Control Device and Control Method of Distributed Power Conversion System

Abstract

The present invention provides a control device and a control method for a distributed power conversion system. The distributed power conversion system includes N power modules connected in parallel, where N is a positive integer greater than 1. The control method includes: configuring N control units to respectively control the N power modules, and each control unit is used to execute: Step S1, generating a first quantity Q1 reflecting the respective module number R according to a coordination quantity; Step S2, generating a second quantity Q2 reflecting the optimal number of operating modules M; Step S3, comparing the first quantity Q1 and the second quantity Q2. Wherein, when the first quantity Q1 is greater than the second quantity Q2, the corresponding power module stops operating; when the first quantity Q1 is less than or equal to the second quantity Q2, the corresponding power module is put into operation. By using the coordination quantity to coordinate the operation between modules in the distributed power conversion system, the present invention improves the system efficiency, reduces the output voltage and output current ripple, and realizes the balanced operation between modules.

Description

Technical Field

[0001] The present invention relates to the field of power electronics technology, and in particular, to a control device and a control method for a distributed power conversion system. Background Art

[0002] With the progress of distributed new energy power generation technology and the increasing number of DC electrical equipment, the demand for DC power distribution is rising day by day, such as high-power energy storage power conditioning systems (PCS), ultra-fast electric vehicle charging stations, rail transit, medium-voltage power electronic transformer (MV-PET) systems, etc. Due to the limitation of the power of a single module, it is usually necessary to use multiple modules in parallel combination (at least one port in parallel) to achieve the application of low voltage and large current on the DC side, as Figures 1A to 1C shown, which respectively show the structures of parallel combination systems such as solid state transformers (SST), input series output parallel (ISOP) DC / DC converters, input parallel output parallel (IPOP) DC / DC converters, etc.

[0003] To meet the system operation requirements, the DC / DC converter also needs to have functions such as high-frequency isolation, wide-range voltage regulation, and bidirectional operation. Usually, an isolated resonant DC / DC converter can be selected. To reduce the switching loss and improve the efficiency, the isolated resonant DC / DC converter operates in a burst mode under light load, as Figure 1D shown. If the D2D modules are controlled in an isolated and decentralized manner without coordination, when each DC / DC converter starts and stops simultaneously under light load, the output voltage ripple is large and a large output capacitor is required.

[0004] Since the inherent losses such as switching loss, drive loss, and conduction loss account for a relatively large proportion under light load, the efficiency of the isolated resonant DC / DC converter is low under light load, as Figure 1E shown. Currently, most modular parallel converters adopt the power sharing mode, that is, regardless of whether they are operating at full power or not, all modules share the system power equally, resulting in low-power operation of each module in the light load mode and low efficiency. Therefore, in the light load case, if the system loss can be reduced, it will be beneficial to improve the overall operation efficiency of the system.

[0005] The prior art has one or more problems in that it cannot ensure input voltage sharing for an input series system, has high communication rate requirements, cannot ensure that all conversions have equal operation times, cannot avoid inconsistent aging degrees of converters, needs to consider the single point failure of a centralized controller, and increases costs. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a control device and a control method for a distributed power conversion system, which determine the modules put into operation by sorting the coordination quantities between power converters, without a centralized controller, thereby reducing costs.

[0007] To achieve the above object, according to an embodiment of the present invention, a control method for a distributed power conversion system is provided. The distributed power conversion system includes N power modules connected in parallel, where N is a positive integer greater than 1. The control method includes:

[0008] Configuring N control units to respectively control the N power modules, and each of the control units is used to execute:

[0009] Step S1: Generate a first quantity Q1 reflecting the respective module numbers R according to a coordination quantity;

[0010] Step S2: Generate a second quantity Q2 reflecting the optimal number of operating modules M;

[0011] Step S3: Compare the first quantity Q1 and the second quantity Q2, where,

[0012] When the first quantity Q1 is greater than the second quantity Q2, the corresponding power module stops operating;

[0013] When the first quantity Q1 is less than or equal to the second quantity Q2, the corresponding power module is put into operation.

[0014] In an embodiment of the present invention, the first quantity Q1 = k * R, and the second quantity Q2 = k * M, where k is a positive number.

[0015] In an embodiment of the present invention, the operating time of each power module is the same within one carrier period.

[0016] In an embodiment of the present invention, in step S1, each control unit compares its own coordination quantity with the coordination quantities of other power modules to obtain its own ranking, and uses the ranking as its own module number.

[0017] In an embodiment of the present invention, the coordination quantity is one of the following information: voltage, operating time, temperature, current, power, and carrier wave.

[0018] In an embodiment of the present invention, the voltage is the series-side voltage of the distributed power conversion system; the operation time is the operation time when the power module is put into operation; the current is the input current, output current or inductor current of the distributed power conversion system; the power is the input power or output power of the power module.

