阅读说明：本技术 隔离转换器 (Isolation converter ) 是由 H·瓦赫迪 M-A·佛盖特 于 2020-04-14 设计创作，主要内容包括：本公开提供了一种使用转换器提供电隔离的方法和装置,所述转换器包括：第一转换器,其在整流器模式下工作,所述第一转换器接收AC电流并提供DC电流；第二转换器,其在逆变器模式下工作,所述第二转换器从所述第一转换器接收所述DC电流并提供AC电流；变压器,其接收来自所述第二转换器的所述AC电流,具有输入部和输出部,所述变压器在所述输入部和输出部之间提供电隔离；第三转换器,其在整流器模式下工作,所述第三转换器从所述变压器接收AC电流并提供DC电流,其中所述第一转换器、所述第二转换器和所述第三转换器中的至少一个是多电平转换器。(The present disclosure provides a method and apparatus for providing electrical isolation using a converter, the converter comprising: a first converter operating in a rectifier mode, the first converter receiving an AC current and providing a DC current; a second converter operating in an inverter mode, the second converter receiving the DC current from the first converter and providing an AC current; a transformer receiving the AC current from the second converter, having an input and an output, the transformer providing electrical isolation between the input and output; a third converter operating in a rectifier mode, the third converter receiving AC current from the transformer and providing DC current, wherein at least one of the first, second, and third converters is a multilevel converter.)

1. An isolated DC-DC converter, comprising:

-a first converter, operating in an inverter mode, receiving a DC current and providing an AC current;

-a transformer receiving the AC current, the transformer having an input and an output, the transformer providing electrical isolation between the input and output;

-a second converter, operating in rectifier mode, receiving an AC current from the transformer and providing a DC current;

wherein at least one of the first converter and the second converter is a multilevel converter comprising:

an AC port;

at least one DC port;

a power converter component connected to the AC port and the at least one DC port to convert power between the AC port and the DC port at a variable voltage, the power converter component comprising:

at least one high voltage capacitor storing power at a boosted voltage higher than a peak voltage of the AC port;

a circuit, comprising:

an inductor connected in series with the AC port,

a low-voltage capacitor, which is connected to the capacitor,

one of the following:

two diodes connected between a first AC port terminal and opposite ends of the high voltage capacitor; and

two high voltage switches connected between a first AC port terminal and opposite ends of the high voltage capacitor,

two intermediate low-voltage power switches connected between said opposite ends of said high-voltage capacitor and opposite ends of said low-voltage capacitor, and

two end low voltage power switches connected between the opposite ends of the low voltage capacitor and a second AC terminal,

wherein the DC port is connectable to the opposite ends of the high voltage capacitor; and

a controller having at least one sensor for sensing current and/or voltage in the circuit and connected to the gate inputs of the two intermediate low voltage power switches and the two end low voltage power switches.

2. The isolated DC-DC converter of claim 1 wherein the controller is operable for operating the circuit in a rectifier boost mode in which the voltage of the high voltage capacitor is above the peak voltage of the AC port, and the two intermediate low voltage power switches and the two end low voltage power switches switch in redundant switching states in response to a measurement of the voltage present at the low voltage capacitor to maintain the low voltage capacitor at a predetermined fraction of the desired voltage of the high voltage capacitor and thus maintain the high voltage capacitor at the desired high voltage, wherein the circuit provides a DC load and absorbs power as a five level active rectifier with low harmonics on the AC port.

3. The isolated DC-DC converter of claim 1 or 2 wherein the controller interface is further in communication with a battery and receives a desired charging current value, and the power converter is further responsive to the desired charging current value to convert power from the AC port to DC at a DC output at a variable current that does not exceed the desired charging current value for a DC load.

4. The isolated DC-DC converter of any of claims 1 to 3, further comprising a buck converter circuit to convert DC power from the opposite ends of the high voltage capacitor to a lower DC output voltage set by the charging voltage value.

5. The isolated DC-DC converter of any of claims 1 to 4, further comprising a boost converter circuit to convert DC power from the opposite ends of the high voltage capacitor to a higher DC output voltage set by the charging voltage value.

6. The isolated DC-DC converter of any of claims 1 to 5, wherein the two middle low voltage power switches and the two end low voltage power switches switch at a frequency above 10 kHz.

7. The isolated DC-DC converter of any of claims 1 to 6, wherein:

the circuit is a bidirectional rectifier/inverter circuit comprising an inductor connected in series with an AC port, a low voltage capacitor, two high voltage power switches connected between a first AC terminal and opposite ends of the high voltage capacitor, two intermediate low voltage power switches connected between the opposite ends of the high voltage capacitor and opposite ends of the low voltage capacitor, and two end low voltage power switches connected between the opposite ends of the low voltage capacitor and a second AC terminal; wherein a DC port is connectable to the opposite ends of the high voltage capacitor;

the controller is a first controller for rectifier mode having at least one sensor for sensing current and/or voltage in the bidirectional rectifier/inverter and connected to the gate inputs of the two high voltage power switches, the two intermediate low voltage power switches and the two end low voltage power switches for operating the rectifier circuit in boost mode with the voltage of the high voltage capacitor above the peak voltage of the AC port and controlling the two high voltage power switches to be switched on and off at the frequency of the AC port and the two intermediate low voltage power switches and the two end low voltage power switches to switch in redundant switching states in response to a measurement of the voltage present at the low voltage capacitor so as to maintain the low voltage capacitor at a predetermined fraction of the desired voltage of the high voltage capacitor, and thus maintain the high voltage capacitor at a desired high voltage, wherein the rectifier circuit provides the DC load and absorbs power as a five-level active rectifier with low harmonics on the AC port; and

the power converter further includes a second controller for inverter mode connected to the two high voltage power switches, the two intermediate low voltage power switches, and the two end low voltage power switches and configured to generate and apply signal waveforms to the two high voltage power switches, the two intermediate low voltage power switches, and the two end low voltage power switches, the signal waveforms including: a first control signal for connecting the low voltage capacitor in series with the DC port and the AC port and charging at a predetermined value proportional to the voltage of the DC port; and a second control signal for disconnecting the low voltage capacitor from the DC port and connecting in series with the AC port, thereby discharging the low voltage capacitor.

