Ripple control method, controller and current conversion device

Abstract

The application discloses a ripple control method, a controller and a current conversion device, and relates to the technical field of power electronics. The ripple control method is used for an isolated DC-DC converter, and the method comprises the following steps: collecting a first DC voltage of a first DC end and a second DC voltage of a second DC end of the isolated DC-DC converter; obtaining a double-frequency ripple difference value based on the first DC voltage and the second DC voltage; compensating a DC deviation of the first DC voltage or a DC deviation of the second DC voltage by using the double-frequency ripple difference value to obtain a total voltage deviation; and controlling the isolated DC-DC converter based on the total voltage deviation. The method can compensate the DC deviation by using the voltage ripple difference value of the isolated DC-DC converter in reverse without increasing the hardware cost and volume, actively controls the energy throughput to suppress the low-frequency ripple of the bus, and thus can improve the overload capacity and system reliability.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a ripple control method, controller, and converter. Background Technology

[0002] With the acceleration of the global energy transition, the application of power conversion systems based on various new energy sources is becoming increasingly widespread. Among them, the core energy conversion equipment in power conversion systems—the converter (such as the PCS (Power Conversion System) in energy storage systems)—directly affects the efficiency, reliability, and cost of the entire system. The current market places higher demands on the short-term overload capacity of converters, with some products already achieving 1.2 to 1.5 times overload, and demand showing a trend towards 3 times overload. This harsh operating condition significantly intensifies the electrical stress on circuit components, far exceeding conventional design conditions.

[0003] In grid-connected operation, the output power of the converter will fluctuate periodically at twice the frequency (i.e., 100Hz or 120Hz) of the AC grid frequency (e.g., 50Hz or 60Hz). This power pulsation will inevitably be reflected on the DC side, resulting in significant voltage and current ripple at twice the power frequency on the DC bus capacitor of the converter. Under overload conditions, excessive voltage ripple amplitude will affect the accuracy of the modulation waveform and may even cause overmodulation, threatening system stability; while excessive low-frequency current ripple may exceed the rated ripple current withstand capacity of the bus capacitor, causing capacitor overheating, lifespan reduction, and in severe cases, equipment failure.

[0004] In power conversion systems requiring electrical isolation, isolated DC-DC converters such as LLC (Inductor-Inductor-Capacitor Resonant Converter) or DAB (Dual Active Bridge Converter) are typically used, dividing the two DC sides into inner and outer buses. The inner bus connects to the DC source of the preceding stage, while the outer bus connects to the inverter of the following stage. An ideal isolated DC-DC converter can effectively block the transmission of low-frequency ripple from the outer bus to the inner bus, thereby maintaining the stability of the inner bus voltage and protecting the preceding units from low-frequency stress. However, the low-frequency ripple problem on the outer bus capacitor still exists and becomes increasingly prominent with increasing power ratings and overload requirements.

[0005] To suppress low-frequency ripple in the external busbar, the relevant technologies mainly adopt the following two approaches: Option 1: Directly increase the capacitance of the external bus capacitor. This is a passive design based on margin. Although simple and reliable, it will directly lead to an increase in system cost, size and weight, reduce power density and efficiency, and under normal operating conditions that account for most of the operating time, the large-capacity capacitor is in a state of "overkill", resulting in a waste of resources.

[0006] Option 2: Use an APF (Active Power Filter). This option actively injects compensation current to cancel ripple by using additional power electronic switches, drive circuits, and passive components such as inductors and capacitors. While it can effectively suppress ripple, it significantly increases system complexity, cost, and potential failure points, reducing overall reliability. Furthermore, from an energy perspective, ripple originates from the periodic changes in capacitor energy storage; the active filter does not actually eliminate ripple energy but rather transfers it to its own branches, thus not fundamentally solving the problem.

[0007] Therefore, effectively managing the low-frequency ripple of the external bus of the isolated DC-DC converter without significantly increasing system cost, size, and complexity, especially in the pursuit of higher overload capacity, has become a key technical challenge for improving the performance, reliability, and power density of power conversion systems. Summary of the Invention

[0008] The purpose of this invention is to propose a ripple control method, controller, and converter device, which, without increasing hardware cost and size, utilizes the voltage ripple difference of the isolated DC-DC converter to reverse compensate for DC deviation, actively controls energy throughput to smooth low-frequency ripple on the bus, thereby improving overload capacity and system reliability.

[0009] In a first aspect, embodiments of the present invention propose a ripple control method for an isolated DC-DC converter. The method includes the following steps: acquiring a first DC voltage at a first DC terminal and a second DC voltage at a second DC terminal of the isolated DC-DC converter; obtaining a ripple difference of twice the power frequency based on the first DC voltage and the second DC voltage; compensating for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage using the ripple difference of twice the power frequency to obtain a total voltage deviation; and controlling the isolated DC-DC converter based on the total voltage deviation.

