A leakage current inversion boost grid-connected control and safety protection method and system

Abstract

The application discloses a leakage electric inverse variation voltage-boosting grid-connected control and safety protection method and system, relates to the technical field of power grid safety control, and comprises the following steps: performing multistage voltage reduction on the leakage voltage of the equipment shell; performing AC-DC conversion, filtering and voltage stabilization on the reduced AC leakage voltage; collecting electrical parameters in real time; comparing the real-time leakage voltage with a preset voltage range, dynamically adjusting the PWM pulse width based on a control algorithm; comparing a preset leakage current starting threshold and a power upper threshold with the real-time leakage current, and executing a safety protection action according to the comparison result; continuously monitoring the leakage voltage and the leakage current, and disconnecting the bypass safety circuit and restarting the inverse variation voltage-boosting grid-connected circuit when the leakage voltage and the leakage current return to the normal range; and returning the leakage energy that is not connected to the grid to a preset loop during the inverse variation voltage-boosting grid-connected process. The application can solve the technical problems of high leakage risk and insufficient protection in the prior art, realize closed-loop voltage stabilization control, and guarantee the safe and stable operation of the system.

Description

Technical Field

[0001] This invention relates to the field of power grid safety control technology, specifically to a leakage current inverter boost grid connection control and safety protection method and system. Background Technology

[0002] In existing low-voltage power distribution systems, industrial equipment, or electrical maintenance, electrical equipment is prone to leakage current hazards due to factors such as insulation aging, moisture, mechanical damage, or improper construction. This manifests as accidental electrification of the equipment casing or metal components. Such leakage is prevalent in low-voltage power supply networks, especially in complex electrical environments such as older residential areas, temporary power installations, and industrial plants. If these leakage hazards are not effectively identified and properly managed, not only will the leaked energy be wasted as heat, resulting in energy loss, but it may also trigger accidents, posing a serious threat to the safe and stable operation of the power system and personal safety.

[0003] Current technologies still have many inherent defects in practical applications: traditional RCDs are mostly passive protection, which can only mechanically trip and cut off power when the leakage current exceeds a set threshold. This is a post-event remedy and cannot actively guide or suppress leakage energy; existing protection devices have limited functions and cannot monitor the dynamic changes of leakage voltage in real time, lacking the ability to quantitatively assess and accurately control leakage energy; with the popularization of distributed power sources and power electronic equipment, the harmonic interference in the power grid is complex, which can easily lead to malfunctions or failures to operate of traditional protection devices, resulting in poor adaptability; and they have failed to achieve energy recovery, risk management and green energy saving under leakage fault conditions.

[0004] Therefore, there is an urgent need for an active management method that can coordinate leakage current inverter voltage boosting grid connection with safety protection technology to achieve real-time monitoring, precise control and energy recovery of leakage current hazards, and adapt to the wide application needs of various low-voltage power distribution scenarios. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the shortcomings of the prior art by providing a leakage current inverter boost grid-connected control and safety protection method and system.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for controlling and protecting a leakage current inverter boost grid connection includes the following steps: Step S1: Perform multi-stage voltage reduction processing on the input leakage voltage of the device casing; Step S2: Perform AC-DC conversion, filtering, and voltage regulation on the stepped-down AC leakage voltage to output a stable DC input voltage; Step S3: By linking the detection and acquisition circuit with the leakage current inverter boost grid-connected circuit, electrical parameters including at least leakage voltage, leakage current, grid-connected power and PWM pulse width are collected in real time and synchronously. Step S4: Compare the real-time leakage voltage with the preset voltage range, and dynamically adjust the PWM pulse width of the leakage current inverter boost grid-connected circuit based on the algorithm to form a closed-loop voltage regulation control loop for leakage voltage. Step S5: Preset the leakage current start threshold and leakage current power upper limit threshold, compare them with the real-time leakage current, and execute the corresponding safety protection action according to the comparison result. Step S6: Continuously monitor the leakage voltage and leakage current parameters. When both return to the preset normal range, control the disconnection of the bypass safety circuit, restart the leakage current inverter boost grid-connected circuit, and restore the normal working state of the system. Step S7: Based on the real-time grid-connected power and the output capacity of the leakage current inverter boost grid-connected circuit, dynamically allocate the power ratio between the leakage current return path and the inverter boost grid-connected path, and return the leakage current energy that has not been connected to the grid to the preset circuit.

[0007] Further, in step S1, the multi-stage voltage reduction process specifically includes: The first stage of processing is bidirectional semiconductor limiting processing: a bidirectional transient voltage suppression device is connected in parallel at the leakage voltage input terminal to clamp the amplitude of the input leakage voltage to within a preset first safety threshold. The second stage of processing involves bridge rectification and composite filtering: the limited AC leakage voltage is input into the full-bridge rectifier circuit and converted into a pulsating DC voltage, which is then connected to an LC filter composed of a series inductor and a parallel capacitor to output a DC voltage. The third stage of processing involves switching boost and dynamic impedance matching: the filtered DC voltage is input to the Boost circuit, while the control unit identifies the equivalent impedance model of the leakage path online based on the real-time collected drain-source voltage and leakage current, and dynamically adjusts the input impedance of the Boost circuit according to the identification results, so that the leakage energy extraction efficiency meets the preset maximum power point tracking target, and finally outputs a stable DC voltage that is compatible with the subsequent inverter circuit.

