CN114865931A - Carrier discontinuous modulation method of three-phase Vienna rectifier - Google Patents
Carrier discontinuous modulation method of three-phase Vienna rectifier Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/12—Arrangements for reducing harmonics from ac input or output
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- 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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- 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
- H02M7/23—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 arranged for operation in parallel
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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
- H02M7/25—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 arranged for operation in series, e.g. for multiplication of voltage
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
The invention discloses a carrier discontinuous modulation method of a three-phase Vienna rectifier, which is characterized in that normalized sine waves of a phase voltage A, a phase voltage B and a phase voltage C are respectively u phase voltages according to a three-phase normalization formula of a SPWM (sinusoidal pulse Width modulation) strategy of the three-phase Vienna rectifier ma ,u mb ,u mc (ii) a Defining the maximum value of three-phase normalized sine wave at a certain time as u max An intermediate value of u mid Minimum value of u min (ii) a The zero sequence voltage injected is u when the load is balanced z1 The modulation method is in u mid Time scale u is more than or equal to 0 z1 =max(‑u mid ,‑1‑u min ) In u mid < 0 season u z1 =min(‑u mid ,1‑u max ) (ii) a When the load is unbalanced, the injected zero sequence voltage is u z2 The modulation method is in u mid Time scale u is more than or equal to 0 z2 =max(‑u mid ,‑2U dc2 /U dc ‑u min ) In u mid < 0 season u z2 =min(‑u mid ,2U dc1 /U dc ‑u max ) (ii) a And by applying a zero sequence voltage u z1 /u z2 And injecting the three-phase normalized sine wave to obtain the three-phase modulation wave of the three-phase Vienna rectifier.
Description
Technical Field
The invention relates to the field of power electronics, in particular to a carrier intermittent modulation method of a three-phase Vienna rectifier.
Background
The three-phase Vienna rectifier has the advantages of high efficiency, high power density and unit power factor, and is suitable for high-frequency three-phase power factor correction occasions, such as the fields of electric automobile charging, aerospace power supplies and the like. Aviation applications require converters with the characteristics of miniaturization and higher power density. High power density means that the switching frequency of the switching tube of the device needs to be increased. However, at a higher switching frequency of the switching tube, on one hand, buffering of the switching device, circuit and parasitic parameters affect the switching transient process, resulting in poor input current waveform quality; on the other hand, the switching loss of the converter is increased, the overall efficiency of the system is reduced, the calculation period is shortened, and a large calculation load is brought to the controller.
The literature, "Hang Lijun, Li Bin, Zhang Ming, et al, Eq effectiveness of SVM and Carrier-Based PWM in Three-Phase/Wire/Level Vinnna Rectifier and Capability of Unbase-Load control IEEE Transactions on Industrial Ele ctronics 2014,61(1):20-28. Compared with space vector modulation, carrier modulation generally only needs comparison and simple calculation, and is more suitable for high-frequency application. Documents "z.zhang, o.c. thomsen, and m.a.e. andersen, discrete PWM modulation strategy with circuit-level decoupling concept of thyristor connected-point-clamped (npc) inverter, IEEE trans.ind.electron, vol.60, No.5, pp.1897-1906, May 2013" propose a method of Discontinuous carrier modulation for a conventional three-level converter body, but this method cannot satisfy the important condition that the reference voltage and the current are in phase near the zero crossing of the current, and this method, when applied to a vienna rectifier, cannot realize unit power operation and introduces additional low-frequency harmonics to the input current. This method is therefore not suitable for vienna rectifiers. Documents "LeeJ, Lee k. carrier-based discrete PWM methods for video receivers [ J ], ieee transactions on Power Electronics, 2015, 30 (6): 2896-. However, this method adds additional intermediate variables and judgment conditions, which complicates its calculation. For the case of Unbalanced midpoint voltage, documents "x.wu, g.tan, g.yao, c.sun and g.liu, a hybrid PWM Strategy for Three-Level Inverter With Unbalanced DC Links, in IEEE Journal of emitting and Selected Topics in Power Electronics, vol.6, No.1, pp.1-15, March 2018" propose a hybrid modulation method of SVPWM and CBPWM, which can make the T-type Inverter still operate in the state of Unbalanced midpoint voltage, but when the method is applied to a vienna rectifier, the reference voltage and the current cannot be in phase at the zero crossing of the current, resulting in poor current THD performance. For the case of load imbalance, documents "y.ming et al", "a Hybrid Carrier-Based DPWM with Controllable NP Voltage for Three-Phase Vi enna modulators", "in IEEE Transactions on transmission electric configuration, doi: 10.1109/tte.2021.3129778" propose a Carrier discontinuous modulation method, which changes the effect of zero-sequence components by introducing different adjustment coefficients, reduces the problem of current zero-crossing distortion, but this method needs to perform complex sector determination, determines a plurality of coefficients according to different sectors and the positive and negative of reference Voltage, and increases the comparison of intermediate variables, the determination steps are more complicated, and the implementation is more complicated.
