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

This paper presents a high efficiency high power-density LLC DC-DC converter for Electric Vehicles (EVs) on-board low voltage DC-DC converter (LDC) application In the proposed LDC, primary switches achieve ZVS turn-on and secondary synchronous rectifier switches achieve ZVS turn-on and ZCS turn-off To reduce current stress and improve efficiency, three phase interleaved LLC DC-DC converters are paralleled to provide more than 200A load current Switch-Controlled Capacitor (SCC) technology is used to achieve the load current sharing of the three phase LLC DC-DC converter In addition, GaN HEMTs are used in the transformer primary to improve the switching frequency and power-density To verify the analysis, a 38kW(14V/270A) LLC DC-DC converter prototype is designed The experimental results show that full load efficiency is 958% at 270A load current and 3kW/L power-density is achieved

A High Efficiency High Power-Density LLC DC-DC Converter for Electric Vehicles (EVs) On-Board Low Voltage DC-DC Converter (LDC) Application

In this paper, a five-stage fault protection scheme against the short-circuit fault for parallel high-power three-phase combined inverter to achieve high reliability is proposed. There are two control modes, Voltage Controlled Mode (VCM) and Current Controlled Mode (CCM). VCM operates under normal operation to keep constant output voltage. CCM operates under fault operation to limit the output current, which is combined with hardware current limit circuit and software current limit unit. For parallel inverter system, the output voltage recovers quickly and then switch from CCM to VCM for inverter once the short-circuit fault is recovered. However, A little time difference of switching mode between parallel inverters results in the surge circulating current, which reduces the system reliability. Thus, the pre-synchronized state is added to achieve the current sharing at any time and to achieve simultaneous mode change for each inverter. A prototype with two parallel three-phase 400kVA/50HZ inverters is built to verify the reliability of the proposed method.

Short-circuit fault protection strategy of parallel three-phase inverters

A precisely regulated multiple output forward converter topology is presented in this paper. In this topology, each output voltage is directly and independently regulated by its own feedback control circuit that controls the appropriate synchronous rectifiers in the pertinent output stage, while the main switch is feedforward controlled. Thus, there is no cross regulation between the outputs, and design of each output becomes straightforward. Steady state analysis is performed to understand the topology and to provide design guidance. A prototype circuit with two outputs is built, and experiment are carried out on this prototype and the results verify the concepts and design.

A precisely regulated multiple output forward converter topology

An interleaved LCLC resonant converter with accurate current balancing performance over a wide input voltage range is proposed. Resonant tank components have slight tolerances that can unbalance load sharing between paralleled phases. Because of the steep voltage gain curve of the LCLC resonant tank, most conventional current sharing approaches might not be effective. In the proposed converter, the impedances of the resonant tanks are matched by a switch-controlled capacitor (SCC) that is in series with the resonant capacitor resulting in precise load current balancing between phases. The impact of various unbalanced situations on the interleaved LCLC resonant converter is investigated, a minimum operating angle for the SCC circuit is identified, the basic accuracy of SCC current balancing via digital control is investigated, and a control strategy is proposed to perform the current sharing. Computer simulation results and experimental results from a GaN-based prototype validate the performance of the proposed interleaved LCLC converter with precise current sharing over a wide input voltage range from 250 to 400 V. Using enhancement mode GaN and benefiting from the interleaving feature, a high conversion efficiency is achieved on a two-phase 1 kW LCLC converter with peak efficiency of 96.7%.

Interleaved LCLC Resonant Converter With Precise Current Balancing Over a Wide Input Voltage Range

A soft switching symmetric bipolar outputs dc-transformer (DCX) for eliminating power supply pumping of half-bridge class-D audio amplifiers is proposed in this paper. Compared with the traditional unidirectional front-end dc–dc converter in the half-bridge class-D audio amplifier, output capacitances of the proposed DCX and voltage stress of the half-bridge class-D audio amplifier are significantly reduced. Soft switching of the proposed DCX can be achieved when the load current of half-bridge class-D audio amplifier is positive or negative. Thus, the efficiency and power density of the proposed audio amplifier system can be improved. In addition, the proposed DCX has smoothing transition between the positive load current and the negative load current with a simple open-loop controller. The operating principle of the proposed DCX is analyzed and a 200-W prototype is built up. Experimental results show that power supply pumping is reduced with small DCX output capacitors, symmetric bipolar outputs are obtained and peak efficiency of 96.3% is achieved.

Yan-Fei Liu

Papers

A High Efficiency High Power-Density LLC DC-DC Converter for Electric Vehicles (EVs) On-Board Low Voltage DC-DC Converter (LDC) Application

Short-circuit fault protection strategy of parallel three-phase inverters

A precisely regulated multiple output forward converter topology

Interleaved LCLC Resonant Converter With Precise Current Balancing Over a Wide Input Voltage Range

Soft Switching Symmetric Bipolar Outputs DC-Transformer (DCX) for Eliminating Power Supply Pumping of Half-Bridge Class-D Audio Amplifier