Control device and control method of power conversion system

Abstract

The present invention provides a control device and control method for a power conversion system. The power conversion system includes N power modules connected in parallel, where N is a positive integer greater than 1. The control method includes: step S1, configuring the carrier period of the power module and configuring the carrier phase shift of adjacent power modules by 2π / N; step S2, selecting M power modules to be put into operation within the carrier period, 0≤M≤N, and providing a modulated wave to the power modules, wherein the amplitude of the modulated wave is A / N of the carrier peak value of the carrier. When the power conversion system is in a steady state, A=M; when not in a steady state, M and A are the same after rounding; step S3, respectively comparing the amplitude of the modulated wave with the amplitude of the carrier of each power module. When the amplitude of the modulated wave is greater than the amplitude of the carrier, the corresponding power module is put into operation; when the amplitude of the modulated wave is less than or equal to the amplitude of the carrier, the corresponding power module stops operating. The present invention has a stronger DC-link voltage equalization regulation capability and low communication rate requirements.

Description

Technical Field

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

[0002] With the advancement of distributed renewable energy generation technology and the increasing number of DC power devices, the demand for DC power distribution is increasing, such as high-power energy storage power conditioning systems (PCS), electric vehicle ultra-fast charging stations, rail transportation, medium-voltage power electronic transformer (MV-PET) systems, etc. Due to the power limitation of a single module, it is usually necessary to use multiple modules in parallel (at least one port in parallel) to achieve low voltage and high current applications on the DC side, such as Figures 1A to 1C As shown, the structures of parallel combination systems such as solid-state transformer (SST), input series output parallel (ISOP) DC / DC converter, and input parallel output parallel (IPOP) DC / DC converter are respectively shown.

[0003] In order to reduce switching losses, improve efficiency and reduce gain, DC / DC converters are usually operated in burst mode at light load, such as LLC resonant converters. Figure 1D If the D2D modules are controlled in an isolated and decentralized manner without coordination, when all DC / DC converters start and stop simultaneously under light load, the output voltage ripple will be large, requiring a larger output capacitor.

[0004] Since the inherent losses such as switching loss, driving loss, and conduction loss account for a large proportion at light load, the efficiency of the isolated resonant DC / DC converter is low at light load, such as Figure 1E Currently, most modular parallel converters use a power-sharing mode, where all modules share the system power equally, regardless of whether they are operating at full power. This results in low power operation for each module under light load conditions, leading to lower efficiency. Therefore, reducing system losses under light load conditions will improve overall system efficiency.

[0005] The existing technology for input series output parallel (ISOP) systems has one or more problems: failure to ensure input voltage balance, high communication rate requirements, failure to ensure equal operation time of all converters, and failure to avoid inconsistent converter aging. Summary of the Invention

[0006] An object of the present invention is to provide a control device and a control method for a power conversion system, which can solve one or more defects of the prior art.

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

[0008] Step S1, configuring the carrier period of the N power modules, and configuring the carrier phase shift of any adjacent power modules to be 2π / N;

[0009] Step S2: within the carrier period, select M power modules to be put into operation, where 0≤M≤N, and provide a modulated wave to the N power modules, wherein the amplitude of the modulated wave is A / N of the carrier peak value of the carrier, wherein when the power conversion system is in a steady state, A=M, and when the power conversion system is not in a steady state, M and A are equal after rounding;

[0010] Step S3, respectively compare the amplitude of the modulated wave with the amplitude of the carrier of each of the power modules, wherein when the amplitude of the modulated wave is greater than the amplitude of the carrier, the corresponding power module is put into operation; when the amplitude of the modulated wave is less than or equal to the amplitude of the carrier, the corresponding power module stops running.

[0011] In one embodiment of the present invention, the time when each power module is put into operation is the same within a carrier cycle.

[0012] In one embodiment of the present invention, in step S2, the method for selecting the number M of power modules put into operation includes:

[0013] Determine the optimal efficiency point power P corresponding to the optimal efficiency point of the power module opt ;

[0014] According to the total system power P of the power conversion system o With the best efficiency point power P opt The ratio of the calculated value is rounded to get the running calculation value M cal ;

[0015] According to the principle that the operating power of a single power module is closest to the optimal efficiency point, the number of power modules put into operation is determined as M=M cal or M cal +1.

