A direct current building power supply system and a method for operating control thereof

Abstract

This invention relates to the field of circuit device technology for DC power distribution networks, and proposes a DC building power supply system and its operation control method, including: after constructing a closed-loop detection environment for the base voltage, injecting a wideband excitation signal, calculating the impedance spectrum of the feeder port, determining the peak value of the feeder's inherent impedance and the main oscillation frequency, and determining the phase frequency change rate; calculating the load equivalent negative resistance limit, the target damping resistance value, and the filter quality factor, and generating a frequency domain damping shaping command; during the closed-loop operation phase of high-power charging, setting a discretized filter, introducing a damping soft-start strategy, calculating the corrected command, and driving the hardware circuit to suppress oscillations according to the corrected command. This invention can achieve stable power conversion.

Description

Technical Field

[0001] This invention relates to the field of circuit device technology for DC power distribution networks, and specifically to a DC building power supply system and its operation control method. Background Technology

[0002] In DC building power supply systems and microgrid applications, source-side power supply equipment such as AC / DC converters or DC / DC converters typically supply power to electric vehicle charging stations via DC buses and cables. However, due to variations in building layouts, the length of feeder cables can range from tens to hundreds of meters. The distributed inductance and capacitance introduced by long-distance cables, together with the input capacitance of the electric vehicle on-board charger, form a complex LC resonant network. Under closed-loop control, the electric vehicle on-board charger typically exhibits constant power load characteristics. In a small-signal model, a constant power load manifests as a negative incremental resistance. When the peak impedance at the feeder resonant point exceeds the absolute value of the load's negative resistance, the system damping becomes negative, and the bus voltage will oscillate continuously at the resonant frequency, potentially triggering system protection or damaging equipment.

[0003] To suppress the aforementioned oscillations, active damping can be used to simulate virtual resistance. However, active damping control typically uses fixed control parameters, which cannot adapt to feeder cables of varying lengths corresponding to different building layouts. The resonant frequency and peak shape of the line also change with the length of the feeder cable. When the control parameters for active damping are determined based on long cables, the filtering bandwidth is narrow, leading to frequency drift or insufficient coverage when short cables are connected, potentially causing suppression failure. Conversely, when the control parameters are determined based on short cables, the filtering bandwidth is wide, resulting in a large amount of unnecessary high-frequency switching noise when long cables are connected, degrading power quality. Summary of the Invention

[0004] This invention provides a DC building power supply system and its operation control method to solve the problem that the control parameters of the active damping method cannot be adapted to the different lengths of feeder cables corresponding to different building layouts, which easily leads to continuous oscillation of the bus voltage at the resonant frequency. The specific technical solution adopted is as follows: In a first aspect, one embodiment of the present invention provides a DC building power supply operation control method, the method comprising the following steps: After constructing the basic voltage closed-loop detection environment, a wideband excitation signal is injected, the impedance spectrum of the feeder port is calculated and the peak value is located, the inherent impedance peak value of the feeder and the main oscillation frequency are determined, and a local linear fitting in the frequency domain is performed based on the main oscillation frequency to determine the phase frequency change rate. The phase frequency change rate is used to characterize the local group delay at the resonance point. Read the maximum requested charging power and the minimum allowed charging voltage of the battery, calculate the equivalent negative resistance limit of the load, calculate the target damping resistance value based on the load equivalent negative resistance limit and the peak value of the inherent impedance of the feeder, and calculate the filter quality factor based on the main oscillation frequency and the phase frequency change rate. The main oscillation frequency, the target damping resistance value and the filter quality factor are used to quantify the center frequency, intensity and bandwidth of the damping, respectively. Before the closed-loop operation stage of high-power charging, generate frequency domain damping shaping instructions. During the closed-loop operation phase of high-power charging, a discretized filter is set according to the main oscillation frequency and the filter quality factor. A damped soft-start strategy is introduced to extract the reference value of the basic DC voltage. Combined with the target damping resistance value and the soft-start coefficient, the corrected command is calculated. Based on the corrected command, the hardware circuit is driven to suppress oscillation.

[0005] Furthermore, the specific calculation method for the impedance spectrum of the feeder port is as follows: While injecting the wideband excitation signal, the voltage and current sequences of the source power supply equipment port are simultaneously acquired to obtain the voltage and current vectors in the frequency domain. The ratio of the voltage and current vectors in the frequency domain is recorded as the impedance spectrum of the feeder port in the frequency domain.

