scholarly journals Vector Control of Three-Phase Solar Farm Converters Based on Fictive-Axis Emulation

2020 ◽  
Vol 2 (3) ◽  
Author(s):  
Kai Kang ◽  
Qiaoyu Wang ◽  
Jiayi Meng
Keyword(s):  
Steady State ◽  
Controller Design ◽  
Dynamic Performance ◽  
Reference Signal ◽  
Voltage Source ◽  
Phase System ◽  
The Real ◽  
Control Gain ◽  
Three Phase ◽  
Set Up

In this paper, a new method for adjusting the current of three-phase voltage source DC-AC converter in orthogonal (DQ) reference frame is presented. In the DQ reference system, AC variable appears in the constant form of DC, making the controller design the same as the DC-DC converter[1]. It provides infinite control gain at the steady-state operating point, and finally realizes zero steady-state error[2]. In addition, the common method is to set up a set of virtual quantities orthogonal to the actual single-phase system. In general, orthogonal imaginary numbers get the reference signal by delaying the real quantity by a quarter period. However, the introduction of such time delay makes the dynamic response of the system worse. In this paper, orthogonal quantities are generated from a virtual axis system parallel to the real axis, which can effectively improve the dynamic performance of traditional methods without increasing the complexity of controller structure. Through PSCAD simulation, the ideal experimental results are obtained.

scholarly journals Analysis of direct power control AC-DC converter under unbalance voltage supply for steady-state and dynamic response

2020 ◽  
Vol 10 (4) ◽  
pp. 3333
Author(s):  
Nor Azizah Mohd Yusoff ◽  
Azziddin M. Razali ◽  
Kasrul Abdul Karim ◽  
Raja Nor Firdaus Kashfi Raja Othman ◽  
Auzani Jidin ◽  
...  
Keyword(s):  
Steady State ◽  
Power Control ◽  
Pulse Width Modulation ◽  
Dynamic Performance ◽  
Harmonic Distortion ◽  
Voltage Source ◽  
Phase System ◽  
Direct Power ◽  
Direct Power Control ◽  
Three Phase

This paper presents an analysis of Direct Power Control (DPC) technique for the Three-Phase Pulse Width Modulation (PWM) AC-DC converter under unbalanced supply condition. Unbalance condition will cause the presence of unbalanced current and voltages thus produce the negative components on the grid voltage as well as severe performance degradation of a grid connected Voltage Source Inverter (VSI). The input structures for conventional DPC has been modified with a three simpler sequence networks instead of coupled by a detailed Three-Phase system method. The imbalance voltage can be resolved by separating from the individual elements of voltage and current into symmetrical components called Sequence Network. Consequently, the input power relatively improved during unbalanced condition almost 70% through the measurement of Total Harmonic Distortion (THD) from the conventional Direct Power Control (DPC) in individual elements which is higher compared to separate components. Hence, several analyses are performed in order to analyze the steady state and dynamic performance of the converter, particularly during the load and DC voltage output reference variations.

Inductor Saturation Compensation in Three-Phase Three-Wire Voltage-Source Converters via Inverse System Dynamics-I

2020 ◽  
Author(s):  
Ziya Özkan ◽  
Ahmet Masum Hava
Keyword(s):  
Dynamic Model ◽  
Dynamic Performance ◽  
Current Control ◽  
Inverse System ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Two Phase ◽  
Inverse Dynamic ◽  
Three Phase ◽  
Steady State Current

In three-phase three-wire (3P3W) voltage-source converter (VSC) systems, utilization of filter inductors with deep saturation characteristics is often advantageous due to the improved size, cost, and efficiency. However, with the use of conventional synchronous frame current control (CSCC) methods, the inductor saturation results in significant dynamic performance loss and poor steady-state current waveform quality. This paper proposes an inverse dynamic model based compensation (IDMBC) method to overcome these performance issues. Accordingly, a review of inductor saturation and core materials is performed, and the motivation on the use of saturable inductors is clarified. Then, two-phase exact modelling of the 3P3W VSC control system is obtained and the drawbacks of CSCC have been demonstrated analytically. Based on the exact modelling, the inverse system dynamic model of the nonlinear system is obtained and employed such that the nonlinear plant is converted to a fictitious linear inductor system for linear current regulators to perform satisfactorily.

scholarly journals Muscle: A Three Phase System

1959 ◽  
Vol 43 (1) ◽  
pp. 55-79 ◽  
Author(s):  
Shirley E. Simon ◽  
B. M. Johnstone ◽  
K. H. Shankly ◽  
F. H. Shaw
Keyword(s):  
Steady State ◽  
Sartorius Muscle ◽  
Phase System ◽  
Extracellular Material ◽  
Foreign Ions ◽  
Three Phase ◽  
Na Efflux ◽  
Muscle Water ◽  
Toad Bufo ◽  
Normal Controls

