Converter system and control method thereof

Abstract

The invention provides a converter system and a control method thereof. The converter system includes a first converter including a first AC side having a first frequency and a second AC side having a second frequency, the first converter including a converter having a plurality of branches; a plurality of second converter units configured to be coupled between the first converter and the plurality of DC units, each DC unit of the plurality of DC units being a DC load or a DC source; and a controller configured to control at least one of the first converter and the at least one second converter unit to control power provided to or by at least one of the plurality of DC units.

Description

Converter System and Control Method Technical Field

[0001] This invention relates to a converter system and a control method for controlling the converter system. Background Technology

[0002] A converter can convert alternating current (AC) to direct current (DC) and vice versa. A converter can change the voltage or frequency of a current, or perform a combination thereof. Converters include matrix converters, which are AC-AC converters with a controlled array of power switches. The characteristics of matrix converters are highly attractive, and these characteristics have been studied and are closer to industrial applications.

[0003] In recent years, cascading matrix converters with rectifiers to form converter systems applicable to DC applications has become a hot topic in power electronics research. However, existing technologies for such converter systems still have room for improvement. For example, issues such as complex structure, high cost, and large footprint need to be addressed. Summary of the Invention

[0004] According to one aspect of the present invention, a converter system is provided, comprising: a first converter including a first AC side having a first frequency and a second AC side having a second frequency, the first converter including a converter having a plurality of branches; a plurality of second converter units configured to be coupled between the first converter and a plurality of DC units, each of the plurality of DC units being a DC load or a DC source; and a controller configured to control the first converter and at least one of the at least one of the second converter units to control the power supplied to or by the at least one of the plurality of DC units.

[0005] In one embodiment, the first frequency is the power frequency; and the second frequency is greater than the first frequency, and the range of the second frequency is 100Hz to 10kHz.

[0006] In one embodiment, the converter is a matrix converter and has a first terminal coupled to at least two phases; the plurality of branches include a first group of branches and a second group of branches, the first group of branches including branches coupled to one of the at least two phases, the second group of branches including branches coupled to the other of the at least two phases; and one of the branches in the first group of branches is configured to be combined by phase or by potential with a corresponding branch included in the second group of branches.

[0007] In one embodiment, the converter is a matrix converter and includes nine branches, each branch including one or more modules and a branch inductor connected in series with the one or more modules. Each branch has a first terminal coupled to one of three phases a, b, c and a second terminal coupled to one of three phases x, y, z of the matrix converter. The nine branches include a first to a ninth branch; the first terminals of the first, second, and third branches are coupled to phase a of the first terminal; the second terminals of the first, fourth, and seventh branches are coupled to phase x of the second terminal; the first terminals of the fourth, fifth, and sixth branches are coupled to phase b of the first terminal; the second terminals of the second, fifth, and eighth branches are coupled to phase y of the second terminal; and the first terminals of the seventh, eighth, and ninth branches are coupled to phase c of the first terminal; and the second terminals of the third, sixth, and ninth branches are coupled to phase z of the second terminal.

[0008] In one embodiment, the matrix converter further includes nine branch switches, each branch switch being arranged on a corresponding branch of the nine branches; and wherein the controller is configured to control one or more of the nine branch switches to clear the fault in the event of a fault in at least one of the nine branches.

[0009] In one embodiment, the converter is a matrix converter and includes six branches, each branch including one or more modules and a branch inductor connected in series with the one or more modules. Each branch has a first terminal of one of three phases a, b, c coupled to a first terminal of the matrix converter and a second terminal of one of three phases x, y, z coupled to a second terminal of the matrix converter. The six branches include a first to a sixth branch, the first terminals of the first and sixth branches being coupled to phase a of the first terminal, and the second terminals of the first and second branches being coupled to phase x of the second terminal; the first terminals of the second and third branches being coupled to phase b of the first terminal, and the second terminals of the third and fourth branches being coupled to phase y of the second terminal; and the first terminals of the fourth and fifth branches being coupled to phase c of the first terminal, and the second terminals of the fifth and sixth branches being coupled to phase z of the second terminal.

[0010] In one embodiment, the converter is a matrix converter and includes twelve branches, each branch including one or more modules and a branch inductor connected in series with the one or more modules; the twelve branches include first to sixth branches constituting a first part and seventh to twelfth branches constituting a second part; each branch of the first part has a first terminal of one of three phases a, b, c coupled to a first terminal of the matrix converter, and each branch of the second part has a first terminal of one of three phases x, y, z coupled to a second terminal of the matrix converter; the first terminals of the first and fourth branches are coupled to phase a of the first terminal, and the first terminals of the second and fifth branches are coupled to phase a of the first terminal. The first ends of the first branch and the sixth branch are coupled to the first phase of the first terminal; the first ends of the seventh branch and the tenth branch are coupled to the x phase of the second terminal; the first ends of the eighth branch and the eleventh branch are coupled to the y phase of the second terminal; and the first ends of the ninth branch and the twelfth branch are coupled to the z phase of the first terminal; the first branch to the third branch each have a second end coupled to the first connection point; and the seventh branch to the ninth branch each have a second end coupled to the first connection point; and the fourth branch to the sixth branch each have a second end coupled to the second connection point; and the tenth branch to the twelfth branch each have a second end coupled to the second connection point.

[0011] In one embodiment, the converter is a matrix converter and includes six branches, each branch including one or more modules and a branch inductor connected in series with the one or more modules; the six branches include a first branch to a sixth branch, each branch having a first terminal of one of three phases a, b, c coupled to a first terminal of the matrix converter; the first terminals of the first branch and the fourth branch are coupled to phase a of the first terminal, and the first terminals of the second branch and the fifth branch are coupled to phase b of the first terminal, and the first terminals of the third branch and the sixth branch are coupled to phase c of the first terminal; and each of the first branch to the third branch has a second terminal coupled to a first connection point, and each of the fourth branch to the sixth branch has a second terminal coupled to a second connection point.

[0012] In one embodiment, the converter system further includes a plurality of filters, each filter being coupled between one of the plurality of second converter units and one of the plurality of DC units.

[0013] In one embodiment, the converter system further includes a transformer unit coupled between the first converter and a plurality of second converter units.

[0014] In one embodiment, the transformer unit includes a plurality of transformers, each transformer being coupled between a first converter and one of a plurality of second converter units.

[0015] In one embodiment, the transformer unit includes a transformer having a primary winding and a plurality of secondary windings, each secondary winding being coupled to one of a plurality of second converter units.

[0016] In one embodiment, the controller is configured to receive feedback information from at least one of a first converter, at least one of a plurality of second converter units, and at least one of a DC unit coupled to the at least one second converter unit, and control the first converter and at least one of the at least one second converter unit based on the feedback information.

[0017] In one embodiment, the converter system is operable in one of the following operating modes: a first operating mode in which power is transferred from an AC source coupled to a first side of a first converter to one or more DC units of a plurality of DC units; a second operating mode in which power is transferred from one or more DC sources of a plurality of DC units to the first AC side; a third operating mode in which at least one of a plurality of second converter units is configured to receive power from a first converter and at least another of a plurality of second converter units; and a fourth operating mode in which at least one of a plurality of second converter units is configured to receive power from at least another of a plurality of second converter units, or to receive power from both a first converter and the at least another second converter unit operated to isolate at least one faulty branch of a plurality of branches.

[0018] In one embodiment, the controller is included in the first converter.

