Research On High Quality Waveform Control And Wireless Parallel Key Technology Of Urban Rail Train Auxiliary Power Supply System

With the unbelievable development of urban rail transit, there is increasing demands for high performance waveform control and reliability of the auxiliary power system. Based on the application and research status at domestic and abroad, the dissertation is focused on high performance waveform control, as well as the wireless parallel technology of auxiliary power supply, deriving the achievements as follows:The dissertation introduces neutral inductor into the conventional3-phase-4-line inverter with split capacitors, and comes up with the improved resonant controller, for the realization of high quality AC output. Based on inductor current reconstruction and PADE approximation, an equivalent model of current loop is built, with the consideration of time-delay in continuous domain. Based on the model, the parameter selection criterion is presented; An improved resonant controller is also brought out, together with the parameter selection criterion of voltage loop with such controller for the first time. The high performance waveform control is realized by the elimination of unbalanced voltage across the split capacitors and the reduction of the fundamental and harmonic impedance. By analyzing the frequency error of the resonant spot under different discretization approaches, the qualitative relationship is derived, which is between frequency error and sampling frequency, and among various resonant frequencies. Due to the analysis above, the optimal selection of discretization approach is presented.For the application of resistive droop approach, which is the key to improving the inherent contradiction of inductive droop approach, between the realization of better balanced current output and the improvement of voltage adjustment capability, the dissertation comes up with a novel active impedance control scheme, with the existence of improved resonant controller. What’s more, revised power calculation approach and full period adaptive control mechanism are adopted for the improvement of the dynamic and steady characteristics of such resistive droop approach. Under different circuit parameters of the paralleled inverters, balanced current output is realized by the increase of active power damping coefficient. With the compensation of system impedance voltage and d-axis voltage, the voltage droop caused by pumping load is eliminated. With the theory of independent active power droop and universal reactive power droop, the unbalanced current output and angular displacement owing to unbalanced3-phase load are eliminated. With resistive virtual impedance technology combines low-pass and high-pass filter, the harmonic impedance in wide frequency range is increased, and the frequency error of the resonant spot under nonlinear load is further eliminated. A random value approach, like the dicing mechanism, is applied during the starting up of paralleled inverters. The probability model of such approach is built, and such approach finally plays a key part in the solution of starting up dilemma.Oriented to the disadvantages of conventional paralleled auxiliary inverters small-signal mode, the dissertation presents a novel small-signal model, in which the paralleled voltage is expressed as the function of parameters of the inverters. With such novel model, it is possible for the consideration of the coupling among all the inverters, hence the accuracy of the model is increased. On such basis, the influence on stability and dynamic performance of paralleled system form the droop coefficient, the power calculation approach, the line impedance and load characteristics are analyzed.For all of the theories, models and approaches above, there are corresponding simulated and experimental results, explaining their applicability and validity.