CN114257115A - MPUC inverter selective harmonic elimination method based on multivariate universe optimization - Google Patents

MPUC inverter selective harmonic elimination method based on multivariate universe optimization Download PDF

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CN114257115A
CN114257115A CN202111613812.XA CN202111613812A CN114257115A CN 114257115 A CN114257115 A CN 114257115A CN 202111613812 A CN202111613812 A CN 202111613812A CN 114257115 A CN114257115 A CN 114257115A
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inverter
mpuc
torque
harmonic
phase
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张钰晗
李国华
王轶博
苑朝鸣
付振芳
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Liaoning Technical University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
    • H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
    • H02P23/04—Arrangements or methods for the control of AC motors characterised by a control method other than vector control specially adapted for damping motor oscillations, e.g. for reducing hunting
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
    • H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
    • H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
    • H02P27/08—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation
    • H02P27/085—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency

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  • Control Of Ac Motors In General (AREA)

Abstract

The invention provides a selective harmonic elimination method for an MPUC inverter based on multivariate cosmic optimization, and relates to the technical field of pulse width modulation of the MPUC inverter. The method comprises the steps that firstly, different output voltage waveforms are generated by matching different power supply voltage amplitudes with different modulation controls, and five states are used for triggering the MPUC inverter; analyzing the torque ripple characteristic of the power supply induction motor of the three-phase five-level MPUC inverter, and selectively eliminating the influence of different power supply harmonics on the torque ripple of the motor through comparison analysis; and finally, searching and detecting the space by adopting a multivariate universe optimization algorithm through two processes of exploration and exploitation to solve the switching angle of the selective harmonic elimination pulse width modulation SHEPWM, so that the selective harmonic elimination of the three-phase five-level MPUC inverter is realized. The method can effectively inhibit the corresponding torque ripple in the induction motor and improve the working stability of the motor by selectively eliminating the specific time harmonic in the inverter power supply.

Description

MPUC inverter selective harmonic elimination method based on multivariate universe optimization
Technical Field
The invention relates to the technical field of pulse width modulation of an MPUC inverter, in particular to a method for eliminating selective harmonics of the MPUC inverter based on multi-universe optimization.
Background
At present, the methods for reducing electromagnetic noise and torque ripple of a motor from the aspect of controlling inverter harmonic waves include: the soft and hardware filters are used for improving the switching frequency, dynamically adjusting the switching frequency, realizing a random PWM strategy, improving the topological structure of the inverter, eliminating specific time harmonics and the like. The literature "random PWM control strategy for damping vibration and noise of an induction motor for an electric vehicle" realizes selective control of harmonics in a specific frequency band by adding a band-pass digital filter to a control algorithm, but the calculation amount of the digital filter is relatively large. Patents and solutions prove that increasing the switching frequency of a converter can effectively reduce the running noise of a motor, but the excessively high switching frequency can cause negative effects such as loss increase and stress increase of a power switching device; the document "Audible noise and loss in variable speed index motor drive with IGBT inverters-inverter of the resonant cage design and the switching frequency" reduces the vibration of the motor system in different operating states by dynamically changing the switching frequency; the document "propagation and Selection of basic Statistical Parameters in Random Slope PWM Based on unity Distribution" effectively reduces the electromagnetic noise near the integral multiple of the switching frequency in the ac motor by Random switching frequency, but in the process of Random frequency spreading, it may cause the harmonic content near the original harmonic peak to increase instead, so as to generate new electromagnetic vibration and electromagnetic noise;
a Single-Phase Step-Up Switched-Capacitor-Based Multilevel Inverter Topology With SHEPWM (pulse-width modulation) strategy is an effective method for eliminating low-order time harmonics of an Inverter and adapting to low switching frequency. The common SHEPWM nonlinear transcendental equation solving method has a numerical method, an algebraic method, an intelligent algorithm and the like. In recent years some new intelligent algorithms have been applied in the SHEPWM strategy. The literature, "real number coding genetic simulated annealing algorithm SHEPWM control technology" adopts a genetic algorithm, but the population scale, the variation probability, the mating probability, the evolution algebra and the selection of population initialization can cause the loss of the evolution ability of the population, the reduction of the diversity, the precocity of the population or the occurrence of the situation of non-convergence. The literature, "research on a T-type three-level inverter PWM modulation strategy" adopts a particle swarm optimization algorithm, the performance and convergence of the particle swarm optimization algorithm are directly influenced by parameters, and the setting of the parameters depends on experience to a great extent. The literature "Application of the Bee colony Algorithm for Selective Harmonic impedance simulation in Multilevel investors" applies the swarm Algorithm to the calculation of the SHEPWM equation set, and has the advantages of high precision, slow convergence speed and easy precocity; the application of the literature 'chaotic ant colony algorithm in a three-level inverter SHEPWM strategy' provides an ant colony optimization algorithm, but initially, pheromones are deficient, the global convergence is poor, and the efficiency is low.
