CN113179035A - Non-isolated converter capable of eliminating leakage current and common mode voltage and control method - Google Patents

Non-isolated converter capable of eliminating leakage current and common mode voltage and control method Download PDF

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CN113179035A
CN113179035A CN202110519233.2A CN202110519233A CN113179035A CN 113179035 A CN113179035 A CN 113179035A CN 202110519233 A CN202110519233 A CN 202110519233A CN 113179035 A CN113179035 A CN 113179035A
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current
phase
axis
control method
voltage
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王磊
韩肖清
崔旋
张佰富
任宇
张馨方
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Taiyuan University of Technology
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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
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac 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
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac 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
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/157—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators with digital control
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac 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
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac 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
    • H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators
    • H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac 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 with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
    • 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
    • H02M7/2173—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 biphase or polyphase circuit arrangement

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Abstract

The invention belongs to the technical field of alternating current and direct current hybrid power distribution networks, relates to a non-isolated converter, in particular to a non-isolated converter capable of eliminating leakage current and common mode voltage and a control method, and solves the technical problem in the background technology. A non-isolated converter capable of eliminating leakage current and common mode voltage comprises a three-phase alternating current power grid, an LCL filter, a three-phase rectifier and a DC/DC converter. A control method capable of eliminating leakage current and common mode voltage comprises a method for controlling a three-phase rectifier by adopting a voltage outer ring and a current inner ring and a method for controlling a fourth bridge arm in a DC/DC converter by adopting an independent bridge arm based on inductive current feedback. The invention overcomes the contradiction that the common mode voltage and the leakage current of the three-phase converter can not be simultaneously inhibited, realizes the common mode decoupling of the AC side and the DC side of the power grid, can inhibit the neutral current, reduce the harmonic wave of the AC current, ensure the flexible grounding application of the converter in the AC/DC power grid and provide high-quality electric energy for the DC load.

Description

Non-isolated converter capable of eliminating leakage current and common mode voltage and control method
Technical Field
The invention belongs to the technical field of alternating current and direct current hybrid power distribution networks, and relates to a non-isolated converter, in particular to a non-isolated converter capable of eliminating leakage current and common mode voltage and a control method.
Background
Distributed new energy represented by photovoltaic power generation and wind power generation is connected into a power grid, energy storage, electric vehicles and numerous household appliances based on direct current power supply are popularized and applied to industrial frequency conversion technology, low-voltage direct current power distribution embodies the advantages of relative simplicity and high efficiency, and an alternating current-direct current hybrid power distribution network becomes an efficient and feasible scheme for a regional power distribution system. The bidirectional AC/DC converter is used as a core device, and the performance of the bidirectional AC/DC converter plays an important role in normal operation of a power distribution system and guaranteeing the quality of electric energy. Safe operation to ground becomes a factor that must be considered when using transformerless non-isolated converters to reduce cost and size.
When high-resistance grounding is adopted, the common-mode voltage is very large, and the leakage current is very small; when directly grounded, the common mode voltage is small and the leakage current is large. Therefore, the selection of the grounding method cannot eliminate the common mode voltage and the leakage current at the same time.
Patent 201610637511.3, "power conversion system and common mode voltage suppression method", proposes to improve the circuit topology, and to isolate the ac side and the dc side of the converter in the zero vector state of the converter switch by adding extra switches, and to reduce the common mode voltage amplitude, thereby reducing the common mode voltage and the leakage current; patent 202010983015.X "a PDM-based direct current microgrid common mode voltage suppression method" proposes to avoid the occurrence of system common mode voltage surge caused by the superposition of the maximum common mode voltage of each converter in a direct current microgrid system to cause abnormal operation of equipment and even damage by improving a modulation mode under the precondition that the output voltage is satisfied. Patent CN201610043958.8 "three-phase common mode filter circuit and filter", patent 200880016950.6 "common mode filter system and method for solar inverter" can eliminate high frequency components in the common mode circuit by introducing common mode filtering.
The three common-mode voltage suppression methods can only reduce the fluctuation amplitude of the common-mode voltage or keep the common-mode voltage constant, but cannot simultaneously eliminate the common-mode voltage and the leakage current.
