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.

scholarly journals POWER SYNCHRONIZATION CONTROL OF VSC-HVDC TRANSMISSION FOR WEAK AC SYSTEM

2013 ◽  
pp. 221-225
Author(s):  
SEENA. K. R ◽  
SINDHU.T. K
Keyword(s):  
Control Method ◽  
Short Circuit ◽  
Vector Current ◽  
Current Control ◽  
Voltage Source ◽  
Synchronization Control ◽  
Voltage Source Converter ◽  
Hvdc Transmission ◽  
Ac Systems ◽  
Weak Ac System

In this paper voltage source converter based HVDC transmission system is used for connecting two ac systems. The control method used is power synchronization control. This method is different from other control methods and it uses the internal synchronization mechanism in ac systems. It is applied for all grid connected VSC’s especially for HVDC application. This control method gives strong voltage support to a weak ac system. It shows that the proposed control allows 0.86 p.u power to be transferred from a system with short circuit ratio of 1.2 to a system with an SCR of 1.The result is compared with the vector current control for the same ac system where it can transfer only 0.4 p.u. The simulations in MATLAB/Simulink are done to demonstrate the system and observe the system behavior under three phase AC faults.

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 Operation Zone Analysis of the Voltage Source Converter Based on the Influence of Different Grid Strengths

Symmetry ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 153
Author(s):  
Wenning Wang ◽  
Kejun Li ◽  
Kaiqi Sun ◽  
Jianjian Wang
Keyword(s):  
Renewable Energy ◽  
Control Strategies ◽  
Short Circuit ◽  
Vector Current ◽  
Current Control ◽  
Voltage Source ◽  
Synchronization Control ◽  
Voltage Source Converter ◽  
Operating Stability ◽  
The Stability

With the increasing penetration of renewable energy into the power system, the voltage source converter (VSC) for integrating renewable energy has become the most common device in the electric network. However, the operating stability of the VSC is strongly dependent on its operating control strategy, which is also highly related to the strength of the AC system. Choosing the control strategy of VSC for different strengths of AC systems becomes an essential issue for maintaining the symmetry between high proportion of renewable energy integration and stable operation of AC system. In order to obtain the operation zones of the control strategies of the VSC under different strengths of AC system, in this paper, the two common VSC control strategies, vector current control (VCC) and power synchronization control (PSC), are compared. Firstly, the principle of VCC and PSC are introduced. Then, based on the short circuit ratio (SCR) and the power limit calculation under steady-state conditions of the VSC, the operation zones of the vector current control and power synchronization control are proposed. Finally, a medium voltage modular multilevel converter (MMC) system was built in PSCAD/EMTDC and the proposed operation zones of the VCC and PSC were tested by changing the SCR of the modified IEEE 33 bus system and analyzed via the critical short circuit ratio (CSCR) analysis, the small-signal stability analysis, and transient stability analysis. The results indicate that, as the SCR decreases, the VSC based on VCC is gradually worked into unstable conditions, while the stability of VSC based on PSC gradually increases. The analysis results provide a criterion for the converter operation strategy change that could significantly improve the operating stability of the VSC in the power system and realize the symmetry of the stability of the converter and the change of the strength of the AC system.

Control Strategy for Voltage Source Converter-Based HVDC System under Unbalanced Voltage Conditions

2013 ◽  
Vol 437 ◽  
pp. 629-633 ◽  
Author(s):  
Ming Guang Zhang ◽  
Diao Bing Wang ◽  
Zhong Kuan Zhang
Keyword(s):  
Control Strategy ◽  
Vector Current ◽  
Response Speed ◽  
Simulation Software ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Hvdc System ◽  
Dual Vector ◽  
Current Controller ◽  
Unbalanced Voltage

The mathematical model of voltage source converter-based flexible DC transmission system (VSC-HVDC) and traditional fault control strategy are comprehensively analyzed. The proportional resonant controller in the traditional dual vector current controller is proposed to simplify the structure of traditional inner current controller. The proposed method improves the response speed and control accuracy of the control system. According to the output voltage distortion caused by the DC voltage ripple, the PWM with amplitude-adjustable carrier is adopted, and according to the DC side voltage rise the power setting value is adjusted. Finally, the control strategy is verified by the electromagnetic transient simulation software PSCAD/EMTDC, the simulation results show it can effectively restrain the fault overvoltage, improve the operation ability of the system.

