CN107888090B - Mixed three-phase rectifier with non-three-phase bridge arm symmetrical structure - Google Patents
Mixed three-phase rectifier with non-three-phase bridge arm symmetrical structure Download PDFInfo
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- CN107888090B CN107888090B CN201711405554.XA CN201711405554A CN107888090B CN 107888090 B CN107888090 B CN 107888090B CN 201711405554 A CN201711405554 A CN 201711405554A CN 107888090 B CN107888090 B CN 107888090B
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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
- H02M7/06—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode
-
- 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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/01—Arrangements for reducing harmonics or ripples
-
- 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
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M7/219—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
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- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
-
- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
Abstract
The mixed three-phase rectifier with the non-three-phase bridge arm symmetrical structure comprises a first rectifying circuit, a second rectifying circuit and a control circuit, wherein the first rectifying circuit and the second rectifying circuit are connected in parallel; the control circuit comprises a first sampling circuit, a first driving circuit, a second sampling circuit, a second driving circuit, a zero crossing signal detection circuit and a DSP processor; the output end of the first driving circuit is connected with the control end of the first rectifying circuit; the output end of the second driving circuit is connected with the control end of the second rectifying circuit; the output end of the first sampling circuit, the output end of the second sampling circuit and the output end of the zero crossing signal detection circuit are respectively connected with the input end of the DSP processor. The invention not only reduces the stress of the switching tube and reduces the production cost, but also has the advantages of easy digital realization of the control method, effective suppression of the alternating-current side harmonic wave, improvement of the working efficiency and realization of output power distribution and network side unit power factor operation.
Description
Technical Field
The invention relates to the field of three-phase rectifiers, in particular to a hybrid three-phase rectifier with a non-three-phase bridge arm symmetrical structure.
Background
With the rapid development of power electronics technology, power electronics devices are widely used in various fields of national economy. However, the large amount of power electronic devices also brings about some non-negligible problems, and at present, many current converting devices need a rectifying link to obtain a direct current level, and the traditional phase control rectification and diode rectification not only have low direct current side voltage quality, but also can inject a large amount of harmonic waves into a power grid, so as to cause 'pollution' of the power grid. In general, there are two approaches to suppress grid harmonic pollution: one is to provide compensation means, such as active, passive filters, but whose compensation characteristics are susceptible to the operating conditions and impedance characteristics of the grid; the other is to modify the converter, introduce PWM (Pulse Width Modulation pulse width modulation) technology into the rectifier, improve the dynamic response speed of the system, and realize the sine of the network side current and the unit power factor.
With the development of rectification technology in recent years, a three-phase three-level rectifier can enable a power switching device with low withstand voltage, low working current and small working current to be applied to high-voltage and high-power occasions, and current harmonics are remarkably reduced compared with two levels, so that the three-phase three-level rectifier is widely applied to industrial production, but how to further improve the working efficiency of the three-phase three-level rectifier, inhibit power grid harmonics, improve power factors, reduce production cost and other comprehensive performances becomes a great problem.
Disclosure of Invention
The invention aims to provide a mixed three-phase rectifier with a non-three-phase bridge arm symmetrical structure, which is used for further inhibiting power grid harmonic waves, improving power factors and working efficiency, reducing the number of fully-controlled devices, reducing production cost and realizing power distribution and network side current sine.
The technical scheme of the invention is a mixed three-phase rectifier with a non-three-phase bridge arm symmetrical structure, wherein the output ends of a first rectifying circuit and a second rectifying circuit are connected in parallel; the control circuit comprises a first sampling circuit, a first driving circuit, a second sampling circuit, a second driving circuit, a zero crossing signal detection circuit and a DSP processor; the output end of the first driving circuit is connected with the control end of the first rectifying circuit; the output end of the second driving circuit is connected with the control end of the second rectifying circuit; the output end of the first sampling circuit, the output end of the second sampling circuit and the output end of the zero crossing signal detection circuit are respectively connected with the input end of the DSP processor.
Further, the first rectifying circuit comprises a three-phase bridge type uncontrolled rectifying circuit and a DC-DC converter, the three-phase bridge type uncontrolled rectifying circuit and the DC-DC converter are sequentially connected in series, and the three-phase bridge type uncontrolled rectifying circuit is composed of 3 bridge arms formed by 6 diodes; the midpoints of the 3 bridge arms are used as three-phase alternating current input ends.
