# US 11,121,637 B2 · Power conversion device and power conversion system including a power converter capable of converting between alternating-current (AC) power and direct-current (DC) power > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,121,637 B2 - Document ID: US11121637B2 - Status: Granted - Kind: B2 - Application number: 16/631,196 - Filed: 2017-09-11 - Published: 2020-07-09 - Granted: 2021-09-14 - Earliest claimed: 2017-09-11 - Assignees: Mitsubishi Electric Corporation - Applicants: Mitsubishi Electric Corporation - Inventors: Takeshi Kikuchi; Toshiyuki Fujii; Ryosuke Uda - Web page: https://patentgrep.com/patent/US11121637B2 ## CPC - H02M 1/36: Means for starting or stopping converters - H02M 5/458: using semiconductor devices only - H02M 5/4585: {having a rectifier with controlled elements} - H02M 7/125: {Avoiding or suppressing excessive transient voltages or currents} - H02M 7/217: using semiconductor devices only - H02M 7/219: in a bridge configuration - H02M 7/483: Converters with outputs that each can have more than two voltages levels - H02M 7/4835: {comprising two or more cells, each including a switchable capacitor, the capacitors having a nominal charge voltage which corresponds to a given fraction of the input voltage, and the capacitors being selectively connected in series to determine the instantaneous output voltage} - 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) ## Abstract A power conversion system includes a first power converter and a second power converter which are capable of converting an alternating-current power into a direct-current power or converting a DC power into an AC power. The first power converter is interconnectable to a first AC system via a first AC circuit breaker. The second power converter is interconnectable to a second AC system via a second AC circuit breaker. A first DC terminal of the first power converter and a second DC terminal of the second power converter are connectable. The first power converter begins operation prior to the second power converter. A first control device controls a voltage of the first DC terminal, based on a status of the second power converter sent from a second control device. ## Claims ### Claim 1 A power conversion system, comprising: a first power converter capable of converting an alternating-current (AC) power into a direct-current (DC) power or converting a DC power into an AC power; a second power converter capable of converting an AC power into a DC power or converting a DC power into an AC power; a first control device that controls the first power converter; and a second control device that controls the second power converter, wherein the first power converter is interconnectable to a first AC system via a first AC circuit breaker, the second power converter is interconnectable to a second AC system via a second AC circuit breaker, and a first DC terminal of the first power converter and a second DC terminal of the second power converter are connectable to each other, the first power converter and the second power converter each include a plurality of arms connected in parallel between a positive DC bus and a negative DC bus, the plurality of arms each include a positive arm and a negative arm which are connected in series, the positive arm and the negative arm each include one or more transducer cells which are connected in series, the transducer cells each include: a series body comprising a plurality of semiconductor switching elements connected in series; and a DC capacitor connected in parallel with the series body, the first power converter begins operation prior to the second power converter, the first control device controls a voltage of the first DC terminal, based on a status of the second power converter sent from the second control device, and the first control device and the second device directly communicate with each other. ### Claim 2 (depends on 1) The power conversion system according to claim 1, wherein after the first power converter begins operation, the first control device charges the DC capacitor included in the first power converter and the second power converter by controlling the voltage of the first DC terminal so that the voltage of the first DC terminal increases to a first reference level. ### Claim 3 (depends on 2) The power conversion system according to claim 2, wherein the first reference level is a rated voltage for the first power converter. ### Claim 4 (depends on 2) The power conversion system according to claim 2, wherein, after the voltage of the first DC terminal has increased to the first reference level, the first control device obtains a level of DC voltage that can be output from the second power converter as the status of the second power converter, decreases the voltage of the first DC terminal to the obtained level, after which the second control device starts operation of the second power converter. ### Claim 5 (depends on 4) The power conversion system according to claim 4, wherein the level of DC voltage that can be output from the second power converter is a value obtained based on an average voltage of all capacitors included in the second power converter and a DC voltage modulation rate. ### Claim 6 (depends on 4) The power conversion system according to claim 4, wherein after the second power converter begins operation, the second control device charges the DC capacitor included in the second power converter to a second reference level by controlling a voltage of the second DC terminal so that the voltage of the second DC terminal is increased to