# US 2018/0323725 A1 · Systems and methods for synchronizing converter modules > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0323725 A1 - Document ID: US20180323725A1 - Status: Published application - Kind: A1 - Application number: 15/528,127 - Filed: 2015-12-18 - Published: 2018-11-08 - Earliest claimed: 2014-12-19 - Assignees: Sinewatts, Inc.; The University of North Carolina at Charlotte - Inventors: Robert Williams Cox; Daniel Wade Evans - Web page: https://patentgrep.com/patent/US20180323725A1 ## CPC - H02M 7/49: Combination of the output voltage waveforms of a plurality of converters - H02M 1/088: for the simultaneous control of series or parallel connected semiconductor devices - H02M 3/285: {Single converters with a plurality of output stages connected in parallel (parallel operation of a plurality of converters in DC distribution networks H02J1/10)} - H02M 7/493: the static converters being arranged for operation in parallel - H02M 7/5383: in a self-oscillating arrangement (H02M7/538 takes precedence) - H02M 7/5395: by pulse-width modulation - H02M 1/0043: {Converters switched with a phase shift, i.e. interleaved (non-isolated DC/DC converters H02M3/1586)} - H02M 1/0077: {Plural converter units whose outputs are connected in series} - 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 Various examples are directed to a converter system comprising first and second series-connected converter modules and a synchronization circuit. The synchronization circuit may modulate a reference signal onto a carrier signal to generate a synchronization current signal and the synchronization current signal to an output current of the converter system to generate an aggregated output current. A first converter module may receive the aggregated output current from a first current sensor and generate a first reproduced synchronization signal at least in part from the aggregated output current. A first switch control signal for switching at least one switch at the first converter may be generated based at least in part on the first reproduced synchronization signal. ## Claims ### Claim 1 A direct current (DC) to alternating current (AC) inverter system, comprising: a synchronization control circuit configured to: receive a grid signal from an electrical grid, the grid signal having a grid signal frequency; detect a zero-crossing of the grid signal; generate a pulse signal, wherein a first pulse of the pulse signal corresponds to the zero-crossing of the grid signal; modulate the pulse signal onto a carrier signal to generate a synchronization current signal having a synchronization current signal frequency higher than the grid signal frequency; add the synchronization current signal to an output current of the inverter system to generate an aggregated output current; a first inverter module configured to receive a first DC input from a first DC source and provide a first AC output voltage at a first output, the first inverter module comprising: a first switch electrically coupled between the first DC source and the first output; a first current-mode transformer electrically coupled to sense the aggregated output current; a first module control circuit configured to: detect the synchronization current signal from the first current-mode transformer; demodulate the synchronization current signal to generate a first reproduced pulse signal; and generate a first switch control signal based at least in part on the first reproduced pulse signal; a second inverter module configured to receive a second DC input from a second DC source and provide a second AC output voltage at a second output, wherein the first inverter module and the second inverter module are electrically coupled in series, and wherein an AC output voltage of the inverter system comprises a sum of the first AC output voltage and the second AC output voltage, the second inverter module comprising: a second switch electrically coupled between the second DC source and the second output; a second current-mode transformer electrically coupled to the electrical grid; a second module control circuit configured to: detect the synchronization current signal from the second current-mode transformer; demodulate the synchronization current signal to generate a second reproduced pulse signal; and generate a second switch control signal based at least in part on the second reproduced pulse signal. ### Claim 2 (depends on 1) The system of claim 1, wherein the synchronization current signal frequency is at least ten times higher than the grid signal frequency. ### Claim 3 (depends on 1) The system of claim 1, wherein the grid signal is a voltage on the electrical grid. ### Claim 4 (depends on 1) The system of claim 1, wherein the synchronization control circuit is further configured to: determine a first amplitude of a current introduced onto the electrical grid by the system of claim 1; determine a second amplitude of the current introduced onto the electrical grid, wherein the second amplitude is greater than the first amplitude; and increase an amplitude of the synchronization current signal. ### Claim 5 (depends on 1) The system of claim 1, wherein the first module control circuit is further configured to: detect a first amplitude of the synchronization current signal; detect a second amplitude of the synchronization current signal, where the second amplitude is lower than the first amplitude; and increase a gain of an amplifier applied to the synchronization current signal. ### Claim 6 (depends on 1) The system of claim 1, wherein the synchronization control circuit comprises a monitoring circuit electrically coupled to receive the grid signal, wherein an output of the monitoring circuit is the pulse signal. ### Claim 7 (depends on 1) The system of claim 1, wherein the synchronization control circuit comprises at least one processor programmed to receive the grid signal from the electrical grid; detect the zero-crossing of the grid signal; generate the pulse signal; and modulate the pulse signal onto the carrier signal. ### Claim 8 (depends on 1) The system of claim 1, further comprising a plurality of inverter modules, the plurality of inverter modules comprising the first inverter module and the second inverter module, wherein the synchronization control circuit is electrically connected in parallel with the plurality of inverter modules. ### Claim 9 (depends on 1) The system of claim 1, wherein the first module control circuit is further configured to generate the first switch control signal substantially in phase or in some predetermined relationship with the first reproduced pulse signal. ### Claim 10 (depends on 1) The system of claim 1, wherein the grid signal comprises at least one of: a current of the electrical grid, a voltage of the electrical grid, a combination of harmonics contained within the of the voltage of the electrical grid, and a combination of harmonics contained within the current of the electrical grid. ### Claim 11 A converter system, comprising: a