[0008] Furthermore, in step S2, a DC-DC converter is used to regulate the filtered DC voltage so that the output DC voltage matches the input requirements of the subsequent circuit. The filtering is performed using a combination of capacitor filtering and inductor filtering. Specifically, a multi-stage composite filter network is constructed between the output of the rectifier circuit and the input of the DC-DC converter. The multi-stage composite filter network includes: a first-stage filter unit composed of electrolytic capacitors, used to filter out low-frequency ripple after rectification; a second-stage filter unit composed of a differential-mode inductor and a high-frequency ceramic capacitor forming an LC series branch, used to suppress high-frequency noise; and a third-stage filter unit composed of the input and output capacitors of the Boost circuit itself, forming a cascaded filter structure.

[0009] Furthermore, in the multi-stage voltage reduction process, the third stage specifically includes the following steps: An equivalent impedance model of the leakage current channel is constructed. The instantaneous sampled values ​​of leakage voltage and leakage current are used as inputs. The recursive least squares algorithm is used for online iterative calculation to identify the equivalent resistance and equivalent inductance parameters of the leakage current channel in real time. Based on the maximum power transfer theorem, and using the identified equivalent resistance and equivalent inductance as a basis, the optimal input impedance of the Boost circuit that maximizes the leakage energy transfer efficiency is calculated. The optimal input impedance is the complex conjugate of the equivalent impedance of the leakage channel, that is, the equivalent resistance minus the inductive reactance component of the equivalent inductance. The control unit dynamically adjusts the duty cycle of the switching transistor in the Boost circuit according to the calculated optimal input impedance, so that the equivalent input impedance of the Boost circuit tracks the optimal input impedance in real time, thereby achieving impedance matching between the leakage path and the Boost circuit. While achieving impedance matching, the Boost circuit maintains stable output voltage through duty cycle adjustment, ultimately outputting a stable DC voltage that is compatible with the subsequent inverter circuit.

[0010] Furthermore, in step S4, the dynamic adjustment of the PWM pulse width of the leakage current inverter boost grid-connected circuit based on the algorithm specifically includes the following steps: Calculate the deviation between the actual value of leakage voltage and the preset reference value and its rate of change. Based on the absolute value of the deviation, divide the adjustment process into coarse adjustment zone, fine adjustment zone and steady state zone. Within the fine-tuning range, the deviation and its rate of change are input into the fuzzy controller. After fuzzification, fuzzy inference, and defuzzification, the correction values ​​of the proportional coefficient and integral coefficient are output to perform online adaptive tuning of the PI parameters. An incremental PID algorithm is used to calculate the adjustment of the PWM pulse width, where the proportional coefficient and integral coefficient are the values ​​after fuzzy adaptive tuning; Based on the partitioning results, variable step size adjustment is performed: the coarse adjustment zone uses the maximum step size for fast response, the fine adjustment zone uses incremental PID calculation values ​​for fine adjustment, and the steady-state zone introduces dead zone control and freezes the integral term to suppress frequent jitter of PWM pulse width.

[0011] Furthermore, in step S4, when the PWM pulse width adjustment has reached the preset limit duty cycle and the leakage voltage is still lower than the preset reference value, it is determined that the system is in an input power limited state, and the auxiliary adjustment mechanism is activated: the control unit abandons the voltage closed-loop control and instead executes the maximum power point tracking strategy, adjusting the duty cycle through the perturbation observation method to maximize the leakage energy extraction efficiency; at the same time, the grid current amplitude setpoint is limited to a safe value that matches the current maximum input power; when the leakage voltage rises back to the preset range or the leakage current increases to meet the power demand, the maximum power point tracking mode is exited and the voltage regulation closed-loop control is restored.

[0012] Furthermore, in step S5, the specific safety protection action includes: When the leakage current is lower than the starting threshold, it is determined that the leakage energy is insufficient to support the inverter boost grid connection, the circuit is prohibited from starting and the bypass safety circuit is connected. When the leakage current exceeds the power limit threshold, it is determined to be an overload state, and the PWM output is immediately blocked, the inverter boost grid-connected circuit is shut down, and the bypass safety circuit is simultaneously connected. When the leakage current is between the start-up threshold and the upper limit threshold, the system maintains normal inverter boost grid-connected operation.

