Adaptive compensation control method and system for direct current interference current

Abstract

The application discloses a kind of self-adapting compensation control method and system of direct current interference current, through successively connected single-phase PWM rectifier circuit, double active bridge conversion circuit and full-bridge circuit, gather grid voltage and current, rectification and isolation voltage, tube ground potential and output voltage.Based on output voltage, determine the target voltage of rectification and isolation link according to preset rule;Using phase-locked loop to extract grid phase, combined with alternating current and rectification voltage, generate driving signal through rectification control model, regulate and control PWM rectification output;According to rectification voltage and isolation voltage, calculate phase shift angle through isolation control model, drive double active bridge to realize high-frequency magnetic energy transmission, stabilize isolation voltage;Compare measured tube ground potential with target value, generate full-bridge driving signal through potential control model, adjust output current, implement reverse compensation or active absorption on stray current.The application improves the compensation capability of cathodic protection system under complex stray current interference.

Description

Technical Field

[0001] This invention relates to the field of cathodic protection for oil and gas pipelines, and in particular to an adaptive compensation control method and system for DC interference current. Background Technology

[0002] In cathodic protection systems for oil and gas pipelines, stray currents such as DC interference currents can cause the pipeline-to-ground potential to deviate from the safe range, threatening pipeline safety. Because DC interference currents are characterized by high amplitude, wide range, and drastic dynamic changes, real-time and precise adjustment of the pipeline-to-ground potential is necessary. This requires the compensation system to have a wide range of stray current compensation or absorption capabilities and a fast-response control mechanism to stabilize the output compensation current. To address these challenges, a multi-stage power electronic conversion architecture is needed to achieve reliable stabilization of the pipeline-to-ground potential under complex operating conditions.

[0003] In one existing technology, a power frequency transformer is used to reduce the grid voltage to the required level, and the DC power is obtained through diode uncontrolled rectification. The output voltage amplitude is then adjusted by a thyristor phase-controlled voltage regulation circuit. In the detection stage, an analog voltmeter monitors the tube-to-ground potential, and a mechanical potentiometer sets a reference value. When a deviation is detected, an analog comparator triggers a thyristor phase-shift control circuit to adjust the conduction angle and change the output current, aiming to maintain the tube-to-ground potential within the set range. This existing technology, which uses a power frequency transformer for voltage reduction, diode rectification, and thyristor phase-controlled voltage regulation for energy conversion and regulation, results in slow system response, low power factor, severe harmonic pollution, and insufficient control accuracy.

[0004] Therefore, this existing technology cannot achieve precise reverse compensation or active absorption of strong DC interference current with huge intensity fluctuations, and it is difficult to effectively improve the compensation capability of the cathodic protection system. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an adaptive compensation control method and system for DC interference current, which addresses the shortcomings of the existing technology, and enables precise reverse compensation or active absorption of strong DC interference current with huge intensity fluctuations, thereby improving the compensation capability of the cathodic protection system.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: an adaptive compensation control method for DC interference current, comprising the following steps:

[0007] A single-phase PWM rectifier circuit, a dual active bridge converter circuit, and a full-bridge circuit are connected in sequence. The single-phase PWM rectifier circuit is connected to the power grid, and the full-bridge circuit is connected to the reference electrode and auxiliary anode located near the pipeline. The single-phase AC voltage and AC current of the power grid, the real-time rectified voltage, the real-time isolation voltage, the real-time pipeline ground potential, and the output voltage of the full-bridge circuit are collected.

[0008] Based on the output voltage of the full-bridge circuit, determine the target isolation voltage of the dual active bridge converter circuit and the target rectified voltage of the single-phase PWM rectifier circuit; perform phase-locked loop phase extraction on the single-phase AC voltage of the power grid to obtain the power grid phase;

[0009] Based on the grid phase, the AC current, the real-time rectified voltage, and the target rectified voltage, a switching transistor drive sequence is generated; based on the real-time isolation voltage and the target isolation voltage, a phase shift angle is calculated and a phase shift pulse signal is generated; a potential control quantity is calculated using the real-time transistor ground potential and the preset target transistor ground potential, and a full-bridge drive signal is generated based on the potential control quantity.

[0010] The single-phase PWM rectifier circuit is controlled by the switching transistor driving sequence to control the bridge arm on / off timing, output rectified voltage, and use the rectified voltage as the input voltage of the dual active bridge converter circuit.

[0011] The switching timing of the primary and secondary arms of the dual active bridge converter circuit is controlled according to the phase-shifting pulse signal. Magnetic energy is transferred using a high-frequency transformer to adjust and stabilize the isolation voltage output by the dual active bridge converter circuit. This isolation voltage is then used as the input voltage of the full-bridge circuit.

[0012] The operating mode of the full-bridge circuit is controlled by the full-bridge drive signal. The output current is controlled by adjusting the output voltage of the full-bridge circuit to perform reverse compensation or active absorption of stray current, so that the tube ground potential is stabilized within the preset tube ground potential safety range.