[0010] In some embodiments, obtaining the double power frequency ripple difference based on the first DC voltage and the second DC voltage includes: performing at least two different low-pass filters on the first DC voltage to obtain the DC component of the first DC voltage and a first DC voltage filter value that retains the double power frequency ripple; performing at least two different low-pass filters on the second DC voltage to obtain the DC component of the second DC voltage and a second DC voltage filter value that retains the double power frequency ripple; and obtaining the double power frequency ripple difference based on the first DC voltage filter value, the second DC voltage filter value, the DC component of the first DC voltage, and the DC component of the second DC voltage.

[0011] In some embodiments, obtaining the double power frequency ripple difference value based on the first DC voltage filter value, the second DC voltage filter value, the DC component of the first DC voltage, and the DC component of the second DC voltage includes: subtracting the first DC voltage filter value from the DC component of the first DC voltage to obtain a first double power frequency ripple voltage; subtracting the second DC voltage filter value from the DC component of the second DC voltage to obtain a second double power frequency ripple voltage; subtracting the product of the first double power frequency ripple voltage and a first voltage ratio from the second double power frequency ripple voltage to obtain the double power frequency ripple difference value, wherein the first voltage ratio is the ratio of the DC component of the second DC voltage to the DC component of the first DC voltage; or, subtracting the product of the second double power frequency ripple voltage and a second voltage ratio from the first double power frequency ripple voltage to obtain the double power frequency ripple difference value, wherein the second voltage ratio is the reciprocal of the first voltage ratio.

[0012] In some embodiments, the method further includes: comparing the double power frequency ripple difference value with a lower limit of ripple difference and an upper limit of ripple difference, respectively; if the double power frequency ripple difference value is greater than or equal to the lower limit of ripple difference and less than or equal to the upper limit of ripple difference, then performing the step of compensating for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage using the double power frequency ripple difference value; if the double power frequency ripple difference value is less than the lower limit of ripple difference, then compensating for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage using the lower limit of ripple difference; if the double power frequency ripple difference value is greater than the upper limit of ripple difference, then compensating for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage using the upper limit of ripple difference.

[0013] In some embodiments, the DC deviation of the first DC voltage is the difference between the reference voltage of the first DC voltage and the DC component of the first DC voltage, and the DC deviation of the second DC voltage is the difference between the reference voltage of the second DC voltage and the DC component of the second DC voltage.

[0014] In some embodiments, the step of using the double power frequency ripple difference to compensate for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage to obtain the total voltage deviation includes: summing the double power frequency ripple difference with the DC deviation of the first DC voltage as the total voltage deviation; or, summing the double power frequency ripple difference with the DC deviation of the second DC voltage as the total voltage deviation.

[0015] In some embodiments, controlling the isolated DC-DC converter based on the total voltage deviation includes: generating a duty cycle command using a controller based on the total voltage deviation; and adjusting the duty cycle of the switching transistors of the isolated DC-DC converter based on the duty cycle command.

[0016] In a second aspect, embodiments of the present invention provide a controller, including a memory, a processor, and a computer program stored in the memory. When the computer program is executed by the processor, it implements the ripple control method described in the first aspect embodiment.

[0017] Thirdly, embodiments of the present invention provide a converter device, comprising: an isolated DC-DC converter, wherein a first DC terminal of the isolated DC-DC converter is used to connect to a DC source; a DC-AC converter, wherein the DC terminal of the DC / AC converter is connected to a second DC terminal of the isolated DC-DC converter, and the AC terminal of the DC-AC converter is used to connect to an AC source or an AC load; and a controller as described in the third aspect embodiment, wherein the controller is connected to the control terminal of the switching transistor of the isolated DC-DC converter.

[0018] In some embodiments, the converter is a rectifier or an inverter.

[0019] The ripple control method, controller, and converter device of this invention, when performing ripple control on an isolated DC-DC converter, first acquire the first DC voltage at the first DC terminal and the second DC voltage at the second DC terminal of the isolated DC-DC converter; then, based on the first DC voltage and the second DC voltage, obtain a ripple difference of twice the power frequency, and use this ripple difference to compensate for the DC deviation of either the first or second DC voltage, obtaining the total voltage deviation; subsequently, based on the total voltage deviation, control the isolated DC-DC converter. Thus, without increasing hardware cost or size, the DC deviation can be compensated in reverse using the voltage ripple difference of the isolated DC-DC converter itself, actively controlling energy throughput to smooth low-frequency ripple on the bus, thereby improving overload capacity and system reliability.