[0019] In an embodiment of the present invention, the coordination quantity is a carrier wave, and step S1 includes:

[0020] Step S11: Each control unit configures the carrier period and carrier peak value of the corresponding power module, where the carriers of adjacent power modules are phase-shifted by 2π / N, and the phase-shifting order of each power module is determined by the ID number of each power module;

[0021] Step S12: Each control unit uses the carrier amplitude of the corresponding power module as the coordination quantity for communication and compares it with the carrier amplitudes of other power modules to obtain their respective rankings, and uses the rankings as their respective module numbers, and generates a first quantity Q1 reflecting their respective module numbers R;

[0022] Moreover, in step S2, each control unit generates a second quantity Q2 reflecting the optimal number of operating modules M respectively;

[0023] Moreover, in step S3, each control unit compares the second quantity Q2 with the first quantity Q1 to generate a corresponding drive signal to drive the corresponding power module to be put into operation or stopped.

[0024] In an embodiment of the present invention, step S2 further includes:

[0025] Step 21: Optimize the optimal number of operating modules M, which includes:

[0026] Determine the optimal efficiency point power P corresponding to the best efficiency point of the N power modules opt ;

[0027] Multiply the average output power P of the N power modules local by the total number of power modules N to obtain the total system power of the distributed power conversion system, and calculate the integer part of the ratio of the total system power to the optimal efficiency point power P opt to obtain the operation calculation value M cal ;

[0028] Determine the optimal number of operating modules M = M cal or M cal +1 according to the principle that the operating power of a single module is closest to the best efficiency point.

[0029] In one embodiment of the present invention, the algorithm for determining the optimal number of operating modules M is as follows:

[0030]

[0031] Wherein, if then M = M cal + 1; otherwise M = M cal .

[0032] In one embodiment of the present invention, each of the power modules includes a first port, and the first ports of the N power modules are connected in parallel.

[0033] In one embodiment of the present invention, each of the power modules is a first-level power module, which has a first-level power conversion unit.

[0034] In one embodiment of the present invention, each of the power modules is a second-level power module, which has a cascaded first-level power conversion unit and a second-level power conversion unit. Wherein, when the power module is put into operation or stopped, the first-level power conversion unit or the second-level power conversion unit is put into or stopped, or the first-level power conversion unit and the second-level power conversion unit are put into or stopped simultaneously.

[0035] In one embodiment of the present invention, when one of the power modules is selected to be put into operation, the power module put into operation is in the hiccup mode.

[0036] According to another embodiment of the present invention, the present invention further provides a control device for a distributed power conversion system, characterized in that the distributed power conversion system includes N power modules connected in parallel, where N is a positive integer greater than 1, and the control device includes:

[0037] N control units, respectively corresponding to control the N power modules, and each of the control units includes:

[0038] A serial number generation unit, configured to generate a first quantity Q1 reflecting the respective module serial number R according to a coordination quantity;

[0039] A module quantity calculation unit, configured to generate a second quantity Q2 reflecting the optimal number of operating modules M;

[0040] A comparison unit, configured to compare the first quantity Q1 and the second quantity Q2. Wherein, when the first quantity Q1 is greater than the second quantity Q2, the corresponding power module stops operating; when the first quantity Q1 is less than or equal to the second quantity Q2, the corresponding power module is put into operation.

[0041] In another embodiment of the present invention, the first quantity Q1 = k * R, and the second quantity Q2 = k * M, where k is a positive number.

[0042] In another embodiment of the present invention, the operating time of each of the power modules is the same within one carrier period.

[0043] In another embodiment of the present invention, the sequence number generating unit of each of the control units compares its respective coordination quantity with the coordination quantities of the other power modules to obtain its respective ranking, and uses the ranking as its respective module sequence number.

[0044] In another embodiment of the present invention, the coordination quantity is one of the following information: voltage, operating time, temperature, current, power, and carrier.

[0045] In another embodiment of the present invention, the voltage is the series-side voltage of the distributed power conversion system; the operating time is the operating time when the power module is put into operation; the current is the input current, output current, or inductor current of the distributed power conversion system; the power is the input power or output power of the power module.

[0046] In another embodiment of the present invention, the coordination quantity is a carrier, where:

[0047] The sequence number generating unit of each of the control units configures the carrier period and carrier peak value of the corresponding power module, where the carriers of adjacent power modules are phase-shifted by 2π / N, and determines the phase-shift order of each power module according to the ID number of each power module; and uses the carrier amplitude of the corresponding power module as the coordination quantity for communication and compares it with the carrier amplitudes of the other power modules to obtain its respective ranking, and uses the ranking as its respective module sequence number, and generates a first quantity Q1 reflecting its respective module sequence number R;

[0048] The module quantity calculating unit of each of the control units respectively generates a second quantity Q2 reflecting the optimal operating quantity M of the modules;

[0049] The comparison unit of each of the control units compares the second quantity Q2 with the first quantity Q1 to generate a corresponding drive signal to drive the corresponding power module to be put into operation or stopped.

[0050] In another embodiment of the present invention, the module quantity calculating unit is further used to optimize the optimal operating quantity M of the modules put into operation, where:

[0051] The module quantity calculating unit determines the optimal efficiency point power P corresponding to the optimal efficiency point of the N power modules opt ;

[0052] The module quantity calculation unit multiplies the average output power P of the N power modules local by the total number N of power modules to obtain the total system power of the distributed power conversion system, and the ratio of the total system power to the power P at the optimal efficiency point opt is calculated and rounded to obtain the operation calculation value M cal ;

[0053] The module quantity calculation unit determines the optimal operation quantity M of the modules put into operation according to the principle that the operation power of a single module is closest to the optimal efficiency point, where M = M cal or M cal + 1.