[0013] A leakage current inverter boost grid-connected control and safety protection system, used to implement any one of the leakage current inverter boost grid-connected control and safety protection methods, comprising: The leakage current acquisition and preprocessing unit has an input terminal that is electrically connected to the leakage voltage. It contains a multi-stage step-down circuit and an adaptive impedance matching network. The output terminal outputs the AC leakage voltage signal after step-down and impedance matching. The rectifier, filter and voltage regulator unit is electrically connected to the output of the leakage current acquisition and preprocessing unit. It integrates a rectifier circuit, a filter circuit and a DC-DC voltage regulator converter, and outputs a stable DC input voltage. The leakage current inverter boost grid-connected unit has its input terminal electrically connected to the output terminal of the rectifier, filter and voltage regulator unit, and its output terminal electrically connected to the grid interface and the leakage current return unit, respectively. It is used to invert DC voltage into AC voltage and complete the boost, phase-locking and grid-connected power supply. The full-range parameter detection unit includes a voltage sensor, a current sensor, and a signal conditioning circuit. The acquisition end is electrically connected to the leakage voltage input end, the leakage current loop, the output end of the rectification, filtering and voltage regulation unit, the output end of the inverter unit, and the grid-connected side. The output end outputs digital electrical parameters. The central control unit, with a digital signal processor or field programmable gate array as its core, has its input terminal electrically connected to the output terminal of the global parameter detection unit, and its output terminal electrically connected to the control terminals of the leakage current inverter boost grid-connected unit, the bypass safety execution unit, and the leakage current return unit, forming an information closed-loop control circuit. The bypass safety actuator has its input terminal electrically connected to the leakage voltage, its output terminal electrically connected to the preset safety discharge path, and its controlled terminal electrically connected to the central control unit. Under the control of the central control unit, it realizes the safe discharge of leakage voltage. The leakage current return unit has its input end electrically connected to the output end of the leakage current inverter boost grid-connected unit, its output end electrically connected to the system's preset return bus or energy storage link, and its controlled end electrically connected to the central control unit. Under the control of the central control unit, leakage current energy is recovered and utilized. The central control unit acquires the electrical parameters of each unit in real time through the global parameter detection unit, processes them through an internal algorithm, and sends control commands to each execution unit. The state changes of each execution unit are fed back to the central control unit through the global parameter detection unit, forming a complete closed-loop control system.

[0014] Furthermore, the central control unit specifically includes: The variable step size adaptive PID voltage regulation control module is used to execute the closed-loop voltage regulation control algorithm; The dual-threshold safety protection module is used to execute the leakage current dual-threshold protection logic; The leakage current return and collaborative scheduling module is used to perform dynamic allocation of power ratios.

[0015] Furthermore, the bypass safety execution unit internally employs a solid-state relay or thyristor switching circuit; the leakage current return unit internally integrates a bidirectional DC-DC converter, supporting bidirectional flow of leakage energy to a preset circuit and voltage matching.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention effectively suppresses leakage voltage fluctuations through multi-stage voltage reduction and closed-loop voltage regulation, avoiding the risk of electric shock caused by the equipment casing being electrified; the dual threshold protection mechanism can prevent the circuit from running dry or overloaded, ensuring that the system operates within a safe range.

[0017] 2. This invention achieves coordinated control of leakage current inverter boosting, voltage stabilization and grid connection, and backflow recovery. It enables the grid connection and reuse of leakage current that would otherwise be wasted through inverter boosting, while simultaneously recovering leakage current that is not connected to the grid. This realizes the reuse of leakage current resources, reduces energy waste, meets green energy-saving requirements, and aligns with the development trend of energy conservation and consumption reduction in the power industry.

[0018] 3. This invention adopts a dual-threshold protection mechanism for leakage current, which covers two abnormal scenarios: excessively low leakage current and excessively high leakage current. The bypass safety circuit switches quickly and can reduce the leakage voltage to a safe range within 10ms, effectively avoiding safety accidents.

[0019] 4. The preset voltage range, leakage current dual threshold, and various adjustment parameters of this invention can be adaptively adjusted according to the actual application scenario. It can be adapted to leakage current return inverter boost grid-connected systems of different specifications, and can be directly applied. It has high practical value and industrialization prospects. Attached Figure Description

[0020] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of a method according to an embodiment of the present invention; Figure 2 This is a fuzzy adaptive PID control logic diagram according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the system structure according to an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] like Figure 1 As shown, a method for leakage current inverter boost grid connection control and safety protection includes the following steps: Step S1: Perform multi-stage voltage reduction processing on the input leakage voltage of the device casing; Step S2: Perform AC-DC conversion, filtering, and voltage regulation on the stepped-down AC leakage voltage to output a stable DC input voltage; Step S3: By linking the detection and acquisition circuit with the leakage current inverter boost grid-connected circuit, electrical parameters including at least leakage voltage, leakage current, grid-connected power and PWM pulse width are collected in real time and synchronously. Step S4: Compare the real-time leakage voltage with the preset voltage range, and dynamically adjust the PWM pulse width of the leakage current inverter boost grid-connected circuit based on the algorithm to form a closed-loop voltage regulation control loop for leakage voltage. Step S5: Preset the leakage current start threshold and leakage current power upper limit threshold, compare them with the real-time leakage current, and execute the corresponding safety protection action according to the comparison result. Step S6: Continuously monitor the leakage voltage and leakage current parameters. When both return to the preset normal range, control the disconnection of the bypass safety circuit, restart the leakage current inverter boost grid-connected circuit, and restore the normal working state of the system. Step S7: Based on the real-time grid-connected power and the output capacity of the leakage current inverter boost grid-connected circuit, dynamically allocate the power ratio between the leakage current return path and the inverter boost grid-connected path, and return the leakage current energy that has not been connected to the grid to the preset circuit.

[0023] In step S1, the multi-stage voltage reduction process specifically includes: The first stage of processing is bidirectional semiconductor limiting: a bidirectional transient voltage suppression device, such as a TVS diode or a back-to-back Zener diode, is connected in parallel at the leakage voltage input terminal to clamp the amplitude of the input leakage voltage to within a preset first safety threshold, such as ±400V, to suppress voltage spikes and protect the subsequent circuits. The second stage of processing is bridge rectification and composite filtering: the limited AC leakage voltage is input into the full-bridge rectifier circuit and converted into a pulsating DC voltage, which is then connected to an LC filter composed of a series inductor and a parallel capacitor to output a DC voltage. This LC filter can effectively filter out the high-frequency ripple generated by rectification. The third stage of processing involves switching boost and dynamic impedance matching: the filtered DC voltage is input to the Boost circuit, while the control unit identifies the equivalent impedance model of the leakage path online based on the real-time collected drain-source voltage and leakage current, and dynamically adjusts the input impedance of the Boost circuit according to the identification results, so that the leakage energy extraction efficiency meets the preset maximum power point tracking target, and finally outputs a stable DC voltage that is compatible with the subsequent inverter circuit.