[0020] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] Figure 1 This is a flowchart of a ripple control method according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of a converter device according to an embodiment of the present invention; Figure 3 This is a block diagram of ripple control according to an embodiment of the present invention; Figure 4 This is a schematic diagram illustrating the ripple control effect of an example of the present invention; Figure 5 This is a structural block diagram of a controller according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the converter device according to another embodiment of the present invention. Detailed Implementation

[0022] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0023] The ripple control method, controller, and converter of the present invention are described below with reference to the accompanying drawings.

[0024] Figure 1 This is a flowchart of a ripple control method according to an embodiment of the present invention. The ripple control method is used to isolate a DC-DC converter, which can be an LLC resonant converter or a DAB dual active bridge converter.

[0025] Taking DAB as an example, such as Figure 2 As shown, the isolated DC-DC converter 10 is a component of the converter device 100. Its first DC terminal is connected to a DC source (DC input), and its second DC terminal is connected to the DC-AC converter 20 in the converter device 100. The AC terminal of the DC-AC converter 20 is used to connect to an AC source (such as a grid) or an AC load (LOAD). The isolated DC-DC converter 10 is used to achieve electrical isolation and energy conversion between the two sides.

[0026] like Figure 1 As shown, the ripple control method includes the following steps: S11, acquire the first DC voltage at the first DC terminal and the second DC voltage at the second DC terminal of the isolated DC-DC converter.

[0027] See Figure 2 The first DC terminal of the isolated DC-DC converter 10 is the inner bus side, used to connect to DC inputs from photovoltaic arrays, energy storage batteries, etc.; the second DC terminal of the isolated DC-DC converter 10 is the outer bus side, connected to the DC terminal of the subsequent DC-AC inverter 20. The voltages of the two buses can be detected in real time using voltage sensors or sampling resistors. The sampling frequency must be at least twice the power frequency ripple frequency (e.g., for a 50Hz power frequency, the sampling frequency should be no less than 200Hz) to ensure effective acquisition of the ripple component. To improve control accuracy, the sampled values ​​can be filtered to remove high-frequency noise.

[0028] By separately acquiring the bus voltages on both sides of the isolated DC-DC converter 10, real-time voltage data containing twice the power frequency ripple component was obtained, providing a crucial input parameter for subsequent ripple suppression. This dual-end acquisition method can comprehensively reflect the difference in the impact of external bus ripple voltage on the internal bus, thus laying the foundation for voltage deviation-based compensation control.

[0029] S12, based on the first DC voltage and the second DC voltage, obtains twice the power frequency ripple difference.

[0030] Specifically, the ripple component at twice the power frequency is extracted from the second DC voltage (e.g., the 100Hz / 120Hz component is extracted using a bandpass filter or notch filter), and the corresponding frequency component is extracted from the first DC voltage. The difference between the two is then calculated. Alternatively, the instantaneous difference between the second DC voltage and the first DC voltage can be directly calculated, and then its twice-power frequency component is extracted using a bandpass filter. This difference reflects the degree of difference between the external bus ripple and the internal bus ripple after transmission through the isolated DC-DC converter 10.

[0031] By obtaining the ripple difference at twice the power frequency, the ripple voltage difference between the two buses of the isolated DC-DC converter 10 was accurately quantified, revealing the degree of residual influence of the external bus ripple on the internal bus voltage, and providing accurate ripple characteristic quantities for compensation control.

[0032] S13, use twice the power frequency ripple difference to compensate for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage to obtain the total voltage deviation.

[0033] This step involves using the double power frequency ripple difference obtained in step S12 as a compensation value and superimposing it onto the voltage deviation signal. Specifically, the DC deviation of the first DC voltage is first calculated. ,in, This is the reference value for the first DC terminal voltage. The DC component of the first DC voltage; or, the DC deviation of the second DC voltage. ,in, This is the reference value for the second DC terminal voltage. The DC component of the second DC voltage; then, twice the power frequency ripple difference. The total voltage deviation is obtained by superimposing it onto the selected DC deviation at an appropriate ratio (which can be adjusted by a proportional coefficient), such as... ,or, Where k1 and k2 are compensation coefficients, which can be tuned according to the system stability and ripple suppression requirements.

[0034] By introducing ripple difference compensation into the conventional voltage deviation, the control target can actively respond to changes in bus ripple, achieving active suppression of double power frequency ripple without relying on external active filtering or increasing capacitor value, thus providing a comprehensive deviation signal containing ripple information for subsequent control law design.

[0035] S14 controls the isolated DC-DC converter based on the total voltage deviation.

[0036] Specifically, the total voltage deviation obtained in step S13 can be... The input is sent to a controller (such as a PI (Proportional-Integral) controller, a PID (Proportional-Integral-Derivative) controller, a hysteresis controller, etc.), and the controller outputs a corresponding modulation signal (such as a PWM (Pulse Width Modulation) wave) to drive the switching transistors of the isolated DC-DC converter. By adjusting the on-time and duty cycle of the switching transistors, the energy transfer between the first and second DC terminals is controlled, ensuring that the actual voltage of the external bus follows the corresponding reference value, or the actual voltage of the internal bus follows the corresponding reference value, while actively canceling the double power frequency ripple on the second DC terminal. The control cycle should match the ripple frequency to ensure real-time response to ripple.