[0054] In another embodiment of the present invention, the algorithm for the module quantity calculation unit to determine the optimal operation quantity M of the modules put into operation is as follows:

[0055]

[0056] Wherein, if then M = M cal + 1; otherwise M = M cal .

[0057] In another embodiment of the present invention, each of the power modules includes a first port, and the first ports of the N power modules are connected in parallel.

[0058] In another embodiment of the present invention, each of the power modules is a first-level power module, which has a first-level power conversion unit.

[0059] In another embodiment of the present invention, each of the power modules is a second-level power module, which has a cascaded first-level power conversion unit and a second-level power conversion unit. Wherein, when the power module is put into operation or stopped, the first-level power conversion unit or the second-level power conversion unit is put into or stopped, or the first-level power conversion unit and the second-level power conversion unit are simultaneously put into or stopped.

[0060] In another embodiment of the present invention, when one of the power modules is put into operation, the power module put into operation is in the hiccup mode.

[0061] For a distributed power conversion system including N power modules connected in parallel, the control method of the present invention can perform coordinated operation of the modules on the system through the coordination amount between the power modules, improve the system efficiency, reduce the output voltage and output current ripple, and achieve balanced operation between the modules. The control method of the present invention is simple and reliable. Compared with the existing solutions, it does not require a central controller, avoids the single-point failure problem of the central controller, and reduces the cost.

[0062] By sequentially switching all power modules in a certain order, the present invention has a stronger ability to regulate the voltage equalization of the dc-link (direct current link), does not affect the power transmission characteristics of the converter, has a low communication rate requirement, and is applicable to distributed power conversion systems with multiple modules in parallel, such as including but not limited to data centers, charging stations, energy storage, and microgrids, etc.

[0063] Additional aspects and advantages of the present invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. Brief Description of the Drawings

[0064] By describing its exemplary embodiments in detail with reference to the drawings, the above and other features and advantages of the present invention will become more apparent.

[0065] Figure 1A 、 Figure 1B and Figure 1C are respectively schematic structural diagrams of parallel combination systems such as SST, ISOP D2D, and IPOP D2D of the prior art;

[0066] Figure 1D is a schematic diagram of the operating state of an existing isolated resonant DC / DC converter in burst mode under light load;

[0067] Figure 1E is a schematic diagram of the efficiency of an existing isolated resonant DC / DC converter;

[0068] Figure 2 is a schematic diagram of the control method of the distributed power conversion system of the present invention;

[0069] Figure 3A 、 Figure 3B and Figure 3C are respectively schematic diagrams of the technical effects of the coordinated control method of the distributed power conversion system of the present invention under different operating states at different system load powers;

[0070] Figure 3D is a schematic diagram of the method for coordinately operating and controlling N power modules of the system by using a carrier wave as a coordination quantity in the present invention;

[0071] Figure 4A and Figure 4B are respectively schematic diagrams of the module switching levels during sequential switching for a two-stage converter in the present invention, where Figure 4A is the first-level switching, Figure 4B is the second-level switching;

[0072] [[ID=~ is a schematic diagram of the simulation model for simulation of the present invention taking two-module input series output parallel as an example;

[0073] ​ For ​ Schematic diagram of simulation results when the shown simulation model adopts module uncoordinated control (A) and module coordinated control (B) under light load;

[0074] ​ For ​ Schematic diagram of simulation results when the shown simulation model adopts module uncoordinated control (A) and module coordinated control (B) under heavy load;

[0075] ​ Schematic structural diagram of the control device of the distributed power conversion system of the present invention for realizing distributed coordinated operation. Specific embodiments

[0076] Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. Like reference numerals in the figures denote like or similar structures and thus their detailed description will be omitted.

[0077] When introducing the elements / components / etc. described and / or illustrated herein, the terms "a", "an", "the", "said" and "at least one" are used to denote the presence of one or more elements / components / etc. The terms "comprising", "including" and "having" are used to mean an open inclusion and mean that there may be additional elements / components / etc. in addition to the listed elements / components / etc. Relative terms such as "upper" or "lower" may be used in the embodiments to describe the relative relationship of one component of the icon to another component. It can be understood that if the device of the icon is turned upside down, the component described on the "upper" side will become the component on the "lower" side. In addition, the terms "first", "second", etc. in the claims are only used as labels and are not numerical limitations on their objects.

