Distributed carrier phase shifting method and system

Abstract

The application provides a method and system for dispersing carrier phase shift, which comprises at least two power modules connected in series and / or in parallel to form a modular system; each power module comprises a control module, the control module samples a common state variable at least twice, the slope of the common state variable at the first sampling time is opposite in sign to the slope of the common state variable at the second sampling time, and the time reference of the first sampling time of each control module is the same; and the carrier frequency of the power module is adjusted according to the relative size of the sampling value at the first sampling time and the sampling value at the second sampling time. According to the embodiment of the application, the carrier phase shift of the modular system connected in series or in parallel can be realized without the modules communicating with each other; meanwhile, the carrier phase shift can be automatically optimized under various duty cycle conditions through closed-loop control, and the system has good stability.

Description

Technical Field

[0001] This application relates to the field of carrier phase shifting technology, and in particular to a distributed carrier phase shifting method and system. Background Technology

[0002] Modular power electronic systems have a wide range of applications. For example, to cope with high-voltage power grids, multiple power modules are connected in series to form a cascaded system, such as... Figure 1 As shown, this reduces the withstand voltage of each power module. This cascaded system is widely used in medium-voltage motor drive frequency converters, power electronic transformers, high-voltage SVG, and other products. Another example is connecting multiple power modules in parallel to form a parallel system, such as... Figure 2 As shown, parallel systems are widely used in new energy power generation, energy storage and other fields.

[0003] For system control, controllers are typically installed on power modules to form a distributed control system, giving the modular system excellent flexibility, scalability, and reliability. To leverage the advantages of a modular system, coordinated operation between modules is essential. For example, inter-module carrier phase-shifting technology allows the switching of each power module to be staggered, significantly reducing the overall output voltage or current harmonics of the modular system. Existing carrier phase-shifting technology is usually based on communication, where a reference module or master controller simultaneously sends a synchronization signal to each power module. Upon detecting the synchronization signal, each power module adjusts its carrier phase to the corresponding phase-shift angle according to its module number. However, this method requires the participation of communication lines and places high demands on communication reliability. In practical communication, the system needs to continue operating stably without relying on communication after a communication failure.

[0004] To address the aforementioned issues, existing technologies typically employ a method of sampling common state variables. Common state variables refer to variables that can be sampled at the ports of each power module and are consistent across all modules, such as the current in a cascaded H-bridge system or the parallel point voltage in a multi-module parallel inverter system. Each power module obtains the zero-crossing point of the signal by sampling the same current or voltage signal and simultaneously updates its carrier wave to the corresponding phase shift angle. However, this method requires high accuracy in zero-crossing detection and also necessitates the power module's serial number. When the number of operating power modules changes, for example, if a power module malfunctions and the numbering order changes, communication is still required to rearrange the module numbers, thus not completely eliminating the dependence on communication. Summary of the Invention

[0005] In this context, one aspect of this disclosure is to provide a distributed carrier phase shifting method that enables carrier phase shifting of modular systems, such as series or parallel systems, even without a communication mode.

[0006] Another aspect of this disclosure provides a distributed carrier phase-shifting system.

[0007] According to one aspect of this disclosure, a distributed carrier phase shifting method is provided, comprising:

[0008] At least two power modules are connected in series and / or in parallel to form a modular system;

[0009] Each of the power modules includes a control module that samples a common state variable at least twice, wherein the slope of the common state variable at the first sampling time has the opposite sign to the slope of the common state variable at the second sampling time, and the time base of the first sampling time of each of the control modules is the same.

[0010] The carrier frequency of the power module is adjusted based on the relative magnitude of the sampled value at the first sampling time and the sampled value at the second sampling time.

[0011] Optional,

[0012] The same time base for the first sampling time includes each power module sampling at a specific moment in its own carrier cycle.

[0013] Optional,

[0014] The specific time includes the rising or falling edge of its own switch, or the time interval that lags the rising or falling edge by the same amount, and the time when its own carrier crosses zero or peak.

[0015] Optional,

[0016] At least two of the power modules are connected in series to form a series modular system. For the series modular system, the common state variable is the current flowing through all the power modules.

[0017] Optional,

[0018] At least two of the power modules are connected in parallel to form a parallel modular system. For the parallel modular system, the common state variable is the parallel port voltage.

[0019] Optional,

[0020] The interval between two adjacent sampling times is one equivalent carrier period T. eq ;

[0021] When bipolar modulation is used

[0022] When using frequency doubling unipolar modulation

[0023] Among them, Ts Let N be the carrier period of the power module, and N be the number of power modules, where N≥2.

[0024] Optional,

[0025] N power modules are cascaded into a single-phase bridge arm, and the single-phase bridge arm is connected in a Y-shape to form a three-phase Y-connected cascaded system.

[0026] When each of the power modules uses bipolar modulation, the interval between two adjacent sampling times is T. delay =T s / 2N; When the power module uses frequency doubling unipolar modulation, the interval between two adjacent sampling times is T. delay =T s / 4N, where Ts is the switching cycle of each power module.