Therefore, it is necessary to research a vienna rectifier carrier discontinuous modulation method which is simple in calculation and easy to implement under the conditions of load balance and load imbalance, so as to reduce the operation burden of the controller and improve the input current waveform quality.
Disclosure of Invention
The invention aims to provide a carrier intermittent modulation method of a three-phase Vienna rectifier, so that the Vienna rectifier can reduce the zero-crossing distortion of current under the conditions of load balance and load unbalance, the quality of input current is improved, a calculation method is simplified, and the calculation burden of a digital controller is reduced.
The invention discloses a three-phase Vienna rectifier carrier discontinuous modulation method, which comprises the following steps: obtaining the normalized sine waves of the A phase, the B phase and the C phase as u respectively according to a three-phase normalization formula of a SPWM (sinusoidal pulse Width modulation) strategy of the three-phase Vienna rectifier ma ,u mb ,u mc (ii) a Defining the maximum value of A-phase, B-phase and C-phase normalized sine waves at a certain moment as u max An intermediate value of u mid Minimum value of u min (ii) a When the load is balanced, the zero sequence voltage is injected to be u z1 The modulation method of the invention is in mid Time scale u is more than or equal to 0 z1 =max(-u mid ,-1-u min ) In u mid < 0 hour u z1 =min(-u mid ,1-u max ) (ii) a When the load is unbalanced, the zero sequence voltage is injected to be u z2 The modulation method of the invention is in mid Time scale u is more than or equal to 0 z2 =max(-u mid ,-2U dc2 /U dc -u min ) In u mid < 0 season u z2 =min(-u mid ,2U dc1 /U dc -u max ) (ii) a And by applying a zero sequence voltage u z1 /u z2 And injecting a three-phase normalized sine wave to obtain a three-phase modulation wave of the Vienna rectifier.
The three-phase Vienna rectifier carrier intermittent modulation method specifically comprises the following steps:
1. obtaining three-phase normalized sine wave, and calculating the maximum value, the intermediate value and the minimum value of the three-phase normalized sine wave
Obtaining an A-phase voltage normalized sine wave u according to a three-phase normalization formula of a three-phase Vienna rectifier SPWM (sinusoidal pulse Width modulation) strategy ma B-phase voltage normalization sine wave u mb C phase voltage normalization sine wave u mc The method for obtaining the three-phase normalized sine wave comprises the following specific steps:
in the formula (I), f g For the frequency of the power grid, m is a modulation ratio, m belongs to (0,1), and the modulation ratio m can be expressed by a formulaIs obtained by m Representing the amplitude, U, of the AC reference phase voltage dc The dc-side bus voltage is shown.
Obtaining the normalized sine wave u of the phase voltage A, the phase voltage B and the phase voltage C at a certain moment ma ,u mb ,u mc Respectively is u max ,u mid ,u min 。
2. Determining zero sequence voltage u in load balancing z1
Defining the zero sequence voltage in load balance as u z1 U of the invention z1 The determination method comprises the following steps:
in the above formula, u z1 Representing the zero sequence voltage injected in load balancing; u. of max ,u mid ,u min Respectively shows the normalized sine wave u of phase A, phase B and phase C at a certain time ma ,u mb ,u mc Maximum, median and minimum values of; min (-u) mid ,1-u max ) Represents obtaining-u mid And 1-u max Minimum value of (d): when-u mid ≤1-u max Hour, min (-u) mid ,1-u max )=-u mid When 1-u is max <-u mid Hour, min (-u) mid ,1-u max )=1-u max ;max(-u mid ,-1-u min ) Represents obtaining-u mid And-1-u min Maximum value of (d): when-u mid ≥-1-u min Max (-u) mid ,-1-u min )=-u mid When 1-u min >-u mid Max (-u) of mid ,-1-u min )=-1-u min 。
3. Obtaining three-phase modulation wave in load balance
Defining three-phase modulation waves of the Vienna rectifier after the zero-sequence component is injected into the three-phase modulation waves as u ref_x And x is a, b and c, and the method for obtaining the three-phase modulated wave in load balance comprises the following steps:
u ref_x =u mx +u z1 ,x=a,b and c (Ⅲ)
in the formula (III), u ref_x X is a, b, and c represents three-phase modulated wave of wiener rectifier, u mx X ═ a, b, and c denotes a three-phase normalized sine wave, u z1 Representing the zero sequence voltage injected at load balance.
