Control method of cascade system and cascade system

Abstract

The invention provides a cascade system control method and a cascade system, the cascade system comprises a first port and N power modules, N is an integer greater than or equal to 2, each power module comprises a first port and a second port, and the first ports of the N power modules are connected in series and then connected with the first port of the cascade system. And the voltage of the first port of at least one power module is controlled, n1 and n2 are adjacent integers between the voltage corresponding to the n1th level and the voltage corresponding to the n2th level within part of time of a switching period, so that the cascade system works in a current interruption mode, the inductance current interruption is realized, and a given value is followed without a static error, and thus the power supply efficiency is improved. A light load control solution of the cascade system is provided, the turn-on current of the power module under the light load is reduced, zero-current turn-on is realized, and the light load efficiency is improved.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a control method for a cascaded system and a cascaded system. Background Technology

[0002] Solid-state transformers employing modular cascaded systems have broad application prospects in data centers, electric vehicle charging and swapping stations, photovoltaics, and energy storage. However, as... Figure 1 As shown, the efficiency of solid-state transformer power supply systems is relatively low under light loads. Therefore, researching methods to improve the efficiency of modular cascaded systems under light loads is of great significance for promoting the application of solid-state transformers.

[0003] In existing technologies, Burst mode is used under light load conditions, controlling the converter's switching state based on the output voltage to improve efficiency. However, this method typically suffers from poor current waveform and is generally used for standby or very light load conditions (e.g., <5% load). Furthermore, depending on whether the inductor current in the cascaded system is continuous, the converter can be divided into three operating modes: Continuous Conduction Mode (CCM), Critical Conduction Mode (CRM), and Discontinuous Conduction Mode (DCM). Figure 2 As shown, using DCM mode control under light load can reduce the switching frequency, and the switching transistor can achieve zero-current turn-on, with no reverse recovery loss in the diode, thereby improving efficiency. However, this method of improving efficiency is only applicable to single modules; the light-load efficiency problem of modular cascaded systems has not yet been solved. Summary of the Invention

[0004] This application provides a control method and a cascaded system for a cascaded system, which provides a solution to improve the efficiency of the cascaded system under light loads to overcome the deficiencies in the prior art.

[0005] In a first aspect, this application provides a control method for a cascaded system, the cascaded system comprising a first port and N power modules, where N is an integer greater than or equal to 2, each power module comprising a first port and a second port, the first ports of the N power modules being connected in series to the first port of the cascaded system; the control method comprising:

[0006] The voltage at the first port of at least one power module is controlled to be between the voltage corresponding to the n1th level and the voltage corresponding to the n2th level for a portion of a switching cycle, such that the cascaded system operates in a current discontinuous conduction mode, where n1 and n2 are adjacent integers.

[0007] In one possible design, the cascaded system further includes an inductor, the first port of the cascaded system being connected to a voltage source via the inductor, wherein the voltage at the first port of the control of at least one power module, during a portion of a switching cycle, lies between the voltage corresponding to the n1th level and the voltage corresponding to the n2th level, including:

[0008] The carrier signals corresponding to the N power modules are sequentially phase-shifted by 2π / N;

[0009] Based on the inductance of the inductor, the equivalent switching frequency of the system, the current setpoint of the first port of the cascaded system, the voltage setpoint of the first port of the cascaded system, the voltage of the second port of the power module, and N, the first duty cycle and the second duty cycle are calculated based on the cascaded system operating in discontinuous current conduction mode.

[0010] The drive signal for the switch in each power module is determined based on the first duty cycle, the second duty cycle, and the carrier signal of each power module.

[0011] In one possible design, the voltage setpoint of the first port of the cascaded system is equal to the voltage of the voltage source.

[0012] One possible design also includes:

[0013] The current error is obtained based on the current setpoint and current feedback value of the first port of the cascaded system, and the current error is modulated to obtain an intermediate voltage; and

[0014] The voltage of the cascaded system is obtained by subtracting the intermediate voltage from the voltage of the voltage source.

[0015] One possible design also includes:

[0016] Based on the voltage setpoint of the first port and the voltage of the second port of the power module, and assuming the cascaded system operates in continuous current conduction mode, a third duty cycle and a fourth duty cycle are calculated; and

[0017] The drive signal for the switch in each power module is determined based on the minimum value of the first duty cycle and the third duty cycle, the minimum value of the second duty cycle and the fourth duty cycle, and the carrier signal of each power module.

[0018] In one possible design, the cascaded system further includes an inductor, the first port of the cascaded system being connected to a voltage source via the inductor, wherein the voltage at the first port of the control of at least one power module, during a portion of a switching cycle, lies between the voltage corresponding to the n1th level and the voltage corresponding to the n2th level, including:

[0019] The number of high-frequency power modules is determined to be 1 or 2 based on the voltage of the voltage source. The high-frequency power module refers to a power module in high-frequency modulation mode.

[0020] In one possible design, determining the number of high-frequency power modules based on the voltage of the voltage source includes:

[0021] If the ratio of the voltage of the voltage source to the voltage of the second terminal of the power module N times is less than a preset ratio, the number of the high-frequency power modules is determined to be 1.