[0019] In one embodiment, the plurality of second converter units have a common local controller, wherein the controller is contained within the common local controller.

[0020] In one embodiment, the first converter includes a local control unit, and each second converter unit includes a local control unit; and the controller communicates with each local control unit for coordinated control of the first converter and the plurality of second converter units.

[0021] In one embodiment, the controller is configured to control at least one of a first converter and at least one second converter unit such that the voltage or current used to supply power to or receive power from at least one of a plurality of DC units is adjusted based on configuration adjustment values ​​and operating modes for the converter system.

[0022] In one embodiment, the controller is configured to: determine the amount of electricity received from the first converter unit and the amount of electricity received from the at least one second converter unit according to a preset configuration value when the converter system is in a third operating mode.

[0023] According to another aspect of the present invention, a control method is provided for controlling a converter system, the converter system including a first converter and a plurality of second converter units, the first converter including a first AC side having a first frequency and a second AC side having a second frequency, the first converter including a converter having a plurality of branches, the plurality of second converter units being configured to be coupled between the first converter and a plurality of DC units, each of the plurality of DC units being a DC load or a DC source, the control method comprising: controlling at least one of the first converter and at least one of the second converter units to control the power supplied to or by at least one of the plurality of DC units.

[0024] According to another aspect of the invention, a power supply system for supplying power to an electrolytic cell is provided, the power supply system comprising the converter system described above. Attached Figure Description

[0025] The following description of the accompanying drawings of the embodiments or implementations further illustrates and explains various aspects of the conversion system and control method. Devices, apparatuses, modules, and blocks having the same structure and effects appear with equivalent reference numerals. In different drawings, descriptions of each of the devices, apparatuses, modules, and blocks will not be repeated in the following drawings as long as they correspond to each other in their functionality.

[0026] Figure 1 is a schematic block diagram of a converter system according to an embodiment of the present invention.

[0027] Figure 2-8 shows an embodiment of the converter system in Figure 1.

[0028] Figures 9-12 are exemplary circuits of the first converter in the converter system of Figure 1.

[0029] Figures 13-15 are exemplary circuits of the second converter unit in Figure 1.

[0030] Figure 16 is a schematic flowchart of a control method according to an embodiment of the present invention.

[0031] Figures 17-21 illustrate embodiments of the main steps of the control method in Figure 16. Detailed Implementation

[0032] OverviewEmbodiments of the present invention relate to a converter system and a control method for controlling the converter system. The converter system includes a first converter coupled to an AC source, a second converter coupled between the first converter and a plurality of DC units (DC units), and a controller for controlling at least one of the first and second converters. Each of the plurality of DC units is a DC load or a DC power supply. The controller controls the converter system based on feedback information from the first converter, the second converter, and at least one of the at least one DC unit, such that the converter system can provide the most suitable conversion for the DC application in the current scenario.

[0033] The converter system has four operating modes. The converter system can be operated in one of these four operating modes. The four operating modes include operating modes one through four. In the first operating mode, power is transferred from an AC source coupled to a first side of the first converter to one or more DC units of a plurality of DC units. In the second operating mode, power is transferred from one or more DC sources of a plurality of DC units to the first AC side. In the third operating mode, at least one of the plurality of second converter units is configured to receive power from the first converter and at least another of the plurality of second converter units. In the fourth operating mode, at least one of the plurality of second converter units is configured to receive power from at least another of the plurality of second converter units, or to receive power from both the first converter and the at least another second converter unit, which are operated to isolate at least one faulty branch of a plurality of branches.

[0034] The first to third operating modes can be applied to scenarios where the power grid coupled to the AC source is in normal operating condition; therefore, the first to third operating modes can be considered normal modes. The fourth operating mode can be applied to scenarios where at least one module included in the power grid or a branch of the first converter is in a fault state; therefore, the fourth operating mode can be considered a fault mode.

[0035] This converter system has the advantages of compact structure, high level of intelligence and low cost.

[0036] In one embodiment, the converter system is a transformerless system, which enables flexibility in connection and handling fault conditions.

[0037] In one embodiment, the first converter has multiple branches, each of which can be controlled to provide power transfer. Thus, by controlling one of the multiple branches, excess power can be transferred to the DC unit coupled to that branch. This is particularly useful when the DC unit is an energy storage device such as a battery.

[0038] Exemplary System Figure 1 schematically illustrates a converter system 100 according to an embodiment of the present invention. The converter system 100 is coupled between an AC source 200 and a plurality of DC units 301 to 30n.

[0039] Referring to Figure 1, AC source 200 is, for example, a medium-voltage AC source (MVAC). As shown by the boxes connected to AC source 200 by dashed lines, AC source 200 can be coupled to the AC grid via a transformer, coupled to the DC grid via a DC-AC converter, or coupled to renewable energy via a DC-AC converter or AC-AC converter.

[0040] Multiple DC units may include one or more DC loads, such as one or more electrolyzers. In one embodiment, a DC load may be implemented as including one electrolyzer (e.g., DC load 301). A DC load may also be implemented as including multiple electrolyzers connected in series, parallel, or a combination thereof (e.g., DC load 30n). Multiple DC units may also include one or more DC sources used as energy storage components. Such DC sources may include one or more of PV, battery, fuel cell, or bidirectional electrolyzer.

[0041] The converter system 100 can convert alternating current (AC) from an AC source 200 into direct current (DC) suitable for powering a DC load. The converter system 100 can also convert direct current (DC) from a DC source back into alternating current (AC) and transmit that AC to the AC source 200. The converter system 100 can also operate to provide energy stored in an energy storage component (e.g., a DC source or a DC load).

[0042] The converter system 100 has four operating modes, namely, operating mode 1 through operating mode 4. Each operating mode is described below.

[0043] When the converter system 100 is in the first operating mode, AC from the AC source 200 is converted to DC to supply power to a DC load. For example, in the first operating mode, the converter system 100 is operated to supply power to an electrolytic cell.

[0044] When the converter system 100 is in the second operating mode, energy stored in one or more DC sources is transferred to the AC source 200. In one application scenario of the second operating mode, energy stored in an EV (electric vehicle) or battery storage system can be returned to the AC source 200 or other devices. In another application scenario of the second operating mode, energy stored in renewable energy sources can be transferred to the AC source 200. In one embodiment, in the second operating mode, the converter system 100 is operated as a distributed grid-connected inverter system.

[0045] When the converter system 100 is in the third operating mode, the DC load can be powered by both the AC source 200 and one or more DC sources. This third operating mode can be referred to as a hybrid mode. This is particularly suitable when one or more DC power sources are renewable energy sources. For example, in the third operating mode, the electrolyzer is powered primarily by renewable energy sources, but can also be supplemented by AC power source 200.

[0046] When the converter system 100 is operating in the fourth operating mode, the DC load can be powered by one or more DC sources. This can be applied in fault conditions. An example of applying the fourth operating mode to fault conditions is described below.

[0047] In one embodiment, when the power grid coupled to AC source 200 is in a faulty state or temporarily unavailable, and thus AC source 200 is unable to supply power to the DC load, one or more DC sources can supply power to the DC load, thereby maintaining the DC load's ability to be powered for a period of time. For some DC loads, such as electrolytic cells, if the power supply suddenly stops or the power supplied is less than a certain percentage of its rated power, a restart is required. In this case, operating the converter system 100 in a fourth operating mode can solve this problem.