8. The isolated DC-DC converter of any of claims 1 to 7, wherein the isolated DC-DC converter is an on-board isolated DC-DC converter for use in an electric or hybrid vehicle.

9. The isolated DC-DC converter of any of claims 1 to 8, wherein the first converter operating in the inverter mode provides an AC current having a frequency above 400 Hz.

10. The isolated DC-DC converter of any of claims 1 to 9, wherein the first converter has a switching frequency of at least about 20 kHz.

11. An isolated AC-DC converter, comprising:

-a first converter operating in a rectifier mode, the first converter receiving an AC current and providing a DC current;

-a second converter operating in an inverter mode, the second converter receiving the DC current from the first converter and providing an AC current;

-a transformer receiving the AC current from the second converter, the transformer having an input and an output, the transformer providing electrical isolation between the input and output;

-a third converter operating in a rectifier mode, the third converter receiving an AC current from the transformer and providing a DC current;

wherein at least one of the first converter, the second converter, and the third converter is a multilevel converter.

12. The isolated AC-DC converter of claim 11 wherein the multilevel converter comprises:

an AC port;

at least one DC port;

a power converter component connected to the AC port and the at least one DC port to convert power between the AC port and the DC port at a variable voltage, the power converter component comprising:

at least one high voltage capacitor storing power at a boosted voltage higher than a peak voltage of the AC port;

a circuit, comprising:

an inductor connected in series with the AC port,

a low-voltage capacitor, which is connected to the capacitor,

one of the following:

two diodes connected between a first AC port terminal and opposite ends of the high voltage capacitor; and

two high voltage switches connected between a first AC port terminal and opposite ends of the high voltage capacitor,

two intermediate low-voltage power switches connected between said opposite ends of said high-voltage capacitor and opposite ends of said low-voltage capacitor, and

two end low voltage power switches connected between the opposite ends of the low voltage capacitor and a second AC terminal,

wherein the DC port is connectable to the opposite ends of the high voltage capacitor; and

a controller having at least one sensor for sensing current and/or voltage in the circuit and connected to the gate inputs of the two intermediate low voltage power switches and the two end low voltage power switches.

13. The isolated AC-DC converter of claim 12 wherein the controller is operable for operating the circuit in a rectifier boost mode in which the voltage of the high voltage capacitor is above the peak voltage of the AC port, and the two intermediate low voltage power switches and the two end low voltage power switches switch in redundant switching states in response to a measurement of the voltage present at the low voltage capacitor to maintain the low voltage capacitor at a predetermined fraction of the desired voltage of the high voltage capacitor and thus maintain the high voltage capacitor at the desired high voltage, wherein the circuit provides a DC load and absorbs power as a five level active rectifier with low harmonics on the AC port.

14. The isolated AC-DC converter of claim 12 or 13 wherein the controller interface is further in communication with a storage battery and receives a desired charging current value, and the power converter is further responsive to the desired charging current value to convert power from the AC port to DC at a DC output at a variable current that does not exceed the desired charging current value of a DC load.

15. An isolated AC-DC converter according to any of claims 12 to 14, further comprising a buck converter circuit to convert DC power from the opposite ends of the high voltage capacitor to a lower DC output voltage set by the charging voltage value.

16. An isolated AC-DC converter according to any of claims 12 to 15, further comprising a boost converter circuit to convert DC power from the opposite ends of the high voltage capacitor to a higher DC output voltage set by the charging voltage value.

17. An isolated AC-DC converter according to any of claims 12 to 16 wherein the two intermediate low voltage power switches and the two end low voltage power switches switch at a frequency above 10 kHz.

18. The isolated AC-DC converter of any one of claims 12 to 17, wherein:

the circuit is a bidirectional rectifier/inverter circuit comprising an inductor connected in series with an AC port, a low voltage capacitor, two high voltage power switches connected between a first AC terminal and opposite ends of the high voltage capacitor, two intermediate low voltage power switches connected between the opposite ends of the high voltage capacitor and opposite ends of the low voltage capacitor, and two end low voltage power switches connected between the opposite ends of the low voltage capacitor and a second AC terminal; wherein a DC port is connectable to said opposite ends of said high voltage capacitor;

the controller is a first controller for rectifier mode having at least one sensor for sensing current and/or voltage in the bidirectional rectifier/inverter and connected to the gate inputs of the two high voltage power switches, the two intermediate low voltage power switches and the two end low voltage power switches for operating the rectifier circuit in boost mode with the voltage of the high voltage capacitor above the peak voltage of the AC port and controlling the two high voltage power switches to be switched on and off at the frequency of the AC port and the two intermediate low voltage power switches and the two end low voltage power switches to switch in redundant switching states in response to a measurement of the voltage present at the low voltage capacitor so as to maintain the low voltage capacitor at a predetermined fraction of the desired voltage of the high voltage capacitor, and thus maintain the high voltage capacitor at a desired high voltage, wherein the rectifier circuit provides the DC load and absorbs power as a five-level active rectifier with low harmonics on the AC port; and

the power converter further includes a second controller for inverter mode connected to the two high voltage power switches, the two intermediate low voltage power switches, and the two end low voltage power switches and configured to generate and apply signal waveforms to the two high voltage power switches, the two intermediate low voltage power switches, and the two end low voltage power switches, the signal waveforms including: a first control signal for connecting the low voltage capacitor in series with the DC port and the AC port and charging at a predetermined value proportional to the voltage of the DC port; and a second control signal for disconnecting the low voltage capacitor from the DC port and connecting in series with the AC port, thereby discharging the low voltage capacitor.

19. An isolated AC-DC converter according to any of claims 11 to 18 wherein the first converter has a diode bridge for unidirectional applications.

20. An isolated AC-DC converter according to any of claims 11 to 18 wherein the isolated AC-DC converter is a bidirectional isolated converter.

21. An isolated AC-DC converter according to any of claims 11 to 20 wherein the first, second and third converters are multilevel converters and the isolated AC-DC converter operates bi-directionally.

