Power System Stability Using Virtual Synchronous Generator For Loading Management

The inertial response plays a vital role in electrical networks to reduce the rate of change of frequency(Ro Co F)following a contingency event.If the inertia has a low or zero value due to a lack of synchronous generators,then the electrical network might experience large undesirable frequency deviations.To overcome this problem,in previous research,mathematical methods have been emerged to enhance the system stability in current source based microgrids.The battery energy storage system embodies the isolated microgrid operates as voltage source and the implementation of the demand side management in which frequency is used as a communication signal.The requirement for inertia frequency response is indicated.In this work,the power electronics methods to emulate virtual inertia have been found,developed and compared.In this research,an overview of existing methods has been presented,which includes the introduction of the principles and comparison between their advantages and disadvantages.Based on those techniques,an additional PID controller has been proposed for the isolated microgrids working as current source.Furthermore,three control schemes to incite inertial responses have been proposed for the microgrids in voltage source type as follows: 1)swing equation method,2)low pass filter,and 3)an adjustable rate limiter.Case studies to test and compare the proposed methods have been established.Accordingly,the corresponding dynamic models of investigated microgrids are created by Simulink graphical blocks.The models allow the study of the voltage source based islanded network in similar conditions as the current source based system,and facilitates their comparison.Therefore,the project includes the comparison between the system behaviors with and without additional inertia control loops in islanded networks with and without rotating mass synchronous generators,respectively.The different responses in the two source types also have been discussed.Inverter dominates the system frequency in microgrid based on voltage source.Compare to the frequency managed by original droop control,the implemented control schemes slow down its changing speed and the system inertial level can be manipulated by adjusting coefficients.Their performance characteristics correspond to the involved extra functions.The PID control in current source-diesel system supports the energy supply and reduces frequency deviation.The proportional equation and the differential equation affect the grid in different ways.Unlike the ideal power reaction in voltage source system,the performance of the current source based islanded microgrid are more improvable and uncontrollable.