Disclosure of Invention
The invention aims to solve the technical problem that the common-mode voltage and the leakage current of a three-phase converter can not be simultaneously inhibited, and provides a non-isolated converter capable of eliminating the leakage current and the common-mode voltage and a control method thereof, so that common-mode decoupling of an alternating current side and a direct current side of a power grid is realized, flexible grounding application of the converter in an alternating current and direct current power grid is ensured, and high-quality electric energy is provided for a direct current load.
The technical means adopted for solving the technical problems is to provide a non-isolated converter capable of eliminating leakage current and common mode voltage, which comprises a three-phase alternating current power grid, an LCL filter, a three-phase rectifier and a DC/DC converter, wherein the three-phase rectifier comprises a first bridge arm, a second bridge arm and a third bridge arm which are connected in parallel, and the first bridge arm comprises a first switching tube S connected in seriesapAnd a second switching tube SanThe second bridge arm comprises a third switching tube S connected in seriesbpAnd a fourth switching tube SbnThe third bridge arm comprises a fifth switching tube S connected in seriescpAnd a sixth switching tube Scn(ii) a The DC/DC converter includes an inductor LNAnd a fourth bridge arm and a split capacitor which are connected in parallel, wherein the fourth bridge arm comprises a seventh switching tube S connected in seriesnpAnd an eighth switching tube SnnThe split capacitor comprises a first capacitor C connected in series1And a second capacitor C2Inductance LNIs connected to a seventh switching tube SnpAnd an eighth switching tube SnnBetween, inductance LNIs connected to the first capacitor C1And a second capacitor C2To (c) to (d); the first terminal of the three-phase alternating current network is connected to the first switch tube S after being filtered by the LCL filterapAnd a second switching tube SanThe second terminal is connected to the third switch tube SbpAnd a fourth switching tube SbnThe third terminal is connected to the fifth switch tube ScpAnd a sixth switching tube ScnThree-phase rectifier is connected with DC/DC converter in parallel, and common end of three-phase AC network is connected with inductor LNThe second end of the split capacitor is connected with the ground, and the two ends of the split capacitor are used as connecting ends for connecting the direct current load. In this configuration, the LCL filter is also grounded. Common end and inductor L of three-phase alternating current network in non-isolated converterNThe second ends of the split capacitors are connected with the ground, so that a common ground topology is realized, and the two ends of the split capacitors and the first capacitor C are connected with each other during operation1Or the second capacitor C2The two ends of the direct current output circuit can be selectively connected with a direct current load to realize bipolar output.
The invention also provides a control method capable of eliminating the leakage current and the common-mode voltage, which is realized based on the non-isolated converter capable of eliminating the leakage current and the common-mode voltage;
the three-phase rectifier of the non-isolated converter adopts a voltage outer ring and current inner ring control method, and the voltage outer ring and current inner ring control method comprises the following steps: after passing through LCL filter, the three-phase AC network outputs AC power supply with specific frequency, and the three-phase voltage v of the AC power supply under static coordinate systema、vb、vcObtaining three-phase voltage v of alternating current power supply through phase-locked loopa、vb、vcThe phase θ of (d); according to the phase theta, the three-phase current i of the alternating current power supply under the static coordinate systema、ib、icCoordinate conversion is carried out to respectively obtain d-axis current i under a rotating coordinate systemdQ-axis current iqAnd zero axis current i0(ii) a The AC power supply is rectified by the three-phase rectifier to become the DC power supply, and the DC voltage U of the DC power supplydcAnd a DC reference voltage
Figure BDA0003063226920000021
The difference is regulated by PI to obtain d-axis reference current, which is compared with d-axis current id to generate d-axis error current id_errAll are the same asQ-axis current iqAnd zero axis current i0The q-axis reference current and the zero-axis reference current can be obtained after selective adjustment according to actual requirements, and then the q-axis error current i is obtainedq_errAnd zero axis error current i0_errFor d-axis error current id_errQ-axis error current iq_errAnd zero axis error current i0_errRespectively carrying out PI regulation to generate d-axis reference voltage V under a rotating coordinate systemdQ-axis reference voltage VqAnd a zero-axis reference voltage V0Converting the d-axis reference voltage V in the rotating coordinate system according to the phase thetadQ-axis reference voltage VqAnd a zero-axis reference voltage V0Coordinate conversion is carried out to obtain three-phase reference voltage V under a static coordinate systema、VbAnd VcFinally Va、VbAnd VcThe pulse width modulation is carried out through a first PWM generator, and pulse modulation signals generated by the first PWM generator are used for driving corresponding first switching tubes S in the three-phase rectifierapA second switch tube SanA third switch tube SbpAnd a fourth switching tube SbnThe fifth switch tube ScpAnd a sixth switching tube ScnAn action;
the fourth bridge arm in the DC/DC converter is controlled by adopting an independent bridge arm control method based on inductive current feedback, and the control method based on inductive current feedback comprises the following steps: for the second capacitor C2Sampling voltages at two ends, wherein the sampled voltages pass through a voltage sampling transfer function HvAfter treatment, the mixture is mixed with VrefPerforming difference, and performing PI or PR adjustment on the obtained result to obtain a first reference signal; inductance L for DC/DC converterNSampling current to obtain inductor LNCurrent through current sampling transfer function HiAfter being processed, the signal is compared with the first reference signal in a difference mode, the obtained signal is subjected to pulse width modulation through a second PWM generator, and a pulse modulation signal Q generated by the second PWM generator1NAnd Q2NRespectively controlling a seventh switch tube SnpAnd an eighth switching tube SnnAnd (6) acting.
