scholarly journals An Improved Phase-Locked-Loop Control with Alternative Damping Factors for VSC Connected to Weak AC System

2016 ◽  
Vol 2016 ◽  
pp. 1-13 ◽  
Author(s):  
Bin Yuan ◽  
Jianzhong Xu ◽  
Chengyong Zhao ◽  
Yijia Yuan
Keyword(s):  
Power Transmission ◽  
Negative Impact ◽  
Phase Locked Loop ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Power Transfer ◽  
Small Signal Stability ◽  
Loop Control ◽  
Optimal Damping ◽  
Weak Ac System

The gains of phase-locked-loop (PLL) have significant impacts on the power transfer limits for the voltage source converter (VSC) connected to weak AC system. Therefore, in this paper, an improved PLL control, respectively, with alternative damping factors for rectifier and inverter is proposed. First, it is proved that the impedance angle of AC system has a great impact on the small-signal stability of the VSC system. With the same variation tendency of Thévenin equivalent resistance, the limits of power transmission are changing in opposite trends for rectifier and inverter. Second, the improved PLL with alternative damping factors is proposed based on the participation factor analysis. Third, the optimal damping factors of the improved PLL control for rectifier and inverter are calculated. Simulations and calculations validated the following three conclusions: (1) in rectifying operation, the equivalent system resistance has a negative impact on the stability of the system and this is not the case for inverting operation; (2) adding the alternative damping factors to PLL control shows similar results compared with changing the impedance angle of AC system; (3) the proposed optimal damping factors of PLL can effectively extend the power transfer limits under both rectifier and inverter modes.

scholarly journals The Possibility of Enhanced Power Transfer in a Multi-Terminal Power System through Simultaneous AC–DC Power Transmission

Electronics ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 108
Author(s):  
Shaista Parveen ◽  
Salman Hameed ◽  
Hafizur Rahman ◽  
Khaliqur Rahman ◽  
Mohd Tariq ◽  
...  
Keyword(s):  
Power System ◽  
Power Transmission ◽  
Transmission System ◽  
Simulation Software ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Transmission Network ◽  
Power Transfer ◽  
Dc Power ◽  
Dc Power Transmission

The feasibility of power transfer enhancement, through simultaneous AC–DC power transmission in a two-terminal transmission network, has been proposed earlier by the authors, and the concept is well established. To meet the increase in demand for electricity, a new technique is proposed in this article to increase the use of existing transmission lines in addition to independent control of AC and DC power flow. This paper extends the concept to a three-terminal transmission network by considering a power tapping from the middle of the line. DC is also superimposed in the already existing three-terminal AC transmission system. In the proposed topology, a multi-terminal simultaneous AC–DC system is used, which is integrated with a zig-zag transformer and more than two voltage source converter (VSC) stations. Each terminal may represent an area of the power system. Anyone/two-terminal(s) may act as sending end, whereas the remaining two/one terminal(s) may act as receiving end. Power can flow in either direction through each segment of the transmission system. At sending end, VSC converts a part of AC to DC and injects it into the neutral of the zig-zag transformer. On receiving terminal, DC power is tapped from neutral of zig-zag transformer and fed to VSC for conversion back to AC. The concept is verified in the digital simulation software PSCAD/EMTDC.

scholarly journals Distribution system power quality compensation using a HSeAPF based on SRF and SMC features

2021 ◽  
Author(s):  
Akram Qashou ◽  
Sufian Yousef ◽  
Abdallah A. Smadi ◽  
Amani A. AlOmari
Keyword(s):  
Power Distribution ◽  
Distribution System ◽  
Reactive Power ◽  
Sliding Mode ◽  
Distribution Network ◽  
Harmonic Distortion ◽  
Phase Locked Loop ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Non Linear

AbstractThe purpose of this paper is to describe the design of a Hybrid Series Active Power Filter (HSeAPF) system to improve the quality of power on three-phase power distribution grids. The system controls are comprise of Pulse Width Modulation (PWM) based on the Synchronous Reference Frame (SRF) theory, and supported by Phase Locked Loop (PLL) for generating the switching pulses to control a Voltage Source Converter (VSC). The DC link voltage is controlled by Non-Linear Sliding Mode Control (SMC) for faster response and to ensure that it is maintained at a constant value. When this voltage is compared with Proportional Integral (PI), then the improvements made can be shown. The function of HSeAPF control is to eliminate voltage fluctuations, voltage swell/sag, and prevent voltage/current harmonics are produced by both non-linear loads and small inverters connected to the distribution network. A digital Phase Locked Loop that generates frequencies and an oscillating phase-locked output signal controls the voltage. The results from the simulation indicate that the HSeAPF can effectively suppress the dynamic and harmonic reactive power compensation system. Also, the distribution network has a low Total Harmonic Distortion (< 5%), demonstrating that the designed system is efficient, which is an essential requirement when it comes to the IEEE-519 and IEC 61,000–3-6 standards.

scholarly journals Modeling and Analyzing the Effect of Frequency Variation on Weak Grid-Connected VSC System Stability in DC Voltage Control Timescale

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4458 ◽  
Author(s):  
Yang ◽  
Yuan
Keyword(s):  
Voltage Control ◽  
System Stability ◽  
Voltage Source ◽  
Frequency Variation ◽  
Voltage Source Converter ◽  
Small Signal ◽  
Small Signal Stability ◽  
Dc Voltage ◽  
Weak Grid ◽  
Dc Voltage Control