[0016] In one embodiment of the present invention, the algorithm for determining the number M of power modules put into operation is as follows:

[0017]

[0018] Among them, if Then M=M cal +1; otherwise M=M cal .

[0019] In one embodiment of the present invention, each of the power modules includes a first port, wherein the first ports of the N power modules are connected in parallel.

[0020] In one embodiment of the present invention, each of the power modules is a one-stage power module having a one-stage power conversion unit.

[0021] In one embodiment of the present invention, each of the power modules is a two-stage power module, which has a cascaded first-stage power conversion unit and a second-stage power conversion unit, wherein when the power module is put into operation or stopped, the first-stage power conversion unit or the second-stage power conversion unit is put into operation or stopped, or the first-stage power conversion unit and the second-stage power conversion unit are put into operation or stopped at the same time.

[0022] In one embodiment of the present invention, when one of the power modules is selected to be put into operation, the power module that is put into operation is in a hiccup mode.

[0023] In one embodiment of the present invention, the control method is implemented by a centralized controller, wherein the centralized controller is used to generate N carriers with a phase shift of 2π / N according to the total number N of current power modules, and is used to calculate the number M of power modules put into operation and generate the modulation wave, and is used to compare the modulation wave with the carrier respectively to generate a corresponding drive signal and send it to each corresponding power module.

[0024] In one embodiment of the present invention, the control method is implemented by a plurality of control chips respectively distributed on each of the power modules, wherein each of the control chips is used to generate N carriers with a phase shift of 2π / N according to the ID number of the current power module, the inter-module synchronization signal, and the total number N of the current power modules, and is used to obtain the number M of power modules that need to be put into operation and generate the modulation wave through local calculation or communication, and is used to compare the modulation wave with the carrier to generate a corresponding drive signal.

[0025] According to another embodiment of the present invention, the present invention further provides a control device for a power conversion system, wherein the power conversion system includes N power modules connected in parallel, where N is a positive integer greater than 1, wherein the control device includes at least one control unit for controlling the N power modules, wherein the at least one control unit includes:

[0026] A carrier generating unit, configured to generate N carriers, wherein the carriers of any adjacent power modules are phase-shifted by 2π / N;

[0027] a module quantity selection unit, configured to select M of the power modules for operation within a carrier cycle of the N power modules, where 0≤M≤N, and provide a modulated wave to the N power modules, wherein the amplitude of the modulated wave is A / N of the carrier peak value of the carrier, wherein when the power conversion system is in a steady state, A=M, and when the power conversion system is not in a steady state, M and A are equal after rounding;

[0028] A comparison unit is used to compare the amplitude of the modulated wave with the amplitude of the carrier of the power module, wherein when the amplitude of the modulated wave is greater than the amplitude of the carrier, the corresponding power module is put into operation; when the amplitude of the modulated wave is less than or equal to the amplitude of the carrier, the corresponding power module stops running.

[0029] In another embodiment of the present invention, the time when each power module is put into operation is the same within a carrier cycle.

[0030] In another embodiment of the present invention, the module quantity selection unit is configured to determine the best efficiency point power P corresponding to the best efficiency point of the power module. opt According to the total system power P of the power conversion system o With the best efficiency point power P opt The ratio of the running calculation value M is calculated cal ; and according to the principle that the operating power of a single power module is closest to the optimal efficiency point, the number of power modules put into operation is determined to be M = M cal or M cal +1.

[0031] In another embodiment of the present invention, the algorithm used by the module quantity selection unit to determine the number M of power modules put into operation is as follows:

[0032]

[0033] Among them, if Then M=M cal +1; otherwise M=M cal .

[0034] In another embodiment of the present invention, each of the power modules comprises a first port, wherein the first ports of the N power modules are connected in parallel.

[0035] In another embodiment of the present invention, each of the power modules is a one-stage power module having a one-stage power conversion unit.

[0036] In another embodiment of the present invention, each of the power modules is a two-stage power module, which has a cascaded first-stage power conversion unit and a second-stage power conversion unit, wherein the power module puts the first-stage power conversion unit or the second-stage power conversion unit into operation or stops operation, or puts the first-stage power conversion unit and the second-stage power conversion unit into operation or stops operation at the same time.