Disclosure of Invention
The invention aims to solve the technical problem of the prior art, and provides a selective harmonic elimination method of an MPUC inverter based on multivariate cosmic optimization, which is used for selectively eliminating the harmonic of a five-level MPUC inverter.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: the MPUC inverter selective harmonic elimination method based on the multivariate universe optimization comprises the following steps:
step 1, analyzing the switching state of a three-phase five-level MPUC inverter, generating different output voltage waveforms by utilizing different power supply voltage amplitudes and different modulation control coordination, and triggering the MPUC inverter by using the states of 1, 3, 5, 7 and 8;
step 2, analyzing the torque ripple characteristic of a power supply induction motor of the three-phase five-level MPUC inverter; selectively eliminating the influence of different power supply harmonics on the motor torque pulsation through comparative analysis;
step 2.1, determining the asynchronous torque of a power supply induction motor of the three-phase five-level MPUC inverter;
when the times of air gap harmonic magnetic flux and rotor harmonic current in the three-phase five-level MPUC inverter power supply induction motor are the same, the power supply induction motor influenced by the electromagnetic action can generate asynchronous torque, and the following formula is shown as follows:
Tn,1＝CTφnI2ncosψ2n (1)
wherein, Tn,1To power the asynchronous torque generated by the induction motor,
Figure BDA0003436353630000021
is a torque constant, m1Is the number of motor phases, p is the number of motor pole pairs, N2For each phase turn of the rotor, kw2Is the fundamental wave rotor winding coefficient; phi is anStator flux generated for n time harmonics; psi2nIs composed ofnGenerated electromotive force and rotor harmonic current I2nThe phase difference of (a);
the direction of the asynchronous torque depends on the high-order time harmonic number, when the harmonic number n is 6k +1, k is a natural number, and the direction of the asynchronous torque is the same as the rotating speed; when n is 6k '-1, k' is a natural number not equal to 0, and the direction of asynchronous torque is opposite to the rotating speed;
step 2.2, determining the pulsation torque of a power supply induction motor of the three-phase five-level MPUC inverter;
the pulsating torque of the motor is generated by the interaction of current and magnetic flux of different frequencies in the air gap of the motor; because of the uncertainty of the harmonic times, the ripple torque generated by each set of current and magnetic flux is different, wherein the most important ripple torque is generated by the stator fundamental wave magnetic flux and the rotor harmonic current, and the following formula is shown:
Tn＝2CTφI2ncos[(n±1)ωt-ψ1,2n] (2)
wherein, TnThe pulsating torque generated by the stator fundamental flux and the n-th harmonic current of the rotor, phi being the fundamental flux, psi1,2nThe phase difference between the fundamental electromotive force and the rotor current is shown, omega is the angular frequency of the rotor current, and t is time;
according to the formula (2), in the three-phase five-level MPUC inverter induction motor, the frequency of the ripple torque generated by 5 th and 7 th harmonics is 6f, f is the fundamental frequency output by the three-phase five-level MPUC inverter, and the directions are opposite, namely f- (-5f) ═ 6f and f-7f ═ 6 f; similarly, the frequencies of the pulsating torques generated by the 11 th harmonic and the 13 th harmonic are both 12f, i.e., f- (-11f) ═ 12f and f-13f ═ 12 f; and then obtain the ripple torque that arbitrary subrotor harmonic current and fundamental wave magnetic flux place produced, namely the main ripple torque source is 6 fundamental wave frequencies, therefore the instantaneous ripple torque of the motor is shown as following formula:
T(em)(t)＝T0+T6cos6ωt+T12cos12ωt……T6ncos6nωt (3)
wherein, T(em)(T) instantaneous pulsating torque of the motor, T0For instantaneous ripple torque fundamental amplitude, T6nA ripple torque generated for the 6n harmonic, n not equal to 0;
step 3, searching and detecting the space by adopting a multivariate universe optimization algorithm through two processes of exploration and exploitation to solve the switching angle of selective harmonic elimination pulse width modulation SHEPWM, so that selective harmonic elimination of the three-phase five-level MPUC inverter is realized;
step 3.1, according to the amplitude of the output voltage waveform of the five-level MPUC inverter and the symmetrical characteristics of the waveform, the nonlinear SHEPWM equation system output by the five-level MPUC inverter is expressed as follows:
Figure BDA0003436353630000031
where M is the amplitude modulation ratio, n is 6 k' -1, alpha is the higher order number of the harmonic to be eliminatedsIs the S-th switching angle in (0, pi/2), S is the total number of switching angles, pkFor position factor, p when the inverter output level riseskIs 1, p when the output level is loweredkIs-1;
step 3.2, converting a nonlinear SHEPWM equation system output by the five-level MPUC inverter into a multi-objective optimization problem;
each sub-equation in the formula (4) is regarded as an optimization objective function, and is respectively denoted as f(1)、f(2)、f(3)、……、f(m)M is the number of equations; converting the multi-objective function of the formula (4) into a single objective function, as shown in the following formula:
Figure BDA0003436353630000032
