scholarly journals Current Compensation in Grid-Connected VSCs using Advanced Fuzzy Logic-based Fluffy-Built SVPWM Switching

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1259
Author(s):  
Yuvaraja Teekaraman ◽  
Ramya Kuppusamy ◽  
Hamid Reza Baghaee ◽  
Marko Vukobratović ◽  
Zoran Balkić ◽  
...  
Keyword(s):  
Control Variable ◽  
Current Control ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Switching Loss ◽  
Current Compensation ◽  
Intelligent Controller ◽  
Circulating Current ◽  
Utility Grid ◽  
Control Configuration

A main focus in microgrids is the power quality issue. The used renewable sources fluctuate and this fluctuation has to be suppressed by designing a control variable to nullify the circulating current caused by voltage fluctuations and deviations. The switching losses across power electronic switches, harmonics, and circulating current are the issues that we discuss in this article. The proposed intelligent controller is an interface between a voltage-sourced converter and a utility grid that affords default switching patterns with less switching loss, less current harmonic content, and overcurrent protection, and is capable of handling the nonlinearities and uncertainties in the grid system. The interfaced controller needs to be synchronized to a utility grid to ensure that the grid–lattice network can be fine-tuned in order to inject/absorb the prominent complex reactive energy to/from the utility grid so as to maintain the variable power factor at unity, which, in turn, will improve the system’s overall efficiency for all connected nonlinear loads. The intelligent controller for stabilizing a smart grid is developed by implementing a fuzzy-built advance control configuration to achieve a faster dynamic response and a more suitable direct current link performance. The innovation in this study is the design of fuzzy-based space vector pulse width modulation controller that exploits the hysteresis current control and current compensation in a grid-connected voltage source converter. By using the proposed scheme, a current compensation strategy is proposed along with an advanced modulation controller to utilize the DC link voltage of a voltage source converter. To demonstrate the effectiveness of the proposed control scheme, offline digital time-domain simulations were carried out in MATLAB/Simulink, and the simulated results were verified using the experimental setup to prove the effectiveness, authenticity, and accuracy of the proposed method.

scholarly journals Circulating Current Reduction in MMC-HVDC System Using Average Model

2019 ◽  
Vol 9 (7) ◽  
pp. 1383 ◽  
Author(s):  
Kamran Hafeez ◽  
Shahid A. Khan ◽  
Alex Van den Bossche ◽  
Qadeer Ul Hasan
Keyword(s):  
Vector Current ◽  
Current Control ◽  
New Method ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Direct Modulation ◽  
Hvdc System ◽  
Voltage Oscillation ◽  
Average Value ◽  
Circulating Current

: Modular multilevel converters (MMCs) are quickly emerging as a suitable technology for a voltage-source converter-based high-voltage direct-current (VSC-HVDC) transmission systems due to its numerous advantages as reported in literature. However, for a large DC-network, MMCs require large numbers of sub-modules (SMs) and switches, which makes its modeling very challenging and computationally complex using electromagnetic transient (EMT) programs. Average Value Model (AVM) provides a relatively better solution to model MMCs by combining cells as an arm equivalent circuit. Circulating current is an important issue related to the performance and stability of MMCs. Due to circulating currents, power loss in a converter increases as root mean square (RMS) values of the arm current increases. The traditional method for inserting SMs in each arm is based on direct modulation, which does not compensate for the arm voltage oscillations, and generates circulating current in each leg of a three-phase MMC. This paper presents a new method for reducing the circulating current by adding 2nd and 4thharmonics in the upper and lower arm currents of an MMC. Less capacitor energy variations reobtained by the proposed method compared to traditional direct modulation methods. The proposed method is tested on a common symmetrical monopole (point-to-point) MMC-HVDC system using vector current control strategy in PSCAD/EMTDC software. Analytical and simulation results show the effectiveness of the new method in minimizing the circulating current and arm voltage oscillation reductions as compared to the direct modulation approach.

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.