[0006] Furthermore, the specific method for determining the peak value of the inherent impedance of the feeder and the main oscillation frequency is as follows: The maximum value of the feeder port impedance magnitude corresponding to all frequencies in the frequency domain is denoted as the feeder inherent impedance peak value, and the frequency corresponding to the feeder inherent impedance peak value is denoted as the main oscillation frequency.

[0007] Furthermore, the specific method for determining the phase frequency change rate is as follows: Centered on the main oscillation frequency, a local frequency window of a preset width is selected. Data pairs corresponding to discrete frequency points within the local frequency window are extracted from the impedance phase spectrum and frequency vector. Straight line fitting is performed on all data pairs corresponding to discrete frequency points, and the absolute value of the slope of the fitted straight line is recorded as the phase frequency change rate.

[0008] Furthermore, the load equivalent negative resistance limit is the ratio of the square of the minimum charging voltage to the maximum requested charging power for completing the data validity verification.

[0009] Furthermore, the specific calculation method for the target damping resistance value is as follows: The product of the equivalent negative resistance limit of the load and the preset stability margin coefficient is denoted as the impedance safety boundary. The difference between the peak value of the inherent impedance of the feeder and the impedance safety boundary is calculated, and the maximum value of the result is denoted as the number 0. The product of the maximum value and the preset engineering correction coefficient is denoted as the target damping resistance value.

[0010] Furthermore, the filter quality factor is: a preset bandwidth correction coefficient, a master oscillation frequency, a phase frequency change rate, and... The product of the products, where, It represents pi (π).

[0011] Furthermore, the method for setting the discretization filter is as follows: Read the master oscillation frequency and filter quality factor, and convert the transfer function of the second-order normalized bandpass filter in the second-order linear time-invariant system into a difference equation or Z-transfer function in the discrete domain to obtain the discretized filter.

[0012] Furthermore, a damped soft-start strategy is introduced, which extracts the baseline DC voltage reference value, combines it with the target damping resistance value and the soft-start coefficient, and calculates the corrected command. The specific methods include: Define a time Variable soft start coefficient : Preset soft start duration. The soft start coefficient increases linearly from 0 to 1 within the soft start duration. After the soft start duration is exceeded, the soft start coefficient remains constant at 1. The bus current is acquired in real time, and the oscillation current of a specific frequency band is extracted through a discretization filter; the product of the soft start coefficient, the target damping resistance value and the bus current is recorded as the real-time damping feedback correction amount. Request the reference value of the base DC voltage of the DC building power supply system, and use the difference between the reference value of the base DC voltage and the real-time damping feedback correction as the corrected command.

[0013] Secondly, embodiments of the present invention also provide a DC building power supply system, including a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor executes the computer program to implement the steps of any of the methods described above.

[0014] The beneficial effects of this invention are: This application aims to safely and accurately obtain the impedance characteristics of the electrical network consisting of the external feeder and load before the formal output of high-power charging current. It constructs a basic voltage closed-loop detection environment within the basic closed-loop detection time slot after the pre-charging phase ends and the contactor closes, extracts the group delay near the resonant point, and determines the phase frequency change rate. This avoids the influence of the original active damping or complex dynamic adjustment functions in the digital controller on the extraction of the actual line distributed parameter characteristics. Simultaneously, it avoids the problem of high-voltage DC bus voltage drift or even runaway caused by directly disconnecting the control loop. The frequency domain local linear fitting method can effectively ensure the stability of the phase frequency change rate value, providing a reliable benchmark for subsequent parameter mapping. Furthermore, after completing the extraction of the phase frequency change rate, the system enters a brief calculation interval based on... The inherent impedance peak value of the feeder, the rate of change of phase frequency, and the demand information of the external load are used to quantify the center frequency, intensity, and bandwidth of the damping, calculate a set of optimal control parameters, and generate frequency domain damping shaping commands. When the system enters the formal charging stage, a damping soft-start strategy is introduced to avoid directly superimposing the calculated damping correction amount onto the voltage command. This avoids the problem of the output signal stepping due to the mismatch between the initial value of the filter's internal state variables and the current signal. The frequency domain damping shaping command is smoothly converted into a real-time continuous control law to drive the hardware circuit to suppress oscillations. This solves the problem that the control parameter values ​​of the active damping method cannot adapt to the different lengths of feeder cables corresponding to different building layouts, which easily leads to continuous oscillation of the bus voltage at the resonant frequency, thus achieving stable power conversion. Attached Figure Description

[0015] 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.

