CN118337076A

CN118337076A - Converter system, controller and control method thereof

Info

Publication number: CN118337076A
Application number: CN202211703573.1A
Authority: CN
Inventors: 张维驰; 杨晓波; 黄杏; P·迈巴赫; N·约翰松; 陶星澳
Original assignee: Hitachi Energy Ltd
Current assignee: Hitachi Energy Ltd
Priority date: 2022-12-28
Filing date: 2022-12-28
Publication date: 2024-07-12
Also published as: WO2024141180A1

Abstract

The invention provides a converter system for supplying a direct current load, comprising: a modular converter comprising two or more converter modules coupled between two or more sets of secondary side windings of the phase-shifting transformer and the dc load, each converter module comprising a first converter for outputting a first dc voltage and a second converter for outputting a second dc voltage; and a controller configured to control each converter module to regulate a second DC voltage output by a second converter of each converter module.

Description

Inverter system, controller therefor, and control method therefor

Technical Field

The present invention relates to a solution for dc load powering, in particular to a converter system for dc load powering, and to a method and a controller for controlling a modular converter for powering a dc load.

Background

High power AC/DC rectifiers play a critical role as a power source in DC load applications. In this regard, a variety of different isolated power converter topologies, such as flyback, half-bridge, and full-bridge converters, have been developed to meet the ever-increasing demand for powering dc loads. But the existing solutions still cannot fully meet the increasing demands in terms of efficiency and flexibility for powering dc loads. Moreover, the existing solutions have the problems of high device cost and complex structure.

Disclosure of Invention

In view of the foregoing problems of the prior art, according to an implementation of one aspect of the present invention, there is provided a converter system for supplying a dc load, comprising: a modular converter comprising two or more converter modules coupled between two or more sets of secondary side windings of the phase-shifting transformer and the dc load, each converter module comprising a first converter for outputting a first dc voltage and a second converter for outputting a second dc voltage; and a controller configured to control each converter module to regulate a second DC voltage output by a second converter of each converter module.

In one embodiment, the first converter and the second converter are connected in series, and a sum of the first dc voltage and the second dc voltage is provided to the dc load.

In one embodiment, the second converter and the dc load are connected in series, and a difference between the first dc voltage and the second dc voltage is provided to the dc load.

In one embodiment, the outputs of the two or more converter modules are connected in parallel.

In one embodiment, the outputs of the two or more converter modules are connected in series.

In one embodiment, the controller is configured to: receiving feedback information from at least one of the transformer, the modular converter, and the dc load; and controlling the second converter of each converter module based on the feedback information to regulate a second direct current voltage output by the second converter of each converter module.

In one embodiment, the controller is configured to: determining whether an imbalance condition occurs in the two or more converter modules based on the feedback information; and upon determining that an imbalance condition occurs for at least one of the inverter modules, controlling a second inverter of the at least one inverter module to return the at least one inverter module to the equilibrium condition.

In one embodiment, the controller is configured to: determining whether a short circuit fault occurs to the direct current load based on the feedback information; and controlling the second converter of each converter module to disconnect the dc load from its power supply circuit when it is determined that a short circuit fault has occurred for the dc load.

In one embodiment, the controller is configured to: determining whether a power supply mode required by the direct current load is a constant voltage mode or a constant current mode based on the feedback information; and controlling the second converter of each converter module such that the power supply to the dc load meets its demand power mode.

In one embodiment, the controller is configured to perform for a case where the direct current load is an electrolysis cell: the second DC voltage is regulated by controlling the second inverter of each inverter module when the actual operating state of the electrolytic cell does not coincide with the target operating state, so that the actual operating state of the electrolytic cell becomes the target operating state.

In one embodiment, the controller is configured to perform for a case where the direct current load is an electrolysis cell: in case the operating state of the electrolyzer is an overload state and the second DC voltage is a limit value of its regulation range, a command signal is generated for changing the tap position of a tap changer coupled to the primary winding of the transformer such that both the first DC voltage and the second DC voltage are controlled.

In one embodiment, the controller is configured to perform for a case where the direct current load is an electrolysis cell: determining whether the health status of the electrolyzer is degraded based on the feedback information; and controlling the second converter of each converter module to regulate the second direct voltage in the event of a determination that the health of the electrolyzer is degraded, such that the hydrogen production rate of the electrolyzer is controlled.

In one embodiment, each of the two or more converter modules is coupled to and powers one of a plurality of independent loads.

In one embodiment, one or more of the two or more converter modules collectively power a load in a series or parallel connection.

According to an embodiment of another aspect of the present invention, there is provided a method for controlling a modular converter for powering a dc load, the modular converter comprising two or more converter modules coupled between two or more sets of secondary side windings of a phase-shifting transformer and the dc load, each converter module comprising a first converter for outputting a first dc voltage and a second converter for outputting a second dc voltage, the method comprising: each converter module is controlled to regulate a second dc voltage output by a second converter of each converter module.

According to an embodiment of a further aspect of the invention, there is provided a controller for controlling a modular converter to supply a dc load, comprising one or more processors configured to perform the method as described above.

Drawings

The technical solution of the present invention will be more apparent from the following detailed description with reference to the accompanying drawings. It is to be understood that these drawings are solely for purposes of illustration and are not intended as a definition of the limits of the invention.

FIG. 1 is a block diagram of an exemplary system according to one embodiment of the invention.

Fig. 2 and 3 are schematic block diagrams of converter modules according to some embodiments of the invention.

Fig. 4 is a schematic circuit example of a converter module according to an embodiment of the invention.

Fig. 5 and 6 are schematic block diagrams of modular converters according to some embodiments of the invention.

Fig. 7 and 8 are implementations of modular converters connected to loads according to some embodiments of the invention.

Fig. 9 is a flow chart of a method of controlling power to a load according to one embodiment of the invention.

Fig. 10-14 are flowcharts of some implementations of the main steps of the method of fig. 9, according to some embodiments of the invention.

Fig. 15-18 are schematic structural diagrams of transformers according to some embodiments of the invention.

Detailed Description

Overview

Embodiments of the present invention relate to a solution for powering a direct current load (DC load) with the advantages of high system efficiency, low device cost and small size.