[0048] In another embodiment, the fault occurs in at least one branch of the first converter (e.g., one or more branches are faulty branches, or one or more modules of a branch are faulty modules, in which case the branch is the faulty branch). In this case, the first converter is operated to isolate the faulty branch. Therefore, the DC load can receive power from the first converter with the faulty branch isolated, as well as power from one or more DC sources. In other words, at least one of the plurality of second converter units receives power from the first converter with the faulty branch isolated, and at least another of the plurality of second converter units.

[0049] Referring again to Figure 1, the converter system 100 includes a first converter 10, a second converter 20 cascaded with the first converter 10, and a controller 30 that communicates with the first converter 10, the second converter 20, and a plurality of DC units.

[0050] The first converter 10 includes a first AC side 10A and a second AC side 10B. The first AC side 10A provides a first AC current having a first frequency (f1). The second AC side 10B provides a second AC current having a second frequency (f2). The first converter 10 can convert the first AC current of the first frequency to the second AC current of the second frequency. The first converter 10 can also convert the second AC current of the second frequency back to the first AC current of the first frequency. The first converter 10 is an AC-AC converter. The first converter 10 may include, for example, a matrix converter with multiple branches.

[0051] The second converter 20 is coupled between the first converter 10 and a plurality of DC units 301-30n. The second converter 20 includes a plurality of second converter units 21-2n. The plurality of second converter units can be implemented as a plurality of individual converters or integrated as a modular converter. In one embodiment, each second converter unit is implemented as a rectifier and performs AC-DC conversion (e.g., converter system 100 is in a first operating mode). In another embodiment, each second converter unit is implemented as an inverter and performs DC-AC conversion (e.g., converter system 100 is in a second operating mode). In yet another embodiment, the plurality of second converter units include one or more rectifiers and one or more inverters (e.g., converter system 100 is in a third operating mode).

[0052] Each of the plurality of second converter units is coupled between the first converter 10 and a DC load or a DC source. Each of the plurality of second converter units has a first terminal coupled to the first converter 10 and a second terminal coupled to the DC load or DC source. For example, as shown in FIG1, second converter unit 21 has a first terminal 21A coupled to the first converter 10 and a second terminal 21B coupled to the DC load 301. Second converter unit 22 has a first terminal 22A coupled to the first converter 10 and a second terminal 22B coupled to the DC source 302, and so on. Second converter unit 2n has a first terminal 2nA coupled to the first converter 10 and a second terminal 2nB coupled to the DC load 30n. It should be understood that each of the plurality of second converter units 21 to 2n can be connected to the first converter 10 via an AC bus or directly.

[0053] In one embodiment, an on / off switch may be provided between the second converter unit and the DC unit coupled to the second converter unit, so that the DC unit can be disconnected from the converter system 100 by operating the on / off switch.

[0054] The following describes an embodiment of the second converter unit.

[0055] In one embodiment, the second converter unit can be implemented as a thyristor-based rectifier, which is a semi-controlled device. In this embodiment, the second converter unit can provide an adjustable DC voltage to a DC load such as an electrolytic cell.

[0056] In another embodiment, the second converter unit can be implemented as a diode-based rectifier, which is an uncontrollable device. In this embodiment, the second converter unit can provide a fixed DC voltage (i.e., an unadjustable DC voltage) to a DC load such as an electrolytic cell.

[0057] In yet another embodiment, the second converter unit is implemented as including a diode-based rectifier and a DC-DC converter coupled to the rectifier, wherein the diode-based rectifier is an uncontrolled device and the DC-DC converter is a controlled device. In this embodiment, the second converter unit can provide an adjustable DC voltage to a DC load such as an electrolytic cell.

[0058] In another embodiment, the second converter unit is implemented as an active rectifier. In this embodiment, the second converter unit is capable of providing AC-DC conversion in one direction (i.e., acting as a rectifier) ​​and DC-AC conversion in the other direction (i.e., acting as an inverter).

[0059] It should be understood that multiple second converter units may include two or more types of converters as described above.

[0060] The controller 30 controls the first converter 10 and / or at least one second converter unit based on feedback information. The feedback information may include measurement information (e.g., measured current and / or measured voltage) obtained by sensors (e.g., current sensors and / or voltage sensors) arranged in the converter system 100. For clarity, sensors are shown in FIG. 2 by gray hollow circles and gray solid circles. As shown in FIG. 2, the sensors are arranged in the converter system 100, whereby the feedback information can be generated within the converter system 100. The feedback information may also include status information obtained by a monitoring system (not shown) for monitoring the status of each of the plurality of DC units. The monitoring system may include a plurality of monitoring units, each coupled to one of the plurality of DC units and monitoring the status of the coupled DC unit.

[0061] It should be understood that the state of each DC unit can also be determined based on measurement information (e.g., measured voltage and / or measured current at the branch between each second converter unit and the corresponding DC unit). Therefore, the state of each DC unit is also available within the converter system 100.

[0062] In one embodiment, the feedback information includes one or more of the following: 1) feedback information from a first side 10A of the first converter 10 (e.g., measured current and / or measured voltage measured at the first side 10A); 2) feedback information from each of the plurality of branches of the matrix converter (e.g., measured current measured at each of the plurality of branches of the matrix converter); 3) feedback information from a second side 10B of the first converter 10 (e.g., measured current and / or measured voltage measured at the second side 10B); 4) feedback information from each of the multiple second converter units connecting the first converter 10 and the multiple second converter units. Feedback information from each branch of the first converter 10 (e.g., measured current and / or measured voltage at the branch connecting the first converter 10 and each of the plurality of second converter units); 5) Feedback information from each branch connecting each of the plurality of second converter units to the corresponding DC unit (e.g., measured current and / or measured voltage at each branch connecting each of the plurality of second converter units to the corresponding DC unit); 6) Feedback information from one or more of the plurality of DC units (e.g., the status of each DC unit detected by a status monitoring system associated with the plurality of DC units). When the DC load is an electrolyzer, the status of the electrolyzer can include the degree of aging, aging rate, hydrogen production rate, and operating efficiency of the electrolyzer. The status of the electrolyzer can be determined by calculating the current and voltage of the electrolyzer.

[0063] The controller 30 can provide a first control signal CS_1 to the first converter 10 based on the received feedback information to control the conversion operation of the first converter 10. For example, under the control of the first control signal, the first converter 10 is operated to convert the first AC of the first side 10A into the second AC of the second side 10B, or to convert the second AC of the second side 10B into the first AC of the first side 10A.

[0064] The controller 30 can provide a second control signal CS_2 to the second converter 20 based on the received feedback information to control the conversion operation of each of the second converters 20. For example, under the control of the second control signal, each of the plurality of second converter units can be operated to perform rectification or inversion operations. When the second converter unit is implemented as a controllable device, the DC voltage output by the second converter unit can be adjusted under the control of the second control signal.

[0065] In one embodiment, as shown in FIG3, the controller 30 is implemented as a high-level controller (e.g., a central controller), the first converter 10 includes a local control unit 11, and each second converter unit includes a local control unit. For example, second converter unit 21 includes a local control unit 211, second converter unit 22 includes a local control unit 221, and so on, second converter unit 2n includes a control unit 2n1. In this embodiment, the controller 30 is communicatively connected to the local control unit 11 of the first converter 10 to send a first control signal to the local control unit 11, and the local control unit 11 operates the first converter 10 according to the first control signal. The controller 30 is also communicatively connected to the local control unit of each second converter unit to send a second control signal to the local control unit, and the local control unit operates the second converter unit according to the second control signal. This enables coordinated control of the first and second converters. Furthermore, independent control of the power supply to each DC load is also possible. In this embodiment, the controller 30 and the local control units can form a distributed control system.

