A method for active harmonic suppression and optimization of water electrolysis hydrogen production rectifier transformer

Abstract

The application discloses a kind of water electrolysis hydrogen production rectifier transformer harmonic active inhibition optimization method, comprising the following steps: constructing rectifier circuit, rectifier circuit includes switch tube, the voltage vector and zero vector of switch tube output are combined, and combined output voltage vector is obtained;The harmonic amplitude is obtained by processing combined output voltage vector, Levy tangent flight strategy and confidence domain variation strategy are introduced in black-winged kite optimization algorithm to construct improved dynamic search algorithm, the total harmonic distortion is obtained by iterative calculation of harmonic amplitude by improved dynamic search algorithm, i.e. optimal switch tube combination, the switch tube of rectifier circuit is adjusted by optimal switch tube combination, and the total harmonic distortion of rectifier circuit is reduced.The optimal switch tube combination of rectifier circuit is iteratively calculated by improved dynamic search algorithm in the application, effectively reduces resource consumption, and processing speed is accelerated, and the efficiency and accuracy of electrolytic water hydrogen production rectifier are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of rectifier transformer harmonics, and in particular to a water electrolysis hydrogen production rectifier transformer harmonic active suppression optimization method. BACKGROUND

[0002] As a secondary energy source, hydrogen energy has many advantages: it can be stored and used for long-distance transmission, and it can be efficiently converted into electrical and thermal energy; its energy density is very high; its final product is water, and it does not produce other pollutants; in addition, hydrogen has a wide range of applications in the industrial field and is a key raw material.

[0003] Harmonic pollution not only seriously affects the power quality of the power grid, reduces the generation, transmission and utilization efficiency of electrical energy, but also harms electrical equipment, increases system loss, reduces system power factor, accelerates the aging of cable and wire insulation medium, and causes problems such as line short circuit, ground fault and protection circuit malfunction.

[0004] The active harmonic suppression method considers the specific rectifier device itself, improves the rectifier topology structure, and reduces or eliminates the generation of harmonics. From a technical point of view, this method can be further divided into PWM rectification technology and multi-pulse rectification technology. The goal of PWM is to eliminate specific secondary harmonics and ensure that certain low-frequency harmonics are completely filtered out, but it does not limit the amplitude of total harmonic distortion (THD) and other harmonics. All constraints are equality constraints, so the solution process is relatively simple. On the other hand, the latter requires the amplitude of all odd harmonics to meet the grid standard, and the constraints include both equations and inequalities, and pursues the lowest THD value, taking the minimization of THD as the optimization goal. Therefore, studying how to suppress harmonics to improve its generalization ability, reduce resource consumption, and speed up processing speed plays an important role in improving the efficiency and accuracy of water electrolysis hydrogen production rectifiers. SUMMARY

[0005] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present application provide a water electrolysis hydrogen production rectifier transformer harmonic active suppression optimization method, which solves the problems mentioned in the background art.

[0006] To achieve the above object, the present application provides the following technical scheme: a water electrolysis hydrogen production rectifier transformer harmonic active suppression optimization method, comprising the following steps:

[0007] Step S1: constructing a rectifier circuit, the rectifier circuit comprising a switch tube, combining the voltage vector and the zero vector output by the switch tube to obtain a combined output voltage vector; processing the combined output voltage vector to obtain a harmonic amplitude;

[0008] Step S2: Levy tangent flight strategy and trust region mutation strategy are introduced into the black-winged kite optimization algorithm to construct an improved dynamic search algorithm;

[0009] Step S3: the improved dynamic search algorithm is used to iteratively calculate the harmonic amplitude, and the total harmonic distortion rate is obtained, that is, the optimal switch tube combination, and the switch tube of the rectifier circuit is adjusted through the optimal switch tube combination to reduce the total harmonic distortion rate of the rectifier circuit.

[0010] Further, the rectifier circuit comprises an SVPWM circuit; the SVPWM circuit is divided into a plurality of sectors, each sector contains a switch tube, and also includes a voltage space vector rotation angle, the voltage vectors output by the switch tubes in the plurality of sectors are combined with zero vectors to obtain a combined output voltage vector; r is the voltage space vector rotation angle; to combine the output voltage vector; wherein the SVPWM circuit comprises a phase a capacitor midpoint voltage; .

[0011] Further, based on the combined output voltage vector, let the switching period be T s , which represents:

[0012] (1);

[0013] In the formula, ; represents a zero vector; represents a first zero vector; represents a second zero vector; represents the action time of the first zero vector U1; represents the action time of the second zero vector . represents the action time of the zero vector .

[0014] Solve the values of T1 and T2, which represent:

[0015] (2);

[0016] (3);

[0017] (4);

[0018] In the formula, represents the modulation index; represents the direct current voltage; represents a sine function; represents a cosine function.