[0013] The target isolation voltage expression for the dual active bridge converter circuit is:

[0014] ;

[0015] in, Indicates the target isolation voltage. , and These represent the preset first target isolation voltage, second target isolation voltage, and third target isolation voltage, respectively. o U represents the output voltage of the full-bridge circuit. o1 and U o2 These represent the preset first output voltage threshold and the second output voltage threshold, respectively.

[0016] The expression for the target rectified voltage of a single-phase PWM rectifier circuit is:

[0017] ;

[0018] in, Indicates the target rectified voltage. , and These represent the preset first target rectified voltage, second target rectified voltage, and third rectified isolation voltage, respectively. U DAB U represents the real-time isolation voltage. DAB1 and U DAB2 These represent the preset first isolation voltage threshold and the second isolation voltage threshold, respectively.

[0019] The switching transistor driving sequence is obtained by comparing a modulation wave signal with a triangular carrier signal. The expression for the modulation wave signal is:

[0020] ;

[0021] in, Indicates the reference alternating current. U represents the target rectified voltage. dc Indicates the real-time rectified voltage, i s U represents alternating current, ωt represents the phase of the power grid, and U represents the phase of the power grid. s Indicates the single-phase AC voltage of the power grid. Indicates the initial modulation signal. Represents the modulated wave signal, k pU1 and k pI1 These are the preset proportional coefficients for the rectified voltage loop and the rectified current loop, k. iU1 and k iI1 These are the preset integral coefficients of the rectified voltage loop and the rectified current loop, respectively, and s represents the Laplace operator.

[0022] The formula for calculating the phase shift angle is:

[0023] ;

[0024] in, U represents the target isolation voltage. DAB Indicates the real-time isolation voltage. k represents the phase shift angle. pU2 and k iU2 These are the preset isolation voltage loop proportional coefficient and rectifier voltage loop integral coefficient, respectively, and s represents the Laplace operator.

[0025] The formula for calculating the potential control quantity is:

[0026] ;

[0027] Among them, e ps For the pipe-to-ground potential deviation, U * ps U is the preset target pipe-to-ground potential. ps For real-time pipe-to-ground potential, G NICZ is the preset negative impedance equivalent admittance coefficient. NIC The preset negative impedance parameters, For the compensation current reference value, u ps k is the output voltage control quantity of the full-bridge bridge, i.e., the potential control quantity. pps k is the preset proportional gain coefficient. ips Here, is the preset integral gain coefficient, and s represents the Laplace operator.

[0028] As an inventive concept, the present invention also provides an adaptive compensation control method for DC interference current, which includes the following steps:

[0029] A single-phase PWM rectifier circuit, a dual active bridge converter circuit, and a full-bridge circuit are connected in sequence. The single-phase PWM rectifier circuit is connected to the power grid, and the full-bridge circuit is connected to the reference electrode and auxiliary anode located near the pipeline. The single-phase AC voltage of the power grid is collected.

[0030] Phase-locked loop (PLL) phase extraction is performed on the single-phase AC voltage of the power grid to obtain the power grid phase;

[0031] A switching transistor drive sequence is generated based on the grid phase, the AC current, and the real-time rectified voltage.

[0032] As an inventive concept, the present invention also provides an adaptive compensation control system for DC interference current, comprising:

[0033] One or more processors;

[0034] A memory having stored one or more programs that, when executed by one or more processors, cause the one or more processors to perform the steps of the method described above.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] (1) This invention replaces the traditional power frequency transformer and diode uncontrolled rectification or thyristor phase-controlled voltage regulation scheme with a single-phase PWM rectifier circuit. It uses a phase-locked loop to extract the grid phase and combines it with a pre-constructed rectifier voltage control model for closed-loop control to generate a precise switching transistor drive sequence. Since the model takes the target rectified voltage, real-time rectified voltage, AC current and grid phase as inputs, it can dynamically adjust the current in the AC inductor to strictly track the grid voltage, thereby achieving unity power factor operation. This solves the problems of low power factor, severe harmonic pollution and slow response caused by nonlinear rectification in the prior art, improves the power quality on the grid side, and provides a highly stable DC input foundation for subsequent circuits.

[0037] (2) This invention constructs an isolation stage composed of dual active bridge converter circuits and dynamically sets its target isolation voltage based on preset voltage coordination control rules. It then uses a pre-constructed isolation voltage control model to calculate the phase shift angle and generate a phase-shifting pulse signal. Since this model takes the target isolation voltage and the real-time isolation voltage as inputs and uses a high-frequency transformer for magnetic energy transfer, it can accurately adjust and stabilize the output isolation voltage. This solves the problem of existing technologies lacking efficient electrical isolation and wide-range stable output capabilities. It not only achieves safe electrical isolation between the power grid and pipelines but also ensures high efficiency and high dynamic response accuracy of energy transmission over a wide input voltage range, providing reliable power supply for the full-bridge compensation stage.

