whole PV system is combined with the battery load to
assess the overall performance when subjected to varying weather conditions.
A PV panel model of moderate complexity based on the Shockley diode equation is used to predict
the electrical characteristics of the cell with regard to changes in the atmospheric parameter of
irradiance and temperature.
In this dissertation, five MPPT algorithms are written in Matlab m-files and investigated via
simulations. The standard Perturb and Observe (PO) algorithm along with its two improved versions
and the conventional Incremental Conductance (IC) algorithm, also with its two-stage improved
version, are assessed under different atmospheric operating conditions. An efficient two-mode MPPT
algorithm combining the incremental conductance and the modified constant voltage methods is
selected from the five ones as the best model, because it provides the highest tracking efficiencies in
both sunny and cloudy weather conditions when compared to other MPPT algorithms.
A DC-DC converter topology and interface study between the panel and the battery load is performed.
This includes the steady state and dynamic analysis of buck and boost converters and allows the
researcher to choose the appropriate chopper for the current PV system. Frequency responses using
the state space averaged model are obtained for both converters. They are displayed with the help of
Bode and root locus methods based on their respective transfer functions. Following the simulated
results displayed in Matlab environment for both choppers, an appropriate converter is selected and
implemented in the present PV system. The chosen chopper is then modeled using the Simulink
Power Systems toolbox and validates the design specifications.
The simulated results of the complete PV system show that the performances of the PV panel using
the improved two-stage MPPT algorithm provides better steady state and fast transient characteristics
when compared with the conventional incremental conductance method. It yields not only a reduction
in convergence time to track the maximum power point MPP, but also a significant reduction in
power fluctuations around the MPP when subjected to slow and rapid solar irradiance changes
Issues in Design of Maximum-Power-Point-Tracking Control – Power Electronics Perspective
This thesis provides a comprehensive study of the dynamic characteristics and operation of maximum-power-point-tracking (MPPT) dc-dc converters, especially for those parts that concern the MPPT-control design. The study concentrates on the widely-utilized heuristic perturb-based MPPT algorithms and their design constraints when equipped with photovoltaic-interfacing converter. The main objective is to provide an explicit formulation of the input-power dynamics of the photovoltaic-generator-interfacing dcdc converter for addressing the MPP-tracking control. The dynamics introduce design constraints for the aforementioned MPPT-control algorithms and provide tools for deterministic MPPT design.A photovoltaic (PV) generator has nonlinear current-voltage characteristics with a particular maximum power point (MPP), which depends on the environmental factors such as temperature and irradiation. Thus, to ensure the maximization of the power extracted from the PV source, the interfacing power converter must be capable of controlling its parameters, i.e., changing its input voltage and current levels based on the MPP of the PV generator. That is done by implementing an MPPT controller, which generates the reference control signal for the interfacing converter. Despite the way of implementation, the fundamental operation is to nd the electrical operating point, i.e., the voltage and the current, at which the PV generator either generates the maximum power or follows a given power reference at every time instant. However, the dynamic characteristics of a photovoltaic generator are determined by the environmental conditions as well as the dynamics of the interfacing converter, which creates limitations for the MPPT-control design. It has been noticed recently that the characteristic curve of a PV generator can be separated into three dierent operation regions each having their distinct characteristics. Thus, to ensure reliability and eciency of a maximum-power tracking, all of these regions should be analyzed separately and choose the condition corresponding to the slowest settling dynamics of the PV system. Up to now, that is not completely recognized, and deterministic analytical models are missing to provide design guidelines for the MPPT-control design.This thesis presents a detailed dynamic model for PV-generator power dynamics in case of open-loop and closed-loop-operated switched-mode dc-dc converter. Two common design examples of closed-loop-operated converters were provided, where the closed-loop dynamics of the converter was slow and fast by adjusting the control bandwidth and phase margin of the feedback loop. With the developed models, a proper evaluation of the MPPT control imposed by the converter dynamics was presented. Thus, previously developed design guidelines were revised, or new guidelines were established
Recommended from our members
Accurate modeling of nonideal low-power PWM DC-DC converters operating in CCM and DCM using enhanced circuit-averaging techniques
18th IEEE Workshop on Nonlinear Dynamics of Electronic Systems: Proceedings
Proceedings of the 18th IEEE Workshop on Nonlinear Dynamics of Electronic Systems, which took place in Dresden, Germany, 26 – 28 May 2010.:Welcome Address ........................ Page I
Table of Contents ........................ Page III
Symposium Committees .............. Page IV
Special Thanks ............................. Page V
Conference program (incl. page numbers of papers)
................... Page VI
Conference papers
Invited talks ................................ Page 1
Regular Papers ........................... Page 14
Wednesday, May 26th, 2010 ......... Page 15
Thursday, May 27th, 2010 .......... Page 110
Friday, May 28th, 2010 ............... Page 210
Author index ............................... Page XII