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 method and apparatus for operating an overvoltage response for an electric machine includes opening a first switching element and a second switching element in response to an overvoltage condition. In the instance that the overvoltage condition persists, the method and apparatus can further open a third switchable element to cease the overvoltage condition.

A method and apparatus for operating an overvoltage response for an electric machine includes opening a first switching element and a second switching element in response to an overvoltage condition. In the instance that the overvoltage condition persists, the method and apparatus can further open a third switchable element to cease the overvoltage condition.

A fault detection method includes, at a generator module having a generator, a rectifier connected to the generator by phase leads, and an inverter connected to the rectifier by a direct current (DC) link, receiving a measurement of voltage applied to the rectifier by the phase leads and receiving a measurement of voltage applied to the inverter by the DC link. DC link voltage balance and sequence voltages are calculated using the measurement of voltage applied to the rectifier by the phase leads and the measurement of voltage applied to the inverter by the DC link. Determination is made using the DC link voltage balance and phase sequence voltages when no fault exists in the generator module. Determination is made that a fault condition exists using the DC link voltage balance and phase sequence voltages when a fault exists in the generator module. Generator modules are also described.

A method for enhancing an over-voltage protection by an over-voltage protection device for a generator is provided. The device includes a high voltage excitation off (HEO) circuit lowering an over-voltage level by an over-voltage lockout control value and a voltage-dependent Ki-Kp (VoKiKp) circuit 30 decreasing an over-voltage generation time by a voltage difference value of a battery voltage. A generator setting voltage is provided to operate the over-voltage and the voltage difference value of the generator 1. The over-voltage level is lowered and the over-voltage generation time is minimized, thereby enhancing the over-voltage protection of the regulator of the generator.

The present disclosure relates to an over-voltage prevention apparatus and method of a distribution line connected with a distributed generator, which sets a range of a dispatched voltage based on a current voltage of a Pole Mounted Automatic Voltage Regulator (PVR) and a voltage at a connection point of a distributed generator to control so that the dispatched voltage is output within the corresponding range.

A fault detection method includes, at a generator module having a generator, a rectifier connected to the generator by phase leads, and an inverter connected to the rectifier by a direct current (DC) link, receiving a measurement of voltage applied to the rectifier by the phase leads and receiving a measurement of voltage applied to the inverter by the DC link. DC link voltage balance and sequence voltages are calculated using the measurement of voltage applied to the rectifier by the phase leads and the measurement of voltage applied to the inverter by the DC link. Determination is made using the DC link voltage balance and phase sequence voltages when no fault exists in the generator module. Determination is made that a fault condition exists using the DC link voltage balance and phase sequence voltages when a fault exists in the generator module. Generator modules are also described.

According to some embodiments, system and methods are provided, comprising an electrical installation; one of a permanent magnet motor and a permanent magnet generator; a circuit operative to provide current to operate one of the motor and the generator; one or more sensors coupled to the electrical installation, wherein the one or more sensors are operative to detect an overcurrent in the circuit and to generate an overcurrent signal; one or more inductors; and an inductance module control operative to: receive the overcurrent signal from the one or more sensors; determine how to insert one or more inductors to reduce an amplitude of the overcurrent; activate the one or more inductors based on the determination; and deactivate the one or more inductors when the overcurrent is not detected. Numerous other aspects are provided.

According to some embodiments, system and methods are provided, comprising an electrical installation; one of a permanent magnet motor and a permanent magnet generator; a circuit operative to provide current to operate one of the motor and the generator; one or more sensors coupled to the electrical installation, wherein the one or more sensors are operative to detect an overcurrent in the circuit and to generate an overcurrent signal; one or more inductors; and an inductance module control operative to: receive the overcurrent signal from the one or more sensors; determine how to insert one or more inductors to reduce an amplitude of the overcurrent; activate the one or more inductors based on the determination; and deactivate the one or more inductors when the overcurrent is not detected. Numerous other aspects are provided.

An arrangement for injection-based ground fault protection handling including a number of stator windings of an electric machine that are connected to a neutral point, a first transformer including at least one primary winding connected to at least one measurement point of the stator windings and at least one secondary winding for measuring an electrical quantity of the machine at the measurement point. There is also a second transformer having a primary winding connected between the neutral point and a ground potential and a secondary winding for connection to a signal generation and detection unit in order to inject a signal into the neutral point and receive a response. The impedance of the second transformer is in the range of the impedance of the machine.