[0038] (3) This invention calculates the potential control quantity and generates a full-bridge drive signal by inputting the real-time pipe-to-ground potential and a preset target value into a pre-constructed pipe-to-ground potential control model, thereby controlling the working mode of the full-bridge circuit. Since this model adopts a proportional-integral control structure, combined with the base gain and compensation coefficient, it can precisely adjust the output voltage to control the direction and magnitude of the output current, achieving reverse compensation or active absorption of strong DC interference current. This solves the problems of insufficient accuracy and inability to bidirectionally manage stray currents in existing analog control methods, enabling the pipe-to-ground potential to be stabilized within a safe range with high precision, effectively suppressing pipeline corrosion, and achieving wide-range management of both positive and negative strong DC interference currents. Attached Figure Description

[0039] Figure 1 This is a schematic diagram of the adaptive compensation control system for strong DC interference current according to an embodiment of the present invention;

[0040] Figure 2 This is the topology of the adaptive compensation control system for strong DC interference current in an embodiment of the present invention;

[0041] Figure 3 This is a block diagram of the rectifier voltage control method for the adaptive compensation control method of strong DC interference current according to an embodiment of the present invention;

[0042] Figure 4 This is a block diagram of the isolation voltage control method for the adaptive compensation control method of strong DC interference current according to an embodiment of the present invention;

[0043] Figure 5 This is a block diagram of the tube-to-ground potential control method for the adaptive compensation control method of strong DC interference current according to an embodiment of the present invention. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.

[0045] Example 1

[0046] The first embodiment of the present invention provides an adaptive compensation control method for strong DC interference current, comprising:

[0047] 1) Collect single-phase AC voltage, AC current, real-time rectified voltage, real-time isolation voltage, real-time tube-to-ground potential, and output voltage of the power grid by sequentially connecting a single-phase PWM rectifier circuit, a dual active bridge converter circuit, and a full-bridge circuit.

[0048] 2) Based on the output voltage of the full-bridge circuit, determine the target isolation voltage of the dual active bridge converter circuit and the target rectified voltage of the single-phase PWM rectifier circuit through preset voltage coordination control rules;

[0049] 3) Perform phase-locked loop (PLL) extraction on the single-phase AC voltage of the power grid to obtain the power grid phase;

[0050] 4) Based on the grid phase, AC current and real-time rectified voltage, the rectified voltage is controlled in a closed loop using a pre-built rectified voltage control model, and a switching transistor drive sequence is generated.

[0051] 5) Control the bridge arm on / off timing of the single-phase PWM rectifier circuit according to the switching transistor drive sequence, output the rectified voltage, and use it as the input voltage of the dual active bridge converter circuit;

[0052] 6) Based on the real-time rectified voltage and real-time isolation voltage, calculate the phase shift angle and generate a phase shift pulse signal using a pre-built isolation voltage control model;

[0053] 7) The switching sequence of the primary and secondary bridge arms of the dual active bridge converter circuit is controlled according to the phase-shifting pulse signal. The high-frequency transformer T is used for magnetic energy transfer to adjust and stabilize the isolation voltage output by the dual active bridge converter circuit, which is then used as the input voltage of the full-bridge circuit.

[0054] 8) Input the real-time pipe-to-ground potential and the preset target pipe-to-ground potential into the pre-constructed pipe-to-ground potential control model to calculate the potential control quantity, and generate a full-bridge drive signal based on the potential control quantity;

[0055] 9) The working mode of the full-bridge circuit is controlled by the full-bridge drive signal. The output current is controlled by adjusting the output voltage to perform reverse compensation or active absorption of stray current, so that the tube ground potential is stabilized within the preset tube ground potential safety range.

[0056] In 1), the single-phase AC voltage, AC current, real-time rectified voltage, real-time isolation voltage, real-time tube-to-ground potential, and output voltage of the power grid are collected by a single-phase PWM rectifier circuit, a dual active bridge converter circuit, and a full-bridge circuit connected in sequence.

[0057] A single-phase PWM rectifier circuit includes:

[0058] First switch S1, second switch S2, third switch S3, fourth switch S4, first capacitor C1, AC inductor L m ;

[0059] The first switch S1 and the second switch S2 are connected in series, with the midpoint of the series connection being the series node a. The AC inductance L m One end is connected to the series node a, and the other end is connected to the live wire of 220V AC power;

[0060] The third switch S3 and the fourth switch S4 are connected in series, with the midpoint of the series connection being the series node b, and connected to the neutral wire of 220V AC power.

[0061] The upper ends of the first switch S1 and the third switch S3 are connected to the positive output of the single-phase PWM rectifier circuit, and the lower ends of the second switch S2 and the fourth switch S4 are connected to the negative output of the single-phase PWM rectifier circuit.

