CN112953184A - Input current harmonic suppression method of UPS (uninterrupted Power supply) with PWM (pulse-width modulation) rectifier - Google Patents
Input current harmonic suppression method of UPS (uninterrupted Power supply) with PWM (pulse-width modulation) rectifier Download PDFInfo
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- CN112953184A CN112953184A CN202110251468.8A CN202110251468A CN112953184A CN 112953184 A CN112953184 A CN 112953184A CN 202110251468 A CN202110251468 A CN 202110251468A CN 112953184 A CN112953184 A CN 112953184A
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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
- H02M1/12—Arrangements for reducing harmonics from ac input or output
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
- H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
- H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
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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
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Abstract
The invention discloses an input current harmonic suppression method of a UPS with a PWM rectifier, which comprises the following steps: sampling the voltage of the direct current bus, and selecting proper feedback quantity according to the result of low-pass filtering processing of the voltage of the direct current bus to construct a voltage control loop; sampling the current at the network side and respectively constructing a current control loop by using the current components after DQ conversion; after the band-pass filtering processing and the feedforward processing are added after the current control loop, the inversely transformed quantity is transmitted to the PWM modulator so as to modulate a PWM signal for controlling the PWM rectifier. The input current harmonic suppression method can enable the input current to have smaller harmonic when the UPS load condition changes, and maintain better output dynamic characteristics.
Description
Technical Field
The invention relates to the technical field of UPS, in particular to an input current harmonic suppression method of UPS with a PWM rectifier.
Background
With the rapid development of power electronic technology, the UPS is widely applied to various occasions with high requirements on power supply reliability, for example, in the field of communication, the UPS can be used as a key load to supply power, so that various high-power switching devices are widely applied. In addition, with the higher and higher requirements of the information era on the quality of the power grid, harmonic suppression and reactive compensation have important significance for improving the quality of the power grid, improving the utilization rate of electric energy and maintaining the stability of a power system.
Theoretically, the current loop adopting the PI control algorithm can realize that the input current of the rectifier has a better waveform in a steady state, but because the UPS output power may have variation, the output bus ripple voltage of the PWM rectifier can be caused to vary along with the UPS load variation, if the output of the PWM rectifier is still controlled according to the traditional control strategy, the waveform of the input current of the PWM rectifier is poor, the harmonic wave becomes large, and the national standard requirement is not met.
Disclosure of Invention
The present invention is directed to solve the above-mentioned problems, and an object of the present invention is to provide a method for suppressing input current harmonics in a UPS having a PWM rectifier, which can make the input current have smaller harmonics and maintain better output dynamic characteristics when the UPS load condition changes.
In order to achieve the purpose, the invention adopts the following technical scheme: a method of input current harmonic suppression for a UPS having a PWM rectifier, comprising: step 1: sampling DC bus voltage V of PWM rectifierbus(ii) a Step 2: DC bus voltage VbusLow-pass filtering to obtain low-pass filtered bus voltage Ubus(ii) a If VbusAnd UbusIs less than a preset threshold value UBus_refThen use UbusConstructing a voltage control loop for the feedback quantity, otherwise VbusConstructing a voltage control loop for the feedback quantity; and step 3: grid-side three-phase current I of sampling PWM rectifierRec_R、IRec_s、IRec_TAnd performing abc/DQ conversion on the three-phase current on the grid side to obtain a current component I under a DQ coordinate systemRec_d、IRec_q(ii) a And 4, step 4: with said voltage control loopThe output quantity of the circuit is given as IRec_dConstructing a first current control loop for the feedback quantity; given amount of 0, given as IRec_qConstructing a second current control loop for the feedback quantity; and 5: respectively performing band-pass filtering processing on the output quantities of the first current control loop and the second current control loop, and respectively outputting the output quantities of the two current control loops after subtracting the corresponding output quantities subjected to the band-pass filtering processing; step 6: grid-side three-phase voltage U of sampling PWM rectifierGrid_R、UGrid_s、UGrid_TAnd performing abc/DQ conversion on the three-phase voltage on the grid side to obtain a voltage component U under a DQ coordinate systemGrid_d、UGrid_q(ii) a And 7: introducing feedforward treatment to both output quantities of the step 5; wherein the feed forward quantity introduced corresponding to the output quantity of the first current control loop is UGrid_dThe feedforward quantity introduced corresponding to the output quantity of the second current control loop is UGrid_q(ii) a And 8: and (3) carrying out dq/abc inverse transformation or dq/alpha beta inverse transformation on the two output quantities introduced into the feedforward processing in the step (7), and transmitting the transformation result to a PWM (pulse-width modulation) modulator so as to modulate a PWM signal for controlling the PWM rectifier.
