CN111162680B - Current bias adjusting method and device for direct-drive permanent magnet electric locomotive converter - Google Patents
Current bias adjusting method and device for direct-drive permanent magnet electric locomotive converter Download PDFInfo
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- CN111162680B CN111162680B CN201811324911.4A CN201811324911A CN111162680B CN 111162680 B CN111162680 B CN 111162680B CN 201811324911 A CN201811324911 A CN 201811324911A CN 111162680 B CN111162680 B CN 111162680B
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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
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
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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
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc 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
- H02M7/217—Conversion of ac power input into dc 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
- H02M7/219—Conversion of ac power input into dc 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 in a bridge configuration
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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
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0038—Circuits or arrangements for suppressing, e.g. by masking incorrect turn-on or turn-off signals, e.g. due to current spikes in current mode control
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
The embodiment of the invention provides a method and equipment for adjusting current bias of a direct-drive permanent magnet electric locomotive converter, wherein the method comprises the following steps: sampling alternating current input into the four-quadrant rectifier to obtain alternating current in a sampling period, wherein the alternating current comprises a current value of a positive half period and a current value of a negative half period; acquiring a first sum of the current values of the positive half period and a second sum of the current values of the negative half period, and acquiring a current offset value according to the first sum and the second sum; inputting a first difference value between the current bias value and zero into a first PI controller to obtain a first output value output by the first PI controller; obtaining a pulse width modulation symbol according to the first output value and a second output value output by the PR controller; and controlling the on-off of the IGBT in the four-quadrant rectifier according to the pulse width modulation symbol. The method provided by the embodiment can fundamentally inhibit and eliminate the current bias on the transformer side, so that the influence of the current bias on the control of the four-quadrant converter is eliminated.
Description
Technical Field
The invention relates to the technology of electric locomotive converters, in particular to a method and equipment for adjusting current bias of a direct-drive permanent magnet electric locomotive converter.
Background
The converter comprises a four-quadrant rectifier and an inverter. When the four-quadrant rectifier is subjected to voltage bias due to factors such as devices and control, the four-quadrant converter is unstable, the IGBT device deviates from a rated working area, and large direct current bias is generated on the transformer, so that the working point of the transformer deviates, the temperature rises and the like, the normal operation of the rectifier and the normal operation of the electric locomotive are seriously influenced, and the transformer is damaged or the service life of the transformer is shortened.
In the prior art, a hardware filter circuit design or a software high-pass filter design is adopted to perform hardware filtering on an existing biased alternating-current side current acquisition signal, so that the influence of direct-current bias on a four-quadrant rectifier is eliminated.
However, with the prior art, direct current bias is not fundamentally solved, the four-quadrant rectifier can stably operate, but the transformer still works at a bias point, and the temperature rise of the transformer and other problems brought by the temperature rise are still not solved.
Disclosure of Invention
The embodiment of the invention provides a method and equipment for adjusting current bias of a direct-drive permanent magnet electric locomotive converter, which can be used for fundamentally inhibiting the current bias at the side of a transformer and eliminating the influence of the current bias on the control of a four-quadrant converter.
In a first aspect, an embodiment of the present invention provides a method for adjusting current bias of a converter of a direct-drive permanent magnet electric locomotive, including:
sampling alternating current input into a four-quadrant rectifier to obtain alternating current in a sampling period, wherein the alternating current comprises a current value of a positive half period and a current value of a negative half period;
acquiring a first sum of current values of a positive half period and a second sum of current values of a negative half period, and acquiring a current offset value according to the first sum and the second sum;
inputting a first difference value between the current bias value and zero to a first PI controller to obtain a first output value output by the first PI controller;
obtaining a pulse width modulation symbol according to the first output value and a second output value output by a PR controller, wherein the PR controller is used for controlling the alternating current without static error to enable the period and the phase of the alternating current to be the same as the voltage of a power grid;
and controlling the on-off of an Insulated Gate Bipolar Transistor (IGBT) in the four-quadrant rectifier according to the pulse width modulation symbol.
In one possible design, sampling the ac current input to the four-quadrant rectifier, before obtaining the ac current in the sampling period, further includes:
acquiring a second difference value between the direct-current bus voltage of the four-quadrant rectifier and the instruction voltage;
and inputting the second difference value to a second PI controller, so that a third output value output by the second PI controller is multiplied by an output value of a phase-locked loop to obtain alternating current with the same phase as the power grid voltage, wherein the phase-locked loop is used for controlling the period and the phase of the alternating current to be consistent with the period and the phase of the power grid voltage.
