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An approach to suppress low-frequency oscillation in the hybrid multi-Infeed HVDC of mixed H2/H∞ robust-based control theory

Li Congshan, Liu Yan, Li Yikai, He Ping, Fang Yan, Sheng Tingyu

Archives of Electrical Engineering

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2022

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Vol. 71, nr 1

109--124

EN

A hybrid multi-infeed HVDC (HMIDC) system is composed of line-commutated converter-based high-voltage direct current (LCC-HVDC) and voltage-source converterbased high-voltage direct current (VSC-HVDC), whose receiving ends have electrical coupling. To solve the problem of low-frequency oscillation (LFO) caused by insufficient damping in the HMIDC system, according to the multi-objective mixed 𝐻2/𝐻∞ output feedback control theory with regional pole assignment, an additional robust damping controller is designed in this paper, which not only has good robustness, but also has strong adaptability to the change of system operation mode. In the paper, the related oscillation modes and transfer function of the controlled plant are obtained, which are identified by the total least squares estimation of signal parameters via rotary invariance technology (TLS-ESPRIT). In addition, the control-sensitive point (CSP) for suppressing LFO based on the small disturbance test method is determined, which is suitable for determining the installation position of the controller. The results show that the control sensitivity factor of VSC-HVDC is greater than that of LCC-HVDC so that adding an additional damping controller to VSC-HVDC is better than LCC-HVDC in suppressing the LFO of HMIDC. Finally, a hybrid double infeed DC transmission system with three receiving terminals is built on PSCAD/EMTDC where the time-domain simulations are performed to verify the correctness of the CSP selection and the effectiveness of the controller.

2

Research on regional emergency DC power support strategy of VSC-MTDC transmission system

Li Congshan, Sheng Tingyu, Fang Yan, Li Yikai

Archives of Electrical Engineering

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2021

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Vol. 70, nr 1

145--160

EN

In the asynchronous interconnected power grid that is composed of the multiterminal voltage-source converter high voltage direct current (VSC-MTDC) system, the control methods of each converter station and the frequency of the connected AC systemare not the same. When a fault occurs in any place of the asynchronous interconnected system, it will cause the system to have power shortage or surplus, affecting the safe and stable operation of the interconnected power grid. In order to solve the problem of insufficient regional active power reserve, based on the VSC-MTDC asynchronous regional interconnection system and the principle of regional sharing, the dynamic power controller under disturbance conditions is established, and the controller parameters are set to achieve the accuracy of unbalanced power in the disturbance area measuring. Then, according to the degree of the disturbance power, considering the factors that affect the support effect of the converter station, an emergency DC power support (EDCPS) scheme under different power disturbances is formulated to achieve power compensation for the disturbance area. Basedon PSCAD/EMTDC software, the proposed control strategy is simulated. The result showst hat the converter station closer to the disturbance area has a better support effect, and the dynamic active power controller can timely and accurately deliver to the disturbance area when the active power reserve is insufficient.

3

Research on emergency DC power support coordinated control for hybrid multi-infeed HVDC system

Li Congshan, Li Yikai, Guo Jian, He Ping

Archives of Electrical Engineering

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2020

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Vol. 69, nr 1

5--21

EN

Based on the respective characteristics of line-commutated converter highvoltage direct current (LCC-HVDC) and voltage-source converter high voltage direct current (VSC-HVDC), two additional emergency DC power support (EDCPS) controllers are designed, respectively. In addition a coordinated control strategy based on a hybrid multi-infeed HVDC system for EDCPS is proposed. Considering the difference in system recovery between LCC-HVDC and VSC-HVDC in EDCPS, according to the magnitude of the amount of potential power loss, the LCC-HVDC and VSC-HVDC priority issues of boosting power for EDCPS are discussed in detail. Finally, a hybrid three-infeed HVDC that consists of two parallel LCC-HVDCs and one VSC-HVDC that is built in PSCAD/EMTDC are simulated. The effectiveness of the proposed approach is verified based on this hybrid three-infeed HVDC system.