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Large-scale wind power integration has become the current development trend of the power system. Large-scale wind power integration can change the original structure and characteristics of the system. Thus, it’s necessary to analyse the transient stability of power system which contains wind power, and to study the controlling strategy for improving the transient stability of power system. Based on EEAC, this paper studies the transient stability of the power system which contains wind power system theoretically, proposes the calculation method for accelerating area, decelerating area and margin, and illustrates the impact of wind power integration on the transient stability with power angle curve. Furthermore, this paper studies the modeling and simulation, and the experimental results prove the correctness of the theories.

With the continuous development of China’s modernization, renewable energy power generation will become the main power generation technology in the future, in which the wind power in renewable energy accounts for a large proportion. In recent years, China’s wind power is centralized and large-scale tendency. The large scale grid connected wind power system has changed the original structure and characteristics of the system, so it is necessary to study the transient stability of the power system connected with the wind power, and put forward the control strategy to improve the transient characteristics of the system. The current research on the transient stability of power system with wind farm containing mainly based on equivalent model of wind farm, and through the simulation experiment results [

In this paper, based on EEAC, the transient stability analysis of power system with wind farm is studied. Firstly, the system model is described. We use the classical two order model to describe a generator, ignore the dynamics of prime mover and governor, ignore the dynamics of excitation system [

And:

The transient stability of the system without wind farms is analyzed using EEAC. Next, the wind power system is discussed. We discuss about wind farms based on double-fed Induction generator controlled by modern power electronics technology. Because the wind farm based on asynchronous generator does not consider its own power angle stability, its influence on the transient stability of power system is mainly reflected in the power angle stability of synchronous generator [

The nodal admittance matrix of the power system with wind farms can be expressed as

From (3) we can get:

Or:

The injected current on the node i of the S cluster is:

The increase of current on the node of the S cluster can be converted to the change of the self admittance of the S cluster in the admittance matrix

So, the expression of

Because of the change of self admittance of S cluster, according to Formula (3),

In this formula,

At the same time, considering the mechanical power of the wind farm:

Therefore the total mechanical power of the system is:

In formula (11),

To sum up, considering the wind farm access, formula (1) should be written as:

Then the acceleration area and deceleration area are calculated according to the transient power angle characteristic curve. The transient power angle characteristic curve of wind power is shown in

Formula (13) shows the mechanical power of the system.

The power angle characteristics of the system are different under different operating conditions. Parameters like

The stable equilibrium point of the system is derived:

After the system failure, the stable equilibrium point and unstable equilibrium point:

According to Formula (15), we can get stable equilibrium point after failure

After getting the above work points, according to the fault removal time and the high order Taylor series method, we can get

According to the transient acceleration area

In this part, the transient stability analysis method proposed in 2.1 of wind power system is verified. Based on the above analysis, we make a transient calculation on a certain system and then we make a simulation of the system based on PSASP. The calculated results are compared with the simulation results to judge the correctness of theoretical analysis and evaluate the accuracy of theoretical calculation.

The system is shown in

The fault condition is: three phase grounding short circuit occurs at the first end of AC line when the simulation time is 1.0 second and the fault last for 0.1 second. It can be seen from the simulation experiment that generator1 is among S cluster, and generator 0 is among A cluster.

The nodal admittance matrix can be obtained according to the equivalent network of wind power system, and it is shown as:

Through the network transformation we can get:

The influence of the wind power is regarded as generator1 to increase the injection current. Further, the increase of the injection current of generator 1 can

be regarded as the change of generator1’s self admittance. In this way we can propose that the influence of the wind power can be regarded as the change of generator1’s self admittance. The nodal admittance matrix can be further written as:

Calculate the system shown in

It can be seen from the

Based on the above analysis of the transient stability of power system with wind farm, we found that we can change the system transient acceleration area and deceleration area by changing

SVG can play a role in maintaining the transient process of the stroke and grid voltage level [

Simulation time | Calculation results | Simulation results |
---|---|---|

1.0 second | 69.63˚ | 68.941˚ |

1.05 second | 74.23˚ | 73.195˚ |

1.1 second | 88.02˚ | 86.398˚ |

1.15 second | 104.22˚ | 101.600˚ |

1.2 second | 109.28˚ | 108.860˚ |

1.25 second | 107.21˚ | 106.580˚ |

power support, SVG can improve the genertor output voltage, reduce the degree of electromagnetic power reduction, and the acceleration area can be reduced and the deceleration area is increased, so as to improve the transient stability of the system and improve the transient stability of the system.

The simulation experiment bases on WSCC 3 machine 9 node system. The system is shown in

G1, G2, G4 are synchronous generators, and wind farm is a doubly-fed wind turbine. We conducted two sets of experiments. Experiment 1: Set SVG in Wind farm grid bus; Experiment 2: Do not set SVG in Wind farm grid bus, and other conditions are consistent with experiment 1. Fault condition: a three-phase short-circuit fault occurs in the 55% the between GEN3-230 bus and STNB-230 bus. Fault lasts for 0.25 seconds and we observe the swing of power angle between synchronous generators in transient state. The experimental test curves are shown in

From

This paper proposed a method of analysis and calculation for transient acceleration area and deceleration area in wind power system. Than a simulation experiment was carried out to verify the correctness of the theory. By comparing the simulation results and calculation results, we find that the way to analyse and calculate the wind power system is correct.

On this basis, this paper proposed that using SVG to make reactive power compensation during that fault has positive impact on power system transient characteristics. And the simulation results show the feasibility of the theory.

Lin, R. and Liu, R.Y. (2017) Transient Stability Study of Power System with Large-Scale Wind Farm Integration. Energy and Power Engineering, 9, 552-561. https://doi.org/10.4236/epe.2017.94B061