Variable carrier amplitude-equal width PWM modulation method and system for AC-AC voltage regulation

Abstract

The application provides a variable-carrier-amplitude equal-width PWM modulation method and system for AC-AC voltage regulation, and relates to the technical field of power electronic converter modulation. The variable-carrier-amplitude equal-width PWM modulation method keeps the carrier frequency fixed, dynamically adjusts the carrier amplitude, and keeps the PWM on-pulse width in a preset range, thereby solving the technical problem that the PWM pulse width changes with the AC phase in the existing fixed-carrier-amplitude PWM modulation mode, and further causing uneven PWM pulse distribution, and realizing equal-pulse-width modulation in the AC-AC voltage regulation process.

Description

Technical Field

[0001] This invention relates to the field of power electronic converter modulation technology, specifically to a variable carrier amplitude equal-width PWM modulation method and system for AC-AC voltage regulation. Background Technology

[0002] With the widespread integration of distributed photovoltaic (PV) systems, new energy power generation devices, and high-power motor loads into low-voltage distribution network areas, the problem of voltage exceeding limits in these areas is becoming increasingly prominent. On the one hand, low voltage issues are prone to occur at the user side in situations involving long-distance power supply, high line impedance, and heavy end-point loads. On the other hand, in areas with high distributed PV penetration, power backflow can easily occur during the day when PV output is high, leading to localized high voltage problems in the area. Therefore, voltage regulation devices with rapid dynamic response capabilities are needed to achieve bidirectional compensation and continuous management of voltage in distribution areas.

[0003] AC-AC converters enable direct energy conversion from AC to AC side, and can be used for transformer substation voltage regulation, voltage compensation, and multi-mode voltage control. For a voltage regulation circuit based on AC-AC energy conversion, its single-phase power unit can be composed of four sets of four-quadrant paired switches, where S1 and S2 form the BUCK arm, and S3 and S4 form the BOOST arm. When the transformer substation voltage is too high, the circuit enters synchronous BUCK mode, suppressing the high voltage by outputting a reverse compensation voltage; when the transformer substation voltage is too low, the circuit enters synchronous BOOST mode, raising the low voltage by outputting a positive compensation voltage, thereby achieving bidirectional dynamic regulation of the transformer substation voltage. At the control modulation level, existing AC-AC voltage regulation circuits generally adopt PWM modulation, which compares a fixed-amplitude triangular carrier wave with a voltage modulation wave. This modulation method is simple in principle, highly adaptable to hardware, and easy to implement in terms of control logic, making it the mainstream modulation scheme for current AC-AC voltage regulation circuits.

[0004] However, in the PWM modulation method that compares the fixed amplitude triangular carrier wave with the modulation wave, the PWM pulse width will change with the AC phase due to the influence of the fixed amplitude carrier wave during AC voltage operation, resulting in uneven PWM pulse distribution. Summary of the Invention

[0005] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a variable carrier amplitude equal-width PWM modulation method and system for AC-AC voltage regulation, which solves the technical problem of uneven PWM pulse distribution caused by the variation of PWM pulse width with AC phase in existing fixed carrier amplitude PWM modulation methods.

[0006] (II) Technical Solution To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a variable carrier amplitude equal-width PWM modulation method for AC-AC voltage regulation, comprising: The AC input voltage, output voltage, and inductor current of the AC-AC voltage regulator are collected. The phase of the AC input voltage is obtained based on the AC input voltage, the amplitude of the output voltage is obtained based on the output voltage, and the effective value of the inductor current is calculated based on the inductor current. Based on the deviation between the output voltage setpoint and the output voltage amplitude, a current reference value is generated by the voltage outer loop controller; a synchronous sinusoidal modulation wave is generated based on the phase of the AC input voltage, and the positive half-cycle envelope value of the synchronous sinusoidal modulation wave is taken. Based on the deviation between the current reference value and the effective value of the inductor current, a duty cycle correction amount is generated by the current inner loop controller. The feedforward duty cycle is calculated based on the switching cycle average model of the AC-AC voltage regulator, and the feedforward duty cycle, duty cycle correction amount and preset equal pulse width duty cycle center value are combined and constrained to obtain the target equivalent duty cycle. Under the comparison logic that turns on when the carrier wave is greater than the modulating wave, the triangular carrier amplitude of the current switching cycle is dynamically calculated based on the positive half-cycle envelope value of the synchronous sinusoidal modulating wave and the target equivalent duty cycle. Based on the amplitude of the triangular carrier, a triangular carrier with a fixed frequency and variable amplitude is generated, and the triangular carrier is compared with the half-cycle envelope value to generate a PWM drive signal.