According to the power supply scheme of the embodiment of the invention, a DC load (hereinafter, referred to as a "load") is supplied by combining a modular Multi-pulse converter with a phase-shifting transformer (hereinafter, referred to as a "transformer" for some places). The multi-pulse converter includes at least two converter modules, and the phase-shifting transformer includes at least two sets of secondary-side windings coupled to the at least two converter modules. Each converter module includes two converters, one of which delivers most power to the dc load and the other of which can be controlled to process only a small fraction of the power delivered to the load or backed off to a superior power delivery device (e.g., a phase shifting transformer), whereby each converter module implements a partial power processing (PP: partial power processing) converter.

The power supply solution according to the embodiment of the invention comprises a control strategy for supplying power to the load, thereby realizing that the power supply to the load is controllable so as to meet the customized power supply requirement of the load and also optimizing the working efficiency and the running state of the load.

The power supply scheme provided by the embodiment of the invention is particularly suitable for supplying power to the electrolytic cell so as to optimize the hydrogen production rate and the working efficiency of the electrolytic cell according to the state of the electrolytic cell. The power supply scheme according to the embodiment of the invention is also suitable for being used as a rectifying front end of a high-voltage rectifying system to provide adjustable high voltage. The power supply scheme according to the embodiment of the invention is also suitable for providing constant current power supply or constant voltage power supply according to the power supply requirement of the load.

The direct-current side topology structure according to the embodiment of the invention can be realized by adopting a Step-up topology (Step-up topology) or a Step-down topology (Step-down topology), thereby having wide application scenes.

The plurality of converter modules according to the embodiment of the invention can be connected in parallel or in series, and can supply power to a plurality of loads simultaneously in a plurality of combination modes, so that the invention has wide application fields.

According to an embodiment of the invention, each set of secondary side windings of the phase-shifting transformer comprises a high power secondary winding and a low power secondary winding, which cooperates with the above-described partial power handling converter such that a majority of the power is transmitted by the high power secondary winding and a low power winding transmits only a small part of the power. Such a "large and small winding" scheme optimizes the power level of the multi-pulse converter required when the load voltage is varying.

The structural features of the phase-shifting transformer according to embodiments of the present invention (e.g., the number of sets of secondary windings, the arrangement of primary and secondary windings) are designed with consideration given to harmonic performance and fault conditions, which makes the phase-shifting transformer a "custom-made" transformer for powering loads.

In addition, according to the control strategy of the invention, the system comprising the power grid, the transformer, the modularized converter and the load can be cooperatively controlled, so that the working efficiency and the running state of each component part in the system are optimized.

Exemplary System

FIG. 1 schematically illustrates an exemplary system that includes aspects of the present invention. Referring to fig. 1, the exemplary system includes: an AC source (AC source) 1, a transformer 2, a modular converter 3, a controller 4, and a dc load 5.

The AC source 1 may be an AC grid (e.g., grid-connected or off-grid coupled with a renewable energy source). The AC source 1 may also be coupled in a micro grid. The AC source 1 may also be a point of common connection (PCC: point of Common Coupling) in an electrical power system.

With continued reference to fig. 1, a transformer 2 is coupled between AC source 1 and modular converter 3 for transferring AC power between AC source 1 and modular converter 3. The transformer 2 comprises at least one primary side winding 20 and at least two sets of secondary side windings, e.g. a first set of secondary side windings 21 and a second set of secondary side windings 22. Each set of secondary side windings comprises two secondary windings. The primary windings have different turns ratios from the two secondary windings, respectively, such that one of the secondary windings transmits high power and the other winding transmits relatively low power. In other words, each set of secondary side windings includes one high power secondary winding and one low power secondary winding. For example, the first set of secondary side windings 21 includes a high power secondary winding 211 and a low power secondary winding 212. The second set of secondary side windings 22 includes a high power secondary winding 221 and a low power secondary winding 222. Here, the high power secondary winding may also be referred to as a first power secondary winding, the low power secondary winding may also be referred to as a second power secondary winding, and the first power is greater than the second power.

In these secondary windings, the phase angles of the windings in the groups are the same, and there is a phase shift between the groups. That is, the high power secondary windings in each set of secondary windings have the same phase angle as the low power secondary windings (e.g., with respect to a "zero phase" as a reference phase, which may be a virtual phase), and the sets of secondary windings have phase differences therebetween, i.e., the secondary side windings have inter-set phase shifts. In this way, one secondary winding of one set of secondary windings is offset by a phase angle with respect to one secondary winding of the other set of secondary windings. For example, the high power secondary winding 221 and the low power secondary winding 222 in the first set of secondary side windings 21 each have a first phase angle, the high power secondary winding 221 and the low power secondary winding 222 in the second set of secondary side windings 22 each have a second phase angle, and the second phase angle is different from the first phase angle. With respect to the embodiment of the transformer 2 (for example, the number of primary side windings, the number of groups of secondary side windings, the determination of the phase shift angle, the arrangement of the primary side windings and the secondary side windings), will be described in detail below.

With continued reference to fig. 1, the modular converter 3 includes at least two converter modules, e.g., a first converter module 31 and a second converter module 32. Each converter module comprises two converters, and outputs a direct current voltage respectively. And, at least one of the two converters of each converter module is controllable such that at least one of the two dc voltages output by the two converters is adjustable, whereby a controllable supply of power to the load 5 is achieved. As shown in fig. 1, the first inverter module 31 includes a first inverter 311 and a second inverter 312. The second inverter module 32 includes a first inverter 321 and a second inverter 322. The individual converters in each converter module are each coupled to one secondary winding of a set of secondary side windings of the transformer 2. The first transformer 311 and the second transformer 312 of the first transformer module 31 are coupled with the high power secondary winding 211 and the low power secondary winding 212 of the first set of secondary side windings, respectively. The first and second converters 321, 322 of the second converter module 32 are coupled with the high power secondary winding 221 and the low power secondary winding 222, respectively, of the second set of secondary side windings 22.

