CN-122001230-A - Hydrogen production power supply current sharing control method with self-adaptive virtual impedance

CN122001230ACN 122001230 ACN122001230 ACN 122001230ACN-122001230-A

Abstract

The invention discloses a flow equalizing control method of a hydrogen production power supply with self-adaptive virtual impedance, which belongs to the technical field of water electrolysis hydrogen production power supply control and comprises the steps of respectively collecting output currents of all groups of parallel branches of four groups of isolated half-bridge LLC cascade Buck parallel hydrogen production power supply systems, calculating average output currents and circulation currents of all groups of parallel branches, designing smooth continuous nonlinear functions containing hyperbolic tangent terms, arctangent terms and exponential decay terms, constructing the self-adaptive virtual impedance by taking the smooth continuous nonlinear functions as self-adaptive coefficient functions, dynamically matching equivalent impedance changes of a PEM electrolytic tank in a current density interval, integrating the self-adaptive virtual impedance into a circulation feedforward correction link to construct a corrected voltage reference value, and combining voltage-current double closed-loop control of a later-stage Buck converter to adjust the output currents of all groups of parallel branches in real time. The invention realizes the smooth adjustment of the virtual impedance, so that the transition of the system is more gentle when the power fluctuates.

Inventors

CHEN QUAN
QIAN JUN
LI GUOLI
XU JIAZI
LIU GUOHUA
WANG QUNJING

Assignees

安徽大学

Dates

Publication Date: 20260508
Application Date: 20260209

Claims (10)