[0078] The present invention provides a control method for a distributed power conversion system, wherein the distributed power conversion system is a parallel combination system, which for example includes N power modules connected in parallel, and N is a positive integer greater than 1. Wherein, each power module may include a first port, and the first ports of these power modules are connected in parallel. In the present invention, the parallel combination system may be, for example, but not limited to, systems such as SST, ISOP, IPOP, etc. In the present invention, by configuring N control units, the N power modules can be respectively controlled, as ​ shown, wherein each control unit can be used to execute:

[0079] Step S1: Generate a first quantity Q1 that reflects the respective module numbers R according to a coordination quantity;

[0080] Step S2: Generate a second quantity Q2 that reflects the optimal number of operating modules M;

[0081] Step S3: Compare the first quantity Q1 and the second quantity Q2. Among them, when the first quantity Q1 is greater than the second quantity Q2, the corresponding power module stops operating; when the first quantity Q1 is less than or equal to the second quantity Q2, the corresponding power module is put into operation.

[0082] In the present invention, the operating time of each power module within one carrier cycle can be the same. And when selecting a power module to be put into operation, the power module put into operation is, for example, in the hiccup mode.

[0083] In step S1, each control unit compares its own coordination quantity with the coordination quantities of other power modules to obtain its own ranking, and uses the ranking as its own module number. The coordination quantity can be, for example, one of the following information: voltage, operating time, temperature, current, power, and carrier. Among them, the voltage can be, for example, the series-side voltage of the distributed power conversion system. The operating time can be, for example, the operating time when the power module is put into operation. The current can be, for example, the input current, output current, or inductor current of the distributed power conversion system. The power can be, for example, the input power or output power of the power module. However, it can be understood that the coordination quantity is not limited to the above information, and it can also be other information, which are not regarded as limitations to the present invention. The present invention coordinates the operation of the system through the coordination quantity between power modules, can improve the system efficiency, reduce the output voltage and output current ripple, and achieve balanced operation between modules.

[0084] For example, taking the coordination quantity as the carrier as an example, step S1 may include:

[0085] Step S11: Each control unit configures the carrier cycle and carrier peak value of the corresponding power module, where the carriers of adjacent power modules are phase-shifted by 2π / N, and the phase-shifting order of each power module is determined by the ID number of each power module;

[0086] Step S12: Each control unit uses the carrier amplitude of the corresponding power module as the coordination quantity for communication and compares it with the carrier amplitudes of other power modules to obtain its own ranking, and uses the ranking as its own module number to generate a first quantity Q1 that reflects its own module number.

[0087] Among them, in the step S2, for example, each control unit generates a second quantity Q2 that reflects the optimal number of operating modules. The first quantity Q1 that reflects the respective module numbers can be the same as the respective module numbers R or a quantity that reflects the respective module numbers R obtained according to certain rules. Similarly, the second quantity Q2 that reflects the optimal number of operating modules can be the same as the optimal number of operating modules M or a quantity that reflects the optimal number of operating modules M obtained according to certain rules, and the two rules are the same. In a preferred embodiment, the first quantity Q1 has a linear relationship with the module number R, that is, Q1 = k * R, and the second quantity Q2 also has a linear relationship with the optimal number of operating modules M, that is, Q2 = k * M, where k is a positive number. Of course, other rules can also be adopted to obtain the first quantity Q1 and the second quantity Q2, and the present case is not limited thereto.

[0088] Among them, in the step S3, each control unit, for example, compares the second quantity Q2 with the first quantity Q1 to generate a corresponding drive signal to drive the corresponding power module to operate or stop operating.

[0089] Such as ​ 、 ​ and ​ shown, which respectively show the technical effects of the coordinated control method of the present invention in different operating states under different system load powers. Taking the parallel connection of 4 D2D modules with a rated power of 15 kW as an example, it is assumed that a single module enters the burst mode when the power is below 3 kW. As ​ shown, if the load power is 10 kW and the decentralized control operation is performed, that is, the coordinated control method is not enabled, all power modules enter the operating state of the burst mode, and the output voltage ripple is large. As ​ shown, if the coordinated control method is enabled, the module alternate rotation operation is adopted, and only two of the modules are enabled to operate at each moment, and each module undertakes a power of 5 kW, then all power modules do not enter the operating state of the burst mode, and the total power of the entire system is continuous, and the output voltage ripple is reduced. As ​ shown, when the load power is 2.5 kW, the load power is less than the power at which a single module enters the burst mode. At this time, only one module is enabled to operate at the same moment. Through the alternate rotation operation of all modules, although the total power of the system is not continuous, in the case of the same output filter capacitor, the voltage ripple is reduced to 1 / 4. Different patterns in the figure represent different power modules, and the power modules operating simultaneously are represented on the same vertical axis. It can be seen that through the coordinated control operation of the present invention, the number of operating modules also decreases as the power decreases, so the system can always operate in the high-efficiency range.