[0024] In step S2, a DC-DC converter is used to regulate the filtered DC voltage so that the output DC voltage matches the input requirements of the subsequent circuit. The filtering is performed using a combination of capacitor filtering and inductor filtering. Specifically, a multi-stage composite filter network is constructed between the output of the rectifier circuit and the input of the DC-DC converter. The multi-stage composite filter network includes: a first-stage filter unit composed of electrolytic capacitors, used to filter out low-frequency ripple after rectification; a second-stage filter unit composed of a differential-mode inductor and a high-frequency ceramic capacitor forming an LC series branch, used to suppress high-frequency noise; and a third-stage filter unit composed of the input and output capacitors of the Boost circuit itself, forming a cascaded filter structure.

[0025] In the multi-stage voltage reduction process, the third stage specifically includes the following steps: An equivalent impedance model of the leakage current channel is constructed. The instantaneous sampled values ​​of leakage voltage and leakage current are used as inputs. The recursive least squares algorithm is used for online iterative calculation to identify the equivalent resistance and equivalent inductance parameters of the leakage current channel in real time. Based on the maximum power transfer theorem, and using the identified equivalent resistance and equivalent inductance as a basis, the optimal input impedance of the Boost circuit that maximizes the leakage energy transfer efficiency is calculated. The optimal input impedance is the complex conjugate of the equivalent impedance of the leakage channel, that is, the equivalent resistance minus the inductive reactance component of the equivalent inductance. The control unit dynamically adjusts the duty cycle of the switching transistor in the Boost circuit according to the calculated optimal input impedance, so that the equivalent input impedance of the Boost circuit tracks the optimal input impedance in real time, thereby achieving impedance matching between the leakage path and the Boost circuit. While achieving impedance matching, the Boost circuit maintains stable output voltage through duty cycle adjustment, ultimately outputting a stable DC voltage that is compatible with the subsequent inverter circuit.

[0026] The leakage path is equivalent to an RL model consisting of a resistor and an inductor connected in series. The discrete-time relationship between the instantaneous values ​​of leakage voltage and leakage current is established, as shown in the following formula:

[0027] in, Indicates the sampling time sequence number. Indicates the sampling period. and These represent the leakage voltage and leakage current at the nth sampling, respectively. and These represent the equivalent resistance and equivalent inductance of the leakage path, respectively. In this embodiment, the sampling period is 0.5ms, corresponding to a sampling frequency of 2kHz. Define the parameter vector to be identified Observation matrix for:

[0028] The system observation equation is then:

[0029] in, Indicates observation noise; Set initial values ​​for the parameter vector Typically set as a zero vector, the initial value of the covariance matrix. ,in Take a large positive number, such as 106. For identity matrix, forgetting factor Generally, the value is between 0.95 and 1, less than and not equal to 1, used to reduce the weight of old data; For each sampling time n=1, 2, 3..., the following iterative calculation is performed sequentially: Calculate the gain matrix :

[0030] Calculate the prior estimation error :

[0031] Update parameter estimates :

[0032] in, This represents the parameter estimation vector after the nth iteration; Update covariance matrix :

[0033] After several iterations, the parameters converge, yielding estimates of the equivalent resistance and equivalent inductance. According to the maximum power transfer theorem, the optimal input impedance of the Boost circuit that maximizes leakage energy transfer efficiency should be the complex conjugate of the equivalent impedance of the leakage channel. The specific formula is as follows:

[0034] in, This represents the optimal input impedance. This represents the estimated equivalent resistance. This represents the estimated equivalent inductance. Indicates the angular frequency of the power grid; The control unit adjusts the duty cycle of the switching transistor in the Boost circuit according to the optimal input impedance. The specific calculation formulas for the equivalent input impedance, duty cycle, and equivalent load impedance of the Boost circuit are as follows:

[0035] in, This represents the equivalent input impedance of the Boost circuit. This represents the equivalent load impedance at the output of the Boost circuit. Indicates the duty cycle of the switching transistor in the Boost circuit; By using closed-loop control such as a PI regulator, the equivalent input impedance can be tracked in real time to achieve impedance matching and complete maximum power point tracking. While performing impedance matching, the Boost circuit maintains a stable output voltage by adjusting the duty cycle. The formula for calculating the output voltage versus the input voltage is as follows:

[0036] in, and These represent the input and output voltages of the Boost circuit, respectively. The final output is a stable DC voltage that adapts to the subsequent inverter circuit.

[0037] By linking the detection and acquisition circuit with the leakage current inverter boost grid-connected circuit, the following electrical parameters are collected in real time: leakage voltage, leakage current, grid-connected power, PWM pulse width, DC voltage output from the rectifier and filter circuit, and grid-connected voltage phase. After all the above parameters are processed by the signal conditioning circuit, they are transmitted to the central control unit in digital form. The control unit generates a sinusoidal modulation wave synchronized with the grid based on the grid-connected voltage phase, which serves as the reference for inverter control.