For each converter module, most of the power is supplied to the load via a first converter coupled to the high power secondary winding, while a second converter coupled to the low power secondary winding only processes a small fraction of the power, the so-called partial power processing (PPP: partial power processing) converter. Taking the first inverter module 31 as an example, most of the power is provided to the load 5 via the first inverter 311 and the second inverter 312 only processes a small portion of the power. For example, a small fraction of the power is transferred to load 5 ("Step-up" topology) or the small fraction is returned to the transformer ("Step-down" topology).

Each converter module may be implemented in the same manner. In the following, an implementation of the converter module is described in connection with fig. 2 and 3, taking the first converter module 31 as an example.

Referring to fig. 2, in one embodiment, the first converter 311 may be implemented as an AC-DC converter and outputs a first direct current voltage V ₁. The AC-DC converter may be implemented as an uncontrollable device such as a diode to output a fixed direct voltage. The AC-DC converter may also be implemented as a semi-controlled device, such as a thyristor, to output a regulated direct current voltage. The second converter 312 may be implemented to include an AC-DC converter and a DC-DC converter connected in series and output an adjustable second direct current voltage V ₂. Referring to fig. 3, in another embodiment, the second converter 312 may also be implemented as a single-stage AC-DC converter and outputs an adjustable second direct current voltage V ₂.

In addition, as described above, each converter module may be implemented as a "step-up" topology, or as a "step-down" topology. Taking the first converter module in fig. 2 as an example, in the boost topology, the voltage provided to the load 5 by the first converter module is the sum of the output first dc voltage V ₁ of the first converter 311 and the second dc voltage V ₂ output by the second converter 312. In the buck topology, the voltage supplied to the load 5 by the first inverter module is the difference between the output first dc voltage V ₁ of the first inverter 311 and the second dc voltage V ₂ output by the second inverter 312.

Fig. 4 shows an implementation of the converter module. For clarity, the inverter module 31 is illustrated in fig. 4 as an example.

Referring to fig. 4, the first inverter 311 connected to the high-power secondary winding 211 is a three-phase rectifier, implemented by three legs of 6 diodes, and input thereof is three-phase alternating current transmitted from the high-power secondary winding 211. The second converter 312 connected to the low power secondary winding 212 is implemented as a three-phase bridge fully controlled rectifier circuit that includes a plurality of switching devices. The plurality of switching means may be realized, for example, by means of a power electronic switch such as a MOSFET or an IGBT. Each switching device has a control terminal to receive a control signal from the controller 4 so that the output of the second inverter 312 is controllable.

Returning to fig. 1, the load 5 is, for example, a hydrogen production electrolytic tank (hereinafter, simply referred to as an electrolytic tank), a power battery of an electric car, or a corresponding load of a data center.

With continued reference to fig. 1, the controller 4 is communicatively coupled to and capable of interacting with the transformer 2, the modular converter 3, and the load 5. The controller 4 controls the power supply to the load 5 based on feedback information from at least one of the transformer 2, the modular converter 3 and the load 5. In addition, the controller 4 also includes a control strategy for coping with an imbalance situation between the plurality of inverter modules. In addition, the controller 4 also includes a control strategy for optimizing harmonic performance. An embodiment of the control method implemented by the controller 4 will be described in detail in the exemplary method section below.

In one embodiment, the controller 4 is implemented in a distributed control system (not shown) comprising a plurality of controller nodes. For example, the distributed control system includes a controller node on the transformer side, a controller node on the load side, and a controller node on the individual converter module side. In this embodiment, the controller 4 may be integrated with one of the controller nodes on the multiple inverter module side and communicate with the other controller nodes of the distributed control system. The controller 4 may also be provided as a single controller node and integrated with the controller nodes on the individual converter module side to form an intelligent modular converter together with the modular converter.

In another embodiment, the controller 4 may be implemented in a centralized control system (not shown). The centralized control system includes a high-level controller and a plurality of low-level controllers in communication with the high-level controller. For example, the plurality of low-level controllers includes a transformer-side controller, individual converter module-side controllers, and a load-side controller. In this embodiment, the controller 4 may be provided in a high-level controller and communicate with a plurality of low-level controllers. The controller 4 may also be provided in one of a plurality of low-level controls and communicate with a high-level controller.

The controller 4 may be implemented in hardware or software or a combination of software and hardware. For a portion of a hardware implementation, it may be implemented within 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, micro-controllers, microprocessors, electronic units designed to perform their functions, or a combination thereof. For portions implemented in software, they may be implemented by means of microcode, program code or code segments, which may also be stored in a machine-readable storage medium, such as a storage component.

In one embodiment, the controller 4 may be implemented to include a memory and a processor. Stored in the memory are instructions that, when executed by the processor, cause the processor to perform a power supply control method according to an embodiment of the present invention.

One aspect of the invention relates to a modular converter system comprising a modular converter 3 as described above and a controller 4 as described above. Another aspect of the present invention relates to a power supply control method, which can be implemented by the above-described controller. A further aspect of the invention relates to the transformer 2 described above. On the basis of the description of the exemplary system, embodiments of the modular converter 3, the power supply control method implemented by the controller 4, and the transformer 2 are described below, respectively.

Exemplary Modular converter

Fig. 5 shows a modular converter according to an embodiment of the invention. The modular converter 3 shown in fig. 5 comprises 6 converter modules, implemented as a 36-pulse rectification structure, which cooperates with a phase-shifting transformer 2 having 6 sets of secondary-side windings to supply power to the load 5. It will be appreciated that the numbers shown in fig. 5 (e.g., number of inverter modules, number of pulses, phase shift angle) are merely exemplary, and the present invention is not limited thereto.

Referring to fig. 5, the individual converter modules of the modular converter 3 are connected in parallel with each other, and thus may also be referred to as a parallel modular converter. For example, in these inverter modules, the positive output terminals of the first inverters 311 to 361 are connected together and connected to the positive terminal of the dc load 5; and the negative outputs of the second inverters 312-362 are connected together and to the negative terminal of the dc load 5.

Based on such a parallel topology, the plurality of converter modules shunts, and thus the current flowing through each converter module is much smaller relative to the current provided to the load. Also, for each converter module, the partial power processing converter (i.e., the second converter described above) processes only a small portion of the power. Thus, the voltage, current and power transferred to the power electronics constituting the controllable switch of the second converter need to be substantially reduced. Therefore, such a modular converter can greatly reduce the cost of the device and the size.