[0066] In another embodiment, the controller 30 is included in the first converter 10. For example, the controller 30 is integrated with the local control unit 11 of the first converter 10. In this way, the local control unit of the first converter 10 can control the first converter unit 10, and can also control multiple second converter units 21 to 2n.

[0067] In yet another embodiment, the plurality of second converter units 21-2n have a common local controller (not shown). In one implementation of this embodiment, controller 30 is included in the common local controller. Thus, the common local controller can control both the plurality of second converter units 21-2n and the first converter 10.

[0068] Depending on various configurations of the controller, local control unit, and common local controller, the coordinated control of the converter system 100 can be achieved by operating the first converter and / or one or more second converter units through at least one control signal.

[0069] The controller 30 can be implemented in hardware, software, or a combination of both. For the hardware implementation, it can be implemented in one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), data signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, electronic units designed to perform their functions, or combinations thereof. For the software implementation, it can be implemented using microcode, program code, or code segments, and can also be stored in a machine-readable storage medium such as a storage component.

[0070] In one embodiment, the controller 30 may be implemented including a memory and a processor. Instructions are stored in the memory that, when executed by the processor, cause the processor to perform the control method according to an embodiment of the invention.

[0071] Figure 4-8 illustrates an embodiment of the converter system 100.

[0072] According to an embodiment of the invention, as shown in Figures 4 and 5, the converter system 100 further includes a transformer unit 40 coupled between the first converter 10 and the second converter 20. This configuration of the converter system 100 is advantageous. For example, when the first converter 10 is operated to convert a first AC on a first side 10A into a second AC on a second side 10B, the first side 10A is the input side and the second side 10B is the output side. The output voltage of the first converter 10 has an optimal voltage, i.e., the first converter 10 has an optimal output voltage. Furthermore, because the converter system 100 needs to provide a voltage suitable for supplying a DC load, the output voltage of the first converter 10 needs to match the output voltage of the second converter 20. With the converter system 100 including the transformer unit 40 coupled between the first converter 10 and the second converter 20, the optimal output voltage of the first converter 10 can be achieved because the optimal output voltage can be used as the input voltage of the transformer unit 40, and the aforementioned voltage matching can be achieved by means of the transformer unit 40.

[0073] Referring to Figure 4, in one embodiment, transformer unit 40 includes a plurality of transformers 41 to 4n. Each of the plurality of transformers is coupled between the first converter 10 and one of the plurality of second converter units. For example, transformer 41 is coupled between the first converter 10 and the second converter unit 21; transformer 42 is coupled between the first converter 10 and the second converter unit 22; and so on, with transformer 4n coupled between the first converter 10 and the second converter unit 2n. In this embodiment, the number of transformers in transformer unit 40 is equal to the number of second converter units in second converter 20.

[0074] Referring to Figure 5, in another embodiment, transformer unit 40 includes a multi-winding transformer 401. The multi-winding transformer 401 includes a primary winding 4010 and a plurality of secondary windings 4011-401n. Each of the plurality of secondary windings is coupled to one of a plurality of second converter units. In this embodiment, the number of secondary windings of the multi-winding transformer is equal to the number of second converter units.

[0075] It should be understood that the embodiments of Figures 4 and 5 can be combined. For example, transformer unit 40 may include multiple transformers arranged as shown in Figure 4 and multi-winding transformers arranged as shown in Figure 5.

[0076] According to an embodiment of the present invention, as shown in FIG6, the converter system 100 further includes a filter unit 50. The filter unit 50 includes a plurality of filters 51 to 5n. Each of the plurality of filters 51 to 5n is coupled between one of the plurality of second converter units and a DC load or a DC source. For example, filter 51 is coupled between second converter unit 21 and DC load 301; filter 52 is coupled between second converter unit 22 and DC source 302… filter 5n is coupled between second converter unit 2n and DC load 30n. Each filter filters the DC ripple on the DC voltage supplied to the DC load or DC source. When the filters are connected to an electrolytic cell, the filters are designed / selected according to the requirements regarding the DC ripple of the electrolytic cell (e.g., <5%). In the example, each filter can be implemented using an LC circuit.

[0077] According to an embodiment of the present invention, the converter system 100 further includes both a transformer unit and a filter unit.

[0078] In one embodiment, as shown in FIG7, the converter system 100 further includes both a transformer unit and a filter unit. In this embodiment, the transformer unit can be implemented by the transformer unit 40 of FIG4, and the filter unit can be implemented by the filter unit 50 of FIG6. Therefore, the features of the transformer unit 40 described above with reference to FIG4 and the filter unit 50 of FIG6 are also applicable to the exemplary converter system 100 of FIG7.

[0079] In another embodiment, as shown in FIG8, the converter system 100 further includes both a transformer unit and a filter unit. In this embodiment, the transformer unit can be implemented by the transformer unit 40 of FIG5, and the filter unit can be implemented by the filter unit 50 of FIG6. Therefore, the features of the transformer unit 40 of FIG5 and the filter unit 50 of FIG6 described above with reference to FIG5 are also applicable to the exemplary converter system 100 of FIG8.

[0080] The first frequency f1 and the second frequency f2 are described below.

[0081] The first frequency f1 is the power frequency, such as 50Hz or 60Hz.

[0082] The second frequency f2 is greater than the first frequency f1. In one embodiment, the second frequency is predetermined to be in the range of 100Hz to 10kHz based on optimized design and for the purpose of minimizing system cost. Experimental results and model calculations show that when the second frequency is in such a range, the size of the transformer (e.g., each transformer in a transformer unit or a multi-winding transformer) is significantly reduced, which reduces the need for filtering DC ripple, thereby enabling the converter system to be implemented without providing a filter unit or with a low-cost filter unit. Moreover, the power loss caused by the on and off operations of the power switches of the first and second converters is not too large to reduce system efficiency. The second frequency can be predetermined through experiments and / or model calculations, making the system cost-effective and applicable to current DC applications.

[0083] The following describes an example of a matrix converter.

[0084] According to an embodiment of the present invention, a matrix converter has a first terminal coupled to a first side 10A of a first converter 10 and a second terminal coupled to a second side 10B of the first converter 10. The matrix converter can convert a first alternating current into a second single-phase or second multi-phase alternating current. The first terminal is coupled to a first-phase system, such as three-phase (a, b, c). The second terminal is coupled to a second-phase system, such as three-phase (x, y, z), or two-phase AC or single-phase AC.

[0085] In one embodiment, a first terminal of the matrix converter is coupled to at least two phases. The matrix converter includes multiple branches. The multiple branches include at least two sets of branches, namely a first set of branches and a second set of branches. The first set of branches includes branches coupled to one of the at least two phases, and the second set of branches includes branches coupled to another of the at least two phases. For example, the first set of branches includes branches coupled to one of the three phases (a, b, c), and the second set of branches includes branches coupled to any one of the remaining two phases (a, b, c). Furthermore, a branch in the first set of branches is configured to be combined by phase or by potential with a corresponding branch included in the second set of branches.