Further, the DC-DC converter is a Boost type Boost circuit.
Further, the second rectifying circuit is a diode clamped SVPWM rectifying circuit, and comprises a first bridge arm, a second bridge arm and a direct current side capacitor C 1 、C 2 The first bridge arm and the second bridge arm have the same circuit structure and are both provided with a first conduction switch S 1 Second conduction switch S 2 Third on switch S 3 Fourth on switch S 4 First clamping switch D 1 And a second clamp switch D 2 Constructing; the first conduction switch S 1 Is simultaneously connected with the second conduction switch S 2 And a first clamp switch D 1 A second conducting switch S connected with the cathode of the battery 2 Negative pole and third conduction switch S of (2) 3 A third conducting switch S 3 Is simultaneously connected with the fourth conduction switch S 4 Positive electrode of (D) and second clamp switch D 2 Is connected with the anode of the first clamping switch D 1 Anode and second clamp switch D of (2) 2 Is connected with the cathode of the battery; DC side capacitor C 1 、C 2 The capacitor C is connected in series in sequence and then connected with the first bridge arm and the second bridge arm in parallel 1 、C 2 Is taken as a neutral point n; the midpoints of clamping switches of the first bridge arm and the second bridge arm are respectively connected to a neutral point n; the midpoint of the first bridge arm, the midpoint of the second bridge arm and the neutral point n are respectively connected with a series reactor and then serve as three-phase alternating current input ends.
Preferably, the conducting switch is composed of an IGBT anti-parallel diode.
Preferably, the clamp switch is a diode.
Further, the first sampling circuit and the second sampling circuit comprise Hall voltage current sensors.
Further, the model of the DSP processor is TMS320F2812.
The control method for the mixed three-phase rectification of the non-three-phase bridge arm symmetrical structure comprises the following specific steps:
step 1: sampling DC side voltage U dc Output total current I dc First rectifying circuitStream I dc2 Determining a current distribution coefficient alpha by adopting an adaptive power distribution algorithm;
step 2: sampling three-phase bridge type uncontrolled rectifying circuit output current I indc2 Calculating the DC side voltage U dc With reference voltage U dref The error signal passes through a third PI controller, the output value of the third PI controller is multiplied by k (1-alpha), and the result is used as the current reference value of the current inner loop of the first rectifying circuit, and the current reference value and the sampling current I indc2 Comparing, the difference value passes through a fourth PI controller, and an SPWM signal is generated according to the output of the fourth PI controller and is used as a driving signal of a Boost type Boost circuit switching tube of the first rectifying circuit;
step 3: direct current side current I dc Multiplying by current distribution coefficient alpha and DC side voltage reference value U dref DC side voltage U dc As input of the sliding mode controller, the output of the sliding mode controller is used as active power reference quantity alpha P ref ；
Step 4: sampling active power P 2 Reactive power Q 2 And alternating voltage phase theta, calculating active power reference quantity alpha P ref And active power P 2 The error signal is passed through a second PI controller to obtain a reference voltage vector u rd ；
Step 5: let reactive power reference quantity Q ref =0, calculate reactive power Q 2 And reactive power reference quantity Q ref The error signal is passed through the first PI controller to obtain the reference voltage vector u rq ；
Step 6: will reference voltage vector u rd 、u rq Performing inverse rotation coordinate transformation from the two-phase rotation coordinate system to the two-phase stationary coordinate system to obtain u rα 、u rβ By performing SVPWM modulation, the generated PWM signal is used as a driving signal of a switching tube of a three-phase two-bridge arm three-level rectifying circuit.
In step 1, the adaptive power distribution algorithm specifically includes sampling voltage and current signals output from the DC sides of the first rectifying circuit and the second rectifying circuit by a sampling circuit to obtain output power, and changing when the load condition occursDuring conversion, the ratio of the output power of the two rectifying circuits will also change. By varying the reference value I of the current dref The power distribution of the output side is realized, and the unit power factor operation of the network side is ensured. The distribution coefficient of the current reference value is:
wherein P is O1 For outputting power of the second rectifying circuit, P O2 The power is output for the first rectifying circuit.
