Equivalent Modeling For Micro-grid Based On Differential Homology

Micro-grid system is a distributed, short-distance, controllable network, and it contains a lot of special electric power generators and power electronic devices which has fast dynamic response. The power between micro-grid system and great-grid system is permeable. As a result, the traditional modeling method can not resolve all the problems in micro-grid system. Therefore, this dissertation involves a novel method attempting to present an equivalence method for micro-grid system.Coherency equivalence method and mode equivalence method are well applied in the power systems. These two methods mainly fit for synchronous generator system in stead of the micro-grid system containing a large number of new power supplies and power electronics converters. In this paper, ship power system, one of the typical micro-grid systems is emphasized to proposed differential cohomology equivalent modeling theory for micro-grid system.The main contents include:This paper proposed a more complete micro-grid system of differential cohomology equivalent theory, including the definition,the discrimination, the parameters of the small perturbation polymerization method as well as testing algorithm for large perturbations of analytic theory, the parameters of the recognition.This article firstly apply cohomology differential algebraic topology for equivalence. The small perturbation algorithm the approximate simplified parallel converter model and the calculation process is given in detail, with the example of ship power system. To resolve the problem of the equivalent modeling under large disturbance, this dissertation attempts to change the equivalent modeling power electronic circuits into Duffing type nonlinear circuit. The above discussed present between chapter2to chapter5.In chapter2, IEEE34node of wind power is researched firstly to illustrate the coherency method which is widely-used in the power systems and it tips4disadvantages for micro-grid systems. This dissertation spread equivalents algorithm from motor electromechanical transient analysis of the synchronous generators to electromagnetic transient analysis of inverters by multi-scale wavelet packet algorithm. And then it discusses the the differential cohomology mathematical concepts and the physical meaning of the three-phase inverter to figure out coherency equivalents is a special case of the differential cohomology. the effect of differential cohomology algorithm is validated by single-phase variable flow parallel circuit parameters polymerization. Large disturbances in the power system are often serious oscillations or unbalanced three phase voltages. This case can not be directly through the small-signal linearity approximation, so this article attempts to transformed Duffing type nonlinear circuit and gives approximate continuous nonlinear equations his article attempts to transformed Duffing type nonlinear circuit and gives approximate continuous nonlinear equations.In chapter3, EPRI’s power grid with tone equivalents polymerization method first introduced, which is divided into the stepsof the model, busbar polymerization, network aggregation fleet polymerization. The algorithm has been widely applied in the power system modeling. Subsequently, the time-domain differential cohomology polymerization method for the power electronic devices is presented. Refered to the coherency equivalents method, the time-domain differential cohomology polymerization method is divided into5steps of a converter capacitance impedance equivalent polymerization, the the equivalent converter load carried by the power control aspects of the polymerization process, part of the polymerization process of the voltage and current link polymerization process. Equivalent AC and DC examples for shipboard power systems are analyzed in chapter5. Finally, the Duffing nonlinear circuits using harmonic balance and numerical analysis method to obtain the approximate solution, approximate solution is a system parameter contains only expressions into the system parameters and the approximate equivalent.In chapter4, microgrids model identification and calibration method, the method of least squares identification the gradient parameter estimates, as well as the subjective validation methods, these methods can be effective recognition system parameters, extended differential cohomology methods of engineering applications.In chapter5, the large ship power systems, also known as the ship integrated power system is a typical micro-grid system. It is divided into two major AC part and the DC part, AC part contains the traditional power of the synchronous motor also contain asynchronous motor load. Small disturbance and large disturbance case is analyzed. DC part contains a lot of power electronic converters. In this dissertation, the method of polymerization method in chapter3is applied for the equivalence of DC part. And Laboratory test verified the method. By the Duffing nonlinear circuit in chapter3under large disturbance and ship integrated power system example in chapter5under small disturbance, the significance of the differential cohomology are able to carry out the equivalent modeling.