Back-to-back converter system configured to provide ac or DC output

Abstract

Adaptive variable frequency drive Described herein is an electrical power conversion system for use with an alternating current (AC) source. The electrical power conversion system comprises a converter and a control system configured to receive an input indicative of a desired output from the electrical power conversion system. The control system is configured to select, based on the input, an operational mode of the converter. The operational modes comprise a first operational mode and a second operational mode. In the first operational mode, the converter is configured as an alternating current (AC) to AC converter configured to convert an input alternating current from the AC source into an AC output, the electrical power conversion system configured to provide the AC output to an AC load. In the second operational mode, the converter is configured as an AC to direct current (DC) converter configured to convert the input alternating current from the AC source into a DC output, the electrical power conversion system configured to provide the DC output to a DC load. A method for operating the electrical power conversion system is also described herein.

Description

[0001] Adaptive electrical power conversion system

[0002] Field

[0003] This relates to an adaptive electrical power conversion system for use with an alternating current (AC) source.

[0004] Background

[0005] In systems which perform electrical power conversion of an alternating current from an AC source to provide both AC and DC outputs, electrical circuits are provided to facilitate the AC to AC conversion and AC to DC conversion.

[0006] It would be desirable to provide a system and / or method which provides AC and DC output in a simple and cost-effective manner.

[0007] Summary

[0008] Described herein is an electrical power conversion system for use with an alternating current (AC) source, which depending on a selected operating mode, provides either an AC output or a DC output. A method for operating the electrical power conversion system is also described herein.

[0009] An electrical power conversion system for use with an AC source, as described herein, comprises a converter and a control system. The control system is configured to receive an input indicative of a desired output from the electrical power conversion system. The control system is further configured to select an operational mode of the converter, based on the input. The operational mode comprises: a first operational mode and a second operational mode. In the first operational mode, the converter is configured as an AC to AC converter. The AC to AC converter is configured to convert an input alternating current from the AC source into an AC output, and the electrical power conversion system is configured to provide the AC output to an AC load. In the second operational mode, the converter is configured as an AC to direct current (DC) converter. The AC to DC converter is configured to convert the input alternating current from the AC source into a DC output, and the electrical power conversion system is configured to provide the DC output to a DC load.

[0010] Previous systems require distinct electrical circuits to perform AC to AC conversion and AC to DC conversion, which can be complex to manufacture and require more electrical components, as well as requiring more involved installation, making retrofitting difficult. The disclosed electrical power conversion system in which the operational mode of the converter is selected based on the input indicative of the desired output from the electrical power conversion system can allow existing AC to AC converters to be adapted to perform AC to DC conversion through a software and / or firmware update to the control system, without any change to the underlying hardware. In this way, an adaptive electrical power conversion system can be provided in a simple and cost-effective manner.

[0011] The adaptive electrical power conversion system may therefore provide both AC to AC and AC to DC conversion in a way which is does not require the complex manufacturing, additional electrical components, and more involved installation which previous systems (with independent circuits) require. Moreover, the adaptive electrical power conversion system can be more easily retrofit to existing electrical power converters.

[0012] In some implementations, the electrical power conversion system is a variable frequency drive.

[0013] In some implementations, the AC load, to which the electrical power conversion system is configured to provide the AC output, comprises one or more electric motors, one or more heating systems, one or more ventilation systems, one or more air conditioning systems, one or more heat pumps, and / or one or more heating hot water pumps.

[0014] In some implementations, the DC load, to which the electrical power conversion system is configured to provide the DC output, comprises one or more electric vehicle charging stations, and / or one or more batteries.

[0015] In some implementations, in the first operational mode the AC to AC converter comprises a three phase inverter. In some implementations, in the second operational mode the DC to DC converter comprises an interleaved buck converter. Any suitable AC to AC and DC to DC converters can be used.

[0016] In some implementations, the input comprises one or more user inputs and / or one or more inputs from a building management system. In some implementations, the control system of the electrical power conversion system is further configured to communicate with the building management system, wherein the building management system is configured to modify the operation of the control system. Advantageously, by allowing the building management system to influence the desired output of the electrical power conversion system and / or modify the operation of the control system, the system may provide the AC and DC outputs to the respective AC and / or DC loads in a more efficient manner. For example, if the building management system determines that the AC output needs to be prioritised, then the first operational mode can be selected and therefore the building management system can ensure more efficient overall operation of the electrical power conversion system.

[0017] In some implementations, the electrical power conversion system further comprises at least one contactor, wherein the at least one contactor is configured to provide the output to either the AC load or the DC load.