step 3.3, taking the single objective function minF as the fitness function of the multi-universe optimization algorithm to minimize the fitness function value and obtain the optimal switching angle of SHEPWM
Figure BDA0003436353630000033
In the SHEPWM solution problem, the switching angle is regarded as a transport of particles from white holes to black holes, from which the particles select the black holes according to WEP and TDR; then, updating the WEP and the TDR continuously according to the fitness value, thereby continuously searching an optimal solution, specifically comprising the following steps:
3.3.1, initializing iteration times I, switching angle numbers S and universe group numbers U, and calculating a minF value; when the iteration times are less than I, carrying out the next operation;
3.3.2, selecting black holes from the white holes by the particles according to WEP and TDR, and calculating a fitness value;
step 3.3.3, randomly placing u universes in s angles;
3.3.4, based on the standard expansion rate, generating white holes by the roulette rule, and selecting black holes from the white holes according to WEP and TDR by particles; then, updating WEP and TDR continuously according to the fitness value, thereby continuously searching the universe;
step 3.3.5, calculating each switch angle after iteration, and recording an optimal value and an optimal point;
step 3.3.6, updating the calculated switch angle; if the updated optimal universe is superior to the current optimal universe, replacing the current switch angle with each updated switch angle, and updating the optimal universe, otherwise, still keeping the current switch angle and the current optimal universe;
step 3.3.7, recording the optimal value and the optimal point;
step 3.3.8, adding 1 to the iteration times, and returning to step 2 if the iteration times are less than the specified times;
and step 3.3.9, ending.
Adopt the produced beneficial effect of above-mentioned technical scheme to lie in: the MPUC inverter selective harmonic elimination method based on multivariate cosmic optimization provided by the invention utilizes a multivariate cosmic optimization algorithm to calculate the switching angle required by SHEPWM, thereby realizing selective harmonic elimination without initial conditions. The method can effectively inhibit the corresponding torque ripple in the induction motor and improve the working stability of the motor by selectively eliminating the specific time harmonic in the inverter power supply.
Drawings
Fig. 1 is a flowchart of a method for selectively eliminating harmonics of an MPUC inverter based on multivariate cosmic optimization according to an embodiment of the present invention;
fig. 2 is a topology structure diagram of a three-phase five-level MPUC inverter according to an embodiment of the present invention;
fig. 3 is a diagram of output voltage levels and current direction of the MPUC inverter provided in the embodiment of the present invention in different switching states, where (a) is a single-phase MPUC topology structure, (b) is a current direction when the output voltage of the single-phase MPUC inverter is 2E, (c) is a current direction when the output voltage of the single-phase MPUC inverter is E, (d) is a current direction when the output voltage of the single-phase MPUC inverter is 0, (E) is a current direction when the output voltage of the single-phase MPUC inverter is-E, and (f) is a current direction when the output voltage of the single-phase MPUC inverter is-2E;
FIG. 4 is a waveform diagram of a five-level phase voltage provided by an embodiment of the present invention;
FIG. 5 is a diagram of a relationship between an objective function and an iteration number according to an embodiment of the present invention;
fig. 6 is a waveform diagram of an inverter phase voltage and an FFT experiment thereof according to an embodiment of the present invention;
FIG. 7 is a graph of inverter line voltage and FFT experimental waveforms thereof according to an embodiment of the present invention;
FIG. 8 is a graph of harmonic content of inverter line voltages at different modulation levels according to an embodiment of the present invention;
fig. 9 is an inverter phase voltage u provided by an embodiment of the present inventionANAnd FFT experiment oscillogram thereof;
fig. 10 shows an inverter line voltage u according to an embodiment of the present inventionABAnd FFT experiment oscillogram thereof;
FIG. 11 is a waveform of torque within 0.46-0.48s provided by an embodiment of the present invention;
fig. 12 is a comparison graph of the torque FFT provided by the embodiment of the present invention.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
In this embodiment, the MPUC inverter selective harmonic elimination method based on multivariate cosmic optimization, as shown in fig. 1, includes the following steps:
step 1, analyzing the switching state of a three-phase five-level MPUC inverter, generating different output voltage waveforms by utilizing different power supply voltage amplitudes and different modulation controls in a matching manner, and triggering the MPUC inverter by only using the states 1, 3, 5, 7 and 8 in order to reduce power loss;
a three-phase five-level MPUC (Modified Packed U-Cells) inverter topology is shown in fig. 2, and the topology is composed of three groups of identical MPUC inverters. Taking a single-phase MPUC five-level inverter as an example, fig. 3(a) is a topology structure of the structure. The structure is composed of 2 independent direct current power supplies and 6 groups of power switching devices.
