Modeling And Simulation Of Microgrid, 2018 Missouri University of Science and Technology

#### Modeling And Simulation Of Microgrid, Ahmad Alzahrani, Mehdi Ferdowsi, Pourya Shamsi, Cihan H. Dagli

*Pourya Shamsi*

Complex computer systems and electric power grids share many properties of how they behave and how they are structured. A microgrid is a smaller electric grid that contains several homes, energy storage units, and distributed generators. The main idea behind microgrids is the ability to work even if the main grid is not supplying power. That is, the energy storage unit and distributed generation will supply power in that case, and if there is excess in power production from renewable energy sources, it will go to the energy storage unit. Therefore, the electric grid becomes decentralized in terms of control ...

Chaotic Behavior In High-Gain Interleaved Dc-Dc Converters, 2018 Missouri University of Science and Technology

#### Chaotic Behavior In High-Gain Interleaved Dc-Dc Converters, Ahmad Alzahrani, Pourya Shamsi, Mehdi Ferdowsi, Cihan H. Dagli

*Pourya Shamsi*

In this paper, chaotic behavior in high gain dc-dc converters with current mode control is explored. The dc-dc converters exhibit some chaotic behavior because they contain switches. Moreover, in power electronics (circuits with more passive elements), the dynamics become rich in nonlinearity and become difficult to capture with linear analytical models. Therefore, studying modeling approaches and analysis methods is required. Most of the high-gain dc-dc boost converters cannot be controlled with only voltage mode control due to the presence of right half plane zero that narrows down the stability region. Therefore, the need of current mode control is necessary to ...

Singular Perturbation Theory For Dc-Dc Converters And Application To Pfc Converters, 2018 Missouri University of Science and Technology

#### Singular Perturbation Theory For Dc-Dc Converters And Application To Pfc Converters, Jonathan W. Kimball, Philip T. Krein

*Jonathan W. Kimball*

Many control schemes for dc-dc converters begin with the assertion that inductor currents are "fast" states and capacitor voltages are "slow" states. This assertion must be true for power factor correction (PFC) converters to allow independent control of current and voltage. In the present work, singular perturbation theory is applied to boost converters to provide rigorous justification of the time scale separation. Krylov-Bogoliubov-Mitropolsky (KBM) averaging is used to include switching ripple effects. A relationship between inductance, capacitance, load resistance, and loss resistances derives from an analysis of an approximate model. Similar results hold for buck and buck-boost converters. An experimental ...

Series-Parallel Approaches And Clamp Methods For Extreme Dynamic Response With Advanced Digital Loads, 2018 Missouri University of Science and Technology

#### Series-Parallel Approaches And Clamp Methods For Extreme Dynamic Response With Advanced Digital Loads, Philip T. Krein, Jonathan W. Kimball

*Jonathan W. Kimball*

The series-input parallel-output dc-dc converter combination provides inherent sharing among the converters. With conventional controls, however, this sharing is unstable. Recent literature work proposes complicated feedback loops to correct the problem, at the cost of dynamic performance. This paper shows that a simple sensorless current mode control stabilizes sharing with fast dynamics suitable for advanced digital loads. With this control in place, a "super-matched" current sharing control emerges. Sharing occurs through transients, limited only by the energy limits of the converters. The control approach has considerable promise for high-performance voltage regulator modules. For even faster response, clamping techniques are proposed.

Reducing Common-Mode Voltage In Three-Phase Sine-Triangle Pwm With Interleaved Carriers, 2018 Missouri University of Science and Technology

#### Reducing Common-Mode Voltage In Three-Phase Sine-Triangle Pwm With Interleaved Carriers, Jonathan W. Kimball, Maciej Jan Zawodniok

*Jonathan W. Kimball*

Interleaving PWM waveforms is a proven method to reduce ripple in dc-dc converters. The present work explores interleaving for three-phase motor drives. Fourier analysis shows that interleaving the carriers in conventional uniform PWM significantly reduces the common-mode voltage. New DSP hardware supports interleaving directly with changes to just two registers at setup time, so no additional computation time is needed during operation. The common-mode voltage reduction ranges from 36% at full modulation to 67% when idling with zero modulation. Third harmonic injection slightly reduces the advantage (to 26% at full modulation). However, the maximum RMS common-mode voltage is still less ...