[0037] In another embodiment of the present invention, the power module that is put into operation is in a hiccup mode.

[0038] In another embodiment of the present invention, the at least one control unit is configured as a centralized controller, wherein the centralized controller generates N carriers with a phase shift of 2π / N according to the total number N of current power modules through the carrier generation unit, calculates the number M of power modules put into operation and generates the modulation wave through the module quantity calculation unit, and compares the modulation wave with the carrier through the comparison unit to generate a corresponding drive signal and send it to each corresponding power module.

[0039] In another embodiment of the present invention, the at least one control unit is configured to include a plurality of control chips respectively distributed on each of the power modules, wherein each of the control chips generates N carriers with a phase shift of 2π / N according to the ID number of the current power module, the inter-module synchronization signal, and the total number N of the current power modules through the carrier generation unit, and obtains the number M of power modules that need to be put into operation and generates the modulation wave through local calculation or communication through the module quantity calculation unit, and compares the modulation wave with the carrier through the comparison unit to generate a corresponding drive signal.

[0040] For a power conversion system consisting of N power modules connected in parallel, the control method of the present invention improves system efficiency and reduces output voltage and current ripple by rotating and coordinating the operation of the modules. Compared with existing solutions, the control method of the present invention is simpler and more reliable, requires lower communication speeds, and does not affect system control performance such as voltage and current balancing.

[0041] The present invention determines the active module by comparing the modulated wave with the carrier wave. All power modules are switched on and off in a specific order, providing enhanced DC-link voltage balancing and regulation capabilities without affecting the converter's power transmission characteristics. This invention is suitable for power conversion systems with multiple modules connected in parallel, including but not limited to data centers, charging stations, energy storage systems, and microgrids.

[0042] Additional aspects and advantages of the 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 invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the accompanying drawings.

[0044] The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the accompanying drawings.

[0045] Figure 1A 、 Figure 1B and Figure 1C They are the structural schematic diagrams of the parallel combination systems of SST, ISOP D2D, IPOP D2D, etc. in the prior art;

[0046] Figure 1D A schematic diagram of an operating state of a conventional isolated resonant DC / DC converter in a burst mode at light load;

[0047] Figure 1E Schematic diagram of the efficiency of an existing isolated resonant DC / DC converter;

[0048] Figure 2 Schematic diagram of a control method for a power conversion system of the present invention;

[0049] Figure 3A 、 Figure 3B and Figure 3C They are schematic diagrams of technical effects of the coordinated control method of the power conversion system of the present invention in different operating states at different system load powers;

[0050] Figure 3D Schematic diagram of a method for controlling coordinated operation of N power modules according to the present invention;

[0051] Figure 4A and Figure 4B They are schematic diagrams of the module switching levels of the two-stage converter when switching in turn according to the present invention, wherein Figure 4A For the first level switching, Figure 4B It is a secondary switching;

[0052] Figure 5 This is a schematic diagram of a simulation model in which two modules are connected in series with input and in parallel with output as an example for simulation;

[0053] Figure 6 for Figure 5 The simulation model shown is a schematic diagram of simulation results when using module uncoordinated control (A) and module coordinated control (B) at light load;

[0054] Figure 7 for Figure 5The simulation model shown is a schematic diagram of simulation results when using module uncoordinated control (A) and module coordinated control (B) under heavy load;

[0055] Figure 8 This is a schematic diagram of the structure of the power conversion system control device of the present invention using a centralized controller to achieve centralized coordinated operation;

[0056] Figure 9 This is a structural diagram of a power conversion system control device of the present invention using multiple control chips to achieve distributed coordinated operation. DETAILED DESCRIPTION

[0057] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be embodied in many 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 concepts of the example embodiments to those skilled in the art. Like reference numerals in the figures represent like or similar structures, and thus their detailed description will be omitted.

[0058] When introducing the elements / components / etc. described and / or illustrated herein, the terms "a," "an," "the," "said," and "at least one" are used to indicate that there are one or more elements / components / etc. The terms "comprising," "including," and "having" are used to indicate an open-ended inclusiveness and mean that additional elements / components / etc. may be present in addition to the listed elements / components / etc. Relative terms may be used in the embodiments, such as "upper" or "lower" to describe the relative relationship of one component of the illustration to another component. It is understood that if the device of the illustration is turned over so that it is 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 used only as labels and are not numerical limitations on their objects.