In one possible design, sampling the ac current input to the four-quadrant rectifier to obtain the ac current in a sampling period includes:
sampling alternating current input into a four-quadrant rectifier according to a preset sampling frequency to obtain sampling current, wherein the preset sampling frequency is twice of the on-off frequency of the IGBT;
and obtaining alternating current in a sampling period according to the grid voltage phase determined by the phase-locked loop and the sampling current.
In one possible design, before obtaining the ac current in the sampling period according to the grid voltage phase determined by the phase-locked loop and the sampling current, the method further includes:
filtering the sampling current through a first band-pass filter and a second band-pass filter to obtain filtered sampling current; the first band-pass filter is used for acquiring a main frequency signal of alternating current, and the second band-pass filter is used for filtering interference harmonic waves.
In one possible design, before the first difference between the current bias value and zero is input to the first PI controller and the first output value output by the first PI controller is obtained, the method further includes:
and judging whether the absolute value of the first difference is larger than the absolute value of the current loop width, wherein the obtained judgment result is yes.
In one possible design, deriving the pwm symbol based on the first output value and a second output value output by the PR controller includes:
summing the first output value and the second output value to obtain a third sum value, wherein the first output value is a current variable, and the second output value is a current value;
and obtaining the pulse width modulation symbol according to the third sum and a single-pole frequency doubling pulse modulation mode.
In a second aspect, the present embodiment provides a current bias adjustment device for a converter of a direct-drive permanent magnet electric locomotive, including:
the sampling module is used for sampling alternating current input into the four-quadrant rectifier to obtain alternating current in a sampling period, wherein the alternating current comprises a current value of a positive half period and a current value of a negative half period;
the current inner loop processing module is used for acquiring a first sum of current values of the positive half period and a second sum of current values of the negative half period, and acquiring a current offset value according to the first sum and the second sum;
the current inner loop processing module is further used for inputting a first difference value between the current bias value and zero to a first PI controller, and acquiring a first output value output by the first PI controller;
the pulse width modulation PWM module is used for obtaining a pulse width modulation symbol according to the first output value and a second output value output by a PR controller, and the PR controller is used for controlling the alternating current without static error so that the period and the phase of the alternating current are the same as the voltage of a power grid;
and the pulse width modulation PWM module is also used for controlling the on-off of an Insulated Gate Bipolar Transistor (IGBT) in the four-quadrant rectifier according to the pulse width modulation symbol.
In one possible design, further comprising: a voltage outer loop processing module;
the voltage outer-loop processing module is used for acquiring a second difference value between the direct-current bus voltage of the four-quadrant rectifier and the instruction voltage before sampling the alternating current input into the four-quadrant rectifier to obtain the alternating current in a sampling period;
and inputting the second difference value to a second PI controller, so that a third output value output by the second PI controller is input to a phase-locked loop, and the phase-locked loop is used for controlling the period and the phase of the alternating current to be consistent with the period and the phase of the grid voltage.
In one possible design, further comprising: a filtering module;
the filtering module is used for filtering the sampling current through a first band-pass filter and a second band-pass filter before the alternating current in the sampling period is obtained according to the grid voltage phase determined by the phase-locked loop and the sampling current, so that the filtered sampling current is obtained; the first band-pass filter is used for acquiring a main frequency signal of alternating current, and the second band-pass filter is used for filtering interference harmonic waves.
In a third aspect, the present embodiment provides a current bias adjustment device for a converter of a direct-drive permanent magnet electric locomotive, including:
the FPGA chip and the DSP chip are used for processing the digital signals;
the FPGA chip is used for sampling alternating current input into the four-quadrant rectifier;
the DSP chip is configured to perform the method of any of claims 1 to 6, wherein the method does not include the step of sampling an alternating current input to the four-quadrant rectifier.
