# US 11,114,972 B2 · System, method and device for reflected wave cancellation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,114,972 B2 - Document ID: US11114972B2 - Status: Granted - Kind: B2 - Application number: 16/692,222 - Filed: 2019-11-22 - Published: 2020-08-20 - Granted: 2021-09-07 - Earliest claimed: 2019-02-15 - Assignees: The Florida State University Research Foundation, Inc. - Applicants: The Florida State University Research Foundation, Inc. - Inventors: Hui Li; Yu Zhang; Yanjun Shi - Web page: https://patentgrep.com/patent/US11114972B2 ## CPC - H02M 7/5387: in a bridge configuration - H02P 29/0241: {the fault being an overvoltage} - H02M 1/32: Means for protecting converters other than automatic disconnection - H02M 1/44: Circuits or arrangements for compensating for electromagnetic interference in converters or inverters - H02M 7/53871: {with automatic control of output voltage or current} - H02P 27/08: with 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) - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS ## Abstract An active reflected wave canceller (ARWC, or RWC) can attached to each phase at the output of a motor drive (i.e., inverter). The reflected wave canceller is generally comprised of a pulse generator and a power inductor. The power inductor is used to by-pass the load current, so it doesn't flow through the pulse generator. The pulse generator injects an accurately controlled nanoseconds narrow-width pulse into the system. The injected narrow pulse breaks the rising and falling edge of the inverter output voltage into two steps, which generates two traveling waves along the cable that cancel each other at the motor terminals. ## Claims ### Claim 1 A method of mitigating overvoltage at terminals of a load caused by a reflected wave, the method comprising: receiving a signal from an inverter, wherein said inverter provides a voltage waveform to a load through a cable having a length; and injecting two voltage pulses into the cable in each switching cycle, said one injected two voltage pulses corresponding to a leading edge of the inverter voltage waveform and another of the two injected voltage pulses corresponding to a trailing edge of the inverter voltage waveform, wherein the injected voltage pulse corresponding to the leading edge of the inverter voltage waveform has a first polarity, first width and first amplitude, wherein the signal results in the voltage pulse corresponding to the leading edge of the inverter voltage waveform breaking the leading edge of the inverter voltage waveform into a first two-step voltages, wherein a reflected voltage at the terminals of the load caused by a first step voltage of the first two-step voltages is substantially canceled by a reflected voltage caused by a second step voltage of the first two-step voltages, and wherein the injected voltage pulse corresponding to the trailing edge of the inverter voltage waveform has a second polarity that is opposite the first polarity, a second width and a second amplitude, wherein the signal results in the voltage pulse corresponding to the trailing edge of the inverter voltage waveform breaking the trailing edge of the inverter voltage waveform into a second two-step voltages, wherein a reflected voltage at the terminals of the load caused by a first step voltage of the second two-step voltages is substantially canceled by a reflected voltage caused by a second step voltage of the second two-step voltages. ### Claim 2 (depends on 1) The method of claim 1, wherein the first amplitude equals the second amplitude, and wherein the first amplitude and the second amplitude are approximately one-half of an amplitude of the inverter voltage waveform. ### Claim 3 (depends on 1) The method of claim 1, wherein the first width equals to the second width, and wherein the first width and the second width are each determined based on a transmission time of the cable, wherein a time period of the first width and the second width is two times the transmission time. ### Claim 4 (depends on 3) The method of claim 3, wherein the transmission time of the cable is the time for the pulse to travel the length of the cable which can be determined by calculation or measurement. ### Claim 5 (depends on 1) The method of claim 1, wherein the signal comprises a voltage signal or PWM control signal. ### Claim 6 An active reflected wave canceller comprising: a power inductor, wherein load current from an inverter passes through the power inductor and continues through a cable having a length to a load connected to the cable by terminals and wherein ratings of the power inductor are selected to bypass a fundamental frequency and switching frequency components of the load current; a full bridge circuit, wherein the full bridge circuit generates two voltage pulses that are injected into the cable in each switching cycle wherein one injected voltage pulse corresponds to a leading edge of an inverter voltage waveform and another injected voltage pulse corresponds to a trailing edge of the inverter voltage waveform; and a controller comprising pulse width adjustment circuits and protection circuits, wherein the pulse width adjustment circuits are used to control a time period of each voltage pulse based on different cable lengths, wherein the pulse width adjustment circuits receive a signal from the inverter such that the injected voltage pulse corresponding to the leading edge of the inverter voltage breaks the leading edge of the inverter voltage waveform into a first two-step voltages such that a reflected voltage at the terminals of the load caused by a first step voltage of the first two-step voltages is substantially canceled by a reflected voltage caused by a second step voltage of the first two-step voltages, and wherein the injected voltage pulse corresponding to a trailing edge of the inverter voltage waveform breaks the trailing edge of the inverter voltage waveform into a second two-step voltages such that a reflected voltage at the terminals of the load caused by a first step voltage of the second two-step voltages is substantially canceled by a reflected voltage caused by a second step voltage of the second two-step voltages, and wherein