[0022] If the ratio of the voltage of the voltage source to N times the voltage of the second terminal of the power module is greater than or equal to the preset ratio, the number of the high-frequency power modules is determined to be 2.

[0023] In one possible design, the preset ratio is 0.2.

[0024] In one possible design, when the number of the high-frequency power modules is 2, it further includes:

[0025] If the input voltage of the high-frequency power module is an integer multiple of the output voltage, the high-frequency power module is synchronously controlled; and

[0026] If the input voltage of the high-frequency power module is not an integer multiple of the output voltage, the high-frequency power module is controlled asynchronously.

[0027] In one possible design, the asynchronous control includes one of the following scenarios: simultaneously turning on the high-frequency power modules and not simultaneously turning them off; not simultaneously turning on the high-frequency power modules and simultaneously turning them off; or not simultaneously turning on the high-frequency power modules and not simultaneously turning them off.

[0028] In one possible design, the high-frequency power module can be determined by N power modules rotating in a timed or ordered manner.

[0029] Secondly, this application provides a cascaded system, comprising: a first port and N power modules, where N is an integer greater than or equal to 2, each power module including a first port and a second port, the first ports of the N power modules being connected in series to the first port of the cascaded system; and

[0030] A control unit is configured to control the voltage at the first port of at least one power module, which, for a portion of a switching cycle, is between the voltage corresponding to the n1th level and the voltage corresponding to the n2th level, such that the cascaded system operates in a discontinuous current mode, where n1 and n2 are adjacent integers.

[0031] In one possible design, the cascaded system further includes an inductor, and the first port of the cascaded system is connected to a voltage source via the inductor. The control unit is specifically used for:

[0032] The carrier signals corresponding to the N power modules are sequentially phase-shifted by 2π / N;

[0033] Based on the inductance of the inductor, the equivalent switching frequency of the system, the current setpoint of the first port of the cascaded system, the voltage setpoint of the first port of the cascaded system, the voltage of the second port of the power module, and N, the first duty cycle and the second duty cycle are calculated based on the cascaded system operating in discontinuous current conduction mode.

[0034] The drive signal for the switch in each power module is determined based on the first duty cycle, the second duty cycle, and the carrier signal of each power module.

[0035] In one possible design, the voltage setpoint of the first port of the cascaded system is equal to the voltage of the voltage source.

[0036] In one possible design, the control unit is further configured to:

[0037] The current error is obtained based on the current setpoint and current feedback value of the first port of the cascaded system, and the current error is modulated to obtain an intermediate voltage; and

[0038] The voltage of the cascaded system is obtained by subtracting the intermediate voltage from the voltage of the voltage source.

[0039] In one possible design, the control unit is further configured to:

[0040] Based on the voltage setpoint of the first port and the voltage of the second port of the power module, and assuming the cascaded system operates in continuous current conduction mode, a third duty cycle and a fourth duty cycle are calculated; and

[0041] The drive signal for the switch in each power module is determined based on the minimum value of the first duty cycle and the third duty cycle, the minimum value of the second duty cycle and the fourth duty cycle, and the carrier signal of each power module.

[0042] In one possible design, the cascaded system further includes an inductor, the first port of the cascaded system being connected to a voltage source via the inductor, and the control unit is further configured to:

[0043] The number of high-frequency power modules is determined to be 1 or 2 based on the voltage of the voltage source. The high-frequency power module refers to a power module in high-frequency modulation mode.

[0044] In one possible design, the control unit is further configured to:

[0045] If the ratio of the voltage of the voltage source to the voltage of the second terminal of the power module N times is less than a preset ratio, the number of the high-frequency power modules is determined to be 1.

[0046] If the ratio of the voltage of the voltage source to N times the voltage of the second terminal of the power module is greater than or equal to the preset ratio, the number of the high-frequency power modules is determined to be 2.

[0047] In one possible design, the preset ratio is 0.2.

[0048] In one possible design, when the number of the high-frequency power modules is two, the control unit is further configured to:

[0049] If the input voltage of the high-frequency power module is an integer multiple of the output voltage, the high-frequency power module is synchronously controlled; and

[0050] If the input voltage of the high-frequency power module is not an integer multiple of the output voltage, the high-frequency power module is controlled asynchronously.

[0051] In one possible design, the asynchronous control includes one of the following scenarios: simultaneously turning on the high-frequency power modules and not simultaneously turning them off; not simultaneously turning on the high-frequency power modules and simultaneously turning them off; or not simultaneously turning on the high-frequency power modules and not simultaneously turning them off.

[0052] In one possible design, the high-frequency power module can be determined by N power modules rotating in a timed or ordered manner.