Preferably, in the control method based on the inductor current feedback, the sampling is carried outTo inductance LNThe current is processed by a current sampling transfer function and then is subjected to difference comparison with a first reference signal, and the obtained signal is firstly subjected to a delay link in sequence
Figure BDA0003063226920000022
And the zero-order keeping link ZOH is sent to the second PWM generator. Delay element
Figure BDA0003063226920000031
The zero-order holding link ZOH is used for keeping the signal for a certain time and ensuring that a subsequent link can receive the signal.
Preferably, in the method for controlling the voltage outer loop and the current inner loop of the three-phase rectifier, the three-phase current i of the alternating current power supply in the static coordinate system is determined according to the phase thetaa、ib、icConverted into d-axis current i under a rotating coordinate systemdQ-axis current iqAnd zero axis current i0The calculation formula of (2) is as follows:
Figure BDA0003063226920000032
preferably, in the method for controlling the voltage outer loop and the current inner loop of the three-phase rectifier, the d-axis reference voltage V in the rotating coordinate system is set according to the phase θdQ-axis reference voltage VqAnd a zero-axis reference voltage V0Converting into three-phase reference voltage V under a static coordinate systema、VbAnd VcThe calculation formula of (2) is as follows:
Figure BDA0003063226920000033
preferably, the q-axis reference current and the zero-axis reference current are both set to zero. And the q-axis reference current and the zero-axis reference current are adjusted according to actual needs.
The invention has the beneficial effects that: the non-isolated converter and the control method can simultaneously eliminate leakage current and common mode voltage, overcome the problems of the size and the over-high cost of an isolated converter transformer, overcome the contradiction that the common mode voltage and the leakage current of a three-phase converter can not be simultaneously inhibited, realize the common mode decoupling of an alternating current side and a direct current side of a power grid, inhibit neutral current, reduce alternating current measurement current harmonic waves, ensure the flexible grounding application of the converter in an alternating current and direct current power grid, provide high-quality electric energy for direct current load, avoid the problems of the reduction of the efficiency and the increase of the size of the introduced isolated transformer, improve the operation performance of the converter and improve the safety performance of equipment.
Drawings
Fig. 1 is a schematic diagram of a non-isolated converter capable of eliminating leakage current and common mode voltage according to the present invention.
Fig. 2 is a control block diagram of a voltage outer loop and a current inner loop control method adopted by the three-phase rectifier of the invention.
Fig. 3 is a control block diagram of an independent bridge arm control method based on inductive current feedback, which is adopted by the fourth bridge arm of the present invention.
Detailed Description
Referring to fig. 1, 2 and 3, a non-isolated converter and a control method for eliminating leakage current and common mode voltage according to the present invention will be described in detail.