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 Reliability Assessment of a Multi-State HVDC System by Combining Markov and Matrix-Based Methods

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3097
Author(s):  
Roberto Benato ◽  
Antonio Chiarelli ◽  
Sebastian Dambone Sessa
Keyword(s):  
Current System ◽  
Estimation Method ◽  
Reliability Estimation ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Hvdc System ◽  
Critical Elements ◽  
The Matrix ◽  
The Impact

The purpose of this paper is to highlight that, in order to assess the availability of different HVDC cable transmission systems, a more detailed characterization of the cable management significantly affects the availability estimation since the cable represents one of the most critical elements of such systems. The analyzed case study consists of a multi-terminal direct current system based on both line commutated converter and voltage source converter technologies in different configurations, whose availability is computed for different transmitted power capacities. For these analyses, the matrix-based reliability estimation method is exploited together with the Monte Carlo approach and the Markov state space one. This paper shows how reliability analysis requires a deep knowledge of the real installation conditions. The impact of these conditions on the reliability evaluation and the involved benefits are also presented.

Real power regulation design for multi-terminal VSC-HVDC systems

2013 ◽  
Vol 3 (2) ◽  
Author(s):  
Guo-Jie Li ◽  
Si-Ye Ruan ◽  
Tek Lie
Keyword(s):  
Control Strategy ◽  
Control Mode ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Real Power ◽  
The Real ◽  
Hvdc System ◽  
High Voltage Direct Current ◽  
Power Regulation ◽  
Regulation Functions

AbstractA multi-terminal voltage-source-converter (VSC) based high voltage direct current (HVDC) system is concerned for its flexibility and reliability. In this study, a control strategy for multiple VSCs is proposed to auto-share the real power variation without changing control mode, which is based on “dc voltage droop” power regulation functions. With the proposed power regulation design, the multiple VSCs automatically share the real power change and the VSC-HVDC system is stable even under loss of any one converter while there is no overloading for any individual converter. Simulation results show that it is effective to balance real power for power disturbance and thus improves operation reliability for the multi-terminal VSC-HVDC system by the proposed control strategy.

scholarly journals Fault Ride through Capability Augmentation of a DFIG-Based Wind Integrated VSC-HVDC System with Non-Superconducting Fault Current Limiter

2019 ◽  
Vol 11 (5) ◽  
pp. 1232 ◽  
Author(s):  
Md Alam ◽  
Mohammad Abido ◽  
Alaa Hussein ◽  
Ibrahim El-Amin
Keyword(s):  
Control Strategy ◽  
Reactive Power ◽  
Current Control ◽  
Control Mode ◽  
Voltage Source ◽  
Fault Current ◽  
Fault Current Limiter ◽  
Hvdc System ◽  
Fault Ride Through ◽  
Current Limiter

This paper proposes a non-superconducting bridge-type fault current limiter (BFCL) as a potential solution to the fault problems of doubly fed induction generator (DFIG) integrated voltage source converter high-voltage DC (VSC-HVDC) transmission systems. As the VSC-HVDC and DFIG systems are vulnerable to AC/DC faults, a BFCL controller is developed to insert sizeable impedance during the inception of system disturbances. In the proposed control scheme, constant capacitor voltage is maintained by the stator VSC (SVSC) controller, while current extraction or injection is achieved by rotor VSC (RVSC) controller. Current control mode-based active and reactive power controllers for an HVDC system are developed. Balanced and different unbalanced faults are applied in the system to show the effectiveness of the proposed BFCL solution. A DFIG wind-based VSC-HVDC system, BFCL, and their controllers are implemented in a real time digital simulator (RTDS). The performance of the proposed BFCL control strategy in DFIG-based VSC-HVDC system is compared with a series dynamic braking resistor (SDBR). Comparative RTDS implementation results show that the proposed BFCL control strategy is very efficient in improving system fault ride through (FRT) capability and outperforms SDBR in all cases considered.

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