[0090] Next, taking the carrier wave as the coordination quantity as an example, the coordinated operation control method of the distributed power conversion system of the present invention will be further described in detail. As ​As shown, first, the carrier period \(T_{carrier}\) is selected, the carrier peak value is configured as \(N\) (where \(N\) is the total number of power modules), the carriers of adjacent power modules are phase-shifted by \(2\pi / N\), and the phase-shifting order of each power module is determined by the ID number of each power module. For example, the figure includes 4 power modules, namely modules Cell1 to Cell4, and the corresponding carriers are phase-shifted by \(2\pi / 4\) in sequence. Then, the carrier amplitudes of each power module are used as coordination quantities for communication and compared with the coordination quantities of other power modules to obtain the ranking of this power module, which is also output as its own module serial number \(R\) (\(1\leq R\leq N\)), that is, the first quantity \(Q1\) reflecting their respective module serial numbers is generated. For example, \(Q1 = R\), as ​ the solid lines in the second to fifth waveforms in [reference] represent the value of \(Q1\) at the current moment. If \(M\) (\(1\leq M\leq N\)) modules are put into operation (i.e., the optimal number of operating modules is \(M\)), the modulation wave is \(M\), that is, the second quantity \(Q2\) reflecting the optimal number of operating modules is generated. For example, \(Q2 = M\), as ​ the dashed lines in the second to fifth waveforms in [reference] represent the value of \(Q2\) at the current moment. Among them, if \(R\leq M\), the corresponding power module is put into operation, that is, cut in; if \(R > M\), the corresponding power module stops operating, that is, cut out.

[0091] In this embodiment, since the carrier phase is related to the ID number and the ID number has been determined during module initialization, real-time communication may not be required. In addition, information such as the series-side voltage, operating time, temperature, current, and power can also be used as coordination quantities for communication to achieve distributed coordinated operation control. In this way, the rotation of modules can be automatically realized, and the rotation period can be flexibly configured by the carrier period. This control method of the present invention has low requirements for communication rate, which is beneficial to the implementation of the distributed controller. At the same time, multiple modules rotate in operation, which can avoid inconsistent aging degrees of each module. For the input series system, high-speed switching can ensure the voltage sharing of the DC-link.

[0092] In an embodiment of the present invention, each power module can be a first-level power module, which can have a first-level power conversion unit. In other embodiments, each power module can also be a second-level power module, which can have a cascaded first-level power conversion unit and a second-level power conversion unit. And when the power module is put into operation or stops operating, it is to put into or stop the first-level power conversion unit or the second-level power conversion unit, or to put into or stop the first-level power conversion unit and the second-level power conversion unit at the same time. For example, as ​ and ​ shown, for a two-level converter, only one level can be switched alternately. For example, ​ only the second-level D2D units of each module Cell 1 to Cell n are switched in [reference], or both levels can be switched, for example, ​The first - stage A2D units and the second - stage D2D units of each module Cell 1 to Cell n in it are switched on and off simultaneously.

[0093] In the present invention, in order to optimize the system efficiency and reduce the output voltage ripple, the optimal number of operating modules M can also be optimized. In other words, the step S2 may further include: Step 21, optimizing the optimal number of operating modules M. Among them, the optimization method may include, for example: First, determine the optimal efficiency point power P corresponding to the best efficiency points of N power modules opt ; Secondly, multiply the average output power P of N power modules local by the total number of power modules N to obtain the total system power of the distributed power conversion system. The ratio of the total system power to the optimal efficiency point power P opt is calculated and rounded to obtain the operation calculation value M cal ; Then, according to the principle that the operating power of a single module is closest to the optimal efficiency point, determine the optimal number of operating modules M = M cal or M cal +1.

[0094] In the present invention, the algorithm for determining the optimal number of operating modules M is as follows:

[0095]

[0096] Among them, if [[ID=2,5]] then M = M cal +1; otherwise M = M cal .

[0097] Taking 15kW * 4 modules as an example, assume that the optimal efficiency point is P opt = 7.5kW, and the optimal efficiency range is 5kW - 10kW. Assume that the power entering the Burst mode is P burst = 3kW. The corresponding number of operations for the total power range calculated by the above - mentioned optimization algorithm is shown in Table 1. As the power decreases, the number of operations is reduced to ensure that each module operates near the optimal efficiency point above 10kW. And after adopting the coordinated control method of the present invention, the boundary power of the system entering the Burst mode drops from 12kW to 3kW.

[0098] ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

[0099] Table 1 Example of optimizing the number of operations

[0100] Taking the input series - output parallel connection of two modules Cell 1 and Cell 2 as an example for simulation, the simulation model is as ​ shown. The simulation results are as ​ and ​As shown, where PWM_en is the switching signal for the switching-in and switching-out of Module Cell1 and Module Cell2, 1 represents switching-in, and 0 represents switching-out; V dc is the input voltage of the two modules, and i o is the output current of the two modules, and V o is the output voltage, and f s is the converter control variable. ​ In the left figure (A) and the right figure (B) in [Figure reference], the load conditions are the same, but the load is relatively light (i.e., light load). When coordinated control is not enabled in the left figure (A), both Module Cell 1 and Module Cell 2 are switched in and running. Each module undertakes less power (when the output voltages are equal, the output current of a single module during operation is relatively low). Each module is in the Burst mode of operation, and the output voltage ripple is relatively large. After coordinated control is enabled in the right figure (B), Module Cell 1 and Module Cell 2 operate alternately. The power borne by a single module increases (when the output voltages are equal, the output current of a single module during operation is relatively high). The operating state of the system changes from the Burst mode to continuous operation of the system, and the output voltage ripple decreases. ​ In the left figure (A) and the right figure (B) in [Figure reference], the load conditions are the same, but the load is relatively heavy (i.e., heavy load). When coordinated control is not enabled in the left figure (A), the system runs continuously, but both Module Cell1 and Module Cell 2 operate simultaneously, and the output power of each module is relatively low (when the output voltages are equal, the output current of a single module during operation is relatively low). Therefore, the system efficiency is relatively low. After coordinated control is enabled in the right figure (B), the number of operating modules is optimized, that is, the two modules operate alternately. The power borne by a single module increases (when the output voltages are equal, the output current of a single module during operation is relatively high), and the system operating efficiency is improved.