[0019] Further, the specific process of obtaining the harmonic amplitude is as follows:

[0020] In the process of calculating the harmonic amplitude of the SVPWM circuit, the Fourier decomposition of the point voltage is performed based on the combined output voltage vector, which is expressed as:

[0021] (5);

[0022] Where, Indicates point voltage over time The changing voltage waveform; Indicates the average value of the point voltage; Indicates infinity; Indicates the harmonic order; Indicates the fundamental angular frequency; and denote the amplitudes of the corresponding cosine and sine terms respectively; ; is the fundamental frequency;

[0023] The point voltage is an even function, which means:

[0024] (6);

[0025] (7);

[0026] (8);

[0027] Where, represents a small increment of time;

[0028] Rotation angle of voltage space vector As the boundary, the voltage at the point changes with time The changing voltage waveform In half the output switching period T s Expanded inside, divided into 1 zone and district; is the modulation factor;

[0029] Based on the division into Zone 1 and Assume that the voltage space vector corresponding to the kth region rotates by an angle, which is expressed as:

[0030] (9);

[0031] Where r k is the rotation angle of the voltage space vector corresponding to the kth region; Indicates the rotation angle increment for each interval; Indicates the total number of intervals;

[0032] Assume that the positive level duty ratio of the voltage space vector rotation angle corresponding to the kth region is ,express:

[0033] (10);

[0034] wherein, denotes the last time node in half of the switching period T s the starting time of the time node; denotes the last time node in half of the switching period T s , i.e. the ending time of half of the period T s ; denotes the ending time of the positive duty ratio time node of the voltage space vector rotation angle corresponding to the 1st zone; denotes the positive duty ratio of the voltage space vector rotation angle corresponding to the 1st zone; denotes the ending time of the positive duty ratio time node of the voltage space vector rotation angle corresponding to the 2k−2th zone; denotes the ending time of the positive duty ratio time node of the voltage space vector rotation angle corresponding to the 2k−3th zone; denotes the positive duty ratio of the voltage space vector rotation angle corresponding to the k−1th zone; denotes the ending time of the positive duty ratio time node of the voltage space vector rotation angle corresponding to the 2k−1th zone; denotes the period;

[0035] Based on the positive duty ratio and the period T, the time value is calculated; denotes the time value calculated from the positive duty ratio of the 1st zone and the period T, denotes the time value calculated from the positive duty ratio of the kth zone and the period T;

[0036] Further, the calculated time value is substituted into formula (8), the integral of the time value is expanded, and is calculated, which represents:

[0037] (11);

[0038] wherein, denotes the amplitude of the nth harmonic.

[0039] Further, the specific process of introducing the Levy tangent flight strategy in the black-winged kite optimization algorithm is as follows:

[0040] ​The parameters of the black-winged kite optimization algorithm are set, including the number of black-winged kites, the search space, the total number of iterations, and the leader. A black-winged kite matrix is generated based on the set parameters of the black-winged kite optimization algorithm. After randomly assigning the position of each black-winged kite from the black-winged kite matrix, the initial population is generated using the Tent mapping, and the initial position of the black-winged kite in the initial population is calculated using formula (12), which is represented as:

[0041] (12);

[0042] wherein, represents the initial position of the i-th black-winged kite; and represent the lower and upper bounds of the search space, respectively; () represents a random number between [0, 1];

[0043] The calculation formula of the optimal position y L of the black-winged kite in the initial population is represented as:

[0044] (13);

[0045] (14);

[0046] wherein, represents the optimal fitness value found currently; represents the fitness value of the i-th black-winged kite in the initial population; represents the black-winged kite; represents function; represents the minimum value; represents the fitness value of the i-th black-winged kite at the current position ; and

[0047] The attack strategy updating equation is:

[0048] (15);

[0049] wherein, represents the position of the i-th black-winged kite in the j-th dimension in the t+1-th iteration step; represents the position of the i-th black-winged kite in the j-th dimension in the t-th iteration step; represents a threshold value; represents a random number between 0 and 1 in the initial population; represents a nonlinear factor; ; Q represents the total number of iterations; represents the base of natural logarithm; represents otherwise;

[0050] Black kite migration strategy, indicating:

[0051] (16);

[0052] Where, Represents a random number between 0 and 1, indicating a Cauchy mutation; represents the black kite with the highest score in the j-th dimension in the t-th iteration step; represents the fitness value of the i-th black-winged kite; represents a randomly generated fitness threshold; represents a constant; ;

[0053] The probability density function of the Cauchy mutation is expressed as:

[0054] (17);

[0055] Where, represents the probability density function of the Cauchy distribution; represents the scale parameter; represents a random variable; Represents positional parameters;

[0056] when When , the probability density function becomes the standard form, which is expressed as:

[0057] (18);

[0058] The improved black kite migration strategy, which incorporates the Levy tangent flight strategy algorithm, is expressed as follows:

[0059] (19);

[0060] Where, represents the tangent function; Indicates the flight length.

[0061] Furthermore, the specific process of introducing the prey escape strategy into the black kite optimization algorithm is as follows:

[0062] First, define the prey escape energy of the black kite algorithm, which is expressed as:

[0063] (20);

[0064] Where, It indicates the energy of prey escape; represents the exponential function; Indicates the current number of iterations t and the total number of iterations The ratio of

[0065] when When , it means that the prey does not have excess prey escape energy to escape the attack circle of the black-winged kite. At this time, the original attack strategy of formula (15) is used to update the position of the black-winged kite, where E0 represents the prey escape threshold;

[0066] when When , it means that the prey has enough escape energy to escape the attack of the black kite. At this time, the trust region mutation strategy is introduced into the black kite optimization algorithm to increase the search intensity and prevent the prey from escaping.