[0053] This application provides a control method and a cascaded system for a cascaded system. The cascaded system includes a first port and N power modules, where N is an integer greater than or equal to 2. Each power module includes a first port and a second port. The first ports of the N power modules are connected in series to the first port of the cascaded system. The voltage of the first port of at least one power module is controlled to be between the voltage corresponding to the n1-th level and the voltage corresponding to the n2-th level during a portion of a switching cycle, where n1 and n2 are adjacent integers. This allows the cascaded system to operate in a discontinuous current mode, achieving discontinuous inductor current with no steady-state error following the given value. This provides a light-load control solution for the cascaded system, reducing the turn-on current of the power modules under light load, achieving zero-current turn-on, and improving light-load efficiency. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 A schematic diagram illustrating the efficiency of a solid-state transformer power supply system in the prior art;

[0056] Figure 2 This is a schematic diagram of the inductor current waveform under different control modes provided in the prior art;

[0057] Figure 3 A schematic diagram of a cascaded system provided in an embodiment of this application;

[0058] Figure 4 A simulation effect diagram provided for an embodiment of this application;

[0059] Figure 5 A control block diagram provided for an embodiment of this application;

[0060] Figure 6 A schematic diagram illustrating a carrier phase shift-based DCM implementation provided in this application embodiment;

[0061] Figure 7 Another control block diagram provided for embodiments of this application;

[0062] Figure 8 This is another simulation effect diagram provided for an embodiment of this application;

[0063] Figure 9 This is another simulation effect diagram provided for an embodiment of the present application;

[0064] Figure 10 A schematic diagram of asynchronous DCM control between power modules provided in an embodiment of this application;

[0065] Figure 11 Different scenarios of asynchronous control provided in the embodiments of this application;

[0066] Figure 12 This is a schematic diagram of another cascaded system provided in an embodiment of this application;

[0067] Figure 13 A schematic diagram illustrating the calculation process of duty cycle and switching frequency provided for an embodiment of this application;

[0068] Figure 14 A block diagram illustrating how to determine an error based on average current, as provided in an embodiment of this application;

[0069] Figure 15 A schematic diagram illustrating the operation effect of a cascaded system under quadrilateral DCM control, provided in an embodiment of this application;

[0070] Figure 16 This is a schematic diagram of another cascaded system provided in an embodiment of this application. Detailed Implementation

[0071] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application. Rather, they are merely examples of methods and apparatus consistent with some aspects of this application as detailed in the appended claims.

[0072] The terms “first,” “second,” “third,” “fourth,” etc. (if present) in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the application described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms “comprising” and “having,” and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0073] In existing technologies, Burst mode is used under light load conditions, controlling the converter's switching state based on the output voltage to improve efficiency. However, this method typically suffers from poor current waveform and is generally used for standby or very light load (e.g., <5% load) applications. Furthermore, depending on whether the inductor current in the cascaded system is continuous, the converter can be divided into three operating modes: CCM, CRM, and DCM. Figure 2 As shown, using DCM mode control under light load can reduce the switching frequency, and the switching transistor can achieve zero-current turn-on, with no reverse recovery loss in the diode, thereby improving efficiency. However, this method of improving efficiency is only applicable to single modules; the light-load efficiency problem of modular cascaded systems has not yet been solved.

[0074] To address the aforementioned problems in the prior art, this application provides a control method and a cascaded system for a cascaded system. The inventive concept of the control method for the cascaded system provided in this application is as follows: the cascaded system may include a first port and N power modules, where N is an integer greater than or equal to 2. Each power module includes a first port and a second port. The first ports of the N power modules are connected in series to the first port of the cascaded system. By controlling the voltage of the first port of at least one power module, within a portion of a switching cycle, between the voltage corresponding to the n1-th level and the voltage corresponding to the n2-th level, where n1 and n2 are adjacent integers, the cascaded system operates in a discontinuous current mode. This enables discontinuous inductor current with no steady-state error following the given value, providing a light-load control solution for the cascaded system. This reduces the turn-on current of the power modules under light loads, achieving zero-current turn-on and improving light-load efficiency.

[0075] Figure 3 This is a schematic diagram of a cascaded system provided in an embodiment of this application. Figure 3 As shown, the cascaded system includes a first port and N power modules, where N can be an integer greater than or equal to 2. Each power module includes a first port and a second port. The first ports of the N power modules are connected in series to the first port of the cascaded system.

[0076] By controlling the voltage at the first port of at least one of the N power modules, within a portion of a switching cycle, between the voltage corresponding to the n1-th level and the voltage corresponding to the n2-th level, the cascaded system can be made to operate in a discontinuous current conduction mode. Here, n1 and n2 are consecutive integers. The n1-th and n2-th levels are module levels.

[0077] For example, a two-level module has two output voltage levels: 0 and 1. A three-level module has three output voltage levels: -1, 0, and 1. A five-level module has five output voltage levels: -2, -1, 0, 1, and 2. And so on. Assuming the output level is n, for different topologies of the cascaded system, the output voltage is n multiplied by (Vdc / m). The same number of DC capacitors connected in series form m sets of output voltages. The value of m varies in different multi-level circuits. Vdc is the voltage at the second port of each power module. Figure 3 Vg is the voltage at the first port of the cascaded system, which is also the input voltage.

[0078] As described above, by controlling the turn-on and turn-off times of each switch in each power module and the timing between each power module, the rise, fall, and discontinuity times of the grid-side current in the cascaded system can be controlled. This enables the inductor current to be discontinuous and to follow the given value without steady-state error, allowing the cascaded system to operate in discontinuous current mode. This provides a light-load control solution for cascaded systems, which can reduce the turn-on current of power modules under light load, achieve zero-current turn-on, and improve light-load efficiency.