[0027] Optional,

[0028] The method for adjusting the carrier frequency of the power module based on the relative magnitude of the sampled value at the first sampling time and the sampled value at the second sampling time is as follows:

[0029] The relative magnitude of the sampled value at the first sampling time and the sampled value at the second sampling time of the kth power module is used as the input of the adjustment controller, and the output of the adjustment controller is added to the preset carrier frequency to obtain the actual carrier frequency of the power module.

[0030] The actual carrier frequency is used as the input to the carrier generation module to generate the drive signal for the power module.

[0031] Optional,

[0032] The regulating controller is a proportional controller, a proportional-integral controller, a proportional-derivative controller, or a proportional-integral-derivative controller.

[0033] Optional,

[0034] The regulating controller is a proportional controller, and the proportional control coefficient K of the proportional controller is... p The method for determining the value is as follows:

[0035]

[0036] Where d is the duty cycle of the power module.

[0037] Optional,

[0038] The regulating controller is a proportional controller, the number of power modules N>3, and the proportional control coefficient K of the proportional controller is [missing information] throughout the entire power frequency cycle. p >0.

[0039] Optional,

[0040] The actual carrier frequency of the kth power module is:

[0041]

[0042] Among them, f sref The preset carrier frequency of the power module, Let M be the sampled value at the i-th sampling time of the k-th power module, and M represent the number of samplings in the carrier period Ts of the power module.

[0043] According to another aspect of this disclosure, a distributed carrier phase-shifting system is provided, comprising:

[0044] At least two power modules are connected in series and / or in parallel to form a modular system;

[0045] Each of the power modules includes a control module;

[0046] The control module is used to sample the common state variable at least twice. The slope of the common state variable at the first sampling time has the opposite sign to the slope of the common state variable at the second sampling time. The time base of the first sampling time of each control module is the same.

[0047] The carrier frequency of the power module is adjusted based on the relative magnitude of the sampled value at the first sampling time and the sampled value at the second sampling time.

[0048] Optional,

[0049] The same time base for the first sampling time includes each power module sampling at a specific moment in its own carrier cycle.

[0050] Optional,

[0051] The specific time includes the rising or falling edge of its own switch, or the time interval that lags the rising or falling edge by the same amount, and the time when its own carrier crosses zero or peak.

[0052] Optional,

[0053] At least two of the power modules are connected in series to form a series modular system. For the series modular system, the common state variable is the current flowing through all the power modules.

[0054] Optional,

[0055] At least two of the power modules are connected in parallel to form a parallel modular system. For the parallel modular system, the common state variable is the parallel port voltage.

[0056] Optionally, the interval between two adjacent sampling times is one equivalent carrier period T. eq ;

[0057] When bipolar modulation is used

[0058] When using frequency doubling unipolar modulation

[0059] Among them, T s Let N be the carrier period of the power module, and N be the number of power modules, where N≥2.

[0060] Optional,

[0061] N power modules are cascaded into a single-phase bridge arm, and the single-phase bridge arm is connected in a Y-shape to form a three-phase Y-connected cascaded system.

[0062] When each of the power modules uses bipolar modulation, the interval between two adjacent sampling times is T. delay =T s / 2N; When the power module uses frequency doubling unipolar modulation, the interval between two adjacent sampling times is T. delay =T s / 4N, where Ts is the switching cycle of each power module.

[0063] Optional,

[0064] The relative magnitude of the sampled value at the first sampling time and the sampled value at the second sampling time of the kth power module is used as the input of the adjustment controller, and the output of the adjustment controller is added to the preset carrier frequency to obtain the actual carrier frequency of the power module.

[0065] The actual carrier frequency is used as the input to the carrier generation module to generate the drive signal for the power module.

[0066] Optional,

[0067] The regulating controller is a proportional controller, a proportional-integral controller, a proportional-derivative controller, or a proportional-integral-derivative controller.

[0068] Optional,

[0069] The regulating controller is a proportional controller, and the proportional control coefficient K of the proportional controller is... p The method for determining the value is as follows:

[0070]

[0071] Where d is the duty cycle of the power module.

[0072] Optional,

[0073] The regulating controller is a proportional controller, the number of power modules N>3, and the proportional control coefficient K of the proportional controller is [missing information] throughout the entire power frequency cycle. p >0.

[0074] Optional,

[0075] The actual carrier frequency of the kth power module is:

[0076]

[0077] Among them, f sref The preset carrier frequency of the power module, Let M be the sampled value at the i-th sampling time of the k-th power module, and M represent the number of samplings in the carrier period Ts of the power module.