[0059] The present invention provides a control method for a power conversion system, wherein the 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. 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, an SST, an ISOP, an IPOP, and other systems. In the present invention, Figure 2 As shown, the control method includes:

[0060] Step S1: configure the carrier period of N power modules and configure the carrier phase shift of any adjacent power modules to be 2π / N;

[0061] Step S2: within a carrier cycle, select M power modules to be put into operation, where 0≤M≤N, and provide a modulated wave to the N power modules. The amplitude of the modulated wave is A / N of the carrier peak value of the carrier, where A=M when the power conversion system is in a steady state, and M is equal to A after rounding when the power conversion system is not in a steady state;

[0062] Step S3: Compare the amplitude of the modulated wave with the amplitude of the carrier of each power module respectively. When the amplitude of the modulated wave is greater than the amplitude of the carrier, the corresponding power module is put into operation; when the amplitude of the modulated wave is less than or equal to the amplitude of the carrier, the corresponding power module stops running.

[0063] In the present invention, the time for each power module to be put into operation can be the same within a carrier cycle. In addition, when a module is selected to be put into operation, the power module put into operation is, for example, in a hiccup mode.

[0064] like Figure 3A 、 Figure 3B and Figure 3C As shown, it shows the technical effects of the coordinated control method of the present invention in different operating states at different system load powers. Take four D2D modules with a rated power of 15kW in parallel as an example to illustrate, assuming that a single module below 3kW enters the hiccup mode. Figure 3A As shown, if the load power is 10kW, when decentralized control is in operation, that is, the coordinated control method is not enabled, all power modules enter the hiccup mode operation state, and each module starts and stops at the same time, resulting in large output voltage ripple. Figure 3B As shown in the figure, if the coordinated control method is enabled, the modules are operated alternately, and only two modules are enabled at any time, and each module bears 5kW of power, then all power modules will not enter the hiccup mode, the total power of the entire system will be continuous, and the output voltage ripple will be reduced. Figure 3C As shown in the figure, when the load power is 2.5kW, the load power is less than the power required for a single module to enter the burst mode. At this time, only one module is enabled to operate alternately at the same time. By alternating, the total system power is discontinuous, but the fluctuating power is reduced to 1 / 4. Under the same output filter capacitance, the voltage ripple is reduced to 1 / 4. Different patterns in the figure represent different power modules, and the same vertical axis represents power modules operating simultaneously. This shows that the present invention operates through coordinated control, and the number of modules in operation also decreases as the power decreases, so the system can always operate in a high efficiency range.

[0065] The coordinated operation control method of the power conversion system of the present invention is described in detail below. Figure 3DAs shown, first, the carrier period T_carrier is selected, the carrier peak value is configured to be N (N is the total number of power modules), and the phase shift between the carriers of adjacent power modules is 2π / N, for example Figure 3D The waveform includes 4 power modules, namely Cell1 to Cell4. The solid lines in the first 4 waveforms represent the carriers of the corresponding cells. The adjacent power modules can be arbitrarily adjacent. For example, the power modules can be arbitrarily numbered. The adjacent power modules refer to the power modules with adjacent numbers. Then, M (1≤M≤N) modules are selected for operation. The amplitude of the modulation wave is M. For example, Figure 3D In the illustrated embodiment, two power modules are selected for operation during the first carrier cycle T_carrier, and one power module is selected for operation during the next carrier cycle T_carrier. The dashed lines in the first four waveforms represent the modulation wave. When the modulation wave is greater than the carrier wave, the corresponding module is put into operation (i.e., switched on); when the modulation wave is less than the carrier wave, the corresponding module is deactivated (i.e., switched off). Figure 3D When the enable signal of each cell is 1, the corresponding module is switched on; when the enable signal is 0, the corresponding module is switched off. This method automatically rotates modules using carrier phase shifting, and the rotation period can be flexibly configured based on the carrier period. This method also requires low communication rates and can be implemented with both centralized and distributed controllers. Module rotation also prevents inconsistent aging across modules. For ISOP systems, high-speed switching ensures DC-link voltage balancing.