[0007] Preferably, the step of generating a current reference value through a voltage outer loop controller based on the deviation between the output voltage setpoint and the output voltage amplitude includes: Calculate the output voltage error : in, The output voltage setpoint; Indicates the output voltage amplitude; The current reference value is output through the voltage outer loop PI controller. : in, This is a limiting function; This is the reference value for the current output from the outer voltage loop. and These are the proportional and integral coefficients of the outer voltage loop, respectively. For the switching cycle, and These are the lower and upper limits of the current reference value, respectively. For the switching cycle index number, .

[0008] Preferably, the step of generating a synchronous sinusoidal modulation wave based on the phase of the AC input voltage and taking the positive half-cycle envelope value of the synchronous sinusoidal modulation wave includes: Generate a synchronous sinusoidal modulation wave based on the phase of the input voltage: in, This represents the instantaneous peak value of the sinusoidal signal at the current sampling moment; Indicates the phase of the AC input voltage; Pick Positive half-cycle envelope value: in, To synchronize the sinusoidal modulation wave, The envelope value of the positive half-cycle of the synchronous sinusoidal modulated wave participating in the carrier comparison.

[0009] Preferably, the step of generating a duty cycle correction amount through a current inner loop controller based on the deviation between the current reference value and the effective value of the inductor current includes: Current error for: in, This is the current reference value. This is the effective value of the inductor current; Current inner loop PI controller output duty cycle correction: in, This is the duty cycle correction amount for the inner current loop output; and These are the proportional coefficient and integral coefficient of the inner current loop, respectively; For the switching cycle index number, .

[0010] Preferably, the calculation of the feedforward duty cycle based on the switching cycle average model of the AC-AC voltage regulator includes: The average switching cycle model of the AC-AC voltage regulator in the current operating mode μ(k) is: in, The average voltage during the switching cycle at the output terminal. The duty cycle-voltage transfer function is determined by the current operating mode and the circuit topology. The current operating mode includes synchronous BUCK mode and synchronous BOOST mode. In synchronous BUCK mode, the following are available: Therefore, the switching period averaging model can be specifically expressed as: To ensure that the average output voltage reaches the target value, let: in, This indicates the target average voltage at the output terminal; Then we have: The feedforward duty cycle can be obtained from the above relationship. : When using the amplitude of the input voltage , Amplitude of output voltage When performing feedforward calculations, it is written as: .

[0011] Preferably, the calculation method for the target equivalent duty cycle includes: in, Indicates the target equivalent duty cycle; Represents the amplitude limiting function; This indicates the preset center value of the constant pulse width duty cycle; Indicates an unconstrained duty cycle. , This indicates the duty cycle correction amount. Indicates the feedforward duty cycle; Indicates the allowed duty cycle offset; Indicates the minimum duty cycle limit; This indicates the maximum duty cycle limit.

[0012] Preferably, under the comparison logic that enables conduction when the carrier wave is greater than the modulating wave, the triangular carrier amplitude of the current switching cycle is dynamically calculated based on the positive half-cycle envelope value of the synchronous sinusoidal modulating wave and the target equivalent duty cycle, including: Define the normalized triangular carrier wave as: The amplitude of the triangular carrier wave in the current switching cycle. for: in, This indicates the actual carrier amplitude during the current switching cycle; when If the control logic outputs the conduction signal, then the time length during which the triangular carrier wave is greater than the modulated wave is: Therefore, the duty cycle is: exist Furthermore, when carrier amplitude limiting is not triggered, the duty cycle obtained by the comparison logic satisfies the above relationship; when carrier amplitude limiting is triggered, the PWM conduction pulse width remains within the preset allowable range; Set the duty cycle Equal to the target equivalent duty cycle : The reference value of the carrier amplitude in the current switching cycle for: The actual carrier amplitude is obtained after limiting: in, and These are the lower and upper limits of the triangular carrier amplitude, respectively. The envelope value of the positive half-cycle of the synchronous sinusoidal modulated wave participating in the carrier comparison.

[0013] Preferably, the step of generating a triangular carrier with a fixed frequency and variable amplitude based on the amplitude of the triangular carrier, and comparing the triangular carrier with the half-cycle envelope value to generate a PWM drive signal includes: According to the triangular carrier amplitude Generate variable amplitude triangular carrier : The PWM comparator outputs the turn-on signal according to the following rules: in, This indicates that the current power switch combination is in the ON state. This indicates that the current power switch combination is in the off or freewheeling state; This indicates the actual carrier amplitude during the current switching cycle.

