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Aiming at the problem of online fault location of large generator stator and the lack of research status of on-line fault location method under multi-mode grounding condition of generator stator, an injection type on-line fault location method under multi-mode grounding condition of large generator stator is proposed. By injecting non-power frequency signal into the secondary side of grounding transformer under multi-mode grounding mode, the voltage and current values of power frequency and non-power frequency returned by the system are fused, and the value of system grounding fault transition resistance is calculated, and the expression of sub grounding transition resistance and fault location is determined. By analyzing the analytic relationship between the system neutral voltage and the fault phase voltage, the stator ground fault location of large generator is solved. The PSCAD/EMTDC simulation model is built to verify that this method can effectively adapt to the demand of real-time online fault location of stator multi-mode grounding mode, with low positioning error, reducing fault finding time and economic loss caused by shutdown.

Aiming at the incompatibility of the existing protection method for the measurement of the ground insulation state under the combined grounding method of the generator stator neutral point (resistance parallel reactor on the secondary side of the grounding transformer), an injection-type monitoring method of insulation state of generator stator to ground in neutral point combined grounding mode is proposed in this paper. By connecting the variable frequency power injecting AC variable frequency signal supplied to the secondary side of the arc suppression coil reactor at the neutral point of the generator, it can search the resonance frequency of stator inductance and capacitance, and calculate the insulation state caused by the insulation damage of stator winding. So it can achieve the purpose that generator stator’s insulation state can be real-time monitored. Through modeling and analysis in PSCAD/EMTDC, this method can be adapted to the measurement of the ground insulation state under the combined grounding mode of the generator stator neutral point and obtain the size of the excessive resistance.

Generator insulation faults account for a high proportion of generator faults. It is difficult to meet the requirements of fast and accurate real-time monitoring of generator stator insulation state. In this paper, the on-line monitoring method of generator stator winding insulation state based on resonance measurement is proposed. By injecting zero-sequence current with constant amplitude and frequency variation into arc suppression coil, the phase angle difference between zero-sequence voltage of stator winding neutral point and injection current is monitored in real time, the resonance frequency of zero-sequence circuit is searched, the capacitance current and leakage resistance current of generator to ground are calculated, and the insulation state of generator stator winding is measured online. Considering the influence of damping resistance and excitation branch of voltage transformer, the accuracy of on-line insulation monitoring is improved. Through PSCAD/EMTDC simulation analysis, the method is not affected by arc suppression coil damping resistance and generator operation mode, which can effectively overcome the interference of excitation branch of voltage transformer to measurement, and meet the requirement of accurate on-line real-time monitoring of generator stator windings. It has certain engineering application value.

In order to solve the limited accuracy of the grounded parameters measurement caused by damping resistance in resonant grounding distribution network, this paper proposes a new resonance measurement method of grounded parameters considering the damping resistance. A characteristic current signal from the constant current signal source with variable frequency is directly injected into the neutral point, and the characteristic voltage signal is measured through the triangular side of the zero-sequence voltage transformer. Constructing the resonant equivalent loops with the damping resistance and establishing the resonance relationship, the formulas for measuring the grounded capacitance and leakage conductance are derived. The method is quick and accurate, eliminating the influence of the damping resistance on measurement.

This paper presents an optimized predictive current control (PCC) for a Halbach array-linear linear vernier permanent magnet machine(H-LVPMM). The stability and robustness of the PCC are affected by parameter variation. Toward this, a modified proportional integral disturbance observer (PIDO) is proposed to estimate the disturbance voltage value caused by parameter error and inject the correspondent observed component into the control system. Experimental results show the validity of the introduced control scheme.

In this paper, an online synchronous generator parameter identification procedure is presented using large disturbance responses and the extended least square estimation algorithm. It was shown that the entire process of signal generation, injection and response measurement can be performed in real time using an industrial personal computer system. In this study, the nonlinear saturated machine model parameters are identified under different operating conditions. Furthermore, from these identified parameters, the parameter sub-models are identified using the least square estimation algorithm under a wide range of operating conditions. This identification technique is carried out on a practical power system to estimate the parameters of a synchronous machine rated at 125 MW. Simulation studies are performed to validate the accuracy of the identified machine model including parameter sub-model.