[0038] like Figure 2 As shown, in step S4, the step of dynamically adjusting the PWM pulse width of the leakage current inverter boost grid-connected circuit based on the algorithm specifically includes the following steps: Calculate the deviation between the actual value of leakage voltage and the preset reference value and its rate of change. Based on the absolute value of the deviation, divide the adjustment process into coarse adjustment zone, fine adjustment zone and steady state zone. Within the fine-tuning range, the deviation and its rate of change are input into the fuzzy controller. After fuzzification, fuzzy inference, and defuzzification, the correction values ​​of the proportional coefficient and integral coefficient are output to perform online adaptive tuning of the PI parameters. An incremental PID algorithm is used to calculate the adjustment of the PWM pulse width, where the proportional coefficient and integral coefficient are the values ​​after fuzzy adaptive tuning; Based on the partitioning results, variable step size adjustment is performed: the coarse adjustment zone uses the maximum step size for fast response, the fine adjustment zone uses incremental PID calculation values ​​for fine adjustment, and the steady-state zone introduces dead zone control and freezes the integral term to suppress frequent jitter of PWM pulse width.

[0039]

[0040] in, This represents the voltage deviation value at the k-th sampling time, i.e., the deviation between the actual leakage voltage value and the preset reference value. This indicates the coarse adjustment threshold. Indicates the steady-state threshold; Within the fine-tuning range, to address the nonlinearity and time-varying nature of leakage current conditions, fuzzy logic is introduced to adaptively tune the PI parameters online. The specific implementation includes the following steps: Using voltage deviation and its rate of change as inputs to the fuzzy controller, they are mapped onto the corresponding fuzzy universe of discourse to obtain fuzzy variables E and EC. In this embodiment, the maximum deviation is taken as 50V, and the maximum deviation change rate is taken as 100V / s based on the system's dynamic characteristics, thus obtaining the quantization factor. =0.02, =0.01; The fuzzy universes of E and EC are divided into seven fuzzy subsets: {Negative Large (NB), Negative Medium (NM), Negative Small (NS), Zero (ZO), Positive Small (PS), Positive Medium (PM), Positive Large (PB)}, where each subset is described by a Gaussian membership function; In fuzzy adaptive PI control, the domain of the input variable is usually normalized to a symmetric interval. When the universe of discourse is [-1, 1], the center values ​​of each fuzzy subset, i.e., the peak points of the membership function, correspond to the following values: NB (negative large): -1.0; NM (negative medium): -0.67; NS (negative small): -0.33; ZO (zero): 0; PS (positive small): 0.33; PM (positive medium): 0.67; PB (positive large): 1.0. If other universes of discourse are used, the values ​​can be scaled proportionally. For example, when the universe of discourse is [-3, 3], the above values ​​can be multiplied by 3. Fuzzy rules are constructed based on expert experience. The specific rule table is shown in Table 1. The rule tables can be similarly constructed, and the two are either symmetrical or complementary: Table 1: Fuzzy Rule Table

[0041] Each element in the table represents A fuzzy subset, such as PB representing a positive large correction and ZO representing a zero correction, when E is NB and EC is NB. When PB is chosen, meaning that both the deviation and the rate of change are negative, the proportional coefficient needs to be increased significantly to achieve a rapid response. Based on the preset fuzzy rule table, Mamdani-type fuzzy inference is performed to obtain the proportional coefficient correction amount. and integral coefficient correction amount The blurred output is then deblurred using the centroid method to obtain the precise correction amount:

[0042]

[0043] in, This indicates that in the i-th rule, the output variable... The membership degree is obtained by taking the minimum value of the input membership degree and then using Mamdani inference. This indicates that in the j-th rule, the output variable... membership degree This indicates the output variable in the i-th rule. The center value of the fuzzy subset, This indicates the output variable in the i-th rule. The center value of the fuzzy subset; The correction value obtained by defuzzification is added to the initial value to obtain the adaptive PI parameter under the current operating condition. The incremental digital PID algorithm is used to calculate the PWM duty cycle adjustment. Differential adjustments are performed based on the judgment results of different zones: In the coarse adjustment zone, the preset maximum step size adjustment is directly output to quickly bring the leakage voltage close to the preset range; in the fine adjustment zone, the PWM duty cycle adjustment calculated by the incremental digital PID algorithm is used for fine adjustment; in the steady-state zone, if... ,in, If the dead zone threshold is indicated, the PWM duty cycle adjustment is set to 0, and the integral term is frozen to suppress frequent jitter of the PWM pulse width.

[0044] According to the preset voltage range Set partition threshold: , , If the preset voltage range is 5V~250V, then =49V, =12.25V, =2.45V; In step S4, when the PWM pulse width adjustment has reached the preset limit duty cycle, such as 5% to 95%, and the leakage voltage is still lower than the preset reference value, it is determined that the system is in an input power limited state. At this time, the auxiliary adjustment mechanism is activated: the control unit abandons the voltage closed-loop control and instead executes the maximum power point tracking (MPPT) strategy. By slightly perturbing the duty cycle and observing the changes in input power, the leakage energy extraction efficiency is maximized. At the same time, the grid current amplitude setpoint is limited to a safe value that matches the current maximum input power to avoid forcibly increasing the power and causing the system to crash. When the leakage voltage rises and stabilizes within the preset range, or when the leakage current increases and indicates that the input power is sufficient, the MPPT mode is exited and normal voltage regulation closed-loop control is restored.