[0016] Figure 1 This is a flowchart illustrating a DC building power supply operation control method according to an embodiment of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and 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.

[0018] Please see Figure 1The diagram illustrates a flowchart of a DC building power supply operation control method according to an embodiment of the present invention, which includes the following steps: Step S001: After constructing the basic voltage closed-loop detection environment, a wideband excitation signal is injected, the impedance spectrum of the feeder port is calculated and the peak value is located, the inherent impedance peak value of the feeder and the main oscillation frequency are determined, and a local linear fitting in the frequency domain is performed based on the main oscillation frequency to determine the phase frequency change rate. The phase frequency change rate is used to characterize the local group delay at the resonance point.

[0019] Select a bidirectional DC / DC converter or AC / DC rectifier as the source power supply device, and use the digital controller of the source power supply device to implement the following control process.

[0020] Before officially outputting high-power charging current, it is necessary to safely and accurately obtain the impedance characteristics of the electrical network formed by the external feeder and the load. Therefore, it is necessary to extract the group delay near the resonant point within the basic closed-loop detection time slot after the pre-charging stage ends and the contactor closes.

[0021] When extracting the group delay near the resonant point, it is first necessary to construct a closed-loop detection environment for the base voltage. Specifically, during impedance detection, in order to obtain the true characteristics of the line distributed parameters, it is necessary to temporarily disable the original active damping or complex dynamic adjustment functions in the digital controller. However, directly disconnecting the control loop will cause the high-voltage DC bus voltage to drift or even become uncontrollable, which is extremely unsafe in engineering. Therefore, this embodiment adopts the "base voltage closed-loop" mode.

[0022] Specifically, the digital controller confirms that the external contactor is closed and that the power supply equipment and load are electrically connected. The digital controller then switches the control mode to the base voltage closed-loop mode. In base voltage closed-loop mode, the digital controller performs the following operations: 1. Freeze Dynamic Branch: The gain of the high-frequency damping branch used to suppress oscillations in the control algorithm is forcibly set to zero, ensuring that the digital controller does not actively suppress high-frequency disturbance signals, thus exhibiting high-frequency open-loop characteristics. High-frequency disturbance signals refer to disturbance signals above 50Hz.

[0023] 2. Maintain Reference Closed Loop: A voltage proportional-integral regulator with an extremely low bandwidth (e.g., a cutoff frequency set to 10Hz to 20Hz) is retained solely to maintain the steady-state value of the DC bus voltage (e.g., 750V) to counteract slow voltage drift caused by leakage current. The cutoff frequency should be set to 10Hz to 20Hz, and the steady-state value of the DC bus voltage should be set to 750V.

[0024] Thus, the detection environment has been constructed. Specifically, a detection environment that is stable in the DC and low-frequency bands and can accurately reflect the impedance characteristics of the physical circuit in the high-frequency band has been constructed.

[0025] After the detection environment is constructed, a broadband excitation signal needs to be injected.

[0026] Due to the uncertainty of the feeder length, the resonant frequency may be distributed over a wide frequency band. In order to excite the full-band response of the system, a broadband signal with a flat power spectral density needs to be injected.

[0027] Specifically, in the base voltage closed-loop mode, the digital controller superimposes a wideband excitation signal onto the voltage reference command or current feedforward command.

[0028] The wideband excitation signal is selected from PRBS pseudo-random binary sequence or Chirp linear frequency modulation signal; the frequency coverage range of the wideband excitation signal is set to 0Hz to half of the system switching frequency, where 0Hz is DC and half of the system switching frequency is 5kHz; in order to prevent the injected signal from causing system overcurrent or load malfunction, the amplitude of the wideband excitation signal should be strictly limited to a preset proportion of the rated current of the source power supply equipment. In this embodiment, the amplitude of the wideband excitation signal is limited to 1% to 5% of the rated current of the source power supply equipment.

[0029] It is important to note that the continuous injection of wideband excitation signals into the digital controller should ensure that subsequent signal processing can obtain sufficient statistical data.

[0030] While injecting a wideband excitation signal, a high-frequency sampling device configured at the source power supply port is used to synchronously acquire the voltage and current sequences of the port. The sampling frequency of the high-frequency sampling device should be much higher than the expected highest resonant frequency.