The reference given value of the current inner loop of the first rectifying circuit is k (1-alpha) I dc The method comprises the steps of carrying out a first treatment on the surface of the The second rectifying circuit gives a current reference value of alpha I dc 。
Further, in the step 3, the sliding mode controller is specifically designed as follows: the power outer ring describes the dynamic process of direct-current voltage through instantaneous active power and instantaneous reactive power balance equation, and selects a slip-form surface taking active power and reactive power as variables:
when the hybrid rectifier works in a unit power factor state and the reactive power is zero, the following steps are carried out:
Q ref ＝Q＝0 (3)
for the active power sliding mode surface, in any switching period, the equivalent impedance loss and the switching loss of the circuit are not counted, and the input power at the alternating current side is equal to the power at the direct current side, so that the following steps are included:
p in the formula ac For inputting power to AC side, P dc For DC side power, CU dc dU dc The/2 dt is the instantaneous power of the upper and lower capacitors on the DC side,for the instantaneous power of the load, the following steps can be obtained:
the two sub-units (2) and (4) are connected, and the direct control quantity of the power outer ring is U dc Slip form surface S 2 The method comprises the following steps of:
wherein K is a control coefficient and is not zero; reference U of DC voltage relative to power inner loop in one switching period dref Default to a fixed valueSubstituting formula (5) into (6) to obtain:
since (7) satisfies the slip plane S 2 ＝P ref -p=0, yielding
Output of the sliding mode controller:
the technical scheme adopts a self-adaptive power distribution algorithm to realize the power balance distribution between the first rectifying circuit and the second rectifying circuit; the PI controller with the power distribution coefficient and the correction coefficient is adopted for the first rectifying circuit, the PI sliding mode composite control strategy is adopted for the second rectifying circuit, the outer ring of the composite control strategy is controlled by adopting a power sliding mode variable structure, and the inner ring of the composite control strategy is controlled by adopting the PI controller.
The working principle of the invention is as follows: the first sampling circuit and the second sampling circuit collect voltage and current signals of a direct current side output end and an alternating current side input end, the voltage and current signals are transmitted into the DSP controller after A/D conversion, analysis and operation are carried out on the sampled signals through the DSP controller, three-level SVPWM modulation is further carried out, and then the switching-on and switching-off of switching devices of the three-phase two-bridge arm three-level rectifier of the first rectifying circuit and the second rectifying circuit are controlled through the driving circuit; the zero-crossing signal detection circuit detects the zero crossing point of the sinusoidal voltage, captures the rising edge through the DSP controller, realizes the phase locking of the power grid frequency, and provides a phase angle for the calculation of the control signal.
The beneficial effects of the invention are as follows: compared with the traditional three-phase three-level voltage type PWM rectifier, the switching tube stress is reduced, the production cost is reduced, the control method is easy to realize digitally, the alternating-current side harmonic wave can be effectively restrained, the working efficiency is improved, and the output power distribution and the network side unit power factor operation are realized.
Drawings
The invention is further described below with reference to the drawings and examples.
Fig. 1 is a block diagram of a circuit structure of the present invention.
Fig. 2 is a circuit diagram of the present invention.
Fig. 3 is a schematic diagram of a control circuit of the present invention.
Fig. 4 is an equivalent circuit diagram of the second rectifying circuit.
Fig. 5 is an equivalent circuit diagram of the second rectifying circuit in the operation mode 1.
Fig. 6 is an equivalent circuit diagram of the second rectifying circuit in the operation mode 2.
Fig. 7 is an equivalent circuit diagram of the second rectifying circuit in the operation mode 3.
Fig. 8 is an equivalent circuit diagram of the second rectifying circuit in the operation mode 4.
Fig. 9 is an equivalent circuit diagram of the second rectifying circuit in the operation mode 5.
Fig. 10 is an equivalent circuit diagram of the second rectifying circuit in the operation mode 6.
Fig. 11 is an equivalent circuit diagram of the second rectifying circuit in the operation mode 7.
Fig. 12 is an equivalent circuit diagram of the second rectifying circuit in the operation mode 8.
Fig. 13 is an equivalent circuit diagram of the second rectifying circuit in the operation mode 9.
Fig. 14 is a waveform of the current at the input side of the first rectifying circuit.