[0045] The system presets a leakage current start threshold and a leakage current power limit threshold. The start threshold is the minimum leakage current value required for the leakage current inverter boost grid-connected circuit to maintain the minimum power output, which is 10% to 20% of the circuit's rated leakage current. The power limit threshold is the maximum leakage current value corresponding to the circuit's rated output power, which does not exceed 120% of the rated leakage current. The system performs a logical comparison between the real-time leakage current and the two thresholds and executes the corresponding safety protection actions.

[0046] In step S5, the specific safety protection action includes: When the leakage current is lower than the starting threshold, it is determined that the leakage energy is insufficient to support the inverter boost grid connection, the circuit is prohibited from starting and the bypass safety circuit is connected. When the leakage current exceeds the power limit threshold, it is determined to be an overload state, and the PWM output is immediately blocked, the inverter boost grid-connected circuit is shut down, and the bypass safety circuit is simultaneously connected. When the leakage current is between the start-up threshold and the upper limit threshold, the system maintains normal inverter boost grid-connected operation.

[0047] When the leakage current is lower than the start-up threshold, the control unit prevents the leakage current inverter boost grid-connected circuit from starting and simultaneously outputs a control signal to connect the bypass safety circuit, directing the leakage voltage to a preset safe discharge path to prevent the circuit from running dry and being damaged. When the leakage current exceeds the upper limit of the power threshold, the control unit immediately outputs a control signal to shut down the power output of the leakage current inverter boost grid-connected circuit and simultaneously connects the bypass safety circuit to ensure that the leakage voltage drops to a safe range below 36V within 10ms, thus avoiding damage to the circuit module and safety accidents such as electric shock and fire. After the bypass safety circuit is turned on, the detection and acquisition circuit continuously collects leakage current and leakage voltage parameters and feeds them back to the control unit in real time, so that the control unit can monitor parameter changes and prepare for system recovery.

[0048] The control unit continuously monitors leakage current and leakage voltage parameters. When both return to the preset normal range, that is, when the actual value of leakage current returns to the normal range between the start-up threshold and the upper power limit threshold, and the actual value of leakage voltage returns to the preset voltage range, the control unit outputs a control signal, disconnects the bypass safety circuit, restarts the leakage current inverter boost grid-connected circuit, and synchronously adjusts parameters such as PWM pulse width, so that the system returns to the normal working state of leakage current inverter boost voltage regulation grid-connected circuit and leakage current return recovery, forming an automated closed-loop control of detection-adjustment-protection-recovery.

[0049] During the inverter boost grid connection control process, the control unit synchronously outputs control signals to control the leakage current return path and the inverter boost grid connection path to work together. It detects the leakage current that has not been connected to the grid in real time and returns the part of the leakage current that has not been connected to the grid to the preset circuit. This realizes the dual functions of leakage current return and recovery and inverter boost grid connection utilization, further improving the leakage current recovery and utilization rate and reducing energy waste.

[0050] like Figure 3 As shown, a leakage current inverter boost grid-connected control and safety protection system is used to implement any of the leakage current inverter boost grid-connected control and safety protection methods described in the figure, comprising: The leakage current acquisition and preprocessing unit has an input terminal that is electrically connected to the leakage voltage. It contains a multi-stage step-down circuit and an adaptive impedance matching network. The output terminal outputs the AC leakage voltage signal after step-down and impedance matching. The rectifier, filter and voltage regulator unit is electrically connected to the output of the leakage current acquisition and preprocessing unit. It integrates a rectifier circuit, a filter circuit and a DC-DC voltage regulator converter, and outputs a stable DC input voltage. The leakage current inverter boost grid-connected unit has its input terminal electrically connected to the output terminal of the rectifier, filter and voltage regulator unit, and its output terminal electrically connected to the grid interface and the leakage current return unit, respectively. It is used to invert DC voltage into AC voltage and complete the boost, phase-locking and grid-connected power supply. The full-range parameter detection unit includes a voltage sensor, a current sensor, and a signal conditioning circuit. The acquisition end is electrically connected to the leakage voltage input end, the leakage current loop, the output end of the rectification, filtering and voltage regulation unit, the output end of the inverter unit, and the grid-connected side. The output end outputs digital electrical parameters. The central control unit, with a digital signal processor or field programmable gate array as its core, has its input terminal electrically connected to the output terminal of the global parameter detection unit, and its output terminal electrically connected to the control terminals of the leakage current inverter boost grid-connected unit, the bypass safety execution unit, and the leakage current return unit, forming an information closed-loop control circuit. The bypass safety actuator has its input terminal electrically connected to the leakage voltage, its output terminal electrically connected to the preset safety discharge path, and its controlled terminal electrically connected to the central control unit. Under the control of the central control unit, it realizes the safe discharge of leakage voltage. The leakage current return unit has its input end electrically connected to the output end of the leakage current inverter boost grid-connected unit, its output end electrically connected to the system's preset return bus or energy storage link, and its controlled end electrically connected to the central control unit. Under the control of the central control unit, leakage current energy is recovered and utilized. The central control unit acquires the electrical parameters of each unit in real time through the global parameter detection unit, processes them through an internal algorithm, and sends control commands to each execution unit. The state changes of each execution unit are fed back to the central control unit through the global parameter detection unit, forming a complete closed-loop control system.