the protection circuits are used to protect the full bridge circuit from overcurrent, overtemperature and short circuits. ### Claim 7 (depends on 6) The active reflected wave canceller of claim 6, wherein the signal from the inverter comprises a voltage signal or PWM control signal. ### Claim 8 (depends on 7) The active reflected wave canceller of claim 7, wherein the signal from the inverter comprises pulse-width modulation (PWM) switching signals that can be received from the inverter via an optical fiber input or from sensing circuits. ### Claim 9 (depends on 6) The active reflected wave canceller of claim 6, wherein the full bridge circuit generates the two voltage pulses in each switching cycle, wherein the pulse corresponding to a leading edge of the inverter voltage waveform has a first amplitude and the pulse corresponding to the trailing edge of the inverter voltage waveform has a second amplitude, wherein the first amplitude equals the second amplitude and wherein the first amplitude and the second amplitude are approximately one-half of an amplitude of the inverter voltage waveform. ### Claim 10 (depends on 6) The active reflected wave canceller of claim 6, wherein the controller determines the time period of the voltage pulse corresponding to the leading edge of the inverter voltage and a time period of the voltage pulse corresponding to the trailing edge of the inverter voltage and wherein the time period is based on a transmission time of the cable, wherein the time period is two times the transmission time. ### Claim 11 (depends on 10) The active reflected wave canceller of claim 10, wherein the transmission time of the cable is the time for the pulse to travel the length of the cable which can be determined by a calculation or by a measurement. ### Claim 12 A system comprising: an inverter, wherein the inverter generates an inverter voltage waveform; a load, wherein the load is connected to the inverter at terminals by a cable having a length; and an active reflected wave canceller connected between the inverter and the cable, said active reflected wave canceller comprising: a power inductor, wherein load current from an inverter passes through the power inductor and continues through a cable having a length to a load connected to the cable by terminals and wherein ratings of the power inductor are selected to bypass a fundamental frequency and switching frequency components of the load current; a full bridge circuit, wherein the full bridge circuit generates two voltage pulses that are injected into the cable in each switching cycle wherein one injected voltage pulse corresponds to a leading edge of the inverter voltage waveform and another injected voltage pulse corresponds to a trailing edge of the inverter voltage waveform; and a controller comprising pulse width adjustment circuits and protection circuits, wherein the pulse width adjustment circuits are used to control a time period of each voltage pulse based on different cable lengths, wherein the pulse width adjustment circuits receive a signal from the inverter such that the injected voltage pulse corresponding to the leading edge of the inverter voltage breaks the leading edge of the inverter voltage waveform into a first two-step voltages such that a reflected voltage at the terminals of the load caused by a first step voltage of the first two-step voltages is substantially canceled by a reflected voltage caused by a second step voltage of the first two-step voltages, and wherein the injected voltage pulse corresponding to a trailing edge of the inverter voltage waveform breaks the trailing edge of the inverter voltage waveform into a second two-step voltages such that a reflected voltage at the terminals of the load caused by a first step voltage of the second two-step voltages is substantially canceled by a reflected voltage caused by a second step voltage of the second two-step voltages, and wherein the protection circuits are used to protect the full bridge circuit from overcurrent, overtemperature and short circuits. ### Claim 13 (depends on 12) The system of claim 12, wherein the load comprises a motor. ### Claim 14 (depends on 12) The system of claim 12, wherein the full bridge circuit generates the two voltage pulses in each switching cycle, wherein the pulse corresponding to a leading edge of the inverter voltage waveform has a first amplitude and the pulse corresponding to the trailing edge of the inverter voltage waveform has a second amplitude, wherein the first amplitude equals the second amplitude and wherein the first amplitude and the second amplitude are approximately one-half of an amplitude of the inverter voltage waveform. ### Claim 15 (depends on 12) The system of claim 12, wherein the controller determines the time period of the voltage pulse corresponding to the leading edge of the inverter voltage and a time period of the voltage pulse corresponding to the trailing edge of the inverter voltage and wherein the time period is based on a transmission time of the cable, wherein the time period is two times the transmission time. ### Claim 16 (depends on 15) The system of claim 15, wherein the transmission time of the cable is the time for the pulse to travel the length of the cable which can be determined by a calculation or by a measurement. ### Claim 17 (depends on 12) The system of claim 12, wherein the inverter is a poly-phase inverter and an overvoltage caused by the reflected voltage is mitigated at the terminals on each phase by a separate active reflected wave canceller installed on each phase. ### Claim 18 (depends on 12) The system of claim 12, wherein the inverter comprises silicon carbide (SiC) devices, wherein the full bridge circuit comprises a GaN full bridge circuit or Si full bridge circuit or SiC full bridge circuit, wherein the power inductor comprises an iron-core power inductor or an air-core power inductor. ### Claim 19 (depends on 12) The system of claim 12, wherein the inverter comprises Si devices, wherein the full bridge circuit comprises a GaN full bridge circuit or Si full bridge circuit or SiC full bridge circuit, wherein the power inductor comprises an iron-core power inductor or an air-core power inductor.