# US 10,483,865 B2 · Converters for wind turbine generators > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,483,865 B2 - Document ID: US10483865B2 - Status: Granted - Kind: B2 - Application number: 15/030,316 - Filed: 2014-10-14 - Published: 2016-08-18 - Granted: 2019-11-19 - Earliest claimed: 2013-10-18 - Assignees: Vestas Wind Systems A/S - Applicants: Vestas Wind Systems A/S - Inventors: Tusitha Abeyasekera; Duy Duc Doan; Lars Helle; Allan Holm Jørgensen; John Godsk Nielsen; Søren Andersen - Web page: https://patentgrep.com/patent/US10483865B2 ## CPC - H02J 3/381: {Dispersed generators} - F03D 9/255: {connected to electrical distribution networks; Arrangements therefor} - H02H 3/105: {responsive to excess current and fault current to earth} - H02H 7/122: for inverters, i.e. DC/AC converters - H02J 3/28: Arrangements for balancing of the load in networks by storage of energy - H02M 1/12: Arrangements for reducing harmonics from AC input or output - H02M 1/32: Means for protecting converters other than automatic disconnection - H02M 5/42: by static converters - H02M 5/4585: {having a rectifier with controlled elements} - H02M 7/219: in a bridge configuration - H02M 7/493: the static converters being arranged for operation in parallel - H03H 7/0107: {Non-linear filters} - G01R 31/40: Testing power supplies (testing photovoltaic devices H02S50/10) - H02J 2101/28: Wind energy - H02M 1/0077: {Plural converter units whose outputs are connected in series} - H02M 1/123: {Suppression of common mode voltage or current} - H02M 7/23: arranged for operation in parallel {(H02M7/2176 takes precedence)} - Y02E 10/72: Wind turbines with rotation axis in wind direction - Y02E 10/76: Power conversion electric or electronic aspects - Y02E 70/30: Systems combining energy storage with energy generation of non-fossil origin - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY - F03D: WIND MOTORS - H02H: EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS (indicating or signalling undesired working conditions G01R, e.g. G01R31/00, G08B; locating faults along lines G01R31/08; emergency protective devices H01H) - H02M: APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF (transformers H01F; dynamo-electric converters H02K47/00; controlling transformers, reactors or choke coils, control or regulation of electric motors, generators or dynamo-electric converters H02P) - H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P) - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract A wind turbine generator 1 supplies three-phase a.c. current of variable voltage and variable frequency to two pairs of rectifiers 4a, 4b and 4c, 4d which generate respective d.c. outputs connected to positive, negative and neutral d.c. conductors 6, 7, 8. The outputs from each pair of rectifiers are connected together, and the outputs from the two pairs are connected in series to create a high-voltage d.c. output. Inverters 10a, 10b, 10c, 10d then convert the d.c. power to a.c. at a fixed frequency and voltage suitable for connection to the mains grid. To reduce the effect of common-mode noise, a capacitor is connected between the 1 neutral conductor 7 and earth, and a respective filter circuit 30 is connected between each of the a.c. outputs of the inverters 10a, 10b, 10c, 10d and earth. To reduce the effect of voltage surges during lightning, a surge protection device is also connected between the neutral d.c. conductor 7 and earth. Any imbalance in the current in the positive and negative conductors 6, 8 is compensated by detecting the presence of current flowing in the neutral conductor 7. Power supplied to auxiliary circuits from the output of one of the inverters, e.g. 10a, of the wind turbine is measured, and any resulting imbalance between the current in the positive and negative conductors is compensated. In the event of an earth-leakage fault in the conductors connecting the a.c. outputs of the inverters to the grid, when isolated, isolation detection relays 25 are provided. ## Claims ### Claim 1 A system for converting an alternating current (AC) output from a generator of a wind turbine, the system comprising: a first rectifier and a second rectifier of the wind turbine, each rectifier connected to the AC output of the generator and arranged to generate a respective direct current (DC) output, wherein: a positive DC level output from the first rectifier is applied to a first, positive DC conductor; a negative DC level output from the first rectifier is connected together with a positive DC level output from the second rectifier and applied to a second, neutral DC conductor; and a negative DC level output from the second rectifier is applied to a third, negative DC conductor, the first, second, and third DC conductors being arranged to transmit the resulting DC voltages; and a controller configured to, responsive to sensing a presence of current flowing in the second DC conductor, control the rectifiers to balance current flowing in the first DC conductor and the third DC conductor, wherein the current in the second DC conductor is reduced. ### Claim 2 (depends on 1) A system as claimed in claim 1, further comprising: a third rectifier and a fourth rectifier of the wind turbine, each rectifier connected to the AC output of the generator and arranged to generate a respective DC output, wherein the DC output of the third rectifier is connected to the DC output of the first rectifier and the DC output of the fourth rectifier is connected to the DC output of the second rectifier. ### Claim 3 (depends on 1) A system as claimed in claim 1, further comprising: switching elements for selectively disconnecting each rectifier from the AC output of the generator. ### Claim 4 (depends on 1) A system as claimed in claim 1, further comprising: a first inverter configured to convert the DC output of the first rectifier to a first AC output having a predetermined frequency and voltage; and a second inverter configured to convert the DC output of the second rectifier to a second AC output having a predetermined frequency and voltage. ### Claim 5 (depends on 4) A system as claimed in claim 4, further comprising switching elements for selectively disconnecting