Study On Hamilton Energy Function Method And Its Application In Power System Stability Control

Power system is a typical high-dimensional nonlinear dynamic system. The variouscharacteristics of the complex dynamical behavior therein have not been fully grasped.The stability of the power system has been one of the essential research topics for a longtime. With the implementation of the Ultra-High Voltage planning in China, the scale ofthe interconnected grid becomes increasingly large, therefore it is unbearable when theinstability accident occurred in power system. However, the frequent blackouts in NorthAmerica, Brazil, India and other places over the past decade always remind us to pay moreattention on power system stability problems. The transient stability analysis based onenergy function method is a successful application of the nonlinear theory in powersystem, which is able to quantitatively evaluate the stability and is particularly suitable forfast online stability assessment. Along with the time-domain simulation method, these twomethods are powerful tools for power system stability analysis.The ultimate purpose of stability analysis of power system is stabilization control. Thecurrently available energy function methods are mostly based on simple models. It needsto be further studied on the accuracy of the model, the theoretical depth and the stabilitycontroller design with the Hamilton system theory which can provide as a powerfulmathematical tool. Based on generalized controlled Hamiltonian system theory, thestabilization control and coordinated control of the generator excitation and FACTSdevices in power system considering transfer conductance are investigated in this thesis.Then the periodic solution theory of autonomous Hamilton system is used for theoreticalanalysis of the low frequency oscillation phenomenon in power system. The energyfunction of the AC/DC interconnected power system is used to design the HVDCsupplementary damping controllers that can help to suppress low-frequency oscillation.And then the coordination between HVDC and TCSC damping controllers is studied. Themain research contents and results are summarized as following.Based on the generalized Hamilton system theory, a new system structure with more general form, named pseudo-generalized Hamiltonian system, is proposed. The localLyapunov function of the newly presented system is constructed based on Hamiltonenergy function and the stabilization controller is proposed for asymptotically stability atthe equilibrium point. Then the passivity theory is introduced for designing the robustcontroller with L2disturbance attenuation characteristics. Some theorem, conditions andcriterion for the new system structure are illustrated. The system framework and thecontroller design method are applied to the simplified network model of multi-machinepower system with transfer conductance and generator excitations. A generator excitationcontroller based on energy balance and damping injection is proposed, which has a clearphysical meaning. Then the actual power system considering uncertainties is expressed asthe pseudo-generalized Hamilton system and a robust excitation controller with L2disturbance attenuation criteria is proposed. Numerical experiments verify the correctnessand validity of the two proposed controller design methods.The intrinsic structural characteristics of the generalized Hamiltonian system are usedfor coordinated control of power system generator excitation and FACTS devices. Firstly,for the particular scene of long distance power transmission from isolated large powerplants to load center, TCSC can be installed in transmission lines to strength systemstability. By introducing the virtual control input of the equivalent susceptance, the singlemachine infinite bus system is presented into generalized dissipation Hamilton system.The direct feedback control strategy is presented, aiming to reduce the transient energyand make the system asymptotically stable. The coordination between the excitation andTCSC is directly realized with the internal structure. A typical engineering examplesimulation shows the control strategy is effective. Secondly, based on the simplifiednetwork model of multi-machine power system with SVCs, the pseudo generalizeddissipation Hamilton realization is achieved with the dynamics of SVCs being consideredin time-varying system admittance matrix. The Lyapunov function of the system isconstructed and the robust coordinated control of excitation and SVC is designed via L2disturbance attenuation method. The strategy can be approximately expressed as ameasurable form. A numerical example illustrates the correctness and effectiveness of thecontrol design method. The analysis and control of the low-frequency oscillation in power system are studiedvia Hamilton theory. Firstly, based on the lossless single machine infinite bus powersystem model and a two interconnected power system equivalent model, the autonomousHamiltonian system is realized by constructing Hamiltonian energy function. The periodicsolution theory of autonomous Hamilton system is illustrated and used in analyzing powersystem low frequency oscillation properties. Then, the low-frequency oscillation ofAC-DC interconnected power grid is discussed. Based on the two machine equivalentmodel with inertia center equivalence method, the generalized Hamilton system is realizedby defining the oscillation Hamilton function with the oscillation energy concept. Acontrol strategy aiming to reduce system oscillation energy is proposed which takesadvantage of the HVDC fast power modulation capability to damp low frequencyoscillation. Lastly, the Hamiltonian energy function considering the deviation potentialenergy of TCSC installed in the parallel AC line is constructed. The coordination ofHVDC and TCSC supplementary damping controllers, both for reducing the oscillationenergy of the system, are designed using the internal structure properties to strength theability for damping low-frequency oscillations.