DC-DC control with frequency-dependent phase correction in voltage feedback
Patent Information
- Application Number
- PCT/DE2026/100224
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-10
- Filing Date
- 2026-02-24
- Publication Date
- 2026-09-17
Smart Images
Figure DE2026100224_17092026_PF_FP_ABST
Abstract
Description
[0001] 202500316 1
[0002] Description
[0003] DC-DC control with frequency-dependent phase boost in the voltage feedback
[0004] DC-DC converters are used particularly in vehicle electrical systems to adapt different voltage levels. For example, electric vehicles often have a high-voltage electrical system and a low-voltage electrical system. A DC-DC converter can be used to transfer power from the high-voltage system to the low-voltage system.
[0005] The high-voltage electrical system may contain loads that generate interference, and it is detrimental if this interference is significantly transmitted to the low-voltage electrical system. Filters are known to be used for interference suppression. However, these involve some costs.
[0006] It is therefore an object of the invention to demonstrate a way in which electrical energy can be transmitted via a DC-DC converter, whereby disturbances are dampened during this transmission.
[0007] This problem is solved by the subject matter of claim 1. Further properties, features, embodiments and advantages become apparent with the dependent claims, the description and the figures.
[0008] It was discovered that interference, for example from an inverter in an electric vehicle drive system, can also be transmitted via a DC / DC converter, which, like the inverter, is powered by a high-voltage electrical system. In particular, it was found that some of this interference lies in a frequency range where a control loop, such as one used to set the (constant) target voltage, reacts too slowly to reduce the interference through regulation.
[0009] As the frequency of the disturbances increases, the controller lags behind the disturbances, and the disturbances in the input voltage have a greater impact on the 202500316 2
[0010] Output voltage is lost. A first approach is therefore disturbance compensation using the measured input voltage, which is captured (especially through analog-to-digital conversion) and corrects the manipulated variable. The correction here counteracts the disturbance in the input voltage and ideally eliminates it. However, with increasing frequency, this method also becomes too slow because delays in measurement and manipulated variable realization lead to a phase shift. The manipulated variable correction thus lags behind the disturbance and, in the worst case, can even amplify rather than attenuate the disturbance in this frequency range.
[0011] The proposed solution for achieving improved ripple damping in the output voltage lies in an adapted phase boost of the measured input voltage. The phase boost can be tailored to the problematic frequency range and its amplitude can be adjusted. The problematic frequency range essentially corresponds to the frequency range to be suppressed. This frequency range is derived from the frequency spectrum of the interference generated by a component connected to the vehicle electrical system that carries the input voltage. The filtering thus involves a phase boost for the frequency range to be suppressed, which corresponds to at least a portion of the frequency spectrum of the interference generated by a component supplied with the input voltage (such as the converter) (i.e., the one connected to the first stage of the converter).(connected to an input side thereof). The component that is operated with the input voltage due to the same supply voltage or is connected to the first converter side is in particular a switching component, such as a pulse-width modulated power component like an inverter, preferably a traction inverter.
[0012] It is therefore proposed to operate the DC-DC converter not only according to a control variable of a control element (a regulator) that adjusts the actual output voltage and the (constant) target output voltage relative to each other, but also according to a filtered input voltage, whereby the filtering provides a phase boost for a predefined frequency range to be suppressed. This enables the control loop to
[0013] The aim is to suppress disturbances in the aforementioned frequency range through control, especially since these can be detected and compensated for by the control element or the control loop due to the increased phase.
[0014] A common method for controlling a DC-DC converter involves converting a voltage on one side of the converter (i.e., an input voltage or high voltage) into a voltage on the other side (i.e., an output voltage or low voltage). Despite operating the converter according to a control system, interference can still travel from the first to the second side. The approach described here provides a way for the converter to significantly suppress interference with higher frequencies (> 1 kHz or > 5 kHz), even if the control system is not inherently designed to handle this dynamic range. A target voltage (i.e., a constant value that can be adjusted) is input to the converter's control system. Furthermore, an actual voltage is input to the control system. These voltages refer to the second side of the converter.The setpoint voltage is a target output voltage or a target low-voltage voltage. The setpoint voltage is predetermined. The actual voltage is therefore an actual output voltage or an actual low-voltage voltage, specifically a measured voltage. These setpoint and actual values pertain to the second side of the converter. These setpoint and actual values, which are input to the control system, serve to determine the control error. The setpoint voltage corresponds to the reference input of the control system. The control is provided by a closed-loop control system. The actual voltage is input as the actual value for the control error calculation of the control system.
