A Subsynchronous Oscillation Suppression Method for Direct-drive Fan Grid-connected System
A technology of subsynchronous oscillation and wind turbine, applied in flexible AC transmission system, reducing/preventing power oscillation, AC network circuit, etc., can solve the problems of weakening power grid stability, no clear explanation of mechanism, subsynchronous oscillation, etc. The effect of high applicability, suppression of subsynchronous oscillation, and clear internal mechanism
Active Publication Date: 2022-08-05
HEFEI UNIV OF TECH +1
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[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 the grid-connected system of direct-drive fans
[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 exhibits negative damping, and the corresponding subsynchronous oscillation frequency is 35.45Hz. The calculation result of the normalized participation factor is 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 generation of subsynchronous oscillation of the direct-drive fan is due to the interaction between the grid-side converter and the weak AC grid.
[0083] 2. Establish the grid-connected model ...
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The invention discloses a method for suppressing subsynchronous oscillation of a grid-connected system of a direct-drive fan. The steps include: 1. Establishing a system-wide mathematical model of a direct-drive fan power generation system merging into a weak AC power grid, and after linearization, establishing a small signal 2. Calculate the characteristic root based on the small signal model, determine the sub-synchronous oscillation mode, calculate the participation factor of the sub-synchronous oscillation mode, obtain the degree of participation of each state variable in the sub-synchronous oscillation mode, and determine the influence of the sub-synchronous oscillation mode. Synchronous oscillation components; 3. Based on Matlab / Simulink simulation software, the simulation model of the grid-connected system of the direct-drive fan is built, and a phase-shifting transformer is attached at the PCC point. The invention can isolate the interaction between the grid-side converter and the weak AC grid from the source, thereby suppressing the sub-synchronous oscillation.
Description
technical field [0001] The invention belongs to the technical field of direct-drive fans, and in particular relates to a method for suppressing subsynchronous oscillation of a grid-connected system of a direct-drive fan. Background technique [0002] With the promotion of new energy power generation in my country, the installed capacity of wind power generation has increased 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, and has been widely used in wind power generation. widely used. [0003] However, with the integration of various new energy power generation into the grid and power electronic components covering all aspects of the power system, the stability of the power grid is gradually weakened, increasing the risk of subsynchronous oscillation caused by direct-drive fans connected to the grid without series compensation devices. In 2015,...
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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