[0062] The first capacitor C1 is connected in parallel between the positive and negative terminals of the output side.

[0063] The dual active bridge converter circuit includes:

[0064] Fifth switch S5, sixth switch S6, seventh switch S7, eighth switch S8, ninth switch S9, tenth switch S 10 Eleventh switch S 11 12th switch S 12 The second capacitor C2, the third capacitor C3, and the high-frequency transformer T;

[0065] The fifth switch S5 and the sixth switch S6 are connected in series, with the midpoint of their series connection being the series node c. The seventh switch S7 and the eighth switch S8 are connected in series, with the midpoint of their series connection being the series node d.

[0066] The upper ends of the fifth switch S5 and the seventh switch S7 are connected to the positive input terminal of the dual active bridge converter circuit, and the lower ends of the sixth switch S6 and the eighth switch S8 are connected to the negative input terminal of the dual active bridge converter circuit.

[0067] The second capacitor C2 is connected in parallel between the positive and negative terminals of the input side of the dual active bridge converter circuit;

[0068] One end of the primary winding of the high-frequency transformer T is connected to the series node c, and the other end is connected to the series node d.

[0069] Ninth switch S9 and tenth switch S 10 The series connection is such that the midpoint of the series connection is the series node e, and the eleventh switch S is connected in series. 11 With the twelfth switch S 12 A series connection, with the midpoint of the series connection being the series node f;

[0070] Ninth switch S9 and eleventh switch S 11 The upper ends are connected to the positive output terminal of the dual active bridge converter circuit, and the tenth switch S 10 With the twelfth switch S 12 The lower ends are connected together to the negative output terminal of the dual active bridge converter circuit;

[0071] The third capacitor C3 is connected in parallel between the positive and negative terminals of the output side of the dual active bridge converter circuit;

[0072] The two ends of the secondary winding of the high-frequency transformer T are connected to the series node e and the series node f, respectively.

[0073] A full-bridge circuit includes:

[0074] The thirteenth switching transistor S 13 Fourteenth switch S 14 The fifteenth switching transistor S 15 Sixteenth switch S 16 Fourth capacitor C4, filter inductor L f and filter capacitor C f ;

[0075] The thirteenth switching transistor S 13 With the fourteenth switch S 14 The series connection is such that the midpoint of the series connection is the series node g, and the fifteenth switch S is connected in series. 15 With the sixteenth switch S 16 The series connection is such that the midpoint of the series connection is the series node h;

[0076] The thirteenth switching transistor S 13 With the fifteenth switch S 15 The upper ends of the transistors are connected to the positive input terminal of the full-bridge circuit, and the fourteenth switch S...14 With the sixteenth switch S 16 The lower ends of both are connected to the negative input terminal of the full-bridge circuit;

[0077] The fourth capacitor C4 is connected in parallel between the positive and negative terminals of the input side of the full-bridge circuit;

[0078] Filter inductor L f One end is connected to the series node g, and the other end serves as the positive output of the full-bridge circuit. The series node h serves as the negative output of the full-bridge circuit.

[0079] Filter capacitor C f It is connected in parallel between the positive and negative terminals of the input side of the full-bridge circuit;

[0080] The positive output terminal of the full-bridge circuit is connected to the auxiliary anode in the cathodic protection station, and the negative output terminal of the full-bridge circuit is connected to the buried pipeline.

[0081] Specifically, multiple key electrical variables from the power grid and within the system are collected through a single-phase PWM rectifier circuit, a dual active bridge converter circuit, and a full-bridge circuit connected in sequence. Data sources include the live and neutral wire connection points of the 220V AC power supply, the output terminal of the single-phase PWM rectifier circuit, the primary and secondary connection points of the dual active bridge converter circuit, and the output terminal of the full-bridge circuit. The specific data collected include single-phase AC voltage from the power grid, AC current, real-time rectified voltage, real-time isolation voltage, output voltage, and real-time ground potential. The single-phase AC voltage is measured between the live and neutral wires, and the AC current is measured through the AC inductor L. m The real-time rectified voltage is obtained from the two ends of the first capacitor C1 between the positive and negative terminals of the output side of the single-phase PWM rectifier circuit; the real-time isolation voltage is measured from the two ends of the third capacitor C3 on the output side of the dual active bridge converter; the output voltage is obtained from the filter capacitor C between the positive and negative terminals of the output side of the full-bridge circuit. f The real-time pipeline potential is obtained from the reference electrode and the two ends of the buried pipeline.