A non-isolated converter capable of eliminating leakage current and common mode voltage comprises a three-phase alternating current power grid, an LCL filter, a three-phase rectifier and a DC/DC converter, wherein the three-phase rectifier comprises a first bridge arm, a second bridge arm and a third bridge arm which are connected in parallel, the first bridge arm comprises a first switching tube S connected in seriesapAnd a second switching tube SanThe second bridge arm comprises a third switching tube S connected in seriesbpAnd a fourth switching tube SbnThe third bridge arm comprises a fifth switching tube S connected in seriescpAnd a sixth switching tube Scn(ii) a The DC/DC converter includes an inductor LNAnd a fourth bridge arm and a split capacitor which are connected in parallel, wherein the fourth bridge arm comprises a seventh switching tube S connected in seriesnpAnd an eighth switching tube SnnThe split capacitor comprises a first capacitor C connected in series1And a second capacitor C2Inductance LNIs connected to a seventh switching tube SnpAnd an eighth switching tube SnnBetween, inductance LNIs connected to the second end ofA capacitor C1And a second capacitor C2To (c) to (d); the first terminal of the three-phase alternating current network is connected to the first switch tube S after being filtered by the LCL filterapAnd a second switching tube SanThe second terminal is connected to the third switch tube SbpAnd a fourth switching tube SbnThe third terminal is connected to the fifth switch tube ScpAnd a sixth switching tube ScnThree-phase rectifier is connected with DC/DC converter in parallel, and common end of three-phase AC network is connected with inductor LNThe second end of the split capacitor is connected with the ground, and the two ends of the split capacitor are used as connecting ends for connecting the direct current load. In this configuration, the LCL filter includes a first filter inductor LDM1A second filter inductor LDM2And a filter capacitor CDMWherein the filter capacitor CDMGrounding is also required. Common end and inductor L of three-phase alternating current network in non-isolated converterNThe second ends of the split capacitors are connected with the ground, so that a common ground topology is realized, and the two ends of the split capacitors and the first capacitor C are connected with each other during operation1Or the second capacitor C2The two ends of the direct current output circuit can be selectively connected with a direct current load to realize bipolar output.
The invention also provides a control method capable of eliminating the leakage current and the common-mode voltage, which is realized based on the non-isolated converter capable of eliminating the leakage current and the common-mode voltage;
the three-phase rectifier of the non-isolated converter adopts a voltage outer ring and current inner ring control method, as shown in fig. 2, the voltage outer ring and current inner ring control method is as follows: after passing through LCL filter, the three-phase AC network outputs AC power supply with specific frequency, and the three-phase voltage v of the AC power supply under static coordinate systema、vb、vcObtaining three-phase voltage v of alternating current power supply through phase-locked loopa、vb、vcThe phase θ of (d); according to the phase theta, the three-phase current i of the alternating current power supply under the static coordinate systema、ib、icCoordinate conversion is carried out to respectively obtain d-axis current i under a rotating coordinate systemdQ-axis current iqAnd zero axis current i0(ii) a The alternating current power supply is rectified by the three-phase rectifier to become a direct current power supply,DC voltage U of DC power supplydcAnd a DC reference voltage
Figure BDA0003063226920000041
The difference is regulated by PI to obtain d-axis reference current, d-axis reference current and d-axis current idComparison produces d-axis error current id_errFor q-axis current iqAnd zero axis current i0The q-axis reference current and the zero-axis reference current can be obtained after selective adjustment according to actual requirements, and then the q-axis error current i is obtainedq_errAnd zero axis error current i0_errFor d-axis error current id_errQ-axis error current iq_errAnd zero axis error current i0_errRespectively carrying out PI regulation to generate d-axis reference voltage V under a rotating coordinate systemdQ-axis reference voltage VqAnd a zero-axis reference voltage V0Converting the d-axis reference voltage V in the rotating coordinate system according to the phase thetadQ-axis reference voltage VqAnd a zero-axis reference voltage V0Coordinate conversion is carried out to obtain three-phase reference voltage V under a static coordinate systema、VbAnd VcFinally Va、VbAnd VcThe pulse width modulation is carried out through a first PWM generator, and pulse modulation signals generated by the first PWM generator are used for driving corresponding first switching tubes S in the three-phase rectifierapA second switch tube SanA third switch tube SbpAnd a fourth switching tube SbnThe fifth switch tube ScpAnd a sixth switching tube ScnAn action;
the fourth bridge arm in the DC/DC converter is controlled by using an independent bridge arm control method based on inductive current feedback, as shown in fig. 3, the control method based on inductive current feedback is as follows: for the second capacitor C2Sampling voltages at two ends, wherein the sampled voltages pass through a voltage sampling transfer function HvAfter treatment, the mixture is mixed with VrefPerforming difference, and performing PI or PR adjustment on the obtained result to obtain a first reference signal; inductance L for DC/DC converterNSampling current to obtain inductor LNCurrent through current sampling transfer function HiMixing with the first ginseng after treatmentComparing the difference of the reference signals to obtain a signal, performing pulse width modulation on the signal by a second PWM generator, and generating a pulse modulation signal Q by the second PWM generator1NAnd Q2NRespectively controlling a seventh switch tube SnpAnd an eighth switching tube SnnAnd (6) acting. In FIG. 3, Gv(z) is the transfer function for PI or PR adjustment.