[0015] The control system is further inputted with an actual voltage relating to the first converter side, i.e., the input side of the converter. This actual voltage is the same voltage that supplies the disturbance-generating component. The actual voltage relating to the first converter side can also be referred to as the input actual voltage. This input actual voltage relating to the first converter side is combined with the control error resulting from the difference between the actual and setpoint voltages of the second converter side. The control system based on the actual and setpoint voltages relating to the second converter side generates a manipulated variable that is related to the actual voltage.
[0016] The signal is combined (e.g., by weighted addition, if necessary), which relates to the first converter side. The actual voltage relating to the first converter side is defined as a signal that reproduces the waveform of the actual voltage relating to the first converter side, or only AC components thereof, or in particular only high-pass filtered AC components thereof.
[0017] The control system operates according to a control objective that aims to minimize the difference between the setpoint voltage and the actual voltage on the second side of the converter. The control objective thus aims to minimize the control error (difference between the actual and setpoint voltage on the second side of the converter) or, more precisely, to minimize its magnitude. Since the setpoint voltage is constant or at least has no AC components > 50 Hz, this control objective also results in a secondary objective: to ensure that the actual voltage on the second side of the converter (i.e., the output voltage) has the lowest possible AC components (e.g., > 50 Hz).
[0018] The actual voltage of the first converter side is provided by passing the voltage applied to the first converter side through a filter. The signal, which is combined with the control input (output signal of the controller), is therefore a filtered signal. The transfer function of the filter provides a phase boost for the specified frequency range to be suppressed. The converter is driven according to the combined signal, so that the AC components on the first converter side are also included in the control. Due to feedback from the controller, the AC components are compensated. The AC components present in the combined signal are filtered AC components whose phase has been boosted by the filtering. This applies to the AC components that lie within the specified frequency range to be suppressed. The phase boost results in improved control behavior for the suppressed frequency range.
[0019] The aforementioned control objective includes the goal of minimizing alternating components in the actual voltage of the first converter side, since the control objective is to adapt the actual voltage of the second side as closely as possible to a constant (adjustable), predetermined target voltage of the second side. The "voltage of the second side" or "voltage referenced to the second side" is defined as 202500316 5
[0020] In particular, an output voltage is referred to (actual or target voltage). The term "first-side voltage" or "first-side reference voltage" refers in particular to an input voltage (actual voltage).
[0021] The frequency range to be suppressed includes at least one frequency that is too high for complete suppression during control according to the control objective (the most accurate possible matching to the target voltage of the second side). This frequency is higher than a maximum frequency or...
[0022] The maximum rate of change is determined by the dynamics of the control system, whereby the resulting control error remains a minimum error (approximately at least 1 ppm, 1%, 2%, 5%, or 10% of the amplitude of the frequency component exhibiting that frequency). Preferably, the lower limit of the frequency range to be suppressed is 2 kHz, 3 kHz, or 5 kHz. Alternatively, or in combination with this, the upper limit of the suppressed frequency range is at least 6 kHz, 8 kHz, or 10 kHz. The phase boost for the frequency range to be suppressed is up to 30°, 40°, or 50°. For a frequency range below the frequency range to be suppressed, a smaller phase boost and, optionally, a phase attenuation may be provided. This frequency range below the frequency range to be suppressed may extend from 0 Hz or another predetermined minimum frequency up to the frequency range to be suppressed.The phase shift for the frequency range to be suppressed can increase up to a certain frequency and then decrease again for higher frequencies above that specific frequency (to 0° or below). The phase shift is preferably at least 0° at the upper limit.
[0023] It may be provided that the attenuation of the filter decreases with increasing frequency, at least in one section of the frequency range to be suppressed, and that this section begins in particular at the lower limit of the frequency range to be suppressed. It may also be provided that the attenuation increases again from a certain frequency, for example, from 10 kHz or from 12 kHz. The attenuation begins to increase in particular from a frequency higher than the frequency at which the phase boost ends.