[0066] In one embodiment of the present invention, each power module may be a first-stage power module, which may have a first-stage power conversion unit. In other embodiments, each power module may also be a second-stage power module, which may have a cascaded first-stage power conversion unit and a second-stage power conversion unit. Moreover, when the power module is put into operation or stopped, it puts the first-stage power conversion unit or the second-stage power conversion unit into operation or stops the operation, or puts the first-stage power conversion unit and the second-stage power conversion unit into operation or stops the operation at the same time. For example, Figure 4A and Figure 4B As shown, for a two-stage converter, the alternate switching can be only one of the stages, for example Figure 4A Only the second-level D2D units of each module Cell 1 to Cell n are switched, or two-level switching is possible, for example Figure 4B The first-stage A2D units and the second-stage D2D units of each module Cell 1 to Cell n are switched on and off simultaneously.

[0067] In the present invention, in order to optimize system efficiency and reduce output voltage ripple, the number M of modules put into operation can also be optimized. In other words, in step S2, the method for selecting the number M of power modules put into operation may include, for example: first, determining the best efficiency point power P corresponding to the best efficiency point of the power module opt Secondly, according to the total system power P of the power conversion system o With the best efficiency point power P opt The ratio of the calculated value is rounded to get the running calculation value M cal Then, the number of power modules put into operation is determined based on the principle that the operating power of a single power module is closest to the optimal efficiency point. cal or M cal +1.

[0068] The algorithm for determining the number M of power modules put into operation is as follows:

[0069]

[0070] Among them, if Then M=M cal +1; otherwise M=M cal .

[0071] Take 15kW*4 modules as an example, assuming the optimal efficiency point is P opt =7.5kW, the best efficiency range is 5kW-10kW. Assume that the power to enter Burst mode is P burst =3kW. The above optimization algorithm calculates the number of operations corresponding to the corresponding total power range, as shown in Table 1. As the power decreases, the number of operations is reduced to ensure that each module operates near its optimal efficiency point above 10kW. Furthermore, after adopting the coordinated control method of the present invention, the power limit for the system to enter Burst mode drops from 12kW to 3kW.

[0072] Total power range Number of runs Single module power range system 25.7kW~60kW 4 at the same time 6.43kW~15kW System continuous operation 18kW~25.7kW 3 rotations 6kW~8.57kW System continuous operation 10kW~18kW 2 take turns 5kW~9kW System continuous operation 3kW~10kW 1 rotation 3kW~10kW System continuous operation 0kW~3kW 1 rotation 0kW~3kW Burst Mode

[0073] Table 1 Example of optimization of the number of runs

[0074] Take the two modules Cell 1 and Cell 2 with inputs connected in series and outputs connected in parallel as an example for simulation. The simulation model is as follows: Figure 5 The simulation results are shown in Figure 6 and Figure 7 As shown, PWM_en is the switching signal of module Cell1 and module Cell2, 1 is switching on, 0 is switching off; V dc is the input voltage of the two modules, i o is the output current of the two modules, V o is the output voltage, fs is the converter control variable. Figure 6 The load conditions in the left figure (A) and the right figure (B) are the same, but the load is lighter (i.e., light load). When coordinated control is not enabled in the left figure (A), both modules Cell 1 and Cell 2 are put into operation. Each module bears less power (when the output voltage is equal, the output current of a single module is lower when it is running). The module is in Burst mode, and the output voltage V o The ripple is large; in the right figure (B), after the coordinated control is enabled, the two modules Cell 1 and Cell 2 operate alternately, and the power borne by a single module increases (when the output voltage is equal, the output current of a single module is higher), and the operating state of the system changes from Burst mode to continuous operation. The output voltage V o Ripple reduction. Figure 7 The load conditions in the left and right figures (A) and (B) are identical, but the load is heavier (i.e., heavy load). In the left figure (A), without coordinated control, the system operates continuously, but both modules, Cell 1 and Cell 2, operate simultaneously. Each module's output power is low (when the output voltages are equal, the output current is lower when a single module is operating), resulting in low system efficiency. In the right figure (B), with coordinated control enabled, the number of operating modules is optimized, with the two modules operating alternately. This increases the power borne by each module (when the output voltages are equal, the output current is higher when a single module is operating), improving system efficiency.

