Magnetic flux integral current measurement method based on chopping zero magnetic flux

Abstract

The invention discloses a magnetic flux integral current measurement method based on chopping zero magnetic flux, and relates to the technical field of current measurement, and the method comprises the steps: obtaining the zero offset of a detection resistor channel and a magnetic flux detection channel when the zero voltage of a compensation winding is compensated; each window collects bus voltage and records a window starting point; synchronously acquiring detection resistor voltage and magnetic flux detection voltage, calculating compensation current, and recursively updating compensation current integral quantity, magnetic flux estimator and two-stage recursion state quantity; constructing a feasible codeword set according to the two-stage recursion state quantity, and obtaining a final codeword according to window tail end forced closing, magnetic flux border-crossing recovery and predicted magnetic flux minimization judgment; determining a compensation voltage level according to the final code word and generating a gate timing sequence to drive a compensation winding; and at the end of the window, reconstructing the measured current based on the compensation current integral quantity endpoint difference, and updating the magnetic flux channel zero offset based on the magnetic flux estimator endpoint difference. Chopped wave compensation sequence closing and operation correction are realized through code word forced closing.

Description

Technical Field

[0001] This invention relates to the field of current measurement technology, and in particular to a flux integration current measurement method based on chopper zero flux. Background Technology

[0002] In the field of current measurement, engineering commonly employs methods such as shunt resistors, Hall effect sensors, current transformers, and zero-flux closed-loop systems to acquire current. Among these, chopper-based zero-flux methods typically utilize a compensation winding to establish a reverse magnetomotive force on the magnetic core. The induced voltage of the flux detection winding is integrated to form a flux representation. Then, the compensation voltage or current is modulated through a closed loop to maintain the core's operating point near zero flux. Combined with digital sampling and timing control, current measurement and signal output can be achieved under wide bandwidth and isolation conditions.

[0003] However, existing methods still have two limitations: First, if the switching timing or duty cycle is used as the current demodulation quantity, the device switching delay, bus voltage fluctuation and drive timing discretization will introduce equivalent modulation error, which will affect the demodulation consistency. Second, the flux integration link is sensitive to zero-point bias and low-frequency drift. The bias has a cumulative effect during time integration, which can easily lead to baseline drift of the flux characterization quantity, thereby increasing the complexity of calibration and long-term stable control. Summary of the Invention

[0004] In view of the aforementioned existing problems, the present invention is proposed.

[0005] Therefore, this invention provides a flux integration current measurement method based on chopper zero flux to solve the problems of duty cycle demodulation being easily affected by bus voltage fluctuations and switching delays, and the easy accumulation of zero-point bias drift in the flux integration link in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0007] This invention provides a flux integration current measurement method based on chopper zero flux, comprising: acquiring the zero-point bias of the detection resistor channel and the flux detection channel when no compensation voltage is applied to the compensation winding; acquiring the bus voltage in each detection window; recording the flux estimation starting point value and the compensation current integration starting point value of the detection window; synchronously acquiring the detection resistor voltage and the flux detection voltage; calculating the compensation current based on the zero-point bias and recursively updating the compensation current integral and the flux estimate; recursively updating the two-level recursive state quantities through the flux estimate; constructing a feasible codeword set based on the two-level recursive state quantities; selecting the final codeword according to the multi-layer judgment of forced closure at the end of the window, flux over-limit recovery, and predicted flux minimization; calculating the target compensation voltage level based on the final codeword; generating the gate timing drive compensation winding according to the codeword and sampling period segmented level rule; calculating the measured current based on the window endpoint differential reconstruction of the compensation current integral; and recursively deriving the flux detection channel bias correction amount based on the window endpoint differential of the flux estimate and updating the zero-point bias.

[0008] As a preferred embodiment of the flux integration current measurement method based on chopper zero flux described in this invention, the step of obtaining the zero-point bias of the detection resistance channel and the flux detection channel under the state where no compensation voltage is applied to the compensation winding includes controlling the driver of the compensation winding to enter a zero-level holding or off state, and after a continuous establishment time, sampling the detection resistance channel and the flux detection channel respectively to obtain the corresponding zero-point bias.