The method and the device for adjusting the current bias of the direct-drive permanent magnet electric locomotive converter provided by the embodiment sample the alternating current input into the four-quadrant rectifier to obtain the alternating current in a sampling period, wherein the alternating current comprises a current value of a positive half period and a current value of a negative half period; acquiring a first sum of the current values of the positive half period and a second sum of the current values of the negative half period, and acquiring a current offset value according to the first sum and the second sum; inputting a first difference value between the current bias value and zero into a first PI controller to obtain a first output value output by the first PI controller; obtaining a pulse width modulation symbol according to the first output value and a second output value output by a PR controller, wherein the PR controller is used for carrying out no-static-error control on the alternating current to enable the period and the phase of the alternating current to be the same as the voltage of a power grid; and controlling the on-off of an Insulated Gate Bipolar Transistor (IGBT) in the four-quadrant rectifier according to the pulse width modulation symbol. The second output value is adjusted through the first output value output by the first PI controller to obtain a third sum value, so that direct current bias of alternating current is restrained, the third sum value is modulated in a single-pole frequency-multiplication pulse modulation mode to obtain a pulse width modulation symbol to control the work of the IGBT, the IGBT device is prevented from deviating from a rated working area, and therefore the current bias on the side of the transformer is effectively restrained and eliminated fundamentally, and further the influence of the current bias on the control of the four-quadrant converter is eliminated.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a circuit diagram of a direct drive permanent magnet motor traction system according to an embodiment of the present invention;
FIG. 2 is a partial circuit diagram of a four-quadrant rectifier of a direct-drive permanent magnet electric locomotive according to an embodiment of the present invention;
fig. 3 is a first schematic flow chart of a current bias adjustment method for a converter of a direct-drive permanent magnet electric locomotive according to an embodiment of the present invention;
fig. 4 is a schematic flow chart of a current bias adjustment method of a converter of a direct-drive permanent magnet electric locomotive according to an embodiment of the present invention;
fig. 5 is a third schematic flow chart of a current bias adjustment method for a converter of a direct-drive permanent magnet electric locomotive according to an embodiment of the present invention;
fig. 6 is a first schematic structural diagram of a current bias adjustment device of a converter of a direct-drive permanent magnet electric locomotive according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram ii of a current bias adjustment device of a converter of a direct-drive permanent magnet electric locomotive according to an embodiment of the present invention;
fig. 8 is a schematic diagram of a hardware structure of a current bias adjustment device of a direct-drive permanent magnet electric locomotive converter according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a circuit diagram of a direct-drive permanent magnet motor traction system according to an embodiment of the present invention, and as shown in fig. 1, the direct-drive permanent magnet motor traction system according to the embodiment includes: the system comprises a transformer 10, a pre-charging circuit 20, a four-quadrant rectifier 30, a bus capacitor 40 and an inverter 50; wherein the content of the first and second substances,
the output end of the transformer 10 is connected with the input end of the pre-charging module 20, the output end of the pre-charging module 20 is connected with the input end of the four-quadrant rectifier 30, the output end of the four-quadrant rectifier 30 is connected with one end of the bus capacitor 40, the other end of the bus capacitor 40 is connected with the input end of the inverter 50, and the output end of the inverter 50 is connected with the motor.
The transformer 10 converts the voltage of the power grid to provide the voltage required by the operation of the direct-drive permanent-magnet converter. The pre-charging circuit 20 pre-charges the converter circuit of the direct-drive permanent magnet electric locomotive, and effectively protects devices in the converter circuit of the direct-drive permanent magnet electric locomotive.
The four-quadrant rectifier 30 is a novel rectifier for converting ac current into dc current, and in the embodiment of the present invention, the input current is ac current, and the ac current is converted into dc current through the four-quadrant rectifier 30 as the input current of the bus capacitor 40.
The dc voltage output by the four-quadrant rectifier is referred to as a dc bus voltage, the dc bus voltage fluctuates, the dc current is unstable, the bus capacitor 40 supports the dc bus voltage, the supporting action improves the fluctuation of the circuit to obtain a stable dc voltage, and the stable dc voltage is used as an input voltage of the inverter 50 to supply power to the inverter 50.
The inverter 50 converts the stabilized dc power into ac power and outputs the ac power, and the output ac power controls the motor to operate.
The four-quadrant rectifier in fig. 1 includes an IGBT device, and the IGBT device realizes a function of converting an alternating current into a direct current by the four-quadrant rectifier. The structure of the four-quadrant rectifier will be described with reference to fig. 2.
Fig. 2 is a partial circuit diagram of a four-quadrant rectifier according to an embodiment of the present invention, and as shown in fig. 2, g1, g2, g3, and g4 are IGBT devices of the four-quadrant rectifier, and g1, g2, g3, and g4 cooperate to realize an effect of converting an ac voltage into a dc voltage by the four-quadrant rectifier.
In the embodiment shown in fig. 1 and 2, when the voltage bias occurs to the four-quadrant rectifier due to factors such as devices and control, the four-quadrant converter will be unstable, and the IGBT devices deviate from the rated operating area, and a large direct current bias will be generated on the transformer. This is explained in detail below with reference to fig. 3.
