Characteristic Analysis And Parameter Setting Of Multi-band Power System Stabilizer

With the rapid growth of installed capacity of power system and demand for electricity,the operation mode and structure of power grid become more and more complex.Although these changes improve the economy,they also increase the possibility of low-frequency oscillation.For a long time,power system stabilizer(PSS)is the most economical and effective measure to suppress low frequency oscillation.In the face of increasingly large and complex power system,traditional PSS only aims at single oscillation mode in the system,and its role is limited.Multi-band power system stabilizers,such as PSS4 B,can effectively suppress multiple low-frequency oscillation modes in the system at the same time,but need to cooperate with effective parameter tuning.Firstly,the performance of PSS4 B is analyzed,which provides a basis for parameter tuning of PSS4 B.The velocity deviation sensor of the input signal is analyzed by frequency domain method;the expression of the parameters of PSS4 B is deduced by setting the central frequency filter as a symmetrical band-pass filter,which reduces the parameters that need to be adjusted eventually;the frequency characteristic curves of PSS4 B in different frequency bands and combinations of different frequency bands are analyzed according to PSS4 B.Frequency characteristic curve can be obtained,which operating frequency band plays the leading role in different frequency bands.The influence of gain and compensation coefficient on the performance of PSS4 B is analyzed by setting four sets of parameters.For the study of PSS4 B parameter tuning,based on GMR/PMT technology and six-order model of synchronous generator,a small interference linearization model is established to form the state space equation of the system.The eigenvalues,damping ratios,eigenvectors,participation factors and electromechanical oscillation modes of the system are obtained by the state equation of the system.According to the oscillation frequency of generator participating in strong correlation oscillation mode,the central frequency of each PSS4 B is set;then the time constant of PSS4 B leadingand lagging link is adjusted by phase compensation method;finally,the optimal gain of each frequency band of PSS4 B is determined by root locus method;considering the random factors of power system under multi-operation mode,the probability theory is introduced and the normal distribution is obtained.Assuming that the random factors of power system under multi-operation mode are analyzed by probability analysis,the probabilistic characteristic roots of system electromechanical oscillation mode are calculated to analyze the influence of PSS4 B on system stability in the process of parameter tuning and parameter coordination.Finally,an example is analyzed on a 24-node system of 8 generators,and 720 operation modes of 8 generators are taken as samples.Based on the performance of PSS4 B and the method of parameter tuning proposed in this paper,the parameters of PSS4 B installed in eight generators are tuned.Under the assumption of normal distribution,the real part and damping ratio of the characteristic roots of the electromechanical oscillation mode of the system satisfy the probability stability.After installing PSS4 B in the whole 8-machine system,the small interference stability of the system has been significantly improved.