Predicting Solar Irradiance Using Time Series Neural Networks, 2018 Missouri University of Science and Technology

#### Predicting Solar Irradiance Using Time Series Neural Networks, Ahmad Alzahrani, Jonathan W. Kimball, Cihan H. Dagli

*Jonathan W. Kimball*

Increasing the accuracy of prediction improves the performance of photovoltaic systems and alleviates the effects of intermittence on the systems stability. A Nonlinear Autoregressive Network with Exogenous Inputs (NARX) approach was applied to the Vichy-Rolla National Airport's photovoltaic station. The proposed model uses several inputs (e.g. time, day of the year, sky cover, pressure, and wind speed) to predict hourly solar irradiance. Data obtained from the National Solar Radiation Database (NSRDB) was used to conduct simulation experiments. These simulations validate the use of the proposed model for short-term predictions. Results show that the NARX neural network notably outperformed ...

Non-Unity Active Pfc Methods For Filter Size Optimization, 2018 Missouri University of Science and Technology

#### Non-Unity Active Pfc Methods For Filter Size Optimization, Yongxiang Chen, Jonathan W. Kimball, Philip T. Krein

*Jonathan W. Kimball*

Active power factor correction seeks to obtain unity power factor and sinusoidal line currents. Optimized nonsinusoidal line currents reduce filter capacitor requirements with a nonunity target power factor. Implementation methods are presented that permit reduced power factor to be traded off against filter size in a nearly optimum manner. A simple waveform shape can reduce filter component size by about 40% in active PFC converters at the same level of complexity as in conventional PFC designs while yielding power factor as high as 0.9. Two approximate methods to generate appropriate shapes are presented. They offer direct practical implementation of ...

Modeling Controlled Switches And Diodes For Electro-Thermal Simulation, 2018 Missouri University of Science and Technology

#### Modeling Controlled Switches And Diodes For Electro-Thermal Simulation, Jonathan W. Kimball

*Jonathan W. Kimball*

Designers of advanced power converters may choose from a variety of switching device models for simulation. Some situations call for simple idealized models, while others require physics-based models. When evaluating thermal system performance, a behavioral model that includes both conduction and switching losses is desired. A set of models has been developed to include both unidirectional devices, such as IGBTs, BJTs, and diodes, and bidirectional devices, such as MOSFETs. Logic and timing elements are used to insert voltage and current sources into the circuit at appropriate times. All losses affect circuit operation, so simulation can accurately predict losses when the ...

Modern Laboratory-Based Education For Power Electronics And Electric Machines, 2018 Missouri University of Science and Technology

#### Modern Laboratory-Based Education For Power Electronics And Electric Machines, Robert S. Balog, Zakdy Sorchini, Jonathan W. Kimball, Patrick L. Chapman, Philip T. Krein

*Jonathan W. Kimball*

The study of modern energy conversion draws upon a broad range of knowledge and often requires a fair amount of experience. This suggests that laboratory instruction should be an integral component of a power electronics and electric machines curriculum. However, before a single watt can be processed in a realistic way, the student must understand not only the operation of conversion systems but also more advanced concepts such as control theory, speed and position sensing, switching signal generation, gate drive isolation, circuit layout, and other critical issues. Our approach is to use a blue-box module where these details are pre-built ...