[0009] As a preferred embodiment of the flux integration current measurement method based on chopper zero flux described in this invention, the step of obtaining the corresponding zero-point bias includes continuously sampling the output of the detection resistor channel and the output of the flux detection channel during the zero-level holding or off state, and averaging the respective sampled values ​​to obtain the zero-point bias of the detection resistor channel and the zero-point bias of the flux detection channel.

[0010] As a preferred embodiment of the flux integration current measurement method based on chopper zero flux described in this invention, the step of acquiring the bus voltage in each detection window includes: continuously sampling the bus voltage sampling channel at the beginning of the detection window, accumulating the bus voltage sampling values, obtaining the accumulated value, recording the number of samplings, and using the ratio of the accumulated value to the number of samplings as the representative value of the bus voltage in this detection window.

[0011] As a preferred embodiment of the flux integration current measurement method based on chopper zero flux described in this invention, the specific steps of calculating the compensation current based on zero-point bias and recursively updating the integral amount of the compensation current and the flux estimate are as follows: reading the zero-point bias of the detection resistor channel, performing bias subtraction on the sampled value of the detection resistor voltage to obtain the detection resistor voltage value after bias subtraction; converting the detection resistor voltage value after bias subtraction according to the resistance value of the detection resistor to obtain the compensation current value of the current sampling period; using a fixed sampling period as the time increment, accumulating the compensation current value of the current sampling period into the compensation current integral accumulator and the flux accumulator in a discrete integration manner to obtain the updated integral amount of the compensation current and the updated flux estimate.

[0012] As a preferred embodiment of the flux integration current measurement method based on chopper zero flux described in this invention, the step of recursively updating the two-level recursive state quantities through flux estimation includes: setting a first state quantity and a second state quantity; initializing the first state quantity and the second state quantity; accumulating the current flux estimation quantity into the first state quantity to obtain a new first state quantity; and accumulating the updated first state quantity into the second state quantity to obtain a new second state quantity.

[0013] As a preferred embodiment of the flux integration current measurement method based on chopper zero flux described in this invention, the step of constructing a feasible codeword set based on two-level recursive state variables includes: establishing a codeword candidate set as a fixed set; setting candidate codewords according to a second state variable; for each codeword in the codeword set, using the sum of the codeword and the current codeword accumulation as the updated codeword accumulation; and constructing a feasible codeword set through constraints. The constraints include window-based constraints and remaining closable constraints. The window-based constraints stipulate that the absolute value of the updated codeword accumulation does not exceed the upper limit threshold of the codeword accumulation in this window. The remaining closable constraints are implemented using a closing criterion.

[0014] As a preferred embodiment of the flux integration current measurement method based on chopper zero flux described in this invention, the step of selecting the final codeword by multi-layer judgment based on forced closure of the window end, flux boundary recovery, and prediction flux minimization specifically involves the following steps: when the detection window is at the end and the remaining sampling count satisfies the forced closure judgment, the codeword that closes the cumulative amount of the codeword at the end of the window is selected as the final codeword; when the flux estimate reaches the flux linear upper limit threshold, the flux boundary recovery judgment is performed, and the codeword that causes the flux estimate to change in the regression direction is selected as the final codeword; when the forced closure of the window end and the flux boundary recovery judgment are not triggered, the prediction flux minimization judgment is performed, and each codeword in the feasible codeword set is further predicted for flux, and the codeword that minimizes the predicted flux amplitude is selected as the final codeword.

[0015] As a preferred embodiment of the flux integration current measurement method based on chopper zero flux described in this invention, the steps of calculating the target compensation voltage level based on the final codeword and generating the gate timing drive compensation winding according to the codeword and sampling period segmented level rules are as follows: mapping the final codeword to the discrete voltage level range allowed by the compensation drive, and calculating the target compensation voltage level for the current sampling period based on the representative value of the bus voltage of the current detection window; generating the gate timing according to the final codeword and sampling period segmented level application rules and applying the compensation voltage; the segmented level is a segmentation method in which a fixed full level is applied to the first half of the half-cycle and a zero level is applied to the half-cycle for the half-level codeword.

