Research On Inductive Power Quality Controller And Its Key Technologies

Aiming at the harmonic pollution problem brought by high-power rectification system and the requirement of high-quality power supply for sensitive load,a new inductive power quality control scheme combining inductive filtering technology and active filtering technology is constructed.It includes an inductive active filter system that can realize harmonic current and harmonic flux suppression,and an inductive hybrid unified power quality controller that combines harmonic suppression and voltage sag compensation.The thesis has carried out a series of in-depth research on the operating mechanism and common key technologies of the inductive power quality controller.The main research contents and related achievements include the following:(1)In view of the fact that the traditional filter can not eliminate the adverse effects of harmonics on the transformer,the inductive filtering device can not dynamically control the harmonics,the design of the zero harmonic impedance is difficult,an inductive active filtering system(IAFS)is proposed.The electromagnetic analysis model of the system topology is established based on multi-winding transformer theory and circuit topology to reveal its unique filtering mechanism.The mathematical model of active power filter is established,and the closed-loop control scheme and equivalent output impedance expression are given.Further,the impedance matching method is used to analyze the influence of the impedance ratio of the filter winding impedance and the active power filter output impedance on the reference current,output current and stability of the system.The impedance matching constraint is extracted to eliminate the adverse effect.The theoretical analysis and system performance are verified by simulation and experiment.The simulation and experimental results show the correctness and feasibility of the proposed IAFS;(2)Aiming at the problem that the synchronous rotating frame phase lock loop can not accurately lock the phase under non-ideal voltage conditions,a frequency adaptive phase lock loop with integrated sliding Goertzel discrete Fourier transform(SGDFT)filter is proposed.The non-ideal component in the voltage is suppressed by the fundamental positive sequence separator based on SGDFT filter.At the same time,the Lagrange interpolation method is used to correct the number of sampling points,so as to reduce the filtering error when the sampling point is not an integer value.Further,by adding a reference angular frequency update loop,the phase lock loop tracking speed is accelerated and the accuracy of detection is ensured.The comparison experiments with MCCF-PLL,DSOGI-PLL,PMAF-PLL and GDSC-PLL show that the proposed phase lock loop have obvious advantages in accuracy and adjustment time;(3)In view of the problem that the vector PI controller can not guarantee the control precision when the voltage frequency changes,and the existing frequency division control harmonic detection can not directly extract the 6n harmonic,the frequency adaptive current division control system including frequency adaptive vector PI time-frequency current control and the matching 6n harmonic detection method is proposed.The time domain controller designed acooring to the singular perturbation theory is to improve system response speed.The frequency-adaptive vector PI controller changes the discretization parameters of the controller in real time according to the current tracking error to eliminate the steady-state error introduced by the frequency fluctuation.Further,a method of directly extracting 6n harmonics is proposed,which is used together with controllers tuned to the 6n harmonics to make the frequency division control more precise and the system stability better.The proposed control system is verified by simulation,the simulation results show that the system can achieve better compensation effect when the frequency changes,and its response speed is also improved to some extent.(4)In order to meet the demand of high-quality power supply for sensitive load,based on the inductive active filter system,an inductive hybrid unified power quality controller(IHUPQC)capable of simultaneously treating harmonic pollution and voltage sag is proposed.The single-phase equivalent circuit model of the system is established,and the compensation principle of voltage sag is analyzed.The mathematical model and control strategy of the system are studied separately.On this basis,three operating modes of inductive hybrid unified power quality controller are proposed,the power flow characteristics are analyzed,and the reference signals of are also derived.Combined with the operating characteristics of the three modes,the voltage compensation capability,overall capacity and reactive power compensation capability of each mode are analyzed,and the applicable situations of the three modes are discussed.The system simulation model under different operating modes is established to verify the correctness and feasibility of the proposed system.