[0067] First, define black-winged kite i to black-winged kite The Euclidean distance between them is used to calculate the mean position of all black kites based on the Euclidean distance. , according to the current black-winged kite i and the mean position The distance between them is used to calculate the initial trust region radius, which is expressed as:

[0068] (twenty one);

[0069] Where, Indicates black-winged kite i and black-winged kite The Euclidean distance between represents the Euclidean distance; Represents the coordinate value of the i-th black-winged kite in the first dimension of the multidimensional space; Indicates the The coordinate values ​​of a black kite in the first dimension of the multidimensional space; represents the coordinate value of the i-th black-winged kite in the D-th dimension in the multidimensional space; Indicates the The coordinate value of a black-winged kite in the D-th dimension in multidimensional space; represents the total number of black-winged kites; Indicates black-winged kite i and black-winged kite location; represents the initial trust region radius of the i-th black kite;

[0070] Current Black Winged Kite i to Black Winged Kite The Euclidean distance between them is less than the initial trust region radius of the i-th black kite, and it is regarded as a trustworthy black kite. The mean position of the trustworthy black kite is calculated, which is expressed as:

[0071] (twenty two);

[0072] Where, represents the set of locations of the i-th reliable black kite; represents the position of the i-th trustworthy black kite; represents the mean position of the trustworthy black-winged kite; represents the number of reliable black-winged kite; represents the threshold value of the mean position of the i th reliable black-winged kite;

[0073] The Levy tangent flight strategy is introduced in the attack strategy, which is represented as:

[0074] (23);

[0075] (24);

[0076] In the formula, represents the step size of the Levy tangent flight strategy algorithm; represents a random number normally distributed between 0 and 1; represents the standard deviation; represents the gamma function; represents the conventional parameter;

[0077] The position of the attack strategy is updated by combining the Levy tangent flight strategy and the trust region mutation strategy, which is represented as:

[0078] (25);

[0079] The error of the position of the i th black-winged kite in the j th dimension in the t+1 th iteration after combination is corrected according to the optimal position y L of the black-winged kite in the initial population until the accuracy requirement of the black-winged kite optimization algorithm is met;

[0080] When the black-winged kite optimization algorithm meets the accuracy requirement, the iteration is ended, and the optimal identification parameter is obtained. Otherwise, the initial position of the black-winged kite in the initial population is recalculated in formula (12). Considering that when the black-winged kite optimization algorithm reaches the upper limit of the number of iterations in the iteration process and still does not meet the accuracy requirement, the minimum fitness value of the position of the i th black-winged kite in the j th dimension in the t+1 th iteration after combination in the iteration process is selected as the optimal solution output.

[0081] Further, the specific process of obtaining the total harmonic distortion rate is as follows:

[0082] The n th harmonic amplitude is iteratively calculated by the optimal identification parameter of the improved dynamic search algorithm , which is represented as:

[0083] (26);

[0084] In the formula, represents the first harmonic amplitude; represents the total harmonic distortion rate of the first 50 harmonics of the output voltage; represents the error term of the harmonic amplitude; Indicates pulse edge; Represents the i-th switch tube; is the zeroth harmonic amplitude; represents the error term of the first harmonic amplitude; Z represents the modulation ratio; Indicates voltage; Indicates the correction coefficient or proportional factor; Indicates the 5th harmonic amplitude standard; represents the error term of the 5th harmonic amplitude; Indicates the Subharmonic amplitude standard; Indicates the The error term of the harmonic amplitude; =1,2,3,…,6; =5,7,11,…,49;

[0085] Based on the first 50 harmonic distortion rates of the output voltage Calculate the total harmonic distortion, expressed as:

[0086] (27);

[0087] Where, Indicates total harmonic distortion; Indicates the absolute value of the harmonic amplitude.

[0088] Compared with the existing technology, the present invention has the following beneficial effects:

[0089] (1) The present invention simulates the flight behavior of the black kite by adopting the Levy tangent flight strategy, which can get rid of the dependence on the black kite that has lost its leader role, and is conducive to expanding the search range of the algorithm; the prey escape strategy is introduced to optimize the black kite optimization algorithm, which solves the problem that the black kite optimization algorithm is prone to fall into a local optimal solution in the later stage and cannot quickly converge to the optimal value.

[0090] (2) The present invention maintains a certain exploration capability in the early stage through an improved dynamic search algorithm, thereby effectively reducing the output total harmonic distortion rate and showing strong adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0091] Figure 1 Flow chart of the method of the present invention. DETAILED DESCRIPTION

[0092] like Figure 1 As shown, the present invention provides a technical solution: a method for actively suppressing and optimizing harmonics of a rectifier transformer for water electrolysis hydrogen production, comprising the following steps:

[0093] Step S1: constructing a rectifier circuit, the rectifier circuit including a switch tube, combining a voltage vector output by the switch tube and a zero vector to obtain a combined output voltage vector; processing the combined output voltage vector to obtain a harmonic amplitude;

[0094] Step S2: Introducing the Levy tangent flight strategy and the trust region mutation strategy into the black kite optimization algorithm to construct an improved dynamic search algorithm;

[0095] Step S3: Iteratively calculate the harmonic amplitude through the improved dynamic search algorithm to obtain the total harmonic distortion rate, that is, the optimal switch tube combination. The switch tubes of the rectifier circuit are adjusted through the optimal switch tube combination to reduce the total harmonic distortion rate of the rectifier circuit.

[0096] The rectifier circuit includes an SVPWM circuit; the space vector pulse width modulation SVPWM circuit in the source power filter (APF) is used as the research topology; the SVPWM circuit is divided into 6 sectors, each of which includes 6 switching tubes; the 6 sectors also include the voltage space vector rotation angle, and the voltage vectors output by the switching tubes in the 6 sectors and the zero vector are combined to obtain a combined output voltage vector, wherein the 6 switching tubes output 8 voltage vectors; 2 of the 8 voltage vectors are zero vectors, and the length of the 6 voltage vectors is 2 / 3Udc; r is the voltage space vector rotation angle; is the combined output voltage vector; wherein the SVPWM circuit includes the midpoint voltage of the a-phase capacitor; is the point voltage.