[0014] Preferably, the variable carrier amplitude equal-width PWM modulation method further includes: After the PWM signal is inserted with a dead time, it is adjusted according to the current operating mode. and input voltage polarity direction signal Assigned to the corresponding bridge arm: In synchronous BUCK mode, the BUCK bridge arm performs high-frequency complementary operation, while the BOOST bridge arm keeps S3 normally on and S4 normally closed. In synchronous BOOST mode, the BOOST bridge arm performs high-frequency complementary operation, while the BUCK bridge arm keeps S1 normally on and S2 normally closed. S1, S2, S3, and S4 are four sets of four-quadrant paired switching transistors in a voltage regulation circuit based on AC-AC energy conversion. S1 and S2 constitute the BUCK bridge arm, and S3 and S4 constitute the BOOST bridge arm.

[0015] Secondly, the present invention provides an AC-AC voltage regulation device for implementing the variable carrier amplitude equal pulse width PWM modulation method as described above, comprising: The voltage and current sampling module is used to collect AC input voltage, output voltage, and inductor current. The phase synchronization module is used to obtain the input phase θ(k) based on the AC input voltage and generate positive and negative half-cycle direction signals DIR(k); The voltage outer loop control module is used to generate a current reference value based on the deviation between the output voltage setpoint and the output voltage amplitude. The inner current control module is used to generate a duty cycle correction based on the deviation between the synchronous current reference and the inductor current. The feedforward duty cycle calculation module is used to calculate the feedforward duty cycle based on the average model of the AC-AC voltage regulator. The equal pulse width constraint module is used to determine the pulse width constraint based on the pulse width constraint. , , and Generate target equivalent duty cycle ; Synchronous sinusoidal modulation wave generation module, used to generate and ; The variable carrier amplitude calculation module is used to calculate the amplitude based on the carrier amplitude. and calculate ; The variable amplitude triangular carrier generation module is used to generate triangular carriers with fixed frequency and variable amplitude. ; PWM comparator module, used in Output conduction signal at the time; Dead-time insertion module is used to insert dead time into the complementary switch drive signal; The drive logic allocation module is used to allocate the PWM drive signal to the corresponding switching device according to the current working mode and the positive and negative half-cycle direction signals.

[0016] (III) Beneficial Effects This invention provides a variable carrier amplitude equal-width PWM modulation method and system for AC-AC voltage regulation. Compared with the prior art, it has the following advantages: The variable carrier amplitude equal-width PWM modulation method proposed in this invention keeps the PWM conduction pulse width within a preset range by dynamically adjusting the carrier amplitude while maintaining a fixed carrier frequency. This solves the technical problem of uneven PWM pulse distribution caused by the change of PWM pulse width with AC phase in the existing fixed carrier amplitude PWM modulation method, and realizes equal pulse width modulation in the AC-AC voltage regulation process. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A block diagram of a variable carrier amplitude equal-width PWM modulation method for AC-AC voltage regulation; Figure 2 This is a schematic diagram illustrating the generation of variable carrier amplitude PWM. Figure 3 Block diagram of a variable carrier amplitude constant pulse width PWM modulation system for an AC-AC voltage regulator; Detailed Implementation To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] This application provides a variable carrier amplitude equal-width PWM modulation method and system for AC-AC voltage regulation, which solves the technical problem of uneven PWM pulse distribution caused by the variation of PWM pulse width with AC phase in the existing fixed carrier amplitude PWM modulation method. It can generate a PWM drive signal with relatively consistent pulse width even under AC input voltage variation, BUCK / BOOST mode switching and dead-time freewheeling constraints.

[0020] The technical solution in this application is to solve the above-mentioned technical problems, and the general idea is as follows: Existing AC-AC voltage regulation circuits typically employ PWM modulation, which compares a fixed-amplitude triangular carrier wave with a modulating wave. While this method is structurally simple, it suffers from the following shortcomings in AC-AC voltage regulation scenarios: First, the input voltage of the AC-AC circuit is an alternating current, and its amplitude and polarity change periodically with time. Existing fixed amplitude carrier PWM modulation will cause the PWM pulse width to change significantly under different AC phases, resulting in uneven pulse distribution.

[0021] Secondly, when switching between high-voltage regulation and low-voltage regulation, the circuit needs to switch between synchronous BUCK mode and synchronous BOOST mode. Existing modulation methods are prone to pulse abrupt changes, abnormally narrow pulses or pulse loss in the mode switching interval.

[0022] Third, uneven PWM pulse width will make the high-frequency component distribution in the output compensation voltage complex, increasing the design difficulty of the subsequent filter; if the filter parameters are increased, the device size and cost will be increased, and the dynamic response speed will be reduced.

[0023] Fourth, the power switching devices in AC-AC circuits are not ideal devices, and a dead time is usually required when complementary switches operate. During the dead time, if the freewheeling state is not properly set, the inductor current may lose its freewheeling path, leading to increased voltage stress on the switching devices or even damage.