[0016] As a preferred embodiment of the flux integration current measurement method based on chopper zero flux described in this invention, the steps of calculating the measured current based on the window endpoint differential reconstruction of the compensation current integral and reversing the flux detection channel bias correction amount and updating the zero-point bias based on the window endpoint differential of the flux estimate are as follows: The endpoint differential is performed on the compensation current integral endpoint value to obtain the compensation current integral increment, and the ratio of the compensation current integral increment to the detection window duration is used as the window value; the window value is converted into the measured current according to the ratio of the number of turns of the compensation winding to the equivalent number of turns of the measured conductor; the endpoint differential is performed on the flux estimate endpoint value to obtain the flux estimate increment; the flux detection channel bias correction amount is calculated based on the flux estimate increment, and the flux detection channel bias correction amount is added to the current flux detection channel zero-point bias to obtain the updated flux detection channel zero-point bias.

[0017] The beneficial effects of this invention are as follows: By generating codewords based on two-level recursive state variables and combining the codeword accumulation and remaining sampling times for minimization and hierarchical determination, and by forcibly closing the window end, a chopper compensation sequence that can be closed within the window scale is formed and codeword accumulation drift is suppressed; by using the window endpoint differential of the compensation current integral to reconstruct the measured current and using the window endpoint differential of the magnetic flux estimate to deduce the magnetic flux detection channel bias correction amount to update the zero-point bias, the output current is demodulated independently of the duty cycle and the zero-point bias is self-corrected during operation. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. 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.

[0019] Figure 1 This is a flowchart of a flux integration current measurement method based on chopper zero flux.

[0020] Figure 2The flowchart for zero-point offset acquisition and detection window initialization.

[0021] Figure 3 This is a flowchart of sampling and state recursion.

[0022] Figure 4 This is a flowchart for codeword-driven and endpoint differential. Detailed Implementation

[0023] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0024] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0025] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0026] Reference Figures 1-4 This is one embodiment of the present invention, which provides a flux integration current measurement method based on chopper zero flux, comprising the following steps:

[0027] S1. Obtain the zero-point bias of the detection resistor channel and the magnetic flux detection channel when the compensation winding is not subjected to compensation voltage. Obtain the bus voltage in each detection window and record the magnetic flux estimation starting value and the compensation current integration starting value of the detection window.

[0028] The compensation winding is energized by a bidirectional chopper driver; the resistance detection channel and the flux detection channel are both connected to the same processor's analog-to-digital conversion interface; the sampling clock is generated by a timer.

[0029] To ensure the compensation winding is in an electrical state without applied compensation voltage, the processor outputs a disable command to the compensation drive circuit, causing the compensation drive to enter a zero-level holding state, maintaining equipotential at both ends of the compensation winding, and the compensation winding is not subjected to external compensation voltage. After outputting the disable command, a setup time is waited to eliminate the influence of switch-off transients and residual charging and discharging at the sampling front end on the sampling.

[0030] It should be noted that the setup time is determined by collecting voltage data from the detection resistor channel and the magnetic flux detection channel after the compensation drive switches to zero level hold, calculating the difference between two adjacent sample values, and determining the setup time as the time from the switching moment to the current moment when the difference between the two channels is zero for a fixed number of consecutive sampling periods (e.g., 3).

[0031] To obtain the zero-point bias of the detection resistor channel, specifically, during the period when the disable command remains valid, the voltage across the detection resistor is continuously sampled at a fixed sampling period (e.g., 10μs), and the number of samplings is set to a fixed value (e.g., 256 times). The sampled digital quantities are accumulated to obtain the accumulated value, and the number of samplings is recorded. The ratio of the accumulated value to the number of samplings is used as the zero-point bias of the detection resistor channel.

[0032] To obtain the zero-point bias of the magnetic flux detection channel, specifically, during the period when the disable command remains valid, the magnetic flux detection voltage is continuously sampled according to a fixed sampling period. The number of samplings is set to a fixed value. The various digital quantities obtained by sampling are accumulated to obtain the accumulated value, and the number of samplings is recorded. The ratio of the accumulated value to the number of samplings is used as the zero-point bias of the magnetic flux detection channel.