[0079] In one possible design, light load can refer to less than 20% of the load. In actual working conditions, the corresponding range of light load can also be set according to the actual situation, and this application embodiment does not limit this.

[0080] Figure 4 This is a simulation effect diagram provided for an embodiment of this application. The simulation experiment uses a cascaded system consisting of three power modules as an example. Specifically, the number of cascaded modules N=3. By controlling the total bridge arm voltage of the three power modules to be between 2Vo and 3Vo for a period of time after the current drops to zero, ensuring it is neither a 2Vo nor a 3Vo level, discontinuous inductor current is achieved under light load. Here, Vo represents the output voltage of the power module, i.e., Vdc. Furthermore, Figure 4 In this context, Ig, Igref, and Vbsum represent the current value (i.e., the inductor current value), the current setpoint, and the port voltage after the first ports of N power modules are connected in series, respectively.

[0081] In one possible design, the voltage at the first port of at least one power module in the cascaded system can be controlled by carrier phase shifting to be between the voltages corresponding to the n1 and n2 levels for a portion of a switching cycle.

[0082] Specifically, refer to Figure 5 As shown, the carrier signals corresponding to the N power modules can be phase-shifted by 2π / N sequentially, and then the inductance (e.g., Figure 3 The L shown fThe inductance of the cascaded system and the equivalent switching frequency T. eq The current setpoint I at the first port of the cascaded system ref The voltage setpoint V at the first port of the cascaded system bref The voltages Vo and N at the second port of the power module are calculated based on the cascaded system operating in discontinuous current conduction mode to generate a first duty cycle d1 and a second duty cycle d2. Then, based on the first duty cycle d1, the second duty cycle d2, and the carrier signal of each power module, the drive signal of the switch in each power module is determined. Based on the drive signal, the voltage at the first port of the corresponding power module is controlled accordingly to achieve discontinuous inductor current.

[0083] In one possible design, calculations are performed based on the cascaded system operating in discontinuous current conduction mode, i.e., through... Figure 5 The possible implementations of the DCM calculation of the first and second duty cycles shown can be achieved through the following formulas (1), (2), (5) to (8):

[0084]

[0085]

[0086] Formula 1 is used to calculate the current rise time T. eqr Formula (2) is used to calculate the current fall time T. eqf , where V gx According to V g -nV o Calculated.

[0087] Wherein, the voltage setpoint V at the first port gx It can be obtained through the following formulas (3) and (4):

[0088]

[0089] V gx =V g -nV o (4)

[0090] As shown in formula (3), based on the current reference value I at the first port of the cascaded system... ref The current error is obtained from the current feedback value at the first port of the cascaded system. The intermediate voltage nV is obtained by modulating the current error. o Referring to formula (4), the voltage V of the voltage source g Subtract the intermediate voltage to get V gx .

[0091] The current rise time T calculated by combining formulas (1) and (2) eqrand current fall time T eqf Furthermore, the conduction times of the upper and lower tubes in the cascaded system are calculated using the following formulas (5) and (6):

[0092] T0=(Nn-1)T eq +T eqr (5)

[0093] T1 = nT eq +T eqf (6)

[0094] Where T0 and T1 represent the conduction time of the upper tube such as S11 and the conduction time of the lower tube such as S12, respectively.

[0095] Furthermore, based on the conduction time, the first duty cycle d1 and the second duty cycle d2 are generated using formulas (7) and (8):

[0096] d1=T0 / T sw (7)

[0097] d2=(T0+T1) / T sw (8)

[0098] Among them, T sw Indicates the switching cycle.

[0099] Combination Figure 5 As shown, after generating the first duty cycle d1 and the second duty cycle d2, the drive signal for the switch in each power module is determined based on the first duty cycle, the second duty cycle, and the carrier signal of each power module. For example, when the carrier signal is less than the first duty cycle d1, S... i1 When the carrier signal is between the first duty cycle d1 and the second duty cycle d2, S is turned on. i2 When the carrier signal is greater than the second duty cycle d2, S is turned on. i1 and S i2 All drives are disabled. Therefore, for a portion of a switching cycle, the drive of the i-th power module is disabled, controlling the first port voltage of the i-th power module to be between 0 and V. o This allows for discontinuous inductor current. Figure 6 This is a schematic diagram of a carrier phase shift-based DCM implementation provided in an embodiment of this application.

[0100] Optionally, the voltage setpoint at the first port of the cascaded system can be equal to the voltage of the voltage source, for example, as... Figure 3 Vg in the text.

[0101] In some embodiments, the control method for the cascaded system provided in this application can also achieve seamless switching between CCM mode and DCM mode. (See also...) Figure 7As shown, the voltage value V at the first port can be used as a reference. bref The voltage Vo at the second port of the power module is calculated based on the cascaded system operating in continuous current conduction mode. Figure 7 The CCM calculation shown in the figure obtains the third duty cycle c1 and the fourth duty cycle c2. Further, based on the minimum value cmp1 of the first duty cycle d1 and the third duty cycle c1, the minimum value cmp2 of the second duty cycle d2 and the fourth duty cycle c2, and the carrier signal of each power module, the drive signal of the switch in each power module is determined. Based on the drive signal, the voltage of the first port of the corresponding power module is controlled accordingly to realize the discontinuous inductor current.