[0024] To address the aforementioned issues, this invention proposes a variable carrier amplitude equal-width PWM modulation method and system for AC-AC voltage regulation. This method enables the generation of PWM drive signals with relatively consistent pulse widths even under conditions of AC input voltage variation, BUCK / BOOST mode switching, and dead-time freewheeling constraints. This reduces filtering pressure, improves the quality of output compensation voltage, and enhances the operational reliability of the voltage regulation device.

[0025] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0026] Example 1: This invention proposes a variable carrier amplitude equal-width PWM modulation method for AC-AC voltage regulation, such as... Figure 1 As shown, it includes: S1. Collect the AC input voltage, output voltage and inductor current of the AC-AC voltage regulator; obtain the AC input voltage phase based on the AC input voltage; obtain the output voltage amplitude based on the output voltage; and calculate the effective value of the inductor current based on the inductor current. S2. Based on the deviation between the output voltage setpoint and the output voltage amplitude, a current reference value is generated through the voltage outer loop controller; a synchronous sinusoidal modulation wave is generated based on the phase of the AC input voltage, and the positive half-cycle envelope value of the synchronous sinusoidal modulation wave is taken. S3. Based on the deviation between the current reference value and the effective value of the inductor current, a duty cycle correction amount is generated by the current inner loop controller. S4. Calculate the feedforward duty cycle based on the switching cycle average model of the AC-AC voltage regulator, and combine the feedforward duty cycle, duty cycle correction amount and preset equal pulse width duty cycle center value to obtain the target equivalent duty cycle. S5. Under the comparison logic that is turned on when the carrier wave is greater than the modulating wave, the triangular carrier amplitude of the current switching cycle is dynamically calculated based on the positive half-cycle envelope value of the synchronous sinusoidal modulating wave and the target equivalent duty cycle. S6. Generate a triangular carrier with a fixed frequency and variable amplitude based on the amplitude of the triangular carrier, and compare the triangular carrier with the half-cycle envelope value to generate a PWM drive signal.

[0027] The variable carrier amplitude equal-width PWM modulation method proposed in this invention keeps the PWM conduction pulse width within a preset range by dynamically adjusting the carrier amplitude while maintaining a fixed carrier frequency. This solves the technical problem of uneven PWM pulse distribution caused by the change of PWM pulse width with AC phase in existing fixed carrier amplitude PWM modulation methods, and realizes equal pulse width modulation in AC-AC voltage regulation process.

[0028] The following is a detailed description of each step: In step S1, the AC input voltage, output voltage, and inductor current of the AC-AC voltage regulator are acquired. The phase of the AC input voltage is obtained based on the AC input voltage, the amplitude of the output voltage is obtained based on the output voltage, and the effective value of the inductor current is calculated based on the inductor current. The specific implementation process is as follows: The AC input voltage, output voltage, and inductor current of the AC-AC voltage regulator are collected. The control update cycle is defined as the k-th switching cycle, and the sampling quantity is defined as: From AC input voltage Extracting the phase of AC input voltage from the waveform In this embodiment of the invention, a second-order generalized integrator phase-locked loop (SOGI-PLL) is used to obtain... .

[0029] From output voltage Extract the output voltage amplitude from the waveform .

[0030] Based on inductor current Calculate the effective value of inductor current .

[0031] Where k represents the kth switching cycle as the control update cycle.

[0032] In step S2, a current reference value is generated by the voltage outer loop controller based on the deviation between the output voltage setpoint and the output voltage amplitude; a synchronous sinusoidal modulation wave is generated based on the phase of the AC input voltage, and the positive half-cycle envelope value of the synchronous sinusoidal modulation wave is taken; the specific implementation process is as follows: The outer voltage loop does not directly output the duty cycle; instead, it outputs a current reference value. This is because the outer voltage loop determines how much energy the system needs to increase or decrease based on the output voltage deviation, while the current reference serves as an intermediate variable for energy regulation.

[0033] The output voltage error is: in, The output voltage setpoint.

[0034] Reference value for the output current of the voltage outer loop PI controller: in, This is a limiting function used to prevent the current reference from exceeding the allowable range of power devices, inductors, or the system. This is the reference value for the current output from the outer voltage loop. and These are the proportional and integral coefficients of the outer voltage loop, respectively. For the switching cycle, and These are the lower and upper limits of the current reference value, respectively. For the switching cycle index number, .

[0035] Generate a synchronous sinusoidal modulation wave based on the phase of the input voltage: in, This represents the instantaneous peak value of the sinusoidal signal at the current sampling moment.