[0018] In some implementations, the converter of the electrical power conversion system comprises a first stage and a second stage. The first stage and the second stage of the converter are symmetric. Optionally, the first stage and the second stage are symmetric such that the first and second stages are mirror images of each other with a component (optionally a capacitor or a bulk capacitor) in the middle. In other words, the symmetry is such that the first stage and second stage are mirror images of each other with respect to a component of the converter. In some implementations, the component of the converter is a capacitor, such as a bulk capacitor.

[0019] In some implementations, the control system of the electrical power conversion system is remote from the converter. Advantageously, by providing a control system which is remote, the operational mode of the converter and therefore the output provided by the electrical power conversion system may be selected remotely. This can allow the input to be provided to e.g. a remote server or cloud computing infrastructure.

[0020] In some implementations, the power of the output AC to the AC load is between 18 kW and 588 kW. In some implementations, the power of the output DC to the DC load is between 25 kW and 350 kW.

[0021] Also described herein is a method for operating the electrical power conversion system for use with an AC source. The method comprises receiving, at a control system of the electrical power conversion system, an input indicative of a desired output from the electrical power conversion system. The method further comprises selecting, based on the input, an operational mode of a converter. In response to selecting a first operational mode, the method further comprises configuring the converter as an AC to AC converter and converting an input alternating current from the AC source into an AC output. The method comprises providing, by the electrical power conversion system, the AC output to an AC load. In response to selecting a second operational mode, the method comprises configuring the converter as an AC to DC converter and converting the input alternating current from the AC source into a DC output. The method further comprises providing, by the electrical power conversion system, the DC output to a DC load.

[0022] Features described herein with reference to the system may be implemented as part of the method, and vice versa, in any suitable combination.

[0023] List of figures

[0024] The detailed description is with reference to the following figures.

[0025] Figure 1 is a schematic illustration of an example electrical power conversion system.

[0026] Figure 2 is an illustration of example electrical circuits for the converter. One of the example circuits depicted is configured to convert an AC input to AC output (left hand side), and another example circuit depicted is configured to convert an AC input to a DC output (right hand side).

[0027] Figure 3 is an example electrical power conversion system with additional optional components.

[0028] Figure 4 is an example method for operating the electrical power conversion system 100, such as those illustrated in Figure 1 and Figure 3, for use with an AC source 102.

[0029] Detailed description

[0030] With reference to Figure 1, an example electrical power conversion system is described. Figure 1 shows the example electrical power conversion system 100 for use with an alternating current (AC) source 102. The electrical power conversion system 100 comprises a converter 104 and a control system 110.

[0031] The control system 110 is configured to receive an input 190 indicative of a desired output from the electrical power conversion system. The control system 110 is further configured to select, based on the input 190, an operational mode of the converter 104. The operational mode comprises a first operational mode and a second operational mode. In the first operational mode, the converter 104 is configured as an AC to AC converter 104a. The AC to AC converter 104a is configured to convert an AC input from the AC source 102 into an AC output. The electrical power conversion system 100 is further configured to provide the AC output to an AC load 106.

[0032] In the second operational mode, the converter 104 is configured as an AC to direct current (DC) converter 104b. The AC to DC converter 104b is configured to convert the AC input from the AC source 102 to a DC output. The electrical power conversion system 100 is further configured to provide the DC output to a DC load 108.

[0033] The described electrical power conversion system 100 may selectively provide both AC to AC and AC to DC conversion in a way which is does not require the complex manufacturing, additional electrical components, and more involved installation which previous systems require.

[0034] In some examples, the electrical power conversion system 100 is a variable frequency drive.

[0035] In some examples, the AC load 106 may comprise one or more electric motors, one or more heating systems, one or more ventilation systems, one or more air conditioning systems, one or more heat pumps, and / or one or more heating hot water pumps.

[0036] In some examples, the power of the output AC to the AC load 106 may be between 18 kW and 588 kW.

[0037] In some examples, the DC load 108 may comprise one or more electric vehicle charging stations, and / or one or more batteries. In some examples, the power of the output DC to the DC load 108 may be between 25 kW and 350 kW.

[0038] In some examples (not shown), the control system 110 of the electrical power conversion system 100 may be remote from the converter 104. In other words, the electrical power conversion system 100 is a distributed system. Advantageously, the remote control system of the electrical power conversion system may allow the operational mode of the converter 104 be selected remotely. In this way, the output current type (AC or DC) may be selected remotely. The first and second operational modes, and the electrical circuits by which the converter 104 converts the AC input into either an AC output or a DC output are described in more detail with reference to Figure 2.