[0086] Figure 9 illustrates an exemplary circuit of a matrix converter according to an embodiment of the present invention.

[0087] Referring to Figure 9, the matrix converter includes nine branches, each branch including one or more modules (B11~B1n) and a branch inductor (i.e., branch reactor) connected in series with the one or more modules (B11~B1n). Each of the one or more modules can be implemented as a full-bridge circuit. Each branch has a first terminal coupled to one of the three phases a, b, c of the matrix converter's first terminal and a second terminal coupled to one of the three phases x, y, z of the matrix converter's second terminal. The nine branches include branches one through nine (branches 1~9). The first terminals of branches one, two, and three are coupled to phase a of the first terminal. The second terminals of branches one, four, and seven are coupled to phase x of the second terminal. The first terminals of branches four, five, and six are coupled to phase b of the first terminal. The second terminals of branches two, five, and eight are coupled to phase y of the second terminal. The first terminals of branches seven, eight, and nine are coupled to phase c of the first terminal. The second ends of the third, sixth, and ninth branches are coupled to the z-phase of the second terminal.

[0088] In this embodiment, the matrix converter may further include nine branch switches, each arranged in one of the nine branches. The branch switches can be operated to provide protection in case of a fault. For example, this can be achieved using a fourth operating mode of the converter system described elsewhere in this invention.

[0089] For example, when at least one of the first, fifth, and ninth branches fails, the branch switches in the first, fifth, and ninth branches are disconnected via controller or manual operation. This allows the matrix converter to continue operating under fault conditions. Similarly, when at least one of the second, sixth, and seventh branches fails, the branch switches in the second, sixth, and seventh branches are disconnected via controller or manual operation. This allows the matrix converter to continue operating under fault conditions. Similarly, when at least one of the third, fourth, and eighth branches fails, the branch switches in the third, fourth, and eighth branches are disconnected via controller or manual operation. This allows the matrix converter to continue operating under fault conditions. Although this embodiment describes fault scenarios in specific branches, those skilled in the art will understand that when a fault is detected in any module of a branch, the controller can operate the first converter to isolate the faulty branch and operate the first converter through other related or voltage-related branches.

[0090] Figure 10 illustrates an exemplary circuit of a matrix converter according to another embodiment of the present invention.

[0091] Referring to Figure 10, the matrix converter includes six branches, each branch including one or more modules (B11~B1n) and branch inductors connected in series with those modules. Each of the modules can be implemented as a full-bridge circuit. Each branch has a first terminal coupled to one of the three phases a, b, c of the matrix converter's first terminal and a second terminal coupled to one of the three phases x, y, z of the matrix converter's second terminal. The six branches include branches one through six (branches 1~6). The first terminals of the first and sixth branches are coupled to phase a of the first terminal. The second terminals of the first and second branches are coupled to phase x of the second terminal. The first terminals of the second and third branches are coupled to phase b of the first terminal. The second terminals of the third and fourth branches are coupled to phase y of the second terminal. The first terminals of the fourth and fifth branches are coupled to phase c of the first terminal. The second terminals of the fifth and sixth branches are coupled to phase z of the second terminal.

[0092] Figure 11 illustrates an exemplary circuit of a matrix converter according to yet another embodiment of the present invention.

[0093] Referring to Figure 11, the matrix converter includes twelve branches, each branch comprising one or more modules (B11-B1n) and branch inductors connected in series with those modules. Each of the modules can be implemented as a half-bridge circuit. The twelve branches include branches 1-6 (branches 1-6) forming a first section and branches 7-12 (branches 7-12) forming a second section. Each branch in the first section has a first terminal coupled to one of the three phases a, b, c of the matrix converter's first terminal. Each branch in the second section has a first terminal coupled to one of the three phases x, y, z of the matrix converter's second terminal. The first terminals of the first and fourth branches are coupled to phase a of the first terminal. The first terminals of the second and fifth branches are coupled to phase b of the first terminal. The first terminals of the third and sixth branches are coupled to phase c of the first terminal. The first terminals of the seventh and tenth branches are coupled to phase x of the second terminal. The first terminals of the eighth and eleventh branches are coupled to phase y of the second terminal. The first ends of the ninth and twelfth branches are coupled to the z-phase of the first terminal. Each of the first to third branches has a second end coupled to the first connection point (at the same potential, and thus described as branches combined based on the potential of the connection point). Each of the seventh to ninth branches has a second end coupled to the first connection point. Each of the fourth to sixth branches has a second end coupled to the second connection point. The tenth to twelfth branches each have a second end coupled to the second connection point. In this embodiment, the first connection point may be the positive terminal of the DC bus, and the second connection point may be the negative terminal of the DC bus. Generally speaking, it can be said that one of the branches in the first group of branches is configured to be combined at the first and second connection points according to the potential with the corresponding branch included in the second group of branches.

[0094] Figure 12 illustrates an exemplary circuit of a matrix converter according to yet another embodiment of the present invention.

[0095] Referring to Figure 12, the matrix converter includes six branches, each branch including one or more modules (B11~B1n) and branch inductors connected in series with the one or more modules. Each of the one or more modules can be implemented as a full-bridge circuit. The six branches include branches 1 to 6 (branches 1 to 6), and the first terminal of each branch is coupled to one of the three phases a, b, and c of the first terminal of the matrix converter. The first terminals of the first and fourth branches are coupled to phase a of the first terminal. The first terminals of the second and fifth branches are coupled to phase b of the first terminal. The first terminals of the third and sixth branches are coupled to phase c of the first terminal. Each of the first to third branches has a second terminal coupled to a first connection point. Each of the fourth to sixth branches has a second terminal coupled to a second connection point. In this embodiment, the first connection point can be the positive terminal of the DC bus, and the second connection point can be the negative terminal of the DC bus. The first connection point and the second connection point constitute a single-phase second AC.

[0096] An exemplary circuit for the second converter unit is described below. For clarity, the exemplary circuit is described using second converter unit 21 as an example. Other second converter units can be implemented in a similar manner.

[0097] Figure 13 illustrates an exemplary circuit of a second converter unit 21 according to an embodiment of the present invention. As shown in Figure 13, the second converter unit 21 is implemented as a three-phase thyristor rectifier. In this embodiment, the second converter unit 21 is coupled to a filter 51, which is a DC filter. The filter 51 includes an inductor and / or one or more capacitors. The filter 51 is coupled between the second converter unit 21 and a DC load 301 for filtering out DC ripple.

[0098] Figure 14 illustrates an exemplary circuit of a second converter unit 21 according to another embodiment of the present invention. As shown in Figure 14, the second converter unit 21 is implemented as a voltage source converter (VSC) based on a three-phase IGBT. In this embodiment, the second converter unit 21 is coupled to a filter 51, which is a DC filter. The filter 51 includes one or more capacitors. The filter 51 is coupled between the second converter unit 21 and a DC load 301 for filtering out DC ripple.

[0099] Figure 15 illustrates an exemplary circuit of a second converter unit 21 according to yet another embodiment of the present invention. As shown in Figure 15, the second converter unit 21 is implemented as a three-phase diode rectifier in combination with a buck converter. In one embodiment, the diode rectifier performs AC / DC conversion, and the buck converter is operated to regulate the output voltage or output current based on the power supply requirements of the DC load 31. Filter 51 is a DC filter 51 and includes one or more capacitors. Filter 51 is coupled between the second converter unit 21 and the DC load 301 for filtering out DC ripple.

