The electricity research institute of the State Academy of Sciences developed an excitation control device for synchronous generator.
The device maintains the terminal voltage of generator at a certain rate, evenly distributes reactive power to generators in parallel operation and keeps up the synchronous operation state of generators in times of trouble with the electrical system.
“Our research team analysed the defects of the previous excitation control device, developed a new one and introduced it to several power stations,” said Jo Chol Jin, section chief of the institute.
According to him, the previous device was greatly affected by frequency variation and failed to sensitively respond to the change in the operation state of various electrical systems. Another defect was that at thermal power plants using high frequency subexciters, the reactive power fluctuated as synchronizing signal measurement error of the subexciters became greater along with the increase in excitation current and subsequently the operation of controlled rectifiers got unsteady.
The research team developed a digitalized and intelligent excitation control device and program for thermal and hydroelectric power stations.
The device helps enhance the stability of operation and manoeuvrability of generator in various ranges of variation in voltage and frequency.
And the team has duplexed the excitation control system and improved the reliability of operation of generator and the stability of electrical system with various troubleshooting and excitation limiting functions.
“In particular, we studied and introduced a methodology for overcoming the effect of the phase short circuit caused by the rise in the inductance of line and load current, which was one of knotty problems in checking and measuring the synchronizing signal of thermal generators using high-frequency subexciters, and for compensating phase lag of control angle and ascertained the effectiveness of the methodology,” said researcher Ri Kwang Jin.
The new excitation control device costs 25 percent less than the previous one and can more than double the control precision and reduce the overshoot to less than ten percent.
“Our complex introduced the new excitation control device for synchronous generator this year and thus increased the lifespan of generating facilities and saved much labour and fund for repairing equipment,” said Ri Myong Sop, senior engineer of the Pukchang Thermal Power Complex.