[0075] like Figure 8 As shown, it shows the structure of the control device of the power conversion system of the present invention to achieve centralized coordinated operation. Wherein, the power conversion system may include N power modules Cell 1 to Cell N, and the control device may include a control unit 200, for example, configured as a centralized controller for centrally controlling these power modules Cell 1 to Celln. Wherein, the driving square wave of each module is generated in the centralized controller. The centralized controller may, for example, generate N phase-shifted 2π / N carriers according to the total number N of current power modules through the carrier generation unit 201, and calculate the number M of power modules put into operation and generate a modulation wave through the module quantity calculation unit 202, and compare the modulation wave with the carrier through the comparison unit 203 to generate a corresponding driving signal (PWM_en) and send it to the corresponding power modules Cell 1 to Cell N.

[0076] like Figure 9As shown, it shows the structure of the control device of the power conversion system of the present invention to achieve distributed coordinated operation. Among them, the power conversion system may include N power modules Cell 1 to Cell N, and the control device may include N control units 200, for example, configured to include multiple control chips distributed on each power module. Among them, each control chip generates N phase-shifted 2π / N carriers according to the ID number of the current power module, the inter-module synchronization signal Sync, and the total number N of current power modules through the carrier generation unit 201, and obtains the number M of power modules that need to be put into operation and generates a modulation wave through local calculation or communication through the module quantity calculation unit 202, and compares the modulation wave with the carrier through the comparison unit 203 to generate a corresponding drive signal (PWM_en). The inter-module synchronization signal Sync can be obtained through communication.

[0077] Accordingly, the present invention can provide a control device for a power conversion system, which may include at least one control unit for controlling N power modules. The at least one control unit may include: a carrier generation unit for generating N carriers, wherein the carriers of any adjacent power modules are phase-shifted by 2π / N; a module quantity selection unit for selecting M power modules for operation within the carrier period of the N power modules, wherein 0≤M≤N, and providing a modulated wave to the N power modules, wherein the amplitude of the modulated wave is A / N of the carrier peak value of the carrier, wherein when the power conversion system is in a steady state, A=M, and when the power conversion system is not in a steady state, M and A are equal after rounding; a comparison unit for comparing the amplitude of the modulated wave with the amplitude of the carrier of the power module, wherein when the amplitude of the modulated wave is greater than the amplitude of the carrier, the corresponding power module is put into operation; when the amplitude of the modulated wave is less than or equal to the amplitude of the carrier, the corresponding power module stops operating.

[0078] In one embodiment of the present invention, the time when each power module is put into operation is the same within one carrier cycle.

[0079] In one embodiment of the present invention, the module quantity selection unit is configured to determine the best efficiency point power P corresponding to the best efficiency point of the power module. opt ; According to the total system power P of the power conversion system o and the best efficiency point power P opt The ratio of the running calculation value M is calculated cal ; and according to the principle that the operating power of a single power module is closest to the optimal efficiency point, the number of power modules put into operation is determined to be M = M cal or M cal +1.

[0080] In one embodiment of the present invention, the algorithm used by the module quantity selection unit to determine the number M of power modules put into operation is as follows:

[0081]

[0082] Among them, if Then M=M cal +1; otherwise M=M cal .

[0083] In one embodiment of the present invention, each power module includes a first port, wherein the first ports of N power modules are connected in parallel.

[0084] In one embodiment of the present invention, each power module is a one-stage power module having a one-stage power conversion unit.

[0085] In one embodiment of the present invention, each power module is a two-stage power module, which has a cascaded first-stage power conversion unit and a second-stage power conversion unit, wherein when the power module is put into operation or stopped, the first-stage power conversion unit or the second-stage power conversion unit is put into operation or stopped, or the first-stage power conversion unit and the second-stage power conversion unit are put into operation or stopped at the same time.

[0086] In one embodiment of the present invention, when a power module is selected to be put into operation, the power module that is put into operation is in a hiccup mode.

[0087] In one embodiment of the present invention, at least one control unit is configured as a centralized controller, wherein the centralized controller generates N carrier waves with a phase shift of 2π / N according to the total number N of current power modules through a carrier generation unit, calculates the number M of power modules put into operation and generates a modulation wave through a module quantity calculation unit, and compares the modulation wave with the carrier wave through a comparison unit to generate a corresponding drive signal and send it to each corresponding power module.