5. Determining zero sequence voltage u when load is unbalanced z2
Defining the zero sequence voltage in load balance as u z2 U of the invention z2 The determination method comprises the following steps:
u z2 indicating zero sequence voltage, u, under load unbalance conditions or injection max ,u mid ,u min Respectively shows the normalized sine wave u of phase A, phase B and phase C at a certain time ma ,u mb ,u mc Maximum, median and minimum, U dc1 、U dc2 Respectively representing the upper and lower capacitor voltages, U, of the DC-side bus dc Represents the total voltage of the DC side bus in min (-u) mid ,2U dc1 /U dc -u max ) Expression to find-u mid And 2U dc1 /U dc -u max Minimum value of (d): when-u mid ≤2U dc1 /U dc -u max Hour, min (-u) mid ,1-u max )=-u mid When 2U is used dc1 /U dc -u max <-u mid Hour, min (-u) mid ,1-u max )=2U dc1 /U dc -u max ;max(-u mid ,-2U dc2 /U dc -u min ) Represents obtaining-u mid and-2U dc2 /U dc -u min Maximum value of (c): when-u mid ≥-2U dc2 /U dc -u min Max (-u) of mid ,-1-u min )=-u mid When is-2U dc2 /U dc -u min >-u mid Max (-u) mid ,-1-u min )=-2U dc2 /U dc -u min 。
6. Obtaining three-phase modulated wave when load is unbalanced
Defining three-phase modulation waves of the Vienna rectifier after the zero-sequence component is injected into the three-phase modulation waves as u ref_x And x is a, b and c, and the method for obtaining the three-phase modulated wave when the load is unbalanced is as follows:
in the formula (V), u ref_x X ═ a, b, and c denotes a three-phase modulated wave of a wiener rectifier, u mx X ═ a, b, and c denotes a three-phase normalized sine wave, u z2 Indicating zero sequence voltage, U, under load unbalance conditions or injection dc1 、U dc2 Respectively representing the upper side capacitance voltage and the lower side capacitance voltage of a DC side bus, U dc Representing the total dc side bus voltage.
The invention discloses a three-phase Vienna rectifier carrier intermittent modulation method, which has the following beneficial effects:
the invention can improve the input current quality and the current waveform quality of the three-phase Vienna rectifier under the conditions of load balance and load unbalance, has simple judgment condition and short required time of the modulation wave calculation process, and can reduce the operation burden of the digital controller.
Drawings
Fig. 1 is a main circuit topology structure diagram of a carrier discontinuous modulation method of a three-phase vienna rectifier;
FIG. 2 is a flowchart illustrating an exemplary implementation of a three-phase Vienna rectifier carrier modulation method according to the present invention;
FIG. 3 is a graph of the relationship between the waveform and the sector of a three-phase normalized sine wave signal in one cycle according to the present invention;
FIG. 4 is a diagram of the clamping mode of the method of the present invention during load balancing;
FIGS. 5a and 5b are graphs of clamping modes of the method of the present invention under unbalanced load, FIG. 5a is a graph of clamping modes of the load resistor R1< R2, and FIG. 5b is a graph of clamping modes of the load resistor R1> R2;
FIGS. 6a and 6b are waveform diagrams of circuit simulation under load balancing conditions by using the modulation method of the present invention;
fig. 7a and 7b are waveform diagrams of circuit simulation under the condition of unbalanced load by adopting the modulation method of the invention.
Detailed Description
The invention is further described with reference to the following figures and detailed description.
Fig. 1 to 7 show a method for discontinuous modulation of a carrier of a three-phase vienna rectifier according to the present invention.