[0078] The distributed carrier phase shifting method provided in the above embodiments involves setting a control module in each power module. Each control module samples a common state variable at least twice, ensuring that the time base of the first sampling time is the same for each control module, and that the slope of the common state variable at the first sampling time has the opposite sign to the slope at the second sampling time. Then, the carrier frequency of the power module is adjusted based on the relative magnitudes of the sampled values ​​at the first and second sampling times. This distributed carrier phase shifting method achieves carrier phase shifting in modular systems such as series or parallel connections without requiring communication between control modules. Furthermore, through closed-loop control, it can automatically achieve optimal carrier phase shifting under various duty cycle conditions, exhibiting good stability. This method can also automatically support power module shutdown or module loading, achieving redundant operation and plug-and-play functionality.

[0079] Furthermore, the distributed carrier phase shifting method of this application embodiment can also be applied to various modular series-parallel systems, such as three-phase Y-connected cascaded systems, three-phase delta-connected cascaded systems, multi-module LLC resonant converter parallel systems, MMC modular multilevel converters, or medium- and high-voltage DC / DC converters composed of cascaded bridges. This is of great significance for improving the flexibility and scalability of modular systems. Attached Figure Description

[0080] The above and other objects, features and advantages of this disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0081] Figure 1 This is a flowchart illustrating the distributed carrier phase shifting method of this application;

[0082] Figure 2 This is a schematic diagram of the control principle of the distributed carrier phase shifting method of this application;

[0083] Figure 3 This is the circuit schematic of a cascaded system;

[0084] Figure 4 In response to Figure 3 The control principle diagram of the distributed carrier phase shifting method in the cascaded system embodiment shown;

[0085] Figure 5 This is a schematic diagram of carrier phase shift when d < 1 / N;

[0086] Figure 6 This is a schematic diagram of carrier phase shift when d > 1 / N;

[0087] Figure 7 This is a schematic diagram of carrier phase shift during multiple sampling;

[0088] Figure 8 In response to Figure 3 Simulation waveforms of the cascaded system embodiment shown;

[0089] Figure 9 In response to Figure 3 Simulation waveforms of the cascaded system embodiment shown when switching between different numbers of power modules;

[0090] Figure 10 This is a circuit schematic diagram of a three-phase Y-connected cascaded system.

[0091] Figure 11 In response to Figure 10 Simulation waveforms of an embodiment of a three-phase Y-connected cascaded system are shown;

[0092] Figure 12 This is a schematic diagram of a parallel modular system circuit.

[0093] Figure 13 In response to Figure 12 The control principle diagram of the distributed carrier phase shifting method in the parallel modular system embodiment shown is illustrated.

[0094] Figure 14 This is a circuit schematic of a multi-module LLC resonant converter system.

[0095] Figure 15 In response to Figure 14 The simulation waveforms of the multi-module LLC resonant converter system embodiment shown are obtained using the coordinated Burst method.

[0096] Figure 16 In response to Figure 14The simulation waveform of the multi-module LLC resonant converter system embodiment shown uses the distributed coordination Burst method. Detailed Implementation

[0097] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0098] It should be noted that when assigning reference numerals to components in the figures in this specification, although the same reference numerals are shown in different figures, the same reference numerals shall, as far as possible, represent the same components. Furthermore, in the description below of this disclosure, detailed descriptions of known functions and constructions incorporated herein will be omitted where such detailed descriptions would make the subject matter of this disclosure considerably unclear.

[0099] Furthermore, when describing elements of this disclosure, terms such as “first,” “second,” “A,” “B,” “(a),” and “(b)” may be used herein. These terms are used only to distinguish one element from other elements, and the nature, order, sequence, or number of the corresponding elements are not limited by these terms. When an element is described as being “connected to,” “coupled to,” or “linked to” another element, it will be understood that an element may not only be directly connected to or coupled to another element, but may also be “connected to,” “coupled to,” or “linked to” another element via a third element, or the third element may be inserted between one element and another element.

[0100] Furthermore, references to "an embodiment," "an embodiment," "an example embodiment," etc., indicate that the described embodiment may include specific features, structures, or characteristics, but not every embodiment must include these specific features, structures, or characteristics. Moreover, such statements do not refer to the same embodiment. Furthermore, when describing specific features, structures, or characteristics in connection with embodiments, whether or not explicitly described, it is indicated that incorporating such features, structures, or characteristics into other embodiments is within the knowledge of those skilled in the art.

[0101] Furthermore, certain terms are used in the specification and subsequent claims to refer to specific components or parts. Those skilled in the art will understand that manufacturers may use different names or terms to refer to the same component or part. This specification and subsequent claims do not distinguish components or parts by differences in name, but rather by differences in function. The terms "comprising" and "including" used throughout the specification and subsequent claims are open-ended and should be interpreted as "including but not limited to." Additionally, the term "connection" here includes any direct and indirect electrical connection means. Indirect electrical connection means include connections made through other means.

[0102] Figure 1 This is a schematic flowchart of a distributed carrier phase shifting method according to an embodiment of the present disclosure.

[0103] Figure 2 This is a control principle diagram of a distributed carrier phase shifting method according to an embodiment of the present disclosure.