For clarity, the load 5 is illustrated as an electrolytic cell. It is to be understood that the numerical values set forth in the following examples are intended to be illustrative and not limiting. For example, when the electrolyzer is changed from light to full load operation, the voltage variation range is 30%, where the first converter provides 70% of the load voltage (power), and the partial power handling converter handles only 30% of the power provided to the load, then the second converter of each of the 6 converter modules only needs to handle one sixth of 30%, i.e. 5%.

Such a parallel modular converter is suitable for use in situations where the load is an electrolyzer, because the electrolyzer load is characterized by: the hydrogen production is positively correlated with the cell current and the cell current is positively correlated with the cell voltage. The electrolyzer corresponds to high current and high voltage when operating at full load. The electrolyzer is operated under light load corresponding to low current and low voltage. The parallel modular converter described above can be controlled by the controller 4 to regulate the current and voltage supplied to the load so as to meet the power supply requirements of the electrolyzer.

Such parallel modular converters are also suitable for use in situations where the load is an electric car power battery, as the power battery charging mode includes constant voltage charging and constant current charging. Which charging mode is used is related to the state of charge (SOC) of the power battery. For example, when the SOC is 0 to 95%, constant current charging is employed. Constant voltage charging is used when the SOC is 95% -98% (typically not 100% for battery life). The parallel modular converter can be controlled by the controller 4 to regulate the current and voltage provided to the load so as to meet the power supply requirements of the power battery of the electric automobile.

Fig. 6 shows a modular converter according to another embodiment of the invention.

Similar to fig. 5, the modular converter 3 shown in fig. 6 comprises 6 converter modules, implemented as a 36-pulse rectifier structure, which cooperates with a phase-shifting transformer 2 having 6 sets of secondary-side windings to supply power to the load 5. It will be appreciated that the numbers shown in fig. 6 (e.g., number of inverter modules, number of pulses, phase shift angle) are merely exemplary, and the present invention is not limited thereto.

Referring to fig. 6, the individual converter modules of the modular converter 3 are connected in series with each other, and thus may also be referred to as a series modular converter. For example, the negative output of the second inverter 312 of the first inverter module is connected to the positive output of the first inverter 321 of the second inverter module; the negative output of the second converter 322 of the second converter module is connected to the positive output of the first converter 331 of the third converter module and so on. Based on such a series topology, a high voltage can be supplied to the load 5.

Such a series modular converter 3 is particularly suitable for use in cases where the load is a high voltage rectifying system, for example, as the front end of a high voltage rectifying system, providing it with an adjustable high voltage. One example of an application scenario is an electric haul truck.

In addition, according to an embodiment of the present invention, the outputs of the respective ones of the plurality of converter modules are isolated from each other, since the AC-DC conversion is already done at the front end. In this way, the outputs of the converter modules may be connected to and power a load, respectively, or the outputs of the converter modules may be connected in series or in parallel to and power a load. Fig. 7 and 8 show some examples of the use of a modular converter 3 to supply a plurality of independent loads simultaneously.

Referring to fig. 7, there are shown 3 inverter modules 31-33, each of which is connected to a respective load embodiment. The inverter module 31 connects the load 51 and supplies power to the load 51; the inverter module 32 connects to the load 52 and provides power to the load 52; the inverter module 33 connects the load 53 and supplies power to the load 53. The application scenario of this embodiment is that each converter module is connected to a power battery of an electric vehicle, for example, so that a plurality of electric vehicles can be charged at the same time.

Referring to fig. 8, there are shown 8 inverter modules 31-38, wherein 4 inverter modules 31-34 are connected in series or parallel with each other and commonly connect a load 51 to power load 51; the other 4 inverter modules 35-38 are connected in series or parallel and are commonly connected to a load 52 to power the load 52. An application scenario of this embodiment is for example a modular converter for simultaneously powering a plurality of different scale electrolytic cells.

Exemplary method

An example method is now presented. These methods may be performed using the controller 4 described above. It should be understood that the operations involved in the following methods need not be performed in the exact order described. Conversely, multiple operations may be handled in a different order or simultaneously, and operations may be added or omitted.

Fig. 9 is a flowchart of a method 900 for controlling a modular converter to supply power to a dc load, according to one embodiment of the invention. According to the control strategy of the method 900, the controller 4 controls each converter module to regulate the second dc voltage output by the second converter of each converter module, thereby enabling the supply of power to the load 5 to be controllable.

Referring to fig. 9, at block 910, the controller 4 receives feedback information from at least one of the transformer 2, the modular converter 3, and the load 5. The feedback information may for example be expressed directly or indirectly: the operating state and efficiency of the load, the harmonic performance, the supply current, the supply voltage and the supply power.

For example, the feedback information may comprise measurement information of the primary side and/or the secondary side of the transformer. For example, a measured current and a measured voltage. The feedback information may include status information of the first and second inverter modules of the respective inverter modules. For example, the power, voltage and current converted by the first and second converters of each converter module. The load information may include status information of the load. Such as load power, load current, and load voltage. In one embodiment, when the load is an electrolysis cell, the status information thereof may include: the hydrogen production rate of the electrolytic cell, the current flowing through the electrolytic cell (hereinafter referred to as "cell current"), the voltage across the electrolytic cell (hereinafter referred to as "cell voltage"), the operating efficiency of the electrolytic cell, the health status of the electrolytic cell, the aging index of the electrolytic cell, and the operating status of the electrolytic cell (e.g., full load status, light load status, or overload status).

At block 920, the controller 4 controls the second converter of each converter module to regulate the second dc voltage output thereof based on the received feedback information.

Such regulation control can enable the power supply to the load 5 to be controlled, for example, the power supply to the load can satisfy the operating condition of the load and promote the operation efficiency of the load. Such regulation control is also capable of coping with an imbalance situation between a plurality of converter modules. Such tuning control also enables optimization of harmonic performance. Some embodiments of block 920 are described below.

Fig. 10 illustrates one embodiment of block 920 (block 921). According to this embodiment, the load 5 is an electrolytic cell, and the controller 4 performs regulation control according to a target operation state of the electrolytic cell load.