[0097] Among them, taking the combined output voltage vector as an example, let the switching period be T s ,express:

[0098] (1);

[0099] Where, ; represents the zero vector; represents the first zero vector; represents the second zero vector; Indicates the action time of the first zero vector U1; Represents the second zero vector duration of action; Represents the zero vector duration of action;

[0100] Decompose equation (1) on the horizontal and vertical axes to find the values ​​of T1 and T2, which are expressed as:

[0101] (2);

[0102] (3);

[0103] (4);

[0104] Where, represents the modulation index; Indicates DC voltage; represents the sine function; Represents the cosine function.

[0105] The specific process of obtaining the harmonic amplitude is as follows:

[0106] In the process of calculating the harmonic amplitude of the SVPWM circuit, the Fourier decomposition of the point voltage is performed based on the combined output voltage vector, which is expressed as:

[0107] (5);

[0108] Where, Indicates point voltage over time The changing voltage waveform; Indicates the average value of the point voltage; Indicates infinity; Indicates the harmonic order; Indicates the fundamental angular frequency; and Represent the amplitudes of the corresponding cosine and sine terms respectively; among them, ; is the fundamental frequency;

[0109] The total time of positive and negative voltage level action in one output switching cycle T s The same inside, and the point voltage is an even function, which means:

[0110] (6);

[0111] (7);

[0112] (8);

[0113] Where, represents a small increment of time;

[0114] Rotation angle of voltage space vector As the boundary, the voltage at the point changes with time The changing voltage waveform In half the output switching period T s Expanded inside, divided into 1 zone and District 1 and The length of the zone is T s / 2; is the modulation factor;

[0115] Based on the division into Zone 1 and Assume that the voltage space vector corresponding to the kth region rotates by an angle, which is expressed as:

[0116] (9);

[0117] Where r k is the rotation angle of the voltage space vector corresponding to the kth region; Indicates the rotation angle increment for each interval; Indicates the total number of intervals;

[0118] Assume that the positive level duty ratio of the voltage space vector rotation angle corresponding to the kth region is ,express:

[0119] (10);

[0120] Where, Represents half a switching period T s The starting moment of the time node; Represents half a switching period T s The last time node within the half cycle T s The final moment; Indicates the end time of the positive level duty cycle time node of the voltage space vector rotation angle corresponding to the first zone; Indicates the positive level duty cycle of the voltage space vector rotation angle corresponding to the first zone; Indicates the end time of the positive level duty cycle time node of the voltage space vector rotation angle corresponding to the 2k-2 region; Indicates the end time of the positive level duty cycle time node of the voltage space vector rotation angle corresponding to the 2k-3 region; represents the positive level duty cycle of the voltage space vector rotation angle corresponding to the k−1th region; Indicates the end time of the positive level duty cycle time node of the voltage space vector rotation angle corresponding to the 2k-1th zone; Indicates a period;

[0121] Based on the positive level duty cycle And the period T is calculated to get Time value; Indicates the positive level duty cycle of zone 1 The time value obtained by and period T, Indicates the Positive level duty cycle The time value obtained by summing the period T;

[0122] Then the obtained The time value is substituted into formula (8) to obtain The integral expansion of the time value is obtained , which represents

[0123] (11);

[0124] In the formula, represents the amplitude of the first harmonic.

[0125] In the black-winged kite optimization algorithm, the specific process of introducing the Levy tangent flight strategy is as follows:

[0126] The parameters of the black-winged kite optimization algorithm are set, including the number of black-winged kites, the search space, the total number of iterations, and the leader, which is a value randomly selected between [0, 1] and used to initialize the position of each black-winged kite; a black-winged kite matrix is generated based on the set parameters of the black-winged kite optimization algorithm, and after randomly assigning the position of each black-winged kite from the black-winged kite matrix, the initial population is generated using the Tent mapping, and the current iteration number t of the initial population is set to 0; the initial position of the black-winged kite in the initial population is calculated by formula (12), which represents

[0127] (12);

[0128] In the formula, represents the initial position of the i-th black-winged kite; and represent the lower and upper bounds of the search space, respectively; () represents a random number between [0, 1];

[0129] When initializing the initial population, the best black-winged kite in terms of fitness is considered as the leader in the initial population, i.e., the optimal position of the black-winged kite in the initial population, and the optimal position is the best choice for the entire data, y L The calculation formula of y

[0130] (13);

[0131] (14);

[0132] In the formula, represents the fitness value of the optimal solution found at present; represents the fitness value of the i-th black-winged kite in the initial population; represents the optimal position of the black-winged kite in the initial population; represents the black-winged kite; represents function; represents the minimum value; ​fitness value of the i-th black kite at the current position fitness value of the i-th black kite at the current position

[0133] As a predator of grassland small mammals and insects, the black kite adjusts the angle of the wings and tail according to the wind speed in the battle, quietly circles to observe the prey, and then dives to attack quickly; the attack strategy includes global exploration and different attack behaviors, which helps the black kite to better capture the prey; the attack strategy update equation is:

[0134] (15);