Fig. 3 is a first schematic flow chart of a current bias adjustment method for a converter of a direct-drive permanent magnet electric locomotive according to an embodiment of the present invention, as shown in fig. 3, the method includes:
s301, sampling alternating current input into the four-quadrant rectifier to obtain alternating current in a sampling period, wherein the alternating current comprises a current value of a positive half period and a current value of a negative half period.
Specifically, as shown in fig. 1, according to a preset sampling frequency, an alternating current input to the four-quadrant rectifier 30 is sampled to obtain a plurality of sampling points, and the obtained plurality of sampling points are plotted into a curve to obtain a sine curve or a cosine curve. The preset sampling frequency can be twice or even several times of the on-off frequency of the IGBT or other frequencies, as long as a complete sine or cosine curve can be obtained by sampling according to the preset sampling frequency, and the preset sampling frequency is not particularly limited herein. For example, in this embodiment, the preset sampling frequency may be twice the on-off frequency of the IGBT, and then a sine curve or a cosine curve is drawn from a plurality of sampling points obtained according to the preset sampling frequency, and the sine curve or the cosine curve is divided into a positive half cycle and a negative half cycle according to the phase, for example, the positive half cycle of the sine curve is 0 to pi, the negative half cycle is pi to 2 pi, the values of the plurality of sampling points of the positive half cycle are the values of the positive half cycle of the alternating current, and the values of the plurality of sampling points of the negative half cycle are the values of the negative half cycle of the alternating current.
S302, acquiring a first sum of current values of the positive half period and a second sum of current values of the negative half period, and acquiring a current offset value according to the first sum and the second sum.
Specifically, the values of the plurality of sampling points in the positive half period are summed to obtain a first sum P, the values of the plurality of sampling points in the negative half period are summed to obtain a second sum N, the absolute value of the P and N is subjected to difference calculation, and the obtained difference is Q. If the Q value is 0, the absolute values of the P value and the N value are considered to be completely equal, the positive half period and the negative half period of the sine curve or the cosine curve are completely symmetrical, and the alternating current has no direct current bias. If the Q value is not 0, the absolute values of the P value and the N value are not equal, the positive half period and the negative half period of the sine curve or the cosine curve are asymmetric, the alternating current has direct current bias, and the Q value is the direct current bias value.
And S303, inputting a first difference value between the current bias value and zero to a first PI controller, and acquiring a first output value output by the first PI controller.
Specifically, the direct current offset value Q and zero are input into a first PI controller, the first PI controller forms a control deviation according to the direct current offset value Q and zero, the proportion and the integral of the deviation are combined linearly to form a control quantity, the alternating current is controlled, and the direct current offset of the alternating current is eliminated. The control quantity is the first output value.
S304, obtaining a pulse width modulation symbol according to the first output value and a second output value output by a PR controller, wherein the PR controller is used for controlling the alternating current without static error, and the period and the phase of the alternating current are the same as the voltage of a power grid.
Specifically, the alternating current is input to the PR controller, and after the phase and the period of the alternating current are ensured to be the same as the voltage of the power grid, a stable output alternating current, that is, a second output value, is obtained. And summing the first output value and the second output value to obtain a third sum value. Namely, the control quantity obtained by the first PI controller adjusts the stable output alternating current, thereby inhibiting the direct current bias of the alternating current. And modulating the third sum value by using a unipolar frequency multiplication pulse modulation mode to obtain a pulse width modulation symbol.
S305, controlling the on-off of an Insulated Gate Bipolar Transistor (IGBT) in the four-quadrant rectifier according to the pulse width modulation symbol.
Specifically, in conjunction with fig. 3, the pulse width modulation symbols are used as inputs to the insulated gate bipolar transistors IGBTs g1, g2, g3, and g4 in the four-quadrant rectifier to control the switching of the bipolar transistors IGBTs.
The current bias adjusting method for the direct-drive permanent magnet electric locomotive converter provided by the embodiment is characterized in that alternating current input into a four-quadrant rectifier is sampled to obtain alternating current in a sampling period, wherein the alternating current comprises a current value of a positive half period and a current value of a negative half period; acquiring a first sum of the current values of the positive half period and a second sum of the current values of the negative half period, and acquiring a current offset value according to the first sum and the second sum; inputting a first difference value between the current bias value and zero into a first PI controller to obtain a first output value output by the first PI controller; obtaining a pulse width modulation symbol according to the first output value and a second output value output by the PR controller, wherein the PR controller is used for carrying out no-static-error control on the alternating current to enable the period and the phase of the alternating current to be the same as the voltage of a power grid; and controlling the on-off of an Insulated Gate Bipolar Transistor (IGBT) in the four-quadrant rectifier according to the pulse width modulation symbol. The second output value is adjusted through the first output value output by the first PI controller to obtain a third sum value, so that direct current bias of alternating current is restrained, the third sum value is modulated in a single-pole frequency-multiplication pulse modulation mode to obtain a pulse width modulation symbol to control the work of the IGBT, the IGBT device is prevented from deviating from a rated working area, and therefore the current bias on the side of the transformer is effectively restrained and eliminated fundamentally, and further the influence of the current bias on the control of the four-quadrant converter is eliminated.