Fig. 15 is a waveform of the current at the input side of the second rectifying circuit.
Fig. 16 shows current and voltage waveforms at the input side of the present invention.
Fig. 17 is an output side voltage waveform of the present invention.
Detailed Description
The invention will be described in further detail with reference to the drawings and the detailed description.
As shown in fig. 1, in a hybrid three-phase rectifier with a non-three-phase bridge arm symmetrical structure, the output ends of the first rectifying circuit and the second rectifying circuit are connected in parallel; the control circuit comprises a first sampling circuit, a first driving circuit, a second sampling circuit, a second driving circuit, a zero crossing signal detection circuit and a DSP processor; the output end of the first driving circuit is connected with the control end of the first rectifying circuit; the output end of the second driving circuit is connected with the control end of the second rectifying circuit; the output end of the first sampling circuit, the output end of the second sampling circuit and the output end of the zero crossing signal detection circuit are respectively connected with the input end of the DSP processor.
The first rectifying circuit comprises a three-phase bridge type uncontrolled rectifying circuit and a DC-DC converter, the three-phase bridge type uncontrolled rectifying circuit and the DC-DC converter are sequentially connected in series, and the three-phase bridge type uncontrolled rectifying circuit is composed of 3 bridge arms formed by 6 diodes; the midpoints of the 3 bridge arms are used as three-phase alternating current input ends after passing through the series reactors. The DC-DC converter is a Boost type Boost circuit.
As shown in FIG. 2, V a (t)、V b (t)、V c (t) is three-phase symmetrical phase voltage, i a1 、i b1 、i c1 Three-phase current i is input to the network side of the second rectifying circuit a2 、i b2 、i c2 Three-phase current is input to the grid side of the first rectifying circuit; l (L) 1 、L 2 、L 3 The filter inductance on the net side of the second rectifying circuit (the three-phase filter inductances are equal in size) R 1 、R 2 、R 3 Is equivalent resistance L 4 、L 5 、L 6 The net side filter inductance of the first rectifying circuit (the three-phase filter inductance is equal in size); l (L) d A Boost inductor of a Boost type DC-DC converter in the first rectifying circuit; s is S 1 、S 2 、S 6 、S 7 Is an upper bridge arm IGBT (Insulated Gate Bipolar Transistor composite full-control voltage-driven power semiconductor switch tube) of a second rectifying circuit, S 3 、S 4 、S 8 、S 9 Is the lower bridge arm IGBT of the second rectifying circuit, S 5 A switching tube for a DC-DC converter; c (C) 1 、C 2 R is a direct-current side capacitor L Is a resistive load; u (U) dc For outputting voltage at DC side, I dc For outputting total current at DC side, I d1 For outputting current at the DC side of the second rectifying circuit, I dc2 The current is output for the direct current side of the first rectifying circuit.
The three-phase diode bridge of the first rectifying circuit consists of six diodes, and the input end of the three-phase diode bridge is connected with a three-phase alternating current power supply V a (t)、V b (t)、V c (t) the same phase access terminal is connected, the output terminal is connected in series with the boost inductor L in turn d Parallel switch tube S 5 A diode D5 is connected in series and then connected with a capacitor C in series 1 、C 2 Resistive load R L Parallel connection of the diodes D 5 Ensuring unidirectional flow of energy in the first rectifying circuit. Two bridge arms of the second rectifying circuit are composed of IGBT and diode, and input a phase passes through a reactor L 1 Is connected with the midpoint of the arm a, and inputs phase b through a reactor L 2 Is connected with the midpoint of the bridge arm b, and is input with the phase c through a reactor L 3 Directly connected to the neutral point n. The upper bridge arm and the lower bridge arm of each bridge arm are respectively composed of 2 IGBT (insulated gate bipolar transistors) connected in series, 2 diodes connected in series are connected between the middle points of the upper bridge arm and the lower bridge arm (the cathodes of the diodes connected in series are connected with the middle point of the upper bridge arm), each IGBT is connected in anti-parallel with the diode, and the middle point of the diode connected in series of each bridge arm is connected with a neutral point n; the upper and lower nodes of each bridge arm are respectively connected with an output capacitor C in series 1 、C 2 And a resistive load R L Connected in parallel. The alternating current side inductor is mainly used for filtering current harmonic waves at the net side, and the direct current side capacitor C 1 、C 2 As an energy storage element, providing a smooth voltage output; the first rectifying circuit and the second rectifying circuit work in different topological structures and working frequencies, are connected in parallel to supply power to the same load, and input currents of the first rectifying circuit and the second rectifying circuit are synthesized into sinusoidal currents synchronous with the network side voltage.