[0033] Configure a timer to generate a periodic trigger signal, with the trigger period set to the sampling period. The trigger signal simultaneously triggers the analog-to-digital conversion of the detection resistance channel and the magnetic flux detection channel, thereby forming synchronous sampling. Set the detection window length to the sampling period count value and establish a window counter. The detection window counter increments once after each sampling period processing. When the detection window counter reaches the detection window length, the detection window is determined to be closed.

[0034] When the detection window counter is set to zero and the detection window is determined to be at its start, the bus voltage sampling channel is continuously sampled, the bus voltage sampled values ​​are accumulated, the accumulated value is obtained, and the number of samplings is recorded. The ratio of the accumulated value to the number of samplings is used as the representative value of the bus voltage in this detection window, and the representative value of the bus voltage is fixed as the bus voltage in this detection window until the detection window ends.

[0035] When the detection window begins to determine that the condition is met, the flux accumulator and the current integral accumulator are set to zero respectively, the code word accumulation is set to zero, and the detection window counter is cleared.

[0036] S2. Synchronously acquire and detect the resistor voltage and magnetic flux detection voltage, calculate the compensation current based on the zero-point bias, and recursively update the integral quantity of the compensation current and the magnetic flux estimate. The two-level recursive state quantities are then updated through the magnetic flux estimate.

[0037] Initiate analog-to-digital conversion for the resistance detection channel and the flux detection channel. After the analog-to-digital conversion is completed, read the voltage sample values ​​of the resistance detection channel and the flux detection channel respectively. Read the zero-point bias of the resistance detection channel, subtract the bias from the voltage sample value of the resistance detection channel, and obtain the resistance voltage value after bias subtraction. Convert the resistance voltage value after bias subtraction according to the resistance value of the resistance detection channel to obtain the compensation current value for this sampling period.

[0038] The integral quantity of the compensation current is updated recursively. Specifically, the value of the compensation current integral accumulator is read, and the compensation current value of the current sampling period is accumulated into the compensation current integral accumulator in a discrete integration manner with a fixed sampling period as the time increment to obtain the updated integral quantity of the compensation current.

[0039] The zero-point bias of the flux detection channel is read from the storage area. The sampled value of the flux detection voltage is deducted by bias to obtain the flux detection voltage value after bias deduction. The value of the flux accumulator is read. With a fixed sampling period as the time increment, the flux detection voltage value after bias deduction is accumulated into the flux accumulator in a discrete integration manner to obtain the updated flux estimate.

[0040] To form a discrete feedback state for codeword decision-making, a two-level recursive state variable is established, which is updated once in each sampling period. Specifically, a first state variable and a second state variable are set. At the beginning of the detection window, the first state variable and the second state variable are initialized. After obtaining the updated magnetic flux estimate, the current magnetic flux estimate is added to the first state variable to obtain a new first state variable. The updated first state variable is added to the second state variable to obtain a new second state variable.

[0041] S3. Construct a set of feasible codewords based on the two-level recursive state variables, and select the final codewords by multi-level judgment based on forced closure of the window end, magnetic flux over-limit recovery, and prediction of magnetic flux minimization.

[0042] Read the second state quantity updated in the current sampling period, read the current magnetic flux estimate, read the codeword accumulation, detection window count, and detection window length within the detection window; take the difference between the detection window length and the window count as the remaining sampling times for the window; establish a fixed set of codeword candidate set {-2, -1, 0, +1, +2}, and establish an empty set of feasible codewords.

[0043] Candidate codewords are set based on the second state variable. Specifically, it is determined whether the second state variable is 0. If it is 0, the candidate codeword is directly set to 0. If it is not 0, the sign of the second state variable is determined and its absolute value is taken as the amplitude. The amplitude is compared with the full amplitude threshold of the state variable. When the amplitude is not less than the full amplitude threshold of the state variable, the candidate codeword is set to +2 or -2 according to the sign of the second state variable. When the amplitude is less than the full amplitude threshold of the state variable, it is compared with the half amplitude threshold of the state variable. When the amplitude is not less than the half amplitude threshold of the state variable, the candidate codeword is set to +1 or -1 according to the sign of the second state variable. When the amplitude is less than the half amplitude threshold of the state variable, the candidate codeword is set to 0. The codeword set is then obtained.