Further, the step 1, the step 3 and the step 6 are carried out simultaneously.
Further, the given amount of the voltage control loop is the preset threshold UBus_ref。
Further, the voltage control loop, the first current control loop and the second current control loop are all PI control loops.
Further, the PWM modulator is an SPWM modulator or an SVPWM modulator.
Compared with the prior art, the invention has the following beneficial effects:
the harmonic suppression method of the input current provided by the invention adopts two more important technical means to reduce the harmonic of the input current, wherein one is to sample the direct current bus voltage and carry out low-pass filtering processing on the direct current bus voltage, and then select different feedback quantities according to the result of the low-pass filtering processing to construct a voltage control loop so as to control the bus voltage, and the other is to add a link of band-pass filtering processing behind the current control loop and adopt the difference value of the unprocessed output quantity and the output quantity subjected to the band-pass filtering processing to carry out subsequent control.
Specifically, the invention first samples the DC bus voltage V before constructing the voltage control loop for controlling the DC bus voltagebusLow-pass filtering to obtain low-pass filtered bus voltage UbusAnd then selecting an appropriate amount as a feedback amount according to the difference between the two to construct the voltage control loop. If the difference value between the two is small, the direct current bus voltage is stable, the voltage ripple is small, and therefore the output dynamic characteristic of the UPS can be still guaranteed even if the control process is in a certain hysteresis state, and at the moment, the U subjected to low-pass filtering processing is selectedbusAs a feedback quantity, the bus voltage can be controlled to be more stable and the voltage ripple is smaller, so that the harmonic wave of the input current is reduced; if the difference value of the two is larger, the direct current bus voltage is unstable and the voltage ripple is larger, and V which is not subjected to low-pass filtering processing is selected at the momentbusAs a feedback quantity, the control loop has a quick response characteristic so that the bus voltage can be quickly stabilized, and the output dynamic characteristic of the UPS can be ensured while the voltage ripple is reduced so that the harmonic wave of the input current is reduced.
In addition, the band-pass filtering processing is added after the current control loop, so that the situation that the input current enters a resonance point of an LCL filter of the UPS when the input current has harmonic waves can be avoided, the whole UPS is in a resonance state, and the harmonic waves are further increased.
Therefore, the two technical means adopted by the invention can reduce the harmonic level of the input current when the UPS load condition changes, and maintain better output dynamic characteristics.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a control loop according to an embodiment of the present invention.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. It is to be understood that the described embodiments are presently preferred embodiments of the invention and are not to be taken as an exclusion of other embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
In the claims, the specification and the drawings of the present invention, the terms "including", "having" and their variants, if used, are intended to be inclusive and not limiting.
Referring to fig. 1, an embodiment of the present invention provides an input current harmonic suppression method for a UPS having a PWM rectifier, which can make the input current have smaller harmonics when the UPS load condition changes. The method comprises the following steps:
step 1: sampling DC bus voltage V of output end of PWM rectifierbus。
Step 2: will direct current bus voltage VbusAnd transmitting the voltage control loop to an f (Ubus) function module, and constructing the voltage control loop by using the output quantity of the f (Ubus) function module. Specifically, in the f (ubus) function module, the dc bus voltage V is first compared with the dc bus voltage VbusLow-pass filtering to obtain low-pass filtered bus voltage UbusThen according to VbusAnd UbusThe difference value of (a) is selected as a feedback quantity to construct the voltage control loop. Wherein, if VbusAnd UbusIs less than a preset threshold value UBus_refThen use UbusConstructing a voltage control loop for the feedback quantity, otherwise VbusA voltage control loop is constructed for the feedback quantity. In this embodiment, the given amount of the voltage control loop is the preset threshold UBus_refAnd the voltage control loop is a PI control loop.