[0037] By directly controlling the isolated DC-DC converter 10 based on the total voltage deviation including ripple compensation, the isolated DC-DC converter 10 inherently possesses ripple suppression capability. This means that by actively adjusting energy throughput, a portion of the ripple energy from the external bus is fed back to the internal bus or supplemented from the internal bus, thereby smoothing low-frequency ripple from the external bus without adding hardware. This method improves system overload capacity and reliability while maintaining the advantages of high power density and low cost.

[0038] In some embodiments of the present invention, obtaining a double power frequency ripple difference based on a first DC voltage and a second DC voltage includes: performing at least two different low-pass filters on the first DC voltage to obtain a DC component of the first DC voltage and a first DC voltage filter value that retains double the power frequency ripple; performing at least two different low-pass filters on the second DC voltage to obtain a DC component of the second DC voltage and a second DC voltage filter value that retains double the power frequency ripple; and obtaining a double power frequency ripple difference based on the first DC voltage filter value, the second DC voltage filter value, the DC component of the first DC voltage, and the DC component of the second DC voltage.

[0039] Specifically, in some examples, such as Figure 3 As shown, a first low-pass filter LPF1 (such as a filter with a cutoff frequency higher than twice the power frequency but lower than the switching frequency, for example, 150Hz-200Hz for a 50Hz power frequency) is used to filter the second DC voltage. Filtering is performed to obtain a second DC voltage filter value that retains twice the power frequency ripple. The filtered value It contains a DC component and a ripple component at twice the power frequency, but filters out higher-frequency switching noise. Then, a second low-pass filter LPF2 (such as a filter with a cutoff frequency much lower than the power frequency, for example, 5Hz-10Hz) is used to filter the second DC voltage value. Filtering is performed to obtain the DC component of the second DC voltage. .

[0040] Similarly, for the first DC voltage collected... Perform the same two different low-pass filtering processes: obtain the first DC voltage filter value that retains twice the power frequency ripple through the third low-pass filter LPF3. The DC component of the first DC voltage is obtained through the fourth low-pass filter LPF4. .

[0041] In other examples, a low-pass filter (such as a filter with a cutoff frequency much lower than the power frequency, for example, 5Hz-10Hz) is used to filter the second DC voltage to obtain the DC component of the second DC voltage. Simultaneously, another low-pass filter (such as a filter with a cutoff frequency higher than twice the power frequency but lower than the switching frequency, for example, 150Hz-200Hz for a 50Hz power frequency) is used to filter the second DC voltage, resulting in a second DC voltage filter value that retains twice the power frequency ripple. .

[0042] Similarly, the first DC voltage is subjected to two different low-pass filtering processes to obtain the DC component of the first DC voltage. And retain the first DC voltage filter value with twice the power frequency ripple. .

[0043] Subsequently, the double power frequency ripple difference is calculated based on the above four quantities.

[0044] By employing two low-pass filters with different cutoff frequencies, the DC component and ripple component are decoupled and separated, thereby accurately calculating the ripple difference between the two buses at twice the power frequency. This method eliminates the need for complex bandpass filter design, utilizing only a simple combination of low-pass filters. It involves minimal computation, is easy to implement in engineering, and effectively filters out interference from high-frequency switching noise on ripple extraction, improving the accuracy of the ripple difference and the stability of the control system.

[0045] In some examples, a double power frequency ripple difference is obtained based on a first DC voltage filter value, a second DC voltage filter value, the DC component of the first DC voltage, and the DC component of the second DC voltage. This includes: subtracting the first DC voltage filter value from the DC component of the first DC voltage to obtain a first double power frequency ripple voltage; subtracting the second DC voltage filter value from the DC component of the second DC voltage to obtain a second double power frequency ripple voltage; subtracting the product of the first double power frequency ripple voltage and the ratio of the first voltage from the second double power frequency ripple voltage to obtain a double power frequency ripple difference, wherein the first voltage ratio is the ratio of the DC component of the second DC voltage to the DC component of the first DC voltage; or, subtracting the product of the second double power frequency ripple voltage and the ratio of the second voltage from the first double power frequency ripple voltage to obtain a double power frequency ripple difference, wherein the second voltage ratio is the reciprocal of the first voltage ratio.

[0046] Specifically, see Figure 3 Taking the product of the first twice-power-frequency ripple voltage and the ratio of the first voltage to the second twice-power-frequency ripple voltage as an example, the formula for calculating the twice-power-frequency ripple difference is as follows:

[0047] in, The ripple component is twice the power frequency ripple in the first DC voltage. The difference between the two components is the power frequency ripple component in the second DC voltage, which is the power frequency ripple difference between the two buses. , which is the first voltage ratio.