[0044] It should be noted that, under the condition that the compensation drive is kept at zero level and there is no current in the external conductor being measured, the continuous operating state quantity is used for recursion, the maximum absolute value of the second state quantity is recorded, and the maximum absolute value of the second state quantity is used as the half-amplitude threshold of the state quantity; then twice the half-amplitude threshold of the state quantity is used as the full-amplitude threshold of the state quantity, and the value range is greater than zero.

[0045] For each codeword in the codeword set, the sum of the codeword and the current codeword accumulation is used as the updated codeword accumulation. A feasible codeword set is obtained through constraint construction. Specifically, the constraints include in-window constraints and residual closure constraints. The in-window constraint states that the absolute value of the updated codeword accumulation does not exceed the upper limit threshold of the codeword accumulation in this window. The residual closure constraint states that the updated codeword accumulation has the possibility of closing to zero within the remaining sampling count minus one sampling in the remaining window. The residual closure constraint is implemented using a closure criterion, expressed as:

[0046] ;

[0047] in, Indicates the codeword to be verified. This indicates the current cumulative amount of codewords. This indicates the number of samples remaining.

[0048] It should be noted that the upper limit threshold for codeword accumulation is calculated by reading the upper limit of the linear working magnetic induction intensity of the magnetic core material and the effective cross-sectional area of ​​the magnetic core, and calculating the upper limit value of the linear magnetic flux. At the same time, the representative value of the bus voltage, the number of turns of the compensation winding, and the sampling period are read in this window, and the magnetic flux step size of a single sampling period under the action of the maximum codeword is calculated. The ratio of the upper limit value of the linear magnetic flux to the magnetic flux step size of a single period is rounded down as the upper limit threshold for codeword accumulation in this window, and the value range is greater than zero.

[0049] If the feasible codeword set is empty, the codeword will be fixed as AND. The codeword with the opposite sign and the largest amplitude.

[0050] Multi-level judgment and selection are performed. Specifically, a three-level judgment order is adopted: the first level is the judgment of forced closure at the end of the window, the second level is the judgment of magnetic flux over-limit and recovery, and the third level is the judgment of minimization based on magnetic flux prediction.

[0051] The window end is forcibly closed when When the value equals 1, the codeword is directly selected as the opposite of the current codeword's accumulated value, and the current codeword is output as the final codeword.

[0052] The magnetic flux out-of-bounds and recovery determination is as follows: when the absolute value of the current magnetic flux estimate reaches or exceeds the upper limit threshold of the magnetic flux linearity, the feasible codeword set is shrunk to a subset of the maximum amplitude codeword and the zero codeword, and a codeword with the opposite sign to the magnetic flux estimate is selected from the subset (if the magnetic flux is positive, a negative codeword is selected, and if the magnetic flux is negative, a positive codeword is selected); when the magnetic flux estimate is within the recovery threshold, this branch is exited and the third-level determination is entered.

[0053] The selection criterion based on minimizing the predicted magnetic flux is as follows: for each codeword in the feasible codeword set, calculate the estimated predicted magnetic flux value for the next sampling period, and select the codeword with the smallest absolute value of the predicted magnetic flux as the final codeword; the predicted magnetic flux value is calculated according to the discrete relationship between the compensation winding voltage and the magnetic flux, and the expression is:

[0054] ;

[0055] in, This represents the current magnetic flux estimate. Indicates the application of codewords The predicted magnetic flux estimate for the next sampling period is obtained after corresponding compensation voltage level. This represents the bus voltage value within this detection window. Indicates the number of turns in the compensation winding. Indicates the sampling period.

[0056] It should be noted that the upper limit threshold for magnetic flux linearity is calculated during the design phase based on the upper limit of the linear working magnetic induction intensity given by the core material and the effective cross-sectional area of ​​the core, and its value range is greater than zero. The recovery threshold is calculated at the beginning of each detection window by obtaining the representative value of the bus voltage of the detection window and combining it with the number of turns of the compensation winding and the sampling period to calculate the single sampling period magnetic flux step size corresponding to the maximum codeword. The result of subtracting two single sampling period magnetic flux step sizes from the upper limit threshold for magnetic flux linearity is used as the recovery threshold for the detection window, and its value range is greater than zero.