The partition of Li+, Br-, and I- across the membrane of the sartorius muscle of the toad Bufo marinus has been investigated both at the steady state and with kinetic methods. Li+ was found to have access to an amount of muscle water similar to that of Na+. Br- and I- could be regarded as being interchangeable with cellular Cl-. None of the foreign ions caused significant losses of cellular K+. Li+ efflux from the cell was slower in muscles which were equilibrated for long periods in Li+ than in short equilibrated muscles. Na+ efflux from Li+-treated muscles was similar in rate to normal controls, but the amount of Na+ in the slow fraction was increased by Li+. I- efflux was extremely rapid, and it was not possible to differentiate kinetically between intra- and extracellular material. These results have been found to be consistent with the hypothesis of a three phase system for muscle.

scholarly journals HIL-Assessed Fast and Accurate Single-Phase Power Calculation Algorithm for Voltage Source Inverters Supplying to High Total Demand Distortion Nonlinear Loads

Electronics ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 1643
Author(s):  
Jorge El Mariachet ◽  
Yajuan Guan ◽  
Jose Matas ◽  
Helena Martín ◽  
Mingshen Li ◽  
...  
Keyword(s):  
Steady State ◽  
Single Phase ◽  
Reactive Power ◽  
Dynamic Performance ◽  
Active Power ◽  
Voltage Source ◽  
Power Calculation ◽  
Calculation Algorithm ◽  
Nonlinear Loads ◽  
Voltage Source Inverters

The dynamic performance of the local control of single-phase voltage source inverters (VSIs) can be degraded when supplying to nonlinear loads (NLLs) in microgrids. When this control is based on the droop principles, a proper calculation of the active and reactive averaged powers (P–Q) is essential for a proficient dynamic response against abrupt NLL changes. In this work, a VSI supplying to an NLL was studied, focusing the attention on the P–Q calculation stage. This stage first generated the direct and in-quadrature signals from the measured load current through a second-order generalized integrator (SOGI). Then, the instantaneous power quantities were obtained by multiplying each filtered current by the output voltage, and filtered later by utilizing a SOGI to acquire the averaged P–Q parameters. The proposed algorithm was compared with previous proposals, while keeping the active power steady-state ripple constant, which resulted in a faster calculation of the averaged active power. In this case, the steady-state averaged reactive power presented less ripple than the best proposal to which it was compared. When reducing the velocity of the proposed algorithm for the active power, it also showed a reduction in its steady-state ripple. Simulations, hardware-in-the-loop, and experimental tests were carried out to verify the effectiveness of the proposal.

scholarly journals Application of Hollow Fibre-Liquid Phase Microextraction Technique for Isolation and Pre-Concentration of Pharmaceuticals in Water

Membranes ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 311
Author(s):  
Lawrence Mzukisi Madikizela ◽  
Vusumzi Emmanuel Pakade ◽  
Somandla Ncube ◽  
Hlanganani Tutu ◽  
Luke Chimuka
Keyword(s):  
Liquid Phase ◽  
Solid Phase ◽  
Deep Eutectic Solvents ◽  
Enrichment Factors ◽  
Hollow Fibre ◽  
Phase System ◽  
Phase Extraction ◽  
Liquid Phase Microextraction ◽  
Three Phase ◽  
Set Up

In this article, a comprehensive review of applications of the hollow fibre-liquid phase microextraction (HF-LPME) for the isolation and pre-concentration of pharmaceuticals in water samples is presented. HF-LPME is simple, affordable, selective, and sensitive with high enrichment factors of up to 27,000-fold reported for pharmaceutical analysis. Both configurations (two- and three-phase extraction systems) of HF-LPME have been applied in the extraction of pharmaceuticals from water, with the three-phase system being more prominent. When compared to most common sample preparation techniques such as solid phase extraction, HF-LPME is a greener analytical chemistry process due to reduced solvent consumption, miniaturization, and the ability to automate. However, the automation comes at an added cost related to instrumental set-up, but a reduced cost is associated with lower reagent consumption as well as shortened overall workload and time. Currently, many researchers are investigating ionic liquids and deep eutectic solvents as environmentally friendly chemicals that could lead to full classification of HF-LPME as a green analytical procedure.

scholarly journals Design of a Preview Controller for Discrete-Time Systems Based on LMI

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Li Li ◽  
Fucheng Liao
Keyword(s):  
Steady State ◽  
Discrete Time ◽  
Controller Design ◽  
Design Method ◽  
Reference Signal ◽  
Original System ◽  
Disturbance Attenuation ◽  
Linear Matrix ◽  
Discrete Time Systems ◽  
Time Systems

A preview controller design method for discrete-time systems based on LMI is proposed. First, we use the difference between a system state and its steady-state value, instead of the usual difference between system states, to transform the tracking problem into a regulator problem. Then, based on the Lyapunov stability theory and linear matrix inequality (LMI) approach, the preview controller ensuring asymptotic stability of the closed-loop system for the derived augmented error system is found. And an extended functional observer is designed in this paper which can achieve disturbance attenuation in the estimation process; as a result, the state of the system can be reconstructed rapidly and accurately. The controller gain matrix is obtained by solving an LMI problem. By incorporating the controller obtained into the original system, we obtain the preview controller of the system under consideration. To make sure that the output tracks the reference signal without steady-state error, an integrator is introduced. The numerical simulation example also illustrates the effectiveness of the results in the paper.