[0048] In other examples, a double power frequency ripple difference is obtained based on a first DC voltage filter value, a second DC voltage filter value, the DC component of the first DC voltage, and the DC component of the second DC voltage. This includes: subtracting the first DC voltage filter value from the DC component of the first DC voltage to obtain a first double power frequency ripple voltage; subtracting the second DC voltage filter value from the DC component of the second DC voltage to obtain a second double power frequency ripple voltage; dividing the first double power frequency ripple voltage by the DC component of the first DC voltage to obtain a first normalized ripple coefficient; dividing the second double power frequency ripple voltage by the DC component of the second DC voltage to obtain a second normalized ripple coefficient; calculating the difference between the second normalized ripple coefficient and the first normalized ripple coefficient, and then multiplying it by a reference voltage (such as a rated voltage or the average value of the DC component) to obtain the double power frequency ripple difference.

[0049] This example uses normalization to eliminate the impact of bus voltage amplitude differences on ripple comparison, making it suitable for scenarios operating over a wide voltage range.

[0050] In other embodiments of the present invention, the difference between the first DC voltage and the second DC voltage is obtained by: performing bandpass filtering on the second DC voltage to extract its ripple component at twice the power frequency; performing bandpass filtering on the first DC voltage to extract its ripple component at twice the power frequency; and calculating the difference between the two ripple components at twice the power frequency to obtain the difference between the two ripple components at twice the power frequency. Compared with the above-mentioned filtering scheme of at least two steps, this scheme directly extracts the ripple components on both sides for differential calculation, which is suitable for scenarios that require accurate comparison of the impact of ripple transmission.

[0051] In some embodiments of the present invention, the ripple control method further includes: comparing the ripple difference value of twice the power frequency with a lower limit value of ripple difference and an upper limit value of ripple difference, respectively; if the ripple difference value of twice the power frequency is greater than or equal to the lower limit value of ripple difference and less than or equal to the upper limit value of ripple difference, then performing the step of compensating for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage using the ripple difference value of twice the power frequency; if the ripple difference value of twice the power frequency is less than the lower limit value of ripple difference, then compensating for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage using the lower limit value of ripple difference; if the ripple difference value of twice the power frequency is greater than the upper limit value of ripple difference, then compensating for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage using the upper limit value of ripple difference.

[0052] For example, the DC deviation of the first DC voltage is the difference between the reference voltage of the first DC voltage and the DC component of the first DC voltage, and the DC deviation of the second DC voltage is the difference between the reference voltage of the second DC voltage and the DC component of the second DC voltage.

[0053] For example, the total voltage deviation is obtained by compensating for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage using the double power frequency ripple difference, including: summing the double power frequency ripple difference with the DC deviation of the first DC voltage as the total voltage deviation; or, summing the double power frequency ripple difference with the DC deviation of the second DC voltage as the total voltage deviation.

[0054] Specifically, to ensure the stability and safety of ripple compensation and to avoid overshooting or instability of the control system due to abnormal ripple differences, this invention adds a compensation amount limiting step, such as... Figure 3 As shown. The specific implementation is as follows: First, set the threshold range for ripple compensation, including the lower limit of ripple difference. Upper limit of ripple difference Among them, the lower limit value Can be negative or zero, upper limit value The value is positive, and the specific value can be pre-set based on the calculation method of twice the power frequency ripple difference, as well as the system rated voltage, bus capacitor withstand voltage rating, switching transistor current stress, and control stability requirements. For example, It can be set to ±5% of the rated voltage or determined based on empirical values.

[0055] Then, the double power frequency ripple difference value calculated in step S12 is used. Compared with the lower limit of ripple difference respectively and upper limit value Comparison: Scenario 1 (Normal Range): If This indicates that the current ripple difference is within a preset reasonable range, and the actual value can be directly used for compensation. At this point, step S13 is executed, utilizing... Compensation for DC deviation of the second DC voltage The total voltage deviation is obtained by taking the DC deviation of the first DC voltage.

[0056] Figure 3 Taking the DC deviation compensation of the second DC voltage as an example, the DC deviation of the second DC voltage is shown. The reference voltage for the second DC voltage DC component of the second DC voltage The difference between them.

[0057] Scenario 2 (below the lower limit): If This indicates that the detected ripple difference is too small (possibly too large in the negative direction), and directly using it for compensation may lead to incorrect control direction or insufficient compensation. In this case, discard the actual value and let... Instead, the lower limit of ripple difference is used as the compensation amount to compensate for DC deviation.

