CN109639160B - Novel unidirectional three-phase three-level rectifier based on soft switching technology - Google Patents

Novel unidirectional three-phase three-level rectifier based on soft switching technology Download PDF

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CN109639160B
CN109639160B CN201811482810.XA CN201811482810A CN109639160B CN 109639160 B CN109639160 B CN 109639160B CN 201811482810 A CN201811482810 A CN 201811482810A CN 109639160 B CN109639160 B CN 109639160B
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power switch
switch tube
capacitor
voltage
parallel
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CN109639160A (en
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马辉
韩笑
田鹏辉
田宇
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Wuhan Xinyuan Automatic Control Engineering Co.,Ltd.
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China Three Gorges University CTGU
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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
    • H02M7/2173—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
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • H02M1/4208—Arrangements for improving power factor of AC input
    • H02M1/4233—Arrangements for improving power factor of AC input using a bridge converter comprising active switches
    • 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
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • H02M1/4208—Arrangements for improving power factor of AC input
    • H02M1/4241—Arrangements for improving power factor of AC input using a resonant converter
    • 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
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0012—Control circuits using digital or numerical techniques
    • 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
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • H02M1/0058—Transistor switching losses by employing soft switching techniques, i.e. commutation of transistors when applied voltage is zero or when current flow is zero
    • 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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  • Power Engineering (AREA)
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Abstract

A novel unidirectional three-phase three-level rectifier based on a soft switching technology comprises a unidirectional three-level rectification circuit, a resonance circuit, a buffer circuit, a voltage sampling circuit, a current sampling circuit, a zero-crossing comparison circuit, a DSP control module and a PWM driving circuit. The unidirectional three-phase three-current smoothing circuit is formed by 6 power switching tubes to form three rectifier bridge arms, so that the number of elements is effectively reduced, the structure is simplified, and the cost is reduced. The resonant circuit comprises a resonant inductor, a clamping capacitor, an auxiliary switch and the like, and can enable the main switch to realize zero-voltage switching-on, thereby effectively reducing the switching loss and the switching noise. The buffer circuit consists of 6 capacitors connected with the main switch in parallel, so that the turn-off process of the main switch is softer. By adopting the structure, a double closed-loop control mode is utilized, and the PI control and SVPWM combined control method is adopted for the current inner ring and the voltage outer ring, so that harmonic waves are effectively inhibited, and the current sine at the alternating current side, the stable output of voltage and the unit power factor control at the network side are realized.

Description

Novel unidirectional three-phase three-level rectifier based on soft switching technology
Technical Field
The invention relates to the technical field of three-phase rectifiers, in particular to a novel unidirectional three-phase three-level rectifier based on a soft switching technology.
Background
With the rapid development of power electronic technology, power electronic equipment, such as various high-quality application-type power supplies, electric traction locomotives and other electric railway equipment, variable-frequency speed control systems, various new energy power generation and the like, is increasing in daily life and work production. As an important technology for improving system performance and improving system working efficiency, the multilevel conversion technology is gaining more and more favor from academic and industrial circles in high-power fields such as new energy inverter grid connection, distributed direct current power generation, transmission systems and the like. Due to the increasingly strong requirements of the characteristics of high voltage resistance, high frequency, high voltage, large capacity and the like of the power electronic device, the traditional two-level converter has a plurality of bottlenecks which are difficult to break through in the application of a high-power occasion. Although the main circuit structure of the three-level rectifier is relatively complicated compared to the conventional two-level rectifier, the three-level rectifier is receiving more and more attention due to its advantages in terms of harmonic suppression, power factor improvement, voltage stress reduction, and the like.
