The present disclosure provides a method and a system for quickly determining transient stability of a half-wavelength transmission system. The method includes: obtaining power and a power angle of a feeding-end generator of a half-wavelength transmission system; and determining transient power angle stability and a power angle instability mode of the half-wavelength transmission system by using a constructed index system, where two power angle instability modes, that is, an instability mode 1 and an instability mode 2, are specifically constructed for the half-wavelength transmission system based on an equal area method. Based on the equal area method, the present disclosure constructs two instability modes specific to the half-wavelength transmission system, so as to accurately describe transient power angle characteristics of the half-wavelength transmission system under a severe fault, and characteristics of the two instability modes are significantly different from those of an AC transmission mode.

The disclosure discloses a generator circuit breaker control method based on short-circuit fault current symmetry. The method includes: collecting, by a control device, current on an outlet side of a generator in real time; calculating a transferring current feeding moment based on a current symmetry method when fault current rises to a peak value after a short-circuit fault occurs; correcting the transferring current feeding moment by a correction coefficient; and then calculating a breaker switching moment, thereby realizing precise control on a generator circuit breaker. The method mainly addresses the situation that the existing control method cannot effectively cope with the complexity of the short-circuit fault current on the outlet side of the generator, and fills the blank of the effective method for short-circuit control of the generator circuit breaker.

The disclosure discloses a generator circuit breaker control method based on short-circuit fault current symmetry. The method includes: collecting, by a control device, current on an outlet side of a generator in real time; calculating a transferring current feeding moment based on a current symmetry method when fault current rises to a peak value after a short-circuit fault occurs; correcting the transferring current feeding moment by a correction coefficient; and then calculating a breaker switching moment, thereby realizing precise control on a generator circuit breaker. The method mainly addresses the situation that the existing control method cannot effectively cope with the complexity of the short-circuit fault current on the outlet side of the generator, and fills the blank of the effective method for short-circuit control of the generator circuit breaker.

A system comprises a generator control unit (GCU) configured to control a generator. The system includes a first sensor connected to provide feedback to the GCU for generator control. The first sensor is configured to connect to sense at least one of voltage and/or current in a feeder connecting between the generator and a load. The system also includes a second sensor connected to provide feedback to the GCU for generator control. The second sensor is configured to sense at least one of voltage and/or current in a feeder connecting between the generator and the load. The first and second sensors are configured to connect to the feeder apart from one another with feeder impedance therebetween.

An example electrical power system includes a DC bus connected to a load, a plurality of generators driven by rotation of a common shaft, and a plurality of power converters. Each power converter includes an active rectifier controller that operates a respective active rectifier to rectify AC from a respective one of the generators to DC on the DC bus. A load sharing controller is operable to provide a respective adjustment signal to each respective power converter that is enabled, the respective adjustment signals based on a difference between an average output current across all of the active rectifiers that are enabled, and a particular output current of the respective power converter. Each active rectifier controller is operable to determine a quadrature current value for its associated generator based on its adjustment signal.

Various embodiments include determining an alternating current (AC) voltage and frequency of a supply voltage coupled to a circuit input. The circuit includes a soft starter circuit that is coupled between the circuit input and a first side of an AC motor. A stator winding configuration of the AC motor is determined. A control transformer is configured in response to the AC voltage and frequency, wherein the control transformer is coupled to the circuit input. A jumper device is configured on a second side of the AC motor in response to the stator winding configuration of the AC motor.

A drive train comprising an electric machine including a rotor and a stator, the stator being electrically connected to an alternating grid and having a stator frequency, and a bidirectional system for converting an alternating current into another alternating current. The conversion system is connected between the grid and the rotor, and comprises an ac/dc converter connected to the network, and an inverter connected between the ac/dc converter and the rotor, the inverter and the rotor being interconnected at an intermediate point for each phase of the alternating voltage. The drive train comprises a band-stop filter for a target interval of between 0.6 times the stator frequency and 1.4 times the stator frequency, said band-stop filter being connected between the intermediate points and attenuating the voltage at the intermediate point for the frequencies of the target interval.

A drive train comprising an electric machine including a rotor and a stator, the stator being electrically connected to an alternating grid and having a stator frequency, and a bidirectional system for converting an alternating current into another alternating current. The conversion system is connected between the grid and the rotor, and comprises an ac/dc converter connected to the network, and an inverter connected between the ac/dc converter and the rotor, the inverter and the rotor being interconnected at an intermediate point for each phase of the alternating voltage. The drive train comprises a band-stop filter for a target interval of between 0.6 times the stator frequency and 1.4 times the stator frequency, said band-stop filter being connected between the intermediate points and attenuating the voltage at the intermediate point for the frequencies of the target interval.

The disclosed embodiments include a method to protect a downhole generator from overvoltage. In one embodiment, the method includes determining a speed of an alternator. The method also includes activating overvoltage protection mode if the speed of the alternator is greater than a threshold speed, where activating the overvoltage protection mode includes converting an alternating current measured at the alternator into a first component and a second component of a direct current. Activating the overvoltage protection mode also includes determining a first current threshold based on at least one component of the downhole generator. Activating the overvoltage protection mode also includes shutting down the downhole generator if the first component of the direct current is greater than the first current threshold and decreasing a magnetic flux of the downhole generator if the first component of the direct current is not greater than the first current threshold.

A rectifier includes a rectification MOSFET that performs rectification, a comparator formed by connecting a drain of the rectification MOSFET to a non-inverting input terminal and a source to an inverting input terminal, and a control circuit that performs an on/off control of the rectification MOSFET using an output of the comparator. The control circuit includes a shut-off MOSFET that disconnects a drain of the rectification MOSFET and a non-inverting input terminal of the comparator from each other, and a shut-off circuit that turns off the shut-off MOSFET to electrically disconnect the drain of the rectification MOSFET and the non-inverting input terminal of the comparator from each other when the drain voltage of the rectification MOSFET is equal to or higher than a predetermined first voltage.