It should be further described that the topology structure adopted by the second rectifying circuit in the present invention has an equivalent circuit as shown in fig. 4, wherein S a =1 means S 1 And S is 2 Conducting; s is S a =0 means S 2 And S is 3 Conducting; s is S a = -1 represents S 3 And S is 4 Conducting. S is S b =1 means S 6 And S is 7 Conducting; s is S b =0 means S 7 And S is 8 Conducting; s is S b = -1 represents S 8 And S is 9 Conducting. Assume that neutral point n is in dynamic voltage balance state, and U C1 ＝U C2 ＝U dc V is/2 an 、V bn Respectively have 3 levels-U dc /2、0、U dc /2，V ab There are 5 levels-U dc 、-U dc /2、0、U dc /2、U dc The voltage withstand value of each switch tube is U dc And 2, the voltage stress of the switching tube is effectively reduced, and the production cost is reduced. As can be seen from the equivalent circuit, the three-phase two-bridge arm three-level rectifier has 9 working modes, and is specifically shown in fig. 5-13:
1) Working mode 1 (S) a ＝0,S b ＝0；S 2 、S 3 、S 7 、S 8 Conduction): v (V) an ＝V bn ＝V ab The equivalent circuit diagram is shown in fig. 5.
2) Working mode 2 (S) a ＝1,S b ＝0；S 1 、S 2 、S 7 、S 8 Conduction): v (V) an ＝V ab ＝U dc /2,V bn ＝0；
Current i a Reduced when V bc At > 0, i b Increase when V bc When < 0, i b The reduction, equivalent circuit diagram is shown in fig. 6.
3) Mode of operation 3 (S a ＝1,S b ＝1；S 1 、S 2 、S 6 、S 7 Conduction): v (V) an ＝V bn ＝U dc /2,V ab =0; current i a 、i b Reduction, i c The equivalent circuit diagram is shown in fig. 7.
4) Working mode 4 (S) a ＝0,S b ＝1；S 2 、S 3 、S 6 、S 7 Conduction): v (V) an ＝0,V bn ＝U dc /2,V ab ＝-U dc 2; when V is ac At > 0, current i a Increase when V ac When < 0, i a A reduction; current i b The reduction, equivalent circuit diagram is shown in fig. 8.
5) Working mode 5 (S) a ＝-1,S b ＝1；S 3 、S 4 、S 6 、S 7 Conduction): v (V) an ＝-U dc /2,V bn ＝U dc /2,V ab ＝-U dc Current i a Increase, i b The reduction, equivalent circuit diagram is shown in fig. 9.
6) Working mode 6 (S) a ＝-1,S b ＝0；S 3 、S 4 、S 7 、S 8 Conduction): v (V) an ＝-U dc /2,V bn ＝0,V ab ＝-U dc /2, current i a Increase when V bc At > 0, i b Increase when V bc When < 0, i b The reduction, equivalent circuit diagram is shown in fig. 10.
7) Working mode 7 (S) a ＝-1,S b ＝-1；S 3 、S 4 、S 8 、S 9 Conduction): v (V) an ＝-U dc /2,V bn ＝-U dc /2,V ab =0, current i a 、i b Increase, i c The reduction, equivalent circuit diagram is shown in fig. 11.
8) Worker's workWorking mode 8 (S) a ＝0,S b ＝-1；S 2 、S 3 、S 8 、S 9 Conduction): v (V) an ＝0,V bn ＝-U dc /2,V ab ＝U dc 2, when V ac At > 0, i a Increase when V ac When < 0, i a Reduction of current i b The equivalent circuit diagram is shown in fig. 12.
9) Working mode 9 (S) a ＝1,S b ＝-1；S 1 、S 2 、S 8 、S 9 Conduction): v (V) an ＝U dc /2,V bn ＝-U dc /2,V ab ＝U dc Current i a Reduction, i b The equivalent circuit diagram is shown in fig. 13.