[0031] The digital controller is used to perform Discrete Fourier Transform or Fast Fourier Transform on the acquired voltage and current sequences, respectively, to obtain the voltage and current vectors in the frequency domain. The ratio of the voltage and current vectors in the frequency domain is denoted as the feeder port impedance spectrum in the frequency domain.

[0032] The frequency domain feeder port impedance spectrum includes the magnitude and phase angle of the feeder port impedance at each frequency. If phase angle data exists... The transition is smoothed using a phase dewinding algorithm to obtain a continuous phase curve. Among these, It represents pi (π).

[0033] The maximum value of the feeder port impedance magnitude corresponding to all frequencies in the frequency domain is denoted as the feeder inherent impedance peak value, and the frequency corresponding to the feeder inherent impedance peak value is denoted as the main oscillation frequency.

[0034] Among them, the peak value of the inherent impedance of the feeder and the main oscillation frequency can preliminarily and quantitatively describe the maximum oscillation risk faced by the system and its location.

[0035] To further adapt the circuit's resonance mode by controlling parameters, it is necessary to extract the rate of change of the impedance phase. Since the raw sampled data inevitably contains noise, directly performing two-point difference or differentiation calculations on the phase spectrum will result in drastic jumps in the results, rendering them unusable. Therefore, a frequency domain local linear fitting method is used to robustly extract this feature.

[0036] Specifically, under the frequency domain local linear fitting method, the digital controller performs the following steps: 1. Determine the fitting window: A local frequency window is selected centered on the main oscillation frequency. In this embodiment, the width of the local frequency window is set to... When the discrete frequency points contained within a local frequency window are less than At this time, the width of the local frequency window is set to the main oscillation frequency. This ensures that the discrete frequency points contained within the local frequency window are greater than or equal to [the specified frequency]. One, of which This indicates a preset quantity; in this embodiment, the preset quantity is set to 5.

[0037] 2. Extract data subsets: Extract data pairs corresponding to discrete frequency points within the local frequency window from the impedance phase spectrum and frequency vector.

[0038] 3. Least squares fitting: Use the least squares method to perform univariate linear regression fitting on the data pairs corresponding to all the discrete frequency points mentioned above, and obtain the slope of the fitted line.

[0039] 4. Calculate the phase frequency change rate: The absolute value of the slope of the fitted straight line is denoted as the phase frequency change rate.

[0040] The phase-frequency change rate physically characterizes the group delay near the resonant point. For sharp resonant peaks caused by long feeders or low-loss lines, the phase changes extremely rapidly with frequency, resulting in a large calculated phase-frequency change rate. Conversely, for flat resonant peaks caused by short feeders or high-damping lines, the phase changes gradually, leading to a smaller calculated phase-frequency change rate. The frequency domain local linear fitting method effectively ensures the stability of the phase-frequency change rate value, providing a reliable benchmark for subsequent parameter mapping.

[0041] At this point, the phase frequency change rate is obtained.

[0042] Step S002: Read the maximum requested charging power and the minimum allowed charging voltage of the battery, calculate the equivalent negative resistance limit of the load, calculate the target damping resistance value based on the equivalent negative resistance limit of the load and the peak value of the inherent impedance of the feeder, and calculate the filter quality factor based on the main oscillation frequency and the phase frequency change rate. The main oscillation frequency, the target damping resistance value, and the filter quality factor are used to quantify the center frequency, intensity, and bandwidth of the damping, respectively. Before the closed-loop operation stage of high-power charging, a frequency domain damping shaping command is generated.

[0043] After extracting the phase frequency change rate, the system enters a brief calculation gap, where it needs to calculate a set of optimal control parameters based on the feeder's inherent impedance peak, phase frequency change rate, and external load requirements.

[0044] To determine whether and how much damping is needed for the system, it is first necessary to quantify the destructive impact of the electric vehicle's on-board charger load on system stability. In a small-signal model, a constant power load behaves as a negative resistance; the smaller the absolute value of this resistance, the more prone the system is to instability. To ensure stability across the entire operating range, estimations should be performed based on the "worst-case scenario."

[0045] Specifically, the digital controller reads the handshake message sent by the BMS (Battery Management System) through the communication interface to obtain the maximum requested charging power and the minimum allowable charging voltage of the battery. The communication interface can be, for example, a CAN bus or a PLC power line carrier.

[0046] It is important to note that the lowest allowable charging voltage of the battery is chosen here because, under constant power conditions, the lower the voltage, the higher the current, the smaller the absolute value of the corresponding negative resistance, and the lowest the system stability margin.