[0102] The embodiments of this application do not limit the possible implementation of CCM calculation, which can be any implementation in the related art.

[0103] contrast Figure 6 and Figure 7 It can be seen that, in Figure 6 In the DCM mode shown, closed-loop control can be performed, or Vbref can be directly set to Vg. Figure 7 The CCM mode shown requires a closed-loop control component. When using closed-loop control... Figure 6 In the DCM calculation formula shown in the embodiment, the Vg part needs to be replaced with V. bref . Figure 7 The flowchart for automatic switching between CCM and DCM modes in the document. Figure 7 Compared to Figure 6 The full-range DCM mode shown can achieve automatic switching, resulting in better control.

[0104] Figure 8 Another simulation effect diagram provided for an embodiment of this application, such as Figure 8 and Figure 9 As shown, under lighter loads, such as Figure 8 As shown, controlling the first port voltage of at least one power module to be between two adjacent voltage levels, such as 2Vo and 3Vo in the figure, results in discontinuous inductor current, enabling zero-current switching, reducing switching losses, and improving light-load efficiency. Figure 9 As shown, the DCM mode time varies under different loads. Under heavy load, CCM mode is the main mode, under light load, CCM mode is partially used, and under very light load, DCM mode is used completely. Through automatic switching between CCM mode and DCM mode, the inductor current can follow the current setpoint without steady-state error under different loads.

[0105] In some embodiments, the light-load control of the cascaded system based on carrier phase shift described above has the advantages of simple implementation and is beneficial for distributed control. This control method is applicable to both centralized and distributed control. For example, the closed-loop control algorithm and DCM calculation formula described above can be implemented in both centralized controllers and modular controllers, and this application does not limit the implementation of such implementation.

[0106] In one possible design, such as Figure 3 The cascaded system shown includes a first port and N power modules, where N is an integer greater than or equal to 2. Each power module includes a first port and a second port. The first ports of the N power modules are connected in series to the first port of the cascaded system. The cascaded system also includes an inductor, and the first port of the cascaded system is connected to a voltage level through the inductor. A quadrilateral DCM control can be used to ensure that the voltage at the first port of at least one power module in the cascaded system is between the voltages corresponding to the n1th and n2th levels for a portion of a switching cycle.

[0107] For example, the number of high-frequency power modules can be determined as 1 or 2 based on the voltage of the voltage source of the cascaded system. This means controlling one or two power modules in the cascaded system to be in high-frequency modulation mode, thus achieving light-load control of the cascaded system. Here, a high-frequency power module refers to a power module in high-frequency modulation mode.

[0108] Specifically, the number of high-frequency power modules (1 or 2) can be determined based on the voltage of the voltage source. For example, if the ratio of the voltage of the voltage source to the voltage at the second terminal of N times the power module is less than a preset ratio, such as... Then the number of high-frequency power modules is determined to be 1, and the remaining power modules remain at zero level; if the ratio of the voltage of the voltage source to the voltage at the second terminal of N times the power module is greater than or equal to a preset ratio, such as... The number of high-frequency power modules is determined to be 2, and the remaining power modules maintain a zero-level or 1-level state according to the voltage relationship. In some embodiments, the preset ratio can be 0.2.

[0109] Furthermore, when the number of high-frequency power modules is two, if the input voltage (e.g., Vg) of the high-frequency power module is an integer multiple of the output voltage (e.g., Vo), then the two high-frequency power modules are controlled synchronously; however, if the input voltage (e.g., Vg) of the high-frequency power module is not an integer multiple of the output voltage (e.g., Vo), then... Figure 10 The two high-frequency power modules are controlled asynchronously as shown.

[0110] In one possible design, the asynchronous control of the high-frequency power module can include methods such as... Figure 11 The following are some examples:

[0111] For example, asynchronous control may include, Figure 11 As shown in (a), the high-frequency power modules are turned on simultaneously but not simultaneously turned off, such as... Figure 11 As shown in (b), the high-frequency power modules are not simultaneously turned on but simultaneously turned off, or as shown in (b). Figure 11 The scenario shown in (c) involves either the simultaneous activation or simultaneous deactivation of the high-frequency power modules. Figure 11 Cell 1 and Cell 2 in the diagram represent two high-frequency power modules.

[0112] In one possible design, such as Figure 12 In the cascaded system shown, after determining the number of high-frequency power modules, the high-frequency power modules can be determined by rotating N power modules in a timed or sequential manner. It should be noted that... Figure 12 The example shown uses three power modules; this is not a limitation on the number of power modules.

[0113] Specifically, for example, a counter can be used for timed rotation. First, the counter reading is initialized to 0. After calculating the duty cycle of each power module, the counter can determine which group of power modules is currently designated as high-frequency power modules. For example, if the counter reading is less than the number of power modules, the power modules in the first group are identified as high-frequency power modules. If the counter reading is greater than the number of power modules but less than twice the number of power modules, the power modules in the second group are identified as high-frequency power modules. If the counter reading is greater than twice the number of power modules but less than three times the number of power modules, the power modules in the third group are identified as high-frequency power modules. If the counter reading is greater than three times the number of power modules, the counter is reset to zero, and the duty cycle of each segment is recalculated.