[0051] The central control unit specifically includes: The variable step size adaptive PID voltage regulation control module is used to execute the closed-loop voltage regulation control algorithm; The dual-threshold safety protection module is used to execute the leakage current dual-threshold protection logic; The leakage current return and collaborative scheduling module is used to perform dynamic allocation of power ratios.

[0052] The bypass safety execution unit uses a solid-state relay or thyristor switching circuit; the leakage current return unit integrates a bidirectional DC-DC converter to support bidirectional flow of leakage energy to a preset circuit and voltage matching.

[0053] The embodiments described herein are merely preferred embodiments of the invention and are not intended to limit the concept and scope of the invention. Any modifications and improvements made by those skilled in the art to the technical solutions of the invention without departing from the design concept of the invention should fall within the protection scope of the invention.

Claims

1. A method for leakage current inverter boost grid connection control and safety protection, characterized in that, Includes the following steps: Step S1: Perform multi-stage voltage reduction processing on the input leakage voltage of the device casing; Step S2: Perform AC-DC conversion, filtering, and voltage regulation on the stepped-down AC leakage voltage to output a stable DC input voltage; Step S3: By linking the detection and acquisition circuit with the leakage current inverter boost grid-connected circuit, electrical parameters including at least leakage voltage, leakage current, grid-connected power and PWM pulse width are collected in real time and synchronously. Step S4: Compare the real-time leakage voltage with the preset voltage range, and dynamically adjust the PWM pulse width of the leakage current inverter boost grid-connected circuit based on the algorithm to form a closed-loop voltage regulation control loop for leakage voltage. Step S5: Preset the leakage current start threshold and leakage current power upper limit threshold, compare them with the real-time leakage current, and execute the corresponding safety protection action according to the comparison result. Step S6: Continuously monitor the leakage voltage and leakage current parameters. When both return to the preset normal range, control the disconnection of the bypass safety circuit, restart the leakage current inverter boost grid-connected circuit, and restore the normal working state of the system. Step S7: Based on the real-time grid-connected power and the output capacity of the leakage current inverter boost grid-connected circuit, dynamically allocate the power ratio between the leakage current return path and the inverter boost grid-connected path, and return the leakage current energy that has not been connected to the grid to the preset circuit.

2. The method according to claim 1, characterized in that, In step S1, the multi-stage voltage reduction process specifically includes: The first stage of processing is bidirectional semiconductor limiting processing: a bidirectional transient voltage suppression device is connected in parallel at the leakage voltage input terminal to clamp the amplitude of the input leakage voltage to within a preset first safety threshold. The second stage of processing involves bridge rectification and composite filtering: the limited AC leakage voltage is input into the full-bridge rectifier circuit and converted into a pulsating DC voltage, which is then connected to an LC filter composed of a series inductor and a parallel capacitor to output a DC voltage. The third stage of processing involves switching boost and dynamic impedance matching: the filtered DC voltage is input to the Boost circuit, while the control unit identifies the equivalent impedance model of the leakage path online based on the real-time collected drain-source voltage and leakage current, and dynamically adjusts the input impedance of the Boost circuit according to the identification results, so that the leakage energy extraction efficiency meets the preset maximum power point tracking target, and finally outputs a stable DC voltage that is compatible with the subsequent inverter circuit.

3. The method according to claim 2, characterized in that, In step S2, a DC-DC converter is used to regulate the filtered DC voltage so that the output DC voltage matches the input requirements of the subsequent circuit. The filtering is performed using a combination of capacitor filtering and inductor filtering. Specifically, a multi-stage composite filter network is constructed between the output of the rectifier circuit and the input of the DC-DC converter. The multi-stage composite filter network includes: a first-stage filter unit composed of electrolytic capacitors, used to filter out low-frequency ripple after rectification; a second-stage filter unit composed of a differential-mode inductor and a high-frequency ceramic capacitor forming an LC series branch, used to suppress high-frequency noise; and a third-stage filter unit composed of the input and output capacitors of the Boost circuit itself, forming a cascaded filter structure.

4. The method according to claim 3, characterized in that, In the multi-stage voltage reduction process, the third stage specifically includes the following steps: An equivalent impedance model of the leakage current channel is constructed. The instantaneous sampled values ​​of leakage voltage and leakage current are used as inputs. The recursive least squares algorithm is used for online iterative calculation to identify the equivalent resistance and equivalent inductance parameters of the leakage current channel in real time. Based on the maximum power transfer theorem, and using the identified equivalent resistance and equivalent inductance as a basis, the optimal input impedance of the Boost circuit that maximizes the leakage energy transfer efficiency is calculated. The optimal input impedance is the complex conjugate of the equivalent impedance of the leakage channel, that is, the equivalent resistance minus the inductive reactance component of the equivalent inductance. The control unit dynamically adjusts the duty cycle of the switching transistor in the Boost circuit according to the calculated optimal input impedance, so that the equivalent input impedance of the Boost circuit tracks the optimal input impedance in real time, thereby achieving impedance matching between the leakage path and the Boost circuit. While achieving impedance matching, the Boost circuit maintains stable output voltage through duty cycle adjustment, ultimately outputting a stable DC voltage that is compatible with the subsequent inverter circuit.