the level of DC voltage that can be output from the second power converter. ### Claim 7 (depends on 6) The power conversion system according to claim 6, wherein the second reference level is a rated level of the DC capacitor. ### Claim 8 (depends on 6) The power conversion system according to claim 6, wherein after the DC capacitor included in the second power converter is charged to the second reference level, the first control device increases the voltage of the first DC terminal to a third reference level and the second control device increases the voltage of the second DC terminal to a fourth reference level. ### Claim 9 (depends on 8) The power conversion system according to claim 8, wherein the third reference level is a rated voltage for the first power converter, and the fourth reference level is a rated voltage for the second power converter. ### Claim 10 (depends on 1) The power conversion system according to claim 1, wherein after the first control device turns on the first AC circuit breaker and the second control device turns on the second AC circuit breaker, the first control device causes the first power converter to begin operation once an average voltage of the DC capacitor included in the first power converter has reached an initial charging level. ### Claim 11 (depends on 10) The power conversion system according to claim 10, wherein after the first power converter begins operation, the plurality of semiconductor switching elements included in the first power converter are driven by a voltage stored in the DC capacitor included in the first power converter. ### Claim 12 (depends on 1) The power conversion system according to claim 1, comprising a main control device that controls the first control device and the second control device, wherein, the main control device communicates with the first control device and the second control device. ### Claim 13 (depends on 1) The power conversion system according to claim 1, comprising: a DC transmission line for connecting the first DC terminal and the second DC terminal; a first DC circuit breaker between the first DC terminal and the DC transmission line; and a second DC circuit breaker between the second DC terminal and the DC transmission line. ### Claim 14 (depends on 1) The power conversion system according to claim 1, comprising a main control device that determines the first power converter to be started up first, based on a status of one of the first AC system and the second AC system. ### Claim 15 (depends on 1) The power conversion system according to claim 1, wherein the power conversion system is a Back to Back (BTB) system, and the first DC terminal and the second DC terminal are directly connected to each other. ### Claim 16 (depends on 1) The power conversion system according to claim 1, wherein the power conversion system includes an HVDC system, and the first DC terminal and the second DC terminal are connected to a DC transmission line. ### Claim 17 A power conversion device, comprising: a power converter capable of converting an AC power into a DC power or converting a DC power into an AC power; and a control device that controls the power converter, wherein the power converter is interconnectable to an AC system via an AC circuit breaker, and a DC terminal of the power converter and a DC terminal of another power converter are connectable, the power converter includes a plurality of arms connected in parallel between a positive DC bus and a negative DC bus, the plurality of arms each include a positive arm and a negative arm connected in series, and a point of connection between the positive arm and the negative arm is connected to each phase AC line, the positive arm and the negative arm each include one or more transducer cells connected in series, the transducer cells each include a series body which includes a plurality of semiconductor switching elements connected in series, and a DC capacitor connected in parallel with the series body, the power converter begins operation prior to the other power converter, the control device controls a voltage of the DC terminal of the power converter, based on a status of the other power converter, and the control device and the other power converter directly communicate with each other. ### Claim 18 A power conversion device, comprising: a power converter capable of converting an AC power into a DC power or converting a DC power into an AC power; and a control device that controls the power converter, wherein the power converter is interconnectable to an AC system via an AC circuit breaker, and a DC terminal of the power converter and a DC terminal of another power converter are connectable, the power converter includes a plurality of arms connected in parallel between a positive DC bus and a negative DC bus, the plurality of arms each include a positive arm and a negative arm connected in series, and a point of connection between the positive arm and the negative arm is connected to each phase AC line, the positive arm and the negative arm each include one or more transducer cells connected in series, the transducer cells each include a series body which includes a plurality of semiconductor switching elements connected in series, and a DC capacitor connected in parallel with the series body, wherein the power converter begins operation prior to the other power converter, the control device notifies another control device that controls the other power converter of a status of the power converter, and the control device and the another control device directly communicate with each other.