اثرات مقاومت دامپینگ سیستم نصب روی ثبات ژنراتور نوع دیسک چرخه بازMHD متصل به خطوط انتقال قدرت

This study is performed as part of the wide research on large scale coal fired MHD generation systems. Faults in the power transmission line give remarkable fluctuations to the MHD generator and to the transmission network. Then, it is required to take countermeasures for stable operation of the generation system. The fluctuations do not converge to a stable state after cutting off the fault line in the transmission line because the commutation failure occurs in the inverter system after the line faults. The effects of installed system dumping resistors (SDR) on the stability of an open cycle disk type MHD generator connected to power transmission lines are numerically studied. Usually the AC SDR is installed in the AC primary grid of the transmission line for system stability. The SDR is used to absorb the output energy of the synchronous generator and to get stability of the power transmission system when faults occur in the transmission line. In this paper, we propose to install the SDR in the DC lines between the MHD generator and the primary side of connected line commutated inverters. We show that the SDR is effective for system stability by a time dependent numerical analysis. This study makes it clear that switching on the applied SDR using the thyristor switches in addition to cutting off the faulted transmission lines is effective to remove the fluctuations of the MHD generation system.

It has been shown that line faults give remarkable influences to the MHD generator and the transmission network and that the control of the inverter is required for stable operation of the generation system [1]. The fluctuations do not converge to a stable state after cutting off the fault lines. It has been shown that control of the inverter angle in addition to cutting off the faulted lines is effective to remove the fluctuations of the MHD system [2] and [3]. In this paper, we propose to install system dumping resistors (SDR) circuits in the MHD generation system connected to the line forced inverters and power transmission lines. We show that the SDR circuits are effective for system stability by a time dependent numerical analysis. The SDR circuits are installed in the DC lines between the MHD output terminal and the DC primary side of the inverter. The model of the power system is made for a large scale disk type MHD generator where the thermal input is 1300 MW and the MHD generator output is 235 MW with two pair loads. The voltage and frequency of the transmission line are 275 kV and 60 Hz, respectively.

In this paper, the authors propose applying the new method of SDR circuits, which is suitable for stabilizing the MHD generation system connected to the power transmission system. Adopting the proposed method installs the SDR circuits in the DC primary side of the inverter system, and the SDR circuits are operated when faults occur in the power transmission system. It has been shown that the faults give remarkable influences to the MHD generator system, but all values of the system become stable when the SDR circuits are operated after the fault. The SDR circuits are effective to reduce damages of the MHD generator and the inverters and to make stable the MHD generation system when the faults occur in the system. In the simulation, the inverter system is reconnected to the power transmission system and the SDR circuits are cut off after that fault is removed. We can think that this simulation step as the reconnection is also the same as the starting operation, which connects the MHD generator to the power transmission line through the inverters. The disk MHD generator needs electric load resistors for starting because some values of the output currents need to generate the required output voltage when the MHD generator is connected to the power line. Then, the SDR circuits for the load resistors for starting can be used also as the stabilizer.