1. A hydrogen production power supply current sharing control method of self-adaptive virtual impedance is characterized by comprising the following steps: S1, respectively collecting output currents of all groups of parallel branches of four groups of isolated half-bridge LLC cascade Buck parallel hydrogen production power supply systems, and calculating average output currents and circulation currents of all groups of parallel branches; S2, designing a smooth continuous nonlinear function containing a hyperbolic tangent term, an arctangent term and an exponential decay term; s3, taking the smooth continuous nonlinear function designed in the S2 as a self-adaptive coefficient function, constructing self-adaptive virtual impedance, and dynamically matching the equivalent impedance change of the PEM electrolytic cell in a current density interval; s4, integrating the self-adaptive virtual impedance into a loop feedforward correction link to construct a corrected voltage reference value, and combining voltage and current double closed-loop control of a back-stage Buck converter to adjust the output current of each group of parallel branches in real time so as to realize accurate distribution of the current among each group of parallel branches.
2. The adaptive virtual impedance hydrogen production power supply current sharing control method according to claim 1, wherein in S1, the isolated half-bridge LLC cascade Buck parallel hydrogen production power supply system comprises a direct current power supply, four groups of parallel branches and a PEM electrolytic tank, wherein the output end of the direct current power supply is connected with the input ends of the four groups of parallel branches in parallel, and the output ends of the four groups of parallel branches are commonly connected with the input end of the PEM electrolytic tank.
3. The adaptive virtual impedance hydrogen generation power supply current sharing control method according to claim 2, wherein in S1, each group of parallel branches has the same structure and comprises a front-stage isolation type half-bridge LLC resonant converter and a rear-stage Buck converter.
4. The method for current sharing control of a hydrogen generation power supply with self-adaptive virtual impedance as set forth in claim 3, wherein in S1, each group of parallel branches of the front-stage isolation type half-bridge LLC resonant converter comprises a first MOS transistor Q 11 , a second MOS transistor Q 12 , a resonant inductor L r1 , Resonance capacitor C r1 , exciting inductance L m1 , transformer T 1 , first diode D 11 , second diode D 12 , A third diode D 13 , a fourth diode D 14 , and an output filter capacitor C 1 ; two output ends of the direct current power supply are respectively connected with the drain electrode of the first MOS tube Q 11 , The source electrode of the second MOS tube Q 12 , the first diode D 11 and the second diode D 12 are respectively connected in anti-parallel with the two ends of the first MOS tube Q 11 and the second MOS tube Q 12 , the source electrode of the first MOS tube Q 11 is connected with the drain electrode of the second MOS tube Q 12 and then connected with one end of a resonant capacitor C r1 , the other end of the resonant capacitor C r1 is connected with one end of a resonant inductor L r1 , the other end of the resonant inductor L r1 is connected with one end of a primary winding of a transformer T 1 , the other end of the primary winding of the transformer T 1 is connected with the source electrode of the second MOS tube Q 12 , an excitation inductor L m1 is connected with the two ends of the primary winding of the transformer T 1 in parallel, the two ends of a secondary winding of the transformer T 1 are respectively connected with the anodes of a third diode D 13 and a fourth diode D 14 , the third diode D 13 is connected with the cathode electrode of the fourth diode D 14 and then connected with one end of a filter capacitor C 1 , the other end of the filter capacitor C 1 is connected with the center point of a secondary winding of the transformer T 1 , and the primary winding of the transformer is electrically isolated from the secondary winding, and the primary bridge is converted to realize primary conversion; The back-stage Buck converter of each group of parallel branches consists of a third MOS tube Q 1 , a fifth diode D 15 , a sixth diode D 16 , an output filter inductor L 1 and an output filter capacitor C o1 , wherein the output end of the front-stage isolation type half-bridge LLC resonant converter, namely, two ends of the filter capacitor C 1 are respectively connected with the drain electrode of the third MOS tube Q 1 and the anode of the sixth diode D 16 , the source electrode of the third MOS tube Q 1 is connected with the cathode of the sixth diode D 16 and then is connected with one end of the output filter inductor L 1 , the fifth diode D 15 is connected in anti-parallel with two ends of the third MOS tube Q 1 , the other end of the output filter inductor L 1 is connected with one end of the output filter capacitor C o1 , and the other end of the output filter capacitor C o1 is connected with the anode of the sixth diode D 16 .
5. The adaptive virtual impedance hydrogen generation power supply current sharing control method as claimed in claim 4, wherein the pre-isolated half-bridge LLC resonant converter adopts open loop control.
6. The adaptive virtual impedance hydrogen generation power supply current sharing control method according to claim 2, wherein S1 comprises: S11, respectively collecting output currents of parallel branches of four groups of isolated half-bridge LLC cascade Bucks, and calculating average output currents : ; In the formula, For the output currents of the parallel branches of each group, Numbering parallel branches, wherein the values are 1, 2, 3 and 4; s12, respectively mixing the output currents of parallel branches of each group of isolated half-bridge LLC cascade Bucks with the average output current Calculating the circulation of each group of parallel branches by difference : 。
7. The adaptive virtual impedance hydrogen generation power supply current sharing control method as in claim 6, wherein in S2, a smooth continuous nonlinear function containing hyperbolic tangent term, arctangent term and exponential decay term is designed : ; In the formula, Electrolyzing the current for a PEM electrolyzer; Taking 0.8 as the lower limit value of the nonlinear function; For the amplitude calibration factor to be a factor, An electrolysis current at the inflection point of the V-I characteristic curve of the PEM electrolyzer; , , respectively hyperbolic tangent term coefficient, arctangent term coefficient and exponential decay term coefficient, for regulating function Shape and rate of change over different current intervals.
8. The adaptive virtual impedance hydrogen generation power supply current sharing control method as claimed in claim 7, wherein in S2, PEM electrolyzer V-I characteristics are: ; in the formula, For a single PEM electrolyser port voltage, In order to open the reversible voltage of the circuit, Is a gas constant which is a function of the gas, The reaction temperature in the tank; As a function of the charge transfer coefficient, Is a function of the faraday constant, In order to exchange the current density of the current, In order to achieve a current density of the material, Is the equivalent resistance of the proton exchange membrane, Is an anti-hyperbolic sine function.
9. The adaptive virtual impedance hydrogen generation power supply current sharing control method as claimed in claim 8, wherein S3 comprises: s31, calculating rated equivalent impedance of single parallel branch : ; In the formula, In order to be a resonant inductance, In the form of a resonant capacitor, For the excitation of the inductance, In order to achieve the transformation ratio of the transformer, The filter inductance is output for the back-stage Buck converter, For the parasitic resistance of the output filter inductance, The filter capacitor is output for the back-stage Buck converter, Is a complex frequency domain variable; s32, determining a virtual impedance basic value; Defining an equivalent impedance impact factor The expression is: ; in the formula, Is the equivalent impedance variation among the parallel branches caused by component parameter tolerance, , For electrolytic current of The total equivalent impedance of the PEM electrolyzer, Is a virtual impedance base value; when equivalent impedance changes At the position of When the interval changes, a factor capable of enabling the equivalent impedance to influence is selected Virtual impedance base value varying in section as virtual impedance base value ; S33, constructing self-adaptive virtual impedance Is the virtual impedance basic value And smooth continuous nonlinear function Is the product of: ; When the PEM electrolyzer is operated in the low current density region, Smaller, so that Smaller and when the PEM electrolyzer is operating in the high current density region, Substantially unchanged by Dynamically matching equivalent impedance changes within the PEM electrolyzer current density interval.
10. The adaptive virtual impedance hydrogen generation power supply current sharing control method as claimed in claim 9, wherein S4 comprises: S41, integrating the self-adaptive virtual impedance into a loop feedforward correction link to construct a corrected voltage reference value; Storing the S33 constructed calculation function of the adaptive virtual impedance Collecting the electrolytic current of PEM electrolyzer in real time, calculating real-time virtual impedance value, multiplying the calculated virtual impedance value by each group of parallel branch loop current, and outputting voltage given value to original hydrogen production power supply Performing correction to generate the first Corrected voltage reference value for group parallel branch : ; In the formula, Outputting a voltage given value for an original hydrogen production power supply; S42, collecting output voltages of four groups of isolated half-bridge LLC cascade Buck parallel hydrogen production power supply systems, and calculating inductance current reference values of each group of parallel branch post-stage Buck converters through a voltage outer ring; Collecting output voltage of hydrogen production power supply system by voltage sensor Calculating the corrected voltage reference value of each group of parallel branches And (3) with The deviation of the inductance current reference value of the parallel branch post-stage Buck converter is output through a voltage outer loop PI regulator ; S43, respectively collecting inductance currents of four groups of back-stage Buck converters, and calculating PWM duty ratio signals of the back-stage Buck converters of each parallel branch through a current inner loop; Inductance current of four groups of later-stage Buck converters is respectively collected by adopting current sensors Calculating inductance current reference value of each group of parallel branches And (3) with The deviation outputs PWM duty ratio signals of the back-stage Buck converters of the group of parallel branches through the current inner loop PI regulator; S44, PWM duty ratio signals of the rear-stage Buck converters of the parallel branches of each group are input to a PWM generator to obtain PWM square wave signals of the rear-stage Buck converters of the parallel branches of each group, the MOS tube in the rear-stage Buck converters of the parallel branches of each group is driven to be turned on and off, and output voltage and current of each group of parallel branches are dynamically adjusted.