Sliding Mode Control Application in Wind Energy Conversion System Using DSTATCOM

2015 ◽  
Vol 1 (1) ◽  
Author(s):  
R. S. Bajpai ◽  
Amarjeet Singh
Keyword(s):  
Sliding Mode Control ◽  
Sliding Mode ◽  
Harmonic Distortion ◽  
Voltage Control ◽  
Input Voltage ◽  
Current Control ◽  
Control Mode ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Mode Control

This paper deals with sliding mode control of converter and its application to distributed generation. Sliding mode control is used to control the voltage source converter in voltage or current control mode. Modeling and control of H bridge converter system using sliding mode control is proposed. Easily implemented sliding surfaces provide prominent dynamic characteristics against changes in the load and in the input voltage. Distribution static compensator (DSTATCOM) is used to control the voltage of the bus to which it is connected to a balance sinusoid in respect of the harmonic distortion in supply or load side. A variable wind turbine generator is used to produces a variable DC voltage which is placed as input voltage source to converter of DSTATCOM. A control strategy for grid voltage control using DSTATCOM in voltage control mode has been implemented in respect of the wind variation. The results are validated using PSCAD/EMTDC simulation studies.

scholarly journals Hysteresis-Based Current Control Approach by Means of the Theory of Switched Systems

2021 ◽  
Vol 11 (19) ◽  
pp. 9175
Author(s):  
Malte Thielmann ◽  
Florian Hans
Keyword(s):  
State Space ◽  
Switched Systems ◽  
Multiple Equilibria ◽  
Current Control ◽  
The State ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Reference Trajectory ◽  
State Variables ◽  
Control Approach

In this paper, a novel hysteresis-based current control approach is presented. The basis of the developed control approach is the theory of switched systems, in particular, the system class of switched systems with multiple equilibria. The proposed approach guarantees the convergence of the state trajectory into a region around a reference trajectory by selective switching between the individual subsystems. Here, the reference trajectory is allowed to be time varying, but lies within the state space spanned by the subsystem equilibria. Since already published approaches only show convergence to a common equilibrium of all subsystems, the extension to the mentioned state space is a significant novelty. Moreover, the approach is not limited to the number of state variables, nor to the number of subsystems. Thus, the applicability to a large number of systems is given. In the course of the paper, the theoretical basics of the approach are first explained by referring to a trivial example system. Then, it is shown how the theory can be applied to a practical application of a voltage source converter that is connected to a permanent-magnet synchronous motor. After deriving the limits of the presented control strategy, a simulation study confirms the applicability on the converter system. The paper closes with a detailed discussion about the given results.

scholarly journals A new passive islanding detection technique for different zones in utility grid

2021 ◽  
Vol 9 (3B) ◽  
Author(s):  
Yasser Ahmed Elshrief ◽  
◽  
A. D. Asham ◽  
Belal Ahmed Abozalam ◽  
Sameh Abd-Elhaleem ◽  
...  
Keyword(s):  
Large Scale ◽  
Detection Algorithm ◽  
Rate Of Change ◽  
Voltage Source ◽  
Small Scale ◽  
Voltage Source Converter ◽  
Islanding Detection ◽  
Utility Grid ◽  
Convenient Technique ◽  
The Impact

Distributed generation (DG) has reformed the meaning of traditional generation of power from large-scale to small-scale generation. The main issue of connecting the DG to the utility grid is the detection of unintended islanding. This paper shows the impact of the islanding phenomenon in the case of grid-connected photovoltaic arrays and how to develop a convenient technique to detect this phenomenon. A passive islanding detection algorithm is proposed for all types of DGs by varying and analyzing the DC-link voltage for voltage source converter in the photovoltaic inverter. The proposed algorithm is applied on the low and medium voltage scales. Furthermore, a comparison for applying the proposed technique with resistance load on the two scales is presented. In addition, the proposed technique for anti-islanding protection is performed and compared with a lot of techniques such as underfrequency, overfrequency, and rate of change of frequency according to the detection time of islanding. The simulation results using MATLAB/ SIMULINK platform illustrate the effectiveness of the proposed method.

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