[0104] As an example, this embodiment provides a distributed carrier phase shifting method, including:

[0105] S101. At least two power modules are connected in series and / or in parallel to form a modular system;

[0106] S102. Each of the power modules includes a control module that samples a common state variable at least twice, wherein the slope of the common state variable at the first sampling time has the opposite sign to the slope of the common state variable at the second sampling time, and the time base of the first sampling time of each of the control modules is the same.

[0107] In practical implementation, the modular system can be a cascaded system composed of multiple power modules connected in series, or a parallel system composed of multiple power modules connected in parallel. For the cascaded system, the common state variable is the current flowing through all the power modules; for the parallel modular system, the common state variable is the parallel port voltage. For the common state variable at the first and second sampling times, it is necessary to ensure that the sampling slope signs are opposite within the time interval between the two sampling times; simultaneously, it is necessary to ensure that each power module samples at a specific moment of its own carrier cycle, setting the time base for the first sampling moment of each power module to be the same. The selection of the time base for the first sampling moment can be chosen at the rising or falling edge of its own switch, or at a time interval lagging the rising or falling edge by the same amount, or at a specific moment such as the zero-crossing or peak moment of its own carrier.

[0108] Meanwhile, to ensure that the difference between the sampled values ​​at two adjacent sampling times reflects the relative phase relationship of each power module, a certain time interval is required between adjacent sampling times. This ensures that the voltage level of at least one power module's bridge arm changes between adjacent sampling times. The carrier phase is then adjusted to advance or delay this voltage level change, thereby altering the difference between the two sampled values. This is because if the carrier phase shift reaches a steady state, the current or voltage at two points within the equivalent carrier period between two adjacent sampling times is equal, and there is precisely one voltage level change in the bridge arm voltage of at least one power module within the equivalent carrier period. Therefore, this application preferably uses an equivalent carrier period T as the interval between two adjacent sampling times. eq That is, the sampling interval T delay =T eq When bipolar modulation is used, When using frequency doubling unipolar modulation Among them, T s Let N be the carrier period of the power module, and N be the number of power modules, where N≥2.

[0109] S103. Adjust the carrier frequency of the power module based on the relative magnitude of the sampled value at the first sampling time and the sampled value at the second sampling time. Specifically:

[0110] The relative magnitude of the sampled value at the first sampling time and the sampled value at the second sampling time of the kth power module is used as the input of the adjustment controller, and the output of the adjustment controller is added to the preset carrier frequency to obtain the actual carrier frequency of the power module.

[0111] The actual carrier frequency is used as the input to the carrier generation module to generate the drive signal for the power module.

[0112] In a specific implementation, the regulating controller can be a P, PI, PD, or PID controller. In this embodiment, a proportional controller is selected, and Kp is the proportional control coefficient of the proportional controller. p The value can be taken as follows: d represents the duty cycle of the power module, and N represents the number of power modules. That is, after achieving optimal carrier phase shift, the sampled value at the first sampling time and the sampled value at the second sampling time of each power module can be equal, or the steady-state difference between the sampled value at the first sampling time and the sampled value at the second sampling time of each power module can be equal.

[0113] Furthermore, the sampling of the common state variable in this application is not limited to two times; with M samplings per period, the actual carrier frequency of the k-th power module is expressed as:

[0114]

[0115] Among them, f sref The preset carrier frequency of the power module, Let M represent the sampled value at the i-th sampling time of the k-th power module, and let M represent the number of samples in the carrier period Ts of the power module. When each sample is equal to the average of the M sampled values, consistency of the M sampled values ​​is achieved, thus reaching the optimal carrier phase shift state. In one embodiment, the number of samples M is equal to the number of power modules N.

[0116] As mentioned earlier, for modular systems, carrier phase shifting is essential for coordinated operation between modules. However, in related technologies, the method of sampling common state variables requires high accuracy in zero-crossing detection. In addition, it requires the serial numbers of the power modules. When the number of operating power modules changes, the numbering order changes, and communication is still needed to rearrange the module numbers, so it cannot completely eliminate the dependence on communication.

[0117] The distributed carrier phase shifting method of this application embodiment sets up a control module in each power module. There is no communication between the control modules. Each control module samples the common state variable at least twice, ensuring that the time base of the first sampling time is the same for each control module, and that the slope of the common state variable at the first sampling time has the opposite sign to the slope of the common state variable at the second sampling time. Then, based on the relative magnitude of the sampled values ​​at the first and second sampling times, the carrier frequency of the power module is adjusted. This distributed carrier phase shifting method can achieve carrier phase shifting in modular systems such as series or parallel connections without communication between the control modules. Furthermore, through closed-loop control, it can automatically achieve optimal carrier phase shifting under various duty cycle conditions, exhibiting good stability.

