# US 2021/0344279 A1 · Multilevel electric power converter > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0344279 A1 - Document ID: US20210344279A1 - Status: Published application - Kind: A1 - Application number: 17/274,317 - Filed: 2019-09-09 - Published: 2021-11-04 - Earliest claimed: 2018-09-07 - Assignees: Socovar S.E.C. - Applicants: Socovar S.E.C. - Inventors: Mohammad SHARIFZADEH; Kamal AL-HADDAD - Web page: https://patentgrep.com/patent/US20210344279A1 ## CPC - H02M 7/4833: {Capacitor voltage balancing} - H02M 1/0095: {Hybrid converter topologies, e.g. NPC mixed with flying capacitor, thyristor converter mixed with MMC or charge pump mixed with buck} - H02M 7/487: Neutral point clamped inverters - H02M 7/5387: in a bridge configuration - H02M 1/325: {with means for allowing continuous operation despite a fault, i.e. fault tolerant converters} - H02M 7/217: using semiconductor devices only - H02M 7/4837: {Flying capacitor converters} - H02M 7/5388: with asymmetrical configuration of switches - H02M 7/5395: by pulse-width modulation - 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 multilevel power converter and method for transforming DC power from a DC source into AC power for an AC load are provided. The converter is composed of a half-bridge inverter, a switching cell, and a controller configured for controlling operation of the half-bridge inverter and the switching cell. The half-bridge inverter and the switching cell are connectable to the DC source and the AC load. The switching cell is composed of first and second pairs of switches forming first and second branches in parallel, first and second capacitors connected in series in a capacitor branch connected between the first and second branches, and a pair of back-to-back connected switches in a third branch, the third branch connected to the capacitor branch and connectable to the AC load. ## Claims ### Claim 1 A multilevel power converter for transforming direct current (DC) power from a DC source to alternating current (AC) power for an AC load or for transforming AC power from an AC source to DC power for a DC load, comprising: a half-bridge inverter connectable to first and second ports of the DC source and to a first port of the AC load; a switching cell connected to the half-bridge inverter and connectable to the DC source, in parallel with the half-bridge inverter, and to a second port of the AC load, the switching cell comprising: a first pair of switches forming a first branch connectable between the first port of the DC source and the second port of the AC load; a second pair of switches forming a second branch connectable between the second port of the DC source and the second port of the AC load, in parallel with the first branch; first and second capacitors connected in series in a capacitor branch, the capacitor branch connected between the first and second branches at first and second points located between the switches of the first and second pairs of switches, respectively; and a pair of back-to-back connected switches in a third branch, the third branch connected to the capacitor branch at a third point located between the first and second capacitors and connectable to the second port of the AC load; and a controller coupled to the half-bridge inverter and to the switching cell and configured for controlling operation of the half-bridge inverter and the switching cell to convert the DC power from the DC source to the AC power for the AC load. ### Claim 2 (depends on 1) The multilevel power converter of claim 1, wherein the switching cell further comprises: at least one additional capacitor connected in the capacitor branch; and at least one additional branch connected to the capacitor branch at a respective additional point located between the at least one additional capacitor and an adjacent capacitor and connectable to the second port of the AC load, the at least one additional branches comprising at least one additional pair of back-to-back connected switches. ### Claim 3 (depends on 2) The multilevel power converter of claim 2, wherein the controller is configured to convert the DC power to the AC power by producing m voltage levels, where m=number of capacitors×4+1, wherein the number of capacitors includes the first and second capacitors and the at least one additional capacitor. ### Claim 4 (depends on 1) The multilevel power converter of claim 1, wherein the switching cell is a first switching cell, further comprising at least one additional switching cell connected in parallel to the half-bridge inverter and to the first switching cell, the at least one additional switching cell being connectable to a second port of the AC load. ### Claim 5 (depends on 4) The multilevel power converter of claim 4, further comprising at least one voltage sensor coupled to the at least one additional switching cell for measuring voltages of capacitors of the at least one additional switching cell. ### Claim 6 (depends on 4) The multilevel power converter of claim 4, wherein the controller is configured to convert the DC power to the AC power by producing at least seventeen voltage levels. ### Claim 7 (depends on 1) The multilevel power converter of claim 1, wherein controlling operation of the switching cell comprises regulating voltages of the first and second capacitors. ### Claim 8 (depends on 7) The multilevel power converter of claim 7, wherein regulating the voltages of the first and second capacitors comprises actively balancing the voltages of the first and second capacitors. ### Claim 9 (depends on 8) The multilevel power converter of claim 8, wherein actively balancing the voltages of the first and second capacitors comprises balancing the voltages of the first and second capacitors to equal values. ### Claim 10 (depends on 9) The multilevel power converter of claim 9, wherein the equal values are of one-quarter of a voltage amplitude of the DC source. ### Claim 11 (depends on 7) The multilevel power converter of claim 7, further comprising a voltage sensor coupled to the switching cell for measuring voltages of the first and second capacitors. ### Claim 12 (depends on 1) The multilevel power converter of claim 1, wherein the controller is configured to convert the DC power to the AC power by producing at least nine voltage levels. ### Claim 13 (depends on 1) The multilevel power converter of claim 1, further comprising an external controller for adjusting the voltage of each capacitors to ⅕ of the DC power in order to produce at least eleven voltage levels. ### Claim 14 (depends on 1) The multilevel power converter of claim 1, wherein a switching frequency of switches composing the half-bridge inverter is lower than a switching frequency of the first and second pairs of switches of the switching cell. ### Claim 15 (depends on 1) The multilevel power converter of claim 1, wherein a rated voltage value of the first and second pairs of switches of the switching cell is lower than a rated voltage value of switches composing the half-bridge inverter. ### Claim 16 A method for transforming direct current (DC) power from a DC source to alternating current (AC) power for an AC load, comprising: obtaining the DC power at a multilevel power converter connected to the DC source and to the AC load, the multilevel power converter comprising a half-bridge inverter, connected to first and second ports of the DC source and to a first port of the AC load, and a switching cell, connected to the first and second ports of the DC source in parallel with the half-bridge inverter and to a second port of the AC load, wherein the switching cell comprises first and second capacitors connected in series and split by a pair of back-to-back connected switches; obtaining measurement values from a sensor indicative of voltages of the first and second capacitors; controlling operation of the half-bridge inverter and the switching cell to convert the DC power from the DC source to the AC power for the AC load based on the voltages of the first and second capacitors by activating at least one of the back-to-back connected switches; and outputting the AC power from the multilevel power converter to the AC load via the first and second ports of the AC load. ### Claim 17 (depends on 16) The method of claim 16, wherein obtaining measurement values from the sensor comprises obtaining measurement values indicative of voltages of the first and second capacitors, and of at least one third capacitor of the switching cell, and wherein the operation of the switching cell is further controlled based on the voltage of the at least one third capacitor. ### Claim 18 (depends on 16) The method of claim 16, wherein the sensor is a first sensor, the method further comprising obtaining measurement values from a second sensor indicative of voltages of at least third and fourth capacitors of at least one additional switching cell connected in parallel to the half-bridge inverter and to the first switching cell. ### Claim 19 (depends on 16) The method of claim 16, wherein controlling operation of the switching cell comprises regulating voltages of the first and second capacitors. ### Claim 20 (depends on 19) The method of claim 19, wherein regulating the voltages of the first and second capacitors comprises actively balancing the voltages of the first and second capacitors to equal values.