In addition, with the rapid development of power electronic technology, the technology of the switching power supply is continuously advanced and innovated, but with the development trend of light weight, high frequency and high voltage power of the switching power supply, a series of problems such as on-off loss and switching noise caused by the increase of the switching frequency are not negligible. In order to solve the problems, a soft switching technology is proposed, namely, a resonance link is introduced before and after the switching process, so that the voltage of a switching tube is reduced to zero before the switching tube is switched on, and the current value is reduced to zero before the switching tube is switched off. Thus, the overlapping of voltage and current is eliminated in the process of switching on and off the device, and the switching loss is greatly reduced. Meanwhile, the introduced resonance link limits the change rate of voltage and current in the switching process, so that the switching noise is obviously reduced, and the soft switching technology ensures the further improvement of the working frequency.
Disclosure of Invention
The invention aims to provide a novel unidirectional three-phase three-level rectifier based on a soft switching technology, which effectively solves the switching loss and switching noise caused by the traditional hard switch, reduces the number of elements, simplifies the structure and reduces the cost.
The technical scheme adopted by the invention is as follows:
the novel unidirectional three-phase three-level rectifier based on the soft switching technology comprises a rectifying circuit, a resonant circuit, a buffer circuit, a sampling circuit, a zero-crossing detection circuit, a DSP control module and a PWM driving circuit;
the rectifying loop consists of 3 rectifying bridge arms, and each rectifying bridge arm consists of 2 power switching tubes Sx1、Sx22 clamping diodes respectively connected with the power switch tube in parallel and 2 fast recovery diodes Dx1、Dx2Composition is carried out;
rectifier bridge arm 1: Sa1Collector and its anti-parallel diode cathode, fast recovery diode Da1The anode is connected with one end of the buffer capacitor; sa2Collector and anti-parallel diode thereofCathode, fast recovery diode Da1The anode is connected with one end of the buffer capacitor; sa1Emitter and anti-parallel diode anode thereof, and fast recovery diode Da2One end of the cathode is connected with one end of the buffer capacitor; sa2Emitter, anti-parallel diode anode thereof, one end of buffer capacitor and resonant inductor LrOne end is connected.
Rectifier bridge arm 2: Sb1Collector and its anti-parallel diode cathode, fast recovery diode Db1The anode is connected with one end of the buffer capacitor; sb2Collector and its anti-parallel diode cathode, fast recovery diode Db1The anode is connected with one end of the buffer capacitor; sb1Emitter and anti-parallel diode anode thereof, and fast recovery diode Db2One end of the cathode is connected with one end of the buffer capacitor; sb2Emitter, anti-parallel diode anode thereof, one end of buffer capacitor and resonant inductor LrOne end is connected.
Rectifier bridge arm 3: Sc1Collector and its anti-parallel diode cathode, fast recovery diode Dc1The anode is connected with one end of the buffer capacitor; sc2Collector and its anti-parallel diode cathode, fast recovery diode Db1The anode is connected with one end of the buffer capacitor; sc1Emitter and anti-parallel diode anode thereof, and fast recovery diode Db2One end of the cathode is connected with one end of the buffer capacitor; sc2Emitter, anti-parallel diode anode thereof, one end of buffer capacitor and resonant inductor LrOne end is connected.
The resonant circuit is composed of a resonant inductor LrAuxiliary switch S3Parallel capacitor C3And a clamp capacitor CcAnd (4) forming. S3Collector and resonant inductor LrOne end, reverse parallel diode anode and parallel capacitor C3One end is connected; s3Emitter, reverse parallel diode cathode and parallel capacitor C3The other end and a clamping capacitor CcOne end is connected. Capacitor CcThe other end and a resonant inductor LrThe other end is connected with the middle position point n. By adopting the structure, the starting moment of circuit resonance is controlled by introducing the auxiliary switch, so that the resonance inductance is harmoniousThe vibration capacitor only generates resonance before the main switch is switched on, so that resonance current is generated to charge and discharge the parallel capacitor, and a zero voltage switching-on condition is created for the main switch.
The buffer loop is composed of 6 power devices and a capacitor connected with the power devices in parallel. The voltage at the two ends of the switch can not change suddenly after the switch is turned off, the turn-off process is softer, and the switching loss is reduced.