[0118] like Figure 3 As shown, taking the carrier phase shift control of a cascaded system as an example, the cascaded system is a series modular system composed of at least two power module outputs connected in series. The common state variable is the current flowing through the outputs of all the power modules, and the carrier phase shift adjustment controller is a proportional controller. Figure 4 As shown in the figure, for the carrier phase shift control of the k-th power module, the common state variable sampled by the control module is the current i flowing through the power module. This is the first current sampling value of the k-th power module. This is the second current sampling value for the k-th power module. The first sampling was performed on the bridge arm voltage v of power module k. bk At the rising edge, that is, as Figure 3At the rising edges of switches Sk1 and Sk4 in the cascaded system shown, the second sampling lags the first sampling by a certain time interval T. delay The first current sampling value Compared with the second current sampling value The difference is used as the input to the proportional controller Kp, where Kp is the proportional control coefficient. The output of the proportional controller is related to the preset module carrier frequency f. sref The summation yields the actual carrier frequency of the power module. This actual carrier frequency is then used as the input to the carrier generation module, which generates a triangular carrier. The duty cycle d of the triangular carrier and the k-th power module are then calculated. k The drive signals for switches Sk1 and Sk4 are compared, and then the drive signals for switches Sk2 and Sk3 are generated by inverting the NOT logic. The duty cycle is generated by another current or voltage closed-loop control. The carrier phase shifting method of this application is not limited to being combined with a certain control algorithm.

[0119] Taking N=3 power modules as an example, such as Figure 5 This diagram illustrates carrier phase shift when d < 1 / N, where d represents the duty cycle of each power module, assuming all power modules have equal duty cycles. The solid lines in the diagram represent the positions of the arm voltages and currents generated by the current carrier, while the dashed lines represent the optimal positions of the arm voltages and currents under ideal carrier phase shift. The first current sampling is performed on the arm voltage v of the k-th power module. bk At the rising edge, the second sampling lags the first sampling by a certain time interval of one carrier period Ts. The current bridge arm voltage v of the second power module in the diagram... b2 Lagging ideal bridge arm voltage Positioning at a very small angle, this angular lag will cause a difference in the current between the two points sampled by the second power module. At this point, the proportional control coefficient Kp is set to < 0, and the carrier frequency of the second power module is increased, causing the carrier of the second power module to shift to the left. Through continuous closed-loop adjustment, the second power module gradually moves towards the optimal carrier position, ultimately ensuring that the three power modules achieve equal-interval carrier phase shift.

[0120] Figure 6 This diagram illustrates the carrier phase shift when d > 1 / N. As can be seen from the diagram, the current bridge arm voltage v of the second power module... b2 Lagging ideal bridge arm voltage A very small angle in the position will cause a lag that results in a difference in the current sampled at the two points by the third power module. At this point, the proportional control coefficient Kp > 0 is set to reduce the carrier frequency of the third power module. This lower carrier frequency causes a rightward shift in the phase of the carrier and its arm voltage, resulting in a greater time lag between the arm voltage of the third power module and that of the second power module. This further causes the first power module to shift the phase of its own carrier to the right, ultimately ensuring that the three power modules achieve equally spaced carrier phase shifts.

[0121] Meanwhile, for cascaded systems with N>3 power modules, since the time d>1 / N is much longer than d<1 / N in one power frequency cycle, the proportional control coefficient Kp of the proportional controller can be greater than 0 throughout the entire power frequency cycle to ensure that the control logic is correct most of the time and the system can operate stably.

[0122] Meanwhile, if the common state is sampled multiple times in each cycle, with M samples per cycle, such as... Figure 7 As shown in the diagram, there are a total of 3 power modules, and each power module is sampled three times. For example, the three sample values ​​of the first power module are... The time interval between two consecutive samples is the equivalent carrier period T. eq For the k-th power module, its carrier frequency is:

[0123]

[0124] The above formula indicates that the carrier frequency of this power module is adjusted based on the relative magnitude of the average value of the first sample and the Mth sample. When each sample is equal to the average value of the M sample values, the consistency of the M sample values ​​is achieved, thus reaching the optimal carrier phase shift state. In this embodiment, the number of samples M is equal to the number of power modules N, which is 3 times.

[0125] This application Figure 3 The simulation waveforms of the cascaded system embodiment shown are as follows: Figure 8 As shown. Taking N=4 as an example, the V of each power module dc =1500V. As can be seen from the graph, the carrier phase shift is stable under various grid voltage conditions, minimizing current ripple. Different AC voltage conditions correspond to different duty cycles, and the system operates stably under all duty cycles.

[0126] Since this application has a certain tolerance for the sampling interval and uses proportional control, it does not require that the two sampled values ​​be completely identical. For a cascaded system, when the power modules switch from N=4 to N=3, the simulation waveform is as follows: Figure 9 As shown, if four power modules are initially in operation, the equivalent carrier period is T. eq =T s / 4, when one power module exits operation, the remaining three power modules operate. However, because the control modules of each power module in the system do not communicate with each other, the control modules cannot know that the total number of power modules N has changed. Therefore, the interval T is still used. eq =T s Sampling at / 4 ensures system stability. If all three power modules are initially operational, the equivalent carrier period is T. eq =T s / 3, when one power module is loaded, all four power modules are running. However, because the control modules of each power module do not communicate with each other, the control modules cannot know that the total number of power modules N has changed. Therefore, the interval T is still used. eq =T s Sampling at / 3 allows the system to remain stable. Therefore, the distributed carrier phase-shifting method of this application can automatically support the loading and unloading of a certain number of power modules.