[0057] If multiple codewords correspond to the same absolute value of predicted flux, the codeword that makes the absolute value of the updated codeword accumulation smaller is selected from these codewords as the final codeword; the codeword accumulation in the window is updated with the final codeword and the detection window count is incremented once; when the detection window count reaches the detection window length, the window end flag is triggered.

[0058] S4. Calculate the target compensation voltage level based on the final codeword, and generate the gate timing drive compensation winding according to the codeword and sampling period segment level rules.

[0059] Read the final codeword of this sampling period and the representative value of the bus voltage in this detection window, and calculate the target compensation voltage level for this sampling period. The expression is:

[0060] ;

[0061] in, This indicates the target compensation voltage.

[0062] Gate timing is generated and compensation voltage is applied according to the segmented level application rules based on the final codeword and sampling period. Specifically, when the final codeword is +2, the compensation drive circuit is controlled to output a positive bus voltage throughout the entire sampling period, keeping the compensation winding at a positive full level until the end of the sampling period; when the final codeword is -2, the compensation drive circuit is controlled to output a reverse bus voltage throughout the entire sampling period, keeping the compensation winding at a reverse full level until the end of the sampling period; when the final codeword is 0, the compensation drive circuit is controlled to output a zero level throughout the entire sampling period, keeping the compensation winding at the same potential until the end of the sampling period. End; When the final codeword is +1, the processor divides the sampling period into a first half-cycle and a second half-cycle. During the first half-cycle, it controls the compensation drive circuit to output a positive bus voltage, and during the second half-cycle, it controls the compensation drive circuit to output a zero level, thus forming a positive half-level; When the final codeword is -1, the sampling period is divided into a first half-cycle and a second half-cycle. During the first half-cycle, it controls the compensation drive circuit to output a reverse bus voltage, and during the second half-cycle, it controls the compensation drive circuit to output a zero level, thus forming a reverse half-level; During any level switching, a fixed dead time is inserted between the drive signals of the complementary switching devices.

[0063] The fixed-segmentation method refers to applying a full level to the first half of the cycle and a zero level to the second half of the cycle for the half-level codeword. The segmentation ratio is fixed at 1:1 and does not change with the current magnitude.

[0064] It should be noted that the dead time is the sum of the maximum turn-off propagation delay and the maximum turn-off time given in the datasheet of the power switching device used.

[0065] Read the accumulated codeword amount within the detection window, add the codewords of the current sampling period to the accumulated codeword amount using integer addition, and obtain the updated accumulated codeword amount; read the detection window counter and increment it once to obtain the updated detection window count; when the detection window count reaches the detection window length, set the window end flag, and clear the detection window count to zero before the start of the next period, while also clearing the accumulated codeword amount to zero.

[0066] S5. Calculate the measured current based on the window endpoint differential reconstruction of the compensation current integral, and deduce the magnetic flux detection channel bias correction based on the window endpoint differential of the magnetic flux estimate and update the zero-point bias.

[0067] Read the value of the current compensation current integral accumulator and latch it as the compensation current integral endpoint value at the end of the detection window; read the value of the current magnetic flux estimate accumulator and latch it as the magnetic flux estimate endpoint value at the end of the detection window; read the compensation current integral endpoint value and magnetic flux estimate endpoint value recorded at the beginning of this detection window as the starting endpoint value of the detection window.

[0068] Endpoint differential is performed on the integral endpoint value of the compensation current to obtain the integral increment of the compensation current within this window; the ratio of the integral increment of the compensation current to the duration of the detection window (the product of the detection window length and the sampling period) is used as the window value of the compensation current for this detection window. The window value of the compensation current is converted into the output current of the measured current according to the ratio of the number of turns of the compensation winding to the equivalent number of turns of the measured conductor, as expressed by:

[0069] ;

[0070] in, Indicates the measured current. Indicates the equivalent number of turns of the conductor being tested. This represents the end value of the detection window for the integral of the compensation current. This represents the starting and ending point values ​​of the window for the integral of the compensation current. Indicates the length of the detection window.