[0100] Exemplary methods Building upon the example system described above, exemplary methods are now presented. These methods can be executed using the controller 30 described above. It should be understood that the operations involved in the following methods do not need to be performed in the exact order described. Instead, multiple operations can be performed in different orders or simultaneously, and operations can be added or omitted.

[0101] Figure 16 illustrates a control method 1600 for controlling a converter system 100 according to an embodiment of the present invention.

[0102] In block 1610, controller 30 receives feedback information from at least one of a first converter, at least one of a plurality of second converter units, and at least one of a DC unit coupled to at least one second converter unit. In one embodiment, the feedback information includes measurement information measured by current sensors and / or voltage sensors arranged in converter system 100. It should be understood that the above description regarding reference feedback information also applies here.

[0103] In block 1620, controller 30 controls at least one of the first converter 10 and at least one of the second converter units based on feedback information to control the power supplied to or from the DC unit. For example, controller 30 controls at least one of the first converter and at least one of the second converter units such that the voltage or current used to supply power to or receive power from at least one of the plurality of DC units is adjusted based on regulation values ​​and operating modes configured for the converter system. Thus, regulation of at least one of the voltage and current supplied to the DC unit can be achieved by controlling the first converter and at least one of the second converter units to respond to changes in load-side demand; that is, loading the DC unit can be achieved by controlling the first converter and at least one of the second converter units. Furthermore, the configured regulation values ​​are values ​​used to configure the controller to perform the aforementioned regulation, and coordinated control of the first converter and at least one of the second converter units using the technology provided by this invention also helps to improve the accuracy of regulation.

[0104] The following describes an embodiment of the control in block 1620.

[0105] Figure 17 illustrates one embodiment of block 1620 (method 1700). In this embodiment, the converter system 100 is in a first operating mode. For clarity, this embodiment is illustrated using the example of a first converter 10 and a second converter unit 21 supplying power to a DC load 301. In this embodiment, the DC load 301 is supplied by an AC source 200.

[0106] Referring to Figure 17, in block 1710, controller 30 controls first converter 10 to convert first AC on first side 10A to second AC on second side 10B, and controls second converter unit 21 to operate as a rectifier (i.e., line AC-DC conversion).

[0107] In block 1720, controller 30 determines, based on feedback information, the amount of voltage regulation supplied to DC load 301 and / or the amount of current regulation supplied to DC load 301. For example, depending on the requirements of the current application to which converter system 100 is used, the voltage supplied to load 301 needs to be increased by 10%, and this requirement can be included in the feedback information. In this case, controller 30 determines, based on the feedback information, to increase the voltage supplied to DC load 301 by 10%.

[0108] In block 1730, controller 30 determines whether the first converter 10 can achieve the determined voltage regulation amount and / or the determined current regulation amount to realize the configuration regulation value of the first converter 10. In one embodiment, the configuration regulation value (predetermined regulation value) of the first converter 10 may include the aforementioned voltage regulation amount and / or current regulation amount, and may also include a calibration value (e.g., a linear regulation amount) for achieving the voltage regulation amount and / or current regulation amount. There is a situation where the configuration regulation value (predetermined regulation value) of the first converter 10 may be equal to the minimum regulation value that the first converter 10 can achieve (i.e., the configuration regulation value is the limit value that the regulation accuracy of the first converter can achieve). In this case, controller 30 determines whether the first converter can achieve the configuration regulation value. For example, controller 30 may determine whether the voltage regulation accuracy value of the first converter meets the determined voltage regulation amount or linear regulation value of the first converter 10. Similarly, controller 30 may determine whether the current regulation accuracy value of the first converter meets the determined current regulation amount or linear regulation value of the first converter 10.

[0109] It is understood that the minimum adjustment value achievable by the first converter 10 corresponds to the adjustment accuracy of the first converter. This minimum adjustment value can be preset. For example, the minimum adjustment value can be set to the sum of the minimum adjustment value determined based on the device performance of the first converter and an offset, which can be preset according to the current application scenario.

[0110] If the determination result in block 1730 is negative ("No"), that is, it is determined that the first converter 10 cannot achieve the determined voltage regulation amount and / or the determined current regulation amount, then method 1700 proceeds to block 1740. In block 1740, controller 30 controls the second converter unit 21 to adjust the output current and / or output voltage of the second converter unit 21 according to the determined voltage regulation amount and / or the determined current regulation amount.

[0111] If the determination result in block 1730 is affirmative ("yes"), that is, if the determination bit indicates that the first converter 10 can achieve the determined voltage regulation amount and / or the determined current regulation amount, then method 1700 proceeds to block 1750. In block 1750, controller 30 controls the first converter 10 to adjust the output current and / or output voltage of the first converter 10 according to the determined voltage regulation amount and / or the determined current regulation amount.

[0112] In block 1760, controller 30 controls second converter unit 21 to compensate for the difference between the determined regulation and the regulation implemented by first converter 10, thereby improving the accuracy of voltage regulation and / or current regulation.

[0113] For example, it is determined that the voltage supplied to the DC load 301 will be increased by 100V. The controller 30 compares the determined voltage regulation (e.g., 100V) with the voltage regulation (e.g., 90V) implemented by the first converter 10 to obtain the difference (e.g., 10V). The controller 30 then controls the second converter unit 21 to increase the output voltage of the second converter unit 21 by 10V to compensate for this difference. In this way, higher precision voltage regulation and / or current regulation can be achieved.

[0114] It is worth noting that the control of the first converter can be considered as first-level control, in order to achieve the required adjustment with a certain degree of precision. The adjustment implemented by the second converter unit can be considered as fine-tuning for improving precision.

[0115] Alternatively, the first converter and at least one second converter unit can be controlled simultaneously based on a configured adjustment value. This configuration adjustment value is based on voltage and / or current regulation amounts and also on a preset reference value to improve accuracy.

[0116] In this way, coordinated control of the converter system 100 is achieved. This is advantageous because there are situations where the determined adjustment cannot be achieved by relying on the first converter due to the limitation of the minimum adjustment capability of the first converter 10. Furthermore, the fine-tuning function of the second converter unit can be utilized. According to the control strategy of method 1700, various adjustment situations can be addressed, and the adjustment accuracy under various adjustment situations can be improved.

[0117] Figure 18 illustrates another embodiment of block 1620 (method 1800). In this embodiment, the converter system 100 is in a first operating mode and is used to power multiple electrolytic cells. For clarity, this embodiment is described as an example of powering electrolytic cells 301 and 30n using a first converter 10, a second converter unit 21, and a second converter unit 2n. The distributed control system described above in conjunction with Figure 3 is particularly suitable for the implementation of method 1800.

[0118] Referring to Figure 18, in block 1810, controller 30 controls first converter 10 to convert the first AC on the first side 10A to the second AC on the second side 10B, controls second converter unit 21 to operate as a rectifier (i.e., to perform AC-DC conversion), and controls second converter unit 2n to also operate as a rectifier (i.e., to perform AC-DC conversion).

[0119] In block 1820, controller 30 determines the total adjustment amount of voltage and / or current supplied to electrolyzers 301 and 30n based on feedback information. In embodiments for industrial applications, the feedback information may include changes in hydrogen production demand, and the total adjustment amount of voltage and / or current supplied to electrolyzers 301 and 30n may be determined based on these changes in hydrogen production demand.