[0127] The dispersed carrier phase shifting method of this application can also be applied to, for example... Figure 10 The three-phase Y-connected cascaded system shown is characterized by N power modules cascaded into a single-phase bridge arm, which is then Y-connected to form the three-phase Y-connected cascaded system. In this system, carrier phase shifting reduces current harmonics; minimizing current harmonics is equivalent to minimizing line voltage harmonics. Each line voltage is synthesized from the bridge arm voltages of 2N power modules, for example, v. bAB =v bA1 +…+v bAN -(v bB1 +…+v bBN Each power module employs the distributed carrier phase-shifting method provided in this application, with the common state variable being the current flowing through all the power modules. Each power module uses bipolar modulation, and the interval between two adjacent sampling times is T. delay =T s / 2N, where Ts is the switching cycle of each power module. Simulation results are as follows: Figure 11 As shown, the initial phase is arbitrarily given, and the harmonics are relatively large. After the dispersed carrier phase shift of this application is initiated, the harmonics of the three line voltages and three currents gradually decrease and reach a stable state. In one embodiment, when each power module can use frequency-doubled unipolar modulation, the interval between two adjacent sampling times is T. delay =T s / 4N, where Ts is the switching cycle of each power module.

[0128] like Figure 12 As shown, for a parallel modular system, the carrier phase shifting method is as follows: Figure 13As shown, the parallel modular system uses the parallel port voltage as a common state variable. Each control module samples this common state variable. The specific carrier phase shift control logic is the same as that of the cascaded system described above, and will not be described in detail in this embodiment.

[0129] Another preferred embodiment of this application is as follows: Figure 14 The circuit shown is a parallel circuit of a multi-module LLC resonant converter. Since the efficiency of LLC is low if it operates continuously under light load, it is often operated in Burst mode, that is, it operates at high power for a period of time and then stops for a period of time, thus repeating the operation cyclically. This operation can improve efficiency, but the output voltage ripple becomes larger. Figure 15 To illustrate the coordinated Burst operation, taking three power modules as an example, each power module corresponds to one carrier wave. The carrier waves are phase-shifted, and their respective start / stop periods are the carrier periods. The duty cycle is determined by a separate voltage or current control algorithm. However, in the coordinated Burst operation using the carrier phase-shifting method of this application, the common state variable sampled is the output voltage. Figure 16 To improve the Burst simulation effect for distributed coordination of LLC, Figure 16 (a) Figure 16 (b) Figure 16 (c) Displayed as the resonant current of each power module. Figure 16 (d) Displaying the output voltage: Initially, each resonant current operates synchronously, resulting in a large output voltage ripple. By employing the distributed carrier phase shifting method of this application, the carrier phase shifting is achieved in a distributed closed-loop manner, thereby reducing the output voltage ripple.

[0130] The above embodiments only illustrate some applications of the distributed carrier phase shift control method of this application. It can also be applied to various modular series-parallel systems such as three-phase delta-connected cascaded H-bridge systems, MMC modular multilevel converters, or medium- and high-voltage DC-DC converters composed of cascaded bridges.

[0131] In summary, the distributed carrier phase shifting method of this application establishes a control module in each power module. Each control module samples a common state variable at least twice, with the first sampling time of each control module sharing the same time base. This ensures that the slope of the common state variable at the first sampling time has the opposite sign to the slope at the second sampling time. Then, the carrier frequency of the power module is adjusted based on the relative magnitudes of the sampled values ​​at the first and second sampling times. This distributed carrier phase shifting method achieves carrier phase shifting in modular systems such as series or parallel connections without requiring communication between the control modules. Furthermore, through closed-loop control, it automatically achieves optimal carrier phase shifting under various duty cycle conditions, exhibiting good stability. This method can also automatically support power module shutdown or module loading, enabling redundant operation and plug-and-play functionality. This method can also be applied to various modular series-parallel systems, such as three-phase Y-connected cascaded systems, three-phase delta-connected cascaded systems, multi-module LLC resonant converter parallel systems, MMC modular multilevel converters, or medium- and high-voltage DC-DC converters composed of cascaded bridges. It is of great significance for improving the flexibility and scalability of modular systems.

[0132] This application also provides a distributed carrier phase-shifting system, including:

[0133] At least two power modules are connected in series and / or in parallel to form a modular system;

[0134] Each of the power modules includes a control module;

[0135] The control module is used to sample the common state variable at least twice. The slope of the common state variable at the first sampling time has the opposite sign to the slope of the common state variable at the second sampling time. The time base of the first sampling time of each control module is the same.

[0136] The carrier frequency of the power module is adjusted based on the relative magnitude of the sampled value at the first sampling time and the sampled value at the second sampling time.