Fig. 4 is a schematic flow diagram of a second method for adjusting current bias of a direct-drive permanent magnet electric locomotive converter according to an embodiment of the present invention, and fig. 5 is a schematic flow diagram 3 of a method for adjusting current bias of a direct-drive permanent magnet electric locomotive converter according to an embodiment of the present invention, where as shown in fig. 5, Udc is a dc bus voltage, a wave trap mainly filters a fluctuation value of the dc bus voltage Udc, Udc is an instruction voltage, i is an alternating current input to a four-quadrant rectifier, and Us is a voltage of the alternating current input to the four-quadrant rectifier, and with reference to fig. 5, the present embodiment describes in detail a specific implementation process of the present embodiment on the basis of the embodiment of fig. 3. As shown in fig. 4, the method includes:
s401, sampling alternating current input into the four-quadrant rectifier according to a preset sampling frequency to obtain sampling current, wherein the preset sampling frequency is twice of the on-off frequency of the IGBT.
S401 provided in this embodiment is similar to S301 in the embodiment of fig. 3, and this embodiment is not described herein again.
S402, filtering the sampling current through a first band-pass filter and a second band-pass filter to obtain a filtered sampling current; the first band-pass filter is used for acquiring a main frequency signal of alternating current, and the second band-pass filter is used for filtering interference harmonic waves.
Specifically, in consideration of the difference of the main frequencies of the alternating current in different regions, the passband frequency of the first bandpass filter is set between 40Hz and 60Hz, for example, in this embodiment, the passband frequency of the first bandpass filter is 45 Hz to 55Hz, and optionally, when the main frequency of the alternating current is 50Hz, the passband frequency of the first bandpass filter is set to 50Hz for obtaining the main frequency signal of the alternating current. Similarly, in this embodiment, the switching frequency of the four-quadrant rectifier is f, that is, the on-off frequency of the IGBT is f, the passband frequency of the second band-pass filter is 2f/50 ± 5Hz, and the second band-pass filter is used for filtering higher harmonic interference. The first and second band pass filters are the filters in fig. 5.
And S403, acquiring a second difference value between the direct-current bus voltage of the four-quadrant rectifier and the instruction voltage, and inputting the second difference value to a second PI controller, so that a third output value output by the second PI controller is multiplied by an output value of a phase-locked loop, wherein the phase-locked loop is used for obtaining a power grid voltage phase, and thus alternating current with the same period and phase as the power grid voltage is obtained.
Specifically, the direct-current bus voltage Udc and the command voltage Udc are input to the second PI controller, and the second PI controller linearly combines the proportion and the integral of the deviation according to the deviation between the direct-current bus voltage Udc and the command voltage Udc to form a control quantity, wherein the control quantity is a third output value output by the second PI controller. And multiplying a third output value output by the second PI controller by the output of the phase-locked loop to obtain the alternating current with the same phase as the voltage of the power grid. The phase-locked loop, i.e. the PLL of fig. 5, is used to control the period and phase of the alternating current i and the period and phase of the grid voltage to be in agreement. And calculating the phase of the power grid voltage according to the phase controlled by the phase-locked loop. The second PI controller in S403 is the second PI in fig. 5.
S404, obtaining alternating current in a sampling period according to the grid voltage phase determined by the phase-locked loop and the sampling current, wherein the alternating current comprises a current value of a positive half period and a current value of a negative half period.
Specifically, the phase of the grid voltage is calculated according to the phase controlled by the phase-locked loop PLL, the phase of the alternating current i is determined, and the phase of the sampling current is also determined, the sampling current is divided into a positive half cycle and a negative half cycle according to the phase, for example, the positive half cycle of a sine curve is 0 to pi, the negative half cycle is pi to 2 pi, the values of a plurality of sampling points of the positive half cycle are the values of the positive half cycle of the alternating current i, and the values of a plurality of sampling points of the negative half cycle are the values of the negative half cycle of the alternating current i. S404 is the dc offset extraction calculation in fig. 5.