[0135] wherein, position of the i-th black kite in the j-th dimension in the t+1-th iteration step; position of the i-th black kite in the j-th dimension in the t-th iteration step; threshold value; a random number between 0 and 1 in the initial population; nonlinear factor; Q represents the total number of iterations; natural logarithm base; otherwise;

[0136] Bird migration strategy is a complex behavior affected by environmental factors such as climate and food supply; bird migration strategy is to adapt to seasonal changes, and many birds migrate from the north to the south in winter to obtain better living conditions and resources; the migration strategy is usually led by a leader, and the navigation skills of birds are crucial to the success of the team; based on the bird migration strategy, a hypothesis is proposed: if the fitness value of the current optimal solution is less than the random migration population, the leader will give up leadership and join the random migration population, which indicates that it is not suitable to lead the initial population forward, on the contrary, if the fitness value of the current optimal solution is greater than the random migration population, it will guide the initial population until the destination is reached; the migration strategy can dynamically select excellent leaders to ensure successful migration; the black kite migration strategy is represented as:

[0137] (16);

[0138] wherein, a random number between 0 and 1, representing a Cauchy mutation; the highest scorer of the black kite in the j-th dimension in the t-th iteration step; fitness value of the i-th black kite; a randomly generated fitness threshold value; a constant; ;

[0139] The probability density function of Cauchy mutation is represented as:

[0140] (17);

[0141] In the formula, The probability density function of Cauchy distribution is represented as: The scale parameter is represented as: The random variable is represented as: The position parameter is represented as:

[0142] When The probability density function becomes a standard form, which is represented as:

[0143] (18);

[0144] In the migration strategy stage, the Levy tangent flight strategy algorithm is applied to the case that the fitness value of the current optimal solution found is less than the fitness value of the random migration population, which can get rid of the dependence on the black-winged kite losing the leader role, and is beneficial to expand the search range of the algorithm.

[0145] In the Levy tangent flight strategy algorithm, a new step length based on a tangent function is proposed, such as: step xtan(0), where step is the moving step length, and xtan(0) is the moving direction, which can finely adjust the local search; when the step xtan(0) value gradually tends to 0, the tangent slope of the step xtan(0) value gradually becomes smaller, the change of the moving step length is smaller, and the obtained data is more suitable for the required optimization data, which is suitable for local search; when the step xtan(0) value is closer to 0, the tangent slope of the step xtan(0) value is larger, the change of the moving step length is larger, and the obtained solution is farther away from the current solution, which is suitable for global search; using the Levy tangent flight strategy algorithm to generate the moving step length of the tangent flight helps to explore the remote areas in the space and enhances the global search ability of the black-winged kite optimization algorithm, and can better cope with complex search space; the Levy tangent flight strategy algorithm is added to the black-winged kite migration strategy, which is represented as:

[0146] (19);

[0147] In the formula, The tangent function is represented as: The flight length is represented as:

[0148] In the black-winged kite optimization algorithm, the specific process of introducing the prey escape strategy is as follows:

[0149] In the attack strategy of the black kite optimization algorithm, different attack behaviors of global exploration and search are included, but the escape of the prey from the attack of the black kite is ignored, which makes the black kite optimization algorithm fail to find the global optimal solution and easily fall into local optimization. In addition, the search intensity of the black kite optimization algorithm is limited due to the lack of information exchange in the attack stage, so the prey escape energy in the golden jackal optimization algorithm is referred to, and the prey escape energy in the black kite algorithm is defined as follows:

[0150] (20);

[0151] In the formula, represents the prey escape energy; represents the exponential function; represents the ratio of the current iteration number t to the total iteration number .

[0152] When , it means that the prey does not have excess prey escape energy to escape the attack circle of the black kite, at this time the original attack strategy formula (15) is used to update the position of the black kite, where E0 represents the prey escape threshold;

[0153] Compared with formula (15), the nonlinear factor is changed to E, and the nonlinear factor gradually decreases with the increase of the iteration number, and the nonlinear factor has a limited range of value, which leads to a limited search range of the black kite optimization algorithm, and E oscillates between (-1, 1), which makes the update step of the black kite optimization algorithm more random, so that the black kite optimization algorithm can find more excellent solutions;

[0154] When , it means that the prey has enough prey escape energy to escape the attack of the black kite, at this time the trust region mutation strategy is introduced into the black kite optimization algorithm to increase the search intensity and prevent the prey from escaping;

[0155] Firstly, the Euclidean distance between the black kite i and the black kite is defined, and the mean position of all black kites is calculated based on the Euclidean distance, and the initial trust region radius is calculated according to the distance between the current black kite i and the mean position , which is represented as:

[0156] (21);

[0157] In the formula, represents the Euclidean distance between the black kite i and the black kite . represents the Euclidean distance; represents the coordinate value of the first dimension of the i-th black kite in the multi-dimensional space; represents the coordinate value of the first dimension of the i-th black kite in the multi-dimensional space; represents the coordinate value of the first dimension of the i-th black kite in the multi-dimensional space; represents the coordinate value of the D-th dimension of the i-th black kite in the multi-dimensional space; represents the coordinate value of the D-th dimension of the i-th black kite in the multi-dimensional space; represents the coordinate value of the D-th dimension of the i-th black kite in the multi-dimensional space; represents the total number of black kites; represents the positions of black kite i and black kite represents the initial trust region radius of the i-th black kite;

[0158] the Euclidean distance between the current black kite i and black kite is less than the initial trust region radius of the i-th black kite, as a trusted black kite, the mean position of the trusted black kite is calculated, represented as:

