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Algorithm of Qingdao used generator asynchronous damping coefficient. The example shows that the equivalent asynchronous damping coefficient obtained by the algorithm can accurately describe the effect of the damping winding on the stability of the power system. Qingdao used generator recycling / sale
In the past, when people were engaged in power system stability analysis and research or controller design, in order to save computing memory and avoid Weishu disaster, etc., the power system was often simplified and reduced order. The common practice is to ignore the effect of the damping windings on some generator sets and consider them according to a simplified model to achieve the purpose of order reduction. It is hypothesized that during the low frequency oscillation of the power system, the current induced in the damping winding is still small enough to be ignored, so the damping winding can be completely ignored in the system model.
Generally, the higher the model order of a used generator set, the more detailed and true the description of the used generator set is, but the more computer memory is used, the slower the analysis and calculation speed is. Therefore, a sub-transient potential change model with a fixed effect of the reduced-order model of the generator is used as the original model, and the transient potential change model without the generator's damping winding is used as the reduced-order model to study the algorithm of equivalent asynchronous damping coefficient .
If the damping strength of a used generator set is sensitive to the dominant oscillation mode or unstable oscillation mode of the power system, simply ignoring the damping winding of the unit and abandoning the asynchronous damping effect of the unit may judge a stable power system as Unstable. The conclusion of environmental stability is forcing people to take measures to improve stability, thus causing unnecessary economic losses. In view of this situation, this paper uses the eigenvalue and sensitivity analysis techniques to give an equivalent asynchronous damping coefficient algorithm that maintains the real part of the eigenvalue of the sensitive oscillation mode before and after the reduction of the generator. The corresponding example is obtained through an example. in conclusion.
The secondary transient potential of the second-hand generator that takes into account the damping winding is the sum of the other one. The incremental differential equation of the slip of the generator set can be obtained as follows, where is the mechanical damping coefficient of the unit, and the meaning of other symbols. This can be obtained in the form of the full power system linearized differential equation 2 force 2, where 4 is a coefficient matrix containing parameters such as and 7.
In order to reduce the order of matrix 4, considering only the changes in the transient electric potential of the generator axis, the incremental differential equation of the slip of the generator set can be obtained as follows, where is the comprehensive damping coefficient of the generator set. In the same way, the linear electric differential equation of the whole power system can be obtained as follows, where 1 is a coefficient matrix including parameters such as,, and so on. For the comprehensive damping coefficient of the generator set, the following relationship is established, and the equivalent asynchronous damping coefficient of the generator damping winding is considered.
Sex research analysis results bring bias.
First obtain the unit's comprehensive damping coefficient, and then subtract the mechanical damping coefficient to obtain the equivalent asynchronous damping coefficient. Because the damping of each unit mainly affects the attenuation of the mechanical oscillation mode of the unit, but has little effect on the oscillation frequency, the equivalent asynchronous damping coefficient can be obtained according to the following calculation steps.
1 Find the eigenvalues and eigenvectors of the unreduced power system according to Equation 2, and then find the sensitivity of the real part of all conjugate complex eigenvalues of the system to the damping coefficient of the unit to be reduced.
Among them, there are common claws for the solid system of the conjugate complex eigenvalues of the first pair. For conjugate complex eigenvalues, the left and right normalized eigenvectors of the first pair of conjugate complex eigenvalues are respectively, 0 is the damping coefficient of the 7th reduced-order unit, and the system has a total of reduced-order units. According to the above negative sensitivity value, the conjugate complex characteristic value corresponding to the first reduced-order unit was identified, and the actual part was recorded as 1. Exhausted.
The initial value of the comprehensive damping coefficient of the reduced-order unit is 1 =, the lean is zero, the number of calculation iterations is set to 0, and the given calculation accuracy is ampere.
Find the eigenvalues and eigenvectors of the reduced-order power system according to Equation 4, and then find the sensitivity of the real part of all conjugate complex eigenvalues of the system to the damping coefficient of the reduced-order unit. The ministry is marked as = to the end.
Value for eigenvalue configuration. Note that the correction amount of the comprehensive damping coefficient of the first reduced-order unit is 4, and if there is 5, the calculation result is output and the iterative calculation is stopped. Otherwise, make left + 1 =, and go to step 3 according to the modified comprehensive damping coefficient correction matrix.