Referring to fig. 10, at block 9211, the controller 4 determines a target operating state of the electrolytic cell and an actual operating state of the electrolytic cell based on receiving the feedback information. The target operating state of the electrolyzer may be determined by user demand or by advanced controllers based on coordinated control of the system and grid demand (e.g., active, reactive demand). The target operating state may be included in the feedback information and transmitted to the controller 4. The actual operating state of the electrolyzer can be determined by detecting electrolyzer state parameters by means of the electrolyzer-side sensors. The actual operating state may be included in the feedback information and sent to the controller 4.

At block 9212, the controller 4 controls the second inverter of each inverter module to regulate the second dc voltage V ₂ so that the power to the electrolyzer is controlled and so that the operating conditions of the electrolyzer are controlled. For example, when the actual operating state of the electrolytic cell corresponds to the target operating state, the current control is maintained unchanged. When the actual operating state of the electrolytic cell does not coincide with the target operating state, the actual operating state of the electrolytic cell is made to become the target operating state by notification. Some examples of block 9212 are described below.

In one embodiment, if the target operating state of the electrolyzer is full, and the actual operating state of the electrolyzer is full, the controller 4 maintains the current control unchanged.

In another embodiment, if the target operating state of the electrolytic cell is full load, when the actual operating state of the electrolytic cell is operating at the lowest load, the second dc voltage V ₂ is regulated by the controller 4 controlling the second inverter of each inverter module, so that the actual operating state of the electrolytic cell is changed from operating at the lowest load to full load. For example, if the converter system employs a buck topology, the second dc voltage is adjusted to a minimum value within its adjustable range. If the converter system adopts a boost topology, the second DC voltage is regulated to a maximum value within its regulated range.

In yet another embodiment, if the target operating state of the electrolyzer is light-loaded, and the actual operating state of the electrolyzer is light-loaded, the controller 4 maintains the current control unchanged.

In yet another embodiment, if the target operating state of the electrolytic cell is operating at the lowest load, when the actual operating state of the electrolytic cell is full load, the second dc voltage V ₂ is regulated by the controller 4 controlling the second inverter of each inverter module, so that the actual operating state of the electrolytic cell is changed from full load to operating at the lowest load. For example, if the converter system employs a buck topology, the second dc voltage is regulated to a maximum value within its adjustable range. If the converter system adopts a boost topology, the second DC voltage is regulated to a minimum value within its regulated range.

In addition, when the target operation state of the electrolytic tank is overload and the second direct current voltage V ₂ has been adjusted to a limit value (e.g., a maximum value or a minimum value) within its adjustable range, the controller 4 may send a command signal to the controller node on the transformer side to change the tap position of the tap changer coupled to the primary side of the transformer such that both the first direct current voltage V ₁ and the second direct current voltage V ₂ are controlled so that the actual operation state of the electrolytic tank becomes overload.

Fig. 11 shows another embodiment of block 920 (block 922). According to this embodiment, the load 5 is an electrolytic cell, and the controller 4 performs regulation control according to the health status of the electrolytic cell load so that both the operation efficiency and the hydrogen production rate of the electrolytic cell are optimized in the case where the health status thereof is degraded.

Referring to fig. 11, at block 9221, the controller 4 determines whether the SOH of the electrolytic cell is degraded (degradation) based on the received feedback information. For example, the controller 4 compares the current SOH of the electrolytic cell with the historical SOH stored in the controller 4 to determine whether the SOH of the electrolytic cell is degraded.

In the case of a determination of SOH degradation of the electrolyzer, the controller 4 controls the second converter of each converter module to regulate the second dc voltage V ₂, such that the voltage supplied to the electrolyzer is controlled, block 9222.

For example, after SOH of the electrolyzer is degraded, the internal resistance of the electrolyzer is increased, at which time the second DC voltage V ₂ is regulated by the controller 4 controlling the second inverter of each inverter module so that the voltage supplied to the electrolyzer is correspondingly increased to ensure that the hydrogen production rate at that time reaches the target hydrogen production rate without failing to reach the target hydrogen production rate due to SOH degradation of the electrolyzer.

In addition, in this embodiment, it is also possible to control both the first dc voltage V ₁ and the second dc voltage V ₂ by changing the tap position of the tap changer coupled to the primary side of the transformer so that the hydrogen production rate of the electrolytic cell reaches the target hydrogen production rate.

Fig. 12 shows yet another embodiment of block 920 (block 923). According to this embodiment, the controller 4 controls the respective inverter modules such that the load is supplied with a power supply mode, for example, a constant voltage mode or a constant current mode, which satisfies the load demand.

In block 9231, the controller 4 determines whether the demand power mode of the load is a constant voltage mode or a constant current mode based on the received feedback information.

For example, when the load is a power battery of an electric vehicle, the controller determines a demand power mode based on the SOC of the power battery. The rules for determining the power mode may be pre-stored in the controller. For example, the rule is: when the SOC of the power battery is 0-95%, constant current charging is adopted; and when the SOC of the power battery is 95-98%, constant voltage charging is adopted.

At block 9232, the controller 4 controls the second inverter of each inverter module based on the determined power mode such that the power to the load meets the determined power mode.

For example, if the determined power supply mode is a constant voltage mode, the second inverter of each inverter module is controlled so that the voltage supplied to the load is kept constant. If the determined power supply mode is a constant current mode, the adjustment amount of the second direct current voltage is calculated based on the fed back load current and load voltage so that the current supplied to the load remains unchanged.

Fig. 13 shows yet another embodiment of block 920 (block 924). According to this embodiment, the controller 4 handles the situation of a load short circuit by controlling the second inverter.

Referring to fig. 13, in block 9241, the controller 4 determines whether a short circuit fault has occurred in the load according to the feedback information. For example, a short circuit fault is considered to occur when the load current exceeds a predetermined current threshold.

At block 9242, if it is determined that a short circuit fault has occurred to the load, the power electronic switches of the second inverter of each inverter module are controlled to cut off current in the loop. In this way, the current in the loop can be switched by controlling the controllable switch of the second converter. The switching-off mode is fast, so that quick response to load short-circuit faults is realized. Then, in case there is no current in the loop, a switch (not shown) connected between the transformer and the converter module is opened, which may completely disconnect the load from the power supply system.