[0101] Such as ​ It should be noted that the references like "In the left figure (A) and the right figure (B) in [Figure reference]..." and "In the left figure (A) and the right figure (B) in [Figure reference]..." in the translation assume that there should be a specific figure reference which is not provided in the original text. You may need to adjust it according to the actual situation.As shown, it shows the structure of the control device of the distributed power conversion system of the present invention to achieve distributed coordinated operation. Among them, the distributed power conversion system may include, for example, n power modules Cell 1 to Cell n, and the control device may include, for example, n control units 200 (for example, respectively integrated into n control chips), which are used to respectively control these power modules Cell 1 to Cell n, and the driving method of each power module can be independently implemented in the control chip of each power module. Each control unit 200 may include, for example, three units: a sequence number generation unit 201, a module optimal number calculation unit 202, and a comparison unit 203. The sequence number generation unit 201 compares and sorts the coordination amount of this module with the coordination amounts of other modules by receiving the communication coordination amount between modules, and can obtain the ranking of this module, and at the same time outputs it as its own module sequence number R (1 ≤ R ≤ N), that is, generates a first amount Q1 reflecting the respective module sequence numbers R. The module optimal number calculation unit 202 receives the amount reflecting its own efficiency and outputs the optimal operation number M of the module (1 ≤ M ≤ N), that is, generates a second amount Q2 reflecting the optimal operation number M of the module. The comparison unit 203 compares the first amount Q1 reflecting R and the second amount Q2 reflecting M. If Q1 > Q2, the corresponding module is cut out; if Q1 ≤ Q2, the corresponding module is put into operation. The above-mentioned communication coordination amount between modules can be information such as the series-side voltage, the operation time, the temperature, the current (input current, output current, inductor current, etc.), the power (input power, output power, etc.), the carrier wave (the amplitude is related to the ID number, and real-time communication is not required), etc.

[0102] Correspondingly, the present invention can provide a control device for a distributed power conversion system, which may include N control units for respectively controlling N power modules connected in parallel of the distributed power conversion system. Among them, each control unit may include: a sequence number generation unit for generating a first amount Q1 reflecting the respective module sequence numbers R according to a coordination amount; a module number calculation unit for generating a second amount Q2 reflecting the optimal operation number M of the module; and a comparison unit for comparing the first amount Q1 and the second amount Q2, wherein when the first amount Q1 is greater than the second amount Q2, the corresponding power module stops operating; when the first amount Q1 is less than or equal to the second amount Q2, the corresponding power module is put into operation.

[0103] In an embodiment of the present invention, the operation time of each power module within a carrier period is the same.

[0104] In one embodiment of the present invention, the sequence number generation unit of each control unit compares its respective coordination quantity with the coordination quantities of other power modules to obtain its respective ranking, and uses the ranking as its respective module sequence number. The coordination quantity can be one of the following information: voltage, operation time, temperature, current, power, and carrier wave. Wherein, the voltage can be the series-side voltage of the distributed power conversion system; the operation time can be the operation time when the power module is put into operation; the current can be the input current, output current, or inductor current of the distributed power conversion system; the power can be the input power or output power of the power module.

[0105] In one embodiment of the present invention, the coordination quantity can be, for example, a carrier wave. Wherein, the sequence number generation unit of each control unit can configure the carrier period and carrier peak value of the corresponding power module, where the carriers of adjacent power modules are phase-shifted by 2π / N, and the phase-shifting order of each power module is determined by the ID number of each power module; and the carrier amplitude of the corresponding power module is used as the coordination quantity for communication and compared with the carrier amplitudes of other power modules to obtain its respective ranking, and uses the ranking as its respective module sequence number, and generates a first quantity Q1 reflecting its respective module sequence number. The module quantity calculation unit of each control unit respectively generates a second quantity Q2 reflecting the optimal operation quantity of the module. The comparison unit of each control unit compares the second quantity Q2 with the first quantity Q1 to generate a corresponding drive signal to drive the corresponding power module to be put into operation or stopped.

[0106] In one embodiment of the present invention, the module quantity calculation unit can also be used to optimize the optimal operation quantity M of the modules put into operation, where: the module quantity calculation unit determines the optimal efficiency point power P corresponding to the best efficiency point of the N power modules opt ; the module quantity calculation unit multiplies the average output power P of the N power modules local by the total number N of power modules to obtain the total system power of the distributed power conversion system, and takes the integer part of the ratio of the total system power to the optimal efficiency point power P opt to obtain the operation calculation value M cal ; the module quantity calculation unit determines the optimal operation quantity M of the modules put into operation according to the principle that the operation power of a single module is closest to the optimal efficiency point, where M = M cal or M cal +1.