And operating parameters. The node number machine is an equivalent check-in machine of 12 cubits, the node number 42 is five 100 units, the Jia unit is equivalent, and the node 53 is three 100 units, the Jia unit is equivalent. Node 13 is under load. For the sake of brief explanation, all loads are considered with constant impedance, and all generator stator winding resistances and mechanical damping coefficients are taken to be zero. The meaning of the regulating system frame and the parameters are detailed. The No. 1 machine is a fixed excitation; the excitation regulation system of the No. 23 machine is the same, and the parameters are as follows: No. 13 machine is a steam turbine generator. The corresponding single-unit speed control system is the same, the parameters are as follows: No. 1 unit has no intermediate reheating unit. No. 1 equivalent unit. The parameters of the stand-alone generator are relative power angle change curve stabilization measures to prevent the system from breaking down. 5. Obviously, this conclusion will cause Unnecessary economic losses.
Research on Model Reduction and Asynchronous Damping Coefficient of Second-hand Generator
Comparing 42, it can be seen that when the second-order generator reduced-order model is used, the role of the damping winding in the large disturbance process is used.
1 The use of second-order generator reduced-order models should be cautious. As long as the computer hardware conditions permit, the use of reduced-order models should be avoided. When using a reduced-order model of a generator set without damping windings, ignoring the asynchronous damping effect of the damping windings may bring incorrect conclusions to the research or analysis results, which will cause unnecessary economic losses. Using the eigenvalue and its sensitivity analysis technology, an equivalent asynchronous damping coefficient that keeps the real part of the eigenvalue of the sensitive oscillation mode constant before and after the reduction of the generator is given. The calculation example shows that the algorithm can well consider the effect of the damping winding on the stability of the power system.
3.1 Second-order generator model reduction and equivalent asynchronous damping coefficient analysis and calculation situation 1 The generator adopts the formula 1 model, and it can be obtained that the characteristic value of the mechanical oscillation mode corresponding to No. 3 machine is 42 ± 12.7365, and the real parts of the values are all negative. The eigenvalues are not listed, which indicates that the system is stable and stable with small interference in the studied operating mode.
Case 2 The generator adopts the formula 2 reduced order model and does not take into account the asynchronous damping effect. It can be obtained that the characteristic values of the mechanical oscillation mode corresponding to No. 13 machine are unstable at + 1.0919 ± 12.275 respectively. In order to improve the stability of the system, the conclusion forced people to install additional controllers on the relevant generator set, which will eventually cause waste of investment.
Case 3 The second-hand generator adopts the formula 2 reduced-order model and takes into account the asynchronous damping effect of the damping winding. The single-machine equivalent asynchronous damping coefficients of the equivalent machine No. 13 are 1.332, 14.1373, and 7.3569, corresponding to the mechanical oscillations. The eigenvalue of the mode is ± 6.8307. Compared with case 1, it can be seen that using the equivalent asynchronous damping coefficient algorithm proposed in this paper, while adopting the reduced-order model, the asynchronous damping effect of the damping winding is better retained, so as to maintain stability. The correctness of the results of sexual analysis.
It should be noted that the above-mentioned equivalent asynchronous damping coefficient is only obtained for a certain operation mode. If multiple operation modes are involved, multiple equivalent asynchronous damping coefficients corresponding to each operation mode must be calculated and used.
3.2 System simulation calculation under the effect of large disturbance In the above system, the branch between nodes 2 and 3 is composed of 2 lines with the same parameters. When the phase permanent short-circuit fault occurs on the switching line side of node 3 on the return line, 0.128 When the fault is removed, 24 corresponds to the above case 13.5. At the same time as the fault is removed in case 2, the load of No. 1 node 40 and the unit 90 are connected. The vertical axis is the relative power angle, and the unit is. ; The horizontal axis is time, the unit is 3.
It can be known from 2 that the unit in the system can maintain synchronous operation. But sway, and eventually lose synchronization. Under this conclusion, anti-accident Yu Yaonan must be taken. The beginning of dynamic power system.
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