[0036] Take its positive half-cycle envelope value: in, To synchronize the sinusoidal modulation wave, This refers to the positive half-cycle envelope value of the synchronous sinusoidal modulating wave participating in carrier comparison. The modulating wave provides synchronous sinusoidal phase and half-cycle envelope information but does not directly undertake the main duty cycle adjustment function. The main duty cycle adjustment is handled by... Characterization is achieved through variable carrier amplitude.

[0037] Step S3: Based on the deviation between the current reference value and the effective value of the inductor current, a duty cycle correction amount is generated through the current inner loop controller. The specific implementation process is as follows: The current error is: in, This is the current reference value. This is the effective value of the inductor current.

[0038] Current inner loop PI controller output duty cycle correction: in, This is the duty cycle correction amount for the inner current loop output. and These are the proportional coefficient and integral coefficient of the inner current loop, respectively.

[0039] Step S4: Calculate the feedforward duty cycle based on the switching cycle average model of the AC-AC voltage regulator, and combine the feedforward duty cycle, duty cycle correction amount, and preset equal pulse width duty cycle center value into a constraint to obtain the target equivalent duty cycle. The specific implementation process is as follows: The average switching cycle model of the AC-AC voltage regulator in the current operating mode μ(k) is: in, The average voltage during the switching cycle at the output terminal. The duty cycle-voltage transfer function is determined by the current operating mode and the circuit topology. The current operating mode includes synchronous BUCK mode and synchronous BOOST mode.

[0040] In this embodiment of the invention, the feedforward duty cycle is calculated according to the voltage transfer relationship in synchronous BUCK mode. Ignoring power device voltage drop and switching ripple, the AC input voltage can be approximated as constant within a single switching cycle. Therefore, in synchronous BUCK mode: Therefore, the aforementioned average switching period model can be specifically expressed as: To ensure that the average output voltage reaches the target value, let: in, This indicates the target average voltage at the output terminal.

[0041] Then we have: The feedforward duty cycle can be obtained from the above relationship: When using the amplitudes of the input and output voltages for feedforward calculations, it can be written as: in, The duty cycle correction of the inner current loop output is combined with the feedforward duty cycle to obtain the unconstrained duty cycle: To achieve constant pulse width, a preset center value for the constant pulse width duty cycle is defined: in, Set the preset target conduction pulse width.

[0042] The target equivalent duty cycle is: in, To allow duty cycle offset, This indicates the minimum duty cycle limit. This indicates the maximum duty cycle limit.

[0043] Therefore, we can conclude that: At this time, the PWM conduction pulse width is: This formula is the theoretical basis for "equal pulse width".

[0044] In step S5, under the comparison logic that enables operation when the carrier wave is greater than the modulating wave, the triangular carrier amplitude of the current switching cycle is dynamically calculated based on the positive half-cycle envelope value of the synchronous sinusoidal modulating wave and the target equivalent duty cycle. The specific implementation process is as follows: Define the normalized triangular carrier wave as: The amplitude of the triangular carrier wave in the current switching cycle. for: in, This indicates the actual carrier amplitude during the current switching cycle.

[0045] The embodiments of the present invention employ a comparison logic of "conduction occurs when the carrier wave is greater than the modulating wave," that is... The output is turned on.

[0046] The time length during which the triangular carrier wave is greater than the modulating wave is: Therefore, the duty cycle is: exist Furthermore, if carrier amplitude limiting is not triggered, the duty cycle obtained by the comparison logic satisfies the above relationship; when carrier amplitude limiting is triggered, the PWM conduction pulse width remains within the preset allowable range.

[0047] Set the duty cycle Equal to the target equivalent duty cycle : The reference value of the carrier amplitude in the current switching cycle for: The actual carrier amplitude is obtained after limiting: in, and These are the lower and upper limits of the triangular carrier amplitude, respectively. This is used to avoid false triggering caused by excessively small carrier amplitude near zero crossing. Used to meet the upper limit of amplitude of controllers, comparators, or digital carrier generators.

[0048] In step S6, a triangular carrier with a fixed frequency and variable amplitude is generated based on the amplitude of the triangular carrier, and the triangular carrier is compared with the half-cycle envelope value to generate a PWM drive signal. The specific implementation process is as follows: Generate variable amplitude triangular carriers based on the aforementioned triangular carrier amplitudes: The PWM comparator outputs the turn-on signal according to the following rules: in, This indicates that the current power switch combination is in the ON state. This indicates that the current power switch combination is in the off or freewheeling state.

[0049] After the PWM signal is inserted with a dead time, it is adjusted according to the current operating mode. and input voltage polarity direction signal Assigned to the corresponding bridge arm: In synchronous BUCK mode, the BUCK arm performs high-frequency complementary operation, while the BOOST arm maintains S3 normally on and S4 normally closed. In synchronous BOOST mode, the BOOST arm performs high-frequency complementary operation, while the BUCK arm maintains S1 normally on and S2 normally closed. A schematic diagram of variable carrier amplitude PWM generation is shown below. Figure 2 As shown.