[0107] Wherein, the algorithm for the module quantity calculation unit to determine the optimal operation quantity M of the modules put into operation is as follows:

[0108]

[0109] Wherein, if Then M = M cal + 1; otherwise M = M cal .

[0110] In one embodiment of the present invention, each power module may include a first port, and the first ports of N power modules are connected in parallel.

[0111] In one embodiment of the present invention, each power module may be a first-level power module, which may have a first-level power conversion unit. Alternatively, each power module may be a second-level power module, which may have a cascaded first-level power conversion unit and a second-level power conversion unit. Wherein, when the power module is put into operation or stopped, the first-level power conversion unit or the second-level power conversion unit is put into or stopped, or the first-level power conversion unit and the second-level power conversion unit are put into or stopped simultaneously.

[0112] In one embodiment of the present invention, when a power module is selected to be put into operation, the power module put into operation is in the hiccup mode.

[0113] For a distributed power conversion system including N power modules connected in parallel, the control method of the present invention can coordinate the operation of the system through the coordination amount between the power modules, improve the system efficiency, reduce the output voltage and output current ripple, and achieve balanced operation between the modules. The control method of the present invention is simple and reliable. Compared with the existing solutions, it does not require a centralized controller, avoids the single-point failure problem of the centralized controller, and reduces the cost.

[0114] The present invention has a stronger dc-link voltage equalization regulation ability by switching all power modules in a certain order in turn, does not affect the power transmission characteristics of the converter, has a low communication rate requirement, and is applicable to a distributed power conversion system with multiple modules connected in parallel, such as including but not limited to data centers, charging stations, energy storage, and microgrids, etc.

[0115] The above specifically shows and describes the exemplary embodiments of the present invention. It should be understood that the present invention is not limited to the disclosed embodiments. On the contrary, the present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A control method for a distributed power conversion system, characterized in that The described distributed power conversion system includes N power modules connected in parallel, where N is a positive integer greater than 1. The control method includes: Configuring N control units to respectively control the N power modules, where each control unit is used to execute: Step S1: Generate a first quantity Q1 reflecting its respective module number R according to a coordination quantity. Wherein, each control unit compares its own coordination quantity with the coordination quantities of other power modules to obtain its own ranking, and uses the ranking as its own module number; Step S2: Generate a second quantity Q2 reflecting the optimal operation number M of the modules. Wherein, optimizing the optimal operation number M of the modules put into operation includes: determining the optimal efficiency point power Popt corresponding to the best efficiency point of the N power modules, and calculating the value of M according to the ratio of the total system power to the optimal efficiency point power Popt; Step S3: Compare the first quantity Q1 and the second quantity Q2, wherein, When the first quantity Q1 is greater than the second quantity Q2, the corresponding power module stops operating; When the first quantity Q1 is less than or equal to the second quantity Q2, the corresponding power module is put into operation.

2. The control method of the distributed power conversion system according to claim 1, wherein The first quantity Q1 = k * R, and the second quantity Q2 = k * M, where k is a positive number.

3. The control method of the distributed power conversion system according to claim 1, wherein, The operating time of each power module put into operation is the same within one carrier cycle.

4. The control method of the distributed power conversion system according to claim 1, characterized in that, The coordination quantity is one of the following information: voltage, operating time, temperature, current, power, and carrier.

5. The control method of the distributed power conversion system according to claim 4, wherein, The voltage is the series-side voltage of the distributed power conversion system; the operating time is the operating time of the power module put into operation; the current is the input current, output current, or inductor current of the distributed power conversion system; the power is the input power or output power of the power module.

6. The control method of the distributed power conversion system according to claim 4, characterized in that, The coordination quantity is a carrier, and step S1 includes: Step S11: Each control unit configures the carrier cycle and carrier peak value of the corresponding power module, where the carriers of adjacent power modules are phase-shifted by 2π / N, and the phase-shifting order of each power module is determined by the ID number of each power module; Step S12: Each control unit uses the carrier amplitude of the corresponding power module as the coordination quantity for communication and compares it with the carrier amplitudes of other power modules to obtain its own ranking, and uses the ranking as its own module number, and generates a first quantity Q1 reflecting its respective module number R; Moreover, in step S2, each control unit respectively generates a second quantity Q2 reflecting the optimal operation number M of the modules; Moreover, in step S3, each control unit compares the second quantity Q2 with the first quantity Q1 to generate a corresponding drive signal to drive the corresponding power module to be put into operation or stop operating.

7. The control method of the distributed power conversion system according to claim 1, characterized in that, Step S2 further includes: According to the average output power P of the N power modules local multiply by the total number N of power modules to obtain the total system power of the distributed power conversion system, and take the integer part of the ratio of the total system power to the power P at the optimal efficiency point opt to obtain the operation calculation value M cal ; Determine the optimal number of modules M = M to be put into operation according to the principle that the operating power of a single module is closest to the best efficiency point cal or M cal + 1 8. The control method of the distributed power conversion system according to claim 7, characterized in that, The algorithm for determining the optimal operation number M of the modules put into operation is as follows: Among them, if then M = M cal + 1; otherwise M = M cal .