S405, acquiring a first sum of the current values of the positive half cycle and a second sum of the current values of the negative half cycle, and acquiring a current offset value according to the first sum and the second sum.
S405 in this embodiment is similar to S302 in the embodiment of fig. 3, and S405 is also the dc offset extraction calculation in fig. 5, which is not described herein again.
S406, judging whether the absolute value of the first difference is larger than the absolute value of the current loop width, wherein the obtained judgment result is yes.
Specifically, to avoid the first difference Q from having an error due to a sampling error, the Q value and the hysteresis loop width are calculated, and the hysteresis loop width may be ± 5A, or may be any other value as long as the first difference Q can be avoided from having an error. For example, in the present embodiment, the hysteresis loop width is ± 5A; the absolute value of the first difference Q is greater than 5A, and the obtained judgment result is yes, that is, the alternating current has the direct current offset. Specifically, the first difference Q is greater than 5A, a positive dc bias exists for the ac current, the first difference Q is less than-5A, and a negative dc bias exists for the ac current.
And S407, inputting a first difference value between the current bias value and zero to a first PI controller, and acquiring a first output value output by the first PI controller.
S407 provided in this embodiment is similar to S303 in the embodiment of fig. 3, and the first PI controller in S407 is the first PI in fig. 5, which is not described herein again.
S408, summing the first output value and a second output value output by the PR control to obtain a third sum value, wherein the first output value is a current variable, and the second output value is a current value; and obtaining the pulse width modulation symbol according to the third sum and a single-pole frequency doubling pulse modulation mode.
S408 provided in this embodiment is similar to S304 in the embodiment of fig. 3, and the PR controller in S408 is a PR in fig. 5, which is not described herein again.
And S409, controlling the on-off of the insulated gate bipolar transistor IGBT in the four-quadrant rectifier according to the pulse width modulation symbol.
S409 provided in this embodiment is similar to S305 in the embodiment of fig. 3, and is similar to the pulse modulation in fig. 5, and this embodiment is not described herein again.
According to the current bias adjusting method for the direct-drive permanent magnet electric locomotive converter, provided by the embodiment of the invention, the alternating current is sampled to obtain the sampled current, then the second difference value of the direct current bus voltage and the instruction voltage is input to the second PI controller to obtain the third output value output by the second PI controller, and the third output value is used for adjusting the alternating current. After the third output value is multiplied by the output value of the phase-locked loop, the phase of the alternating current is determined according to the phase of the power grid voltage calculated by the phase-locked loop, the phase of the sampling current is further determined, the sampling current is divided into a positive half period and a negative half period, the current value of the positive half period and the current value of the negative half period are calculated, then a first difference value of the current value of the positive half period and the current value of the negative half period is input into a first PI controller, a second output value output by the PR controller is adjusted through the first output value output by the first PI controller, a third sum value is obtained, the direct current bias of the alternating current is restrained, the third sum value is modulated in a single-pole frequency doubling pulse modulation mode, the work of the pulse width modulation sign control IGBT is obtained, the IGBT device is prevented from deviating from a rated working area, and the current bias of the transformer side is effectively restrained and, and further eliminating the influence of current bias on the control of the four-quadrant converter.
Further, the current bias adjusting method for the direct-drive permanent magnet electric locomotive converter improves the response speed of direct current bias suppression, adopts a software control algorithm to solve direct current bias, saves hardware circuit design, and solves the problem that other direct current bias suppression methods are not suitable for wide-frequency change of the voltage frequency of a power grid.
Fig. 6 is a first schematic structural diagram of a current bias adjustment device of a converter of a direct-drive permanent magnet electric locomotive according to an embodiment of the present invention. As shown in fig. 6, the current bias adjusting device 60 of the direct-drive permanent magnet electric locomotive converter comprises: a sampling module 601, a current inner loop processing module 602, and a Pulse Width Modulation (PWM) module 603.
The sampling module 601 is configured to sample an alternating current input to the four-quadrant rectifier to obtain an alternating current in a sampling period, where the alternating current includes a current value of a positive half cycle and a current value of a negative half cycle;
a current inner loop processing module 602, configured to obtain a first sum of current values of the positive half cycle and a second sum of current values of the negative half cycle, and obtain a current offset value according to the first sum and the second sum;
the current inner loop processing module 602 is further configured to input a first difference between the current bias value and zero to a first PI controller, and obtain a first output value output by the first PI controller;
a PWM module 603 configured to obtain a PWM symbol according to the first output value and a second output value output by the PR controller, where the PR controller is configured to perform non-static control on the ac current, so that a period and a phase of the ac current are the same as a grid voltage.