Further, as a specific embodiment of the control method for eliminating the leakage current and the common mode voltage according to the present invention, in the control method based on the inductor current feedback, the inductor L obtained by sampling is usedNThe current is processed by a current sampling transfer function and then is subjected to difference comparison with a first reference signal, and the obtained signal is firstly subjected to a delay link in sequence
Figure BDA0003063226920000051
And the zero-order keeping link ZOH is sent to the second PWM generator. Delay element
Figure BDA0003063226920000052
The zero-order holding link ZOH is used for keeping the signal for a certain time and ensuring that a subsequent link can receive the signal.
Further, as a specific embodiment of the control method for eliminating the leakage current and the common mode voltage according to the present invention, in the control method for the voltage outer loop and the current inner loop of the three-phase rectifier, the three-phase current i of the ac power supply in the stationary coordinate system is adjusted according to the phase θa、ib、icConverted into d-axis current i under a rotating coordinate systemdQ-axis current iqAnd zero axis current i0The calculation formula of (2) is as follows:
Figure BDA0003063226920000053
further, as a specific embodiment of the control method for eliminating the leakage current and the common mode voltage according to the present invention, in the control method for the voltage outer loop and the current inner loop of the three-phase rectifier, the d-axis reference voltage V in the rotating coordinate system is set according to the phase θdQ axisReference voltage VqAnd a zero-axis reference voltage V0Converting into three-phase reference voltage V under a static coordinate systema、VbAnd VcThe calculation formula of (2) is as follows:
Figure BDA0003063226920000054
further, as a specific embodiment of the control method for eliminating the leakage current and the common mode voltage according to the present invention, the q-axis reference current and the zero-axis reference current are both set to be zero. And the q-axis reference current and the zero-axis reference current are adjusted according to actual needs.
While the preferred embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (6)

1. The non-isolated converter capable of eliminating leakage current and common-mode voltage is characterized by comprising a three-phase alternating-current power grid, an LCL filter, a three-phase rectifier and a DC/DC converter, wherein the three-phase rectifier comprises a first bridge arm, a second bridge arm and a third bridge arm which are connected in parallel, and the first bridge arm comprises a first switching tube S connected in seriesapAnd a second switching tube SanThe second bridge arm comprises a third switching tube S connected in seriesbpAnd a fourth switching tube SbnThe third bridge arm comprises a fifth switching tube S connected in seriescpAnd a sixth switching tube Scn(ii) a The DC/DC converter includes an inductor LNAnd a fourth bridge arm and a split capacitor which are connected in parallel, wherein the fourth bridge arm comprises a seventh switching tube S connected in seriesnpAnd an eighth switching tube SnnThe split capacitor comprises a first capacitor C connected in series1And a second capacitor C2Inductance LNIs connected to a seventh switching tube SnpAnd an eighth switching tube SnnBetween, inductance LNIs connected to the first capacitor C1And a second capacitor C2To (c) to (d); the first terminal of the three-phase alternating current network is connected to the first switch tube S after being filtered by the LCL filterapAnd a second switching tube SanThe second terminal is connected to the third switch tube SbpAnd a fourth switching tube SbnThe third terminal is connected to the fifth switch tube ScpAnd a sixth switching tube ScnThree-phase rectifier is connected with DC/DC converter in parallel, and common end of three-phase AC network is connected with inductor LNThe second end of the split capacitor is connected with the ground, and the two ends of the split capacitor are used as connecting ends for connecting the direct current load.