[0058] Scenario 3 (above the upper limit): If This indicates that the ripple difference is too large (possibly caused by sensor failure, transient impact, or abnormal operating conditions). Direct compensation may lead to overshoot or system protection. In this case, discard the actual value and set... Instead, the upper limit of the ripple difference is used as the compensation amount to compensate for the DC deviation.

[0059] Ultimately, the compensation amount after amplitude limiting will be... Superimposed on the selected DC deviation in the preset direction. The total voltage deviation is obtained from the above. .

[0060] By adding upper and lower limit comparisons and limiting mechanisms for ripple difference, the compensation amount can be constrained within a safe range, preventing over-compensation from causing overmodulation or device damage, and improving fault tolerance. Under normal operating conditions, ripple suppression is guaranteed; in abnormal situations, the limiting value takes over to achieve adaptive protection. The upper and lower limits can be uniformly set according to rated parameters, simplifying debugging complexity and facilitating product commercialization.

[0061] In some embodiments of the present invention, the isolated DC-DC converter is controlled based on the total voltage deviation, including: using a controller to generate a duty cycle command based on the total voltage deviation; and adjusting the duty cycle of the switching transistors of the isolated DC-DC converter based on the duty cycle command.

[0062] Specifically, the total voltage deviation obtained in step S13 The input is sent to the controller. This controller can be a proportional-integral (PI) controller, a proportional-integral-derivative (PID) controller, or other types of regulators. Taking a PI controller as an example... Figure 3 As shown, the total voltage deviation As the input to the PI controller, the signal is processed by the proportional and integral circuits to generate the corresponding duty cycle instruction D.

[0063] In a PI controller, the proportional gain determines the controller's response speed to the current deviation; the integral gain is used to eliminate steady-state error. The proportional element ensures that the system can respond quickly to voltage fluctuations, while the integral element ensures that the voltage tracks the reference value without steady-state error in steady state.

[0064] Subsequently, the generated duty cycle command D is sent to the PWM modulation module. The PWM modulation module generates corresponding switching drive signals (such as PWM pulse sequences) based on the duty cycle command D, adjusting the on and off times of the switching transistors (such as MOSFETs and IGBTs) in the isolated DC-DC converter. By controlling the duty cycle of the switching transistors, the energy transfer from the first DC terminal (inner bus) to the second DC terminal (outer bus) or in the reverse direction can be adjusted, ensuring that the actual voltage follows the reference value while actively canceling the double power frequency ripple on the second DC terminal.

[0065] It should be noted that the execution cycle of the controller and PWM modulation should match the ripple frequency (e.g., for a 50Hz power frequency, the control cycle is usually set to the level of 100μs to 1ms) to ensure real-time response to ripple.

[0066] By inputting the total voltage deviation into the controller to generate duty cycle commands, closed-loop control of the isolated DC-DC converter is achieved. The controller adjusts the duty cycle based on the total voltage deviation, including ripple compensation, actively absorbing and discharging energy to smooth low-frequency ripple on the external bus, achieving active ripple suppression without increasing hardware costs. The proportional element of the PI controller ensures rapid response to voltage fluctuations, while the integral element eliminates steady-state errors, balancing dynamic response and steady-state accuracy. By suppressing ripple and reducing bus capacitor current stress, capacitor overheating and lifespan degradation can be avoided, improving overload capacity and system reliability. The entire process relies on existing controllers and PWM modules, achieving simplicity, low cost, and maintaining high power density, demonstrating significant engineering application value.

[0067] In other embodiments of the present invention, the isolation DC-DC converter is controlled based on the total voltage deviation, including: inputting the total voltage deviation into the controller, the controller outputting a phase shift angle command; adjusting the phase shift angle between the primary H-bridge and the secondary H-bridge of the isolation DC-DC converter based on the phase shift angle command; and adjusting the direction and magnitude of energy transmission by controlling the magnitude and direction of the phase shift angle, thereby achieving closed-loop control and ripple suppression of the bus voltage.

[0068] This embodiment is applicable to DAB topologies and achieves bidirectional energy flow control through phase-shift modulation. It is particularly suitable for scenarios requiring bidirectional energy transfer (such as energy storage systems) and supports bidirectional power regulation while suppressing ripple.

[0069] Figure 4 The diagram shows the ripple control method before and after using an embodiment of the present invention. Figure 2 The diagram shows a comparison of voltage ripple and current ripple at the two DC terminals of the isolated DC-DC converter. Figure 4 As can be seen, after applying the method of the present invention, a balanced distribution of ripple is achieved between the high-voltage bus and the low-voltage bus capacitor.

[0070] In summary, the ripple control method of this invention, by introducing twice the power frequency ripple information into the control loop, can actively transport and suppress twice the power frequency ripple on the high-voltage bus capacitor without increasing the capacitance value of the high-voltage bus capacitor or introducing additional switching circuits, relying solely on the existing hardware architecture. Compared with traditional solutions, this invention not only has significant cost advantages and is more flexible and simple to implement, but also enables existing systems where the high-voltage bus capacitor is a limiting factor for overload capacity to effectively improve overload capacity simply through software upgrades.