Description

Hydrogen production power supply current sharing control method with self-adaptive virtual impedance Technical Field The invention belongs to the technical field of hydrogen production power supply control by water electrolysis, and particularly relates to a hydrogen production power supply current sharing control method with self-adaptive virtual impedance. Background The new energy water electrolysis hydrogen production becomes a key technical path for breaking the dilemma of intermittent new energy such as photovoltaic, wind energy and the like and realizing on-site digestion. The hydrogen production power supply is used as a core component of the water electrolysis hydrogen production system, and the working requirements of large current, low ripple and wide voltage adaptation of a PEM (proton exchange membrane) electrolytic tank are required to be met. In order to improve the power level and reliability of the power supply, a multi-module parallel architecture is widely adopted in industry, and a four-group isolation type half-bridge LLC (double-inductance single-capacitance resonant converter) cascading Buck (Buck converter) parallel scheme becomes the preferred topology of the medium-high power hydrogen production power supply due to the advantages of high power density, soft switching characteristics, electrical isolation and the like. However, due to the influence of LLC resonance parameter tolerance and Buck circuit inductance parasitic resistance difference, the equivalent output impedance of each module is inconsistent, so that current distribution is uneven, the modules with larger current can bear too high thermal stress, the service life of the devices is shortened, and even module faults are caused. The existing hydrogen production power supply current sharing technology is mostly applied to hydrogen production power supplies of isolated half-bridge LLC topology, PEM electrolytic tanks are often equivalent to linear loads, fixed virtual impedance is adopted to be connected in series in a module equivalent circuit, and the current sharing is realized by increasing total impedance to reduce the influence of equivalent impedance change caused by parameter difference on the total impedance. In practice, however, PEM electrolyzers are loads with significant non-linear characteristics that have a large equivalent impedance in the low current density region and a small equivalent impedance in the high current density region, and the use of a fixed virtual impedance results in an excessive total impedance in the low current density region, affecting the dynamic response of the system. Therefore, a current sharing control method capable of dynamically adapting to four groups of isolated half-bridge LLC cascade Buck parallel hydrogen production power supply systems with a nonlinear load of a PEM electrolytic cell is needed. Disclosure of Invention In order to solve the technical problems, the invention adopts the following technical scheme: A hydrogen production power supply current sharing control method of self-adaptive virtual impedance comprises the following steps: S1, respectively collecting output currents of all groups of parallel branches of four groups of isolated half-bridge LLC cascade Buck parallel hydrogen production power supply systems, and calculating average output currents and circulation currents of all groups of parallel branches; S2, designing a smooth continuous nonlinear function containing a hyperbolic tangent term, an arctangent term and an exponential decay term; s3, taking the smooth continuous nonlinear function designed in the S2 as a self-adaptive coefficient function, constructing self-adaptive virtual impedance, and dynamically matching the equivalent impedance change of the PEM electrolytic cell in a current density interval; s4, integrating the self-adaptive virtual impedance into a loop feedforward correction link to construct a corrected voltage reference value, and combining voltage and current double closed-loop control of a back-stage Buck converter to adjust the output current of each group of parallel branches in real time so as to realize accurate distribution of the current among each group of parallel branches. The invention has the following beneficial effects: The invention aims to solve the problem that the output current of four groups of isolated half-bridge LLC cascade Buck parallel hydrogen production power supply systems is not uniform by introducing virtual impedance into a loop feedforward correction link to correct the original hydrogen production power supply output voltage given value and combining voltage and current double closed loop control, avoid the problem that a single parallel branch in the hydrogen production power supply system bears too high thermal stress due to overlarge current, prolong the service life of a device, dynamically adapt the equivalent impedance change of a PEM electrolytic tank in different current density intervals