[0047] Considering that communication may be delayed or interrupted, or that the maximum requested charging power sent by the BMS in standby mode is zero, in order to prevent division by zero errors or parameter calculation failures, the digital controller performs data validity verification before calculation.

[0048] The data validity verification specifically involves: 1. Determine whether the maximum requested charging power is greater than the preset minimum power threshold, wherein, in this embodiment, the minimum power threshold is set to 1kW.

[0049] 2. If the maximum requested charging power is greater than the preset minimum power threshold, the maximum requested charging power is deemed valid, and the reading value of the maximum requested charging power is directly used in the calculation.

[0050] 3. If the maximum requested charging power is less than or equal to the preset minimum power threshold or a communication timeout occurs, the maximum requested charging power is deemed invalid, and the digital controller activates a safety fallback strategy. The safety fallback strategy uses the rated output power of the source power supply equipment itself as a substitute for the maximum requested charging power by default, assuming that the load will operate at the maximum capacity that the equipment can provide, which is the most conservative safety estimate.

[0051] Based on the minimum charging voltage and the maximum requested charging power for completing data validity verification, the load equivalent negative resistance limit under the worst operating conditions is calculated. The load equivalent negative resistance limit is the ratio of the square of the minimum charging voltage to the maximum requested charging power for completing data validity verification.

[0052] Thus, robust estimation of the equivalent negative resistance characteristic of the load is achieved, and the limit value of the equivalent negative resistance of the load is obtained.

[0053] According to the Middlebrook stability criterion, the system remains stable when the magnitude of the output impedance of the source power supply is much smaller than the load input impedance (i.e., the absolute value of the negative resistance). Therefore, the control objective is to reduce the peak impedance of the line below the safe limit. The load input impedance is the absolute value of the negative resistance.

[0054] The impedance safety boundary of the system is calculated based on the equivalent negative resistance limit of the load, which is the product of the equivalent negative resistance limit of the load and the preset stability margin coefficient.

[0055] The stability margin coefficient should be greater than or equal to 0.7 and less than or equal to 0.9. In this embodiment, the stability margin coefficient is 0.8.

[0056] The target damping resistance value is calculated based on the numerical relationship between the peak value of the inherent impedance of the feeder and the impedance safety boundary. The method for determining the target damping resistance value is as follows: calculate the maximum value of the difference between the peak value of the inherent impedance of the feeder and the impedance safety boundary and the number 0, and multiply the maximum value by a preset engineering correction coefficient, which is recorded as the target damping resistance value.

[0057] The engineering correction factor should be greater than or equal to 0.8 and less than or equal to 1.2. In this embodiment, the engineering correction factor is set to 1.0.

[0058] In calculating the target damping resistance value, selecting the maximum value aims to ensure that the target damping resistance value is not less than 0 when the peak value of the inherent impedance of the feeder itself is less than the impedance safety boundary. This avoids the unnecessary introduction of virtual damping, thereby preventing unnecessary control actions and power losses. When the peak value of the inherent impedance of the feeder itself is greater than the impedance safety boundary, the target damping resistance value is determined based on the impedance difference between the peak value of the feeder's inherent impedance and the impedance safety boundary. This ensures system stability while avoiding the problem of slowing down the system's dynamic response due to blindly applying excessive damping.

[0059] Although the suppression of parallel resonance peaks by series resistance is nonlinear in strict circuit theory, mapping the impedance difference directly to a virtual resistance value in the signal domain near the resonance point is an effective linearization approximation method that has been verified in engineering.

[0060] At this point, the digital controller has determined "how much force is needed" to suppress the oscillation, realized the differential quantitative calculation of the target damping resistance value, obtained the target damping resistance value, and quantified the damping strength parameter.

[0061] After determining the target damping resistance value, it is necessary to further determine the frequency domain form of the damping effect, namely the "damping bandwidth", which is the key to solving the problem of adapting long and short lines.

[0062] To ensure that the virtual damping acts precisely on the frequency band where the resonant energy is concentrated, a bandpass filter needs to be constructed. The quality factor of the filter determines the width of the passband; the quality factor is the Q value. The higher the Q value, the narrower the passband; the lower the Q value, the wider the passband.

[0063] It is important to understand that for long feeder systems, the resonant peak is usually sharp and narrow, and the Q value is high. If the filter bandwidth is too wide, it will introduce switching noise in the non-resonant frequency band. For short feeder systems, the resonant peak is usually flat and wide, and the Q value is low. If the filter bandwidth is too narrow, the damping coverage may fail due to frequency drift.