And the Pulse Width Modulation (PWM) module 603 is further configured to control on/off of an Insulated Gate Bipolar Transistor (IGBT) in the four-quadrant rectifier according to the pulse width modulation symbol.
The device of this embodiment may be configured to execute the technical solution of the method embodiment shown in fig. 3, and the implementation principle and the technical effect are similar, which are not described herein again.
Fig. 7 is a schematic structural diagram of a current bias adjusting device of a converter of a direct-drive permanent magnet electric locomotive according to an embodiment of the present invention. On the basis of the embodiment of fig. 6, the present embodiment further includes: a voltage outer loop processing module 604, a filtering module 605.
Optionally, the voltage outer loop processing module 604 is configured to:
sampling the alternating current input into the four-quadrant rectifier, and acquiring a second difference value between the direct current bus voltage of the four-quadrant rectifier and the instruction voltage before the alternating current in a sampling period is obtained;
inputting the second difference value to a second PI controller, so that a third output value output by the second PI controller is input to a phase-locked loop, wherein the phase-locked loop is used for controlling the period and the phase of the alternating current and the period and the phase of the grid voltage to be consistent;
optionally, the sampling module 601 is specifically configured to:
sampling alternating current input into a four-quadrant rectifier according to a preset sampling frequency to obtain sampling current, wherein the preset sampling frequency is twice of the on-off frequency of the IGBT;
obtaining alternating current in a sampling period according to the grid voltage phase determined by the phase-locked loop and the sampling current;
optionally, the filtering module 605 is configured to:
before the alternating current in the sampling period is obtained according to the grid voltage phase determined by the phase-locked loop and the sampling current,
filtering the sampling current through a first band-pass filter and a second band-pass filter to obtain filtered sampling current; the first band-pass filter is used for acquiring a main frequency signal of alternating current, and the second band-pass filter is used for filtering interference harmonic waves;
optionally, the current inner loop processing module 602 is further configured to:
before a first difference value between the current bias value and zero is input to a first PI controller and a first output value output by the first PI controller is obtained,
and judging whether the absolute value of the first difference is larger than the absolute value of the current loop width, wherein the obtained judgment result is yes.
Optionally, the PWM module 603 is specifically configured to:
obtaining a pulse width modulation symbol according to the first output value and a second output value output by the PR controller
Summing the first output value and the second output value to obtain a third sum value, wherein the first output value is a current variable, and the second output value is a current value;
and obtaining the pulse width modulation symbol according to the third sum and a single-pole frequency doubling pulse modulation mode.
The device of this embodiment may be configured to execute the technical solution of the method embodiment shown in fig. 4, and the implementation principle and the technical effect are similar, which are not described herein again.
Fig. 8 is a schematic diagram of a hardware structure of a current bias adjustment device of a direct-drive permanent magnet electric locomotive converter according to an embodiment of the present invention. As shown in fig. 8, the current bias adjusting device 80 of the direct-drive permanent magnet electric locomotive converter of the embodiment includes: a field programmable gate array FPGA chip 801 and a digital signal processing DSP chip 802; wherein the content of the first and second substances,
the FPGA chip 801 is used for sampling alternating current input into the four-quadrant rectifier; specifically, in this embodiment, the FPGA samples the ac current input to the four-quadrant rectifier at a high speed, and stores and updates the sampled ac current value in the FPGA register.
The DSP chip 802 is configured to perform the method of any of claims 1 to 6 wherein the method does not include the step of sampling the ac current input to the four-quadrant rectifier. Specifically, in the present embodiment, an ac current sampling period interrupt is set in the DSP, and when the interrupt comes, the sampled ac current value is read from the FPGA register and the operation involved in the method according to any one of claims 1 to 6 is performed.