Inverter switching state as shown in Table 1, switching tube T1And T4、T2And T5、T3And T6Complementary states during conduction. From table 1 it can be derived that a total of 8 switching states can be derived for 3 groups of switching devices. Different supply voltage amplitudes in combination with different modulation controls will produce different output voltage waveforms. Only 1, 3, 5, B, C, and C, C,7. The 8 state triggers the PUC inverter to further reduce power losses. In this embodiment, under the operating conditions of table 1, the voltage and current flows of the MPUC inverter are as shown in fig. 3(b) - (f).
TABLE 1 MPUC inverter switch state table
Figure BDA0003436353630000051
Wherein u isANOutputting phase voltage for the single-phase MPUC inverter, and E is direct-current power supply voltage;
step 2, analyzing the torque ripple characteristic of a power supply induction motor of the three-phase five-level MPUC inverter; selectively eliminating the influence of different power supply harmonics on the motor torque pulsation through comparative analysis;
harmonic components in the induction machine input current can lead to the generation of harmonic electromagnetic torque. When the motor is driven by the PWM converter, the stator current of the motor is non-sinusoidal, so that the magnetic flux density is changed, and magnetic potential at an air gap generates harmonic waves in time and space, and further generates unnecessary harmonic torque. Harmonic torques can be generally divided into asynchronous torques and pulsating torques.
Step 2.1, determining the asynchronous torque of a power supply induction motor of the three-phase five-level MPUC inverter;
when the times of air gap harmonic magnetic flux and rotor harmonic current in the three-phase five-level MPUC inverter power supply induction motor are the same, the power supply induction motor influenced by the electromagnetic action can generate asynchronous torque, and the following formula is shown as follows:
Tn,1＝CTφnI2n cosψ2n (1)
wherein, Tn,1To power the asynchronous torque generated by the induction motor,
Figure BDA0003436353630000061
is a torque constant, m1Is the number of motor phases, p is the number of motor pole pairs, N2For each phase turn of the rotor, kw2Is the fundamental wave rotor winding coefficient; phi is anFor generation of time harmonics of order nA stator magnetic flux; psi2nIs composed ofnGenerated electromotive force and rotor harmonic current I2nThe phase difference of (a);
the direction of the asynchronous torque depends on the high-order time harmonic number, when the harmonic number n is 6k +1 (namely n is 1,7,13 …), k is a natural number, and the direction of the asynchronous torque is the same as the rotating speed; when n is 6k '-1 (i.e. n is 5,11,17, …), k' is a natural number not equal to 0 and the direction of asynchronous torque is opposite to the rotational speed; the asynchronous torque value generated by the harmonic current is small, and harmonic torques in opposite directions can be offset pairwise, so that the influence on the motor is small and can be ignored in the actual operation;
step 2.2, determining the pulsation torque of a power supply induction motor of the three-phase five-level MPUC inverter;
the pulsating torque of the motor is generated by the interaction of current and magnetic flux of different frequencies in the air gap of the motor; because of the uncertainty of the harmonic times, the ripple torque generated by each set of current and magnetic flux is different, wherein the most important ripple torque is generated by the stator fundamental wave magnetic flux and the rotor harmonic current, and the following formula is shown:
Tn＝2CTφI2ncos[(n±1)ωt-ψ1,2n] (2)
wherein, TnThe pulsating torque generated by the stator fundamental flux and the n-th harmonic current of the rotor, phi being the fundamental flux, psi1,2nThe phase difference between the fundamental electromotive force and the rotor current is shown, omega is the angular frequency of the rotor current, and t is time;
supplying power to an induction motor of a three-phase five-level MPUC inverter, wherein the current harmonic frequency corresponding to n-1 is 6k +1, k is a natural number, and the current harmonic frequency corresponding to n +1 is 6 k' -1; the amplitudes of the harmonic currents of 5 th, 7 th, 11 th and 13 th are influenced by harmonic magnetic fields and are reduced along with the increase of the harmonic times; therefore, the ripple harmonic torque caused by the interaction between the fundamental wave magnetic field and each harmonic current needs to be considered;
according to the formula (2), in the three-phase five-level MPUC inverter induction motor, the frequency of the ripple torque generated by 5 th and 7 th harmonics is 6f, f is the fundamental frequency output by the three-phase five-level MPUC inverter, and the directions are opposite, namely f- (-5f) ═ 6f and f-7f ═ 6 f; similarly, the frequencies of the pulsating torques generated by the 11 th harmonic and the 13 th harmonic are both 12f, i.e., f- (-11f) ═ 12f and f-13f ═ 12 f; and then obtain the ripple torque that arbitrary subrotor harmonic current and fundamental wave magnetic flux place produced, namely the main ripple torque source is 6 fundamental wave frequencies, therefore the instantaneous ripple torque of the motor is shown as following formula:
