Research On Harmonic Suppression Strategy Of Active Power Filter Based On Long Transmission Line

Recently,the significant increase of electronics devices has resulted in large harmonics flowing into grid,which leads to serious harmonic pollutions in the power system.In addition,due to the interaction between transmission lines impedance and other devices impedance,harmonic resonance tends to occur,especially when it goes through a long transmission line.Then it would cause harmonic amplified dramatically and aggravate the harmonic pollution,even threaten the reliable operation of power grid.To suppress the harmonic voltage and current,this paper researches on the propagation characteristic of harmonics in the radial and complex distribution system.Firstly,this paper theoretically analyzes the reason of harmonic current amplification and deduces the propagation equation of harmonic current based on the distributed parameter model of transmission line.Then,the effect of load capacity on harmonic resonance is studies,and it explores that harmonic voltage and current are prone to resonance when the system operates with no or light load.Conversely,heavy load would mitigate the harmonic resonance.Additionally,the influence of harmonics on power system protection is presented.According to a simulation on IEEE 30 nodes distribution system in MATLAB software,this paper reveals that a number of harmonics can affect the relay operation,especially when the total harmonic distortion(THD)is more than 20%,malfunction of relays tends to occur.To solve the above issues,this paper proposes a harmonic suppression strategy called ?-APF based on active power filters(APF).The proposed control strategy will not only suppress harmonics like other APFs but also attenuates the amplified current due to resonance.According to the comparison of the resistive active power filter(R-APF),a traditional harmonic suppression strategy,the effectiveness of the proposed strategy is demonstrated on the distribution system.Finally,this paper establishes a single-phase cable model based on lumped parameter cascade ? model,and theoretically analyzes the feasibility of this model for experimental verification.The single-phase active power filter experiment platform based on DSP TMS320F28335 is built,and the experiment verifies the effectiveness of the harmonic suppression strategy proposed in this paper.