[0082] In the implementation process, the single-phase PWM rectifier circuit periodically controls the on / off states of the first switch S1 to the fourth switch S4, thereby controlling the AC inductor L. m The current in the converter tracks the phase of the grid voltage, thus achieving unity power factor rectification. The rectified DC voltage is stabilized by the first capacitor C1 and serves as the input to the dual active bridge converter circuit. The dual active bridge converter circuit, through the coordinated switching actions of the fifth to twelfth switches, forms phase-shift control on both sides of the high-frequency transformer T, regulating the bidirectional flow of energy. The second capacitor C2 and the third capacitor C3 maintain the stability of the DC bus voltage on the input and output sides, respectively. In the full-bridge circuit, the thirteenth to sixteenth switches switch at a set frequency, working in conjunction with the filter inductor L. f With filter capacitor C fIt forms a low-pass filter that smooths high-frequency pulse voltage into a continuous DC output for use in cathodic protection systems.

[0083] In step 2), the target isolation voltage of the dual active bridge converter circuit and the target rectified voltage of the single-phase PWM rectifier circuit are determined by the preset voltage coordination control rules based on the output voltage of the full-bridge circuit.

[0084] The voltage coordination control rules are as follows:

[0085]

[0086]

[0087] in, Indicates the target isolation voltage. , and These represent the preset first target isolation voltage, second target isolation voltage, and third target isolation voltage, respectively. Indicates the target rectified voltage. , and These represent the preset first target rectified voltage, second target rectified voltage, and third rectified isolation voltage, respectively. o U represents the output voltage. o1 and U o2 U represents the preset first output voltage threshold and the second output voltage threshold, respectively. DAB U represents the real-time isolation voltage. DAB1 and U DAB2 These represent the preset first isolation voltage threshold and the second isolation voltage threshold, respectively.

[0088] Voltage coordination control rules establish a system based on the final output state of the system (i.e., the output voltage u of the full-bridge circuit). o This mechanism dynamically and collaboratively sets the operating targets of the first two power conversion stages (single-phase PWM rectifier circuit and dual active bridge converter circuit). This design breaks the limitations of traditional multi-stage power supply systems where each stage has its own independently and statically set operating point, achieving globally optimized energy management. Especially when dealing with drastic fluctuations in the amplitude of strong DC interference current, this rule can adaptively select the optimal combination of target isolation voltage and target rectified voltage based on the real-time state of the output voltage, ensuring that each stage always operates within its efficient range. This provides a wide-range, highly stable voltage support for the subsequent full-bridge circuit, demonstrating the system's adaptive adjustment capability under complex interference.

[0089] This strongly supports the core requirement of "wide-range compensation." The stray current's intensity and direction vary drastically, leading to a requirement for a specific compensation voltage (i.e., the output voltage u of the full-bridge circuit).o It must also be able to adjust rapidly over a wide range. If the target voltage of the first two stages remains constant, a significant change in the output voltage demand will either cause one stage to enter a region of extremely low efficiency or malfunction (e.g., excessive shift ratio of the dual active bridge), or it will limit the output capability of the entire system. This coordination rule uses a preset threshold (U... o1 U o2 U DAB1 U DAB2 This approach simplifies complex nonlinear relationships into clear, segmented logic, enabling the system to automatically select the optimal "operating mode combination" based on current output demands. For example, when a high output voltage is required, the rules simultaneously set higher target isolation voltage and target rectified voltage, ensuring each stage operates within its efficient range to collectively provide high voltage. Conversely, when low output demand is required, a lower combination is selected to avoid unnecessary energy loss. This not only significantly expands the effective operating range of the entire system, allowing it to handle stray currents of varying intensities, but also ensures high energy conversion efficiency and system stability across the entire range, providing a solid and reliable voltage foundation for the subsequent full-bridge circuit to accurately and quickly perform stray current compensation tasks.

[0090] In step 3), the phase of a single-phase AC voltage of the power grid is extracted using a phase-locked loop to obtain the power grid phase.

[0091] In step 4), based on the grid phase, AC current and real-time rectified voltage, the rectified voltage closed-loop control is performed through a pre-built rectified voltage control model, and a switching transistor drive sequence is generated.

[0092] The rectifier voltage control model is as follows:

[0093]

[0094] in, Indicates the reference alternating current. U represents the target rectified voltage. dc Indicates the real-time rectified voltage, i s U represents alternating current, ωt represents the phase of the power grid, and U represents the phase of the power grid. s Indicates the single-phase AC voltage of the power grid. Indicates the initial modulation signal. Represents the modulated wave signal, k pU1 and k pI1 These are the preset proportional coefficients for the rectified voltage loop and the rectified current loop, k. iU1 and k iI1 These are the preset integral coefficients of the rectified voltage loop and the rectified current loop, respectively, and s represents the Laplace operator.

[0095] In step 5), the single-phase PWM rectifier circuit is controlled by the bridge arm switching timing according to the switching transistor drive sequence, and the rectified voltage is output as the input voltage of the dual active bridge converter circuit.

