Subsynchronous oscillation suppression method for direct-drive fan grid-connected system
A technology of subsynchronous oscillation and fan, applied in flexible AC transmission system, reducing/preventing power oscillation, AC network circuit, etc., can solve the problems of weakened grid stability, poor applicability, subsynchronous oscillation, etc., and achieve suppression of subsynchronous oscillation , high applicability in engineering, and clear internal mechanism
Active Publication Date: 2021-06-01
HEFEI UNIV OF TECH +1
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Problems solved by technology
[0003] However, with a variety of new energy generation connected to the grid and power electronic components covering all aspects of the power system, the stability of the power grid is gradually weakened, which increases the risk of subsynchronous oscillation caused by direct drive wind turbines connected to the grid without series compensation devices
In 2015, when a direct-drive wind farm in Xinjiang, my country supplied power to a nearby non-series-compensated AC power grid, it caused a continuous subsynchronous oscillation phenomenon, which led to serious shutdown accidents of steam turbines hundreds of kilometers away along the line due to protection actions, affecting regional grid stability
Although the subsynchronous torsional vibration caused by large steam turbines and the subsynchronous control interaction phenomenon caused by doubly-fed induction fans connected to high-series compensation grids have been extensively studied, in 2015 the subsynchronous It was observed for the first time, and the academic community has not clearly explained the mechanism of this engineering accident
[0004] For wind power grid-connected subsynchronous oscillation suppression problem, there are two commonly used measures, including: 1. Adjust the control coefficient of the converter according to the influence trend of the control coefficient of the converter on the subsynchronous oscillation. However, this will cause the wind turbine converter to The optimal control target cannot be achieved; 2. By introducing a damping control link or a virtual resistance link, but in actual engineering, it will be limited by the controller hardware, and it is difficult to add additional control loops in wind farms that have been built and put into operation
At the same time, these two measures are designed for a single subsynchronous oscillation mode. In fact, the 2015 Xinjiang direct drive wind turbine subsynchronous oscillation accident was detected to have multiple subsynchronous oscillation modes. Therefore, the current suppression measures are not suitable for engineering
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[0079] Take a single wind turbine connected to a large power grid with a voltage level of 30kv as an example:
[0080] Table 1 Parameters of grid-connected system of direct drive fan
[0081]
[0082] 1. Carry out small signal modeling and analysis according to the parameters in Table 1, set SCR to 2, and obtain a group of unstable subsynchronous oscillation modes λ 1,2 =0.825±j222.739, the subsynchronous oscillation mode is shown as negative damping, the corresponding subsynchronous oscillation frequency is 35.45Hz, the normalized participation factor calculation results are as follows Figure 4 shown. From Figure 4 It can be seen that the subsynchronous oscillation mode is affected by the parameter i gd i gq , u gd , u gq Therefore, it can be determined that the subsynchronous oscillation of the direct drive fan is due to the interaction between the grid-side converter and the weak AC grid.
[0083] 2. According to the parameters in Table 1, establish the grid-con...
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The invention discloses a subsynchronous oscillation suppression method for a direct-drive fan grid-connected system; the method comprises the following steps of: 1, establishing a full-system mathematical model for connecting a direct-drive fan power generation system into a weak alternating-current power grid, and establishing a small-signal model after linearization; 2, performing characteristic root calculation based on a small signal model, judging a subsynchronous oscillation mode, calculating a participation factor of the subsynchronous oscillation mode, obtaining a participation degree of each state variable on the subsynchronous oscillation mode, and determining a component influencing subsynchronous oscillation; and 3, building a direct-drive fan grid-connected system simulation model based on Matlab / Simulink simulation software, and adding a phase-shifting transformer at a PCC point. According to the invention, interaction between the grid-side converter and the weak AC power grid can be isolated from the source, so that subsynchronous oscillation is suppressed.
Description
technical field [0001] The invention belongs to the technical field of direct-drive fans, and in particular relates to a subsynchronous oscillation suppression method of a direct-drive fan grid-connected system. Background technique [0002] With the promotion of new energy power generation in our country, the installed capacity of wind power generation is increasing year by year. Among them, the direct drive fan has the advantages of easy maintenance, good reliability and high efficiency because it has no gearbox and excitation control system. widely used. [0003] However, as a variety of new energy sources are connected to the grid and power electronic components cover all aspects of the power system, the stability of the power grid is gradually weakened, which increases the risk of subsynchronous oscillation caused by direct drive wind turbines connected to the grid without series compensation devices. In 2015, when a direct-drive wind farm in Xinjiang, my country suppl...
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IPC IPC(8): H02J3/24H02J3/38H02J3/06
CPCH02J3/241H02J3/38H02J3/06H02J2203/20H02J2300/28Y02E40/10
Inventor 韩平平王希陆中来崔晓丹吴家龙王欢汪宗强
Owner HEFEI UNIV OF TECH