[0137] In some embodiments, the common time base for the first sampling time includes each power module sampling at a specific time of its own carrier cycle.

[0138] In some embodiments, the specific moment includes the rising or falling edge of its own switch, or the time interval lags the rising or falling edge by the same amount, and either at the zero or peak moment of its own carrier.

[0139] In some embodiments, at least two of the power modules are connected in series to form a series modular system, and for the series modular system, the common state variable is the current flowing through all the power modules.

[0140] In some embodiments, at least two of the power modules are connected in parallel to form a parallel modular system, and for the parallel modular system, the common state variable is the parallel port voltage.

[0141] In some embodiments, the interval between two adjacent sampling times is one equivalent carrier period T. eq ;

[0142] When bipolar modulation is used

[0143] When using frequency doubling unipolar modulation

[0144] Among them, T s Let N be the carrier period of the power module, and N be the number of power modules, where N≥2.

[0145] In some embodiments, N power modules are cascaded into a single-phase bridge arm, and the single-phase bridge arm is Y-connected to form a three-phase Y-connected cascaded system.

[0146] When each of the power modules uses bipolar modulation, the interval between two adjacent sampling times is T. delay =T s / 2N, when the power module uses frequency doubling unipolar modulation, the interval between two adjacent sampling times is T. delay =T s / 4N, where Ts is the switching cycle of each power module.

[0147] In some embodiments, the relative magnitude of the sampled value at the first sampling time and the sampled value at the second sampling time of the kth power module is used as the input of the adjustment controller, and the output of the adjustment controller is added to a preset carrier frequency to obtain the actual carrier frequency of the power module;

[0148] The actual carrier frequency is used as the input to the carrier generation module to generate the drive signal for the power module.

[0149] In some embodiments, the regulating controller is a proportional controller, a proportional-integral controller, a proportional-derivative controller, or a proportional-integral-derivative controller.

[0150] In some embodiments, the regulating controller is a proportional controller, and the proportional control coefficient K of the proportional controller is... p The method for determining the value is as follows:

[0151]

[0152] Where d is the duty cycle of the power module.

[0153] In some embodiments, the regulating controller is a proportional controller, the number of power modules N>3, and the proportional control coefficient K of the proportional controller is [value missing] throughout the entire power frequency cycle. p >0.

[0154] In some embodiments, the actual carrier frequency of the kth power module is:

[0155]

[0156] Among them, f sref The preset carrier frequency of the power module, Let M be the sampled value at the i-th sampling time of the k-th power module, and M represent the number of samplings in the carrier period Ts of the power module.

[0157] The above description and accompanying drawings are merely examples of the technical concept of this disclosure. Those skilled in the art will understand that various modifications and variations in form, such as combinations, separations, substitutions, and changes of structures, can be made to the embodiments described herein without departing from the essential characteristics of this disclosure. Therefore, the embodiments disclosed in this disclosure are not intended to limit but rather describe the technical concept of this disclosure, and thus do not limit the scope of the technical concept of this disclosure. The scope of this disclosure should be interpreted based on the appended claims, and all technical concepts included within the scope of equivalents of the appended claims should be interpreted as including within the scope of this disclosure.

[0158] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.

Claims

1. A distributed carrier phase shifting method, characterized in that, include: At least two power modules are connected in series and / or in parallel to form a modular system; Each of the power modules includes a control module that samples a common state variable at least twice. The slope of the common state variable at the first sampling time has the opposite sign to the slope of the common state variable at the second sampling time. The time base of the first sampling time of each of the control modules is the same. The carrier frequency of the power module is adjusted based on the relative magnitude of the sampled value at the first sampling time and the sampled value at the second sampling time.

2. The distributed carrier phase shifting method according to claim 1, characterized in that, The same time base for the first sampling time includes each power module sampling at a specific moment in its own carrier cycle; wherein, the specific moment includes the rising or falling edge of its own switch, or the time interval that lags the rising or falling edge by the same amount, and or at its own carrier zero crossing or peak moment.

3. The distributed carrier phase shifting method according to claim 1, characterized in that, At least two of the power modules are connected in series to form a series modular system. For the series modular system, the common state variable is the current flowing through all the power modules.

4. The distributed carrier phase shifting method according to claim 1, characterized in that, At least two of the power modules are connected in parallel to form a parallel modular system. For the parallel modular system, the common state variable is the parallel port voltage.

5. The distributed carrier phase shifting method according to claim 1, characterized in that, The interval between two adjacent sampling times is one equivalent carrier period. ; When bipolar modulation is used ; When using frequency-doubled unipolar modulation ; in, Let N be the carrier period of the power module, and N be the number of power modules, where N≥2.

6. The distributed carrier phase shifting method according to claim 1, characterized in that, N power modules are cascaded into a single-phase bridge arm, and the single-phase bridge arm is connected in a Y-shape to form a three-phase Y-connected cascaded system. When each of the power modules uses bipolar modulation, the interval between two adjacent sampling times is... When the power module uses frequency doubling unipolar modulation, the interval between two adjacent sampling times is... , where Ts is the switching cycle of each power module.