T(em)(t)＝T0+T6cos6ωt+T12cos12ωt……T6ncos6nωt (3)
wherein, T(em)(T) instantaneous pulsating torque of the motor, T0For instantaneous ripple torque fundamental amplitude, T6nA ripple torque generated for the 6n harmonic, n not equal to 0;
harmonic torque is a non-negligible excitation source in the motor operation process, so that the torque of the motor changes periodically, the rotation speed oscillation is caused, and the vibration of a mechanical device is influenced in a magnetic-solid coupling mode. Therefore, it is necessary to suppress the ripple harmonic torque to prevent the influence of resonance on the system when the harmonic torque frequency coincides with the resonance frequency of the electromechanical device.
Step 3, searching and detecting the space by exploring and exploiting two processes by adopting a multivariate universe optimization algorithm to solve the switching angle of selective harmonic elimination pulse width modulation SHEPWM, so that the selective harmonic elimination of the three-phase five-level MPUC inverter is realized, and the selective harmonic elimination effect of the method and the suppression effect on the torque ripple of the induction motor are analyzed;
step 3.1, according to the amplitude of the output voltage waveform of the five-level MPUC inverter and the symmetrical characteristics of the waveform, the nonlinear SHEPWM equation system output by the five-level MPUC inverter is expressed as follows:
Figure BDA0003436353630000071
where M is the amplitude modulation ratio, n is 6 k' -1, alpha is the higher order number of the harmonic to be eliminatedsIs the S-th switching angle in (0, pi/2), S is the total number of switching angles, pkAs position coefficient, inverseWhen level of converter output rises pkIs 1, p when the output level is loweredkIs-1;
the waveform of the phase voltage of the five-level MPUC inverter is shown in figure 4, in a half period, the voltage waveform forms 1/4 even symmetry and has S switching points of switches, wherein alpha is shown in the figure1、αm、αS… is the switch angle. In a three-phase system, due to the symmetry of the load, after eliminating a specific subharmonic in the phase voltages, the line voltage does not contain harmonics of the phase voltages, nor harmonics 3 rd order or multiples thereof.
Step 3.2, converting a nonlinear SHEPWM equation system output by the five-level MPUC inverter into a multi-objective optimization problem;
each sub-equation in the formula (4) is regarded as an optimization objective function, and is respectively denoted as f(1)、f(2)、f(3)、……、f(m)M is the number of equations; converting the multi-objective function of the formula (4) into a single objective function, as shown in the following formula:
Figure BDA0003436353630000072
step 3.3, taking the single objective function minF as the fitness function of the multi-universe optimization algorithm to minimize the fitness function value and obtain the optimal switching angle of SHEPWM
Figure BDA0003436353630000073
In a multivariate cosmic optimization based algorithm (MVO), the high expansion rate universe tends to transport material particles from white holes through wormholes to black holes in the low expansion rate universe.
In the SHEPWM solution problem, the switching angle is regarded as a transport of particles from white holes to black holes, from which the particles select the black holes according to WEP and TDR; then, updating the WEP and the TDR continuously according to the fitness value, thereby continuously searching an optimal solution, specifically comprising the following steps:
3.3.1, initializing iteration times I, switching angle numbers S and universe group numbers U, and calculating a minF value; when the iteration times are less than I, carrying out the next operation;
3.3.2, selecting black holes from the white holes by the particles according to WEP and TDR, and calculating a fitness value;
step 3.3.3, randomly placing u universes in s angles;
3.3.4, based on the standard expansion rate, generating white holes by the roulette rule, and selecting black holes from the white holes according to WEP and TDR by particles; then, updating WEP and TDR continuously according to the fitness value, thereby continuously searching the universe;
step 3.3.5, calculating each switch angle after iteration, and recording an optimal value and an optimal point;
step 3.3.6, updating the calculated switch angle; if the updated optimal universe is superior to the current optimal universe, replacing the current switch angle with each updated switch angle, and updating the optimal universe, otherwise, still keeping the current switch angle and the current optimal universe;
step 3.3.7, recording the optimal value and the optimal point;
step 3.3.8, adding 1 to the iteration times, and returning to step 2 if the iteration times are less than the specified times;
and step 3.3.9, ending.