22. An isolated AC-DC converter according to any of claims 11 to 21 wherein the first converter has a diode bridge and a conventional DC-DC buck converter or boost converter to provide power factor correction.

23. An isolated AC-DC converter according to any of claims 11 to 22 wherein the first converter has an active pulse width modulated rectifier to provide power factor correction.

24. The isolated AC-DC converter of any of claims 11-23, wherein the isolated AC-DC converter is an on-board isolated AC-DC converter for use in an electric or hybrid vehicle.

25. An isolated AC-DC converter according to any of claims 11 to 24 wherein the second converter provides an AC current having a frequency above 400 Hz.

26. An isolated AC-DC converter according to any of claims 11 to 25 wherein the second converter has a switching frequency of 20 kHz.

27. A method of providing electrical isolation using an isolation converter, the method comprising:

-providing a first DC current to the isolated converter;

-selecting a first output frequency for converting the first DC current into a first AC current;

-converting the first DC current into the first AC current at the first output frequency using a first conversion circuit;

-providing the first AC current to a transformer having a size and receiving a second AC output current electrically isolated from the first AC current;

wherein the size of the transformer providing isolation is determined based on the first output frequency of the first AC current.

28. The method of claim 27, wherein providing the first DC current to the isolated converter comprises:

-receiving a third AC current having a third frequency lower than the first frequency of the first AC current;

-converting the third AC current into the first DC current using a second converter circuit.

29. The method of claim 27, wherein at least one of the first converter circuit and the second converter circuit is a multilevel converter circuit.

30. The method of claim 28, wherein the multilevel converter circuit is a five-level active rectifier.

31. The method of any of claims 27-30, wherein converting the first DC current to the first AC current at the first output frequency using the first conversion circuit comprises providing a multi-level voltage AC waveform with harmonic rejection.

32. The method of any of claims 27-31, further comprising converting the second AC current to a second DC current using a third converter circuit.

Technical Field

The present disclosure relates generally to the field of converters, and more particularly to converters that provide galvanic isolation.

Background

This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be discussed on-going, but are not necessarily ones that have been previously conceived or discussed. Thus, unless otherwise indicated herein, what is described in this section is not prior art to the specific embodiments and claims in this application and is not admitted to be prior art by inclusion in this section.

Although non-isolated converters are more common than isolated converters, they suffer from the disadvantage that there is an electrical connection, such as a common ground, between the input and output. Many safety standards and/or customer requirements separate the applied input and output voltages, which are typically user accessible.

This can be a problem when dealing with electric vehicles because the isolation converter has a high frequency transformer providing an isolation barrier that can typically withstand any voltage from several hundred volts to several thousand volts, as may be required for medical applications. A second advantage of an isolated converter is that the output can be configured to be positive or negative.

Electric vehicles ("EVs") typically use isolated converters, which are larger and more expensive than non-isolated converters. The main requirement for isolation is to meet safety requirements when higher power levels are encountered.

Therefore, there is a need to improve the power conversion efficiency of such on-board converters while reducing weight and volume. As society and government have driven the reduction of fossil fuel consumption and emissions of carbon dioxide and other greenhouse gases, this is becoming more imperative in view of the popularity of electric vehicles.

Furthermore, most available isolation converters use a transformer, which, while effective in providing the galvanic isolation required by electric vehicles, can be large and heavy.

Therefore, there is a need to reduce the size of these transformers without reducing the overall efficiency of the converter while benefiting from the ability of the transformers to provide electrical isolation.

Disclosure of Invention

The applicant has found a method and a device for providing isolated conversion for different types of currents, which device has a high efficiency and can be realized using small transformers.

In one broad aspect, the present disclosure provides a method of providing electrical isolation using an isolated converter. The method includes providing a first DC current to an isolation converter, selecting a first frequency for converting the first DC current to a first AC current, converting the first DC current to the first AC current at the first frequency using a first conversion circuit, providing the first AC current to a transformer, and receiving a second AC current that is electrically isolated from the first AC current. Selecting the first frequency of the first AC current determines the size of the transformer that provides isolation. In some embodiments, the size of the transformer may be reduced by using higher frequencies.

Those skilled in the art will appreciate that the size of the transformer may depend on the desired output voltage of the transformer.

In some examples of the disclosure, providing the first DC current to the isolated converter may include: a third AC current having a third frequency lower than the first frequency of the first AC current is received and converted to a first DC current using a second converter circuit.

In some examples, one or more of the first converter circuit and the second converter circuit for converting may be a multi-level converter circuit. In some examples, the multi-level converter circuit is a five-level active rectifier. An example of such power is disclosed by the applicant in the international PCT patent application with serial number PCT/CA2018/051291 and publication number WO 2019/071359.

In some examples, the method may further include converting the second AC current to a second DC current using a third converter circuit. This will provide DC-DC isolated conversion between the input and output of the converter.

In one broad aspect, the present disclosure provides an isolated DC-DC converter comprising: a first converter operating in an inverter mode, the first converter receiving a DC current and providing an AC current; a transformer receiving an AC current, having an input and an output, the transformer providing electrical isolation between the input and the output; a second converter operating in a rectifier mode, the second converter receiving the AC current from the transformer and providing a DC current. At least one of the first converter and the second converter is a multilevel converter comprising: an AC port; at least one DC port; a power converter component connected to an AC; and at least one DC port for converting power between the AC port and the DC port at a variable voltage. The power converter components include at least one high voltage capacitor for storing power at a boosted voltage above the peak voltage of the AC port and circuitry. The circuit comprises an inductor connected in series with the AC port, a low voltage capacitor, two diodes or two high voltage switches connected between the first AC port terminal and opposite ends of the high voltage capacitor; two intermediate low voltage power switches connected between opposite ends of the high voltage capacitor and opposite ends of the low voltage capacitor, and two end low voltage power switches connected between opposite ends of the low voltage capacitor and the second AC terminal. The DC port may be connected to opposite ends of the high voltage capacitor. It also includes a controller having at least one sensor for sensing current and/or voltage in the circuit and connected to the gate inputs of the two intermediate low voltage power switches and the two end low voltage power switches.

