Abstract
In order to deeply explore the transient stability mechanism of the AC/DC hybrid system, this paper analyzes the rotor angle stability of the two-area AC/DC hybrid system. The system is analyzed after subjecting it to large disturbances in the AC system and for different operating conditions, qualitatively and quantitatively. The influence of factors, such as the AC operating point of the system and the proportion of DC transmission power, have been considered for improving the rotor motion equation. Subsequently, the transient characteristics of the hybrid system are analyzed after being subjected to disturbances. The power angle stability margin index is obtained, based on which the transient characteristics after DC blocking are analyzed, and the coordinated control strategy with the least control cost is proposed. The results are verified using the two-area AC/DC parallel transmission system network model. The study provides the reference for ensuring the security and stability of the hybrid AC/DC power grid.
Highlights
High Voltage Direct Current (HVDC) has become the first choice for long-distance power transmission due to its advantages of low line loss, large transmission capacity, and adjustable power (Huang et al, 2009)
The instability of the system rotor angle caused by the Commutation failure (CF) is one of the main stability problems faced by the AC/DC hybrid system (Geeganage et al, 2015; Gonzalez-Torres et al, 2021)
For the traditional two area AC system, when the three-phase grounding short-circuit fault occurs in the receiving AC system, the impact energy accumulated in the transient process of the system after the fault can be approximately expressed by the acceleration area Sδ0abδcon the power angle characteristic curve, as shown in Figure 5A, the braking energy of the system can be approximately expressed by the deceleration area Sbcd
Summary
High Voltage Direct Current (HVDC) has become the first choice for long-distance power transmission due to its advantages of low line loss, large transmission capacity, and adjustable power (Huang et al, 2009). Siddiqui et al (2016) used the data provided by the phasor measurement units to predict the system’s risk of instability, after a large disturbance They proposed an online emergency control strategy for possible situations. The main contributions of the paper can be summarized as follows: Taking a two-area AC/DC parallel transmission system as the example, to study the influence of AC operating point on the transient rotor angle stability of AC/DC hybrid system. It was proved that in a certain range, the increase of DC power transmission ratio has the opposite effect on the transient rotor angle stability of hybrid system under different working conditions. These research results provide a basis for the distribution of DC transmission power and the adoption of system control strategy under different operation modes of AC/DC hybrid system. Simulation analysis section demonstrates the effectiveness of the theoretical results by the simulation of the two-area IEEE39 network model using an advanced digital power system simulator (ADPSS)
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