Converter Based HVDC Transmission Research Articles

A combined‐constraints‐based optimization methodology aimed at temperature balancing for radial layered encapsulation structure of bridge arm reactor

Bridge arm reactor is widely used in voltage sourced converter based HVDC transmission projects, whose temperature distribution is the critical factor determining its operating life. However, the prevailing methods cannot effectively address the pending problem of excessive hot-spot temperature. In this paper, a radial layered structure is proposed, and each encapsulation is layered according to the ‘Huke curve’, reducing the overall temperature rise and metal consumption of the reactor significantly. Further, a combined-constraints-based optimization (CCBO) methodology is proposed with combined advantages of the isothermal rise method and the equal resistance voltage method. A joint solution model for the electrothermal parameters of multiple encapsulations is established. The optimal parameters combination is obtained through iterations, and the temperature rise distribution tends to be balanced. The calculation example for an 800-kV bridge arm reactor with the radial layered structure shows that the hot spot temperature rise is 33.9% lower than that of the traditional structure, and the metal consumption decreases by 61.5%. Through the CCBO methodology, the temperature difference among encapsulations reduces by 12.5% in comparison with the isothermal rise method. From this work, encapsulations’ temperature rise distribution and their metal consumption become balanced and less, which will improve the reactors’ operation reliability.

A novel approach to estimate fault location in current source converter–based HVDC transmission line by Gaussian process regression

A novel approach to estimate fault location in current source converter–based HVDC transmission line by Gaussian process regression

Stop Control Strategy of Modular Multilevel Converter Based HVDC System

The stop control strategy of modular multilevel converter based HVDC transmission system is proposed. This stop process is divided into stages of energy feedback and energy consumption. The DC voltage controller is coordinated to the used modules per phase when active power is transmitted prior to reactive power, so that the energy is fed back to the AC power grid connected to the converter station which uses the fixed dc voltage controller. In addition, in view of the different forms connected to the grid, specifically when the converter station supplies power for passive network, the passive converter station can take a certain auxiliary trigger strategy to make its maximum energy feedback to the grid. Finally, a simulation system of the MMC-HVDC system is constructed in Matlab/Simulink environment, and simulation results show that the proposed stop strategies are effective.

POWER SYNCHRONIZATION CONTROL OF VSC-HVDC TRANSMISSION FOR 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.

HYBRID HVDC CONVERTERS AND THEIR IMPACT ON POWER SYSTEM DYNAMIC PERFORMANCE

Hybrid converter HVDC transmission is a new hybrid transmission system for connecting two AC systems. Because it uses different converters, this new configuration offers several advantages over conventional HVDC systems. This paper demonstrates the superior performance of hybrid converter based HVDC transmission systems with respect to increased stability and terminal ac voltage control. A control system is developed for the hybrid system and its dynamic performance is investigated. The hybrid system performance with emphasis on commutation failure during severe disturbances and its results is also compared with a conventional HVDC scheme.