In some embodiments, the controller is operable to cause the circuit to operate in a rectifier boost mode in which the voltage of the high voltage capacitor is above the peak voltage of the AC port, and the two intermediate low voltage power switches and the two end low voltage power switches are switched in a redundant switching state in response to a measurement of the voltage present at the low voltage capacitor to maintain the low voltage capacitor at a predetermined fraction of the desired voltage of the high voltage capacitor and thus maintain the high voltage capacitor at the desired high voltage, wherein the circuit provides a DC load and absorbs power as a five level active rectifier with low harmonics on the AC port.

In some embodiments, the converter further includes a controller interface in communication with the battery and receiving a desired charging current value, and the power converter is further responsive to the desired charging current value to convert power from the AC port to DC at the DC output with a variable current that does not exceed the desired charging current value of the DC load.

In some embodiments, the isolated DC-DC converter may further include a buck converter circuit to convert DC power from opposite ends of the high voltage capacitor to a lower DC output voltage set by the charging voltage value.

In some embodiments, the isolated DC-DC converter may further include a boost converter circuit to convert DC power from opposite ends of the high voltage capacitor to a higher DC output voltage set by the charging voltage value.

In some embodiments, the two intermediate low voltage power switches and the two end low voltage power switches are switched at a frequency higher than 10 kHz.

In some embodiments, the converter includes a housing including a connector backplane having a plurality of module receptacles and at least one module connected in the module receptacles, each of the modules including a rectifier circuit, the modules operating in parallel to provide DC power to a load.

In some embodiments, the circuitry of the multilevel converter may be a bidirectional rectifier/inverter circuit with two controllers. The embodiment comprises the following steps: an inductor connected in series with the AC port, a low voltage capacitor, two high voltage power switches connected between the first AC terminal and opposite ends of the high voltage capacitor, two intermediate low voltage power switches connected between opposite ends of the high voltage capacitor and opposite ends of the low voltage capacitor, and two end low voltage power switches connected between opposite ends of the low voltage capacitor and the second AC terminal; wherein the DC port is connectable to opposite ends of the high voltage capacitor; the controller is a first controller for the rectifier mode having at least one sensor for sensing current and/or voltage in the bidirectional rectifier/inverter and connected to the gate inputs of the two high voltage power switches, the two intermediate low voltage power switches and the two end low voltage power switches to operate the rectifier circuit in a boost mode in which the voltage of the high voltage capacitor is above the peak voltage of the AC port and the two high voltage power switches are controlled to be switched on and off at the frequency of the AC port and the two intermediate low voltage power switches and the two end low voltage power switches are switched in a redundant switching state in response to a measurement of the voltage present at the low voltage capacitor to maintain the low voltage capacitor at a predetermined fraction of the desired voltage of the high voltage capacitor and thus maintain the high voltage capacitor at the desired high voltage, wherein the rectifier circuit provides a DC load and absorbs power as a five-level active rectifier with low harmonics on the AC port; and the power converter further comprises a second controller for inverter mode connected to the two high voltage power switches, the two intermediate low voltage power switches and the two end low voltage power switches and configured to generate and apply signal waveforms to the two high voltage power switches, the two intermediate low voltage power switches and the two end low voltage power switches, the signal waveforms comprising: a first control signal for connecting a low voltage capacitor in series with the DC port and the AC port and charging at a predetermined value proportional to the voltage of the DC port; and a second control signal for disconnecting the low-voltage capacitor from the DC port and connecting in series with the AC port, thereby discharging the low-voltage capacitor.

In some examples of DC-DC converters, the first converter provides an AC current having a frequency above 400Hz, preferably up to about 4 kHz.

In some examples of the DC-DC converter, the first converter may have a switching frequency of 20 kHz.

In another broad aspect, the present disclosure provides an isolated AC-DC converter comprising: a first converter operating in a rectifier mode, the first converter receiving an AC current and providing a DC current; a second converter operating in an inverter mode, the second converter receiving the DC current from the first converter and providing an AC current; a transformer receiving the AC current from the second converter, having an input and an output, the transformer providing electrical isolation between the input and the output; a third converter operating in a rectifier mode, the third converter receiving the AC current from the transformer and providing the DC current, wherein at least one of the first converter, the second converter, and the third converter is a multilevel converter. The multilevel converter includes: an AC port; at least one DC port; a power converter component connected to an AC; and at least one DC port for converting power between the AC port and the DC port at a variable voltage. The power converter components include at least one high voltage capacitor for storing power at a boosted voltage above the peak voltage of the AC port and circuitry. The circuit comprises: an inductor connected in series with the AC port, a low voltage capacitor, two diodes or high voltage switches connected between the first AC port terminal and opposite ends of the high voltage capacitor, two intermediate low voltage power switches connected between opposite ends of the high voltage capacitor and opposite ends of the low voltage capacitor, two end low voltage power switches connected between opposite ends of the low voltage capacitor and the second AC terminal, wherein the DC port is connectable to opposite ends of the high voltage capacitor; and a controller having at least one sensor for sensing current and/or voltage in the circuit and connected to the gate inputs of the two intermediate low voltage power switches and the two end low voltage power switches.

In some embodiments, the controller may be operative to cause the circuit to operate in a rectifier boost mode in which the voltage of the high voltage capacitor is above the peak voltage of the AC port, and the two intermediate low voltage power switches and the two end low voltage power switches are switched in a redundant switching state in response to a measurement of the voltage present at the low voltage capacitor to maintain the low voltage capacitor at a predetermined fraction of the desired voltage of the high voltage capacitor and thus maintain the high voltage capacitor at the desired high voltage, wherein the circuit provides the DC load and absorbs power as a five level active rectifier with low harmonics on the AC port.

In some embodiments, the controller interface is further in communication with the battery and receives a desired charging current value, and the power converter is further responsive to the desired charging current value to convert power from the AC port to DC at the DC output at a variable current that does not exceed the desired charging current value of the DC load.

In some embodiments, the multilevel converter further comprises a buck, boost or buck/boost converter circuit for converting DC power from opposite ends of the high voltage capacitor to a lower DC output voltage set by the charging voltage value.

In some embodiments, the two intermediate low voltage power switches and the two end low voltage power switches are switched at a frequency higher than 10 kHz.