The sampling circuit comprises Hall voltage and current sensors and is used for detecting and sampling voltages and currents on a direct current side and an alternating current side. The sampling circuit adopts a high-precision special sampling chip AD7606 which has a filtering function in a chip. In addition, the LA58-P hall sensor from LEM is used to convert the grid current or the dc link current into a low current. The power grid voltage sampling circuit adopts a TV16E voltage transformer of the company of Yanghua Delchang, and the rated input current is 2.5 mA. The direct current side voltage sampling circuit adopts an LEM LV28 type voltage Hall sensor to measure direct current voltage, the primary-secondary side transformation ratio parameter is 2500:1000, the rated input current is 10mA, the rated voltage range is 500V at most, and 10V at least.
The zero-crossing detection circuit is used for detecting the zero-crossing point moment of the power grid voltage, and capturing the zero-crossing point of the power grid voltage by using the DSP control module to realize phase locking of the power grid frequency.
And the DSP control module is used for acquiring data, realizing a control strategy and controlling a main circuit switching device. The DSP control module may be selected from the C2000 series DSPs of TI corporation, which are designed by TI corporation specifically for real-time control applications. Considering the switching frequency of the PWM rectifier, the requirement of a program on a memory, the operation speed and the fact that the soft switching PWM rectifier has one more direct current resonant circuit and one more auxiliary switching tube than the common PWM rectifier, and finally selecting C2000 series F28335 as a control chip.
And the PWM driving circuit is used for driving the switching tube of the unidirectional three-phase three-level rectifier. The PWM driving circuit adopts an ePWM module of F28335, and 4 ePWM sub-modules are required to be configured in total in consideration of the fact that the invention needs 7 paths of PWM waves and one e PWM sub-module can send out two paths of PWM waves.
The invention discloses a novel unidirectional three-phase three-level rectifier based on a soft switching technology, which has the following beneficial effects:
1. the rectifier only needs 6 main switching tubes, the number of elements is effectively reduced, so that the loss is small, the structure is simplified, the cost is reduced, harmonic waves can be effectively inhibited, and the control of unit power factors on the network side is realized.
2. The invention adopts soft switch technology, adds a resonance loop on the basis of the original rectifier, introduces a resonance link before the switch is conducted, leads the voltage of the switch tube to be reduced to zero before the switch is conducted, and eliminates the overlapping of the voltage and the current in the process of switching on and switching off the device. The switching loss is reduced to be close to zero, and simultaneously, the noise generated in the switching process is reduced, so that the reliability of the switching device is improved.
3. The invention adopts a double closed-loop control mode, and the current inner ring and the voltage outer ring both adopt PI control, thereby having the advantages of inhibiting harmonic waves injected into a power grid, realizing the sine of alternating current side current and unit power factor, improving the current tracking capability, stabilizing the system control and the like.
Drawings
The invention is further illustrated by the following examples in conjunction with the accompanying drawings:
FIG. 1 is a main topology structure diagram of a novel unidirectional three-phase three-level rectifier based on soft switching technology;
FIG. 2 is a timing diagram of the switching of a novel unidirectional three-phase three-level rectifier based on soft switching technology according to the present invention;
FIG. 3 shows a first operating state of a novel unidirectional three-phase three-level rectifier according to the present invention based on soft switching technology;
FIG. 4 shows a second operating state of the novel unidirectional three-phase three-level rectifier according to the present invention based on soft switching technology;
FIG. 5 shows a third operating state of the novel unidirectional three-phase three-level rectifier according to the present invention based on soft switching technology;
FIG. 6 shows a novel unidirectional three-phase three-level rectifier operating state IV based on soft switching technology
FIG. 7 shows a fifth operating state of the novel unidirectional three-phase three-level rectifier according to the present invention based on soft switching technology;
FIG. 8 is a control block diagram of a novel unidirectional three-phase three-level rectifier based on soft switching technology according to the present invention;
FIG. 9 is a voltage waveform diagram of the input side current of the novel unidirectional three-phase three-level rectifier based on the soft switching technology;
FIG. 10 shows a novel main switch S of a unidirectional three-phase three-level rectifier according to the present invention based on soft switching technologyc2U in the process of current conversionCEAnd UGEA waveform diagram;
FIG. 11 shows a novel main switch S of a unidirectional three-phase three-level rectifier according to the present invention based on soft switching technologyc2U in the process of current conversionCEAnd UGEAnd amplifying the waveform.