[0096] Specifically, the switching transistor drive sequence implements bridge arm on / off timing control of the single-phase PWM rectifier circuit, converting the single-phase AC grid voltage into the target rectified voltage, which serves as the input voltage of the dual active bridge converter circuit. The drive signal controls the first switch S1 and the second switch S2 to conduct alternately, and the third switch S3 and the fourth switch S4 to conduct alternately, causing the AC inductor L... m The current in the circuit strictly follows the phase and amplitude changes of the single-phase AC voltage of the power grid. When the first switch S1 and the fourth switch S4 are turned on, the current flows from the live wire of the power grid through the AC inductor L. m The current flows from the first switch S1 to the positive terminal of the output side, and then returns to the neutral line of the power grid via the fourth switch S4; when the second switch S2 and the third switch S3 are turned on, the current flows from the live wire of the power grid through the AC inductor L m The third switch S3 flows to the positive terminal of the output side, and then returns to the neutral line of the power grid via the second switch S2.

[0097] High-frequency switching in AC inductor L m A pulse voltage is generated at both ends, which is filtered by the first capacitor C1 and output as a smooth rectified voltage. This rectified voltage is precisely stabilized at the target rectified voltage, providing a highly stable DC input for the subsequent dual active bridge converter circuit.

[0098] By generating a pulse voltage across the AC inductor through high-frequency switching, and filtering it with a capacitor, a smooth and stable DC voltage is output, providing a high-precision DC input for subsequent circuits. Compared to traditional diode uncontrolled rectification or thyristor phase-controlled rectification, this method achieves unity power factor operation, eliminating harmonic pollution and low power factor problems caused by traditional rectification methods, and improving power quality on the grid side. Simultaneously, this precise voltage control endows the system with a wide output range, enabling it to easily cope with complex operating conditions such as grid voltage fluctuations or drastic load changes. This ensures the normal operation of the subsequent dual active bridge converter circuit and full-bridge circuit, laying a solid front-end energy foundation for the entire cathodic protection system to achieve wide-range compensation of stray currents.

[0099] In step 5), the phase shift angle is calculated and a phase shift pulse signal is generated based on the real-time rectified voltage and the real-time isolation voltage through a pre-built isolation voltage control model.

[0100] The pre-built isolation voltage control model includes:

[0101]

[0102] in, U represents the target isolation voltage.DAB Indicates the real-time isolation voltage. k represents the phase shift angle. pU2 and k iU2 These are the preset isolation voltage loop proportional coefficient and rectifier voltage loop integral coefficient, respectively, and s represents the Laplace operator.

[0103] In step 6), the switching timing of the primary and secondary bridge arms of the dual active bridge converter circuit is controlled according to the phase-shifting pulse signal. The high-frequency transformer T is used for magnetic energy transfer to adjust and stabilize the isolation voltage output by the dual active bridge converter circuit, which serves as the input voltage of the full-bridge circuit.

[0104] Specifically, the phase shift command is multiplied by the switching cycle to determine the delay time of the secondary bridge arm drive signal relative to the primary bridge arm; the fifth switch S5 and the eighth switch S8, the sixth switch S6 and the seventh switch S7 of the primary bridge arm are synchronously turned on, and the ninth switch S9 and the twelfth switch S7 of the secondary bridge arm are synchronously turned on. 12 10th switch S 10 With the eleventh switch S 11 Synchronous conduction is initiated after a delay.

[0105] The primary winding of the high-frequency transformer T is connected between the midpoints c and d of the primary bridge arm, and the secondary winding is connected between the midpoints e and f of the secondary bridge arm. When there is a phase shift angle between the primary and secondary bridge arms, a voltage difference appears on both sides of the high-frequency transformer T. This difference acts on the transformer leakage inductance to generate a real-time isolation current. The direction and amplitude of the real-time isolation current are determined by the polarity and magnitude of the phase shift angle, thereby controlling the power transferred from the input side to the output side. The third capacitor C3 absorbs the pulsating current on the output side, smooths it, and outputs a stable isolation voltage. This isolation voltage serves as the input voltage of the full-bridge circuit, and its value is precisely maintained within the set range.

[0106] Through phase-shift control strategy, efficient and stable electrical isolation and voltage transformation are achieved over a wide input voltage range; magnetic energy transfer is completed by using high-frequency transformer T, avoiding direct electrical connection between the power grid and pipeline, thus improving system safety; precise calculation of phase shift angle and strict synchronization of drive timing ensure the dynamic response speed and steady-state accuracy of output isolation voltage, providing a reliable power supply foundation for the full-bridge circuit.

[0107] In step 7), the real-time pipe-to-ground potential and the preset target pipe-to-ground potential are input into the pre-built pipe-to-ground potential control model to calculate the potential control quantity, and a full-bridge drive signal is generated based on the potential control quantity.