[0088] In one embodiment of the present invention, at least one control unit is configured to include a plurality of control chips respectively distributed on each power module, wherein each control chip generates N carrier waves with a phase shift of 2π / N according to the ID number of the current power module, the inter-module synchronization signal, and the total number N of the current power modules through a carrier generation unit, and obtains the number M of power modules that need to be put into operation and generates a modulation wave through a module quantity calculation unit through local calculation or through communication, and compares the modulation wave with the carrier wave through a comparison unit to generate a corresponding drive signal.

[0089] For a power conversion system consisting of N power modules connected in parallel, the control method of the present invention improves system efficiency and reduces output voltage and current ripple by rotating and coordinating the operation of the modules. Compared with existing solutions, the control method of the present invention is simpler and more reliable, requires lower communication speeds, and does not affect system control performance such as voltage and current balancing.

[0090] The present invention determines the active module by comparing the modulated wave with the carrier wave. All power modules are switched on and off in a specific order, providing enhanced DC-link voltage balancing and regulation capabilities without affecting the converter's power transmission characteristics. This invention is suitable for power conversion systems with multiple modules connected in parallel, including but not limited to data centers, charging stations, energy storage systems, and microgrids.

[0091] While exemplary embodiments of the present invention have been particularly shown and described above, it should be understood that the present invention is not limited to the disclosed embodiments, but rather is intended to cover various modifications and equivalent arrangements encompassed within the spirit and scope of the appended claims.

Claims

1. A control method for a power conversion system, wherein the power conversion system comprises N power modules connected in parallel, wherein N is a positive integer greater than 1, characterized in that: The control method includes: Step S1, configuring the carrier period of the N power modules, and configuring the carrier phase shift of any adjacent power modules to be 2π / N; Step S2: within the carrier period, select M power modules to be put into operation, where 0≤M≤N, and provide a modulated wave to the N power modules, wherein the amplitude of the modulated wave is A / N of the carrier peak value of the carrier, wherein when the power conversion system is in a steady state, A=M, and when the power conversion system is not in a steady state, M and A are equal after rounding; Step S3: Compare the amplitude of the modulated wave with the amplitude of the carrier of each power module, wherein: When the amplitude of the modulated wave is greater than the amplitude of the carrier wave, the corresponding power module is put into operation; When the amplitude of the modulated wave is less than or equal to the amplitude of the carrier wave, the corresponding power module stops running.

2. The control method of the power conversion system according to claim 1, characterized in that: The time when each power module is put into operation is the same within a carrier cycle.

3. The control method of the power conversion system according to claim 1, wherein: In step S2, the method for selecting the number M of power modules put into operation includes: Determine the optimal efficiency point power P corresponding to the optimal efficiency point of the power module opt ; According to the total system power P of the power conversion system o With the best efficiency point power P opt The ratio of the calculated value is rounded to get the running calculation value M cal ; According to the principle that the operating power of a single power module is closest to the optimal efficiency point, the number of power modules put into operation is determined as M = M cal or M cal +1.

4. The control method of the power conversion system according to claim 3, characterized in that: The algorithm for determining the number M of power modules put into operation is as follows: ； Among them, if , then M = M cal +1; otherwise M = M cal .

5. The control method of the power conversion system according to claim 1, characterized in that: Each of the power modules includes a first port, wherein the first ports of the N power modules are connected in parallel.

6. The control method of the power conversion system according to claim 1, characterized in that: Each of the power modules is a one-stage power module having a one-stage power conversion unit.

7. The control method of the power conversion system according to claim 1, characterized in that: Each of the power modules is a two-stage power module, which has a cascaded first-stage power conversion unit and a second-stage power conversion unit, wherein when the power module is put into operation or stopped, the first-stage power conversion unit or the second-stage power conversion unit is put into operation or stopped, or the first-stage power conversion unit and the second-stage power conversion unit are put into operation or stopped at the same time.

8. The control method of the power conversion system according to claim 1, characterized in that: When one of the power modules is selected to be put into operation, the power module that is put into operation is in a hiccup mode.

9. The control method of a power conversion system according to any one of claims 1 to 8, characterized in that: The control method is implemented through a centralized controller, wherein the centralized controller is used to generate N carriers with a phase shift of 2π / N according to the total number N of current power modules, and is used to calculate the number M of power modules put into operation and generate the modulation wave, and is used to compare the modulation wave with the carrier respectively to generate a corresponding drive signal and send it to each corresponding power module.

