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In this paper, transient stability analysis was focused on Hu-Liao HVDC and AC parallel transmission system. The Hu-Liao HVDC project was introduced; Simulation method and mathematic models of AC and DC systems were stu-died as well as corresponding regulators and controllers. The dynamic performance and the interaction between AC and DC systems du...
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Context 1
... following simulation was done in such an operation: 4 units for DC power sending and DC power 1800 MW. First, to research the features of additional controls for AC/DC hybrid system, simulations were calculated by three cases: that is no additional control, with TCSC forced compensation control and with DC emergency power control. Results were shown in Figure 10. When the additional control of TCSC and DC is activated, the transient stability can be improved but in a limit com- pared with unit tripping under such serious faults. ...
Context 2
... China Electric Power Network System consists of four provincial networks, Liaoning, Jilin, Heilongjiang and East of Inner Mongolia. These networks have been linked with 500 kV transmission lines. And Liaoning electric network is connected with Huabei network by back-to-back HVDC links with a rated capacity of 1500 MW. Figure 1 shows the schematic of Hu-Liao HVDC and AC parallel transmission system. Hulunbeier is rich in coal, large scale power plants are under constructing. Liaoning province is a rapid devel- oping province in economic but much lack of energy. So based on the mutual interest and the idea of optimizing resources, Hu-Liao HVDC project is put into operation. Hu-Liao HVDC transmission is a bipolar 12-pulse HVDC transmission system with rated DC voltage ± 500 kV, rated power 3000 MW, rated current 2500 A. Over- head lines have a length of 908 km long. Yimin converter station locates at east of Inner Mongolia, which is 10 km away from Yimin power plants. It acts normally as a rec- tifier and its AC side rated voltage is 500 kV. Mujia con- verter station is in the center of Liaoning province and connected with Anshan 500 kV station with two 21 km lines. It acts principally as an inverter and its AC side rated voltage is also 500 kV. The Hu-Liao HVDC trans- mission system operation modes include bipolar mode, monopolar ground return mode, monopolar metallic re- turn model and monopolar parallel line ground return model. The HVDC system can be operated under rated voltage and lower voltage. The Hu-Liao HVDC trans- mission normally operates in P mode (constant power control mode). I mode (constant current control mode) can be used as a back-up ...
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Citations
... Due to the freewheeling diodes feeding the DC fault, a strong AC grid current flows through them, potentially damaging the converter valves. Recently, protecting HVDC transmission lines using VSC has proven to be very difficult [13][14][15]. ...
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Segmentation of large AC systems through DC links introduces a new concept
that utilizes the advantages of direct current transmission to improve network
reliability and increase power transfer capacity. Technical literature argues
that the segmentation of the AC network and the introduction of DC links at
these systems connection points bring benefits to system operation, once contingencies
generated on one side of the DC connection point would not be reflected
on the other side of DC connection, thereby reducing the likelihood of
cascading shutdowns and blackouts due to load restraint on transmission lines
and transformers. Amidst this scenario, this paper presents a study of the main
topics regarding the use of this new network segmentation philosophy, bringing
a practical point of view for the use of this concept at the electrical power
system planning. The effect of DC segmentation before a contingency that
would initiate major outages in an adapted electrical system model IEEE-14
bus is studied and simulations have been performed with test HVAC systems
and segmented by HVDC link. The results have been compared, principally in
relation to the voltage bus, reactive power generation, system losses and power
flow at the lines, and demonstrated that this new concept improved the grid
reliability.
Combined with an HVDC transmission system closely, the voltage stability of the system is studied which is based on the sensitivity analysis method. First, a hybrid HVDC system sensitivity calculation method is deduced. On the basis of the method, the active and reactive power sensitivity matrix which is about the voltage amplitude of several AC transmission system important nodes to the DC channel and AC channel is calculated. The sensitivity matrix of the transmission active power and the absorbed reactive power of DC system is calculated under different control modes of DC system, as well as several important nodes voltage sensitivity under different control mode. Integrated the sensitivity indicators above, the operation control mode of AC/DC hybrid transmission system and the measures to improve the voltage stability are studied, providing the technical reference for the safe and stable operation of AC/DC hybrid transmission system.
The characteristics of Korean power systems are large capacity of generation sites and concentrated load in Seoul metropolitan area. According to the national generation facility plan, more generation facilities are needed to be constructed as the electrical demands are forecasted to increase. Moreover, the size of generation sites are expected to increase, too. Therefore transient stability problems become worse and worse. Recently, the necessity of HVDC has been raised to overcome the difficulty of constructing HVAC transmission lines. This paper shows the analysis of transient stability when HVDC transmission system is added to the power system consisting of large generation sites.