Fig. 14 shows yet another embodiment of block 920 (block 925). According to this embodiment, when an imbalance situation occurs between the plurality of inverter modules, the plurality of inverter modules are returned to the equilibrium state by the regulation control. Such control is advantageous for a modular converter comprising a plurality of converter modules, since each converter module is optimally harmonically behaved at equilibrium. Moreover, the individual inverter modules have nearly identical lifetimes at equilibrium.

Referring to fig. 14, at block 9251, the controller 4 determines whether an imbalance condition occurs in the plurality of converter modules based on the received feedback information.

In embodiments of the present invention, "balancing" is understood to mean that the power, current and voltage delivered by the individual converter modules all reach a steady state, i.e. the power, current and voltage delivered by the individual converter modules have invariance over time. For the parallel converter modules described above, the main concern is the current transmitted by the individual converter modules. For example, if the currents transmitted by the respective inverter modules are equal, then the plurality of inverter modules are considered to be in a balanced state. For the above-described series converter modules, the main concern is the voltage transmitted by the respective converter module. For example, if the voltages transmitted by the respective converter modules are equal, then the plurality of converter modules are considered to be in a balanced state.

In embodiments of the present invention, an "imbalance" is understood to mean that among a plurality of converter modules, at least one converter module transmits power, current or voltage in an unstable state. The unstable state is, for example, an irregular fluctuation in current or voltage or power over time. The unstable state is also, for example, that at least one of the converter modules transmits a power, current or voltage that is different from the power, current or voltage transmitted by the other converter modules. The unstable state is also, for example, when the power, current or voltage delivered by the converter modules does not correspond to a predetermined proportion.

It will be appreciated that the above definitions of "balance" and "imbalance" constitute rules by which the controller determines whether an imbalance condition occurs in a plurality of converter modules. The rules may be pre-stored in the controller 4.

At block 9252, upon determining that an imbalance condition has occurred for at least one of the plurality of inverter modules, a second inverter of the at least one inverter module is controlled to bring the inverter module back to an equilibrium state.

For clarity, an example of the coping strategies described above with respect to the unbalanced situation is described with reference to fig. 5. As shown, 6 converter modules are connected in parallel, with each converter module providing equal current to the load in a balanced condition. Suppose that such an imbalance situation occurs: the current delivered to the load by the first converter module is not equal to the current delivered to the load by the other 5 converter modules. At this time, the controller 4 calculates a difference between the current transmitted from the first inverter module and the current transmitted from the other inverter modules to the load. The controller 4 then aims to control the second converter of the first converter module with the aim of compensating the difference so that the current delivered to the load by the first converter module is equal to the current supplied to the load by the other converter modules, i.e. the converter modules return to the balanced state again.

Embodiments of the invention also provide a machine-readable storage medium storing executable instructions that, when executed, cause a machine to perform a method as described above.

Exemplary transformers

In accordance with embodiments of the present invention, a number of factors such as harmonic performance, power supply requirements of the end load, rated power and rated current of the converter when the transformer is connected as an energy converter device to the system are considered in providing the geometric parameters of the transformer (e.g., the number of sets of secondary windings, the layout of primary and secondary windings). The transformer thus provided can be a perfect energy converter in the system and transfer energy from one side to the other in an optimal way.

Next, an embodiment of providing the number of secondary side winding groups is described.

First, the minimum number of pulses for the transformer is determined based on the worst case of system harmonic performance. This is because, in various operating states of the system, the situation where the harmonic performance is worst also needs to meet the harmonic requirements of the grid coupled to the AC source (e.g., the harmonic requirements of the PCC points on the grid side) in order to determine the minimum number of pulses of the transformer. The worst case of system harmonics may be different in different application scenarios, and several examples of the worst case of system harmonics are presented below.

In one embodiment, the minimum number of pulses for the transformer is determined taking into account the worst system harmonic performance when operating at the minimum load rate. Specifically, the harmonics generated when operating at the minimum load rate should meet the harmonic requirements of the power grid coupled to the AC source (e.g., the harmonic requirements of the PCC points). For clarity, the cell load will be described below as an example. It should be understood that in the following examples, numerical values are given by way of example only and are not limiting. For example, a 5MW (1000V, 5000A) electrolyzer is operated at 20% of the lowest load rate (i.e., 1 MW), requiring that the harmonic requirements of the PCC point be met (e.g., < 3-5%). Based on such minimum load factor and the harmonic requirement of the PCC point, a minimum number of 36 pulses is calculated, i.e., at least 36 pulses are required to meet the harmonic requirement of the PCC point.

In another embodiment, consider that the system comprises two parts, but only a part of the system has the worst harmonic performance during operation, and the minimum number of pulses of the transformer is determined by this. For clarity, this embodiment is described with reference to fig. 16. The system in fig. 16 includes two parts, each part implemented as 24 pulses, which together constitute 48 pulses. When the system is only partially operated, i.e. at 24 pulses, the harmonics generated in the system need to meet the harmonic requirements of the PCC points. For example, when the system is implemented as 24 pulses consisting of two 12 pulses, if only one set is running, the system is running at 12 pulses, where the harmonic requirement of the PCC is not met. In this case, the system may be implemented to include 48 pulses of two 24 pulses, if only one set is running, the system is running 24 pulses, when the harmonic requirement of the PCC is met. Then, the minimum pulse number of the transformer is determined to be 48 pulses.

In addition, a combination of the cases of the above two embodiments can also be considered as the case where the system harmonic performance is the worst. In other words, the case when the system is operated in one of the two parts and the part is operated at the minimum load is taken as the case where the system harmonic performance is the worst, and the minimum pulse number in this case is determined.

Then, a correction value of the minimum pulse number may be further calculated, that is, a corrected pulse number may be appropriately added to the calculated minimum pulse number to obtain a corrected minimum pulse number, which makes the pulse number of the transformer have a margin against unstable factors such as a fault situation or an unbalance situation. Such redundancy is extremely advantageous for coupling transformers into the system as energy conversion devices, because the transformers so provided take full account of the harmonic performance of the system and can cope to some extent with the instability factors of the system.