A multivariate universe optimization algorithm (Multi-Verse Optimizer, MVO) is a process algorithm based on simulating material exchange in the universe; different expansion rates (NI) exist in different universes; according to different expansion rates, the materials are transferred from white holes with high expansion rate to black holes with low expansion rate, and the process is simulated by a roulette mode:
Figure BDA0003436353630000081
in the formula:
Figure BDA0003436353630000082
and
Figure BDA0003436353630000083
are respectively the ithJ' th variable of the universe and the variable selected by the roulette mechanism; NI (U)i) Standard overrun for ith universe; r is1Is a random number between 0 and 1;
substances are not only transferred through white and black holes, but also exchanged through wormholes; the tunnel for setting the wormhole is always established between the universe and the optimal universe, and the wormhole establishment mechanism is expressed by a formula as follows:
Figure BDA0003436353630000084
in the formula: x is the number ofjThe j variable of the current optimal universe; ubjAnd lbjIs a variable xjThe upper and lower limits of (d); r is2，r3，r4Are all random numbers between 0 and 1;
WEP (Wormhole Existence probability) and TDR (traveling Distance rate) are the wormhole Existence probability coefficient and the journey Distance rate, respectively, as shown in the following formulas:
Figure BDA0003436353630000091
TDR＝1-(l/L)1/p (9)
in the formula: l and L are respectively the current iteration times and the maximum generation times, min is the WEP minimum value, max is the WEP maximum value, p defines the detection speed which changes along with the iteration times, and the higher the value of p is, the faster the local detection speed is and the shorter the time consumption is.
From the equations (7) and (8), it can be seen that TDR decreases exponentially, and WEP increases linearly. Before the TDR and the WEP are intersected, the TDR is larger than the WEP, so that the local optimal solution is prevented, after the TDR and the WEP are intersected, the accurate evaluation of the optimal global result is improved in the iterative process along with the reduction of the TDR and the increase of the WEP, and the mechanism is a mechanism for improving the search precision in the iterative process.
The SHEPWM nonlinear equation set of the five-level MPUC inverter is solved by utilizing a multi-universe optimization MVO algorithm, and specific subharmonics which have large influence on torque ripple of the induction motor in the inverter power supply are selectively eliminated, so that the torque ripple of the motor can be effectively inhibited, and the working quality of the motor is improved.
In this embodiment, first, the effect of selective harmonic cancellation of the SHEPWM is verified by taking the three-phase MPUC inverter with inductive load as an example, and simulation parameters are as follows: an electric reactor at the output end of the inverter is 15mH, and the resistance is 5 omega; the dc-side reference voltage is 24V. The harmonics to be eliminated are the 5, 7, 9, 11,17 th harmonics. The modulation range is 0.7-1, in this embodiment, taking the modulation of 0.8 as an example, the MVO algorithm is used to solve the required switching angle, and fig. 5 is a relationship between the objective function and the iteration number. 6-7 are the three-phase inverter output phase voltage and line voltage waveforms and the corresponding FFT waveforms based on the above. The remaining modulation degree line voltages FFT are shown in fig. 7.
As can be seen from fig. 6(a) and 7(a), the inverter output phase voltage is five levels and the line voltage is seven levels; as can be seen from fig. 6(b) and 7(b), the phase voltages do not contain the harmonics 5, 7, 11, 13, 17, while the output line voltages do not contain the above-mentioned cancelled harmonics and multiples of 3 due to the symmetry of the three-phase circuit. FIG. 8 is a graph of line voltage harmonics distribution for different modulation levels.
Building a three-phase MPUC inverter load-resistance physical simulation system with the same simulation parameters, wherein a system main control chip adopts 32-bit DSPTMS320F 28335; the inverter main circuit selects IGBTBSM50GB120DN2 as a power switch device; the oscilloscope model in the experiment was DS 1052E. Fig. 9-10 are experimental waveforms of voltage phase and line voltage of output voltages of three-phase inverters and corresponding FFT waveforms based on simulation.
As shown in fig. 9, the phase voltage changes at five levels, and harmonics to be eliminated in the FFT waveform are effectively suppressed. With respect to the line voltage waveform shown in fig. 10, the line voltage does not contain harmonics of order 3 and multiples thereof, except for the number of levels. The effectiveness of the three-phase MPUC five-level inverter selective harmonic elimination method based on the MVO algorithm is verified through experiments.
