Research On Stability And Interface Algorithm Of Power Hardware-in-the-Loop Simulation System

With the use of large grid interconnection,UHV AC and DC transmission,new energy and new grid-connected equipment,the characteristics and interaction mechanisms in the grid have huge changes,and a large number of experiments and research are necessary.However,it is costly and risky to build a real grid cluster and study the interaction problem of the grid.The power hardware-in-the-loop(PHIL)simulation technology combines the advantages of real-time digital simulation and physical simulation to effectively simulate the operating characteristics and interaction characteristics of new devices in complex condition.It has numerous applications in the power simulation analysis field.In the PHIL system,the real physical system is replaced by a digital discrete model,and the virtual power interaction is realized by the interface algorithm and the interface circuit.Therefore,the interaction sequence in time and discretization factors of the interface module may cause changes in the impedance characteristics of the system which resulting in stability of the PHIL system and reducing the PHIL system conditions can be simulated.Therefore,this thesis studies the modeling and stability of the power hardware-in-the-loop simulation system.Then an interface algorithm to improve system stability and accuracy is proposed.The main research contents are as follows:Firstly,the existing composition and structure of PHIL system are introduced.The related principles of digital-analog hybrid simulation system are summarized.The principles and characteristics of the most common interface algorithms are summarized.Also the stability of the PHIL system is compared and analyzed based on the continuous domain modeling method.Then,in order to reflect the characteristics of digital discrete model and the sampling and holding characteristics of physical signals,a general discrete domain modeling method for PHIL system is proposed to compensate for the precision deviation of continuous domain modeling.On this basis,the stability boundary calculation method of PHIL system based on D-segmentation is proposed.The effects of system impedance parameters and simulation step size in the stability of PHIL system are analyzed in detail.The variation of the instability boundary of the PHIL system under different simulation steps and impedance matching conditions is discussed.It is verified that the delay and discretization will lead to high frequency instability of the PHIL system,and the PHIL system shrinks than the stable boundary of the real system.Then,a parallel virtual impedance power interface algorithm based on discrete domain design is proposed to overcome stable boundary shrinkage problem for PHIL system.Based on the stability evaluation index of stable boundary expansion coefficient,the influence of parallel virtual impedance on the stability boundary of PHIL system is quantitatively analyzed under wide-range impedance conditions.Based on the voltage/current error coefficient system accuracy evaluation index,the improved effect of parallel virtual impedance on the system simulation accuracy under the conditions of fundamental wave,harmonics and different simulation steps is quantitatively analyzed.Finally,the power hardware-in-the-loop simulation system was built by OPRT OP5600+OP5607 RT-LAB real-time simulation system and Spitzenberger&Spies(SP&S)four-quadrant linear power amplifier.The effects of system impedance parameters and simulation step size on the PHIL system are verified by experiments.The accuracy of the above discrete domain model and stability boundary and the effectiveness and feasibility of the proposed parallel virtual impedance algorithm are verified.The accuracy of the above discrete domain model and stability boundary,the validity and feasibility of the proposed parallel virtual impedance algorithm are verified.