The correction value may be calculated based on experimental results and/or models. For example, a harmonic performance optimization model is created according to a specific application, and a harmonic related parameter measured when an unstable factor occurs in the application is brought into the harmonic performance optimization model, thereby obtaining a pulse wave number correction value capable of optimizing the harmonic performance as the correction value of the minimum pulse wave number.

Then, the number of winding groups on the secondary side is calculated from the corrected minimum pulse number. The set of numbers may be calculated according to the following formula: n= 6*n, where N is the corrected minimum number of pulses; n is the number of winding groups on the secondary side. In one embodiment, the number of pulses N is 108 or less and the number of groups N is2 or more.

Next, the number of winding sets on the secondary side is optimized, and the optimized number of winding sets is taken as the number of winding sets on the secondary side of the transformer, by one or more of the following factors: the power requirements of the end load, the modular design requirements, the economics of the converter modules, the power rating and current rating of the converter modules.

In one embodiment, the optimizing the number of winding sets may be expanding the number of winding sets determined in the manner described above. For example, 6 groups are expanded to 12 groups, so that the voltage, current and power handled by each converter module to be tolerated are reduced, whereby low cost and suitable power electronics can be selected. Thus, while the number of devices is increased, the overall cost of the devices is greatly reduced.

It should be understood that the manner of expanding the number of groups by a multiple in the above example is only an example, and other manners of expanding the number of groups may be also included according to embodiments of the present invention.

Then, the phase angles of the secondary windings are determined on the basis of the number of pulses of the transformer and the number of secondary winding groups. It will be appreciated that the number of pulses at this time can be calculated according to the above formula n= 6*n. Here, N is the number of secondary-side winding groups finally determined, and the number of pulses N is obtained. For clarity, 36 pulse waves are described below as an example.

For example, if the determined number of groups is 6, the pulse number N is 36 (i.e., 6*6 =36). At this time, the inter-group phase shift angle of the secondary side winding is determined according to the formula 360 °/N (N is the number of pulses), that is, the inter-group phase shift angle is 10 °. In other words, the winding phase angles of adjacent groups are sequentially increased or decreased by 10 °. After the phase shift angle between groups is determined, the phase angles of the individual windings may be determined in the following manner. In one embodiment, two winding phase angles of 5 DEG and-5 DEG are determined according to a virtual 0 DEG phase as a reference, and so on, two winding phase angles of 15 DEG and-15 DEG are determined, and two winding phase angles of 25 DEG and-25 DEG are determined. In another embodiment, there is a certain demand phase angle (e.g., the demand phase angle is a customized demand for a particular application), where one winding phase angle is first determined as the demand phase angle, and then the other winding phase angles are determined by sequentially increasing 10 ° or decreasing 10 °. For example, the required phase angle is 30 °, then first one 30 ° winding phase angle is determined with respect to the virtual 0 ° phase as reference, and then the other winding phase angles are determined by sequentially increasing or decreasing by 10 °, for example, the other winding phase angles are 20 °,10 °,0 °,10 ° and-20 °.

Some examples of the layout of the primary side winding and the secondary side winding of the transformer are described below with reference to fig. 15-18.

Fig. 15 shows a transformer according to an embodiment of the invention. As shown in fig. 15, the number of primary side windings is 1, i.e., the primary side has one primary winding W. The secondary side windings are arranged in a high power winding and a low power winding spaced apart arrangement. Thus, the secondary side windings are arranged in the following order: high power winding a-1- & gt low power winding b-1- & gt high power winding a-2- & gt low power winding b-2- & gt. Moreover, the height of the primary winding W corresponds to the total height of the secondary side winding. For example, half the height of the primary winding W is aligned with half the total height of the secondary side winding.

Fig. 16 shows a transformer according to another embodiment of the invention. As shown in fig. 16, the number of primary side windings is 2, i.e., the primary side has two primary windings W1 and W2. Each primary winding is split to half the transformer capacity. The secondary side winding is arranged in two parts, each part corresponding in height to one primary winding and receiving the power transmitted by that primary winding. In each of the two portions of the secondary side winding, the high power winding and the low power winding are arranged at intervals. For example, referring to fig. 16, one portion of the secondary side includes high-power secondary windings a1-a4 and low-power secondary windings b1-b4, and the arrangement order of these secondary windings is: high power winding a-1- & gt low power winding b-1- & gt high power winding a-2- & gt low power winding b-2- & gt. The other part of the secondary side comprises high power secondary windings a5-a8 and low power secondary windings b5-b8, and the secondary windings are arranged in the following order: high power winding a-5- & gtlow power winding b-5- & gthigh power winding a-6- & gtlow power winding b-6- & gt.

In addition, according to another embodiment of the invention (not shown), the primary side comprises three primary windings and the secondary side windings are arranged in three parts. The implementation of this embodiment is similar to the embodiment of fig. 16 and will not be repeated.

In addition, designing the primary side of the transformer to include two or more primary windings is helpful for ampere-turn balancing of the transformer in the event of an unbalanced load condition or fault condition on the secondary side. In other words, when the primary side of a transformer comprises two or more primary windings, such a transformer has a better ampere-turn balance in case of a load imbalance situation or a fault situation.

Fig. 17 shows a transformer according to a further embodiment of the invention. As shown in fig. 17, the number of primary side windings is 2, i.e., the primary side has two primary windings W1 and W2. The two primary windings are split into different ratios of transformer capacity, i.e. one primary winding is split into more transformer capacity and the other primary winding is split into less transformer capacity. The different ratio may be determined from a ratio between the power processed by the secondary-side coupled partial power processing converter (e.g., the second converter described above) and the total power transmitted by the converter modules. For example, for the inverter module 31, the ratio between the power transmitted by the first inverter and the power transmitted by the second inverter is 8:2. It may be arranged that one primary winding gives 80% of the transformer capacity and the other primary winding W2 gives 20% of the transformer capacity. In this embodiment, one portion of the secondary side includes high-power secondary windings a1-a8, and the order of arrangement of these secondary windings is: high power winding a-1→high power winding a-2→high power winding a-8. The other secondary side part comprises low power secondary windings b1-b8 and the order of arrangement of these secondary windings is: low power winding b-1→low power winding b-2→the term.