Modeling Of Capacitor Impedance In Switching Converters, 2018 Missouri University of Science and Technology

#### Modeling Of Capacitor Impedance In Switching Converters, Jonathan W. Kimball, Philip T. Krein, Kevin R. Cahill

*Jonathan W. Kimball*

Switched capacitor (SC) converters are gaining acceptance as alternatives to traditional, inductor-based switching power converters. Proper design of SC converters requires an understanding of all loss sources and their impacts on circuit operation. In the present work, an equivalent resistance method is developed for analysis, and equivalent resistance formulae are presented for various modes of operation. Quasiresonant converters are explored and compared to standard SC converters. Comparisons to inductor-based switching power converters are made. A number of capacitor technologies are evaluated and compared for applications to both SC converters and inductor-based converters. The resulting model can be used to accurately ...

Low-Input-Voltage, Low-Power Boost Converter Design Issues, 2018 Missouri University of Science and Technology

#### Low-Input-Voltage, Low-Power Boost Converter Design Issues, Jonathan W. Kimball, Theresa L. Flowers, Patrick L. Chapman

*Jonathan W. Kimball*

Issues associated with boost converter design and performance are investigated when a low input voltage is used. Low-input-voltage sources include single fuel cells, single solar cells, and thermoelectric devices. The primary context is interfacing single micro fuel cells to portable electronic loads, such as mobile phones. Efficiency and circuit startup are the two most difficult issues for a low-cost design. It is shown in theory and experiment that the boost converter has a voltage collapse point. A simple startup technique is proposed that is appropriate for some applications.

Machine Design Considerations For The Future Energy Challenge, 2018 Missouri University of Science and Technology

#### Machine Design Considerations For The Future Energy Challenge, Jonathan W. Kimball, Marco Amrhein

*Jonathan W. Kimball*

Motors consume a significant fraction of electricity in the United States and in the world. As part of the International Future Energy Challenge, student teams are endeavoring to improve the efficiency of fractional-horsepower machines. The present work summarizes the motor design and construction process for a 500 W prototype induction machine targeting efficiency above 80%. Analytical and finite-element results are shown.

Issues With Low-Input-Voltage Boost Converter Design, 2018 Missouri University of Science and Technology

#### Issues With Low-Input-Voltage Boost Converter Design, Jonathan W. Kimball, Theresa L. Flowers, Patrick L. Chapman

*Jonathan W. Kimball*

This paper addresses boost converter circuits that are built for very low input voltages, i.e. less than 1 V. Such circuits can be useful for single-cell solar and fuel cell power supplies. Important issues are physical size, high conversion ratio, efficiency, and startup. Several experimental studies show the impact of these issues. A startup technique is proposed that works for arbitrarily low input voltages.

Increased Performance Of Battery Packs By Active Equalization, 2018 Missouri University of Science and Technology

#### Increased Performance Of Battery Packs By Active Equalization, Jonathan W. Kimball, Brian T. Kuhn, Philip T. Krein

*Jonathan W. Kimball*

Battery packs for most applications are series strings of electrochemical cells. Due to manufacturing variations, temperature differences, and aging, the individual cells perform differently. When a complete pack is charged and discharged as a single two-terminal circuit element, some cells are chronically overcharged, undercharged, or overdischarged, all of which act to reduce cell life. The performance and life of the complete pack is limited by the weakest cell. Many methods have been proposed and explored to mitigate this problem. In the present work, a switched-capacitor converter is shown to be a simple and effective method to maintain equal cell or ...

Hysteresis And Delta Modulation Control Of Converters Using Sensorless Current Mode, 2018 Missouri University of Science and Technology

#### Hysteresis And Delta Modulation Control Of Converters Using Sensorless Current Mode, Jonathan W. Kimball, Philip T. Krein, Yongxiang Chen

*Jonathan W. Kimball*

Sensorless current mode (SCM) is a control formulation for dc-dc converters that results in voltage-source characteristics, excellent open-loop tracking, and near-ideal source rejection. Hysteresis and delta modulation are well-known, easy-to-construct large-signal methods for switched systems. Combining either large-signal method with SCM creates a controller that is simpler and more robust than a pulse-width modulation (PWM) based controller. The small-signal advantages of PWM-based SCM are retained and expanded to include converter response to large-signal disturbances. These approaches can be used with any converter topology over a broad range of operating conditions. In the present work, hysteresis and delta modulation SCM controllers ...