The control circuit of the invention is composed of a sampling circuit, a DSP controller, a zero crossing signal detection circuit, an auxiliary power supply module, a drive protection circuit and the like; the power distribution can achieve distribution of output power only by distributing direct-current side current, the control circuit adopts a self-adaptive power distribution algorithm to achieve direct-current side current distribution between two rectifiers, and alpha is a current distribution coefficient; and the output of the outer sliding mode controller is a reference value of the inner ring active power.
A PI controller is adopted for the voltage control loop of the first rectifying circuit, and the input of the voltage PI controller is the sampling voltage U at the direct current side dc The DC side voltage gives a reference value U dcref Generating a reference current value of a current inner loop by the output value of the voltage PI controller, and introducing a division coefficient k (1-alpha) for distributing power to the rectifying module, wherein k is a correction coefficient, and k is more than 0 and less than or equal to 1000; thereby obtaining the reference value of the current inner loop as k (1-alpha) I dc The sampling circuit obtains a current sampling value as I indc2 Taking the difference value of the two as the input of a PI controller, generating an SPWM signal by the output of the PI controller through a related driving circuit, and taking the SPWM signal as the driving signal of a Boost type Boost circuit switching tube of a first rectifying circuit; aiming at the second rectifying circuit, a PI sliding mode composite control strategy is adopted, an outer ring of the composite control strategy adopts a sliding mode variable structure controller, and an inner ring adoptsAnd a PI controller.
The specific control process is as follows: the effective value of the three-phase voltage is 220V/50Hz, and the inductance L at the alternating current side 1 ＝4mH、L 2 =2mh, boost inductance L d =4mh, capacitance C 1 ＝C 2 =c=2200 uF; the switching frequency of the first rectifying circuit is 10kHz, the switching frequency of the second rectifying circuit is 12kHz, the expected value of output voltage is 650V, the design is performed by comprehensively considering the dynamic performance and the steady-state performance of the system, and the third PI control parameter of the voltage outer ring of the first rectifying circuit is more than 0 and less than K p3 ≤58，K i3 =11, the fourth PI control parameter in the first rectifying circuit is K p4 ＝45，K i4 =15; the first PI control parameter of the second rectifying circuit is K p1 ＝40，K i1 =22, the second PI control parameter in the second rectifying circuit is 0 < K p2 ≤42，K i2 The external loop sliding mode control parameter k=120, and the controller adopts a TMS320F2812 model DSP chip as core operation, sampling control, power distribution, driving signal distribution and the like. Sampling as shown in FIG. 3 to obtain DC side output voltage U dc Output current I dc 、I d1 、I dc2 Calculating a current distribution coefficient α=p O1 /(P O1 +P O2 )＝(I dc -I dc2 )/I dc Reference amount of distributed current k (1-alpha) I dc And the current actual value I indc2 The error is output to the DSP chip through the PI regulator to generate an SPWM signal, and the power control of the first rectifying circuit is realized through the driving circuit. For the second rectifying circuit, the distributed current αI dc With a given voltage U dref Output voltage U dc The reference quantity alpha P of the active power is obtained through the output of the sliding mode controller ref . Reference quantity Q of reactive power in unit power factor operation ref =0; actual value P of instantaneous active power 2 Actual value Q of instantaneous reactive power 2 The phase of the network side voltage is obtained by sampling an alternating current side; the error between the reference quantity and the actual value of the active power and the reactive power is subjected to unit power factor control through the PI controllers, and the output of the two PI controllers of the power inner loop is the reference voltage vector u rd ，u rq The method comprises the steps of carrying out a first treatment on the surface of the Then the u is obtained through the inverse rotation coordinate transformation from the two-phase rotation coordinate system to the two-phase static coordinate system rα ，u rβ The method comprises the steps of carrying out a first treatment on the surface of the Therefore, three-level SVPWM modulation is carried out, a driving signal is generated, and power control of the second rectifying circuit and unit power factor control of the network side are realized.