5. The method according to claim 4, characterized in that, In step S4, the dynamic adjustment of the PWM pulse width of the leakage current inverter boost grid-connected circuit based on the algorithm specifically includes the following steps: Calculate the deviation between the actual value of leakage voltage and the preset reference value and its rate of change. Based on the absolute value of the deviation, divide the adjustment process into coarse adjustment zone, fine adjustment zone and steady state zone. Within the fine-tuning range, the deviation and its rate of change are input into the fuzzy controller. After fuzzification, fuzzy inference, and defuzzification, the correction values ​​of the proportional coefficient and integral coefficient are output to perform online adaptive tuning of the PI parameters. An incremental PID algorithm is used to calculate the adjustment of the PWM pulse width, where the proportional coefficient and integral coefficient are the values ​​after fuzzy adaptive tuning; Based on the partitioning results, variable step size adjustment is performed: the coarse adjustment zone uses the maximum step size for fast response, the fine adjustment zone uses incremental PID calculation values ​​for fine adjustment, and the steady-state zone introduces dead zone control and freezes the integral term to suppress frequent jitter of PWM pulse width.

6. The method according to claim 5, characterized in that, In step S4, when the PWM pulse width adjustment has reached the preset limit duty cycle and the leakage voltage is still lower than the preset reference value, it is determined that the system is in an input power limited state, and the auxiliary adjustment mechanism is activated: the control unit abandons the voltage closed-loop control and instead executes the maximum power point tracking strategy, adjusting the duty cycle through the perturbation observation method to maximize the leakage energy extraction efficiency; at the same time, the grid current amplitude setpoint is limited to a safe value that matches the current maximum input power; when the leakage voltage rises back to the preset range or the leakage current increases to meet the power demand, the maximum power point tracking mode is exited and the voltage regulation closed-loop control is restored.

7. The method according to claim 6, characterized in that, In step S5, the specific safety protection action includes: When the leakage current is lower than the starting threshold, it is determined that the leakage energy is insufficient to support the inverter boost grid connection, the circuit is prohibited from starting and the bypass safety circuit is connected. When the leakage current exceeds the power limit threshold, it is determined to be an overload state, and the PWM output is immediately blocked, the inverter boost grid-connected circuit is shut down, and the bypass safety circuit is simultaneously connected. When the leakage current is between the start-up threshold and the upper limit threshold, the system maintains normal inverter boost grid-connected operation.

8. A leakage current inverter boost grid-connected control and safety protection system, used to implement the leakage current inverter boost grid-connected control and safety protection method as described in any one of claims 1-7, characterized in that, include: The leakage current acquisition and preprocessing unit has an input terminal that is electrically connected to the leakage voltage. It contains a multi-stage step-down circuit and an adaptive impedance matching network. The output terminal outputs the AC leakage voltage signal after step-down and impedance matching. The rectifier, filter and voltage regulator unit is electrically connected to the output of the leakage current acquisition and preprocessing unit. It integrates a rectifier circuit, a filter circuit and a DC-DC voltage regulator converter, and outputs a stable DC input voltage. The leakage current inverter boost grid-connected unit has its input terminal electrically connected to the output terminal of the rectifier, filter and voltage regulator unit, and its output terminal electrically connected to the grid interface and the leakage current return unit, respectively. It is used to invert DC voltage into AC voltage and complete the boost, phase-locking and grid-connected power supply. The full-range parameter detection unit includes a voltage sensor, a current sensor, and a signal conditioning circuit. The acquisition end is electrically connected to the leakage voltage input end, the leakage current loop, the output end of the rectification, filtering and voltage regulation unit, the output end of the inverter unit, and the grid-connected side. The output end outputs digital electrical parameters. The central control unit, with a digital signal processor or field programmable gate array as its core, has its input terminal electrically connected to the output terminal of the global parameter detection unit, and its output terminal electrically connected to the control terminals of the leakage current inverter boost grid-connected unit, the bypass safety execution unit, and the leakage current return unit, forming an information closed-loop control circuit. The bypass safety actuator has its input terminal electrically connected to the leakage voltage, its output terminal electrically connected to the preset safety discharge path, and its controlled terminal electrically connected to the central control unit. Under the control of the central control unit, it realizes the safe discharge of leakage voltage. The leakage current return unit has its input end electrically connected to the output end of the leakage current inverter boost grid-connected unit, its output end electrically connected to the system's preset return bus or energy storage link, and its controlled end electrically connected to the central control unit. Under the control of the central control unit, leakage current energy is recovered and utilized. The central control unit acquires the electrical parameters of each unit in real time through the global parameter detection unit, processes them through an internal algorithm, and sends control commands to each execution unit. The state changes of each execution unit are fed back to the central control unit through the global parameter detection unit, forming a complete closed-loop control system.

9. The system according to claim 8, characterized in that, The central control unit specifically includes: The variable step size adaptive PID voltage regulation control module is used to execute the closed-loop voltage regulation control algorithm; The dual-threshold safety protection module is used to execute the leakage current dual-threshold protection logic; The leakage current return and collaborative scheduling module is used to perform dynamic allocation of power ratios.

10. The system according to claim 8, characterized in that, The bypass safety execution unit uses a solid-state relay or thyristor switching circuit; the leakage current return unit integrates a bidirectional DC-DC converter to support bidirectional flow of leakage energy to a preset circuit and voltage matching.

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