synchronization control circuit configured to: modulate a reference signal onto a carrier signal to generate a synchronization current signal; add the synchronization current signal to an output current of the converter system to generate an aggregated output current; and a first converter module configured to receive a first direct current (DC) input from a first DC source and provide a first output voltage at a first output, the first converter module comprising: a first switch; a first current sensor; and a first module control circuit configured to: receive the aggregated output current from the first current sensor; generate a first reproduced reference signal, at least in part from the aggregated output current; and generate a first switch control signal based at least in part on the first reproduced reference signal; a second converter module configured to receive a second DC input from a second DC source and provide a second output voltage at a second output, wherein the first converter module and the second converter module are electrically coupled in series and wherein an output voltage of the converter system comprises a sum of the first output voltage and the second output voltage, the second converter module comprising: a second switch; a second current sensor; and a second module control circuit configured to: receive the aggregated output current from the second current sensor; generate a second reproduced reference signal, at least in part from the aggregated output current; and generate a second switch control signal based at least in part on the reference signal. ### Claim 12 (depends on 11) The system of claim 11, wherein the synchronization control circuit further comprises a monitoring circuit electrically connected to receive a grid signal and output the reference signal, wherein the reference signal comprises a first pulse that is at a first zero-crossing of the reference signal. ### Claim 13 (depends on 12) The system of claim 12, wherein the grid signal comprises at least one of: a voltage of an electrical grid, a current of the electrical grid, a harmonic of the voltage of the electrical grid, and a harmonic of the current of the electrical grid. ### Claim 14 (depends on 11) The system of claim 11, wherein the first module control circuit is further configured to generate the first switch control signal substantially in phase or in some predetermined relationship with the first reproduced reference signal. ### Claim 15 (depends on 11) The system of claim 11, wherein the synchronization control circuit is further configured to: detect a first value for the output current at a first time; detect a second value for the output current at a second time after the first time, wherein the second value for the output current is higher than the first value for the output current; and increase an amplitude of the synchronization current signal. ### Claim 16 (depends on 11) The system of claim 11, wherein the first module control circuit comprises at least one filter to extract the synchronization current signal from the aggregated output current. ### Claim 17 (depends on 11) The system of claim 11, wherein the first module control circuit further comprises a first demodulator to generate the first reproduced reference signal. ### Claim 18 (depends on 11) The system of claim 11, further comprising a plurality of converter modules, the plurality of converter modules comprising the first converter module and the second converter module, wherein the synchronization control circuit is electrically connected in parallel with the plurality of converter modules. ### Claim 19 A series-connected converter system comprising: a synchronization control circuit, comprising: a monitoring circuit configured to receive an input signal and output a pulse signal, wherein a first pulse of the pulse signal corresponds to a first zero-crossing of the input signal; a modulator configured to generate a synchronization signal based at least in part on the pulse signal; a transformer comprising a first coil electrically coupled to receive the synchronization signal and a second coil electrically coupled to an output of the converter system; a first converter module electrically coupled between a first direct current (DC) source and a first output, the first converter module comprising: a first switch; a first current sensor positioned to sense an aggregated output current of the converter system, wherein the aggregated output current is a sum of an output current of the converter system and a synchronization current signal proportional to the synchronization signal; a first demodulator in communication with the first current sensor to generate a first reproduced pulse signal, at least in part from the aggregated output current; and a first module control circuit configured to generate a first switch control signal based at least in part on the first reproduced pulse signal; and a second converter module electrically coupled between a second DC source and a second output, the second converter module comprising: a second switch; a second current sensor positioned to sense the aggregated output current of the converter system; a second demodulator in communication with the second current sensor to generate a second reproduced pulse signal, at least in part from the aggregated output current; and a second module control circuit configured to generate a second switch control signal based at least in part on the second reproduced pulse signal, wherein the first converter module and the second converter module are electrically coupled in series, and wherein an output voltage of the converter system comprises a sum of a first output voltage at the first output and a second output voltage a second output voltage at the second output. ### Claim 20 (depends on 19) The system of claim 19, wherein the first module control circuit is further configured to generate the first switch control signal substantially in phase or in some predetermined relationship with the first reproduced pulse signal. ### Claim 21 (depends on 19) The system of claim 19, wherein the synchronization control circuit further comprises at least one processor programmed to: detect a first value for the output current of the converter at a first time; detect a second value for the output current of the converter at a second time after the first time, wherein the second value for the output current is higher than the first value for the output current; and increase a gain of an amplifier applied to the synchronization signal. ### Claim 22 (depends on 19) The system of claim 19, wherein the first module control circuit is further configured to: detect a first amplitude of the synchronization current signal; detect a second amplitude of the synchronization current signal, where the second amplitude is lower than the first amplitude; extract a reproduced synchronization signal from the aggregated output current; and increase a gain of an amplifier applied to the reproduced synchronization signal.