[0050] Example 2: This embodiment provides an AC-AC voltage regulation device with variable carrier amplitude and constant pulse width PWM modulation system for implementing the above method, including: The voltage and current sampling module is used to collect AC input voltage, output voltage, and inductor current. The phase synchronization module is used to obtain the input phase θ(k) based on the AC input voltage and generate positive and negative half-cycle direction signals DIR(k); The voltage outer loop control module is used to generate a current reference value based on the deviation between the output voltage setpoint and the output voltage amplitude. The inner current control module is used to generate a duty cycle correction based on the deviation between the synchronous current reference and the inductor current. The feedforward duty cycle calculation module is used to calculate the feedforward duty cycle based on the average model of the AC-AC voltage regulator. The equal pulse width constraint module is used to determine the pulse width constraint based on the pulse width constraint. , , and Generate target equivalent duty cycle ; Synchronous sinusoidal modulation wave generation module, used to generate and ; The variable carrier amplitude calculation module is used to calculate the amplitude based on the carrier amplitude. and calculate ; The variable amplitude triangular carrier generation module is used to generate triangular carriers with fixed frequency and variable amplitude. ; PWM comparator module, used in Output conduction signal at the time; Dead-time insertion module is used to insert dead time into the complementary switch drive signal; The drive logic allocation module is used to allocate the PWM drive signal to the corresponding switching device according to the current working mode and the positive and negative half-cycle direction signals.

[0051] It should be noted that, in the specific implementation process, the system also includes a soft-start module, which is used to generate a ramp-up output voltage reference value during the system startup phase and maintain it at the rated voltage reference value after it reaches the rated voltage reference value, so as to reduce the startup impact.

[0052] The following is combined with Figure 3 Explanation: In Figure 3 The hardware block for the voltage and current sampling module is not shown separately; the acquired AC input voltage, output voltage, and inductor current are directly fed into subsequent modules. The phase synchronization module uses a phase-locked loop (PLL). The voltage outer loop control module and the current inner loop control module correspond to the contents of the voltage and current dual closed-loop blocks in the diagram. The feedforward duty cycle calculation module and the equal pulse width constraint module correspond to the contents of the target duty cycle generation block in the diagram. The synchronous sinusoidal modulation wave generation module, the variable carrier amplitude calculation module, the variable amplitude triangular carrier generation module, PWM, the comparison module, the dead-time insertion module, and the drive logic allocation module correspond to the contents of the variable carrier amplitude modulation wave generation block in the diagram.

[0053] In summary, compared with existing technologies, it has the following beneficial effects: 1. This invention proposes a variable carrier amplitude equal-width PWM modulation method and system for AC-AC voltage regulation, which enables the generation of PWM drive signals with relatively consistent pulse widths under conditions of AC input voltage variation, BUCK / BOOST mode switching, and dead-time freewheeling constraints, thereby reducing filtering pressure, improving the quality of output compensation voltage, and enhancing the operational reliability of the voltage regulation device.

[0054] 2. This invention addresses the problems of existing fixed-amplitude carrier PWM modulation in AC-AC voltage regulation, such as large pulse width variation with AC phase, abnormally narrow pulses near zero crossing, significant impact of dead time and minimum conduction time, discontinuous pulses during mode switching, and high output filtering pressure. It proposes a modulation mechanism based on inversely calculating the carrier amplitude using the target equivalent duty cycle. By combining the voltage outer loop, current inner loop, input voltage feedforward, and equal pulse width constraints, a target equivalent duty cycle generation model is constructed. By using the half-cycle envelope value of the synchronous sinusoidal modulation wave and the target equivalent duty cycle together for carrier amplitude calculation, a deterministic relationship between "target duty cycle—carrier amplitude—PWM conduction pulse width" is established.

[0055] 3. This invention effectively overcomes the problems of uneven pulse width distribution, obvious extremely narrow pulses, and insufficient modulation consistency in fixed carrier amplitude PWM AC-AC voltage regulation. It significantly improves the pulse width stability of the PWM drive signal and the reliability of the power switch drive, reducing the impact of dead time, minimum conduction time, and comparator delay on the output waveform. Simultaneously, because the PWM conduction pulse width is constrained within a preset range, the high-frequency ripple distribution is more controllable, reducing the design difficulty of the output filter and the pressure of electromagnetic compatibility optimization. This method can balance output voltage regulation performance, inductor current dynamic tracking performance, and equal pulse width modulation effect. It is suitable for AC-AC voltage regulation devices with synchronous BUCK, synchronous BOOST, and input / output operating at the same frequency, and has good engineering implementation value and promising application prospects.

