Research On Large-capacity Balance Compensation Device Of Cophase Traction Power Supply System

Side caused by the single-phase power frequency used in China’s electrified railway traction power supply system, inevitably have a three-phase power system such as three-phase load imbalance, reactive and harmonic interference, at the same time measures the commutation sequence connection exist, will also affect the electric locomotive speed and heavy duty operation. These problems, the existing solution and can not be very desirable to be addressed.Have produced a large capacity power electronic devices, new power electronic control technology is also constantly being proposed in this context, the use of comprehensive power flow controller as the core device of traction power supply system can solve the above mentioned problem. This paper first introduces the Scott type balance traction transformer with phase traction power supply system on the structure and balance to transform the principle of the power flow controller in the same phase power supply system, and come to power flow controller voltage, current and power conversion between. Then introduced several large-capacity converter topology and how it works, focused on diode-clamp, flying-capactior and cascaded-inverters with separater DC sourees of the three-level converter and its analysis and comparison. Taking into account this study load of electrified railway traction load type, choose a structure based on the diode neutral point clamped three-level two-multiple and four-multiple voltage source converter main circuit of comprehensive power flow controller as the main circuit; then down to calculate and analyze the basic electrical parameters of these two programs; simulation compared three types of instantaneous current separation and the separation of two types of active current, the final selection of the active separation with the mean integrator and current control based on SPWM modulation to the reactive power, harmonic current detecting and generating command current for compensation; three-level inverter there is the midpoint voltage balance problem, this paper proposed the DC bus voltage based on improvement over the midpoint of the voltage feed forward balance approach. The end of this article to a traction substation of the measured data as electrical parameters based on MATLAB/Simulink simulation modeling as a basis to determine the power flow controller performance on the main circuit structure of the above two options under harmonic content, as well as three-phase unbalanced degree of energy indicators, to prove the reasonableness and feasibility of two programs designed main circuit structure parameters and control methods.