Detailed Description
FIG. 1 shows a main topology of a novel unidirectional three-phase three-level rectifier based on soft switching technology, Va(t)、Vb(t)、Vc(t) three-phase network voltages, ia、ib、icFor the input current at the network side, L is the filter inductance at the network side, L is equal in size, C is the filter inductance at the three-phase1、C2Is a DC side upper and lower capacitor, Sa1、Sa2、Sb1、Sb2、Sc1、Sc26 IGBT switching tubes for forming the rectifier bridge, Da1、Da2、Db1、Db2、Dc1、Dc26 fast recovery diodes forming the rectifier bridge.
The novel unidirectional three-phase three-level rectifier based on the soft switching technology has three rectification states: state 1 is through switch SX1And a diode DX1Obtained by the conduction of (a); state 2 is when switch SX1And SX2Obtained when conducting simultaneously; state 3 is by switch SX2And a diode DX2Is obtained by the conduction of (a). According to the position in the circuit, 6 main switching tubes in the circuit can be divided into 3 pairs: sa、Sb、Sc. Each bridge arm has 3 effective switch states(1, 0, -1), and satisfy
Figure BDA0001893791680000041
The neutral point n is kept in dynamic voltage balance, an
Figure BDA0001893791680000042
UanRespectively have 3 levels
Figure BDA0001893791680000043
UabThere are five levels
Figure BDA0001893791680000044
The rectifier has 27 working states, and the implementation of the soft switch is described by taking three working modes (011), (010) and (110) as examples, as shown in fig. 3-7:
stage one (t)0-t1): the working vector corresponding to the rectifier at the stage is (011), and the main switch Sa1、Sa2、Sb1、Sc1And an auxiliary switch S3Conduction, current iaVia a main switch Sa1、Sa2Reach the neutral point n, current ibFlows through the main switch Sb1And a diode Db1Then reaches n point, current icVia a main switch Sc1And a diode Dc1And reaches the point n. At this time
Figure BDA0001893791680000051
Stage two (t)1-t2)：t1Time of day, auxiliary switch S3Turn-off, resonant inductance LrAnd a main switch Sc2The parallel capacitor also has an auxiliary switch S3Parallel capacitor C3Carry out resonance, LrTo main switch Sc2Discharging the parallel capacitor of C3And charging is carried out. To t2At the moment, the main switch Sc2The voltage drop across the parallel capacitor is zero, the resonance stops, and S is turned onc2Then switch Sc2Is turned on at zero voltage.
Stage three (t)2-t3): the working vector corresponding to the rectifier at the stage is (010), and the main switch Sa1、Sa2、Sb1、Sc1And Sc2On, current iaVia a main switch Sa1、Sa2Reach the neutral point n, current ibFlows through the main switch Sb1And a diode Db1Then reaches n point, current icVia a main switch Sc1、Sc2Reaching the mid-position n. At this time
Figure BDA0001893791680000053
Resonant inductor LrAnd a main switch Sb2Parallel capacitor and capacitor C3Carry out resonance, LrTo Sb2Charging parallel capacitors to C3And discharging is performed. To t3Time C3The voltage drop at both ends is zero, the resonance stops, and S is switched on3Then S is3Is turned on under zero voltage conditions.
Stage four (t)3-t4)：t3From time to time, the main switch Sa1、Sa2、Sb1、Sc1、Sc2And an auxiliary switch S3The power-on state is carried out,
by a resonant inductance LrAuxiliary switch S3And a clamp capacitor CcIn a composed resonant circuit LrTo CcAnd (6) charging.