[0114] The sorting and rotation method can be implemented, for example, after calculating the duty cycle of each power module, by sorting the output voltages of each power module in the cascaded system, selecting the power module with the higher output voltage to keep at 0 level (i.e., bypass), and selecting the power module with the lower output voltage to keep at 1 level, and then allocating the duty cycles for each power module. The criteria for determining "high" and "low" output voltage can be achieved by setting corresponding voltage thresholds; for example, voltages above the threshold are considered "high" output voltages, and voltages below or equal to the threshold are considered "low" output voltages.

[0115] In some embodiments, the calculation of the duty cycle and switching frequency of each power module in the light-load asynchronous control of a cascaded system implemented by quadrilateral DCM control is as follows: Figure 13 As shown. Please also refer to... Figure 10 and Figure 13 . Figure 13 A schematic diagram illustrating the calculation process of duty cycle and switching frequency provided in this application embodiment is shown below. Figure 13As shown, the embodiments of this application include:

[0116] S101: Preset ripple current.

[0117] Among them, I rip For ripple current, I′ ref I is the average current reference value. xset The ripple parameter setting value can be preset using the following formula (9):

[0118] I rip =2(I ref +I xset (9)

[0119] S102: Sample inductor currents I1 and I2, and calculate the average current I using the equal area method. mean .

[0120] Referring to formulas (10) to (13), where T1 is the time it takes for the inductor current to rise to I1, which is also the time it takes for the second power module to turn on, T2 is the time it takes for the inductor current to rise from I1 to I2, and the sum of T1 and T2 is the time it takes for the first power module to turn on. f T is the time it takes for the inductor current to drop from I2 to 0. off T is the time when the inductor current is 0. sw For the switching period, V g V is the input voltage. o For output voltage,

[0121]

[0122]

[0123]

[0124]

[0125] S103: Average current I obtained through calculation mean Tracking average current reference value I ref The error err is obtained.

[0126] like Figure 14 As shown, based on the calculated average current I mean Tracking average current reference value I ref The error err is obtained, where K p This is the proportionality coefficient.

[0127] S104: Calculate the switching frequency and the duty cycle of each power module.

[0128] For example, if the turn-on time of power module 1 is set to be a times the turn-on time of power module 2, the turn-on time T1 of power module 1 can be obtained according to formula (14):

[0129]

[0130] The sum of the duty cycles of power module 1 and power module 2 is d. sumset The following formula (15):

[0131]

[0132] Introducing the error err obtained from S103, we have the following formula (16):

[0133] d sum =d sumset +err (16)

[0134] Thus, the duty cycle d of power module 1 can be calculated. 1′ The duty cycle d of power module 2 2′ and switching frequency f s The following formulas (17) to (20) are shown:

[0135]

[0136]

[0137]

[0138]

[0139] S105: Modulate the two high-frequency modulation modules according to their respective duty cycles.

[0140] For example, power module S i1 After being turned on for a period of time, it is turned off, and the power S i2 After continuing conduction for a period of time, the circuit is blocked, with both the upper and lower tubes blocked at point T. off During the time period, the port voltage of the control power module is between two levels.

[0141] As can be seen from the above embodiments, the quadrilateral DCM control enables the cascaded system to operate in DCM mode, and the operating effect is as follows: Figure 15 As shown, it can realize light-load control of cascaded systems, reduce switching frequency, and some switches can achieve zero-current turn-on or zero-current turn-off, thereby reducing switching losses and improving light-load efficiency.

[0142] In one possible design, the control method for the cascaded system provided in this application embodiment can support various cascaded system structures, such as DC / DC cascaded systems, like... Figure 16 The Boost cascade system and AC / DC cascade system shown in (a) are as follows: Figure 16 The Boost PFC cascade system in (b) is described in this application. The specific structure of the cascade system is not limited in this embodiment. Figure 16 Cell 1, cell 2, and cell 3 in the diagram represent power modules.

[0143] The cascading system provided in this application embodiment also includes:

[0144] The control unit is configured to implement the control method of the cascaded system provided in the above embodiments, for example, controlling the voltage of the first port of at least one power module between the voltage corresponding to the n1 level and the voltage corresponding to the n2 level for a portion of a switching cycle, so that the cascaded system operates in a current discontinuous mode, where n1 and n2 are adjacent integers.

[0145] In one possible design, the cascaded system also includes an inductor, with the first port of the cascaded system connected to a voltage source and control unit via the inductor, specifically for:

[0146] The carrier signals corresponding to the N power modules are shifted sequentially by 2π / N.

[0147] Based on the inductance of the inductor, the equivalent switching frequency of the system, the current setpoint of the first port of the cascaded system, the voltage setpoint of the first port of the cascaded system, the voltage of the second port of the power module, and N, the first duty cycle and the second duty cycle are calculated based on the cascaded system operating in discontinuous current conduction mode.