In this embodiment, on the basis of the above method, a simulation study is performed on the induction motor powered by variable frequency by using MATLAB; and carrying out simulation research on the torque condition of the three-phase alternating current induction motor by using Maxwell simulation software, wherein the motor parameters are shown in a table 2.
TABLE 2 Motor parameters
Parameter(s) Numerical value
Rated power (kW) 6.6
Rated voltage (V) 380
Winding connection mode Y
Number of poles 4
Rated speed (rpm) 1450
Rated frequency (Hz) 50
The rated voltage signal generated by the inverter is led into a finite element model of the three-phase induction motor. Under the same condition of the modulation degree of 0.8, the first group of SHEPWM control modes is to eliminate 5, 7, 11, 13 and 17 subharmonics; the second group of SHEPWM control modes is to eliminate 17, 19, 23, 25 and 29 subharmonics; the simulation time was 0.5 s. As shown in fig. 11, the stabilized torque waveform is selected as the analysis target. After FFT of the clipped torque, the spectrum of the torque obtained by the normalization process is shown in fig. 11.
As can be seen from fig. 11-12, as the number of harmonics increases, the influence on the motor torque ripple also gradually decreases, i.e., the motor torque is dominated by low order ripple. As can be seen from the torque ripple simulation results in fig. 12, in the case of eliminating harmonics 5, 7, 11, 13, and 17 in the inverter power supply, the harmonic percentages of the torques 6 and 12 of the motor are reduced to 0.17% and 0.05%, respectively, and both are effectively suppressed; there is also a significant content of 18 th harmonic torque because in the phase voltage, only the 17 th harmonic is cancelled out and the 19 th harmonic is not cancelled out. In contrast, the second set of SHEPWM eliminates the 17, 19, 23, 25, 29 harmonics in the phase voltages, which affects the percentage of 18, 24 torque harmonics for the corresponding motor, both down to 0.03%. In contrast, because the harmonics of orders 5, 7, 11, and 13 are not eliminated in the second set of SHEPWM, the percentage of harmonics of orders 6 and 12 of the torque is as high as 16.33% and 1.27%, and the low order ripple of the torque is stronger.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions and scope of the present invention as defined in the appended claims.

Claims (4)

1. A MPUC inverter selective harmonic elimination method based on multivariate universe optimization is characterized in that: the method comprises the following steps:
step 1, analyzing the switching state of a three-phase five-level MPUC inverter, generating different output voltage waveforms by utilizing different power supply voltage amplitudes and different modulation control coordination, and triggering the MPUC inverter by using the states of 1, 3, 5, 7 and 8;
step 2, analyzing the torque ripple characteristic of a power supply induction motor of the three-phase five-level MPUC inverter; selectively eliminating the influence of different power supply harmonics on the motor torque pulsation through comparative analysis;
and 3, searching and detecting the space by adopting a multivariate universe optimization algorithm through two processes of exploration and exploitation to solve the switching angle of the selective harmonic elimination pulse width modulation SHEPWM, so that the selective harmonic elimination of the three-phase five-level MPUC inverter is realized.
2. The MPUC inverter selective harmonic cancellation method based on multivariate cosmic optimization according to claim 1, characterized in that: the step 2 comprises the following steps:
step 2.1, determining the asynchronous torque of a power supply induction motor of the three-phase five-level MPUC inverter;
when the times of air gap harmonic magnetic flux and rotor harmonic current in the three-phase five-level MPUC inverter power supply induction motor are the same, the power supply induction motor influenced by the electromagnetic action can generate asynchronous torque, and the following formula is shown as follows:
Tn,1＝CTφnI2ncosψ2n (1)
wherein, Tn,1To power the asynchronous torque generated by the induction motor,
Figure FDA0003436353620000011
is a torque constant, m1Is the number of motor phases, p is the number of motor pole pairs, N2For each phase turn of the rotor, kw2Is the fundamental wave rotor winding coefficient; phi is anStator flux generated for n time harmonics; psi2nIs composed ofnGenerated electromotive force and rotor harmonic current I2nThe phase difference of (a);
the direction of the asynchronous torque depends on the high-order time harmonic number, when the harmonic number n is 6k +1, k is a natural number, and the direction of the asynchronous torque is the same as the rotating speed; when n is 6k '-1, k' is a natural number not equal to 0, and the direction of asynchronous torque is opposite to the rotating speed;
step 2.2, determining the pulsation torque of a power supply induction motor of the three-phase five-level MPUC inverter;
