다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The authors discuss high-voltage power conversion. Conventional series connection and three-level voltage source inverter techniques are reviewed and compared. A novel versatile multilevel commutation cell is introduced: it is shown that this topology is safer and more simple to control, and delivers purer output waveforms. The authors show how this technique can be applied to either choppers or voltage-source inverters and generalized to any number of switches.<<ETX>>

Multi-level conversion : high voltage choppers and voltage-source inverters

This paper proposes a sliding-mode control (SMC)-based scheme for the variable-speed direct-driven wind energy conversion systems (WECS) equipped with a permanent magnet synchronous generator connected to the grid. In this paper, diode rectifier, boost converter, neutral point clamped inverter, and L filter are used as the interface between the wind turbine and grid. This topology has abundant features such as simplicity for low- and medium-power wind turbine applications. It is also less costly than back-to-back two-level converters in medium-power applications. The SMC approach demonstrates great performance in complicated nonlinear systems control such as WECS. The proposed control strategy modifies reaching law (RL) of the sliding mode technique to reduce chattering issue and to improve total harmonic distortion property compared to conventional RL SMC. The effectiveness of the proposed control strategy is explored by simulation study on a 4-kW wind turbine, and then verified by experimental tests for a 2-kW setup.

Sliding Mode Control of PMSG Wind Turbine Based on Enhanced Exponential Reaching Law

Provided is an electric power converter. A First and second series circuits of switching devices and a series circuit of capacitors are connected in parallel. Between the connection point in the first series circuit of switching devices and the connection point in the series circuit of capacitors, a first bidirectional switch is connected and, between the connection point in the second series circuit of switching devices and the connection point in the series circuit of capacitors, a second bidirectional switch is connected. The connection point in the first series circuit of switching devices is connected through a reactor to an input-output common connection line connected to one end of an AC power supply and the other end of the AC power supply is connected to the connection point in the series circuit of capacitors.

Electric power converter

This paper proposes a modified conation of single-phase pack U-cell (PUC) multilevel inverter in which the output voltage has higher amplitude than the maximum dc link value used in the topology as a boost operation. The introduced inverter generates seven-level ac voltage at the output using two dc links and six semiconductor switches. Comparing to cascaded H-bridge and neutral point clamp multilevel inverters, the introduced multilevel inverter produces more voltage levels using less components. The proposed inverter is used in photovoltaic (PV) system where the green power comes from two separate PV panels connected to the dc links through dc–dc converters to draw the maximum power. Due to boost operation of this inverter, two different PV panels can combine and send their powers to the grid. Simulations and experimental tests are conducted to investigate the good dynamic performance of the inverter in grid-connected PV system.

Modified Seven-Level Pack U-Cell Inverter for Photovoltaic Applications

This paper presents a closed-loop space vector modulation (SVM)-based sliding mode controller (SMC) for a three-level grid-connected neutral point clamped (3L-NPC) inverter. The nonlinear SMC based on Gao's reaching law has been designed to control the grid current and inject desired amount of active and reactive power into the network. Due to using single dc source at the NPC inverter dc bus, neutral point voltage is controlled through redundant switching states and instantaneous dc voltage feedback integrated into SVM technique. Meanwhile, there is no external voltage controller involved, thus no associated fine tuning issues are existed. The performance of the proposed hybrid controller to inject a desired active/reactive power to the grid is investigated through external perturbations such as change in the line current amplitude/phase shift, ac voltage fluctuation, as well as dc voltage variation. Full converter state-space model was developed and simulated. Experimental results are provided to verify the fast dynamic performance, low content of line current THD%, and good voltage balancing of dc bus capacitors of the NPC inverter.

