# US 11,309,815 B2 · Control method for operating a synchronous machine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,309,815 B2 - Document ID: US11309815B2 - Status: Granted - Kind: B2 - Application number: 17/274,017 - Filed: 2019-07-29 - Published: 2021-10-07 - Granted: 2022-04-19 - Earliest claimed: 2018-09-06 - Assignees: Indar Electric S.L. - Applicants: Indar Electric S.L. - Inventors: Iker Garmendia Olarreaga; Alexander Galarraga Telleria; Nestor Campo Caballero - Web page: https://patentgrep.com/patent/US11309815B2 ## CPC - H02P 9/102: {for limiting effects of transients} - H02P 9/006: {Means for protecting the generator by using control (control effected upon generator excitation circuit to reduce harmful effects of overloads or transients H02P9/10)} - H02P 9/04: Control effected upon non-electric prime mover and dependent upon electric output value of the generator - H02P 9/105: {for increasing the stability} - H02P 9/302: {Brushless excitation} - H02P 2103/20: of the synchronous type - H02P 2205/05: Torque loop, i.e. comparison of the motor torque with a torque reference - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS ## Abstract The invention related to a control method for operating a synchronous machine, the machine comprising an exciter connected to a synchronous generator and a controller (40) for controlling the machine field excitation. The method comprises the steps of predefining a stable operation torque derivative range within which a stable operation of the machine occurs, performing a torque measuring or calculating for the machine, calculating the derivative of said torque, determining whether the calculated torque derivative is within the predefined stable operation torque derivative range for the machine, and, if the torque derivative is not within the predefined stable operation torque derivative range, modifying the machine field excitation to bring the torque derivative within the predefined stable operation torque derivative range. ## Claims ### Claim 1 A control method for operating a synchronous machine, the machine comprising an exciter connected to a synchronous generator and a controller for controlling a machine field excitation, the method comprising, determining a torque for the machine, calculating a derivative of said torque, determining whether the calculated torque derivative is within a predefined stable operation torque derivative range for the machine, wherein the stable operation torque derivative range is a range within which a stable operation of the machine occurs, and when the torque derivative is not within the predefined stable operation torque derivative range, modifying the machine field excitation to bring the torque derivative within the predefined stable operation torque derivative range. ### Claim 2 (depends on 1) The control method according to claim 1, wherein the torque is determined periodically, the torque derivative being calculated by comparing two torque determinations. ### Claim 3 (depends on 2) The control method according to claim 2, wherein the two torque determinations are two consecutive torque determinations. ### Claim 4 (depends on 1) The control method according to claim 1, wherein said determining the torque for the machine is determined by calculating a torque of the synchronous generator. ### Claim 5 (depends on 1) The control method according to claim 1, wherein said determining the torque for the machine is determined by measuring a torque of the synchronous generator. ### Claim 6 (depends on 5) The control method according to claim 5, wherein said measuring the torque of the synchronous generator is carried out by a torque sensor. ### Claim 7 (depends on 1) The control method according to claim 1, wherein the exciter comprises a rotating part and a stationary part, the exciter rotating part coupled to a power converter having an output which is connected to the synchronous generator, said power converter being controlled by control signals generated by the controller and the machine field excitation being modified by modifying said control signals. ### Claim 8 (depends on 7) The control method according to claim 7, wherein the synchronous generator of the machine comprises a rotating part and a stationary part, the output of the power converter being connected to the synchronous generator rotating part. ### Claim 9 (depends on 7) The control method according to claim 7, wherein the power converter comprises a thyristor power converter. ### Claim 10 (depends on 1) The control method according to claim 1, wherein the machine is couplable to a prime mover via a mechanical shaft, and upon determining that the torque derivative is not within the predefined stable operation torque derivative range, the controller generates a torque reference for the prime mover. ### Claim 11 (depends on 10) The control method according to claim 10, wherein the torque reference is sent to a prime mover governor, and the prime mover governor is configured to control the prime mover according to said torque reference. ### Claim 12 (depends on 1) The control method according to claim 1, wherein the machine further comprises a switching device configured to disconnect the machine from the grid, the controller causing the switching device to operate to disconnect the machine from the grid, upon determining that the machine is going to be damaged. ### Claim 13 A controller for controlling a machine field excitation of a synchronous machine configured to supply power to a grid, the controller comprising: a control circuit; a control signal output configured to connect to a power converter of the synchronous machine; and a torque input configured to receive a torque signal indicating a torque of a synchronous generator of the synchronous machine, wherein the control circuit is configured to: determine a torque for the synchronous machine based on the received torque signal, calculate a derivative of said torque, determine whether the calculated torque derivative is within a predefined stable operation torque derivative range for the synchronous machine, wherein the stable operation torque derivative range is a range within which a stable operation of the synchronous machine occurs, and when the torque derivative is not within the predefined stable operation torque derivative range, output a control signal from the control signal output to modify the machine field excitation to bring the torque derivative within the predefined stable operation torque derivative range. ### Claim 14 (depends on 13) The controller according to claim 13, further comprising a torque reference signal output configured to output a torque reference signal to a control device for controlling a prime mover connected to the synchronous machine upon determining that the torque derivative is not within the predefined stable operation torque derivative range. ### Claim 15 (depends on 13) The controller according to claim 13, further comprising a switch output configured for connection to a switching device configured to disconnect the synchronous machine from the grid, the controller outputting a disconnect signal to the switch output to cause the switching device to operate to disconnect the machine from the grid, upon determining that the synchronous machine is going to be damaged.