[0064] Although actual long feeders are distributed parameter systems with an infinite number of resonant modes, the main resonant point with the highest amplitude has the greatest impact on system stability analysis. Therefore, this embodiment uses the dominant pole approximation theory to treat the feeder characteristics as a second-order system for parameter tuning near the main oscillation frequency.

[0065] Specifically, the digital controller establishes a linear mapping relationship between the phase frequency change rate and the filter quality factor based on the group delay characteristics of the second-order resonant system.

[0066] Specifically, the filter quality factor is the preset bandwidth correction coefficient, master oscillation frequency, phase frequency change rate, and... The result of the product.

[0067] The stability margin coefficient is used to fine-tune the theoretical bandwidth by taking into account the sampling and holding delay and discretization error of the digital controller. When a more conservative coverage is required, i.e. when a wider bandwidth is needed, the value of the stability margin coefficient can be appropriately reduced.

[0068] The greater the rate of change of phase frequency, the sharper the line resonance, and the narrower the generated filter, i.e., the larger the filter quality factor; the smaller the rate of change of phase frequency, the flatter the line resonance, and the wider the generated filter, i.e., the smaller the filter quality factor.

[0069] To ensure the safety and determinism of the parameters executed subsequently, the digital controller needs to encapsulate the above calculation results into a standardized instruction set and perform boundary verification, namely, to generate and verify the frequency domain damping shaping instructions.

[0070] First, the main oscillation frequency, target damping resistance value, and filter quality factor are encapsulated as parameters, and the digital controller generates frequency domain damping shaping instructions. The frequency domain damping shaping command is: in, Indicates the main oscillation frequency; Indicates the target damping resistance value; This represents the filter quality factor.

[0071] Understandably, the main oscillation frequency, the target damping resistance value, and the filter quality factor define the damping center frequency, the damping strength, and the damping bandwidth, respectively.

[0072] Secondly, boundary checks are performed on the filter quality factor. Specifically, when the filter quality factor is greater than the preset upper limit, the filter quality factor is assigned to the upper limit; when the filter quality factor is less than the preset lower limit, the filter quality factor is assigned to the lower limit.

[0073] In this embodiment, the upper limit and lower limit of the quality factor are set to 20 and 0.5, respectively.

[0074] The purpose of checking the upper limit of the filter quality factor is to prevent the filter passband from being too narrow, which would cause the system to be too sensitive to frequency drift, and to prevent numerical instability caused by coefficient quantization errors during digital implementation. The purpose of checking the lower limit of the filter quality factor is to prevent the filter from degenerating into an all-pass characteristic and introducing too much low-frequency interference.

[0075] Finally, after the boundary check passes, the state transition occurs. The digital controller stores the frequency domain damping shaping instruction into the control register and switches the system state machine flag from "detect / calculate" to "ready" to prepare for the closed-loop operation phase of high-power charging. If the boundary check fails or abnormal parameters occur, a fault alarm is triggered and charging is prohibited.

[0076] At this point, the frequency domain damping shaping command is generated.

[0077] In step S003, during the closed-loop operation phase of high-power charging, a discretized filter is set according to the main oscillation frequency and the filter quality factor, and a damping soft-start strategy is introduced. The reference value of the basic DC voltage is extracted, and the corrected instruction is calculated by combining the target damping resistance value and the soft-start coefficient. Based on the corrected instruction, the hardware circuit is driven to suppress oscillation.

[0078] When the system enters the formal charging phase, the frequency domain damping shaping command is converted into a real-time continuous control law to drive the hardware circuit to suppress oscillations. The formal charging phase is the closed-loop operation phase of high-power charging.

[0079] To accurately execute the damping strategy corresponding to the calculated frequency-domain damping shaping command, the digital controller first needs to reconstruct a bandpass filter within the DSP digital signal processor or FPGA. The core requirement for the bandpass filter is that the gain at the center frequency must be strictly 1 (0dB) to ensure that the physical meaning of the target damping resistance value is not distorted by the gain of the filter itself.

[0080] Specifically, the digital controller reads the master oscillation frequency and filter quality factor from the frequency domain damping shaping instruction, and uses bilinear transformation or other discretization methods to convert the transfer function of the second-order normalized bandpass filter in the second-order linear time-invariant system into a difference equation or Z-transfer function in the discrete domain, thereby obtaining the discretized filter.