[0159] (22);

[0160] wherein, represents the set of positions of the i-th trusted black kite; represents the position of the i-th trusted black kite; represents the mean position of the trusted black kite; represents the number of trusted black kites; represents the threshold value of the mean position of the i-th trusted black kite;

[0161] Finally, combined with the information between the current trusted black kite and the mean position of the trusted black kite, the next generation of trusted black kite is generated, completing the information exchange between the trusted black kites, and preventing the black kite optimization algorithm from falling into local optimum;

[0162] Levy tangent flight strategy is introduced in the attack strategy, which describes a random search method, so that the black kite optimization algorithm can better perform local exploration at small step size and better perform global [0, 1] search at large step size;

[0163] Levy tangent flight strategy is introduced in the attack strategy, represented as:

[0164] (23);

[0165] (24);

[0166] wherein, represents the step size of the Levy tangent flight strategy algorithm; ​Represents a normally distributed random number between [0,1]; represents the standard deviation; represents the gamma function; Indicates general parameters;

[0167] In summary, the Levy tangent flight strategy and the trust region mutation strategy are combined to update the position of the attack strategy, which is expressed as:

[0168] (25);

[0169] The error of the position of the i-th black-winged kite in the j-th dimension of the t+1th iteration after the combination is based on the optimal position y of the black-winged kite in the initial population L Make corrections until the accuracy requirements of the Black Kite optimization algorithm are met;

[0170] When the black kite optimization algorithm meets the accuracy requirements, the iteration ends and the optimal identification parameters are obtained. Otherwise, the algorithm returns to formula (12) to recalculate the initial position of the black kites in the initial population. Considering that the black kite optimization algorithm still fails to meet the accuracy requirements when the number of iterations reaches the upper limit during the iteration process, the minimum fitness value of the position of the i-th black kite in the j-th dimension after the t+1-th iteration is selected as the optimal solution output.

[0171] The specific process of obtaining the total harmonic distortion rate is as follows:

[0172] Taking the solution of 6 switch tubes when M=0.6 as an example, the solution results of particle swarm optimization algorithm PSO, black kite optimization algorithm BKA and improved dynamic search algorithm EBKA are compared;

[0173] The optimal identification parameters of the improved dynamic search algorithm are iteratively calculated. harmonic amplitude ,express:

[0174] (26);

[0175] Where, Indicates the amplitude of the first harmonic; Indicates the distortion rate of the first 50 harmonics of the output voltage; The error term representing the harmonic amplitude; Indicates pulse edge; Represents the i-th switch tube; is the zeroth harmonic amplitude; represents the error term of the first harmonic amplitude; Z represents the modulation ratio; Indicates voltage; Indicates the correction coefficient or proportional factor; Indicates the 5th harmonic amplitude standard; error term representing the 5th harmonic amplitude; error term representing the standard of the 2nd harmonic amplitude; error term representing the standard of the 5th harmonic amplitude; = 1, 2, 3, …, 6; = 5, 7, 11, …, 49;

[0176] based on the pulse edge , the pulse edge is 1 at the rising edge, and the pulse edge is -1 at the falling edge, and the harmonic standards of the power quality utility grid harmonics (GB / T 14549-93); based on the pulse edge and the harmonic standards of the power quality utility grid harmonics (GB / T 14549-93), the switch tube is repeatedly tested by using the particle swarm algorithm PSO, the black-winged kite optimization algorithm BKA, and the improved dynamic search algorithm EBKA, and the optimal case of the repeatedly tested solution is selected and applied to the specific harmonic elimination pulse width modulation and the specific harmonic suppression pulse width modulation strategy, respectively;

[0177] based on the output voltage harmonic distortion rate of the first 50 harmonics the total harmonic distortion rate is calculated:

[0178] (27);

[0179] wherein, represents the total harmonic distortion rate; represents the absolute value of the harmonic amplitude;

[0180] Under the specific harmonic elimination pulse width modulation strategy, as the number of non-linear factors increases, the convergence performance of the improved dynamic search algorithm EBKA is obviously better than that of the particle swarm algorithm PSO and the black-winged kite optimization algorithm BKA, the search speed of the improved dynamic search algorithm EBKA increases at the initial stage, slows down at the mature stage, and speeds up at the end, similar to the growth trend of the growth curve, which is more conducive to jumping out of the local optimal solution and searching for the global optimal solution in the shortest time, and the total harmonic distortion rate THD calculated by the selected switch tube is also the smallest, while the particle swarm algorithm PSO and the black-winged kite optimization algorithm BKA appear unstable at the later stage of the search;

[0181] Under the same modulation ratio M = 0.6, the switch tube and the total harmonic distortion rate obtained by applying the improved dynamic search algorithm EBKA, the black-winged kite optimization algorithm BKA, and the particle swarm algorithm PSO to the specific harmonic elimination pulse width modulation strategy and the specific harmonic suppression pulse width modulation strategy are shown in Tables 1 and 2.

[0182] Table 1 Comparison of simulation results of specific harmonic elimination pulse width modulation strategy under three algorithms

[0183]

[0184] It is found by checking Table 1 that the optimal switch obtained by the improved dynamic search algorithm EBKA to control the rectifier circuit reduces the total harmonic distortion THD by 1.97% compared with the particle swarm algorithm PSO and by 0.73% compared with the black-winged kite optimization algorithm BKA.

