Research On A Novel Electric Spring With LCL Passive Damper

To cope with the challenges of resources,environment and climate,the world is striving to boost renewable energy,but large scales of distributed renewable energies will bring difficulties to efficient consumption,power system safe operation,and so on.In 2012,a fast and automatic demand response technology based on Electric Spring(ES)was proposed,whose function of stabilizing grid voltage,harmonic suppression and power balancing has been verified.Because ES is beneficial to reduce energy storage,improve power system regulation ability,and promote the further development of renewable energy,it has received widespread attention.Most of the ES researches are based on the topology of a series connection with non-critical loads,but this kind series ES has some defects,such as limited compensation ability and poor performance for suppressing voltage under pure reactive power mode.Therefore,based on the summary of series ES,a new ES with LCL passive damper(LCL-ES)is proposed.Different from the series one,LCL-ES takes the non-critical load as the capacitor paralleled passive damper for LCL filter,which not only overcomes the large power loss,but also expands the compensation range,improves the voltage regulation performance,and can adjust the power characteristics to adapt to different situations.The purpose of this paper is to explore new ES topology,and the first application of such passive damper,developing ES based demand response,and renewable energy.The main contents of this paper are as follows1.The basic theory and topologies of ES are introduced.And the general structure of existing ES is given together with analysis of power characteristics and grid-side voltage range.2.LCL-ES,the novel ES,is presented.The working principle and compensation characteristics of LCL-ES are analyzed in detail and compared with series ES.And the system modeling,control strategy and key parameters design are carried out,then the simulation verification for voltage stabilization and harmonic compensation is done.3.PV-LCL-ES,a distributed PV generation system based on LCL-ES,is proposed.The system can simultaneously achieve maximum power tracking and constant grid-connected power.The power characteristics of PV-LCL-ES are analyzed in detail,and compared with series ES,and then the system modeling,control strategy design and simulation verification are carried out.4.Based on the hardware-in-loop experimental platform,the experimental verifications for LCL-ES and PV-LCL-ES are carried out under different conditions.