[0071] The present invention proposes a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the ripple control method of the above embodiments.

[0072] Figure 5 This is a structural block diagram of a controller according to an embodiment of the present invention.

[0073] like Figure 5 As shown, the controller 500 includes a processor 501 and a memory 503. The processor 501 and the memory 503 are connected, for example, via a bus 502. Optionally, the controller 500 may also include a transceiver 504. It should be noted that in practical applications, the transceiver 504 is not limited to one, and the structure of the controller 500 does not constitute a limitation on the embodiments of the present invention.

[0074] Processor 501 may be a CPU (Central Processing Unit), a general-purpose processor, a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. It can implement or execute the various exemplary logic blocks, modules, and circuits described in conjunction with the disclosure of this invention. Processor 501 may also be a combination that implements computational functions, such as including one or more microprocessor combinations, a combination of a DSP and a microprocessor, etc.

[0075] Bus 502 may include a pathway for transmitting information between the aforementioned components. Bus 502 may be a PCI (Peripheral Component Interconnect) bus or an EISA (Extended Industry Standard Architecture) bus, etc. Bus 502 can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 5 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0076] The memory 503 stores a computer program corresponding to the ripple control method of the above embodiments of the present invention. This computer program is executed by the processor 501. The processor 501 executes the computer program stored in the memory 503 to implement the content shown in the foregoing method embodiments. Figure 5 The controller 500 shown is merely an example and should not be construed as limiting the functionality and scope of use of embodiments of the present invention.

[0077] The present invention also proposes a converter device.

[0078] like Figure 6 As shown, the converter 100 includes: an isolated DC-DC converter 10, a DC-AC converter 20, and a controller 500 as described in the above embodiment.

[0079] The first DC terminal of the isolated DC-DC converter 10 is used to connect to the DC input source; the DC terminal of the DC / AC converter 20 is connected to the second DC terminal of the isolated DC-DC converter 10; the AC terminal of the DC-AC converter 20 is used to connect to the AC source (such as the grid) or the AC load; and the controller 500 is connected to the control terminal of the switching transistor of the isolated DC-DC converter 10.

[0080] Specifically, the DC source can be of various types, including but not limited to: photovoltaic arrays (which can be connected to MPPT (Maximum Power Point Tracking) circuits), energy storage batteries, fuel cells, DC buses, electric vehicle power batteries, and DC inputs for server power modules. In other words, the converter device 100 of this invention can be widely used in the fields of photovoltaic energy storage, automotive, server power supply, and other DC-AC conversion scenarios requiring electrical isolation and ripple suppression. The isolated DC-DC converter 10 is used to achieve electrical isolation and energy conversion between the first DC terminal and the second DC terminal, while the DC-AC converter 20 is responsible for converting DC to AC or vice versa. The controller 500 is used to execute the ripple control method described in any of the foregoing embodiments, specifically including: acquiring the first DC voltage at the first DC terminal and the second DC voltage at the second DC terminal of the isolated DC-DC converter 10; obtaining a double power frequency ripple difference based on the first DC voltage and the second DC voltage; using the double power frequency ripple difference to compensate for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage to obtain the total voltage deviation; controlling the isolated DC-DC converter 10 based on the total voltage deviation, adjusting the duty cycle, phase shift angle or switching frequency of its switching transistors, thereby actively suppressing the double power frequency ripple on the second DC terminal.

[0081] In some examples, converter 100 is a rectifier or an inverter.

[0082] Specifically, when used as an inverter, the DC input (such as photovoltaic or battery) is converted into AC output to the grid or load via the isolated DC-DC converter 10 and DC-AC converter 20; when used as a rectifier, the AC input is converted into DC output via the DC-AC converter 20 (operating in rectification mode at this time) and the isolated DC-DC converter 10 to power DC loads or charge batteries.

[0083] By integrating the aforementioned ripple control method into a controller, the converter proposed in this invention can achieve the following beneficial effects: By adapting the first DC terminal to various DC sources such as photovoltaics, batteries, automotive power batteries, and server DC buses, it has achieved widespread application in fields such as photovoltaic energy storage power generation, electric vehicle charging and discharging, and server power supply, demonstrating significant platform-based promotion value. Through software algorithms, it actively suppresses double-frequency ripple without increasing the bus capacitor value or introducing additional active filter circuits, significantly reducing hardware costs and size while increasing power density. Active ripple suppression reduces ripple current stress on the DC bus capacitor, preventing capacitor overheating and lifespan degradation, enabling the converter to safely withstand higher overload conditions and improving overall reliability. By configuring rectification or inverter operating modes, it adapts to the needs of various application scenarios such as new energy power generation, energy storage systems, and V2G electric vehicles. For converters already in operation, only the software algorithm in the controller needs to be updated to effectively improve overload performance without replacing hardware, reducing upgrade and modification costs.