10. The control method of a power conversion system according to any one of claims 1 to 8, characterized in that: The control method is implemented by multiple control chips distributed on each of the power modules, wherein each control chip is used to generate N carriers with a phase shift of 2π / N based on the ID number of the current power module, the inter-module synchronization signal, and the total number N of the current power modules, and is used to obtain the number M of power modules that need to be put into operation and generate the modulation wave through local calculation or communication, and is used to compare the modulation wave with the carrier to generate a corresponding drive signal.

11. A control device for a power conversion system, the power conversion system comprising N power modules connected in parallel, wherein N is a positive integer greater than 1, characterized in that: The control device includes at least one control unit for controlling the N power modules, wherein the at least one control unit includes: A carrier generating unit, configured to generate N carriers, wherein the carriers of any adjacent power modules are phase-shifted by 2π / N; a module quantity selection unit, configured to select M of the power modules for operation within a carrier cycle of the N power modules, where 0≤M≤N, and provide a modulated wave to the N power modules, wherein the amplitude of the modulated wave is A / N of the carrier peak value of the carrier, wherein when the power conversion system is in a steady state, A=M, and when the power conversion system is not in a steady state, M and A are equal after rounding; A comparison unit is used to compare the amplitude of the modulated wave with the amplitude of the carrier of the power module, wherein when the amplitude of the modulated wave is greater than the amplitude of the carrier, the corresponding power module is put into operation; when the amplitude of the modulated wave is less than or equal to the amplitude of the carrier, the corresponding power module stops running.

12. The control device of the power conversion system according to claim 11, characterized in that: The time when each power module is put into operation is the same within a carrier cycle.

13. The control device of the power conversion system according to claim 11, characterized in that: The module quantity selection unit is configured to determine the optimal efficiency point power P corresponding to the optimal efficiency point of the power module. opt According to the total system power P of the power conversion system o With the best efficiency point power P opt The ratio of the running calculation value M is calculated cal ; And according to the principle that the operating power of a single power module is closest to the optimal efficiency point, the number of power modules put into operation is determined as M = M cal or M cal +1.

14. The control device of the power conversion system according to claim 13, characterized in that: The algorithm used by the module quantity selection unit to determine the number M of power modules put into operation is as follows: ； Among them, if , then M = M cal +1; otherwise M = M cal .

15. The control device of the power conversion system according to claim 11, characterized in that: Each of the power modules includes a first port, wherein the first ports of the N power modules are connected in parallel.

16. The control device of the power conversion system according to claim 11, characterized in that: Each of the power modules is a one-stage power module having a one-stage power conversion unit.

17. The control device of the power conversion system according to claim 11, characterized in that: Each of the power modules is a two-stage power module, which has a cascaded first-stage power conversion unit and a second-stage power conversion unit, wherein when the power module is put into operation or stopped, the first-stage power conversion unit or the second-stage power conversion unit is put into operation or stopped, or the first-stage power conversion unit and the second-stage power conversion unit are put into operation or stopped at the same time.

18. The control device of the power conversion system according to claim 11, characterized in that: When one of the power modules is selected to be put into operation, the power module that is put into operation is in a hiccup mode.

19. The control device for a power conversion system according to any one of claims 11 to 18, wherein: The at least one control unit is configured as a centralized controller, wherein the centralized controller generates N carrier waves with a phase shift of 2π / N according to the total number N of current power modules through the carrier wave generating unit, calculates the number M of power modules put into operation and generates the modulated wave through the module quantity calculating unit, and compares the modulated wave with the carrier waves through the comparing unit to generate corresponding driving signals and send them to the corresponding power modules.

20. The control device for a power conversion system according to any one of claims 11 to 18, wherein: The at least one control unit is configured to include a plurality of control chips respectively distributed on each of the power modules, wherein each of the control chips generates N carriers with a phase shift of 2π / N according to the ID number of the current power module, the inter-module synchronization signal, and the total number N of the current power modules through the carrier generation unit, and obtains the number M of power modules that need to be put into operation and generates the modulation wave through local calculation or communication through the module quantity calculation unit, and compares the modulation wave with the carrier through the comparison unit to generate a corresponding driving signal.

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