In some embodiments, the circuit may be a bidirectional rectifier/inverter circuit comprising: an inductor connected in series with the AC port, a low voltage capacitor, two high voltage power switches connected between the first AC terminal and opposite ends of the high voltage capacitor, two intermediate low voltage power switches connected between opposite ends of the high voltage capacitor and opposite ends of the low voltage capacitor, and two end low voltage power switches connected between opposite ends of the low voltage capacitor and the second AC terminal; wherein the DC port is connectable to opposite ends of the high voltage capacitor; the controller is a first controller for the rectifier mode having at least one sensor for sensing current and/or voltage in the bidirectional rectifier/inverter and connected to the gate inputs of the two high voltage power switches, the two intermediate low voltage power switches and the two end low voltage power switches to operate the rectifier circuit in a boost mode in which the voltage of the high voltage capacitor is above the peak voltage of the AC port and the two high voltage power switches are controlled to be switched on and off at the frequency of the AC port and the two intermediate low voltage power switches and the two end low voltage power switches are switched in a redundant switching state in response to a measurement of the voltage present at the low voltage capacitor to maintain the low voltage capacitor at a predetermined fraction of the desired voltage of the high voltage capacitor and thus maintain the high voltage capacitor at the desired high voltage, wherein the rectifier circuit provides a DC load and absorbs power as a five-level active rectifier with low harmonics on the AC port; and the power converter further comprises a second controller for inverter mode connected to the two high voltage power switches, the two intermediate low voltage power switches and the two end low voltage power switches and configured to generate and apply signal waveforms to the two high voltage power switches, the two intermediate low voltage power switches and the two end low voltage power switches, the signal waveforms comprising: a first control signal for connecting a low voltage capacitor in series with the DC port and the AC port and charging at a predetermined value proportional to the voltage of the DC port; and a second control signal for disconnecting the low-voltage capacitor from the DC port and connecting in series with the AC port, thereby discharging the low-voltage capacitor.

In some embodiments of the isolated AC-DC converter, the first converter may have a diode bridge for unidirectional applications. In some embodiments of the isolated AC-DC converter, the first converter has a diode bridge and a conventional DC-DC buck converter or boost converter to provide power factor correction.

In some embodiments of the isolated AC-DC converter, the first converter has an active pulse width modulated rectifier to provide power factor correction.

The isolated AC-DC converter and DC-DC converter of the present disclosure may be used as an on-board isolation converter in an electric, hybrid, or any other type of vehicle that requires an on-board isolation converter.

In one aspect, the present disclosure provides an isolated AC-DC converter comprising: a converter operating in an inverter mode, the converter receiving a DC current and providing an AC current; a transformer that receives an AC current, having an input and an output, the transformer providing electrical isolation between the input and the output. As explained herein, the converter may be a multilevel converter.

In some examples of AC-DC converters, the second converter provides an AC current having a frequency above 400Hz, preferably up to about 4 kHz.

In some examples of the AC-DC converter, the second converter has a switching frequency of 20 kHz.

In one broad aspect, the present disclosure provides a method of providing electrical isolation using an isolated converter. The method includes providing a first DC current to an isolation converter, selecting a first output frequency for converting the first DC current to a first AC current, converting the first DC current to the first AC current at the first output frequency using a first conversion circuit, providing the first AC current to a transformer having a size, and receiving a second AC output current that is electrically isolated from the first AC current, wherein the size of the transformer providing isolation is determined based on the first output frequency of the first AC current.

In some examples of the method, providing the first DC current to the isolated converter includes receiving a third AC current having a third frequency lower than the first frequency of the first AC current, and converting the third AC current to the first DC current using the second converter circuit.

In some examples of the method, at least one of the first converter circuit and the second converter circuit is a multilevel converter circuit. In some examples of the method, the multilevel converter circuit is a five-level active rectifier.

In some examples of the method, converting the first DC current to the first AC current at the first output frequency using the first conversion circuit includes providing a multi-level voltage AC waveform with harmonic rejection.

In some examples, the method may further include converting the second AC current to a second DC current using a third converter circuit.

Systems, methods, and broader techniques are described herein and claimed below.

Drawings

The present examples will be better understood with reference to the following drawings:

fig. 1A shows an illustration of how a typical isolation transformer separates equipment from a power source to prevent surges and other abnormal situations.

Fig. 1B shows an EV example and a schematic diagram of how DC and AC perform charging operations.

FIG. 1C is a schematic diagram of the physical installation of a home EV charging system, the system comprising: a pole top transformer; a residential electrical inlet with a load sensor and a main circuit breaker panel; a 240VAC power cord between the panel and the device; two cable connections extending between the device and an Electric Vehicle (EV); a CAN bus connection between the EV and the device; and solar panel connections.

FIG. 1D is a block diagram illustrating a converter having multiple DC and AC ports and an off-board component panel according to one embodiment of the present disclosure.

Fig. 2 shows a circuit diagram of a converter with a 5-level topology circuit operating in rectifier mode according to a specific example of an embodiment.

Fig. 3 shows a circuit diagram of a battery device converter with a 5-level topology circuit operating in inverter mode according to one embodiment.

Fig. 4 is a schematic diagram of a power converter module with integrated switching capability and multiple DC outputs according to one embodiment.

FIG. 5 is a schematic diagram of a backplane operating with the power converter module shown in FIG. 3 according to one embodiment.

Fig. 6 shows a schematic circuit diagram of an isolated DC-DC converter according to an embodiment of the invention.

Fig. 7 shows a schematic circuit diagram of an isolated AC-DC converter according to one embodiment of the invention.

FIG. 8 illustrates a flowchart of an exemplary method disclosed in accordance with one embodiment of the present invention.

Fig. 9 is a schematic cross-sectional view of a transformer according to an embodiment of the present invention.

Detailed Description

Reference throughout this specification to "one embodiment," "an embodiment," or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment," "in an embodiment," and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

Furthermore, the described features, structures, or characteristics of the invention may be combined in any suitable manner in one or more embodiments. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. Reference will now be made in detail to the preferred embodiments of the present invention.