7. The distributed carrier phase shifting method according to any one of claims 1-5, characterized in that, The method for adjusting the carrier frequency of the power module based on the relative magnitude of the sampled value at the first sampling time and the sampled value at the second sampling time is as follows: The relative magnitude of the sampled value at the first sampling time and the sampled value at the second sampling time of the kth power module is used as the input of the adjustment controller, and the output of the adjustment controller is added to the preset carrier frequency to obtain the actual carrier frequency of the power module. The actual carrier frequency is used as the input to the carrier generation module to generate the drive signal for the power module.

8. The distributed carrier phase shifting method according to claim 7, characterized in that, The regulating controller is a proportional controller, a proportional-integral controller, a proportional-derivative controller, or a proportional-integral-derivative controller.

9. The distributed carrier phase shifting method according to claim 8, characterized in that, The regulating controller is a proportional controller, and the proportional control coefficient of the proportional controller is... The method for determining the value is as follows: Where d is the duty cycle of the power module.

10. The distributed carrier phase shifting method according to claim 8 or 9, characterized in that, The regulating controller is a proportional controller, the number of power modules N>3, and the proportional control coefficient of the proportional controller is [value missing] throughout the entire power frequency cycle. .

11. The distributed carrier phase shifting method according to claim 9, characterized in that, The actual carrier frequency of the kth power module is: in, The preset carrier frequency of the power module, Let M be the sampled value at the i-th sampling time of the k-th power module, and M represent the number of samplings in the carrier period Ts of the power module.

12. A distributed carrier phase-shifting system, characterized in that, include: At least two power modules are connected in series and / or in parallel to form a modular system; Each of the power modules includes a control module; The control module is used to sample the common state variable at least twice. The slope of the common state variable at the first sampling time has the opposite sign to the slope of the common state variable at the second sampling time. The time base of the first sampling time of each control module is the same. The carrier frequency of the power module is adjusted based on the relative magnitude of the sampled value at the first sampling time and the sampled value at the second sampling time.

13. The distributed carrier phase-shifting system according to claim 12, characterized in that, The same time base for the first sampling time includes each power module sampling at a specific moment in its own carrier cycle; wherein, the specific moment includes the rising or falling edge of its own switch, or the time interval that lags the rising or falling edge by the same amount, and or at its own carrier zero crossing or peak moment.

14. The distributed carrier phase-shifting system according to claim 12, characterized in that, At least two of the power modules are connected in series to form a series modular system. For the series modular system, the common state variable is the current flowing through all the power modules.

15. The distributed carrier phase-shifting system according to claim 12, characterized in that, At least two of the power modules are connected in parallel to form a parallel modular system. For the parallel modular system, the common state variable is the parallel port voltage.

16. The distributed carrier phase-shifting system according to claim 12, characterized in that, The interval between two adjacent sampling times is one equivalent carrier period. ; When bipolar modulation is used ; When using frequency-doubled unipolar modulation ; in, Let N be the carrier period of the power module, and N be the number of power modules, where N≥2.

17. The distributed carrier phase-shifting system according to claim 12, characterized in that, N power modules are cascaded into a single-phase bridge arm, and the single-phase bridge arm is connected in a Y-shape to form a three-phase Y-connected cascaded system. When each of the power modules uses bipolar modulation, the interval between two adjacent sampling times is... When the power module uses frequency doubling unipolar modulation, the interval between two adjacent sampling times is... , where Ts is the switching cycle of each power module.

18. The distributed carrier phase-shifting system according to any one of claims 12-17, characterized in that, The relative magnitude of the sampled value at the first sampling time and the sampled value at the second sampling time of the kth power module is used as the input of the adjustment controller, and the output of the adjustment controller is added to the preset carrier frequency to obtain the actual carrier frequency of the power module. The actual carrier frequency is used as the input to the carrier generation module to generate the drive signal for the power module.

19. The distributed carrier phase-shifting system according to claim 18, characterized in that, The regulating controller is a proportional controller, a proportional-integral controller, a proportional-derivative controller, or a proportional-integral-derivative controller.

20. The distributed carrier phase-shifting system according to claim 19, characterized in that, The regulating controller is a proportional controller, and the proportional control coefficient of the proportional controller is... The method for determining the value is as follows: Where d is the duty cycle of the power module.

21. The distributed carrier phase-shifting system according to claim 19 or 20, characterized in that, The regulating controller is a proportional controller, the number of power modules N>3, and the proportional control coefficient of the proportional controller is [value missing] throughout the entire power frequency cycle. .

22. The distributed carrier phase-shifting system according to claim 21, characterized in that, The actual carrier frequency of the kth power module is: in, The preset carrier frequency of the power module, Let M be the sampled value at the i-th sampling time of the k-th power module, and M represent the number of samplings in the carrier period Ts of the power module.

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