each inverter from an electrical grid. ### Claim 6 A system for converting an alternating current (AC) output from a generator of a wind turbine, the system comprising: a first rectifier and a second rectifier of the wind turbine, each rectifier connected to the AC output of the generator and arranged to generate a respective direct current (DC) output, wherein: a positive DC level output from the first rectifier is applied to a first, positive DC conductor; a negative DC level output from the first rectifier is connected together with a positive DC level output from the second rectifier and applied to a second, neutral DC conductor; and a negative DC level output from the second rectifier is applied to a third, negative DC conductor, the first, second, and third DC conductors being arranged to transmit the resulting DC voltages; a first inverter configured to convert the DC output of the first rectifier to a first AC output having a predetermined frequency and voltage; a second inverter configured to convert the DC output of the second rectifier to a second AC output having a predetermined frequency and voltage, wherein the first AC output is configured to supply power to auxiliary circuits of the wind turbine such that the power available for delivery from the first AC output to an electrical grid is less than the power available for delivery from the second AC output; and a controller configured to, responsive to a measurement of the power supplied to the auxiliary circuits, control at least one of the first rectifier, the second rectifier, the first inverter, and the second inverter to improve a balance of AC power levels supplied to the electrical grid from the first AC output and the second AC output. ### Claim 7 (depends on 1) A system as claimed in claim 1, further comprising: circuitry defining a low-impedance path between the neutral DC conductor and earth which substantially blocks DC current. ### Claim 8 (depends on 7) A system as claimed in claim 7, wherein the circuitry defining the low-impedance path comprises a capacitor. ### Claim 9 (depends on 1) A system as claimed in claim 1, further comprising a surge protection device connected between the neutral DC conductor and earth. ### Claim 10 (depends on 9) A system as claimed in claim 9, wherein the surge protection device comprises a switching element defining a current path only when the voltage of the neutral DC conductor exceeds a predetermined level. ### Claim 11 A system for converting an alternating current (AC) output from a generator of a wind turbine, the system comprising: a first rectifier and a second rectifier of the wind turbine, each rectifier connected to the AC output of the generator and arranged to generate a respective direct current (DC) output, wherein: a positive DC level output from the first rectifier is applied to a first, positive DC conductor; a negative DC level output from the first rectifier is connected together with a positive DC level output from the second rectifier and applied to a second, neutral DC conductor; and a negative DC level output from the second rectifier is applied to a third, negative DC conductor, the first, second, and third DC conductors being arranged to transmit the resulting DC voltages; a first inverter configured to convert the DC output of the first rectifier to a first AC output having a predetermined frequency and voltage; and a second inverter configured to convert the DC output of the second rectifier to a second AC output having a predetermined frequency and voltage, wherein a respective switched resistance is provided across DC terminals of each of the first rectifier, the second rectifier, the first inverter, and the second inverter, wherein magnitudes of the switched resistances of the first inverter and the second inverter are substantially greater than magnitudes of the switched resistances of the first rectifier and the second rectifier. ### Claim 12 (depends on 4) A system as claimed in claim 4, further comprising a filter circuit connected to the neutral DC conductor. ### Claim 13 (depends on 4) A system as claimed in claim 4, in which circuitry normally connecting the AC outputs of the inverters to an electrical grid is arranged to be isolated from the inverters under predetermined conditions, the system further comprising: a controller configured to, responsive to detecting a short circuit between the circuitry and earth, generate an alarm signal. ### Claim 14 (depends on 1) A system as claimed in claim 1, further comprising: noise-reducing circuitry electrically connected to the second, neutral DC conductor for reducing high-frequency common-mode noise on the second, neutral DC conductor by providing an AC conductive path between the second, neutral DC conductor and earth which substantially blocks the passage of DC current. ### Claim 15 (depends on 14) A system as claimed in claim 14, wherein the noise-reducing circuitry comprises a capacitor connected between the second, neutral DC conductor and earth. ### Claim 16 (depends on 14) A system as claimed in claim 14 further comprising an inverter for converting a DC voltage of a rectifier to an AC output, wherein the noise-reducing circuitry comprises a filter circuit connected between the AC output of the inverter and the second, neutral DC conductor. ### Claim 17 (depends on 1) A system as claimed in claim 1, further comprising: a controller configured to, responsive to sensing a presence of an abnormally high voltage on the second, neutral DC conductor, provide a conductive path between the second, neutral DC conductor and earth. ### Claim 18 (depends on 4) The system of claim 4, wherein the wind turbine comprises a nacelle mounted at the top of a tower, wherein the generator, the first rectifier, and the second rectifier are arranged in the nacelle, and wherein the first inverter and the second inverter are remote from the nacelle. ### Claim 19 (depends on 18) The system of claim 18, wherein the first inverter and the second inverter are arranged in a base of the tower. ### Claim 20 (depends on 19) The system of claim 19, wherein a plurality of transformers coupled with the first AC output and the second AC output are arranged in the base.