Evaluating Conduction Loss Of A Parallel Igbt-Mosfet Combination, 2018 Missouri University of Science and Technology

#### Evaluating Conduction Loss Of A Parallel Igbt-Mosfet Combination, Jonathan W. Kimball, Patrick L. Chapman

*Jonathan W. Kimball*

A variety of power devices are available to designers, each with specific advantages and limitations. For inverters, typically an IGBT combined with a p-i-n diode is used to obtain high current density. Recent developments in high-voltage MOSFETs support other alternatives. For example, a MOSFET can be paralleled with an IGBT to reduce losses at low currents, while the IGBT carries the load at high currents. The current work evaluates conduction losses in this configuration, showing applicability to generic inverters.

Dynamic Maximum Power Point Tracking Of Photovoltaic Arrays Using Ripple Correlation Control, 2018 Missouri University of Science and Technology

#### Dynamic Maximum Power Point Tracking Of Photovoltaic Arrays Using Ripple Correlation Control, Trishan Esram, Jonathan W. Kimball, Philip T. Krein, Patrick L. Chapman, Pallab Midya

*Jonathan W. Kimball*

A dynamically rapid method used for tracking the maximum power point of photovoltaic arrays, known as ripple correlation control, is presented and verified against experiment. The technique takes advantage of the signal ripple, which is automatically present in power converters. The ripple is interpreted as a perturbation from which a gradient ascent optimization can be realized. The technique converges asymptotically at maximum speed to the maximum power point without the benefit of any array parameters or measurements. The technique has simple circuit implementations.

Digital Ripple Correlation Control For Photovoltaic Applications, 2018 Missouri University of Science and Technology

#### Digital Ripple Correlation Control For Photovoltaic Applications, Jonathan W. Kimball, Philip T. Krein

*Jonathan W. Kimball*

Ripple correlation control (RCC) is a fast, robust online optimization technique. RCC is particularly suited for switching power converters, where the inherent ripple provides information about the system operating point. The present work examines a digital formulation that has reduced power consumption and greater robustness. A maximum power point tracker for a photovoltaic panel demonstrates greater than 99% tracking accuracy and fast convergence.

Discrete-Time Ripple Correlation Control For Maximum Power Point Tracking, 2018 Missouri University of Science and Technology

#### Discrete-Time Ripple Correlation Control For Maximum Power Point Tracking, Jonathan W. Kimball, Philip T. Krein

*Jonathan W. Kimball*

Ripple correlation control (RCC) is a high-performance real-time optimization technique that has been applied to photovoltaic maximum power point tracking. This paper extends the previous analog technique to the digital domain. The proposed digital implementation is less expensive, more flexible, and more robust. with a few simplifications, the RCC method is reduced to a sampling problem; that is, if the appropriate variables are sampled at the correct times, the discrete-time RCC (DRCC) algorithm can quickly find the optimal operating point. First, the general DRCC method is derived and stability is proven. Then, DRCC is applied to the photovoltaic maximum power ...

Digital Scr Control Box For Educational Laboratory, 2018 Missouri University of Science and Technology

#### Digital Scr Control Box For Educational Laboratory, Zakdy Sorchini, Jonathan W. Kimball, Philip T. Krein

*Jonathan W. Kimball*

A "blue box" has been designed to introduce the silicone controlled rectifier (SCR) to power electronics students. SCRs are useful in many real-world applications, and are conceptually important in a student's understanding of power converters. The box is highly flexible in application, and its internal design is simple enough to explain to students. Experiments are shown, both of the type commonly used in the laboratory and of the type used for demonstrations. The box has also been designed to be suitable for research purposes and line voltage applications.