[0071] Perform endpoint differencing on the flux estimation endpoint values ​​to obtain the flux estimation increment within the current detection window. Calculate the flux detection channel offset correction based on the flux estimation increment, and add the flux detection channel offset correction to the current flux detection channel zero-point offset to obtain the updated flux detection channel zero-point offset. The expression is:

[0072] ;

[0073] in, This indicates that the magnetic flux detection channel is zero-point biased. Indicates the number of turns in the flux detection winding. This represents the estimated endpoint value of the magnetic flux at the end of the detection window. This represents the estimated endpoint value of the magnetic flux at the starting point of the detection window.

[0074] Write the end value of the compensation current integration endpoint of the detection window to the starting point of the compensation current integration of the next detection window, and write the end value of the magnetic flux estimation endpoint of the detection window to the starting point of the magnetic flux estimation of the next detection window; clear the detection window counter and clear the accumulated amount of the code word in the window, and enter the first sampling cycle processing flow of the next window.

[0075] In summary, this invention generates codewords based on two-level recursive state variables and performs a minimum hierarchical determination by combining the codeword accumulation and the remaining sampling count, while forcibly closing the window ends. This achieves the formation of a closable chopper compensation sequence within the window scale and suppresses codeword accumulation drift. Furthermore, by using the window endpoint differential of the compensation current integral to reconstruct the measured current and using the window endpoint differential of the magnetic flux estimate to deduce the magnetic flux detection channel bias correction amount to update the zero-point bias, this invention achieves output current demodulation independent of duty cycle and self-correction of the zero-point bias during operation.

[0076] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for measuring flux integration current based on chopper zero flux, characterized in that: include, The zero-point bias of the detection resistor channel and the magnetic flux detection channel is obtained when the compensation winding is not subjected to compensation voltage. The bus voltage is obtained in each detection window, and the magnetic flux estimation starting value and the compensation current integration starting value of the detection window are recorded. The voltage of the detection resistor and the voltage of the magnetic flux are collected synchronously. The compensation current is calculated based on the zero-point bias and the integral quantity of the compensation current and the magnetic flux estimate are updated recursively. The two-level recursive state quantities are updated recursively through the magnetic flux estimate. A feasible codeword set is constructed based on two-level recursive state variables, and the final codeword is selected by multi-level judgment based on forced closure of the window end, magnetic flux over-limit recovery, and prediction of magnetic flux minimization. Calculate the target compensation voltage level based on the final codeword, and generate the gate timing drive compensation winding according to the codeword and sampling period segment level rules; The measured current is calculated by differential reconstruction of the window endpoints based on the integral of the compensation current, and the bias correction of the magnetic flux detection channel is derived from the differential of the window endpoints based on the magnetic flux estimate and the zero-point bias is updated.

2. The flux integration current measurement method based on chopper zero flux as described in claim 1, characterized in that: The step of obtaining the zero-point bias of the detection resistance channel and the magnetic flux detection channel when no compensation voltage is applied to the compensation winding includes controlling the driver of the compensation winding to enter a zero-level holding or off state, and after a certain period of time, sampling the detection resistance channel and the magnetic flux detection channel respectively to obtain the corresponding zero-point bias.

3. The flux integration current measurement method based on chopper zero flux as described in claim 2, characterized in that: The acquisition of the corresponding zero-point bias includes continuously sampling the output of the detection resistor channel and the output of the magnetic flux detection channel during the zero-level holding or off state, and averaging the respective sampled values ​​to acquire the zero-point bias of the detection resistor channel and the zero-point bias of the magnetic flux detection channel.

4. The flux integration current measurement method based on chopper zero flux as described in claim 3, characterized in that: The step of acquiring the bus voltage in each detection window includes continuously sampling the bus voltage sampling channel at the beginning of the detection window, accumulating the bus voltage sample values, obtaining the accumulated value, recording the number of samplings, and using the ratio of the accumulated value to the number of samplings as the representative value of the bus voltage in this detection window.