[0108] The pipe-to-ground potential control model is as follows:

[0109]

[0110] Among them, e psFor the pipe-to-ground potential deviation, U is the preset target pipe-to-ground potential. ps For real-time pipe-to-ground potential, R ps For the transition resistance, i * o For the compensation current reference value, u ps k is the output voltage control quantity of the full-bridge circuit. pps k is the preset proportional gain coefficient. ips Here, is the preset integral gain coefficient, and s represents the Laplace operator.

[0111] By making the full-bridge circuit present an equivalent negative impedance characteristic between the pipe and the auxiliary anode, a compensation current opposite to the stray current disturbance is actively generated, so that the pipe-to-ground potential is stabilized within a preset safe range.

[0112] In 8), the working mode of the full-bridge circuit is controlled by the full-bridge drive signal. The output current is controlled by adjusting the output voltage to perform reverse compensation or active absorption of stray current, so that the tube ground potential is stabilized within the preset tube ground potential safety range.

[0113] A drive signal for the full-bridge circuit is generated at a fixed frequency, causing the thirteenth switch S to... 13 With the sixteenth switch S 16 Synchronous conduction, fourteenth switch S 14 With the fifteenth switch S 15 Synchronous conduction. When the thirteenth switch S... 13 With the sixteenth switch S 16 When the circuit is turned on, current flows from the positive terminal of the full-bridge circuit input through the thirteenth switch S. 13 The water flows into the pipe and then through the sixteenth switch tube S. 16 Return to the negative input of the full-bridge circuit; when the fourteenth switch S 14 With the fifteenth switch S 15 When the circuit is turned on, current flows from the positive terminal of the full-bridge circuit input through the fifteenth switch S. 15 The water flows into the pipe and then through the fourteenth switch tube S. 14 Return to the negative input terminal of the full-bridge circuit. Through high-frequency switching, the output terminal of the full-bridge circuit generates a pulse voltage, which is filtered by the fourth capacitor C4 and outputs a smooth output voltage. This output voltage acts between the pipe and the ground, generating an output current to reverse compensate for or actively absorb stray current.

[0114] In reverse compensation mode, the system actively injects current into the pipeline to counteract the harmful effects of stray current. When operating in the first quadrant, the thirteenth switch S... 13 With the sixteenth switch S 16 Synchronous conduction occurs, at which point current flows from the positive input of the full-bridge circuit, passing sequentially through S... 13 Filter inductor Lf Auxiliary anodes flow into the buried pipeline through the ground, and finally through S 16 The current flows back to the negative input terminal, thus actively injecting positive current into the pipe. When operating in the third quadrant, the fourteenth switch S... 14 With the fifteenth switch S 15 Synchronous conduction, current flows from the positive input terminal, through S 15 It flows to the auxiliary anode, passes through the ground into the buried pipeline, and then through S... 14 The current flows back to the negative input terminal, at which point the system outputs a negative voltage, actively absorbing external current that attempts to flow into the pipe.

[0115] In active absorption mode, the system recovers energy from stray currents. When operating in the second quadrant, the fourteenth switch S... 14 With the fifteenth switch S 15 Synchronous conduction occurs, but at this time the full-bridge circuit adjusts the output voltage to be lower than the pipe ground potential, forcing the current to start from the auxiliary anode, flow through the ground into the buried pipeline, and then through S. 14 Filter inductor L f and S 15 The flow returns to the circuit, recovering excess energy. When operating in the fourth quadrant, the thirteenth switch S... 13 With the sixteenth switch S 16 Synchronous conduction, circuit adjustment reverses the current, and the stray current flowing from the pipe passes through S 16 S 13 The current is guided back to the input side to achieve energy recovery. Through the high-frequency switching of these four switch combinations, the full-bridge circuit can precisely control the magnitude and direction of the current, achieving wide-range management of stray current.

[0116] Through precise control of the full-bridge circuit, a controllable compensating current is established between the pipeline and the ground, suppressing the corrosive effect of stray currents on the pipeline. Closed-loop control of the pipeline-to-ground potential ensures that the pipeline potential is always maintained within a safe range, avoiding over-protection or under-protection. The bidirectional current output capability of the full-bridge circuit enables it to operate in four quadrants, adaptively switching its operating mode according to the polarity and direction of the interference current. This allows it to both reverse compensate for positive DC interference currents and actively absorb negative DC interference currents, achieving comprehensive, dead-angle-free control of complex DC interference currents.

[0117] Example 2

[0118] Embodiment 2 of the present invention provides a system corresponding to Embodiment 1 above, including a memory, a processor, and a computer program stored in the memory; the processor executes the computer program in the memory to implement the steps of the method of Embodiment 1 above.

[0119] In some implementations, the memory may be high-speed random access memory (RAM), and may also include non-volatile memory, such as at least one disk storage device.

[0120] In other implementations, the processor can be any type of general-purpose processor, such as a central processing unit (CPU) or a digital signal processor (DSP), and there is no limitation here.

