31.5
暂态稳定性和系统控制
发电机电压控制对于维持同步发电机和风力轮机的稳定运行至关重要。在旧型号中，由转子驱动的直流发电机将直流电输送到转子的励磁绕组，电力通过滑环和束刷传输。在最新型号中，用到了静态或无刷励磁器。静态励磁器对来自发电机端子的交流电进行整流，然后将直流电直接传输到转子。另一方面，无刷励磁器使用倒置同步发电机，…
在同步发电机中，励磁机向转子的励磁绕组提供直流电能。
早期的模型采用转子驱动的直流发电机作为励磁机，而现代模型则采用静态或无刷励磁机。
静态励磁机将来自发电机端子或母线的交流电整流后供给转子。
无刷励磁机采用倒置的同步发电机，将电枢绕组的交流电通过整流后供给励磁绕组。
1型励磁机具有一个由轴驱动的直流发电机和一个电压调节器，该调节器根据端电压调节励磁电流。
在风力涡轮机中，电压控制随励磁类型的不同而变化。第一类缺乏直接控制，而第二类在阵风期间通过电阻控制维持恒定的功率输出。
3型励磁机控制无功功率，使其保持恒定或随有功功率输出而变化。
框图可直观展示暂态稳定程序中的发电机电压控制。
高增益、快速响应的励磁机在短路期间提高励磁电压，从而改善暂态稳定性。
框图方程用于计算瞬态响应。
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Q1: What is the difference between static and brushless exciters in synchronous generators?
Static exciters rectify AC power from generator terminals or bus and supply DC power directly to the rotor field winding. Brushless exciters use an inverted synchronous generator, rectifying AC power from armature windings via diodes mounted on the rotor, eliminating slip rings and brushes. Both replace older rotor-driven DC generators, improving reliability and reducing maintenance.
Q2: How does a Type 1 exciter control generator terminal voltage?
A Type 1 exciter uses a shaft-driven DC generator with a voltage regulator that measures terminal voltage and compares it to a reference voltage. The voltage error is processed with a gain and time constant, producing a field voltage that adjusts the rotor field current. This feedback mechanism maintains stable terminal voltage output.
Q3: Why do high-gain, fast-responding exciters improve transient stability?
High-gain, fast-responding exciters rapidly increase field voltage during short circuits, strengthening the generator's ability to maintain synchronism. This quick response enhances the simplified synchronous machine model's transient performance by providing immediate reactive power support. Faster exciter response reduces voltage dips and improves overall system stability during disturbances.
Q4: What voltage control methods are used in different wind turbine types?
Type 1 wind turbines use squirrel cage induction machines without direct voltage regulation. Type 2 systems employ wound rotor machines with adjustable external resistance to maintain constant power during wind gusts. Type 3 and Type 4 configurations manage both real and reactive power, providing enhanced control over generator output.
Q5: How do block diagrams represent generator voltage control systems?
Block diagrams visualize the feedback control loop by showing terminal voltage measurement compared against reference voltage, with the error processed through a voltage regulator with gain and time constant parameters. These diagrams compute transient response equations and standardize the representation of exciter and generator dynamics for stability analysis and system design.
Q6: What role does the field winding play in synchronous generator voltage control?
The field winding receives DC power from the exciter, creating the magnetic field that generates terminal voltage. The voltage regulator adjusts field current based on terminal voltage feedback, allowing precise control of generator output. This excitation control is essential for maintaining stable voltage and improving transient stability during system disturbances.
Q7: How does Type 2 wind turbine resistance control maintain power output stability?
Type 2 wind turbines use adjustable external resistance in the rotor circuit of wound rotor induction machines to regulate slip and power output. During wind speed variations, the resistance adjustment maintains consistent power delivery despite changing wind conditions. This resistance control mechanism provides a cost-effective alternative to direct voltage regulation in variable-speed wind turbine systems.