[0148] The drive signal for the switch in each power module is determined based on the first duty cycle, the second duty cycle, and the carrier signal of each power module.

[0149] In one possible design, the voltage setpoint at the first port of the cascaded system is equal to the voltage of the voltage source.

[0150] In one possible design, the control unit is also used for:

[0151] The current error is obtained based on the current setpoint and current feedback value at the first port of the cascaded system. The intermediate voltage is then obtained by modulating the current error.

[0152] The voltage setpoint of the first port of the cascaded system is obtained by subtracting the intermediate voltage from the voltage source voltage.

[0153] In one possible design, the control unit is also used for:

[0154] Based on the voltage setpoint of the first port and the voltage of the second port of the power module, the third duty cycle and the fourth duty cycle are calculated based on the cascaded system operating in continuous current conduction mode; and the drive signal of the switch in each power module is determined based on the minimum value of the first duty cycle and the third duty cycle, the minimum value of the second duty cycle and the fourth duty cycle, and the carrier signal of each power module.

[0155] In one possible design, the cascaded system also includes an inductor, with the first port of the cascaded system connected to a voltage source via the inductor. The control unit is also used for:

[0156] The number of high-frequency power modules is determined by the voltage of the voltage source, which is either 1 or 2. A high-frequency power module refers to a power module in high-frequency modulation mode.

[0157] In one possible design, the control unit is also used for:

[0158] If the ratio of the voltage of the voltage source to the voltage at the second terminal of N times the power module is less than the preset ratio, the number of high-frequency power modules is determined to be 1.

[0159] If the ratio of the voltage of the voltage source to the voltage at the second terminal of N times the power module is greater than or equal to a preset ratio, the number of high-frequency power modules is determined to be 2.

[0160] In one possible design, the preset ratio is 0.2.

[0161] In one possible design, when the number of high-frequency power modules is two, the control unit is also used for:

[0162] If the input voltage of the high-frequency power module is an integer multiple of the output voltage, the high-frequency power module is synchronously controlled; and

[0163] If the input voltage of the high-frequency power module is not an integer multiple of the output voltage, the high-frequency power module is controlled asynchronously.

[0164] In one possible design, asynchronous control includes one of the following scenarios: simultaneously turning on the high-frequency power modules and not simultaneously turning them off; not simultaneously turning on the high-frequency power modules and simultaneously turning them off; or not simultaneously turning on the high-frequency power modules and not simultaneously turning them off.

[0165] In one possible design, the high-frequency power module can be determined by N power modules rotating in a timed or sequential manner.

[0166] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the claims.

[0167] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A control method for a cascaded system, characterized in that, The cascaded system includes a first port and N power modules, where N is an integer greater than or equal to 2. Each power module includes a first port and a second port. The first ports of the N power modules are connected in series to the first port of the cascaded system. The control method includes: The voltage at the first port of at least one power module is controlled to be between the voltage corresponding to the n1th level and the voltage corresponding to the n2th level for a portion of a switching cycle, such that the cascaded system operates in a current discontinuous conduction mode, where n1 and n2 are adjacent integers.

2. The control method according to claim 1, characterized in that, The cascaded system further includes an inductor, and the first port of the cascaded system is connected to a voltage source through the inductor. The voltage at the first port of the control of at least one power module is between the voltage corresponding to the n1th level and the voltage corresponding to the n2th level for a portion of a switching cycle, including: The carrier signals corresponding to the N power modules are sequentially phase-shifted by 2π / N; Based on the inductance of the inductor, the equivalent switching frequency of the system, the current setpoint of the first port of the cascaded system, the voltage setpoint of the first port of the cascaded system, the voltage of the second port of the power module, and N, the first duty cycle and the second duty cycle are calculated based on the cascaded system operating in discontinuous current conduction mode. The drive signal for the switch in each power module is determined based on the first duty cycle, the second duty cycle, and the carrier signal of each power module.

3. The control method according to claim 2, characterized in that, The voltage setpoint of the first port of the cascaded system is equal to the voltage of the voltage source.

4. The control method according to claim 2, characterized in that, Also includes: The current error is obtained based on the current setpoint of the first port of the cascaded system and the current feedback value of the first port of the cascaded system, and the current error is modulated to obtain the intermediate voltage. as well as The voltage of the cascaded system is obtained by subtracting the intermediate voltage from the voltage of the voltage source.

5. The control method according to claim 4, characterized in that, Also includes: Based on the voltage setpoint of the first port and the voltage of the second port of the power module, the third duty cycle and the fourth duty cycle are calculated based on the cascaded system operating in continuous current conduction mode. as well as The drive signal for the switch in each power module is determined based on the minimum value of the first duty cycle and the third duty cycle, the minimum value of the second duty cycle and the fourth duty cycle, and the carrier signal of each power module.

6. The control method according to claim 1, characterized in that, The cascaded system further includes an inductor, and the first port of the cascaded system is connected to a voltage source through the inductor. The voltage at the first port of the control of at least one power module is between the voltage corresponding to the n1th level and the voltage corresponding to the n2th level for a portion of a switching cycle, including: The number of high-frequency power modules is determined to be 1 or 2 based on the voltage of the voltage source. The high-frequency power module refers to a power module in high-frequency modulation mode.