[0121] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0122] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. An adaptive compensation control method for DC interference current, characterized in that, Includes the following steps: A single-phase PWM rectifier circuit, a dual active bridge converter circuit, and a full-bridge circuit are connected in sequence. The single-phase PWM rectifier circuit is connected to the power grid, and the full-bridge circuit is connected to the reference electrode and auxiliary anode located near the pipeline. The single-phase AC voltage and AC current of the power grid, the real-time rectified voltage, the real-time isolation voltage, the real-time pipeline ground potential, and the output voltage of the full-bridge circuit are collected. Based on the output voltage of the full-bridge circuit, determine the target isolation voltage of the dual active bridge converter circuit and the target rectified voltage of the single-phase PWM rectifier circuit. Phase-locked loop (PLL) phase extraction is performed on the single-phase AC voltage of the power grid to obtain the power grid phase; A switching transistor drive sequence is generated based on the grid phase, the AC current, the real-time rectified voltage, and the target rectified voltage; Based on the real-time isolation voltage and the target isolation voltage, the phase shift angle is calculated and a phase shift pulse signal is generated; The potential control quantity is calculated using the real-time pipe-to-ground potential and the preset target pipe-to-ground potential, and a full-bridge drive signal is generated based on the potential control quantity. The single-phase PWM rectifier circuit is controlled by the switching transistor driving sequence to control the bridge arm on / off timing, output rectified voltage, and use the rectified voltage as the input voltage of the dual active bridge converter circuit. The switching timing of the primary and secondary arms of the dual active bridge converter circuit is controlled according to the phase-shifting pulse signal. Magnetic energy is transferred using a high-frequency transformer to adjust and stabilize the isolation voltage output by the dual active bridge converter circuit. This isolation voltage is then used as the input voltage of the full-bridge circuit. The operating mode of the full-bridge circuit is controlled by the full-bridge drive signal. The output current is controlled by adjusting the output voltage of the full-bridge circuit to perform reverse compensation or active absorption of stray current, so that the tube ground potential is stabilized within the preset tube ground potential safety range.

2. The adaptive compensation control method for DC interference current according to claim 1, characterized in that, The target isolation voltage expression for the dual active bridge converter circuit is: ； in, Indicates the target isolation voltage. , and These represent the preset first target isolation voltage, second target isolation voltage, and third target isolation voltage, respectively. o U represents the output voltage of the full-bridge circuit. o1 and U o2 These represent the preset first output voltage threshold and the second output voltage threshold, respectively.

3. The adaptive compensation control method for DC interference current according to claim 1, characterized in that, The expression for the target rectified voltage of a single-phase PWM rectifier circuit is: ； in, Indicates the target rectified voltage. , and These represent the preset first target rectified voltage, second target rectified voltage, and third rectified isolation voltage, respectively. U DAB U represents the real-time isolation voltage. DAB1 and U DAB2 These represent the preset first isolation voltage threshold and the second isolation voltage threshold, respectively.

4. The adaptive compensation control method for DC interference current according to claim 1, characterized in that, The switching transistor driving sequence is obtained by comparing a modulation wave signal with a triangular carrier signal. The expression for the modulation wave signal is: ； in, Indicates the reference alternating current. U represents the target rectified voltage. dc Indicates the real-time rectified voltage, i s U represents alternating current, ωt represents the phase of the power grid, and U represents the phase of the power grid. s Indicates the single-phase AC voltage of the power grid. Indicates the initial modulation signal. Represents the modulated wave signal, k pU1 and k pI1 These are the preset proportional coefficients for the rectified voltage loop and the rectified current loop, k. iU1 and k iI1 These are the preset integral coefficients of the rectified voltage loop and the rectified current loop, respectively, and s represents the Laplace operator.

5. The adaptive compensation control method for DC interference current according to claim 1, characterized in that, The formula for calculating the phase shift angle is: ； in, U represents the target isolation voltage. DAB Indicates the real-time isolation voltage. k represents the phase shift angle. pU2 and k iU2 These are the preset isolation voltage loop proportional coefficient and rectifier voltage loop integral coefficient, respectively, and s represents the Laplace operator.

6. The adaptive compensation control method for DC interference current according to claim 1, characterized in that, The formula for calculating the potential control quantity is: ； Among them, e ps For the pipe-to-ground potential deviation, U * ps U is the preset target pipe-to-ground potential. ps For real-time pipe-to-ground potential, G NIC Z is the preset negative impedance equivalent admittance coefficient. NIC The preset negative impedance parameters, For the compensation current reference value, u ps k is the output voltage control quantity of the full-bridge bridge, i.e., the potential control quantity. pps k is the preset proportional gain coefficient. ips Here, is the preset integral gain coefficient, and s represents the Laplace operator.

7. An adaptive compensation control system for DC interference current, characterized in that, include: One or more processors; A memory having stored one or more programs that, when executed by one or more processors, cause the one or more processors to perform the steps of the method according to any one of claims 1 to 6.

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