Fig. 1A shows a typical example of an isolated converter, and how it can prevent electrical equipment from being damaged by voltage spike power surges. Isolation between the two sides of the isolation transformer means that the input power supply is not directly connected to the parts requiring isolation and is not connected to common ground. This is more important in the case of EV vehicles. Isolation can provide both the safety required by most electric vehicle charging standards to the user and protect the electrical equipment and batteries of the EV in the event of a power network surge.

FIG. 1B shows an electric vehicle or other type of plug-in vehicle, and how DC and AC charging operates. As shown by AC charging, isolated switching is required for safety purposes. Typically, common isolated conversion cells are not efficient. The use of a 5-level packaged U-cell topology operating in bidirectional mode provides power factor correction for active converters. By using multiple conversion circuits, it is possible to achieve the more efficient isolated converter disclosed herein.

Figure 1C illustrates the physical environment of an embodiment in which separate single phase main power is delivered from a utility pole top transformer, which is the most common type of power delivery in north america. Transformers typically receive 14.4kV or 25kV single phase power from distribution lines and transformers can handle about 50 to 167kVA of power delivered to small homes or electrical entrances as split-phase 240 VAC. Each electrical inlet is typically configured to handle 100A to 200A of electricity at 240VAC, i.e., about 24kVA to 48kVA (typically assuming 1kVA is equivalent to 1 kW). As shown, the conversion device or apparatus is connected to the network via an AC connection and may be connected to a plurality of vehicles and/or solar panels. This may be achieved by the bi-directional (rectifier/inverter) nature of the device, which is provided by the ability to receive AC or DC power from one port and provide AC or DC from the other port.

Those skilled in the art will appreciate that while a single phase inlet is shown, embodiments of the present disclosure are not limited to a separate single phase 240VAC power system, and any of the embodiments disclosed herein may be adapted to work with different grids carrying AC voltage.

The electrical inlet typically comprises: an electricity meter; a main breaker rated to correspond to a total allowable load (e.g., 100A or 200A); and a panel having a circuit breaker for each household circuit that can obtain either 240VAC power or 120VAC power from the split phase 240VAC input. While most circuit breakers have a capacity between 15A and 30A, for large appliances, some circuit breakers may be lower (i.e., 10A) and some circuit breakers may be higher, such as 40A. In some countries, the capacity of the electrical inlet is low, such as 40A to 60A, and in countries where all domestic circuits are 240VAC, the power is not split phase, but conventional single phase 240VAC (the voltage levels used may vary from about 100V to 250V).

As shown in fig. 1C, the switching device/converter may be connected to the main panel circuit breaker through a circuit breaker having a larger current rating (such as 40A to 80A), although the disclosed device may consume in excess of 100A if desired. The requirements of device-specific circuit breakers are determined by electrical specifications. The current rating of the cables connecting the device to the panel is quite high. The connection to the power strip may be direct fixed wiring, or a high voltage outlet may be mounted and connected to the power strip such that the device is connected to the power strip using cables and plugs, for example, those similar to those used for appliances such as ovens or dryers. The device is shown connected to a single load sensor that senses the load experienced by the entire power strip including the device. The device cable may be a conventional device cable and plug known in the art. Further, as shown in fig. 1C, the converter may be connected to a solar panel and one or more electric vehicles. Providing electrical isolation between the solar panels and the house wiring is another benefit of the converter providing protection against lightning risks.

FIG. 1D is a block diagram illustrating an exemplary power conversion device 10 having an AC port 18, a plurality of DC and EV/DC ports 12 and 14, a DC/EV input port 16, and an offboard component panel 20. As shown in FIG. 1D, ports 12 and 14 may be connected to EVs 1 and 2, while DC/EV port 16 may be connected to a solar panel to use the DC energy generated by the panel.

In some embodiments, the converter may be adapted to receive a DC current from a first port of the plurality of DC ports (such as EV/DC port 12) and deliver a variable voltage to a second port (such as EV/DC port 14). This may be accomplished by using a plurality of switches, which may be located on the backplane 22 on the conversion circuit module 100, or on a separate switch module that may be connected to the backplane or directly to the conversion circuit module 100.

Those skilled in the art will appreciate that although the module 100 is shown as a bi-directional conversion module, any other type of module such as rectifiers, inverters, DC-DC, buck-boost modules, and surge protector modules may be used in the converter apparatus as desired.

Referring back to fig. 1D, the converter modules 100 may be connected to the backplane 22 using connectors 114 (shown here as connectors 114a, 114b, 114c, 114D, 114e, each connected to one module 100). The converter 10 may also benefit from an off-board component board 20, which in this embodiment serves the purpose of housing the inductor.

Fig. 2 shows details of an example of a type conversion circuit module 100 that may be used in a converter according to a particular embodiment. The conversion circuit 100 operating in rectifier mode may include an AC input 105, an inductive filter 110 connected in series with the AC input 105, and a 5-level topology circuit 115.

In some examples, the inductive filter 110 in this non-limiting example may be a 2.5mH inductor. Conveniently, the present design allows for a small geometry of the overall power conversion circuit 100, due in part to the small size of the inductive filter 110. The inductive filter 110 may vary according to a design selected based on the application, power rating, grid voltage harmonics, switching frequency, etc. Although the simplest such filter is a single inductor, in an alternative embodiment, the inductive filter 110 may comprise a combination of an inductor and a capacitor, such as an inductor (e.g., 2mH) connected to a capacitor (e.g., 30 muf), which itself is grounded. The choice of filter has an impact on the overall size and loss of the design, with larger filters increasing the size of the overall design and generally resulting in more loss.

The 5-level circuit may include: a high-voltage capacitor 120; at least one low voltage capacitor 125; two high voltage power switches 130a, 130b connected between the first terminal 135 and respective opposite ends 145a, 145b of the high voltage capacitor 120; two intermediate low-voltage power switches 140a, 140b, each connected between a respective one of the two opposite ends 145a, 145b of the high-voltage capacitor 120 and a respective opposite end 155a, 155b of the low-voltage capacitor; and two end low voltage power switches 150a, 150b each connected between the second input terminal 160 and a respective one of the opposite ends 155a, 155b of the low voltage capacitor 125. Operating in rectifier mode, the high voltage power switches 130a, 130b can be replaced by two diodes without affecting the way the converter circuit operates.

