| Medium-frequency induction heart furnace based on power electronic technology has become one of the most important load in power system. Due to increasing the capacity of intermediate frequency furnace, harmonic problems more and more serious in the process of power rectifier inverter, which has become the hidden trouble of the safe and stable operation of power grid and also bring many difficulties for industry expansion reporting for work.The effect of power grid and the research of suppression measures which is coused by mediate-frequency furnace load is important issue needed to study in the future. The traditional passive filter will resonance point drift and its harmonic amplification coefficient radical change,harmonic amplification coefficient radical changes when the system frequency fluctuations or change of harmonic branch capacitance and inductance parameters due to the rise and fall of temperature or other reasons.Filter branch may become into harmonic amplifier.This not only harm the filter itself,but also endangers other electrical equipment security in power grid, even disturb the normal safe operation of power grid.This peper study the influence of medium-frequency expansion to power grid by simulation and analyze the effect to restrain the harmonics of different filter circuit. At last, harmonic suppression measures are given according to the prediction of harmonic power.First of all, this peper establish the mediate-frequency furnace model controlled by double closed-loop PWM based on PSCAD simulation software. Setting up six pulse rectifier model according to the 0.35 tonnage mediate- frequency furnace operatiing in the actual line and comparing the simulation results with those of the measured data verify the feasibility and accuracy of model. Secondly, it simulate and analyse harmonic influence on the access point and other nodes in power grid of mediate-frequency furnace load changing. It make simulation to predict harmonic content of each key nodes under the two types of expansion which provide the basis for controlling harmonic content.Then,it analyse harmonic suppression effect of different passive filter circuit and given a passive filter circuit structure to suppress harmonic current amplification verifing the effect of harmonic suppression by the simulation. Finally, it put forward harmonic collaborative governance(setting point on high side, governing distributed on the low voltage side) of power network. |