[0081] Among them, the bilinear transform is the Tustin transform; in the above process, the digital controller needs to ensure the accuracy of the discretization coefficient calculation so as to ensure that after discretizing the second-order bandpass prototype in the continuous domain, the discrete frequency domain amplitude-frequency gain at the center angular frequency of the filter is about 1 (0dB).

[0082] At the instant the system state machine flag is switched from "probe mode" to "run mode," if the calculated damping correction is directly superimposed on the voltage command, a step jump in the output signal may occur because the initial values ​​of the filter's internal state variables do not match the current signal. This step jump manifests as a voltage surge in the voltage loop, potentially triggering overvoltage protection. To eliminate this potential hazard, a fade-in damping soft-start strategy is introduced.

[0083] To implement the damped soft-start strategy, it is first necessary to define a time-varying frequency using a digital controller. Variable soft start coefficient .

[0084] The preset soft-start duration is used. The soft-start coefficient increases linearly from 0 to 1 within the soft-start duration. After the soft-start duration is exceeded, the soft-start coefficient remains constant at 1.

[0085] The bus current is acquired in real time using a digital controller, and the oscillation current in a specific frequency band is extracted using a discretization filter. The real-time damping feedback correction is calculated by combining the target damping resistance value and the soft-start coefficient. The real-time damping feedback correction is the product of the soft-start coefficient, the target damping resistance value, and the bus current.

[0086] It is understandable that the real-time damping feedback correction, soft-start coefficient, and bus current correspond to the same time. .

[0087] The damped soft-start strategy ensures that the virtual damping is "smoothly connected" to the system, avoiding the electrical shocks caused by hard switching.

[0088] The real-time damping feedback correction is introduced into the voltage control loop to synthesize the final drive command. Specifically, the BMS requests the reference value of the base DC voltage of the DC building power supply system. The difference between the reference value of the base DC voltage and the real-time damping feedback correction is used as the corrected command. The corrected command is sent to the voltage PI regulator to generate a PWM signal to drive the power semiconductor switch.

[0089] Understandably, the corrected command is sent to the voltage PI regulator to generate a PWM signal to drive the power semiconductor switch. That is, the corrected voltage control command is input into the PI voltage regulator for closed-loop regulation. The control signal output by the regulator generates PWM pulses, which are ultimately used to drive the power semiconductor switch to turn on and off, thereby precisely controlling the output voltage / current of the circuit and driving the hardware circuit to suppress oscillation.

[0090] At this point, the source-side power supply equipment can exhibit dual output impedance characteristics, specifically as follows: 1. DC and non-resonant frequency bands: Due to the blocking effect of filters, the oscillating current in specific frequency bands... It will be converted into a real-time damping feedback correction. The system output voltage strictly tracks the base DC voltage reference value. This exhibits characteristics of an ideal voltage source. This ensures that the charging voltage does not drop with the magnitude of the load current, maintaining high steady-state accuracy. The ideal voltage source characteristic is essentially a zero internal resistance characteristic.

[0091] 2. Resonant Frequency Band: Due to the passband effect of the filter, the real-time damping feedback correction is proportional to the oscillation current. The system output voltage fluctuates in the opposite direction to the oscillation current, exhibiting the characteristics of a damping source with a resistor corresponding to the target damping resistance value connected in series. This is equivalent to inserting a physical resistor into the resonant circuit, rapidly dissipating the oscillation energy and pulling the system poles back to the stable region of the left half-plane. The resonant frequency band is near the main oscillation frequency; the damping source characteristic is the high internal resistance characteristic.

[0092] Through the above process, a closed-loop control of the oscillation risk of DC building power supply system can be achieved through "sensing-decision-execution", which completely solves the stability problem caused by the uncertainty of feeder parameters.

[0093] This solves the problem of continuous oscillation of the bus voltage at the resonant frequency and enables the adaptive determination of the virtual resistance.