[0039] In some examples, in the first operational mode the AC to AC converter 104a comprises a three phase inverter 204a. In some examples, in the second operational mode the AC to DC converter 104b comprises an interleaved buck converter 204b. Any suitable converter may be used.

[0040] In some examples, such as that depicted in Figure 2, the converter 104 of the electrical power system comprises a first and second stage, which are symmetric. For example, in the case of the converter first mode 204a shown in Figure 2, the first stage of the converter comprises the components of the circuit to one side (e.g., the left) of component 270a (depicted as a capacitor), and the second stage of the converter comprises the components of the electrical circuit to the other side (e.g., the right) of component 270a. The same is true of converter second mode 204b, in which the first stage of the converter comprises the components to one side (e.g., the left) of component 270b (depicted as a capacitor), and the second stage of the converter comprises the components of the electrical circuit to the other side (e.g., the right) of component 270b. In other words, the symmetry of the first and second stage is such that the first stage and second stage are mirror images of each other with respect to component (270a) of the converter 104. In some examples, component (270a) is a capacitor or a bulk capacitor.

[0041] As can be seen, the hardware of the converter 104 is identical in both modes 104a, 104b; the operational mode is varied by changing the control arrangement of the switches within the converter 104 by the control system, as discussed below in more detail.

[0042] In the specific example of Figure 2, in the first operational mode the AC to AC converter 104a comprises a three phase inverter 204a. In the second operational mode the AC to DC converter 104b comprises an interleaved buck converter 204b. Graphs 220a and 220b illustrate examples of the current output by the three phase converter 204a (AC to AC converter) and by the interleaved buck converter 204b (AC to DC converter), respectively. In graphs 220a and 220b, the axes 212a and 212b represent the output voltage of the electrical circuits 204a and 204b, respectively, and the axes 212a and 212b represent time. In graph 220a, an example AC output of the three phase converter 204a is illustrated as the three phase signals which alternate sinusoidally. In graph 202b, an example DC output of the interleaved converter 204b is illustrated as the substantially flat signal.

[0043] The adaptive electrical power conversion system 100 described with reference to Figures 1 and Figure 2 may selectively change, based on the input indicative of the desired output, the configuration of the converter 104 between the three phase converter 204a and an interleaved buck converter 204b. Although the underlying hardware remains fixed, as shown in Figure 2 with reference to converter 104a, 104b, the control system can vary the operational order and control of the switches within the converter 104 to provide the desired output. In other words, a control algorithm of the converter can be changed or selected depending on the selected operational mode to provide an AC or DC output as required. The control algorithm can be changed or updated through a software or firmware updated of the control system, obviating the need to modify hardware of the converter. In some examples, the control algorithm can work by either employing Space Vector Modulation (SVM) or interleaved buck converter control interchangeably. In some examples, the control algorithm can modify the switching frequency to suit the application.

[0044] In this way, an adaptive electrical power conversion system is provided. The adaptive electrical power conversion system may not require the complex manufacturing, additional electrical components, and more involved installation which previous systems require. Moreover, since no hardware modifications are needed to the converter, the device can be retrofit.

[0045] In some examples, the electrical power conversion system comprises at least one contactor. In the example illustrated in Figure 2, the electrical power conversion system comprises a contactor 230 and a contactor 232. The contactor 230 is configured to provide the AC output of the converter 204a to an AC load (not depicted in Figure 2). The contactor 232 is configured to provide the DC output of the converter 204b to a DC load (no depicted in Figure 2).

[0046] In some examples, the converter modes 204a and 204b are configured such that different operation of the switches of the two electrical circuits depicted in Figure 2 result in their respective AC to AC and DC to DC electrical power conversion. In some examples, the contactors 230, 232 are configured such that different operation of switches of the contactors result in providing the output electrical power to the corresponding electrical load. The contactors 230, 232 can be controlled by the control system in accordance with one or more control algorithms, along with the converter 104, to provide the desired output type from the system 100.

[0047] Figure 3 depicts an example electrical power conversion system with additional optional components. Figure 3 shows an electrical power conversion system 300 for use with an alternating current source 302. System 300 is an example of system 100 in Figure 1, and AC source 302 is an example of source 102.

[0048] The electrical power conversion system 300 is configured to provide an AC output to an AC load 306, 342. AC loads 306, 342 are examples of AC load 106. In the example depicted in Figure 3, the AC load comprises one or more electric motors 306. The AC load further comprises electrical infrastructure of a building and a building management system 342. In other examples, the AC load may additionally or alternatively comprise: one or more heating systems, one or more ventilation systems, one or more air conditioning systems, one or more heat pumps, and / or one or more heating hot water pumps.