[0024] The difference between the setpoint voltage and the actual voltage of the second converter side is calculated, in particular by a differential element. This difference is preferably fed into a voltage control element. This element outputs the control signal, which is combined with the filtered actual voltage of the first filter side (actual input voltage) and output as a combined control signal to drive the converter. In addition to the feedback of the actual voltage (of the second converter side, i.e., the output side of the converter), there can also be feedback for the current (flowing at the second converter side, i.e., the output current). A current control element can be provided as a further control element for this purpose. The current control element receives the difference between a setpoint current of the second converter side and an actual current of the second converter side (actual and setpoint output currents). This difference can be calculated by another differential element.The difference is input to the current controller. The control signal output by the current controller can be combined with the control signal output by the voltage controller. This combination can be a selection (either the control signal output of one or the other controller is used as the control signal), a weighted average, or another combination, in particular an arithmetic combination. Furthermore, a control signal can be generated from the resulting combined signal, in particular by transformation into a pulse-width modulated signal whose duty cycle represents the (combined) control signal. The control signal can be a pulse-width modulated signal or can be transformed into a pulse-width modulated signal (PWM signal). The duty cycle of the (PWM signal) represents the amplitude of the resulting signal.
[0025] The error signal, which includes the difference between the target voltage and the actual voltage of the second converter side (approximately the control error, where the error signal can correspond to the difference), is preferably fed into a voltage control element. This element outputs a control signal. This control signal is used to control the converter. For this purpose, the control signal can be converted into a dual-level signal, for example, a pulse-width modulated signal. This can be performed in a computation block. The dual-level signal represents the (possibly varying) amplitude of the control signal.
[0026] In particular, the duty cycle and / or frequency of the dual-level signal determines the amplitude of the control signal. A mapping can be provided that maps the control signal to a duty cycle and / or frequency of the dual-level signal. This mapping specifically illustrates the converter's behavior at different duty cycles and / or frequencies. The converter's at least one switch is controlled by the dual-level signal. The dual-level signal can include an ON level and an OFF level, with these levels defining the corresponding switch position.
[0027] The frequency range to be suppressed preferably comprises at least one frequency which, when sampled (e.g., during measurement) with a sampling frequency, generates an error greater than a predetermined error threshold, which is particularly at 1%, 5%, 10%, 20%, or 40% of the actual amplitude of the current voltage. The frequency range to be suppressed preferably comprises at least one frequency which, when tracked by the control system, generates an error greater than a predetermined error threshold, which is particularly at 1%, 5%, 10%, 20%, or 40% of the actual amplitude of the current voltage. In this case, the limitation of the dynamic range leads to this error, or the error results from the limited (maximum) tracking rate (of the control variable) of the control system.This control-related error and the sampling-related error can also combine to produce an error that exceeds a predefined error threshold, which is typically 1%, 5%, 10%, 20%, or 40% of the actual voltage amplitude. In principle, the error can relate to the actual voltage amplitude, as described, or to the maximum amplitude range of the control system or the sampling process.
[0028] A vehicle DC-DC converter with a control device may be provided. This control device is preferably configured to implement the procedure described here. The vehicle DC-DC converter may have a high-voltage side, corresponding to the first converter side, and a low-voltage side, corresponding to the second converter side. The first converter side may be connected to, or configured for, a 400 V, 600 V, 800 V, or 1000 V electrical system. This electrical system includes, in particular, a (high-voltage) traction battery. The second
[0029] The converter side can be connected to a 48 V, 24 V, 14 V, or 12 V electrical system. The electrical systems are preferably part of the vehicle. The control device can, in particular, correspond to the DC-DC converter control device described below or at least have one of its features.
[0030] A DC-DC converter control device can be configured to implement the procedure described here. This control device has an input for receiving the voltage (input voltage, actual voltage at the input) applied to the first converter side. The control device has an output to which the filter described here is connected. This allows the voltage applied to the first converter side (i.e., the signal applied to the input) to be transmitted via the filter. The filter is part of the control device.