Stage five (t)4-t5): to t4At the moment, the main switch Sa2And (6) turning off. At this time, the working vector corresponding to the rectifier is (110), and the main switch Sa1、Sb1、Sc1、Sc2And the auxiliary switch is turned on S3. Current iaFlows through the main switch Sa1And a diode Da1Then reaches the middle position n; current ibFlows through the main switch Sb1And a diode Db1Then n points are reached; current icVia a main switch Sc1、Sc2Then reaches the point n. At this time
Figure BDA0001893791680000052
The mathematical model of the rectifier is as follows:
Figure BDA0001893791680000061
Van、Vbnvoltages, V, from input points a, b of the rectifier bridge to a point n in the DC sidenoIs the voltage from n point to O point on the direct current side.
FIG. 2 is a timing diagram of the main and auxiliary switches of the rectifier, and the main switch S can be seen from FIG. 2c2Requiring an auxiliary switch S before switching on3Acts to resonate to generate a resonant current to the main switch Sc2Is discharged as Sc2The zero voltage turn-on of (2) creates conditions. Sa2And the turn-off loss of the switching tube is reduced by the buffer action of the capacitors connected in parallel at the two ends of the switching tube during turn-off.
Fig. 8 is a control block diagram of the rectifier, in which a current inner loop and a voltage outer loop are both PI controlled by using a dual closed-loop control method.
The specific parameters of the circuit are as follows:
the effective value of input voltage is 110V, the frequency is 50Hz, the output voltage of the DC side is 350V, the switching frequency is 10kHz, the filter inductance L is 5mH, and the capacitance C of the DC side is1＝C24400 muf, resonant inductor L in the resonant circuit r50 mu H, the switch tube is connected with a capacitor C in parallela1＝Ca2＝Cb1＝Cb2＝Cc1＝Cc233nF, clamp capacitance CcAuxiliary switch parallel capacitor C at 45nF3＝5.04nF。
The specific control process is as follows:
(1) through sampling circuit to the voltage U of the power grida(t)、Ub(t)、Uc(t) AC side Current ia(t)、ib(t)、ic(t) and DC side upper and lower capacitor voltages Udc1、Udc2Sampling is performed.
(2) Measured Udc1、Udc2Adding to obtain DC side voltage UdcWill U isdcWith a given reference value UdcrefAnd comparing to obtain an error, and taking the error as an input value of the voltage outer ring PI regulator, and taking an output value of the voltage outer ring PI regulator as a given value of the current inner ring d axis. Sampled power grid current ia、ib、icD-axis current after dq conversion is decoupled from error thereof, and then power grid voltage feedforward e is addeddFinally, the d-axis component U of the reference voltage vector is obtainedd *. Also like the q-axis, to achieve unity power factor, the given current for the q-axis is therefore 0.
(3) The obtained reference voltage vector Uq *、Ud *Obtaining u through the contra-rotating coordinate transformation from the two-phase rotating coordinate system to the two-phase static coordinate systemrα，urβThen, SVPWM modulation of three levels is carried out, so as to generate a driving signal and control the action of a switching tube.
(4) Measured Udc1、Udc2Subtracting to obtain the potential difference delta U of the upper and lower capacitorsdcControl of Delta U by a simple PI linkdcTherefore, the value of the midpoint potential adjusting factor f is obtained, the action time of distributing positive and negative small redundant vectors is calculated, and the charging and discharging time of upper and lower capacitors is substantially distributed, so that the problem of unbalanced midpoint potential of the three-level rectifier is solved.
Fig. 9 is a waveform diagram of the input side voltage and current of the rectifier, and it can be seen from fig. 9 that the overall current is better sinusoidal, and the voltage and current realize the same phase, and the unity power factor is realized.
FIG. 11 shows the main switch S of the rectifierc2U in the process of current conversionCEAnd UGEThe enlarged waveform is shown in FIG. 11 at Sc2Before conduction, the voltage between the collector and the emitter of the switch is reduced to zero, and soft switching is realized.