Those of ordinary skill in the art will understand that: all or a portion of the steps of implementing the above-described method embodiments may be performed by hardware associated with program instructions. The program may be stored in a computer-readable storage medium. When executed, the program performs steps comprising the method embodiments described above; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled 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; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (5)
1. A current bias adjusting method for a direct-drive permanent magnet electric locomotive converter is characterized by comprising the following steps:
sampling alternating current input into a four-quadrant rectifier according to a preset sampling frequency to obtain sampling current, wherein the preset sampling frequency is twice of the on-off frequency of an Insulated Gate Bipolar Transistor (IGBT);
filtering the sampling current through a first band-pass filter and a second band-pass filter to obtain filtered sampling current; the first band-pass filter is used for acquiring a main frequency signal of the alternating current, and the second band-pass filter is used for filtering interference harmonics;
acquiring a second difference value between the direct-current bus voltage of the four-quadrant rectifier and the instruction voltage, and inputting the second difference value to a second PI controller, so that a third output value output by the second PI controller is multiplied by an output value of a phase-locked loop to obtain alternating current with the same phase as the power grid voltage, wherein the phase-locked loop is used for controlling the period and the phase of the alternating current to be consistent with the period and the phase of the power grid voltage;
according to the grid voltage phase determined by the phase-locked loop and the filtered sampling current, obtaining alternating current in a sampling period, wherein the alternating current in the sampling period comprises a current value of a positive half period and a current value of a negative half period;
acquiring a first sum of the current values of the positive half period and a second sum of the current values of the negative half period, and acquiring a current offset value according to the first sum and the second sum;
inputting a first difference value between the current bias value and zero to a first PI controller, and acquiring a first output value output by the first PI controller, wherein the first difference value is used for representing control deviation, and the first output value is a current variable;
obtaining a pulse width modulation symbol according to the first output value and a second output value output by a PR controller, wherein the PR controller is used for controlling the alternating current without static error to enable the period and the phase of the alternating current to be the same as the voltage of the power grid;
and controlling the on-off of the IGBT in the four-quadrant rectifier according to the pulse width modulation symbol.
2. The method of claim 1, wherein prior to inputting a first difference between the current bias value and zero to a first PI controller and obtaining a first output value output by the first PI controller, the method further comprises:
and judging whether the absolute value of the first difference is larger than the absolute value of the width of the hysteresis loop, wherein the obtained judgment result is yes.
3. The method of claim 1, wherein deriving a pulse width modulation symbol from the first output value and a second output value output by a PR controller comprises:
summing the first output value and the second output value to obtain a third sum value, wherein the second output value is a current value;
and obtaining the pulse width modulation symbol according to the third sum and a single-pole frequency doubling pulse modulation mode.
4. The utility model provides a direct drive permanent magnetism electric locomotive converter current bias adjusting device which characterized in that includes:
the sampling module is used for sampling alternating current input into the four-quadrant rectifier according to a preset sampling frequency to obtain sampling current, wherein the preset sampling frequency is twice of the on-off frequency of an Insulated Gate Bipolar Transistor (IGBT);
the filtering module is used for filtering the sampling current through a first band-pass filter and a second band-pass filter to obtain a filtered sampling current; the first band-pass filter is used for acquiring a main frequency signal of the alternating current, and the second band-pass filter is used for filtering interference harmonics;
the voltage outer loop processing module is used for acquiring a second difference value between the direct-current bus voltage of the four-quadrant rectifier and the instruction voltage, inputting the second difference value to a second PI controller, and multiplying a third output value output by the second PI controller by an output value of a phase-locked loop to obtain alternating current with the same phase as the power grid voltage, wherein the phase-locked loop is used for controlling the period and the phase of the alternating current to be consistent with the period and the phase of the power grid voltage;
the sampling module is further configured to obtain an alternating current in a sampling period according to the grid voltage phase determined by the phase-locked loop and the filtered sampling current, where the alternating current in the sampling period includes a current value of a positive half-cycle and a current value of a negative half-cycle;
the current inner loop processing module is used for acquiring a first sum of the current values of the positive half period and a second sum of the current values of the negative half period and acquiring a current offset value according to the first sum and the second sum;
the current inner loop processing module is further configured to input a first difference value between the current bias value and zero to a first PI controller, and obtain a first output value output by the first PI controller, where the first difference value is used to represent a control deviation, and the first output value is a current variable;
the pulse width modulation PWM module is used for obtaining a pulse width modulation symbol according to the first output value and a second output value output by a PR controller, and the PR controller is used for controlling the alternating current without static error so that the period and the phase of the alternating current are the same as the voltage of the power grid;
and the pulse width modulation PWM module is also used for controlling the on-off of the IGBT in the four-quadrant rectifier according to the pulse width modulation symbol.
5. The utility model provides a direct drive permanent magnetism electric locomotive converter current bias adjusting device which characterized in that includes:
the FPGA chip and the DSP chip are used for processing the digital signals;
the FPGA chip is used for sampling alternating current input into the four-quadrant rectifier;
the DSP chip is configured to perform the method of any of claims 1 to 3, wherein the method does not include the step of sampling an alternating current input to the four-quadrant rectifier.
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