A two-level 24-pulse voltage source converter with fundamental frequency switching for HVDC system

Abstract: A New Voltage Source Converter (VSC) based on neutral clamped three-level circuit is proposed for High Voltage DC (HVDC) system. The proposed VSC is designed in a multipulse configuration. The converter is operated by Fundamental Frequency Switching (FFS). A new control method is developed for achieving all the necessary control aspects of HVDC system such as independent real and reactive power control, bidirectional real and reactive power control. The basic of the control method is varying the pulse width and by keeping the dc link voltage constant. The steady state and dynamic performances of HVDC system interconnecting two different frequencies network are demonstrated for active and reactive power control. Total number of transformers used in this system are reduced to half in comparison with the two-level VSCs for both active and reactive power control. The performance of the HVDC system is improved in terms of reduced harmonics level even at fundamental frequency switching. The harmonic performance of the designed converter is also studied for different value of the dead angle (β), and the optimized range of the dead angle is achieved for varying reactive power requirement. Simulation results are presented for the designed three level multipulse voltage source converters with the proposed control algorithm.

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

Energies ◽

10.3390/en14113097 ◽

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.

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

Open Engineering ◽

10.2478/s13531-012-0064-7 ◽

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.

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Research on Serial VSC-LCC Hybrid HVdc Control Strategy and Filter Design Scheme

Energies ◽

10.3390/en13092260 ◽

2020 ◽

Vol 13 (9) ◽

pp. 2260

Author(s):

Fan Cheng ◽

Lijun Xie ◽

Zhibing Wang

Keyword(s):

Reactive Power ◽

Filter Design ◽

Control Strategies ◽

Short Circuit ◽

Voltage Source ◽

Voltage Source Converter ◽

Level Control ◽

Hvdc System ◽

High Voltage Direct Current ◽

Design Scheme

This paper investigated the characteristics of a novel type of hybrid high voltage direct current (HVdc) converter, which is composed by line commutated converter series with voltage source converter. The system and valve level control strategies are introduced, which can provide ac system voltage support. A novel filter design scheme composed by resonant filers for hybrid HVdc are also proposed, which can decrease the capacity of reactive power compensation equipment without deteriorate harmonic characteristics. The ac voltage of HVdc fluctuation level caused by transmitted power variation will be effectively reduced, with the coordination between filter design scheme and converter control. In addition, the influence of ac grid strength is also analyzed by equivalent source internal impedance represented by short circuit ratio (SCR). Finally, the +800 kV/1600 MW hybrid HVdc system connecting two ac grids under different SCR cases are studied, and the PSCAD/EMTDC simulation results have validated the effectiveness for proposed strategy.

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A Selective Fault Clearing Scheme for a Hybrid VSC-LCC Multi-Terminal HVdc System

Energies ◽

10.3390/en13143554 ◽

2020 ◽

Vol 13 (14) ◽

pp. 3554

Author(s):

Naushath M. Haleem ◽

Athula D. Rajapakse ◽

Aniruddha M. Gole ◽

Ioni T. Fernando

Keyword(s):

High Capacity ◽

Voltage Source ◽

Voltage Source Converter ◽

Circuit Breakers ◽

Hvdc System ◽

Hvdc Transmission ◽

High Voltage Direct Current ◽

Clearing Functions ◽

Transmission Structure ◽

The Impact

A selective fault clearing scheme is proposed for a hybrid voltage source converter (VSC)-line commutated converter (LCC) multi-terminal high voltage direct current (HVdc) transmission structure in which two small capacity VSC stations tap into the main transmission line of a high capacity LCC-HVdc link. The use of dc circuit breakers (dc CBs) on the branches connecting to VSCs at the tapping points is explored to minimize the impact of tapping on the reliability of the main LCC link. This arrangement allows clearing of temporary faults on the main LCC line as usual by force retardation of the LCC rectifier. The faults on the branches connecting to VSC stations can be cleared by blocking insulated gate bipolar transistors (IGBTs) and opening ac circuit breakers (ac CB), without affecting the main line’s performance. A local voltage and current measurement based fault discrimination scheme is developed to identify the faulted sections and pole(s), and trigger appropriate fault recovery functions. This fault discrimination scheme is capable of detecting and discriminating short circuits and high resistances faults in any branch well before 2 ms. For the test grid considered, 6 kA, 2 ms dc CBs can easily facilitate the intended fault clearing functions and maintain the power transfer through healthy pole during single-pole faults.

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