变频调速灯泡贯流泵站的起动过渡过程

Startup transient behavior of bulb pump unit with VFD

为了获得变频调速灯泡贯流泵站的起动过渡过程水力特性,分析了变频调速贯流泵机组起动时采用矢量控制变频装置、低速同步起动的基本特点,建立了同步起动的灯泡贯流泵机组过渡过程力矩动态平衡方程;研究了同步电动机电磁转矩随转速变化的数学表达方法,分析了灯泡贯流泵机组阻力矩由水阻力矩、轴承摩擦力矩、电动机风扇阻力矩和转子风阻力矩等构成,并给出了相应的数学表达式,提出了快速闸门及其分流拍门在开启过程中的流量分配与平衡方程式.以南水北调东线工程中淮阴三站为案例,对设计工况下起动过程中的主要电气参量和水力参数进行仿真模拟,起动瞬间的励磁电流达到设计值的0.63倍,当频率为6.5 Hz时机组开始转动,迟滞时间为15 s,从而得到了频率变化规律与快速闸门延迟开启时间的最佳匹配.在设计工况下,当同步电动机转速线性变化从0到125 r/min的历时为100 s时,快速闸门延迟开启的最佳时刻为70 s.

In order to obtain the transient hydraulic characteristics of the bulb pump unit in a pump station with VFD during startup,the essential features of low-speed synchronous startup controlled by VFD were analyzed initially.Then the moment equilibrium equation of the rotor of pump unit was established in the startup transient period.The mathematically expressing approach for the electroma-gnetic torque in the synchronous motor in terms of time was investigated.The resistance moments,inclusive of hydraulic resistance moment,bearing frictional moment and motor cooling fan resistance moment etc,and their mathematical expressions were clarified.Finally,the flow rate allocation and conservation between the rapid-drop gate and flap valve during the transient period were determined.Taking Huaiyin No.3 Pumping Station as a study case,the startup transient process of the pump unit under the design condition was simulated to obtain the primary electrical and hydraulic parameters.In the simulation,the pump started running when the instant exciting current reached 0.63 times its design value and the frequency was about 6.5 Hz,causing a 15 s lag delay.As a result,a best match was obtained between the motor rotational speed frequency and the lag time for opening the rapid-drop gate.At the design condition,when the rotational speed of the synchronous motor is linearly increased from 0 to 125 r/min in 100 s interval,the optimal lag time is 70 s for opening the rapid-drop gate.