And step 3: sampling PWM rectificationThree-phase current I on grid side of deviceRec_R、IRec_S、IRec_TAnd performing abc/DQ conversion on the three-phase current on the grid side to obtain a current component I under a DQ coordinate systemRec_d、IRec_q. The abc/dq transformation is Park transformation, which is the prior art, and thus the present invention is not described in detail.
And 4, step 4: given by the output of the voltage control loop, by IRec_dConstructing a first current control loop for the feedback quantity; given amount of 0, given as IRec_qA second current control loop is constructed for the feedback quantity. In this embodiment, the first current control loop and the second current control loop are both PI control loops. Therefore, the first current control loop and the voltage control loop form a double closed loop control loop, wherein the voltage control loop of the outer loop is mainly used for controlling the stability of the direct current bus voltage, and the current control loop of the inner loop is used for controlling the current according to the output result of the voltage control loop.
And 5: as shown in the BPF band-pass filter in fig. 1, the output quantities of the first current control loop and the second current control loop are respectively subjected to band-pass filtering, and the output quantities of the two current control loops are subtracted from the corresponding output quantities subjected to the band-pass filtering and then are respectively output. In other words, the output quantity of the current control loop is a, B is obtained after the band-pass filtering processing, and the output quantity of the step 5 is a-B corresponding to the two current control loops.
Step 6: grid-side three-phase voltage U of sampling PWM rectifierGrid_R、UGrid_S、UGrid_TAnd performing abc/DQ conversion on the three-phase voltage on the grid side to obtain a voltage component U under a DQ coordinate systemGrid_d、UGrid_q。
And 7: feed forward processing is introduced for both outputs of step 5. Wherein, as shown in fig. 1, the feed forward quantity introduced corresponding to the output quantity of the first current control loop is UGrid_dThe feedforward quantity introduced corresponding to the output quantity of the second current control loop is UGrid_q。
And 8: and (3) carrying out dq/abc inverse transformation or dq/alpha beta inverse transformation on the two output quantities introduced into the feedforward processing in the step (7), and transmitting the transformation result to a PWM (pulse-width modulation) modulator so as to modulate a PWM signal for controlling the PWM rectifier. In this embodiment, the PWM modulator is an SPWM modulator or an SVPWM modulator.
It should be noted that, in the embodiment of the present invention, the sampling steps performed in step 1, step 3, and step 6 may be performed simultaneously, or may be performed before the corresponding other steps.
It can be seen that, in the harmonic suppression method in the embodiment of the present invention, two important technical means are adopted to reduce the harmonic of the input current, one is to sample the dc bus voltage and perform low-pass filtering on the dc bus voltage, and then select different feedback quantities according to the result of the low-pass filtering to construct a voltage control loop to control the bus voltage, and the other is to add a link of band-pass filtering processing behind the current control loop, and perform subsequent control by using the difference between the unprocessed output quantity and the output quantity subjected to the band-pass filtering processing.
Specifically, the invention first samples the DC bus voltage V before constructing the voltage control loop for controlling the DC bus voltagebusLow-pass filtering to obtain low-pass filtered bus voltage UbusAnd then selecting an appropriate amount as a feedback amount according to the difference between the two to construct the voltage control loop. If the difference value between the two is small, the direct current bus voltage is stable, the voltage ripple is small, and therefore the output dynamic characteristic of the UPS can be still guaranteed even if the control process is in a certain hysteresis state, and at the moment, the U subjected to low-pass filtering processing is selectedbusAs a feedback quantity, the bus voltage can be controlled to be more stable and the voltage ripple is smaller, so that the harmonic wave of the input current is reduced; if the difference value of the two is larger, the direct current bus voltage is unstable and the voltage ripple is larger, and V which is not subjected to low-pass filtering processing is selected at the momentbusAs a feedback quantity, the control loop has a quick response characteristic so that the bus voltage can be quickly stabilized, and the output dynamic characteristic of the UPS can be ensured while the voltage ripple is reduced so that the harmonic wave of the input current is reduced.