Claims (1)

1. The novel unidirectional three-phase three-level rectifier based on the soft switching technology comprises a rectifying circuit, a resonant circuit, a buffer circuit, a sampling circuit, a zero-crossing detection circuit, a DSP control module and a PWM driving circuit; the method is characterized in that:
the rectifying loop consists of 3 rectifying bridge arms, and each rectifying bridge arm consists of 2 power switching tubes, 2 clamping diodes which are respectively connected with the power switching tubes in an anti-parallel mode and 2 fast recovery diodes;
rectifier bridge arm 1: power switch tube Sa1Collector and its anti-parallel clamp diode cathode, fast recovery diode Da1The anode is connected with one end of the first buffer capacitor; power switch tube Sa2Collector and its anti-parallel clamp diode cathode, fast recovery diode Da1The anode is connected with one end of the second buffer capacitor; power switch tube Sa1Emitter and its anti-parallel clamp diode anode, fast recovery diode Da2The cathode is connected with the other end of the first buffer capacitor; power switch tube Sa2Emitter, anode of anti-parallel clamping diode, the other end of second buffer capacitor and resonant inductor LrOne end is connected;
rectifier bridge arm 2 power switch tube Sb1Collector and its anti-parallel clamp diode cathode, fast recovery diode Db1The anode is connected with one end of the third buffer capacitor; power switch tube Sb2Collector and its anti-parallel clamp diode cathode, fast recovery diode Db1The anode is connected with one end of a fourth buffer capacitor; power switch tube Sb1Emitter and its anti-parallel clamp diode anode, fast recovery diode Db2The cathode is connected with the other end of the third buffer capacitor; power switch tube Sb2Emitter, anode of anti-parallel clamping diode of emitter, other end of fourth buffer capacitor and resonant inductor LrOne end is connected;
rectifier bridge arm 3 power switch tube Sc1Collector and its anti-parallel clamp diode cathode, fast recovery diode Dc1The anode is connected with one end of a fifth buffer capacitor; power switch tube Sc2Collector and its anti-parallel clamp diode cathode, fast recovery diode Dc1The anode is connected with one end of the sixth buffer capacitor; power switch tube Sc1Emitter and its anti-parallel clamp diode anode, fast recovery diode Dc2The cathode is connected with the other end of the fifth buffer capacitor; power switch tube Sc2Emitter, anode of anti-parallel clamping diode of emitter, other end of sixth buffer capacitor and resonant inductor LrOne end is connected;
the resonant circuit is composed of a resonant inductor LrAuxiliary switch S3Parallel capacitor C3And a clamp capacitor CcComposition is carried out; auxiliary switch S3Collector and resonant inductor LrOne end, reverse parallel diode anode and parallel capacitor C3One end is connected; auxiliary switch S3Emitter, reverse parallel diode cathode and parallel capacitor C3The other end, a clamping capacitor CcOne end is connected; clamping capacitor CcThe other end and a resonant inductor LrThe other end is connected with a middle position point n;
capacitor C on the DC side1One end is connected with a fast recovery diode Dc1Cathode, capacitor C on the DC side1The other end is connected with a lower capacitor C at the direct current side2One terminal, a DC side down capacitor C2The other end is connected with a fast recovery diode Dc2An anode;
capacitor C on the DC side1The other end and a DC side lower capacitor C2A junction at one end, forming a mid-site n;
the buffer loop is composed of 6 power switch tubes Sa1、Sa2、Sb1、Sb2、Sc1、Sc2And 6 power switch tubes Sa1、Sa2、Sb1、Sb2、Sc1、Sc2The first buffer capacitor, the second buffer capacitor, the third buffer capacitor, the fourth buffer capacitor, the fifth buffer capacitor and the sixth buffer capacitor are respectively connected in parallel;
the sampling circuit comprises a Hall voltage and current sensor and is used for realizing detection and sampling of voltage and current at a direct current side and voltage and current at an alternating current side;