The effect of frequency variation on system stability becomes crucial when a voltage source converter (VSC) is connected to a weak grid. However, previous studies lack enough mechanism cognitions of this effect, especially on the stability issues in DC voltage control (DVC) timescale (around 100 ms). Hence, this paper presented a thorough analysis of the effect mechanism of frequency variation on the weak grid-connected VSC system stability in a DVC timescale. Firstly, based on instantaneous power theory, a novel method in which the active/reactive powers are calculated with the time-varying frequency of voltage vectors was proposed. This method could intuitively reflect the effect of frequency variation on the active/reactive powers and could also help reduce the system order to a certain extent. Then, a small-signal model was established based on the motion equation concept, to depict the effect of frequency variation on the weak grid-connected VSC system dynamics. Furthermore, an analytical method was utilized to quantify the effect of frequency variation on the system’s small-signal stability. The quantitative analysis considered the interactions between the DC voltage control, the terminal voltage control, phase-locked loop, and the power network. Finally, case studies were conducted, and simulation results supported the analytical analyses.

scholarly journals Research on Operating Characteristics of Two-Terminal Flexible Direct Transmission with Improved Deadbeat Control

2021 ◽  
Vol 256 ◽  
pp. 01043
Author(s):  
Mei Jianchun ◽  
Qian Junxia ◽  
Zhao Shengjie ◽  
Ma Hongjuan ◽  
Song Pengcheng ◽  
...  
Keyword(s):  
Control Strategy ◽  
Operation Mode ◽  
Electricity Consumption ◽  
Transmission System ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Basic Operation ◽  
Deadbeat Control ◽  
Operating Characteristics ◽  
Loop Control

Traditional DC transmission technology has obvious defects in power adjustment speed, loss reduction, protection and control, etc., and it has been unable to meet the diverse needs of electricity consumption. The flexible DC transmission system not only solves the above shortcomings, but also has the advantages of independently controllable power and power supply to passive network. It is widely applied in distributed power generation by new energy, micro grid and other fields. This paper takes the two-terminal flexible DC transmission system as the research object, establishes the mathematical mode of two-terminal flexible DC transmission system, and studies the basic operation mode of the system and the voltage source converter (VSC) control strategy on this basis. Considering the problems of control delay and poor responsiveness of current closed-loop control when the traditional deadbeat control is applied to VSC converters, an improved deadbeat control strategy is proposed to solve the above-mentioned defects by predicting the current sampling at k+2 moment. Finally, the co-simulation is used to verify the correctness and reliability of the above-mentioned method.

scholarly journals Technical and Economic Assessment of VSC-HVDC Transmission Model: A Case Study of South-Western Region in Pakistan

Electronics ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 1305 ◽  
Author(s):  
Mehr Gul ◽  
Nengling Tai ◽  
Wentao Huang ◽  
Muhammad Haroon Nadeem ◽  
Muhammad Ahmad ◽  
...  
Keyword(s):  
Flow Analysis ◽  
Economic Assessment ◽  
Transmission Model ◽  
Voltage Source ◽  
Voltage Source Converter ◽  
Renewable Energy Resources ◽  
Discounted Cash Flow ◽  
Loop Control ◽  
Hvdc Transmission

The southwestern part of Pakistan is still not connected to the national grid, despite its abundance in renewable energy resources. However, this area becomes more important for energy projects due to the development of the deep-sea Gwadar port and the China Pakistan Economic Corridor (CPEC). In this paper, a voltage source converter (VSC) based high voltage DC (HVDC) transmission model is proposed to link this area to the national gird. A two-terminal VSC-HVDC model is used as a case study, in which a two-level converter with standard double-loop control is employed. The proposed model has a capacity of transferring bulk power of 3500 MW at 350 kV from Gwadar to Matiari. Furthermore, the discounted cash flow analysis of VSC-HVDC against the HVAC system shows that the proposed system is economically sustainable. The outcomes of this study reveal that the implementation of this project can bring economic stability and energy security in the southwestern region.

scholarly journals Impacts of MT-HVDC Systems on Enhancing the Power Transmission Capability

2019 ◽  
Vol 10 (1) ◽  
pp. 242 ◽  
Author(s):  
Ali Raza ◽  
Armughan Shakeel ◽  
Ali Altalbe ◽  
Madini O. Alassafi ◽  
Abdul Rehman Yasin
Keyword(s):  
Transmission Lines ◽  
Power Flow ◽  
Optimal Power Flow ◽  
Power Transmission ◽  
Test System ◽  
Voltage Source ◽  
Power Transfer ◽  
High Voltage Direct Current ◽  
Transfer Capability ◽  
Excellent Control

In this paper, improvement in the power transfer capacity of transmission lines (TLs) by utilizing a multi-terminal high voltage direct current (MT-HVDC) grid is discussed. A multi-terminal HVDC grid designed for wind power can be used as an extra transmission path in interconnected systems during low wind conditions, and provides extra dynamic stability and security. This paper deals with the power transfer capacity as well as the small signal (SS) stability assessments in less damped oscillations accompanying inter area modes. Computation of the maximum allowable power transfer capability is assessed via DC optimal power flow-based control architecture, permitting more power transfer with a definite security margin. The test system is assessed with and without the exploitation of MT-HVDC grid. Simulation work is done using a generic computational framework i.e., international council on large electric systems (CIGRE) B4 test bench with a Kundur’s two area system, shows that voltage source converters (VSCs) provide excellent control and flexibility, improving the power transfer capability keeping the system stable.

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