scholarly journals Analysis of Stationary- and Synchronous-Reference Frames for Three-Phase Three-Wire Grid-Connected Converter AC Current Regulators

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8348
Author(s):  
Israel D. L. Costa ◽  
Danilo I. Brandao ◽  
Lourenço Matakas Junior ◽  
Marcelo G. Simões ◽  
Lenin M. F. Morais
Keyword(s):  
Steady State ◽  
Reference Frames ◽  
Computational Cost ◽  
Transient Behavior ◽  
Computational Effort ◽  
Superior Performance ◽  
Positive Sequence ◽  
Voltage Source ◽  
Three Phase ◽  
Grid Connected Inverter

The current state of the art shows that unbalance and distortion on the voltage waveforms at the terminals of a grid-connected inverter disturb its output currents. This paper compares AC linear current regulators for three-phase three-wire voltage source converters with three different reference frames, namely: (1) natural (abc), (2) orthogonal stationary (αβ), and (3) orthogonal synchronous (dq). The quantitative comparison analysis is based on mathematical models of grid disturbances using the impedance-based analysis, the computational effort assessment, as well as the steady-state and transient performance evaluation based on experimental results. The control scheme devised in the dq-frame has the highest computational effort and inferior performance under negative-sequence voltage disturbances, whereas it shows superior performance under positive-sequence voltages among the reference frames evaluated. In contrast, the stationary natural frame abc has the lowest computational effort due to its straightforward implementation, with similar results in terms of steady-state and transient behavior. The αβ-frame is an intermediate solution in terms of computational cost.

scholarly journals An Analysis of Virtual Flux Direct Power Control of Three-Phase AC-DC Converter

2018 ◽  
Vol 9 (3) ◽  
pp. 947 ◽  
Author(s):  
Nor Azizah Mohd Yusoff ◽  
Azziddin M. Razali ◽  
Kasrul Abdul Karim ◽  
Auzani Jidin ◽  
Tole Sutikno
Keyword(s):  
Steady State ◽  
Power Control ◽  
Output Voltage ◽  
Pulse Width Modulation ◽  
Dynamic Performance ◽  
Direct Power ◽  
Direct Power Control ◽  
Grid Voltage ◽  
Three Phase ◽  
Virtual Flux

<p>This paper presents an analysis of virtual-flux direct power control (VFDPC) technique for the three-phase pulse width modulation (PWM) ac-dc converter. The proposed VFDPC is developed by assuming the grid voltage and converter line filters quantities are related to a virtual three-phase ac motor. The controller works with less number of sensors by eliminating the voltage sensors used for measuring the three-phase grid voltage. The grid virtual flux which is proportional to the grid voltage will be estimated from the information of converter switching states, line current, and dc-link output voltage. Several analyses are performed in order to study the steady state and dynamic performance of the converter, particularly during the load and DC voltage output reference variations. The proportional integral (PI) controller at the outer voltage control loop of VFDPC is tuned properly and the entire PWM ac-dc converter system is simulated using MATLAB/Simulink to ensure the dc output voltage follow the desired output voltage under steady state and dynamic conditions. Ac-dc converter utilizing the proposed VFDPC is able to generate three-phase input current waveforms that are almost sinusoidal with low harmonics contents which is less than 5% and near unity power factor (<em>pf</em>) operation.</p>

scholarly journals Inductor Saturation Compensation in Three-Phase Three-Wire Voltage-Source Converters via Inverse System Dynamics-I

2020 ◽  
Author(s):  
Ziya Özkan ◽  
Ahmet Masum Hava
Keyword(s):  
Dynamic Model ◽  
Dynamic Performance ◽  
Current Control ◽  
Inverse System ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Two Phase ◽  
Inverse Dynamic ◽  
Three Phase ◽  
Steady State Current

In three-phase three-wire (3P3W) voltage-source converter (VSC) systems, utilization of filter inductors with deep saturation characteristics is often advantageous due to the improved size, cost, and efficiency. However, with the use of conventional synchronous frame current control (CSCC) methods, the inductor saturation results in significant dynamic performance loss and poor steady-state current waveform quality. This paper proposes an inverse dynamic model based compensation (IDMBC) method to overcome these performance issues. Accordingly, a review of inductor saturation and core materials is performed, and the motivation on the use of saturable inductors is clarified. Then, two-phase exact modelling of the 3P3W VSC control system is obtained and the drawbacks of CSCC have been demonstrated analytically. Based on the exact modelling, the inverse system dynamic model of the nonlinear system is obtained and employed such that the nonlinear plant is converted to a fictitious linear inductor system for linear current regulators to perform satisfactorily.

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