the zero-crossing detection circuit is used for detecting the zero-crossing point moment of the power grid voltage, capturing the zero-crossing point of the power grid voltage by using the DSP control module and realizing the phase locking of the power grid frequency;
the DSP control module is used for collecting data, realizing control strategy and carrying out S on a main circuit power switch tubea1、Sa2、Sb1、Sb2、Sc1、Sc2Controlling;
the PWM driving circuit is used for driving a power switching tube of the unidirectional three-phase three-level rectifier;
the novel unidirectional three-phase three-level rectifier has three rectification states:
state 1 is through the power switch tube SX1And a fast recovery diode DX1Obtaining the conduction of (1);
state 2 is when the power switch tube SX1And a power switch tube SX2Obtained when conducting at the same time;
state 3 is formed by the power switch tube SX2And a fast recovery diode DX2Obtaining the conduction of (1);
wherein the content of the first and second substances,Xrepresents a, b, c; a denotes the phase a of the three-phase network, b denotes the phase b of the three-phase network, c denotes the phase c of the three-phase network,
according to the position in the circuit, 6 power switch tubes S in the circuit can be connecteda1、Sa2、Sb1、Sb2、Sc1、Sc2Is divided into 3 pairs which are respectively Sai、Sbi、SciWhere i denotes 1, 2, each leg has 3 valid switch states (1, 0, -1) and satisfies:
Figure FDA0003077956830000021
wherein f isa、fb、fcRespectively showing the effective switch states of a-phase bridge arm, b-phase bridge arm and c-phase bridge arm;
make the neutral point n keep dynamic voltage balance, and
Figure FDA0003077956830000031
Uanrespectively have 3 levels
Figure FDA0003077956830000032
0、
Figure FDA0003077956830000033
UabThere are five levels
Figure FDA0003077956830000034
-E、0、
Figure FDA0003077956830000035
E，
Udc1Representing the capacitance C on the DC side1Voltage of Udc2Representing the capacitance C under the DC side2E is the total voltage value of the DC side, UabIndicating power switch tube Sa1Emitter and power switch tube Sb1Bridge arm line voltage between the emitters;
the rectifier has 27 working states as shown in the formula (1-1), and the implementation method of the soft switch is described by three working modes of (011), (010) and (110):
stage one (t)0-t1): the working vector corresponding to the rectifier at the stage is (011), and the power switch tube Sa1、Sa2、Sb1、Sc1And an auxiliary switch S3On, net side input current iaVia a power switch tube Sa1、Sa2To the neutral point n, the net side input current ibCurrent through the power switch tube Sb1And fast recovery diode Db1Rear arrival at the midpoint n, net side input current icVia a power switch tube Sc1And fast recovery diode Dc1Reach the mid-position n; at this time
Figure FDA0003077956830000036
UanIndicating power switch tube Sa1Voltage between emitter to mid-point n in the DC side, UbnIndicating power switch tube Sb1Voltage between emitter to mid-point n in the DC side, UcnIndicating power switch tube Sc1Voltage between emitter to a point n in the dc side;
stage two (t)1-t2)：t1Time of day, auxiliary switch S3Turn-off, resonant inductance LrAnd a power switch tube Sc2The sixth buffer capacitor connected in parallel also has an auxiliary switch S3Parallel capacitor C3Performs resonance, resonance inductance LrFor power switch tube Sc2Discharging the parallel sixth buffer capacitor to the parallel capacitor C3Charging is carried out; to t2Time of day, power switch tube Sc2The voltage drop at two ends of the sixth buffer capacitor connected in parallel is zero, the resonance stops, and the power switch tube S is switched on at the momentc2Then power switch tube Sc2Is turned on under zero voltage conditions;
stage three (t)2-t3): the working vector corresponding to the rectifier at the stage is (010), and the power switch tube Sa1、Sa2、Sb1、Sc1And Sc2On, net side input current iaVia a power switch tube Sa1、Sa2To the neutral point n, the net side input current ibCurrent through the power switch tube Sb1And fast recovery diode Db1Rear arrival at the midpoint n, net side input current icVia a power switch tube Sc1、Sc2Reach the mid-position n; at this time Uan＝Ucn＝0,
