There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

This paper presents a detailed description of finite control set model predictive control (FCS-MPC) applied to power converters Several key aspects related to this methodology are, in depth, presented and compared with traditional power converter control techniques, such as linear controllers with pulsewidth-modulation-based methods The basic concepts, operating principles, control diagrams, and results are used to provide a comparison between the different control strategies The analysis is performed on a traditional three-phase voltage source inverter, used as a simple and comprehensive reference frame However, additional topologies and power systems are addressed to highlight differences, potentialities, and challenges of FCS-MPC Among the conclusions are the feasibility and great potential of FCS-MPC due to present-day signal-processing capabilities, particularly for power systems with a reduced number of switching states and more complex operating principles, such as matrix converters In addition, the possibility to address different or additional control objectives easily in a single cost function enables a simple, flexible, and improved performance controller for power-conversion systems

Model Predictive Control—A Simple and Powerful Method to Control Power Converters

Predictive control is a very wide class of controllers that have found rather recent application in the control of power converters. Research on this topic has been increased in the last years due to the possibilities of today's microprocessors used for the control. This paper presents the application of different predictive control methods to power electronics and drives. A simple classification of the most important types of predictive control is introduced, and each one of them is explained including some application examples. Predictive control presents several advantages that make it suitable for the control of power converters and drives. The different control schemes and applications presented in this paper illustrate the effectiveness and flexibility of predictive control.

Predictive Control in Power Electronics and Drives

This paper presents a predictive current control method and its application to a voltage source inverter. The method uses a discrete-time model of the system to predict the future value of the load current for all possible voltage vectors generated by the inverter. The voltage vector which minimizes a quality function is selected. The quality function used in this work evaluates the current error at the next sampling time. The performance of the proposed predictive control method is compared with hysteresis and pulsewidth modulation control. The results show that the predictive method controls very effectively the load current and performs very well compared with the classical solutions

Predictive Current Control of a Voltage Source Inverter

Distributed air-gap inductors such as iron powder chip inductors and low-temperature cofired ceramic (LTCC) inductors have the advantage of low-fringing effect loss However, the flux density nonuniformly distributes in the magnetic cores, which results in the magnetic material closer to the conductor becoming saturated while the magnetic material further away from the conductor is still not fully utilized This paper proposes a multipermeability distributed air-gap inductor structure to increase inductance without the necessity of increasing the inductor volume The best discrete permeability value is investigated Based on the best discrete permeability value, inductance as well as the inductance density trends is calculated by varying the number of permeability layers under the condition that thickness for each layer is constant Also, the inductance variations versus the number of permeability layers are also obtained under the condition that the inductor thickness is constant A three-permeability inductor and a single-permeability inductor are fabricated to evaluate the proposed method The measured results show that the three-permeability inductor has a much higher inductance than the single-permeability inductor for the entire load range Both inductors are tested in a 5-V input, 3-V output dc/dc converter to compare their performances The results show that the three-permeability inductor can further improve the efficiency of high-frequency dc/dc converters

Multipermeability Inductors for Increasing the Inductance and Improving the Efficiency of High-Frequency DC/DC Converters

A digital adaptive current source driver (CSD) is proposed for the interleaved Boost PFC converter. The adaptive drive current is achieved for the CSDs to optimize the switching loss and gate drive loss according to different turn-on and turn-off drain currents in a wide load range. Compared to the adaptive CSDs with the linear regulator, the digital adaptive CSD is able to eliminate the additional loss and cost introduced by the linear regulator. The most important benefit of the digital CSD is that the turn-on and turn-off drive current can be adjusted independently according to the different turn-on and turn-off drain currents. At the same time, the proposed digital CSD is compatible with other advanced digital control technique. The proposed digital CSD is applied to the interleaved Boost PFC converter under critical conduction mode (CRM) to reduce the high turn-off loss and gate drive loss. A 220-V AC input, 380-V/400-W output, two-phase interleaved Boost PFC converter with the switching frequency of 90-500 kHz under CRM was built to verify the functionality and advantages of the digital CSD.

A Digital Adaptive Discontinuous Current Source Driver for High-Frequency Interleaved Boost PFC Converters

Evolutionary pressures have led humans to walk in a highly efficient manner that conserves energy, making it difficult for exoskeletons to reduce the metabolic cost of walking. Despite the challenge, some exoskeletons have managed to lessen the metabolic expenditure of walking, either by adding or storing and returning energy. We show that the use of an exoskeleton that strategically removes kinetic energy during the swing period of the gait cycle reduces the metabolic cost of walking by 2.5 ± 0.8% for healthy male users while converting the removed energy into 0.25 ± 0.02 watts of electrical power. By comparing two loading profiles, we demonstrate that the timing and magnitude of energy removal are vital for successful metabolic cost reduction.

Removing energy with an exoskeleton reduces the metabolic cost of walking

The function control law for a buck converter is derived to achieve zero voltage regulation of the output voltage. A new method to retrieve the low frequency component of the inductor voltage is proposed and analyzed. The stability of the closed loop system using a proportional and differential controller is analyzed. The effect of the supply voltage and load current disturbance is also studied. The analysis, computer simulation by PSPICE and experimental results illustrate that excellent performance can be achieved by the function control law. >

A novel method to achieve zero-voltage regulation in buck converter

Interleaving frequency-controlled LLC resonant converters will encounter load-sharing problem due to the tolerance of the resonant components. In this paper, full-wave and half-wave switch-controlled capacitors (SCCs) are used in LLC stages to solve this problem. By using resonant capacitance as a control variable, the output current can be modulated even when all the LLC stages are synchronized at the same switching frequency. A design procedure is developed. A 600W prototype is built to verify the feasibility.

Yan-Fei Liu

Papers

Multipermeability Inductors for Increasing the Inductance and Improving the Efficiency of High-Frequency DC/DC Converters

A Digital Adaptive Discontinuous Current Source Driver for High-Frequency Interleaved Boost PFC Converters

Removing energy with an exoskeleton reduces the metabolic cost of walking

A novel method to achieve zero-voltage regulation in buck converter

An interleaving and load sharing method for multiphase LLC converters