[0031] A computer program can be provided that is configured to implement the procedure described here. This computer program has interfaces for transferring values that represent the voltage at the first converter side (input voltage, actual voltage at the input) and a control signal provided by the controller. The interfaces are configured to transfer the control signal to another computer program and to receive the values (input voltage).
[0032] Figures 1 and 2 are exemplary representations used to describe embodiments of the invention.
[0033] Figure 1 symbolically shows a DC-DC converter W with a first converter side HS (high-voltage side) and a second converter side LS (low-voltage side). The converter W is preferably a buck converter. The voltage signal UH (input voltage) is applied to the first converter side HS, and the voltage signal UL (output voltage) is applied to the second converter side LS, and the voltage signal UL is applied to this converter side HS. The operation and, in particular, the control of the converter W of Figure 1 is shown in more detail in Figure 2.
[0034] The converter W, or rather a corresponding block W representing its transfer function, is shown in Figure 2. The voltage UH is applied to the converter W. This voltage UH is present at the first converter side (input side) of the converter W. The voltage UH corresponds to an actual voltage. Furthermore, the actual current II flows at the first converter side (input side) of the converter W. These two quantities can be determined by measurement.
[0035] The converter W outputs the actual voltage UL at an actual current IL. These values refer to the second converter side (output side). A closed control loop is implemented in which the actual voltage UL is fed back to a differential element, which calculates the difference between an input setpoint voltage US and the actual voltage UL. A voltage regulator RG1 receives this differential signal and outputs a corresponding control signal. When calculating B a control signal PWM, with which the converter W is controlled, not only this control signal from voltage regulator RG1 is considered, but also the actual voltage signal UH from the first converter side, which is filtered in a filter F. The resulting filtered signal UHF is then used to calculate B the control signal PWM.The PWM control signal is therefore based on a combination of the control signal output by the voltage regulator RG1 and the UHF signal, which results from passing the signal UH through filter F. The UHF signal is obtained by filtering the signal UH using filter F. Filter F is designed to perform a phase boost and output the signal with the boosted phase. The phase boost applies specifically to the frequency component of the input signal UH that lies within a predefined frequency range to be suppressed. This frequency range to be suppressed is determined by the spectrum of the interference that is introduced directly or indirectly into the voltage UH (input voltage) by one (or all) components. Specifically, the frequency range of the interference that comprises at least 10%, 25%, 50%, or 75% of the interference power corresponds to the frequency range to be suppressed, for which the phase is boosted.Phase enhancement results in improved controllability of the control loop, even if its dynamics are limited (i.e., its frequency range is limited by the transfer function and corresponds to a low-pass filter). A low-pass control loop has a cutoff frequency, which is 202500316 10.
[0036] The phase shift is located below the frequency range to be suppressed, or in a lower quarter or third of the frequency range to be suppressed. This allows the phase shift to at least partially compensate for the increasing damping of the control loop at higher frequencies, or the resulting dynamics of the control loop (which decreases with increasing frequency). The calculation of the control signal from the control signal of the control element RG1 and the filtered (filter F) UHF signal is based, in particular, on a proportional relationship between the voltage UL and the product of a duty cycle (of the PWM signal or a characteristic thereof) and the magnitude of the voltage UH.
[0037] In the embodiment shown in Fig. 2, a current control element RG2 is also provided. This element receives the difference between the set current IS (which should flow on the second converter side LS) and the actual current IS on the same side. The current control element RG2 generates a control signal from this error signal (difference between IS and IL). The control signal from the current control element RG2 and the voltage control element RG1 are combined in block M. This block can provide a combination of these control signals. The combined signal is passed to block B, where it is combined with the filtered actual current signal flowing on the first converter side to form a PWM control signal for the converter W.
[0038] A transmission path G1 (with a specific transfer function) can be provided in the feedback of the signal UL to the corresponding differential element. This transmission path reflects the behavior of a measurement, such as a measurement using an analog-to-digital converter. The measurement is a voltage measurement. Since this converter, in particular, can generate a relevant error for frequencies in the frequency range to be suppressed, a phase boost is implemented in the filter F, which at least partially compensates for the behavior of the measurement or the transmission path. The error caused by the measurement can consist, in particular, of a delay and / or signal alteration due to a digital-to-analog conversion. The phase boost compensates for this (at least partially) for frequencies in the frequency range to be suppressed.
