问题 问答题 简答题

发电机快速励磁系统最静态稳定有何影响?方法有哪些?

答案

参考答案:

由于快速励磁系统反映灵敏,调节速度快,对同步发电机遭受小扰动时的就静态稳定有益,因此他提高了发电机的极限功率。但若快速励磁系统的开环放大倍数过大,则发电机会在笑的扰动下就产生自发震荡而失去稳定;相反若把放大倍数正定的过小,则稳定运行时维持发电机极端电压恒定的能力较差,此时因达不到高幅值的功角特性,发电机的静态稳定极限同样降低。

一般提高具有快速励磁系统的发电机静态稳定地方法为:

采用稳定环节,如电力系统稳定器PSS,增加发电机阻尼,这样就可以在高放大倍数下消除自发震荡,从而提高发电机的静态稳定能力。

采用最优励磁控制器,提供适当阻尼,以有效地一致各种低频振荡,从而提高发电机的静态稳定极限。

阅读理解

Music can be a great power (力量) to change people’s lives. Regina del Carmen Sanchez, 14, always believes this. The girl from Kansas City, US, leads a hard life. She lives in a small house with her mom and grandparents. Her mom gets a very low pay.

But it doesn’t stop Sanchez’s love of music. She wrote her first song Keep Your Head Up when she was 12. It described the bad situation(情况) at her home, but it also sent the message of hope: “My house is old and poor, but it beats (胜过) being homeless… Love yourself and never give up. You’ll see a better life if you keep your head up…”

It took Sanchez several months to finish the song. Sometimes during a break in class, when lyrics (歌词) came into her head, “I would have to write them down right then,” she told the local newspaper The Kansas City Star.

Jeremy Lillig was a spokesman for Bright Futures, a charity fund. When he saw the video of the song, he was moved. He shared it through social media (社交媒体). The fund has provided money for poor students in Kansas City.

Now Sanchez often plays the song in public. “I want to help people understand what is happening in the world in an easy way,” she said.

小题1:There are     people in Sanchez’s family.

A.three

B.four

C.five

D.six小题2: What’s true about Keep Your Head Up?  ______________________

A.It was written two years ago.

B.It showed a feeling of hopeless.

C.It described the good situation of a house.

D.It took Sanchez several weeks to write the song.小题3: The word “moved” can be replaced (代替) by   .

A.surprised

B.interested

C.touched

D.excited小题4: The best title of the passage can be    .

A.A girl and her song

B.Poor home is better than being homeless

C.Charity changes the girl’s life

D.Let’s support poor students.

问答题 简答题