In order to improve the behavior of transformer protection that is incomplete at present in distinguishing magnetizing inrush current from fault current , the paper puts forward a kind of new principle of transformer differential protection after analyzing the characteristic of magnetizing inrush and active power consume of transformers . this protection uses differential protection based on positive sequence active power as a criterion to discriminate internal faults from magnetizing inrush , and ratio restraint differential current protection as a signal to touch off the protection 针对当前电力系统中变压器保护由于励磁涌流鉴别理论不完善而导致的误动率相对较高的问题，论文在分析了变压器励磁涌流特性和有功损耗的基础上，提出了用变压器正序有功功率差动作为区别励磁涌流和故障电流的判据，并以成熟的比率制动差流保护作为内外部故障判据的变压器主保护。
Adopt advanced micro processor carry out smart control , and to the inputed tri - phase ac voltage and current signal carry out accurate measurement , through cpu automatically arithmetic processing , the tri - phase ac total active reactive power value and electric energy value can be clear and visual displied by high brightness led digital tube or large screen lcd liquid crystal , tri - phase ac total active power can be simultaneously transferred to standard voltage current signal to transmit output , and have super limit control alarm standard serial communication function etc 采用先进的微处理器进行智能控制，对输入的三相交流电压信号与电流信号进行精确的测量，经过cpu自动运算处理后,由高亮度led数码管或大屏幕lcd液晶清晰直观的显示出三相交流总有功无功功率值和电能值，同时三相交流总有功功率可转换成标准电压电流信号变送输出，并具有超限制报警标准串行通讯等功能。
Adopt advanced microprocessor carry out smart control and to the simultaneous inputed single phase ac voltage and current signal carry out accurate measurement , through cpu automatic count the single phase ac active power value , reactive power value , which is displied clearly and visually by the high brilliance led digital tube or high resolution light column , uper screen display active power and down screen display reactive power , and can select serial communication function 采用先进的微处理器进行智能控制，对同时输入的单相交流电压与电流信号进行精确测量，经过cpu自动计算出单相交流有功功率值，无功功率值。上屏显示有功功率下屏显示无功功率，并可选择串行通讯功能。
Wp - le series intelligent power instrument input and measurement parameter scope include : dc voltage , dc current , ac single phase voltage , single phase current , tri - phase voltage , tri - phase current , single phase active power , single phase reactive power , tri - phase active power , tri - phase reactive power , single phase active electric energy , single phase reactive electric energy , tri - phase reactive electric energy , power factor power frequency and so on Wp le系列智能电力仪表输入及测量电参数范围包括：直流电压直流电流交流单相电压单相电流三相电压三相电流单相有功功率单相无功功率三相有功功率三相无功功率单相有功电能单相无功电能三相有功电能三相无功电能功率因数cos工频频率等。
In this paper , several scheme of vscf is compared firstly , of which gets doubly - fed generating mode . doubly - fed vscf wind power generating system uses a doubly - fed induction generator , which rotate speed can be able to change with wind turbine , and it ensures a constant - frequency output , by controlling the frequency of current input into rotor windings . in vector trans control system , the control of stator active power and the control of stator reactive power can be essentially decoupled , and the former is via torque component and the latter is via exciting component of stator current 本文首先比较了几种变速恒频方案，从中选择了双馈式变速恒频方案；它运用双馈电机的工作原理，允许发电机转速变化，而在电机转子侧接入低频励磁电流，通过控制该电流的频率，保证双馈电机定子输出的频率恒定；再结合矢量控制技术，通过调节转子电流来控制定子电流的转矩分量和励磁分量，相应独立地控制发电机输出的有功功率和无功功率。
The fluctuation of active power , ( pe ) , is used as the measurable key disturbance for destroying stability of generator . at the same time , the nonlinear problem of generator equation will be avoided when the measurable disturbance is used as a feedback in the controller 同步发电机输出有功功率的波动p _ e是危害发电机稳定性的主要因素， p _ e的不确定性具有扰动的本质特性，以p _ e作为可测的反馈扰动变量，将避免发电机方程非线性的难题，并能够简化控制器的设计。