[0120] In block 1830, controller 30 determines preset values ​​(configuration adjustment values) for the first converter unit 10, the second converter unit 21, and the second converter unit 2n based on the determined total adjustment amount and also based on the operating state of each of the plurality of electrolytic cells.

[0121] The operating status of each of the multiple electrolytic cells 301 and 30n can be determined based on feedback information. In the case of voltage regulation, the preset values ​​include the adjustment amount of the output voltage of the first converter unit 10, the adjustment amount of the output voltage of the second converter unit 21, and the adjustment amount of the output voltage of the second converter unit 2n. In the case of current regulation or both current regulation and voltage regulation, the preset values ​​can be implemented in a similar manner.

[0122] In one embodiment, the hydrogen production rate of each electrolyzer can be fine-tuned by controlling the corresponding second converter unit (each second converter unit is adjusted individually). For example, it is desirable for electrolyzers with a higher degree of aging to operate under light load to slow down their aging rate. It is also desirable for electrolyzers with a lower degree of aging to operate under higher load to improve the overall hydrogen production rate. In this way, the determined hydrogen production rate can be achieved. Moreover, the aging rate of each electrolyzer tends to be the same, thereby reducing the maintenance cost of the electrolyzers.

[0123] Examples of achieving a 30% increase in hydrogen production rate (i.e., a target adjustment of +30%) are shown in Table 1 below. In Table 1, the first column indicates the number of each embodiment, the second column indicates the adjustment of hydrogen production rate achieved by the first converter unit 10, the third column indicates the adjustment of hydrogen production rate achieved by the second converter unit 21, the fourth column indicates the adjustment of hydrogen production rate achieved by the second converter unit 2n, and the fifth column indicates the target adjustment of hydrogen production rate. In Table 1, the symbol "+" represents an increase, and the symbol "-" represents a decrease.

[0124] Table 1

[0125] The controller 30 can determine preset values ​​for the coordinated control of the first converter 10 and the second converter units 21 and 2n based on the fine-tuning of the hydrogen production rate of each electrolyzer. For example, referring to Embodiment 1 shown in Table 1, preset values ​​are determined such that the output voltage of the first converter 10 increases by 28%, the output voltage of the second converter unit 21 increases by 1%, and the output voltage of the second converter unit 2n increases by 1%.

[0126] In block 1840, controller 30 sends preset values ​​to local control unit 11 of first converter unit 10, local control unit 211 of second converter unit 21, and local control unit 2n1 of second converter unit 2n, so that the local control units control the first converter 10 and the second converter units 21 and 2n according to the preset values. This realizes the coordinated control of converter system 100.

[0127] It should be understood that the preset value can be dynamically adjusted based on feedback information. For example, when the relative aging rate between the two electrolytic cells changes, the preset value will also change accordingly.

[0128] Figure 19 illustrates another embodiment of block 1620 (method 1900). In this embodiment, the converter system 100 is in a second operating mode and is used to transfer energy stored in one or more DC sources to AC source 200. For clarity, this embodiment is described using the example of energy stored in DC source 302 being transferred to AC source 200.

[0129] Referring to Figure 19, in block 1910, controller 30 controls first converter 10 to convert second AC on second side 10B to first AC on first side 10A, and controls second converter unit 22 to operate as an inverter (i.e., perform DC-AC conversion).

[0130] In block 1920, controller 30 determines the energy transfer mode based on the attribute characteristics of DC source 302, and controls the first converter 10 and the second converter unit 22 based on the determined energy transfer mode. In one embodiment, the energy transfer mode is one of a continuous transfer mode and an intermittent transfer mode. For example, when DC source 302 is solar energy, the transfer mode is determined based on the light intensity and can be an intermittent transfer mode. When DC source 302 is associated with wind energy, the transfer mode is determined taking into account seasonality and can be an intermittent transfer mode. When DC source 302 is a fuel cell (which can generate electricity using H2 and O2), the transfer mode can be determined to be a continuous transfer mode.

[0131] Figure 20 illustrates another embodiment of block 1620 (method 2000). In this embodiment, the converter system 100 is in a third operating mode and uses a first converter 10 and one or more DC sources to power the DC load. That is, the DC load is powered by both the AC power supply 200 and one or more DC sources. For clarity, this embodiment is described using the example of the first converter 10 and the second converter units 21-22 powering the DC load 301. The distributed control system described above in conjunction with Figure 3 is particularly suitable for implementing method 2000.

[0132] Referring to Figure 20, in block 2010, controller 30 controls first converter 10 to convert first AC power on first side 10A into second AC power on second side 10B, controls second converter unit 21 to operate as a rectifier (i.e., to perform AC-DC conversion), and controls second converter unit 22 to operate as an inverter (i.e., to perform DC-AC conversion).

[0133] In block 2020, controller 30 determines a preset configuration value for the allocation between the power received from the first converter unit 22 and the power received from the second converter unit 22. For example, this preset configuration value could be the ratio between the power received from the first converter unit 22 (i.e., the power provided by the AC source 200) and the power received from the second converter unit 22 (i.e., the power provided by the DC source 22). In one embodiment, the DC source 302 is a renewable energy source and thus can provide green energy. In this embodiment, green energy can be utilized as much as possible. Therefore, the maximum amount of energy that the DC source 302 can provide will be utilized first. When the maximum energy that the DC source 302 can provide is insufficient to power the DC load 301, energy from the AC source 200 will be used as a supplement.

[0134] In block 2030, controller 30 sends preset values ​​to local control unit 11 of first converter 10 and local control unit 221 of second converter unit 22, so that local control units control first converter 10 and second converter unit 22 according to preset values.

[0135] Figure 21 illustrates another embodiment of block 1620 (method 2100). In this embodiment, the converter system 100 is in a fourth operating mode and is used to power a DC load using one or more DC sources. This embodiment is particularly suitable for fault situations where the AC source 200 is unable to obtain power from the grid due to a grid failure or where power cannot be supplied to the DC load due to a fault in a module of a branch of the first converter. For clarity, this embodiment is described using the second converter units 21 and 22 as an example of powering the DC load 301. In other words, the DC load 301 can be powered solely by the DC source 302 to overcome the fault state. Alternatively, in the event of a fault in a branch of the first converter, the first converter can be operated using corresponding other branches in the branch group.

[0136] In block 2110, controller 30 controls second converter unit 21 to operate as a rectifier (i.e., to perform AC-DC conversion) and controls second converter unit 22 to operate as an inverter (i.e., to perform DC-AC conversion).

[0137] In block 2120, controller 30 controls second converter units 21 and 22, such that energy flows from DC source 302 through second converter unit 22 and second converter unit 21 to DC load 301.

[0138] This control strategy is advantageous because it ensures that the DC load can be continuously powered, thus eliminating the need to shut it down during fault clearing. This is particularly useful when the power grid coupled to AC source 200 experiences a transient fault. In this case, according to the control strategy of method 2100, the DC load can continue to operate unaffected.

Claims

1. A converter system, comprising: The first converter includes a first AC side having a first frequency and a second AC side having a second frequency, and the first converter includes a converter having multiple branches; Multiple second converter units are configured to be coupled between a first converter and multiple DC units, each of the multiple DC units being a DC load or a DC source; And a controller configured to control at least one of a first converter and at least one second converter unit to control the power supplied to or by at least one of a plurality of DC units.

