System, method and device for reflected wave cancellation

Patent metadata

Field	Value
Publication number	US-11114972-B2
Application number	US-201916692222-A
Country	US
Kind code	B2
Filing date	Nov 22, 2019
Priority date	Feb 15, 2019
Publication date	Sep 7, 2021
Grant date	Sep 7, 2021

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.

First claim

What is claimed is:

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.

2. 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.

3. 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.

4. 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.

5. The method of claim 1 , wherein the signal comprises a voltage signal or PWM control signal.

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.

7. The active reflected wave canceller of claim 6 , wherein the signal from the inverter comprises a voltage signal or PWM control signal.

8. 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.

9. 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.

10. 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.

11. 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.

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 su

Assignees

• Univ Florida State Res Found Inc

Inventors

• Li Hui
• Zhang Yu
• Shi Yanjun

Classifications

• H02M7/53871

  with automatic control of output voltage or current · CPC title

• H02M1/44

  Circuits or arrangements for compensating for electromagnetic interference in converters or inverters · CPC title

• H02M1/32

  Means for protecting converters other than automatic disconnection · CPC title

• H02M7/5387 Primary

  in a bridge configuration · CPC title

• H02P29/0241 Primary

  the fault being an overvoltage · CPC title