/pdf/design-and-implementation-of-space-vector-modulation-based-4fnjoklvt2.pdf

Design and Implementation of Space Vector Modulation-Based Sliding Mode Control for Grid-Connected 3L-NPC Inverter

In this paper, a fixed-frequency pulsewidth modulation (PWM) based on sliding-mode current controller is designed and applied to a utility interface three-phase/wire/level neutral-point-clamped inverter. The proposed design methodology of the sliding-mode control is based on a constant switching frequency operation and on Gao’s reaching law that allows chattering compensation. The aim of the controller is to inject a controlled active power from renewable energy sources into the grid while controlling the power factor and minimizing supply current harmonics. Moreover, the dc-link voltages across the split capacitors are controlled with a simple proportional–integral (PI) regulator. Experimental results show the advantages of the proposed control algorithm in terms of fast dynamic response, low voltage ripple on the dc bus, low current Total Harmonic Distortion, and robustness toward external perturbations from the dc and ac sides; moreover, a comparison with a PWM–PI current controller is presented.

/pdf/sliding-mode-fixed-frequency-current-controller-design-for-3dkj0ssbs9.pdf

Sliding Mode Fixed Frequency Current Controller Design for Grid-Connected NPC Inverter

In this article, we propose a modified finite-set model predictive control (M-FS-MPC) for multilevel switching-mode operation of grid-connected nine-level packed E-cell (PEC9) inverter With a single-dc source, six power switches, back-to-back-connected switches as bidirectional and two capacitors horizontally extended, PEC9 inverter topology has remarkably reduced the components count Packed E-cell (PEC) prominent feature has the capability of switching among different multilevel voltages: nine-, seven-, or five-level under faulty switch cases without any structural modification and only if the controller is appropriately designed M-FS-MPC is proposed to operate the grid-connected PEC with the multilevel switching mode under bidirectional switch fault operation Switching among five-, seven-, or nine-level voltages is attained by proper dc capacitors’ voltages regulation, whereas the desired current injection with low total harmonic distortion (THD) and requested power factor for addressing grid connectivity applications is guaranteed The system discrete model is developed and the experimental results verify the performance and robustness of M-FS-MPC in targeting the capability of PEC multilevel switching-mode operation and grid connectivity requirements in both steady and transient states

Multilevel Switching-Mode Operation of Finite-Set Model Predictive Control for Grid-Connected Packed E-Cell Inverter

In this paper, a novel controller based on the predictive technique has been introduced for a neutral-point-clamped grid-tied inverter. The aim of the developed method is to achieve a constant system switching frequency operation. The proposed method generates the voltage vector by nullifying the derivative of the cost function of a finite-set model predictive controller. The developed controller takes in action of injecting the desired grid current while a closed-loop space vector modulator regulates the capacitors voltages. A comparative study with a similar model predictive algorithm with constant switching frequency (MPC-CSF) is introduced and discussed in terms of computational complexity. Experimental results are provided to verify the performance and robustness of the new method over MPC-CSF with its ability of injecting a very low total harmonic distortion to the grid with almost unity power factor during normal and transient operations.

Novel Current Controller Based on MPC With Fixed Switching Frequency Operation for a Grid-Tied Inverter

Nowadays, the three-level neutral point clamped (3L-NPC) inverter has become more attractive among multilevel inverters topologies, especially in transformerless grid connected photovoltaic systems. Due to the unbalance between the two DC load-side capacitor voltages, the development and improvement of such topology were important topics in recent studies. New structures were derived focusing on better distribution of losses, increasing efficiency, decreasing the switching devices losses and the conduction losses. For this reason, seven derived topologies are discussed in this paper and compared among the conventional inverter. In addition, a part of this study focuses on modifying modulation techniques in order to comply with the neutral point fluctuation problem. Several carrier-based PWM and space vector modulation techniques are considered, discussed and compared.

Fadia Sebaaly

Papers

Design and Implementation of Space Vector Modulation-Based Sliding Mode Control for Grid-Connected 3L-NPC Inverter

Sliding Mode Fixed Frequency Current Controller Design for Grid-Connected NPC Inverter

Multilevel Switching-Mode Operation of Finite-Set Model Predictive Control for Grid-Connected Packed E-Cell Inverter

Novel Current Controller Based on MPC With Fixed Switching Frequency Operation for a Grid-Tied Inverter

Three-level neutral-point-clamped inverters in transformerless PV systems — State of the art