In some examples, the power conversion module 100 may operate in a bidirectional state or an inverter-only state using power. This means that a 5-level circuit must have high voltage power switches 130a, 130b and cannot replace them with two diodes in order to convert the voltage/current from AC to DC in rectifier mode as shown in fig. 2 or from DC to AC in inverter mode as shown in fig. 3 with AC load 202 and DC power source 206.

Details of an example of a converter module (module 100), how it works and its switching details have been disclosed by the applicant in international PCT patent application serial No. PCT/CA2018/05129, published under WO/2019/071359.

As described herein, in various embodiments, the power conversion circuit 100 may have off-board or on-board components, such as inductors and switching elements. Further, the power conversion circuit 100 may have a buck/boost circuit integrated therein.

As shown in fig. 4, in one embodiment, the power converter module 100 has integrated switching capabilities. The bi-directional switches BS1, BS2, BS3, BS4, BS5 and BS6 and the relays RE1 and RE2 allow the power converter module 100 to perform switching between the multiple DC ports 802, 804 and 806 and the onboard AC port 808 without any external switching. Ports 812 and 814 are used to connect power converter module 100 to its off-board components, which in this example are inductive filter/inductor 110 and buck/boost inductor 816 for port 814.

Fig. 5 illustrates an example of a backplane 22 that may be used by the power converter module 100 shown in fig. 4. As explained, in this embodiment, all switching can be done on the on-board module, and the backplane can connect only similar ports of cards 1-5 to each other and to the power conversion device ports. There are five series of connectors for cards 1-5, and each series of connectors has a connector 912, 910, 902, 904, 906, 908, and 914 that receives a port 812, 810, 802, 804, 806, 808, and 814, respectively, of the power converter module 100. In one embodiment, all similar ports of different cards may be connected to each other. For example, all ports 902 of cards 1 to 5 may be connected to each other.

Those skilled in the art will appreciate that while in the present embodiment, the necessary switches are present on the module 100, in some embodiments, the backplane 22 may benefit from additional switches to connect the ports to each other in different orders and combinations.

Referring to fig. 6, an isolated DC-DC converter 1002 is shown comprising a first converter 1 having on side 1006 a circuit 115 operating in inverter mode, which receives DC current and provides AC current. The converter inverter receives the DC and converts it to a DC current for use by the transformer 1004. In some embodiments, the transformer may operate at a higher frequency. Higher frequencies may lead to a reduction in the size of the transformer, which may be beneficial, especially when the isolated converter is used in an on-board vehicle.

In one embodiment, the converter 1 may operate as an inverter to generate a high frequency AC voltage waveform from the DC current it receives. Such high frequency AC voltages may range from about 400Hz up to about 4 kHz. Using a multilevel converter with power switches that switch at a frequency at least about 5 times greater, a good sinusoidal approximation AC waveform can be generated for efficient power transfer through the isolation transformer. Small transformers may also be used for step-up or step-down, or the voltages may be the same. The high frequency will allow the selection of a smaller transformer size than used in standard AC power supplies, e.g. 50Hz or 60Hz current.

Finally, the high frequency AC voltage may be rectified in a boost mode, wherein the converter 2 operates as a rectifier. In some embodiments, the converter 2 may be replaced by a diode bridge in a unidirectional application.

In this way, an electrical fault with the AC input side to ground does not provide any voltage to the output side of the transformer. In an electric vehicle, a fault to ground on the AC side may expose the vehicle chassis to the input AC voltage. Because the vehicle is insulated by its tires, a person may be exposed to dangerous electrical shock by contacting the vehicle body and providing a path to ground.

The transformer receives an AC current and has an AC output. While the transformer 1004 may contribute to other roles in the system, its primary responsibility is to provide electrical isolation between the circuits on the sides 1006 and 1008 of the transformer, which is particularly beneficial and sometimes desirable for safety purposes, such as in EV or plug-in hybrid vehicles.

The second converter 2 has a similar circuit 115 on side 1008, but it operates in rectifier mode, as described in this application. Which receives AC current from transformer 1004 and converts the current to DC current.

Furthermore, those skilled in the art will appreciate that the backplane referred to herein does not necessarily refer to a receptacle-type backplane, but may be any type of connector board. For example, all cards and ports may be connected to the backplane by wiring and connectors.

Furthermore, although the backplane is made of a separate part in the connector, the backplane does not necessarily have to be one piece and can perform the functions described above. The present schematic only relates to examples and principles in which different types of converter cards or modules may be connected to each other.

Fig. 7 shows an AC-DC isolated converter 1102 with three converters 0, 1 and 2, and three circuits 115. The converter 0 converts the AC current to DC and then feeds it to the converter 1, which converter 1 functions similarly to the converter 1 illustrated in fig. 6. Converters 0 and 1 may be on one side 1106 of transformer 1004 while converter 2 is on the other side of transformer 1004. The transformer 1004 provides electrical isolation between the two sides 1106 and 1008.

As shown in fig. 7, an AC voltage (AC input) is first converted into a DC voltage (DC input) using the converter 0 serving as a rectifier. Other aspects of the process may be similar to that explained for the DC-DC converter, including the galvanic isolation provided by the high frequency transformer 1004.

Converter 0 may be any type of converter known in the art including a diode bridge for unidirectional applications, a diode bridge and a conventional DC-DC buck or boost converter providing power factor correction (referred to as a PFC stage), an active PWM rectifier providing a PFC stage.

It can be concluded that the AC-DC isolation converter involves 3 stages as an on-board battery charger for the EV. Due to the high efficiency and high performance of the 5-level topology converter, it can replace each stage of the AC-DC isolated on-board charger to have an isolated PUC5 converter, whether bidirectional or unidirectional.

In some embodiments, the isolated AC-DC converter may be bidirectional to provide AC power from a DC power source. In one example, the battery of the EV may be used as a DC power source at the DC port to provide AC power at the AC port. This would be advantageous to provide vehicle-to-home (V-to-H) electrical power. In the present embodiment, it is preferable if all of the converters 0, 1, and 2 are the 5-level multi-layer converters disclosed herein.