the pulsating torque of the motor is generated by the interaction of current and magnetic flux of different frequencies in the air gap of the motor; because of the uncertainty of the harmonic times, the ripple torque generated by each set of current and magnetic flux is different, wherein the most important ripple torque is generated by the stator fundamental wave magnetic flux and the rotor harmonic current, and the following formula is shown:
Tn＝2CTφI2ncos[(n±1)ωt-ψ1,2n] (2)
wherein, TnThe pulsating torque generated by the stator fundamental flux and the n-th harmonic current of the rotor, phi being the fundamental flux, psi1,2nThe phase difference between the fundamental electromotive force and the rotor current is shown, omega is the angular frequency of the rotor current, and t is time;
according to the formula (2), in the three-phase five-level MPUC inverter induction motor, the frequency of the ripple torque generated by 5 th and 7 th harmonics is 6f, f is the fundamental frequency output by the three-phase five-level MPUC inverter, and the directions are opposite, namely f- (-5f) ═ 6f and f-7f ═ 6 f; similarly, the frequencies of the pulsating torques generated by the 11 th harmonic and the 13 th harmonic are both 12f, i.e., f- (-11f) ═ 12f and f-13f ═ 12 f; and then obtain the ripple torque that arbitrary subrotor harmonic current and fundamental wave magnetic flux place produced, namely the main ripple torque source is 6 fundamental wave frequencies, therefore the instantaneous ripple torque of the motor is shown as following formula:
T(em)(t)＝T0+T6cos6ωt+T12cos12ωt……T6ncos6nωt (3)
wherein, T(em)(T) instantaneous pulsating torque of the motor, T0For instantaneous ripple torque fundamental amplitude, T6nThe ripple torque generated for the 6n harmonic, n is not equal to 0.
3. The MPUC inverter selective harmonic cancellation method based on multivariate cosmic optimization according to claim 2, characterized in that: the step 3 comprises the following steps:
step 3.1, according to the amplitude of the output voltage waveform of the five-level MPUC inverter and the symmetrical characteristics of the waveform, the nonlinear SHEPWM equation system output by the five-level MPUC inverter is expressed as follows:
Figure FDA0003436353620000021
where M is the amplitude modulation ratio, n is 6 k' -1, alpha is the higher order number of the harmonic to be eliminatedsIs the S-th switching angle in (0, pi/2), S is the total number of switching angles, pkFor position factor, p when the inverter output level riseskIs 1, p when the output level is loweredkIs-1;
step 3.2, converting a nonlinear SHEPWM equation system output by the five-level MPUC inverter into a multi-objective optimization problem;
each sub-equation in the formula (4) is regarded as an optimization objective function, and is respectively denoted as f(1)、f(2)、f(3)、……、f(m)M is the number of equations; converting the multi-objective function of the formula (4) into a single objective function, as shown in the following formula:
Figure FDA0003436353620000022
step 3.3, taking the single objective function minF as the fitness function of the multi-universe optimization algorithm to minimize the fitness function value and obtain the optimal switching angle of SHEPWM
Figure FDA0003436353620000023
4. The MPUC inverter selective harmonic cancellation method based on multivariate cosmic optimization according to claim 3, characterized in that: said step 3.3 comprises the steps of:
3.3.1, initializing iteration times I, switching angle numbers S and universe group numbers U, and calculating a minF value; when the iteration times are less than I, carrying out the next operation;
3.3.2, selecting black holes from the white holes by the particles according to WEP and TDR, and calculating a fitness value;
step 3.3.3, randomly placing u universes in s angles;
3.3.4, based on the standard expansion rate, generating white holes by the roulette rule, and selecting black holes from the white holes according to WEP and TDR by particles; then, updating WEP and TDR continuously according to the fitness value, thereby continuously searching the universe;
step 3.3.5, calculating each switch angle after iteration, and recording an optimal value and an optimal point;
step 3.3.6, updating the calculated switch angle; if the updated optimal universe is superior to the current optimal universe, replacing the current switch angle with each updated switch angle, and updating the optimal universe, otherwise, still keeping the current switch angle and the current optimal universe;
step 3.3.7, recording the optimal value and the optimal point;
step 3.3.8, adding 1 to the iteration times, and returning to step 2 if the iteration times are less than the specified times;
and step 3.3.9, ending.
CN202111613812.XA 2021-12-27 2021-12-27 MPUC inverter selective harmonic elimination method based on multivariate universe optimization Pending CN114257115A (en)

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CN114640263A (en) * 2022-05-11 2022-06-17 广东电网有限责任公司阳江供电局 Energy storage system optimized carrier phase shifting method and system based on space vector embedding
CN114640263B (en) * 2022-05-11 2022-09-02 广东电网有限责任公司阳江供电局 Energy storage system optimized carrier phase shifting method and system based on space vector embedding

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