Subsynchronous oscillation (SSO) with low amplitude that exceeds cumulative fatigue threshold of the generator shaft frequently could significantly reduce the shaft's service life, which is a new SSO problem that ...Subsynchronous oscillation (SSO) with low amplitude that exceeds cumulative fatigue threshold of the generator shaft frequently could significantly reduce the shaft's service life, which is a new SSO problem that emerges in recent years. According to the real recording oscillograph, the basic reason for frequently over-threshold SSO with low amplitude at multi-power plants was analyzed based on Hulunbuir League system. The sensitivities of the electrical damping to the main electrical parameters in the contributing loop of subsynchronous torsional interaction were calculated. Based on the sensitivities, a simulation method was presented, which was used to excite the same oscillation as the actual case by exerting disturbance on the firing angle. The limitation of wide-band and narrow-band supplementary subsynchronous damping controller (SSDC) for mitigating this kind of SSO was analyzed based on the electromagnetic transient simulation model of Hulunbuir League system. The difference of supplementary excitation damping controller (SEDC) and parallel-form FACTS connected to the generator terminal was compared from the aspects of response time and the ability of damping torque supplying. The analysis indicates that their response time is similar but FACTS has stronger ability of damping torque supplying than SEDC. Time-domain simulation method was used to compare the mitigation effects of SEDC, static var compensator (SVC) and static synchronous compensator (STATCOM). Considering the mitigation effect, the floor space limit of the power plant and so on, STATCOM was considered as the best mitigation measure. A control strategy of cascaded STATCOM for engineering application was presented and the capacity for SSO mitigation as well as output characteristics was analyzed. The analysis indicates that STATCOM using the proposed control strategy has better mitigation effect and output characteristics with smaller capacity.展开更多
A novel chromatic dispersion(CD) monitoring technique based on asynchronous amplitude sampling(AAS) is proposed for a higher modulation format and higher rate system.The dispersion and other impairment factors can be ...A novel chromatic dispersion(CD) monitoring technique based on asynchronous amplitude sampling(AAS) is proposed for a higher modulation format and higher rate system.The dispersion and other impairment factors can be separated with the definition of monitoring parameter M.A 400 Gbit/s 256 quadrature amplitude modulation(QAM)system is built using Optisystem 13.0 beta software.Simulations of CD monitoring technique for different bandwidths of sampling Gaussian filter,optical signal to noise ratios(OSNRs) and duty cycles are investigated,and the tolerance is also discussed.Simulation results show that the method can be less affected by noise,and a higher accuracy of 600 ps/(nm.km) can be achieved.The technique supports a wide range of data traffic and enhances operation flexibility of optical networks.展开更多
In order to further improve the carrier synchronization estimation range and accuracy at low signal-to-noise ratio(SNR), this paper proposes a code-aided carrier synchronization algorithm based on improved nonbinary l...In order to further improve the carrier synchronization estimation range and accuracy at low signal-to-noise ratio(SNR), this paper proposes a code-aided carrier synchronization algorithm based on improved nonbinary low-density parity-check(NB-LDPC) codes to study the polarization-division-multiplexing coherent optical orthogonal frequency division multiplexing(PDM-CO-OFDM) system performance in the cases of quadrature phase shift keying(QPSK) and 16 quadrature amplitude modulation(16-QAM) modes. The simulation results indicate that this algorithm can enlarge frequency and phase offset estimation ranges and enhance accuracy of the system greatly, and the bit error rate(BER) performance of the system is improved effectively compared with that of the system employing traditional NB-LDPC code-aided carrier synchronization algorithm.展开更多
基金supported by the Key Project of the National 12th Five-Year Research Programme of China (Grant No. 2011BAA01B02)the Fundamental Research Funds for the Central Universities of China (Grant No.12QN37)
文摘Subsynchronous oscillation (SSO) with low amplitude that exceeds cumulative fatigue threshold of the generator shaft frequently could significantly reduce the shaft's service life, which is a new SSO problem that emerges in recent years. According to the real recording oscillograph, the basic reason for frequently over-threshold SSO with low amplitude at multi-power plants was analyzed based on Hulunbuir League system. The sensitivities of the electrical damping to the main electrical parameters in the contributing loop of subsynchronous torsional interaction were calculated. Based on the sensitivities, a simulation method was presented, which was used to excite the same oscillation as the actual case by exerting disturbance on the firing angle. The limitation of wide-band and narrow-band supplementary subsynchronous damping controller (SSDC) for mitigating this kind of SSO was analyzed based on the electromagnetic transient simulation model of Hulunbuir League system. The difference of supplementary excitation damping controller (SEDC) and parallel-form FACTS connected to the generator terminal was compared from the aspects of response time and the ability of damping torque supplying. The analysis indicates that their response time is similar but FACTS has stronger ability of damping torque supplying than SEDC. Time-domain simulation method was used to compare the mitigation effects of SEDC, static var compensator (SVC) and static synchronous compensator (STATCOM). Considering the mitigation effect, the floor space limit of the power plant and so on, STATCOM was considered as the best mitigation measure. A control strategy of cascaded STATCOM for engineering application was presented and the capacity for SSO mitigation as well as output characteristics was analyzed. The analysis indicates that STATCOM using the proposed control strategy has better mitigation effect and output characteristics with smaller capacity.
基金supported by the National Natural Science Foundation of China(No.61274121)the Natural Science Foundation of Jiangsu Province(No.BK2012829)the Scientific Research Foundation of Nanjing University of Posts and Telecommunications(No.NY212007)
文摘A novel chromatic dispersion(CD) monitoring technique based on asynchronous amplitude sampling(AAS) is proposed for a higher modulation format and higher rate system.The dispersion and other impairment factors can be separated with the definition of monitoring parameter M.A 400 Gbit/s 256 quadrature amplitude modulation(QAM)system is built using Optisystem 13.0 beta software.Simulations of CD monitoring technique for different bandwidths of sampling Gaussian filter,optical signal to noise ratios(OSNRs) and duty cycles are investigated,and the tolerance is also discussed.Simulation results show that the method can be less affected by noise,and a higher accuracy of 600 ps/(nm.km) can be achieved.The technique supports a wide range of data traffic and enhances operation flexibility of optical networks.
基金supported by the State Key Program of National Natural Science Foundation of China(No.61431009)the Natural Science Foundation of Shandong Province in China(No.ZR2014AM018)the Shandong Tai-shan Scholar Research Fund
文摘In order to further improve the carrier synchronization estimation range and accuracy at low signal-to-noise ratio(SNR), this paper proposes a code-aided carrier synchronization algorithm based on improved nonbinary low-density parity-check(NB-LDPC) codes to study the polarization-division-multiplexing coherent optical orthogonal frequency division multiplexing(PDM-CO-OFDM) system performance in the cases of quadrature phase shift keying(QPSK) and 16 quadrature amplitude modulation(16-QAM) modes. The simulation results indicate that this algorithm can enlarge frequency and phase offset estimation ranges and enhance accuracy of the system greatly, and the bit error rate(BER) performance of the system is improved effectively compared with that of the system employing traditional NB-LDPC code-aided carrier synchronization algorithm.