[0049] The electrical power conversion system 300 is configured to provide a DC output to a DC load 308. DC load is an example of load 108. In the example depicted in Figure 3, the DC load comprises one or more electric vehicle charging stations. In other examples, the DC load may additionally or alternatively comprise one or more batteries.

[0050] In the example illustrated in Figure 3, a control system 340 is configured to receive an input 190 indicative of a desired output from the electrical power conversion system. Control system 340 is an example of control system 110. The control system 340 is configured to select, based on the input, an operational mode of the converter 304 of the electrical power conversion system 300. The control system can be remote from the converter 304. The converter 304 is an example of converter 104.

[0051] In some examples, the input indicative of a desired output from the electrical power conversion system comprises one or more user inputs and / or one or more inputs from a building management system 342. In some examples, the control system 340 is configured to communicate with the building management system 342, and the building management system 342 is configured to modify the operation of the control system 340. Advantageously, the building management system may allow the AC and DC outputs to the respective AC and DC loads to be provided in a more efficient manner. For example, in some examples the DC load comprises one or more batteries. The building management system 342, based on receiving data indicating that the one or more batteries have been fully charged by the DC output of the system 300, modifies the operation of the control system 340 to provide an AC output to the AC load 306. The building management system can thus ensure more efficient operation of the electrical power conversion system 300.

[0052] In some examples, the electrical power conversion system comprises at least one contactor 330, 332, which are configured to provide the output to either the AC load 306 or the DC load 308. In the example illustrated in Figure 3, the electrical power conversion system 300 comprises a contactor 330, which is configured to provide the DC output to the DC load 308, and a contactor 332, which is configured to provide the AC output to the AC load 306 to the AC load 306.

[0053] In the example depicted in Figure 3, data 350 comprising an update for the operation of the electrical power conversion system 300 is shown. The data 350 is configured to modify the operation of the electrical power conversion system 300 through a software and / or firmware change. In some examples, the data 350 comprises an update which, when provided to any electrical power conversion system, modifies the control (or control algorithm) of a converter 104 of the electrical power conversion system such that the converter 104 can perform the different operational modes described herein. In some examples, the data 350 can be provided to the electrical power conversion system 300 through a wired connection and / or a wireless connection. The data 350 can be applied to the control system 340.

[0054] Advantageously, the data 350 allows any existing electrical power conversion system to be reconfigured such that it can provide an AC output and a DC output, and hence an adaptive electrical power conversion system is provided. The adaptive electrical power conversion system can avoid the drawbacks of previous systems, which may require distinct electrical circuits to perform AC to AC conversion and AC to DC conversion, and consequently can be complex to manufacture and require more electrical components, as well as requiring more involved installation, making retrofitting difficult. The system can therefore be more easily retrofit to existing devices, since extensive hardware changes are not required. In the example in which the data 350 is provided to the electrical power conversion system 300 through a wireless connection, the electrical power communication system may be configured to communicate via any suitable wireless communication protocol, including but not limited to, any cellular connection (e.g., 2G, 3G, 4G, 5G), a Wi-Fi connection, a Bluetooth connection, a Bluetooth Low Energy BLE connection, a Zigbee connection, or the like.

[0055] In some examples, the electrical power conversion system may be a variable frequency drive. In examples in which the electrical power conversion system is a variable frequency drive (VFD), the data 350 modifies the control of the VFD, such that a converter of the VFD can perform the operational modes described herein.

[0056] With reference to Figure 4, an example method 400 for operating the electrical power conversion system 100, 300, such as those illustrated in Figure 1 and Figure 3, is shown. The method comprises receiving 402, at a control system 110 of the electrical power conversion system 100, an input 190 indicative of a desired output from the electrical power conversion system. The method further comprises selecting 404, based on the input, an operational mode of a converter 104.

[0057] In response to selecting the first operational mode, the method further comprises configuring 406a the converter 104 as an AC to AC converter 104a, and converting an input alternating current from an AC source 102 into an AC output. The method further comprises providing 408a, by the electrical power conversion system 100, the AC output to an AC load 106.

[0058] In response to selecting the second operational mode, the method further comprises configuring 406b the converter 104 as an AC to DC converter 104b, and converting the input alternating current from the AC source 102 into a DC output. The method further comprises providing 408b, by the electrical power conversion system 100, the DC output to a DC load 108.