In addition, the band-pass filtering processing is added after the current control loop, so that the situation that the input current enters a resonance point of an LCL filter of the UPS when the input current has harmonic waves can be avoided, the whole UPS is in a resonance state, and the harmonic waves are further increased.
Therefore, the two technical means adopted by the invention can reduce the harmonic level of the input current when the UPS load condition changes, and maintain better output dynamic characteristics.
The description of the above specification and examples is intended to be illustrative of the scope of the present invention and is not intended to be limiting. Modifications, equivalents and other improvements which may occur to those skilled in the art and which may be made to the embodiments of the invention or portions thereof through a reasonable analysis, inference or limited experimentation, in light of the common general knowledge, the common general knowledge in the art and/or the prior art, are intended to be within the scope of the invention.
Claims (5)
1. A method of input current harmonic suppression for a UPS having a PWM rectifier, comprising:
step 1: sampling DC bus voltage V of PWM rectifierbus；
Step 2: DC bus voltage VbusLow-pass filtering to obtain low-pass filtered bus voltage Ubus(ii) a If VbusAnd UbusIs less than a preset threshold value UBus_refThen use UbusConstructing a voltage control loop for the feedback quantity, otherwise VbusConstructing a voltage control loop for the feedback quantity;
and step 3: grid-side three-phase current I of sampling PWM rectifierRec_R、IRec_S、IRec_TAnd performing abc/DQ conversion on the three-phase current on the grid side to obtain a current component I under a DQ coordinate systemRec_d、IRec_q；
And 4, step 4: given by the output of the voltage control loop, by IRec_dConstructing a first current control loop for the feedback quantity; given amount of 0, given as IRec_qIs reversedFeeding quantity to construct a second current control loop;
and 5: respectively performing band-pass filtering processing on the output quantities of the first current control loop and the second current control loop, and respectively outputting the output quantities of the two current control loops after subtracting the corresponding output quantities subjected to the band-pass filtering processing;
step 6: grid-side three-phase voltage U of sampling PWM rectifierGrid_R、UGrid_S、UGrid_TAnd performing abc/DQ conversion on the three-phase voltage on the grid side to obtain a voltage component U under a DQ coordinate systemGrid_d、UGrid_q；
And 7: introducing feedforward treatment to both output quantities of the step 5; wherein the feed forward quantity introduced corresponding to the output quantity of the first current control loop is UGrid_dThe feedforward quantity introduced corresponding to the output quantity of the second current control loop is UGrid_q；
And 8: and (3) carrying out dq/abc inverse transformation or dq/alpha beta inverse transformation on the two output quantities introduced into the feedforward processing in the step (7), and transmitting the transformation result to a PWM (pulse-width modulation) modulator so as to modulate a PWM signal for controlling the PWM rectifier.
2. The method of input current harmonic suppression for a UPS having a PWM rectifier of claim 1, wherein: and the step 1, the step 3 and the step 6 are carried out simultaneously.
3. The method of input current harmonic suppression for a UPS having a PWM rectifier of claim 1, wherein: the given amount of the voltage control loop is the preset threshold UBus_ref。
4. The method of input current harmonic suppression for a UPS having a PWM rectifier of claim 1, wherein: the voltage control loop, the first current control loop and the second current control loop are all PI control loops.
5. The method of input current harmonic suppression for a UPS having a PWM rectifier of claim 1, wherein: the PWM modulator is an SPWM modulator or an SVPWM modulator.
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| US20060091845A1 (en) * | 2004-06-16 | 2006-05-04 | Universita' Degli Studi Di Catania | Control system and method for electric drives with a.c. motors |
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