Fig. 14 shows a waveform of a stable current at the input side of the first rectifying circuit, which is verified by simulation according to the control parameters listed in the specific implementation process, and the waveform can be seen that the waveform of the current output by the first rectifying circuit is distorted, and the working state is similar to that of the active filter; fig. 15 is a current waveform of the input side of the second rectifying circuit, and it can be found by comparing the waveforms of fig. 14 and 15, the current waveforms of fig. 14 and 15 are superimposed to form a waveform of fig. 16, and fig. 16 is a current waveform of the input side of the device, from which it can be seen that the total current has a better sinusoidal degree, and the total current and the voltage are in the same phase, so as to meet the output requirement of the rectifier, and the volume of the hybrid rectifier can be greatly reduced due to the reduction of the number of capacitors during the actual circuit design.
Fig. 17 shows a dc side voltage output waveform of the device, and it can be seen from the figure that the hybrid rectifier can stably output a dc voltage, and stabilize the dc voltage to 650V, and the stabilizing time reaches about one power frequency period from the initial time.
The DSP processor performs power balance distribution on the first rectifying circuit and the second rectifying circuit through the control circuit. And the harmonic wave is effectively restrained, and the stable output of the voltage and the unit power factor control at the network side are realized. According to the invention, the three-level rectification parallel connection of the three-phase cascade uncontrolled boost rectifier and the non-three-phase bridge arm symmetrical structure can reduce the capacitance and improve the power density of the converter, so that the working efficiency of the rectifier is greatly improved; the total number of the adopted full-control devices of the hybrid three-level rectifier is only 9, and compared with the traditional three-level rectifier bridge circuit, the full-control device has the advantages of reducing the use quantity of the full-control devices and saving the cost.
Claims (6)
1. The utility model provides a mixed three-phase rectifier of non-three-phase bridge arm symmetrical structure, includes first rectifier circuit, second rectifier circuit and control circuit, its characterized in that: the output ends of the first rectifying circuit and the second rectifying circuit are connected in parallel; the control circuit comprises a first sampling circuit, a first driving circuit, a second sampling circuit, a second driving circuit, a zero crossing signal detection circuit and a DSP processor; the output end of the first driving circuit is connected with the control end of the first rectifying circuit; the output end of the second driving circuit is connected with the control end of the second rectifying circuit; the output end of the first sampling circuit, the output end of the second sampling circuit and the output end of the zero crossing signal detection circuit are respectively connected with the input end of the DSP processor;
the first rectifying circuit comprises a three-phase bridge type uncontrolled rectifying circuit and a DC-DC converter, the three-phase bridge type uncontrolled rectifying circuit and the DC-DC converter are sequentially connected in series, and the three-phase bridge type uncontrolled rectifying circuit is composed of 3 bridge arms formed by 6 diodes; midpoints of the 3 bridge arms are connected with a reactor in series and then serve as three-phase alternating current input ends;
the DC-DC converter is a Boost circuit;
the second rectifying circuit is a diode clamping SVPWM rectifying circuit and comprises a first bridge arm, a second bridge arm and a direct current side capacitor C 1 DC side capacitor C 2 The first bridge arm and the second bridge arm have the same circuit structure and are both provided with a first conduction switch S 1 Second conduction switch S 2 Third on switch S 3 Fourth on switch S 4 First clamping switch D 1 And a second clamp switch D 2 Constructing; the first conduction switch S 1 Is simultaneously connected with the second conduction switch S 2 And a first clamp switch D 1 A second conducting switch S connected with the cathode of the battery 2 Negative pole and third conduction switch S of (2) 3 A third conducting switch S 3 Is simultaneously connected with the fourth conduction switch S 4 Positive electrode of (D) and second clamp switch D 2 Is connected with the anode of the first clamping switch D 1 Anode and second clamp switch D of (2) 2 Is connected with the cathode of the battery; DC side capacitor C 1 DC side capacitor C 2 The capacitor C is connected in series in sequence and then connected with the first bridge arm and the second bridge arm in parallel, and is a direct-current side capacitor C 1 DC side power supplyCapacitor C 2 Is taken as a neutral point n; the midpoints of clamping switches of the first bridge arm and the second bridge arm are respectively connected to a neutral point n; the midpoint of the first bridge arm, the midpoint of the second bridge arm and the neutral point n are respectively connected with a reactor in series and then serve as three-phase alternating current input ends;
