换流变分接头及直流控制器极限诱导分岔分析

本文研究了直流子系统整流站定电流逆变站定电压控制方式下逆变站换流变变比和熄弧角达到限值时交直流互联系统发生极限诱导分岔的情况.对系统遭遇硬限制时不会发生奇异诱导分岔的原因作了详细的探讨;发现系统发生极限诱导分岔时换流变变比需大于临界值并给出了不同类型极限诱导分岔临界值的计算公式.根据临界值对参数灵敏度的信息,可通过调整参数来消除分岔点以增大稳定域.分析了发电机励磁电压极限对换流变变比临界值及系统稳定域的影响.给出了发生此类极限诱导分岔的机理解释:换流变无功消耗的增加,换流站无功补偿的下降及控制方式的转换导致系统因无功缺乏失稳.

Limit induced bifurcation due to converter transformer tap and DC controller limit

The limit induced bifurcation (LIB) in AC/DC power system caused by converter transformer tap and extinction angle limit under the control mode of constant current in rectifier and constant voltage in inverter is studied in this paper. The reason why the singularity induced bifurcation does not occur while the hard limit encounters is analyzed. The transformer ratio should be larger than a critical value while LIB occurs and the formulas for critical value of LIB in defferent types are derived in this paper. The sensitivities of critical value to parameters are calcaulated, from which some bifurcation points are eliminated and the stable region is augmented. And, the effects of field voltage limit on critical value and stable region are discussed. Finally, a mechanism of limit induced bifurcation is proposed. The increase of reactive power consumed in converter transformer and the decrease of the reactive power compensation in converter AC bus and the transform of control mode result in the system destabilization due to the lack of reactive power.