Electromechanical Transient Modeling of Line Commutated Converter-Modular Multilevel Converter-Based Hybrid Multi-Terminal High Voltage Direct Current Transmission Systems

Abstract

Abstract:A method for electromechanical modeling of line commutated converter (LCC)-modular multilevel converter (MMC)-based hybrid multi-terminal High Voltage Direct Current Transmission (HVDC) systems for large-scale power system transient stability study is proposed. Firstly, the general idea of modeling the LCC-MMC hybrid multi-terminal HVDC system is presented, then the AC-side and DC-side models of the LCC/MMC are established. Different from the conventional first-order DC-side model of the MMC, an improved second-order DC-side model of the MMC is established. Besides considering the firing angle limit of the LCC, a sequential power flow algorithm is proposed for the initialization of LCC-MMC hybrid multi-terminal HVDC system. Lastly, simulations of small scale and large scale power systems embedded with a three-terminal LCC-MMC hybrid HVDC system are performed on the electromechanical simulation platform PSS/E. It is demonstrated that if the firing angle limit is not considered, the accuracy of the power flow solutions will be greatly affected. Steady state calculation and dynamic simulation show that the developed LCC-MMC hybrid MTDC model is accurate enough for electromechanical transient stability studies of large-scale AC/DC system.

Electromechanical Transient Modeling and Control Strategy of Decentralized Hybrid HVDC Systems

“…The detailed structures of the receiving end LCC model. The DC line model, which can be found in [9], will not be shown in this paper. The detailed structures of the receiving end LCC and the MMC are shown in Figure 2b,c respectively.…”

“…There have been many related studies before. An MMC model considering the dynamic characteristic of the bridge arm inductance is proposed in [9], and this model is adopted in this paper.…”

“…In addition, the LCC and half bridge sub-module MMC hybrid HVDC system is the focus of this paper. Electromechanical transient models and control strategies of the centralized hybrid HVDC system have previously been studied [9,10]. However, as a new HVDC topology, the decentralized hybrid HVDC system needs further study.…”

“…Most studies about the LCC-MMC hybrid HVDC system focus on the electromagnetic transient field [11][12][13], whereas studies on the electromechanical transient field are relatively deficient. Xiao et al [9] proposed an electromechanical transient model of the LCC-MMC hybrid HVDC system, but all converters in a station can only be connected to one AC bus. The electromechanical transient model of a multi-terminal HVDC system is established in [14], but it is not applicable to the LCC-MMC hybrid HVDC system.…”

A Full-bridge Director Switches based Multilevel Converter with DC Fault Blocking Capability and Its Predictive Control Strategy

“…The modular multilevel converter (MMC) has been accepted as a suitable solution for high-voltage and high-power application fields due to several inherent features [1][2][3][4][5][6][7][8]. However, blocking the DC fault current becomes a difficult problem because the anti-parallel diodes are still conducting after the insulated-gate bipolar transistors (IGBTs) of HBSM are turned off [9].…”