the rectification control method of the hybrid three-phase rectifier comprises the following steps:
step 1: sampling DC side voltage U dc Output total current I dc First rectifying circuit current I dc2 Determining a current distribution coefficient alpha by adopting an adaptive power distribution algorithm;
step 2: sampling three-phase bridge type uncontrolled rectifying circuit output current I indc2 Calculating the DC side voltage U dc With reference voltage U dref The error signal passes through a third PI controller, the output value of the third PI controller is multiplied by k (1-alpha), k is a correction coefficient, the result is used as the current reference value of the current inner loop of the first rectifying circuit, and the current reference value and the three-phase bridge type uncontrolled rectifying circuit output current I indc2 Comparing, the difference value passes through a fourth PI controller, and an SPWM signal is generated according to the output result of the fourth PI controller and is used as a driving signal of a Boost type Boost circuit switch tube of the first rectifying circuit;
step 3: will output the total current I dc Multiplying by current distribution coefficient alpha, and reference voltage U dref DC side voltage U dc As input of the sliding mode controller, the output of the sliding mode controller is used as active power reference quantity alpha P ref ；
Step 4: sampling active power P 2 Reactive power Q 2 And alternating voltage phase theta, calculating active power reference quantity alpha P ref And active power P 2 The error signal is passed through a second PI controller to obtain a reference voltage vector u rd ；
Step 5: let reactive power reference quantity Q ref =0, calculate reactive power Q 2 And reactive power reference quantity Q ref The error signal is passed through the first PI controller to obtain the reference voltage vector u rq ；
Step 6: will reference voltage vector u rd Reference voltage vector u rq Performing inverse rotation coordinate transformation from the two-phase rotation coordinate system to the two-phase stationary coordinate system to obtain u rα 、u rβ By performing the SVPWM modulation, the generated PWM signal is used as a driving signal for the diode-clamped SVPWM rectifying circuit on-switch.
2. The hybrid three-phase rectifier of non-three-phase bridge leg symmetry of claim 1, wherein: the conduction switch consists of an IGBT anti-parallel diode.
3. The hybrid three-phase rectifier of non-three-phase bridge leg symmetry of claim 1, wherein: the clamp switch is a diode.
4. The hybrid three-phase rectifier of non-three-phase bridge leg symmetry of claim 1, wherein: the first and second sampling circuits include hall voltage current sensors.
5. The hybrid three-phase rectifier with the non-three-phase bridge arm symmetrical structure according to claim 1, wherein in the step 1, the adaptive power distribution algorithm samples output voltage and current signals of the direct current sides of the first rectifying circuit and the second rectifying circuit according to the sampling circuit to obtain output power of the first rectifying circuit and the second rectifying circuit, and when the load condition changes, the ratio of the output power of the first rectifying circuit and the output power of the second rectifying circuit also changes; by varying the reference value I of the current dref The power distribution of the output side is realized, the power factor of the network side is controlled, and the current distribution coefficient is as follows:
wherein P is O1 For outputting power of the second rectifying circuit, P O2 Outputting power for the first rectifying circuit;
the current inner loop of the first rectifying circuit is given a referenceHaving a value of k (1-alpha) I dc The method comprises the steps of carrying out a first treatment on the surface of the The given reference value of the second rectifying circuit current is alpha I dc 。
6. The hybrid three-phase rectifier of non-three-phase bridge arm symmetrical structure according to claim 1, wherein in step 3, the slip-mode controller follows the instantaneous active power and instantaneous reactive power balance equation, and selects slip-mode surfaces with active power and reactive power as variables:
for the active power sliding mode surface, in any switching period, the equivalent impedance loss and the switching loss of the circuit are not counted, and the input power at the alternating current side is equal to the power at the direct current side, so that the following steps are included:
p in the formula ac For inputting power to AC side, P dc The power of the direct current side is C is the capacitance value of an upper capacitor and a lower capacitor of the direct current side, R L Representing load resistance, CU dc dU dc The/2 dt is the instantaneous power of the upper and lower capacitors on the DC side,for the instantaneous power of the load, the following steps can be obtained:
combined type son (2) and formula (3), sliding die surface S 2 The process is as follows:
wherein K is a control coefficient and is not zero; in one switching period, reference voltage U dref Is of a constant value, thenSubstituting formula (4) into formula (5):
since (6) satisfies the slip plane S 2 ＝P ref -p=0, yielding
Output of the sliding mode controller:
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