[0056] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0057] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A variable carrier amplitude equal-width PWM modulation method for AC-AC voltage regulation, characterized in that, include: The AC input voltage, output voltage, and inductor current of the AC-AC voltage regulator are collected. The phase of the AC input voltage is obtained based on the AC input voltage, the amplitude of the output voltage is obtained based on the output voltage, and the effective value of the inductor current is calculated based on the inductor current. Based on the deviation between the output voltage setpoint and the output voltage amplitude, a current reference value is generated by the voltage outer loop controller; A synchronous sinusoidal modulation wave is generated based on the phase of the AC input voltage, and the positive half-cycle envelope value of the synchronous sinusoidal modulation wave is taken. Based on the deviation between the current reference value and the effective value of the inductor current, a duty cycle correction amount is generated by the current inner loop controller. The feedforward duty cycle is calculated based on the switching cycle average model of the AC-AC voltage regulator, and the feedforward duty cycle, duty cycle correction amount and preset equal pulse width duty cycle center value are combined and constrained to obtain the target equivalent duty cycle. Under the comparison logic that turns on when the carrier wave is greater than the modulating wave, the triangular carrier amplitude of the current switching cycle is dynamically calculated based on the positive half-cycle envelope value of the synchronous sinusoidal modulating wave and the target equivalent duty cycle. Based on the amplitude of the triangular carrier, a triangular carrier with a fixed frequency and variable amplitude is generated, and the triangular carrier is compared with the half-cycle envelope value to generate a PWM drive signal.

2. The variable carrier amplitude equal-width PWM modulation method for AC-AC voltage regulation as described in claim 1, characterized in that, The step of generating a current reference value through a voltage outer loop controller based on the deviation between the output voltage setpoint and the output voltage amplitude includes: Calculate the output voltage error : in, The output voltage setpoint; Indicates the output voltage amplitude; The current reference value is output through the voltage outer loop PI controller. : in, This is a limiting function; This is the reference value for the current output from the outer voltage loop. and These are the proportional and integral coefficients of the outer voltage loop, respectively. For the switching cycle, and These are the lower and upper limits of the current reference value, respectively. For the switching cycle index number, .

3. The variable carrier amplitude equal-width PWM modulation method for AC-AC voltage regulation as described in claim 1, characterized in that, The step of generating a synchronous sinusoidal modulation wave based on the phase of the AC input voltage and taking the positive half-cycle envelope value of the synchronous sinusoidal modulation wave includes: Generate a synchronous sinusoidal modulation wave based on the phase of the input voltage: in, This represents the instantaneous peak value of the sinusoidal signal at the current sampling moment; Indicates the phase of the AC input voltage; Pick Positive half-cycle envelope value: in, To synchronize the sinusoidal modulation wave, The envelope value of the positive half-cycle of the synchronous sinusoidal modulated wave participating in the carrier comparison.

4. The variable carrier amplitude equal-width PWM modulation method for AC-AC voltage regulation as described in any one of claims 1 to 3, characterized in that, The step of generating a duty cycle correction amount through a current inner loop controller based on the deviation between the current reference value and the effective value of the inductor current includes: Current error for: in, This is the current reference value. This is the effective value of the inductor current; Current inner loop PI controller output duty cycle correction: in, This is the duty cycle correction amount for the inner current loop output; and These are the proportional coefficient and integral coefficient of the inner current loop, respectively; For the switching cycle index number, .

5. The variable carrier amplitude equal-width PWM modulation method for AC-AC voltage regulation as described in any one of claims 1 to 3, characterized in that, The calculation of the feedforward duty cycle based on the switching cycle average model of the AC-AC voltage regulator includes: The average switching cycle model of the AC-AC voltage regulator in the current operating mode μ(k) is: in, The average voltage during the switching cycle at the output terminal. The duty cycle-voltage transfer function is determined by the current operating mode and the circuit topology. The current operating mode includes synchronous BUCK mode and synchronous BOOST mode. In synchronous BUCK mode, the following are available: Therefore, the switching period averaging model can be specifically expressed as: To ensure that the average output voltage reaches the target value, let: in, This indicates the target average voltage at the output terminal; Then we have: The feedforward duty cycle can be obtained from the above relationship. : When using the amplitude of the input voltage , Amplitude of output voltage When performing feedforward calculations, it is written as: 。 6. The variable carrier amplitude equal-width PWM modulation method for AC-AC voltage regulation as described in any one of claims 1 to 3, characterized in that, The calculation method for the target equivalent duty cycle includes: in, Indicates the target equivalent duty cycle; Represents the amplitude limiting function; This indicates the preset center value of the constant pulse width duty cycle; Indicates an unconstrained duty cycle. , This indicates the duty cycle correction amount. Indicates the feedforward duty cycle; Indicates the allowed duty cycle offset; Indicates the minimum duty cycle limit; This indicates the maximum duty cycle limit.

