# US 8,542,505 B2 · Precision switching for carrier based PWM > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,542,505 B2 - Document ID: US8542505B2 - Status: Granted - Kind: B2 - Application number: 13/690,632 - Filed: 2012-11-30 - Published: 2013-04-11 - Granted: 2013-09-24 - Earliest claimed: 2010-06-01 - Assignees: ABB Technology AG - Applicants: Ying Jiang-Hafner - Inventors: Ying Jiang-Hafner - Web page: https://patentgrep.com/patent/US8542505B2 ## CPC - 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 7/537: using semiconductor devices only, e.g. single switched pulse inverters - 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 7/5395: 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 voltage source converter station including a multilevel voltage source converter, for conversion of electrical power between AC and DC, and a control system. The voltage source converter includes a plurality of switching cells including switchable semiconductors, and the control system includes at least one main control unit for providing a voltage reference signal and a plurality of cell control units. Each cell control unit uses carrier based pulse width modulation for controlling the switching of a respective cell, where the main control unit is communicatively connected to the cell control units and provides the reference voltage signal to each cell control unit and each cell control unit creates a switching signal to each respective switching cell using the reference voltage signal and a carrier signal to effectuate the conversion. ## Claims ### Claim 1 A voltage source converter station including a multilevel voltage source converter, for conversion of electrical power between AC and DC, and a control system, the voltage source converter comprises a plurality of switching cells including switchable semiconductors, and the control system comprises at least one main control unit for providing a voltage reference signal to a plurality of included cell control units, each cell control unit using carrier based pulse width modulation for controlling the switching of a respective cell, wherein the main control unit is communicatively connected to the cell control units and provides the reference voltage signal to each cell control unit and each cell control unit creates a switching signal to each respective switching cell using the reference voltage signal and a carrier signal to effectuate the conversion characterized in that each of the cell control units process signals at a higher frequency than the main control unit, wherein each cell control unit includes a reference signal reconstruction unit, for adapting the voltage reference signal to the higher frequency of the cell control unit, which signal reconstruction unit is adapted to provide a reconstructed reference voltage signal by interpolating sampling values of the reference voltage signal. ### Claim 2 (depends on 1) The voltage source converter station according to claim 1, wherein the interpolation is a linear interpolation between consecutive sampling points of the reference voltage signal. ### Claim 3 (depends on 1) The voltage source converter station according to claim 1, wherein each cell control unit includes a carrier signal generator, and generates the carrier signal. ### Claim 4 (depends on 1) The voltage source converter station according to claim 1, wherein each cell control unit includes a comparator for comparing the carrier signal and a reference signal, and the creation of the switching signal includes comparing the carrier signal and the reconstructed reference voltage signal. ### Claim 5 (depends on 1) The voltage source converter station according to claim 1, wherein each cell control unit includes a switching in-activator for avoiding unnecessary switching by holding the switching signal constant. ### Claim 6 (depends on 5) The voltage source converter station according to claim 5, wherein the switching in-activator includes a small value detector, and the in-activator is arranged to only hold the modulation signal constant when the reference voltage signal is smaller than a threshold value. ### Claim 7 (depends on 6) The voltage source converter station according to claim 6, wherein the threshold value being 15% of a nominal amplitude value of the reference voltage signal. ### Claim 8 (depends on 6) The voltage source converter station according to claim 6, wherein the switching in-activator includes an edge detector arranged for detecting switching pulses in the switching signal, and the switching in-activator is adapted to hold the switching signal constant a short time period after a switching signal is detected and the reference voltage signal is smaller than the threshold. ### Claim 9 (depends on 8) The voltage source converter station according to claim 8, wherein the short time period corresponds to the data rate of the main control unit and is the same, or approximately the same as, the time between two sampling values of the reference voltage signal. ### Claim 10 (depends on 1) The voltage source converter station according to claim 1, having at least eight switching cells per phase of the AC. ### Claim 11 (depends on 10) The voltage source converter station according to claim 10, having at least 20 switching cells per phase of the AC. ### Claim 12 (depends on 1) The voltage source converter station according to claim 1, wherein the carrier based pulse width modulation has a pulse number that is twelve or less. ### Claim 13 (depends on 12) The voltage source converter station according to claim 12, wherein the pulse number is less than 8. ### Claim 14 (depends on 1) The voltage source converter station according to claim 1, wherein the carrier based pulse width modulation has a pulse number that is a non-integer.