2. A control method capable of eliminating leakage current and common mode voltage, which is implemented based on the non-isolated converter capable of eliminating leakage current and common mode voltage of claim 1;
the three-phase rectifier of the non-isolated converter adopts a voltage outer ring and current inner ring control method, and the voltage outer ring and current inner ring control method comprises the following steps: after passing through LCL filter, the three-phase AC network outputs AC power supply with specific frequency, and the three-phase voltage v of the AC power supply under static coordinate systema、vb、vcObtaining three-phase voltage v of alternating current power supply through phase-locked loopa、vb、vcThe phase θ of (d); according to the phase theta, the three-phase current i of the alternating current power supply under the static coordinate systema、ib、icCoordinate conversion is carried out to respectively obtain d-axis current i under a rotating coordinate systemdQ-axis current iqAnd zero axis current i0(ii) a The AC power supply is rectified by the three-phase rectifier to become DC, and the DC voltage U of the DCdcAnd a DC reference voltage
Figure FDA0003063226910000011
The difference is regulated by PI to obtain d-axis reference current, d-axis reference current and d-axis current idComparison produces d-axis error current id_errFor q-axis current iqAnd zero axis current i0The q-axis reference current and the zero-axis reference current can be obtained after selective adjustment according to actual requirements, and then the q-axis error current is obtainediq_errAnd zero axis error current i0_errFor d-axis error current id_errQ-axis error current iq_errAnd zero axis error current i0_errRespectively carrying out PI regulation to generate d-axis reference voltage V under a rotating coordinate systemdQ-axis reference voltage VqAnd a zero-axis reference voltage V0Converting the d-axis reference voltage V in the rotating coordinate system according to the phase thetadQ-axis reference voltage VqAnd a zero-axis reference voltage V0Coordinate conversion is carried out to obtain three-phase reference voltage V under a static coordinate systema、VbAnd VcFinally Va、VbAnd VcThe pulse width modulation is carried out through a first PWM generator, and pulse modulation signals generated by the first PWM generator are used for driving corresponding first switching tubes S in the three-phase rectifierapA second switch tube SanA third switch tube SbpAnd a fourth switching tube SbnThe fifth switch tube ScpAnd a sixth switching tube ScnAn action;
the fourth bridge arm in the DC/DC converter is controlled by adopting an independent bridge arm control method based on inductive current feedback, and the control method based on inductive current feedback comprises the following steps: for the second capacitor C2Sampling voltages at two ends, wherein the sampled voltages pass through a voltage sampling transfer function HvAfter treatment, the mixture is mixed with VrefPerforming difference, and performing PI or PR adjustment on the obtained result to obtain a first reference signal; inductance L for DC/DC converterNSampling current to obtain inductor LNCurrent through current sampling transfer function HiAfter being processed, the signal is compared with the first reference signal in a difference mode, the obtained signal is subjected to pulse width modulation through a second PWM generator, and a pulse modulation signal Q generated by the second PWM generator1NAnd Q2NRespectively controlling a seventh switch tube SnpAnd an eighth switching tube SnnAnd (6) acting.
3. The control method as claimed in claim 2, wherein the inductor L is sampled in the control method based on inductor current feedbackNCurrent flows throughThe overcurrent sampling transfer function is processed and then is subjected to difference comparison with a first reference signal, and the obtained signal is firstly subjected to a delay link in sequence
Figure FDA0003063226910000021
And the zero-order keeping link ZOH is sent to the second PWM generator.
4. The control method according to claim 2 or 3, wherein in the control method for the voltage outer loop and the current inner loop of the three-phase rectifier, the three-phase current i of the AC power supply in the stationary coordinate system is adjusted according to the phase θa、ib、icConverted into d-axis current i under a rotating coordinate systemdQ-axis current iqAnd zero axis current i0The calculation formula of (2) is as follows:
Figure FDA0003063226910000031
5. the control method as claimed in claim 4, wherein the d-axis reference voltage V in the rotating coordinate system is determined according to the phase θ in the control method for the voltage outer loop and the current inner loop of the three-phase rectifierdQ-axis reference voltage VqAnd a zero-axis reference voltage V0Converting into three-phase reference voltage V under a static coordinate systema、VbAnd VcThe calculation formula of (2) is as follows:
Figure FDA0003063226910000032
6. the control method of claim 5, wherein the q-axis reference current and the zero-axis reference current are set to zero.
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