7. The variable carrier amplitude equal-width PWM modulation method for AC-AC voltage regulation as described in any one of claims 1 to 3, characterized in that, Under the comparison logic that enables operation when the carrier wave is greater than the modulating wave, the triangular carrier amplitude of the current switching cycle is dynamically calculated based on the positive half-cycle envelope value of the synchronous sinusoidal modulating wave and the target equivalent duty cycle, including: Define the normalized triangular carrier wave as: The amplitude of the triangular carrier wave in the current switching cycle. for: in, This indicates the actual carrier amplitude during the current switching cycle; when If the control logic outputs the conduction signal, then the time length during which the triangular carrier wave is greater than the modulated wave is: Therefore, the duty cycle is: exist Furthermore, when carrier amplitude limiting is not triggered, the duty cycle obtained by the comparison logic satisfies the above relationship; when carrier amplitude limiting is triggered, the PWM conduction pulse width remains within the preset allowable range; Set the duty cycle Equal to the target equivalent duty cycle : The reference value of the carrier amplitude in the current switching cycle for: The actual carrier amplitude is obtained after limiting: in, and These are the lower and upper limits of the triangular carrier amplitude, respectively. The envelope value of the positive half-cycle of the synchronous sinusoidal modulated wave participating in the carrier comparison.

8. The variable carrier amplitude equal-width PWM modulation method for AC-AC voltage regulation as described in any one of claims 1 to 3, characterized in that, The step of generating a triangular carrier wave with a fixed frequency and variable amplitude based on the amplitude of the triangular carrier wave, and comparing the triangular carrier wave with the half-cycle envelope value to generate a PWM drive signal includes: According to the triangular carrier amplitude Generate variable amplitude triangular carrier : The PWM comparator outputs the turn-on signal according to the following rules: in, This indicates that the current power switch combination is in the ON state. This indicates that the current power switch combination is in the off or freewheeling state; This indicates the actual carrier amplitude during the current switching cycle.

9. The variable carrier amplitude equal-width PWM modulation method for AC-AC voltage regulation as described in any one of claims 1 to 3, characterized in that, The variable carrier amplitude equal-width PWM modulation method further includes: After the PWM signal is inserted with a dead time, it is adjusted according to the current operating mode. and input voltage polarity direction signal Assigned to the corresponding bridge arm: In synchronous BUCK mode, the BUCK bridge arm performs high-frequency complementary operation, while the BOOST bridge arm keeps S3 normally on and S4 normally closed. In synchronous BOOST mode, the BOOST bridge arm performs high-frequency complementary operation, while the BUCK bridge arm keeps S1 normally on and S2 normally closed. S1, S2, S3, and S4 are four sets of four-quadrant paired switching transistors in a voltage regulation circuit based on AC-AC energy conversion. S1 and S2 constitute the BUCK bridge arm, and S3 and S4 constitute the BOOST bridge arm.

10. A variable carrier amplitude equal pulse width PWM modulation system for implementing the variable carrier amplitude equal pulse width PWM modulation method as described in any one of claims 1 to 9, characterized in that, include: The voltage and current sampling module is used to collect AC input voltage, output voltage, and inductor current. The phase synchronization module is used to obtain the input phase θ(k) based on the AC input voltage and generate positive and negative half-cycle direction signals DIR(k); The voltage outer loop control module is used to generate a current reference value based on the deviation between the output voltage setpoint and the output voltage amplitude. The inner current control module is used to generate a duty cycle correction based on the deviation between the synchronous current reference and the inductor current. The feedforward duty cycle calculation module is used to calculate the feedforward duty cycle based on the average model of the AC-AC voltage regulator. The equal pulse width constraint module is used to determine the pulse width constraint based on the pulse width constraint. , , and Generate target equivalent duty cycle ; Synchronous sinusoidal modulation wave generation module, used to generate and ; The variable carrier amplitude calculation module is used to calculate the amplitude based on the carrier amplitude. and calculate ; The variable amplitude triangular carrier generation module is used to generate triangular carriers with fixed frequency and variable amplitude. ; PWM comparator module, used in Output conduction signal at the time; Dead-time insertion module is used to insert dead time into the complementary switch drive signal; The drive logic allocation module is used to allocate the PWM drive signal to the corresponding switching device according to the current working mode and the positive and negative half-cycle direction signals.

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