[0185] Table 2 Comparison of simulation results of specific harmonic elimination pulse width modulation strategy under three algorithms

[0186]

[0187] Based on the improved dynamic search algorithm EBKA, the total harmonic distortion THD is analyzed by fast Fourier transform FFT taking the specific harmonic elimination pulse width modulation strategy and the specific harmonic suppression pulse width modulation strategy as examples, the overall iterative search capability is improved, and the total harmonic distortion THD of the output voltage is reduced.

[0188] Although the embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for optimizing the active suppression of harmonics in a rectifier transformer for hydrogen production by water electrolysis, characterized in that: The following steps are involved: Step S1: constructing a rectifier circuit, the rectifier circuit including a switch tube, combining a voltage vector output by the switch tube and a zero vector to obtain a combined output voltage vector; processing the combined output voltage vector to obtain a harmonic amplitude; Step S2: Introducing the Levy tangent flight strategy and the trust region mutation strategy into the black kite optimization algorithm to construct an improved dynamic search algorithm; Step S3: Iteratively calculating the harmonic amplitudes using an improved dynamic search algorithm to obtain the total harmonic distortion rate (THD), i.e., the optimal switch tube combination. The switches of the rectifier circuit are adjusted using the optimal switch tube combination to reduce the THD of the rectifier circuit. The rectifier circuit includes an SVPWM circuit; the SVPWM circuit is divided into several sectors, each sector includes a switch tube and a voltage space vector rotation angle, and the voltage vectors output by the switch tubes in the several sectors are combined with the zero vector to obtain a combined output voltage vector; r is the voltage space vector rotation angle; is the combined output voltage vector; wherein the SVPWM circuit includes the midpoint voltage of the a-phase capacitor; is the point voltage; Based on the combined output voltage vector, let the switching period be T s ,express: （1）； Where, ; represents the zero vector; represents the first zero vector; represents the second zero vector; Indicates the action time of the first zero vector U1; Represents the second zero vector duration of action; Represents the zero vector duration of action; Solve for the values ​​of T1 and T2, which means: （2）； （3）； （4）； Where, represents the modulation index; Indicates DC voltage; represents the sine function; represents the cosine function; The specific process of obtaining the harmonic amplitude is: In the process of calculating the harmonic amplitude of the SVPWM circuit, the Fourier decomposition of the point voltage is performed based on the combined output voltage vector, which is expressed as: （5）； Where, Indicates point voltage over time The changing voltage waveform; Indicates the average value of the point voltage; Indicates infinity; Indicates the harmonic order; Indicates the fundamental angular frequency; and denote the amplitudes of the corresponding cosine and sine terms respectively; ; is the fundamental frequency; The point voltage is an even function, which means: （6）； （7）； （8）； Where, represents a small increment of time; Rotation angle of voltage space vector As the boundary, the voltage at the point changes with time The changing voltage waveform In half the output switching period T s Expanded inside, divided into 1 zone and district; is the modulation factor; Based on the division into Zone 1 and Assume that the voltage space vector corresponding to the kth region rotates by an angle, which is expressed as: （9）； Where r k is the rotation angle of the voltage space vector corresponding to the kth region; Indicates the rotation angle increment for each interval; Indicates the total number of intervals; Assume that the positive level duty ratio of the voltage space vector rotation angle corresponding to the kth region is ,express: （10）； Where, Represents half a switching period T s The starting moment of the time node; Represents half a switching period T s The last time node within the half cycle T s The final moment; Indicates the end time of the positive level duty cycle time node of the voltage space vector rotation angle corresponding to the first zone; Indicates the positive level duty cycle of the voltage space vector rotation angle corresponding to the first zone; Indicates the The end moment of the positive level duty cycle time node of the voltage space vector rotation angle corresponding to the area; Indicates the The end moment of the positive level duty cycle time node of the voltage space vector rotation angle corresponding to the area; represents the positive level duty cycle of the voltage space vector rotation angle corresponding to the k−1th region; Indicates the The end moment of the positive level duty cycle time node of the voltage space vector rotation angle corresponding to the area; Indicates a period; Based on the positive level duty cycle And the period T is calculated to get Time value; Indicates the positive level duty cycle of zone 1 The time value obtained by and period T, Indicates the Positive level duty cycle The time value obtained by summing the period T; Then the obtained Substitute the time value into formula (8) and The integral expansion of the time value is ,express: （11）； Where, Indicates the amplitude of the nth harmonic.

2. The method for optimizing the active harmonic suppression of a rectifier transformer for hydrogen production by water electrolysis according to claim 1, characterized in that: The specific process of introducing the Levy tangent flight strategy into the black kite optimization algorithm is as follows: The parameters of the black kite optimization algorithm are set, including the number of black kites, search space, total number of iterations, and leader. A black kite matrix is ​​generated based on the parameters of the black kite optimization algorithm. After randomly assigning the position of each black kite from the black kite matrix, the initial population is generated using Tent mapping, and the initial position of the black kite in the initial population is calculated using formula (12), which is expressed as: （12）； Where, represents the initial position of the i-th black-winged kite; and Represent the lower and upper bounds of the search space respectively; () represents a random number between [0,1]; The optimal position y of the black kite in the initial population L The calculation formula is: （13）； （14）； Where, Indicates the currently found optimal fitness value; represents the fitness value of the i-th black kite in the initial population; It means black-winged kite; express function; Indicates the minimum value; Indicates that the i-th black-winged kite is at the current position The fitness value at ; The attack strategy update equation is: （15）； Where, represents the position of the i-th black-winged kite in the j-th dimension in the t+1-th iteration step; represents the position of the i-th black-winged kite in the j-th dimension in the t-th iteration step; Indicates the threshold value; Represents a random number between 0 and 1 in the initial population; represents the nonlinear factor; ;Q represents the total number of iterations; represents the base of natural logarithms; Indicates otherwise; Black kite migration strategy, indicating: （16）； Where, Represents a random number between 0 and 1, indicating a Cauchy mutation; represents the black kite with the highest score in the j-th dimension in the t-th iteration step; represents the fitness value of the i-th black-winged kite; represents a randomly generated fitness threshold; represents a constant; ; The probability density function of the Cauchy mutation is expressed as: （17）； Where, represents the probability density function of the Cauchy distribution; represents the scale parameter; represents a random variable; Represents positional parameters; when When , the probability density function becomes the standard form, which is expressed as: （18）； The improved black kite migration strategy, which incorporates the Levy tangent flight strategy algorithm, is expressed as follows: （19）； Where, represents the tangent function; Indicates the flight length.