[0059] This method for operating the electrical power conversion system, which in some examples may be a variable frequency drive, provides an adaptive method for both AC to AC and AC to DC electrical power conversion. The adaptive method can avoid the more complex manufacturing and installations which previous systems can require.

[0060] Described herein is an electrical power conversion system for use with an alternating current (AC) source. The electrical power conversion system comprises a converter and a control system configured to receive an input indicative of a desired output from the electrical power conversion system. The control system is configured to select, based on the input, an operational mode of the converter. The operational modes comprise a first operational mode and a second operational mode. In the first operational mode, the converter is configured as an alternating current (AC) to AC converter configured to convert an input alternating current from the AC source into an AC output, the electrical power conversion system configured to provide the AC output to an AC load. In the second operational mode, the converter is configured as an AC to direct current (DC) converter configured to convert the input alternating current from the AC source into a DC output, the electrical power conversion system configured to provide the DC output to a DC load. A method for operating the electrical power conversion system is also described herein.

Claims

Claims1. An electrical power conversion system (100) for use with an alternating current (AC) source (102), comprising: a converter (104); and a control system (110) configured to receive an input (190) indicative of a desired output from the electrical power conversion system (100), and wherein the control system (110) is configured to select, based on the input (190), an operational mode of the converter (104), the operational modes comprising: a first operational mode, wherein the converter (104) is configured as an alternating current (AC) to AC converter (104a) configured to convert an input alternating current from the AC source (102) into an AC output, the electrical power conversion system (100) configured to provide the AC output to an AC load (106); and a second operational mode, wherein the converter (104) is configured as an AC to direct current (DC) converter (104b) configured to convert the input alternating current from the AC source (102) into a DC output, the electrical power conversion system (100) configured to provide the DC output to a DC load (108).

2. The electrical power conversion system (100) of claim 1, wherein the electrical power conversion system (100) is a variable frequency drive, VFD.

3. The electrical power conversion system (100) of any preceding claim, wherein the AC load (106) comprises one or more electric motors (306), one or more heating systems, one or more ventilation systems, one or more air conditioning systems, one or more heat pumps, and / or one or more heating hot water pumps.

4. The electrical power conversion system (100) of any preceding claim, wherein the DC load (108) comprises one or more electric vehicle charging stations (308), and / or one or more batteries.

5. The electrical power conversion system (100) of any preceding claim, wherein in the first operational mode the AC to AC converter (104a) comprises a three phase inverter (204a).

6. The electrical power conversion system (100) of any preceding claim, wherein in the second operational mode the AC to DC converter (104b) comprises an interleaved buck converter (204b).

7. The electrical power conversion system (100) of any preceding claim, wherein the input (190) comprises one or more user inputs and / or one or more inputs from a building management system.

8. The electrical power conversion system (100) of claim 6, wherein the control system (110) is configured to communicate with the building management system (342), wherein the building management system is configured to modify the operation of the control system (110).

9. The electrical power conversion system (100) of any preceding claim, further comprising at least one contactor (330, 332) configured to provide the output to either the AC load (106) or the DC load (108).

10. The electrical power conversion system (100) of any preceding claim, wherein the converter (104) comprises a first stage and a second stage, and wherein the first stage and second age are symmetric.

11. The electrical power conversion system (100) of claim 10, wherein the symmetry is such that the first stage and second stage are mirror images of each other with respect to a component (270a) of the converter (104), wherein optionally the component (270a) is a capacitor.

12. The electrical power conversion system (100) of any preceding claim, wherein the control system (110) is remote from the converter (104).

13. The electrical power conversion system (100) of any preceding claim, wherein the power of the output AC to the AC load (106) is between 18 kW and 588 kW.

14. The electrical power conversion system (100) of any preceding claim, wherein the power of the output DC to the DC load (108) is between 25 kW and 350 kW.

15. A method (400) for operating an electrical power conversion system (104) for use with an alternating current (AC) source (102), the method comprising:receiving (402), at a control system (110) of the electrical power conversion system (100), an input (190) indicative of a desired output from the electrical power conversion system (100); selecting (404), based on the input (190), an operational mode of a converter (104); in response to selecting a first operational mode, configuring (406a) the converter as an AC to AC converter (104a), converting an input alternating current from the AC source (102) into an AC output, and providing (408a), by the electrical power conversion system, the AC output to an AC load (106); and in response to selecting a second operational mode, configuring (406b) the converter as an AC to DC converter (104b), converting the input alternating current from the AC source (102) into a DC output, and providing (408b), by the electrical power conversion system, the DC output to a DC load (108).

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