[0084] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0085] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0086] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0087] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0088] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A ripple control method, characterized in that, For isolating a DC-DC converter, the method includes the following steps: Collect the first DC voltage at the first DC terminal and the second DC voltage at the second DC terminal of the isolated DC-DC converter; Based on the first DC voltage and the second DC voltage, a power frequency ripple difference of twice is obtained; The total voltage deviation is obtained by compensating for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage using the double power frequency ripple difference. The isolated DC-DC converter is controlled based on the total voltage deviation.

2. The ripple control method according to claim 1, characterized in that, The step of obtaining twice the power frequency ripple difference value based on the first DC voltage and the second DC voltage includes: The first DC voltage is subjected to at least two different low-pass filters to obtain the DC component of the first DC voltage and the first DC voltage filter value that retains twice the power frequency ripple. The second DC voltage is subjected to at least two different low-pass filters to obtain the DC component of the second DC voltage and the second DC voltage filter value that retains twice the power frequency ripple. The double power frequency ripple difference is obtained based on the first DC voltage filter value, the second DC voltage filter value, the DC component of the first DC voltage, and the DC component of the second DC voltage.

3. The ripple control method according to claim 2, characterized in that, The process of obtaining the double power frequency ripple difference value based on the first DC voltage filter value, the second DC voltage filter value, the DC component of the first DC voltage, and the DC component of the second DC voltage includes: The first DC voltage filter value is subtracted from the DC component of the first DC voltage to obtain the first double power frequency ripple voltage; The second DC voltage filter value is subtracted from the DC component of the second DC voltage to obtain the second double power frequency ripple voltage; The product of the first twice-power-frequency ripple voltage and the ratio of the first voltage is subtracted from the second twice-power-frequency ripple voltage to obtain the twice-power-frequency ripple difference value, wherein the first voltage ratio is the ratio of the DC component of the second DC voltage to the DC component of the first DC voltage; or, The product of the second twice-power-frequency ripple voltage and the second voltage ratio is subtracted from the first twice-power-frequency ripple voltage to obtain the twice-power-frequency ripple difference value, wherein the second voltage ratio is the reciprocal of the first voltage ratio.

4. The ripple control method according to any one of claims 1-3, characterized in that, The method further includes: The twice power frequency ripple difference value is compared with the lower limit of ripple difference and the upper limit of ripple difference, respectively. If the double power frequency ripple difference is greater than or equal to the lower limit of the ripple difference and less than or equal to the upper limit of the ripple difference, then the step of using the double power frequency ripple difference to compensate for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage is executed. If the double power frequency ripple difference is less than the lower limit of the ripple difference, then the lower limit of the ripple difference is used to compensate for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage. If the double power frequency ripple difference is greater than the upper limit of the ripple difference, then the upper limit of the ripple difference is used to compensate for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage.

5. The ripple control method according to any one of claims 1-3, characterized in that, The DC deviation of the first DC voltage is the difference between the reference voltage of the first DC voltage and the DC component of the first DC voltage, and the DC deviation of the second DC voltage is the difference between the reference voltage of the second DC voltage and the DC component of the second DC voltage.

6. The ripple control method according to any one of claims 1-3, characterized in that, The step of using the double power frequency ripple difference to compensate for the DC deviation of the first DC voltage or the DC deviation of the second DC voltage to obtain the total voltage deviation includes: The sum of the double power frequency ripple difference and the DC deviation of the first DC voltage is taken as the total voltage deviation; or, The sum of the double power frequency ripple difference and the DC deviation of the second DC voltage is taken as the total voltage deviation.

7. The ripple control method according to any one of claims 1-3, characterized in that, The control of the isolated DC-DC converter based on the total voltage deviation includes: The controller generates a duty cycle command based on the total voltage deviation. Based on the duty cycle command, the duty cycle of the switching transistors of the isolated DC-DC converter is adjusted.

8. A controller comprising a memory, a processor, and a computer program stored in the memory, characterized in that, When the computer program is executed by the processor, it implements the ripple control method as described in any one of claims 1-7.

9. A converter, characterized in that, include: An isolated DC-DC converter, wherein the first DC terminal of the isolated DC-DC converter is used to connect to a DC source; A DC-AC converter, wherein the DC terminal of the DC / AC converter is connected to the second DC terminal of the isolated DC-DC converter, and the AC terminal of the DC-AC converter is used to connect to an AC source or an AC load; The controller as described in claim 8 is connected to the control terminal of the switching transistor of the isolated DC-DC converter.

10. The converter according to claim 9, characterized in that, The converter is either a rectifier or an inverter.

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