[0039] An additional transmission path G2 (with a specific transfer function) can be provided in the feedback of the signal IL to the corresponding differential element. This transmission path reflects the behavior of a measurement, such as a measurement using an analog-to-digital converter. This measurement is a current measurement. Since this converter, in particular, can generate a significant error for frequencies in the frequency range to be suppressed, a phase boost is implemented in the filter F, which at least partially compensates for the behavior of the measurement or the additional transmission path. The error caused by the measurement can consist, in particular, of a delay and / or signal alteration due to a digital-to-analog conversion. The phase boost compensates for this (at least partially) for frequencies in the frequency range to be suppressed.
[0040] The transmission paths G1 and G2 are optional or arise as a parasitic effect and are therefore not part of the measure described here, but rather a (contributing) cause of the problem that is solved by the procedure described here. Therefore, these transmission paths are shown with dashed lines.
[0041] The transfer function of the filter (F) provides a phase boost for a specified frequency range to be suppressed, in order to at least partially compensate for the decreasing dynamic range with increasing frequency. This allows the transmission of interference in the specified frequency range via the transducer to be attenuated.
Claims
202500316 12 Patent claims 1. Method for controlling a DC-DC converter (W) that converts a voltage (UH) of a first converter side (HS) into a voltage (UL) of a second converter side (LS), wherein a control (R) is inputted with a setpoint voltage (US) and an actual voltage (UL), both of which refer to the second converter side (LS), and wherein the control (R) is further inputted with an actual voltage (UHF) that refers to the first converter side (HS), wherein the control is operated according to a control objective which provides for minimizing the difference between the setpoint voltage (US) and the actual voltage (UL) of the second converter side (LS), wherein the actual voltage (UHF) of the first converter side (HS) is provided by transferring the voltage (UH) applied to the first converter side (UH) via a filter (F), wherein the transfer function of the filter (F) provides a phase boost for a predetermined frequency range to be suppressed.
2. Method according to claim 1, wherein the frequency range to be suppressed includes at least one frequency that is too high for complete suppression in the control according to the second control objective, wherein preferably the lower limit of the frequency range to be suppressed is at 2 kHz, 3 kHz or 5 kHz and in particular extends to at least 6 kHz, 8 kHz or 10 kHz.
3. Method according to claim 1 or 2, wherein the maximum phase elevation is at least 30°, 40° or 50°.
4. Method according to claim 1, 2 or 3, wherein the attenuation of the filter (F) decreases with increasing frequency at least in one section of the frequency range to be suppressed, and this section in particular begins at the lower limit of the frequency range to be suppressed.
5. Method according to one of the preceding claims, wherein the difference between the set voltage (US) and the actual voltage (UL) of the second converter side (LS) is calculated and a voltage control element (RG1)202500316 13 is entered and the difference between a target current (IS) and an actual current (IL) of the second converter side (LS) is calculated and a current control element (RG2) is entered.
6. Method according to one of the preceding claims, wherein an error signal containing the difference between the target voltage (US) and the actual voltage (UL) of the second converter side (LS) is input to a voltage control element (RG1) which outputs a control signal which is converted (B) into a two-level signal, such as a pulse width modulated signal.
7. Method according to one of the preceding claims, wherein the frequency range to be suppressed comprises at least one frequency which, when sampled, for example during measurement, with a sampling frequency, produces an error greater than a predetermined error threshold, which is in particular 1%, 5%, 10%, 20% or 40% of the actual amplitude of the actual voltage.
8. Vehicle DC-DC converter with a control device configured for carrying out the method according to one of the preceding claims, wherein the vehicle DC-DC converter has a high-voltage side corresponding to the first converter side (HS) and a low-voltage side corresponding to the second converter side (LS).
9. DC-DC converter control device for carrying out the method according to one of claims 1-7, wherein the control device has an input for receiving the voltage (UH) applied to the first converter side (HS) and has an output to which the filter (F) is connected in order to transmit the voltage (UH) applied to the first converter side (UH) via the filter (F).
10. Computer program set up for executing the operation according to one of claims 1-7, wherein the computer program has interfaces for transferring values that represent the voltage (UH) at the first converter side (HS) and a control signal provided by the control unit (R).