2. The converter system as claimed in claim 1, wherein, The first frequency is the power frequency; and the second frequency is higher than the first frequency, and the range of the second frequency is 100Hz~10kHz.

3. The converter system as described in any one of claims 1-2, wherein, The converter is a matrix converter and has a first terminal coupled to at least two phases; the plurality of branches include a first group of branches and a second group of branches, the first group of branches including branches coupled to one of the at least two phases, and the second group of branches including branches coupled to the other of the at least two phases. Furthermore, one branch in the first group of branches is configured to be combined with a corresponding branch included in the second group of branches by phase or by potential.

4. The converter system as described in any one of claims 1-2, wherein, The converter is a matrix converter and includes nine branches. Each branch includes one or more modules and a branch inductor connected in series with the one or more modules. Each branch has a first terminal coupled to one of three phases a, b, c and a second terminal coupled to one of three phases x, y, z of the matrix converter. The nine branches include a first to a ninth branch. The first terminals of the first, second, and third branches are coupled to phase a of the first terminal, and the second terminals of the first, fourth, and seventh branches are coupled to phase x of the second terminal. The first terminals of the fourth, fifth, and sixth branches are coupled to phase b of the first terminal, and the second terminals of the second, fifth, and eighth branches are coupled to phase y of the second terminal. The first terminals of the seventh, eighth, and ninth branches are coupled to phase c of the first terminal, and the second terminals of the third, sixth, and ninth branches are coupled to phase z of the second terminal.

5. The converter system of claim 4, wherein, The matrix converter also includes nine branch switches, each branch switch being arranged on a corresponding branch of the nine branches; and wherein the controller is configured to control one or more of the nine branch switches to clear the fault in the event of a fault in at least one of the nine branches.

6. The converter system as described in any one of claims 1-2, wherein, The converter is a matrix converter and includes six branches. Each branch includes one or more modules and a branch inductor connected in series with the one or more modules. Each branch has a first terminal of one of three phases a, b, and c coupled to a first terminal of the matrix converter and a second terminal of one of three phases x, y, and z coupled to a second terminal of the matrix converter. The six branches include a first to a sixth branch. The first terminals of the first and sixth branches are coupled to phase a of the first terminal, and the second terminals of the first and second branches are coupled to phase x of the second terminal. The first terminals of the second and third branches are coupled to phase b of the first terminal, and the second terminals of the third and fourth branches are coupled to phase y of the second terminal. The first terminals of the fourth and fifth branches are coupled to phase c of the first terminal, and the second terminals of the fifth and sixth branches are coupled to phase z of the second terminal.

7. The converter system as described in any one of claims 1-2, wherein, The converter is a matrix converter and includes twelve branches, each branch including one or more modules and a branch inductor connected in series with the one or more modules; the twelve branches include first to sixth branches constituting a first part and seventh to twelfth branches constituting a second part; and each branch of the first part has a first terminal of one of the three phases a, b, c coupled to a first terminal of the matrix converter, and each branch of the second part has a first terminal of one of the three phases x, y, z coupled to a second terminal of the matrix converter; The first ends of the first and fourth branches are coupled to phase a of the first terminal, the first ends of the second and fifth branches are coupled to phase b of the first terminal, and the first ends of the third and sixth branches are coupled to phase c of the first terminal. The first ends of the seventh and tenth branches are coupled to the x phase of the second terminal, the first ends of the eighth and eleventh branches are coupled to the y phase of the second terminal, and the first ends of the ninth and twelfth branches are coupled to the z phase of the first terminal. The first to the third branches each have a second end coupled to the first connection point, and the seventh to the ninth branches each have a second end coupled to the first connection point; and the fourth to the sixth branches each have a second end coupled to the second connection point, and the tenth to the twelfth branches each have a second end coupled to the second connection point.

8. The converter system as described in any one of claims 1-2, wherein, The converter is a matrix converter and includes six branches, each branch including one or more modules and a branch inductor connected in series with the one or more modules; the six branches include a first branch to a sixth branch, each branch having a first terminal of one of the three phases a, b, c coupled to a first terminal of the matrix converter; The first ends of the first and fourth branches are coupled to phase a of the first terminal, and the first ends of the second and fifth branches are coupled to phase b of the first terminal, and the first ends of the third and sixth branches are coupled to phase c of the first terminal. Each of the first to third branches has a second end coupled to the first connection point, and each of the fourth to sixth branches has a second end coupled to the second connection point.

9. The converter system of any one of claims 1-8 further includes a plurality of filters, each filter being coupled between one of the plurality of second converter units and one of the plurality of DC units.

10. The converter system of any one of claims 1-9 further includes a transformer unit coupled between the first converter and a plurality of second converter units.

11. The converter system of claim 10, wherein, The transformer unit includes multiple transformers, each transformer being coupled between the first converter and one of the multiple second converter units.

12. The converter system of claim 10, wherein, The transformer unit includes a transformer having a primary winding and multiple secondary windings, each secondary winding being coupled to one of a plurality of second converter units.

13. The converter system according to any one of claims 1-12, wherein, The controller is configured to receive feedback information from at least one of a first converter, at least one of a plurality of second converter units, and at least one of a DC unit coupled to the at least one second converter unit, and to control the first converter and at least one of the at least one second converter unit based on the feedback information.

14. The converter system according to any one of claims 1-13, wherein, The converter system is operable in one of the following operating modes: a first operating mode in which power is transferred from an AC source coupled to a first side of the first converter to one or more DC units of a plurality of DC units. In the second operating mode, power is transferred from one or more DC sources among a plurality of DC units to the first AC side; A third operating mode, in which at least one of the plurality of second converter units is configured to receive power from a first converter and at least another of the plurality of second converter units; and a fourth operating mode, in which at least one of the plurality of second converter units is configured to receive power from at least another of the plurality of second converter units, or to receive power from both a first converter and the at least another second converter unit operated to isolate at least one faulty branch of a plurality of branches.

15. The converter system according to any one of claims 1-14, wherein, The controller is included in the first converter.

16. The converter system according to any one of claims 1-14, wherein, The plurality of second converter units have a common local controller, wherein the controller is contained within the common local controller.

17. The converter system according to any one of claims 1-14, wherein, The first converter includes a local control unit, and each of the plurality of second converters includes a local control unit; and the controller communicates with each local control unit for coordinated control of the first converter and the plurality of second converter units.

18. The converter system as claimed in any one of claims 1-17, wherein, The controller is configured to control at least one of the first converter and at least one of the second converter units such that at least one of the voltage and current used to supply power to or receive power from at least one of the plurality of DC units is adjusted based on configuration adjustment values ​​and operating modes for the converter system.

19. The converter system of claim 14, wherein, The controller is configured to determine the amount of electricity received from the first converter unit and the amount of electricity received from the at least one second converter unit, based on a preset configuration value, when the converter system is in a third operating mode.

20. A control method for controlling a converter system, the converter system including a first converter and a plurality of second converter units, the first converter including a first AC side having a first frequency and a second AC side having a second frequency, the first converter including a converter having a plurality of branches, the plurality of second converter units configured to be coupled between the first converter and a plurality of DC units, each of the plurality of DC units being a DC load or a DC source, the control method comprising: Control at least one of the first converter and at least one of the second converter units to control the power supplied to or by at least one of the plurality of DC units.

21. A power supply system for supplying power to an electrolytic cell, the power supply system comprising a converter system as claimed in any one of claims 1-19.

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