9. The control method of the distributed power conversion system according to claim 1, wherein Each power module includes a first port, and the first ports of the N power modules are connected in parallel.

10. The control method of the distributed power conversion system according to claim 1, wherein Each power module is a first-level power module, which has a first-level power conversion unit.

11. The control method of the distributed power conversion system according to claim 1, characterized in that, Each of the power modules is a two - level power module, which has a cascaded first - level power conversion unit and a second - level power conversion unit. Among them, when the power module is put into operation or stopped, it is to put into or stop the first - level power conversion unit or the second - level power conversion unit, or to put into or stop the first - level power conversion unit and the second - level power conversion unit simultaneously.

12. The control method of the distributed power conversion system according to claim 1, wherein, When one of the power modules is selected to be put into operation, the power module in operation is in the hiccup mode.

13. A control device for a distributed power conversion system, characterized in that, The distributed power conversion system includes N power modules connected in parallel, where N is a positive integer greater than 1. The control device includes: N control units, respectively corresponding to controlling the N power modules. Each of the control units includes: A sequence number generation unit, which is used to generate a first quantity Q1 reflecting the respective module sequence number R according to a coordination quantity. Among them, the respective coordination quantity is compared with the coordination quantities of other power modules to obtain their respective rankings, and the rankings are used as their respective module sequence numbers. A module quantity calculation unit, which is used to generate a second quantity Q2 reflecting the optimal operation quantity M of the modules. Among them, optimizing the optimal operation quantity M of the modules put into operation includes: determining the optimal efficiency point power Popt corresponding to the best efficiency point of the N power modules, and calculating the value of M according to the ratio of the total system power to the optimal efficiency point power Popt. A comparison unit, which is used to compare the first quantity Q1 and the second quantity Q2. Among them, when the first quantity Q1 is greater than the second quantity Q2, the corresponding power module stops operating; when the first quantity Q1 is less than or equal to the second quantity Q2, the corresponding power module is put into operation.

14. The control device of the distributed power conversion system according to claim 13, wherein The first quantity Q1 = k * R, and the second quantity Q2 = k * M, where k is a positive number.

15. The control device of the distributed power conversion system according to claim 13, characterized in that, The operation time of each power module in one carrier period is the same.

16. The control device of the distributed power conversion system according to claim 13, characterized in that, The coordination quantity is one of the following information: voltage, operation time, temperature, current, power, and carrier.

17. The control device of the distributed power conversion system according to claim 16, wherein The voltage is the series - side voltage of the distributed power conversion system; the operation time is the operation time when the power module is put into operation; the current is the input current, output current, or inductor current of the distributed power conversion system; the power is the input power or output power of the power module.

18. The control device of the distributed power conversion system according to claim 16, characterized in that, The coordination quantity is the carrier, where: The sequence number generation unit of each control unit configures the carrier period and carrier peak value of the corresponding power module. The carriers of adjacent power modules are phase - shifted by 2π / N, and the phase - shift order of each power module is determined by the ID number of each power module; and the carrier amplitude of the corresponding power module is used as the coordination quantity for communication and compared with the carrier amplitudes of other power modules to obtain their respective rankings, and the rankings are used as their respective module sequence numbers, and a first quantity Q1 reflecting their respective module sequence numbers R is generated. The module quantity calculation unit of each control unit respectively generates a second quantity Q2 reflecting the optimal operation quantity M of the modules. The comparison unit of each of the control units compares the second quantity Q2 with the first quantity Q1 to generate a corresponding drive signal to drive the corresponding power module to operate or stop operating.

19. The control device of the distributed power conversion system according to claim 13, characterized in that, Where: The module quantity calculation unit multiplies the average output power P of the N power modules local by the total number N of power modules to obtain the total system power of the distributed power conversion system, and calculates and rounds the ratio of the total system power to the power P at the optimal efficiency point opt to obtain the operation calculation value M cal ; The module quantity calculation unit determines the optimal operation quantity M of the modules put into operation according to the principle that the operation power of a single module is closest to the best efficiency point, where M = M cal or M cal + 1.

20. The control device of the distributed power conversion system according to claim 19, characterized in that, The algorithm for the module quantity calculation unit to determine the optimal operating quantity M of the modules put into operation is as follows: Among them, if then M = M cal + 1; otherwise M = M cal .

21. The control device of the distributed power conversion system according to claim 13, characterized in that, Each of the power modules includes a first port, and the first ports of the N power modules are connected in parallel.

22. The control device of the distributed power conversion system according to claim 13, characterized in that, Each of the power modules is a first-level power module, which has a first-level power conversion unit.

23. The control device of the distributed power conversion system according to claim 13, characterized in that, Each of the power modules is a second-level power module, which has a cascaded first-level power conversion unit and a second-level power conversion unit. Wherein, when the power module operates or stops operating, it turns on or off the first-level power conversion unit or the second-level power conversion unit, or turns on or off the first-level power conversion unit and the second-level power conversion unit simultaneously.

24. The control device of the distributed power conversion system according to claim 13, characterized in that, When one of the power modules is selected to operate, the power module put into operation is in the hiccup mode.

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