In some embodiments, the isolated DC-DC converter may further include a buck converter circuit to convert DC power from opposite ends of the high voltage capacitor to a lower DC output voltage set by the charging voltage value.

In some embodiments, the isolated DC-DC or AC-DC converter may further include a boost converter circuit to convert the higher DC power from the opposite ends of the high voltage capacitor to a higher DC output voltage set by the charging voltage value. The buck/boost converter may be integrated in any of converters 0, 1 and 2.

In some embodiments, due to the nature and size of the transformer, the two intermediate low voltage power switches and the two end low voltage power switches are switched at a frequency above 10kHz and close to 20kHz or higher.

In some embodiments of the isolated AC-DC converter 1102, the first converter 0 may have a diode bridge for unidirectional applications. In some embodiments of the isolated AC-DC converter, the first converter 0 has a diode bridge and a conventional DC-DC buck or boost converter to provide power factor correction.

In some embodiments of the isolated AC-DC1102 converter, the first converter 0 has an active pulse width modulated rectifier to provide power factor correction.

The isolated AC-DC converter 1102 and DC-DC converter 1002 of the present disclosure may be used as an on-board isolation converter in an electric, hybrid, or any other type of vehicle that requires an on-board isolation converter.

In one aspect, the present disclosure provides an isolated AC-DC converter comprising: a converter operating in an inverter mode, the converter receiving a DC current and providing an AC current; a transformer that receives an AC current, having an input and an output, the transformer providing electrical isolation between the input and the output. As explained herein, the converter may be a multilevel converter.

Those skilled in the art will appreciate that converter 1 or 2 may have other components or circuits in addition to circuit 115, including multiple circuits operating in parallel, buck/boost circuits, interfaces for communication, and other possible modules and components known in the art.

Furthermore, in addition to the 5-level circuits disclosed herein, any other multi-level converter topology may alternatively be used depending on the manufacturing of the isolated DC-DC and AC-DC converters.

Those skilled in the art will appreciate that any of the embodiments disclosed herein may be used as an external converter for a home working with one or more electric vehicles, or alternatively as an internal charging mechanism for an EV as an integrated part of the EV to provide all of the above advantages.

Referring now to fig. 8, various steps of an exemplary method for providing electrical isolation are shown. Block S1802 provides a DC current to the isolated converter. In some embodiments, as described above, the DC may be received from an external source (e.g., a battery). In some other embodiments, the converter may receive a lower frequency AC current and convert it to a DC current. Block S1802 illustrates providing and selecting a frequency at which the transformer may operate. The frequency is typically selected during converter design to allow selection of the size of the transformer, as shown in block 1808. As shown in block 1808, the DC input is converted to an AC voltage of a selected frequency prior to entering the transformer. Those skilled in the art will appreciate that the desired output voltage from the transformer, as well as other factors, may also affect the size of the transformer. The transformer then provides an AC output current, which may be different or the same voltage as the input voltage, depending on the specifications of the transformer. By doing so, the AC output of the transformer has galvanic isolation from the input, thus providing safety for equipment and users.

In some examples, the AC output of the transformer may again be passed through another converter to reduce its frequency of daily use or to convert to a DC voltage.

In some examples, it may be more efficient to use a multilevel converter at one or more stages. An example of a high efficiency converter used by this converter is a five level active converter, the details of which have been disclosed by the applicant in PCT/CA2018/051291, international PCT patent application publication No. WO2019/071359, and US PG-Pub US2020/0070672 published 3/5/2020, and which is incorporated herein by reference in its entirety.

Those skilled in the art will appreciate that any type of alternating current signal (not a DC signal, such as a square wave) can be used to reduce the size of the transformer by increasing the frequency of the AC input waveform to the transformer. For example, the frequency of the AC input waveform to the transformer may be directly related to the power rating of the transformer, and thus also to the size of the transformer.

Those skilled in the art will appreciate that the transformer core should also allow for the transfer of power quantities (KVA).

In some examples, a converter operating in inverter mode may need to operate at a higher switching frequency in order to provide a high frequency voltage waveform. In some examples, the switching frequency may need to be five times the converter output frequency to be correctly modulated. For example, in some embodiments, a switching frequency of 20kHz may be required to obtain an output frequency of 4kHz from the converter, which will be received by the transformer.

Thus, the controller of the converter can operate the switch at a higher frequency to achieve the target of a higher output frequency, thereby reducing the size of the transformer.

In some examples, the following equation relates the KVA rating of a transformer to the transformer size of a single phase transformer:

rated KVA 2.22 frequency window space coefficient window area column cross-sectional area x current density 10 (-3)

As shown in fig. 9, in some examples, the area of the window 1902 and the cross-sectional area of the post 1904 are the primary dimensions of the transformer; the product of which is proportional to the size and weight of the transformer. Here, the larger the product, the larger and heavier the transformer. In the output equation, the magnetic flux density depends on the type of material used to construct the transformer core; the current density depends on the type of cooling provided; and the window spatial coefficient is constant. Therefore, the KVA rating can be considered to be proportional to the product of frequency, window area and column cross-sectional area. Or more succinctly, the KVA rating may be proportional to the product of frequency and transformer size.

For a given transformer rating, as the frequency increases, the product of the window area and the column cross-sectional area decreases, which means that the size of the transformer core and the required iron content of the core decreases. Thus, as the frequency increases, the transformer becomes lighter and smaller in size.

In some embodiments, a multi-level inverter (or converter operating in inverter mode) may help improve efficiency and provide more harmonic rejection by generating a multi-level voltage waveform for the primary of the transformer and reducing the harmonic losses and voltage/current ripple of the transformer.

In one embodiment, the use of a five-level active inverter provides higher efficiency and harmonic suppression. The use of such an inverter also allows for a reduction in the size of other passive filters (L and C) in the circuit, which is beneficial and provides for a smaller isolated converter. The applicant discloses an example of such an inverter in the international PCT patent application with serial number PCT/CA2018/051291 and publication number WO 2019/071359.

While the above description has been provided with reference to particular examples, this is for the purpose of illustration and not limitation.