7. The control method according to claim 6, characterized in that, The step of determining the number of high-frequency power modules based on the voltage of the voltage source includes: If the ratio of the voltage of the voltage source to the voltage of the second terminal of the power module N times is less than a preset ratio, the number of the high-frequency power modules is determined to be 1. If the ratio of the voltage of the voltage source to the voltage of the second terminal of the power module being N times greater than or equal to the preset ratio, the number of the high-frequency power modules is determined to be 2.

8. The control method according to claim 7, characterized in that, The preset ratio is 0.

2.

9. The control method according to claim 6, characterized in that, When the number of the high-frequency power modules is 2, it also includes: If the input voltage of the high-frequency power module is an integer multiple of the output voltage, the high-frequency power module is synchronously controlled; and If the input voltage of the high-frequency power module is not an integer multiple of the output voltage, the high-frequency power module is controlled asynchronously.

10. The control method according to claim 9, characterized in that, The asynchronous control includes one of the following scenarios: simultaneously turning on the high-frequency power modules and not simultaneously turning them off; not simultaneously turning on the high-frequency power modules and simultaneously turning them off; or not simultaneously turning on the high-frequency power modules and not simultaneously turning them off.

11. The control method according to claim 6, characterized in that, The high-frequency power module can be determined by N power modules rotating in a timed or ordered manner.

12. A cascaded system, characterized in that, include: The system consists of a first port and N power modules, where N is an integer greater than or equal to 2. Each power module includes a first port and a second port. The first ports of the N power modules are connected in series to the first port of the cascaded system. as well as A control unit is configured to control the voltage at the first port of at least one power module, which, for a portion of a switching cycle, is between the voltage corresponding to the n1th level and the voltage corresponding to the n2th level, such that the cascaded system operates in a discontinuous current mode, where n1 and n2 are adjacent integers.

13. The cascade system according to claim 12, characterized in that, The cascaded system further includes an inductor, and the first port of the cascaded system is connected to a voltage source through the inductor. The control unit is specifically used for: The carrier signals corresponding to the N power modules are sequentially phase-shifted by 2π / N; Based on the inductance of the inductor, the equivalent switching frequency of the system, the current setpoint of the first port of the cascaded system, the voltage setpoint of the first port of the cascaded system, the voltage of the second port of the power module, and N, the first duty cycle and the second duty cycle are calculated based on the cascaded system operating in discontinuous current conduction mode. The drive signal for the switch in each power module is determined based on the first duty cycle, the second duty cycle, and the carrier signal of each power module.

14. The cascade system according to claim 13, characterized in that, The voltage setpoint of the first port of the cascaded system is equal to the voltage of the voltage source.

15. The cascaded system according to claim 13, characterized in that, The control unit is also used for: The current error is obtained based on the current setpoint of the first port of the cascaded system and the current feedback value of the first port of the cascaded system, and the current error is modulated to obtain the intermediate voltage. as well as The voltage of the cascaded system is obtained by subtracting the intermediate voltage from the voltage of the voltage source.

16. The cascaded system according to claim 15, characterized in that, The control unit is also used for: Based on the voltage setpoint of the first port and the voltage of the second port of the power module, the third duty cycle and the fourth duty cycle are calculated based on the cascaded system operating in continuous current conduction mode. as well as The drive signal for the switch in each power module is determined based on the minimum value of the first duty cycle and the third duty cycle, the minimum value of the second duty cycle and the fourth duty cycle, and the carrier signal of each power module.

17. The cascaded system according to claim 12, characterized in that, The cascaded system further includes an inductor, and the first port of the cascaded system is connected to a voltage source through the inductor. The control unit is further configured to: The number of high-frequency power modules is determined to be 1 or 2 based on the voltage of the voltage source. The high-frequency power module refers to a power module in high-frequency modulation mode.

18. The cascade system according to claim 17, characterized in that, The control unit is also used for: If the ratio of the voltage of the voltage source to the voltage of the second terminal of the power module N times is less than a preset ratio, the number of the high-frequency power modules is determined to be 1. If the ratio of the voltage of the voltage source to the voltage of the second terminal of the power module being N times greater than or equal to the preset ratio, the number of the high-frequency power modules is determined to be 2.

19. The cascade system according to claim 18, characterized in that, The preset ratio is 0.

2.

20. The cascade system according to claim 17, characterized in that, When the number of the high-frequency power modules is 2, the control unit is further configured to: If the input voltage of the high-frequency power module is an integer multiple of the output voltage, the high-frequency power module is synchronously controlled; and If the input voltage of the high-frequency power module is not an integer multiple of the output voltage, the high-frequency power module is controlled asynchronously.

21. The cascade system according to claim 20, characterized in that, The asynchronous control includes one of the following scenarios: simultaneously turning on the high-frequency power modules and not simultaneously turning them off; not simultaneously turning on the high-frequency power modules and simultaneously turning them off; or not simultaneously turning on the high-frequency power modules and not simultaneously turning them off.

22. The cascade system according to claim 17, characterized in that, The high-frequency power module can be determined by N power modules rotating in a timed or ordered manner.

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