[0094] Based on the same inventive concept as the above method, this embodiment of the invention also provides a DC building power supply system, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any one of the above-described DC building power supply operation control methods.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A DC building power supply operation control method, characterized in that, The method includes the following steps: After constructing the basic voltage closed-loop detection environment, a wideband excitation signal is injected, the impedance spectrum of the feeder port is calculated and the peak value is located, the inherent impedance peak value of the feeder and the main oscillation frequency are determined, and a local linear fitting in the frequency domain is performed based on the main oscillation frequency to determine the phase frequency change rate. The phase frequency change rate is used to characterize the local group delay at the resonance point. Read the maximum requested charging power and the minimum allowed charging voltage of the battery, calculate the equivalent negative resistance limit of the load, calculate the target damping resistance value based on the load equivalent negative resistance limit and the peak value of the inherent impedance of the feeder, and calculate the filter quality factor based on the main oscillation frequency and the phase frequency change rate. The main oscillation frequency, the target damping resistance value and the filter quality factor are used to quantify the center frequency, intensity and bandwidth of the damping, respectively. Before the closed-loop operation stage of high-power charging, generate frequency domain damping shaping instructions. During the closed-loop operation phase of high-power charging, a discretized filter is set according to the main oscillation frequency and the filter quality factor. A damped soft-start strategy is introduced to extract the reference value of the basic DC voltage. Combined with the target damping resistance value and the soft-start coefficient, the corrected command is calculated. Based on the corrected command, the hardware circuit is driven to suppress oscillation.

2. The DC building power supply operation control method according to claim 1, characterized in that, The specific method for calculating the impedance spectrum of the feeder port is as follows: While injecting the wideband excitation signal, the voltage and current sequences of the source power supply equipment port are simultaneously acquired to obtain the voltage and current vectors in the frequency domain. The ratio of the voltage and current vectors in the frequency domain is recorded as the impedance spectrum of the feeder port in the frequency domain.

3. The DC building power supply operation control method according to claim 1, characterized in that, The specific method for determining the peak value of the inherent impedance of the feeder and the main oscillation frequency is as follows: The maximum value of the feeder port impedance magnitude corresponding to all frequencies in the frequency domain is denoted as the feeder inherent impedance peak value, and the frequency corresponding to the feeder inherent impedance peak value is denoted as the main oscillation frequency.

4. The DC building power supply operation control method according to claim 1, characterized in that, The specific method for determining the phase frequency change rate is as follows: Centered on the main oscillation frequency, a local frequency window of a preset width is selected. Data pairs corresponding to discrete frequency points within the local frequency window are extracted from the impedance phase spectrum and frequency vector. Straight line fitting is performed on all data pairs corresponding to discrete frequency points, and the absolute value of the slope of the fitted straight line is recorded as the phase frequency change rate.

5. The DC building power supply operation control method according to claim 1, characterized in that, The equivalent negative resistance limit of the load is the ratio of the square of the minimum charging voltage to the maximum requested charging power that completes the data validity verification.

6. The DC building power supply operation control method according to claim 1, characterized in that, The specific calculation method for the target damping resistance value is as follows: The product of the equivalent negative resistance limit of the load and the preset stability margin coefficient is denoted as the impedance safety boundary. The difference between the peak value of the inherent impedance of the feeder and the impedance safety boundary is calculated, and the maximum value of the result is denoted as the number 0. The product of the maximum value and the preset engineering correction coefficient is denoted as the target damping resistance value.

7. The DC building power supply operation control method according to claim 1, characterized in that, The filter quality factor is: a preset bandwidth correction coefficient, a master oscillation frequency, a phase frequency change rate, and... The product of the products, where, It represents pi (π).

8. The DC building power supply operation control method according to claim 1, characterized in that, The method for setting the discretization filter is as follows: Read the master oscillation frequency and filter quality factor, and convert the transfer function of the second-order normalized bandpass filter in the second-order linear time-invariant system into a difference equation or Z-transfer function in the discrete domain to obtain the discretized filter.

9. A DC building power supply operation control method according to claim 1, characterized in that, The proposed damped soft-start strategy extracts a baseline DC voltage reference value, combines it with the target damping resistance value and soft-start coefficient, and calculates the corrected command. The specific methods include: Define a time Variable soft start coefficient : Preset soft start duration. The soft start coefficient increases linearly from 0 to 1 within the soft start duration. After the soft start duration is exceeded, the soft start coefficient remains constant at 1. Real-time acquisition of bus current, and extraction of oscillation current in a specific frequency band through a discretization filter; The product of the soft-start coefficient, the target damping resistance value, and the bus current is recorded as the real-time damping feedback correction. Request the reference value of the base DC voltage of the DC building power supply system, and use the difference between the reference value of the base DC voltage and the real-time damping feedback correction as the corrected command.

10. A DC building power supply system, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the method as claimed in any one of claims 1-9.

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