5. The flux integration current measurement method based on chopper zero flux as described in claim 4, characterized in that: The specific steps for calculating the compensation current based on zero-point bias and recursively updating the integral of the compensation current and the magnetic flux estimate are as follows: Read the zero-point bias of the detection resistor channel, subtract the bias from the sampled voltage value of the detection resistor, and obtain the voltage value of the detection resistor after bias subtraction; The voltage value of the detection resistor after bias subtraction is converted according to the resistance value of the detection resistor to obtain the compensation current value for this sampling period. Using a fixed sampling period as the time increment, the compensation current value of the current sampling period is accumulated into the compensation current integral accumulator and the magnetic flux accumulator in a discrete integration manner to obtain the updated compensation current integral and the updated magnetic flux estimate.

6. The flux integration current measurement method based on chopper zero flux as described in claim 5, characterized in that: The method of recursively updating the two-level recursive state quantities through magnetic flux estimation includes setting a first state quantity and a second state quantity, and initializing the first state quantity and the second state quantity. The current magnetic flux estimate is added to the first state quantity to obtain a new first state quantity; The updated first state value is added to the second state value to obtain the new second state value.

7. The flux integration current measurement method based on chopper zero flux as described in claim 6, characterized in that: The construction of a feasible codeword set based on two-level recursive state variables includes establishing a fixed set of codeword candidate sets. Candidate codewords are set according to the second state variable. For each codeword in the codeword set, the sum of the codeword and the current codeword accumulation is used as the updated codeword accumulation. By constructing under constraints, a set of feasible codewords can be obtained; The constraints include in-window constraints and remaining closable constraints; The window constraint is that the absolute value of the updated codeword accumulation does not exceed the upper limit threshold of the codeword accumulation in this window. The remaining closable constraints are implemented using a closure criterion.

8. The flux integration current measurement method based on chopper zero flux as described in claim 7, characterized in that: The specific steps for selecting the final codeword using multi-layered judgment based on forced closure of the window end, magnetic flux boundary recovery, and minimization of predicted magnetic flux are as follows: When the detection window is at the end and the remaining number of samplings meets the forced closure judgment, the codeword that closes the codeword accumulation at the end of the window is selected as the final codeword. When the flux estimate reaches the upper limit threshold of flux linearity, a flux out-of-bounds recovery judgment is performed, and the codeword that makes the flux estimate change in the regression direction is selected as the final codeword. Without triggering the forced closure of the window end and the magnetic flux out-of-bounds recovery judgment, the predicted magnetic flux minimization judgment is performed, and the next magnetic flux prediction is performed on each codeword in the feasible codeword set, and the codeword that minimizes the predicted magnetic flux amplitude is selected as the final codeword.

9. The flux integration current measurement method based on chopper zero flux as described in claim 8, characterized in that: The specific steps for calculating the target compensation voltage level based on the final codeword and generating the gate timing drive compensation winding according to the codeword and sampling period segment level rules are as follows: The final codeword is mapped to the discrete voltage level range allowed by the compensation drive, and the target compensation voltage level for this sampling period is calculated based on the representative value of the bus voltage in this detection window. Gate timing is generated according to the final codeword and sampling period, and compensation voltage is applied based on the segmented level application rules. The fixed-segmentation method refers to a segmentation method in which a fixed full level is applied to the first half of the cycle and a zero level is applied to the second half of the cycle for half-level codewords.

10. The flux integration current measurement method based on chopper zero flux as described in claim 9, characterized in that: The process involves calculating the measured current using differential reconstruction at the window endpoints based on the integral of the compensated current, and then deriving the magnetic flux detection channel bias correction and updating the zero-point bias based on the differential calculation at the window endpoints of the magnetic flux estimate. The specific steps are as follows: Endpoint differential is performed on the endpoint value of the compensation current integral to obtain the compensation current integral increment, and the ratio of the compensation current integral increment to the detection window duration is used as the window value. The window value is converted into the measured current according to the ratio of the number of turns of the compensation winding to the equivalent number of turns of the conductor being measured. Perform endpoint difference on the flux estimation endpoint value to obtain the flux estimation increment. Calculate the flux detection channel offset correction based on the flux estimation increment and add the flux detection channel offset correction to the current flux detection channel zero offset to obtain the updated flux detection channel zero offset.

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