Figure FDA0003077956830000041
Resonant inductor LrAnd a power switch tube Sb2Parallel fourth buffer capacitor and parallel capacitor C3Performs resonance, resonance inductance LrFor power switch tube Sb2Charging the parallel fourth buffer capacitor to the parallel capacitor C3Discharging; to t3Time parallel capacitor C3The voltage drop at both ends is zero, the resonance stops, and the auxiliary switch S is turned on3Then auxiliary switch S3Is switched on under the condition of zero voltage;
stage four (t)3-t4)：t3From time to time, the power switch tube Sa1、Sa2、Sb1、Sc1、Sc2And an auxiliary switch S3Is conducted through the resonant inductor LrAuxiliary switch S3And a clamp capacitor CcResonant inductor L in formed resonant looprTo a clamping capacitor CcCharging;
stage five (t)4-t5): to t4Time of day, power switch tube Sa2Turning off; at this time, the working vector corresponding to the rectifier is (110), and the power switch tube Sa1、Sb1、Sc1、Sc2And an auxiliary switch S3Conducting; net side input current iaCurrent through the power switch tube Sa1And fast recovery diode Da1Then reaches the middle position n; net side input current ibCurrent through the power switch tube Sb1And fast recovery diode Db1Then reaches the middle position n; net side input current icVia a power switch tube Sc1、Sc2Then reaches the middle position n; at this time
Figure FDA0003077956830000042
Figure FDA0003077956830000043
Ucn＝0；
The novel unidirectional three-phase three-level rectifier utilizes a double closed-loop control mode, a current inner ring and a voltage outer ring both adopt a control method combining PI control and SVPWM, and the specific control process is as follows:
(1): through sampling circuit to the voltage U of the power grida(t)、Ub(t)、Uc(t) AC side Current ia(t)、ib(t)、ic(t) and DC side upper and lower capacitor voltages Udc1、Udc2Sampling is carried out;
(2): measured Udc1、Udc2Adding the voltage values to obtain a total voltage value E at the DC side, and adding the total voltage value E at the DC side to a given reference value UdcrefComparing to obtain error, and using the error as input value of voltage outer ring PI regulatorThe output value of the regulator is used as the given value of the current of the d-axis of the current inner ring; sampled network side input current ia、ib、icD-axis current after dq conversion is decoupled from error thereof, and then power grid voltage feedforward e is addeddFinally, the d-axis component U of the reference voltage vector is obtainedd *(ii) a Similarly, the q-axis is similar, so that the given current of the q-axis is 0 in order to realize the unit power factor;
(3): the obtained reference voltage vector q-axis component Uq *D-axis component Ud *Obtaining u through the contra-rotating coordinate transformation from the two-phase rotating coordinate system to the two-phase static coordinate systemrα，urβThen, carrying out SVPWM modulation of three levels to generate a driving signal to control the action of a power switch tube;
urαrepresenting the d-axis component U of the reference voltage vectord *Transforming the coordinates by reverse rotation to obtain a voltage value urβRepresenting the q-axis component U of a reference voltage vectorq *Converting the counter-rotating coordinate to obtain a voltage value;
(4): measured Udc1、Udc2Subtracting to obtain the potential difference delta U of the upper and lower capacitors on the DC sidedcControl of Delta U by a simple PI linkdcTherefore, the value of the n potential adjusting factor f of the middle position point is obtained, the action time of distributing the positive and negative small redundant vectors is calculated, and the charging and discharging time of the upper capacitor and the lower capacitor on the direct current side is distributed substantially, so that the problem of unbalanced point potential in the three-level rectifier is solved.
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