Fig. 18 shows a transformer according to a further embodiment of the invention. In this embodiment, the transformer further comprises an additional winding W' for powering accessories in the system (e.g. cooling means, heating means, etc.).

In addition, the transformer according to an embodiment of the present invention may further include a tap changer on a primary side of the transformer, the tap changer having a plurality of selectable tap positions. The change of the tap position may be achieved by control of the controller, or by manually changing the tap position, so that power of different voltage levels is transferred from the primary side to the secondary side. In this way, the flexibility of powering the load can be further increased in order to meet the customised requirements of the power supply for the load.

It will be appreciated that the controller described above may be implemented in a variety of ways. For example, it may be implemented as hardware, software, or a combination thereof.

The controller may include one or more processors. These processors may be implemented using electronic hardware, computer software, or any combination thereof. Whether such processors are implemented as hardware or software will depend upon the particular application and the overall design constraints imposed on the system. By way of example, a processor, any portion of a processor, or any combination of processors presented in this disclosure may be implemented as a microprocessor, microcontroller, digital Signal Processor (DSP), field Programmable Gate Array (FPGA), programmable Logic Device (PLD), state machine, gate logic, discrete hardware circuits, and other suitable processing components configured to perform the various functions described herein. The functions of the present invention of the processor, any portion of the processor, or any combination of processors may be implemented as software executed by a microprocessor, microcontroller, DSP or other suitable platform.

Software may be construed broadly to mean instructions, instruction sets, code segments, program code, programs, subroutines, software modules, applications, software packages, routines, subroutines, objects, threads of execution, procedures, functions, and the like. The software may reside in a computer readable medium. Computer-readable media may include, for example, memory, which may be, for example, a magnetic storage device (e.g., hard disk, floppy disk, magnetic strips), optical disk, smart card, flash memory device, random Access Memory (RAM), read-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM), electrically Erasable PROM (EEPROM), registers, or removable disk. Although the memory is shown separate from the processor in various aspects of the invention, the memory may also be located within the processor (e.g., in a cache or register).

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Accordingly, the claims are not intended to be limited to the aspects shown herein. All structural and functional equivalents to the elements of the various aspects described herein that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims.

Claims

1. A converter system for powering a dc load, comprising:

a modular converter comprising two or more converter modules coupled between two or more sets of secondary side windings of the phase-shifting transformer and the dc load, each converter module comprising a first converter for outputting a first dc voltage and a second converter for outputting a second dc voltage; and

And a controller configured to control each of the converter modules to regulate a second DC voltage output by a second converter of each of the converter modules.

2. The converter system of claim 1, wherein the first converter and the second converter are connected in series and a sum of the first dc voltage and the second dc voltage is provided to the dc load.

3. The converter system of claim 1, wherein the second converter and the dc load are connected in series and a difference between the first dc voltage and the second dc voltage is provided to the dc load.

4. A converter system according to any of claims 1-3, wherein the outputs of the two or more converter modules are connected in parallel.

5. A converter system according to any of claims 1-3, wherein the outputs of the two or more converter modules are connected in series.

6. The converter system of any of claims 1-5, wherein the controller is configured to:

receiving feedback information from at least one of the transformer, the modular converter, and the dc load; and

The second converter of each converter module is controlled based on the feedback information to regulate a second direct current voltage output by the second converter of each converter module.

7. The converter system of any of claims 6, wherein the controller is configured to:

Determining whether an imbalance condition occurs in the two or more converter modules based on the feedback information;

upon determining that an imbalance condition occurs for at least one of the inverter modules, a second inverter of the at least one inverter module is controlled such that the at least one inverter module returns to an equilibrium condition.

8. The converter system of claim 6 or 7, wherein the controller is configured to:

Determining whether a short circuit fault occurs to the direct current load based on the feedback information; and

And controlling the second converter of each converter module to disconnect the direct current load from the power supply loop thereof when the direct current load is determined to have a short circuit fault.

9. The converter system of any of claims 6-8, wherein the controller is configured to:

determining whether a power supply mode required by the direct current load is a constant voltage mode or a constant current mode based on the feedback information; and

The second converter of each converter module is controlled such that the supply of power to the dc load meets its required supply mode.

10. The converter system of any of claims 6-9, wherein the controller is configured to perform for a case where the dc load is an electrolyzer:

the second DC voltage is regulated by controlling the second inverter of each inverter module when the actual operating state of the electrolytic cell does not coincide with the target operating state, so that the actual operating state of the electrolytic cell becomes the target operating state.

11. The converter system of any of claims 6-10, wherein the controller is configured to perform for a case where the dc load is an electrolyzer:

In case the operating state of the electrolyzer is an overload state and the second DC voltage is a limit value of its regulation range, a command signal is generated for changing the tap position of a tap changer coupled to the primary winding of the transformer such that both the first DC voltage and the second DC voltage are controlled.

12. The converter system of any of claims 6-11, wherein the controller is configured to perform for a case where the dc load is an electrolyzer:

determining whether the health status of the electrolyzer is degraded based on the feedback information; and

In the event that a degradation in the health of the electrolyzer is determined, the second converter of each converter module is controlled to regulate the second direct voltage such that the hydrogen production rate of the electrolyzer is controlled.

13. The converter system of any of claims 1-12, wherein each of the two or more converter modules is coupled to and powers one of a plurality of independent loads.

14. The converter system of any of claims 1-12, wherein one or more of the two or more converter modules collectively power a load in a series or parallel connection.

15. A method for controlling a modular converter to power a dc load, the modular converter comprising two or more converter modules coupled between two or more sets of secondary side windings of a phase shifting transformer and the dc load, each converter module comprising a first converter for outputting a first dc voltage and a second converter for outputting a second dc voltage, the method comprising:

Each converter module is controlled to regulate a second dc voltage output by a second converter of each converter module.

16. A controller for controlling a modular converter to power a dc load, comprising one or more processors configured to perform the method of claim 15.