3. The method for optimizing the active harmonic suppression of a rectifier transformer for hydrogen production by water electrolysis according to claim 2, characterized in that: The specific process of introducing the trust region mutation strategy into the Black Kite optimization algorithm is as follows: First, define the prey escape energy of the black kite algorithm, which is expressed as: （20）； Where, It indicates the energy of prey escape; represents the exponential function; Indicates the current number of iterations t and the total number of iterations The ratio of when When , it means that the prey does not have excess prey escape energy to escape the attack circle of the black-winged kite. At this time, the original attack strategy of formula (15) is used to update the position of the black-winged kite, where E0 represents the prey escape threshold; when When , it means that the prey has enough escape energy to escape the attack of the black kite. At this time, the trust region mutation strategy is introduced into the black kite optimization algorithm to increase the search intensity and prevent the prey from escaping. First, define black-winged kite i to black-winged kite The Euclidean distance between them is used to calculate the mean position of all black kites based on the Euclidean distance. , according to the current black-winged kite i and the mean position The distance between them is used to calculate the initial trust region radius, which is expressed as: （21）； Where, Indicates black-winged kite i and black-winged kite The Euclidean distance between represents the Euclidean distance; Represents the coordinate value of the i-th black-winged kite in the first dimension of the multidimensional space; Indicates the The coordinate values ​​of a black kite in the first dimension of the multidimensional space; represents the coordinate value of the i-th black-winged kite in the D-th dimension in the multidimensional space; Indicates the The coordinate value of a black-winged kite in the D-th dimension in multidimensional space; represents the total number of black-winged kites; Indicates black-winged kite i and black-winged kite location; represents the initial trust region radius of the i-th black kite; Current Black Winged Kite i to Black Winged Kite The Euclidean distance between them is less than the initial trust region radius of the i-th black kite, and it is regarded as a trustworthy black kite. The mean position of the trustworthy black kite is calculated, which is expressed as: （22）； Where, represents the set of locations of the i-th reliable black kite; represents the position of the i-th trustworthy black kite; represents the mean position of the trustworthy black-winged kite; Indicates the number of trustworthy black-winged kites; represents the threshold of the mean position of the i-th reliable black kite; The Levy tangent flight strategy is introduced in the attack strategy, which means: （23）； （24）； Where, Indicates the step size of the Levy tangent flight strategy algorithm; Represents a normally distributed random number between [0,1]; represents the standard deviation; represents the gamma function; Indicates general parameters; Combining the Levy tangent flight strategy and the trust region mutation strategy to update the position of the attack strategy, it is expressed as: （25）； The error of the position of the i-th black-winged kite in the j-th dimension of the t+1th iteration after the combination is based on the optimal position y of the black-winged kite in the initial population L Make corrections until the accuracy requirements of the Black Kite optimization algorithm are met; When the black kite optimization algorithm meets the accuracy requirements, the iteration ends and the optimal identification parameters are obtained. Otherwise, the algorithm returns to formula (12) to recalculate the initial position of the black kites in the initial population. Considering that the black kite optimization algorithm still fails to meet the accuracy requirements when the number of iterations reaches the upper limit during the iteration process, the minimum fitness value of the position of the i-th black kite in the j-th dimension after the t+1-th iteration is selected as the optimal solution output.

4. The method for optimizing active harmonic suppression of a rectifier transformer for hydrogen production by water electrolysis according to claim 3, characterized in that: The specific process of obtaining the total harmonic distortion is: The nth harmonic amplitude is calculated iteratively by optimizing the identification parameters of the improved dynamic search algorithm. ,express; （26）； Where, Indicates the amplitude of the first harmonic; Indicates the distortion rate of the first 50 harmonics of the output voltage; The error term representing the harmonic amplitude; Indicates pulse edge; Represents the i-th switch tube; is the zeroth harmonic amplitude; represents the error term of the first harmonic amplitude; Z represents the modulation ratio; Indicates voltage; Indicates the correction coefficient or proportional factor; Indicates the 5th harmonic amplitude standard; represents the error term of the 5th harmonic amplitude; Indicates the Subharmonic amplitude standard; Indicates the The error term of the harmonic amplitude; =1,2,3,…,6; =5,7,11,…,49; Based on the first 50 harmonic distortion rates of the output voltage Calculate the total harmonic distortion, expressed as: （27）； Where, Indicates total harmonic distortion; Indicates the absolute value of the harmonic amplitude.

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