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

Electrolytic capacitors are often needed to provide the high-density energy storage required by ac-powered LED drivers; however, they are also well known for their short lifespans. Eliminating electrolytic capacitors in ac–dc LED driver design has become a very important target to improve LED driver technology. In this paper, a cycle-by-cycle energy buffering LED driver has been proposed to achieve electrolytic capacitor-less flicker-free operation. An energy buffering unit, with high-voltage film capacitors being the energy storage device, is introduced in the design to buffer the imbalanced energy in every switching cycle. The switching current can be controlled to meet high power factor correction requirement, while maintaining dc LED output current at the same time. Compared to previous electrolytic capacitor-less designs, this technology can reduce circulating power and, therefore, power conversion loss. A 15-W experimental prototype had been built and tested to verify the proposed LED driving method.

LED Driver Achieves Electrolytic Capacitor-Less and Flicker-Free Operation With an Energy Buffer Unit

Z-source inverter provides a competitive single-stage dc–ac power conversion with the capability of both buck and boost voltage regulation. In order to maximize voltage gain and to increase efficiency, this paper proposes an improved pulse-width modulation (PWM) strategy. By adjusting the shoot-through duty ratio of one-phase leg, it regulates the average value of intermediate dc-link voltage, which is the same as the instantaneous maximum of three-phase line voltage in one switching time period $(T_{s})$ . And the other two-phase legs maintain the fixed switching states. Thus, the equivalent switching frequency of power devices in the inverter bridge is reduced to $1/ 3f_{s}$ ( $f_{s}$ is the frequency corresponding to $T_{s}$ ). The operating principles and closed-loop controller design are analyzed and verified by simulation and experiments. Compared with the existing PWM strategies, the improved PWM (IPWM) strategy demonstrates higher efficiency under full operation range of low voltage gain (1.27-2) application. However, with the IPWM strategy, the inductor current and capacitor voltage contain six-time-line-frequency ripples, which consequently require large size of the passive components when the output frequency is very low. Thus, it is also suitable for 400–800-Hz medium frequency aircraft and vessel power supply system due to a relatively high output line frequency. Furthermore, the idea of IPWM strategy can be extended to other kinds of three-phase impedance network-based inverters.

An Improved PWM Strategy for Z-Source Inverter With Maximum Boost Capability and Minimum Switching Frequency

As switching frequency increases, to reduce the gate drive loss combined with the zero-voltage-switching (ZVS) technique is meaningful for the widely used full-bridge (FB) converters. A dual-channel isolated resonant gate driver (RGD) is proposed in this paper. The proposed RGD is able to provide two isolated complementary drive signals for a pair of power MOSFETs in one bridge leg. Furthermore, the proposed RGD reduces about 79% gate drive loss compared to the conventional voltage source driver (VSD). In addition, the negative gate drive voltage provided by the proposed RGD prevents the false trigger problem in the FB converters. The comparison to the conventional VSDs demonstrates the power loss reduction achieved by the proposed RGD. The principle of operation and optimum design of the proposed RGD are given in detail. A 200-VDC input, 48-V/20-A output, and 500-kHz phase-shift ZVS FB converter with the proposed RGD was built to verify the advantages and efficiency improvement.

A High-Frequency Dual-Channel Isolated Resonant Gate Driver With Low Gate Drive Loss for ZVS Full-Bridge Converters

The single stage LED Driver can achieve relatively high efficiency, however the low frequency ripple current is too significant if high power factor has been achieved. With two stages AC-DC LED Driver structure, we can achieve high power factor and tight current regulation at the same time. However, the drawback of the two stage structure is relatively low efficiency and high component cost. In this paper, an innovative single stage LED Driver with ripple cancellation technology has been proposed. We can achieve almost as high efficiency and low component cost as single stage LED Driver while maintaining comparable performance to the two stages LED Driver. Our experimental prototype can achieve 1.5mA Pk-Pk 120Hz ripple current, 0.99 power factor and 85.5% efficiency for a universal AC input, 35W (50V-0.7A) output application.

Zero ripple single stage AC-DC LED driver with unity power factor

A self core reset and zero voltage switching (ZVS) forward converter topology is presented in this paper. By employing a simple auxiliary circuit, the proposed topology is able to achieve self reset of the power transformer without the use of the conventional tertiary reset winding, and its main switch can be turned on and turned off under ZVS independent of line and load conditions. This simplifies the power transformer, and the switching losses are substantially removed to improve the overall efficiency. Steady state analysis of the circuit is performed. Based on the analysis, a design procedure is presented, and the effects of the circuit parameters on the flux excursion of the power transformer are investigated to make sure self reset can be achieved without increasing the core losses. Simulation and experiment on a 5 V, 100 W prototype circuit operated at 200 kHz are carried out to verify the design, about 5% higher overall efficiency is obtained in the prototype converter than in its conventional counterpart.

Yan-Fei Liu

Papers

LED Driver Achieves Electrolytic Capacitor-Less and Flicker-Free Operation With an Energy Buffer Unit

An Improved PWM Strategy for Z-Source Inverter With Maximum Boost Capability and Minimum Switching Frequency

A High-Frequency Dual-Channel Isolated Resonant Gate Driver With Low Gate Drive Loss for ZVS Full-Bridge Converters

Zero ripple single stage AC-DC LED driver with unity power factor

A self core reset and zero voltage switching forward converter topology