As shown in FIG. 1, the main circuit topology structure of the present invention includes a voltage source e of phase A electricity a B-phase electric voltage source e b C-phase voltage source e c First to third inductors L a 、L b 、L c First to sixth diodes D a+ 、D a- 、D b+ 、D b- 、D c+ 、D c- First to sixth switching tubes Q 1 、Q 2 、Q 3 、Q 4 、Q 5 、Q 6 First capacitor C 1 A second capacitor C 2 First resistance R 1 A second resistor R 2 Voltage source e of phase A electricity a B-phase electric voltage source e b C-phase voltage source e c Are connected together, a first inductance L a Voltage source e connected in series to phase A a And a first diode D a+ Between the anodes of the first and second inductors L b Voltage source e connected in series with B phase electricity b And a third diode D b+ Between the anodes of the first and second inductors L c Voltage source e connected in series to C-phase power c And a fifth diode D c+ Between the anodes of the first and second diodes D a- A fourth diode D b- A sixth diode D c- Are connected together as point N, and the anodes are respectively connected with the first diode D a+ Anode of (2), third diode D b+ Anode of (2), fifth diode D c+ Is connected to the anode of a second switching tube Q 2 And a fourth switching tube Q 4 And a sixth switching tube Q 6 Is connected together and is marked as the point O, a first switch tube Q 1 A second switch tube Q 2 Connected in series and then connected to a first diode D a+ Between the anode and the point O, a third switching tube Q 3 And a fourth switching tube Q 4 Connected in series to a third diode D b+ Between the anode of (1) and the point O, a fifth switching tube Q 5 And a sixth switching tube Q 6 Connected in series to a fifth diode D c+ Between the anode and the point O, a first diode D a+ Anode of (2), third diode D b+ A fifth diode D c+ Are connected together, denoted as point P, a first capacitance C 1 And a first resistor R 1 A second capacitor C connected in parallel between the point P and the point O 2 And a second resistor R 2 In parallel between point N and point O.
The invention discloses a three-phase Vienna rectifier carrier discontinuous modulation method, which comprises the following steps: obtaining the normalized sine waves of the A phase, the B phase and the C phase as u respectively according to a three-phase normalization formula of a SPWM (sinusoidal pulse Width modulation) strategy of the three-phase Vienna rectifier ma ,u mb ,u mc (ii) a Defining the maximum value of A-phase, B-phase and C-phase normalized sine waves at a certain moment as u max An intermediate value of u mid Minimum value of u min (ii) a When the load is balanced, the zero sequence voltage is injected to be u z1 The modulation method of the invention is in mid Time scale u is more than or equal to 0 z1 =max(-u mid ,-1-u min ) In u mid < 0 season u z1 =min(-u mid ,1-u max ) (ii) a When the load is unbalanced, the zero sequence voltage is injected to be u z2 The modulation method of the invention is in mid Time scale u is more than or equal to 0 z2 =max(-u mid ,-2U dc2 /U dc -u min ) In u mid < 0 season u z2 =min(-u mid ,2U dc1 /U dc -u max ) (ii) a And by applying a zero sequenceVoltage u z1 /u z2 And injecting a three-phase normalized sine wave to obtain a three-phase modulation wave of the Vienna rectifier.
As shown in fig. 2, the specific process of the three-phase vienna rectifier carrier intermittent modulation method of the present invention is as follows:
1. obtaining three-phase normalized sine wave, and calculating the maximum value, the intermediate value and the minimum value of the three-phase normalized sine wave
According to a three-phase normalization formula of a three-phase Vienna rectifier SPWM (sinusoidal pulse Width modulation) strategy, the sine waves of a normalized phase A, a normalized phase B and a normalized phase C are respectively u ma ,u mb ,u mc The method for obtaining the three-phase normalized sine wave comprises the following specific steps:
in the formula (I), f g For the grid frequency, m is a modulation ratio, m is an element (0,1), and the modulation ratio m can be expressed by the formulaIs obtained by m Representing the amplitude, U, of the AC reference phase voltage dc The dc-side bus voltage is shown.
By combining the waveform diagram of the three-phase normalized sine wave signal in one period and the sector relation diagram in fig. 3, it can be obtained that the sine waves normalized by the phases A, B and C are respectively u ma ,u mb ,u mc Is u, the median value and the minimum value of max ,u mid ,u min . For example 2 pi f g When the sine wave is between 0 and pi/3, corresponding to the sector I, the A phase, the B phase and the C phase normalization sine wave u in the sector I ma ,u mb ,u mc In u ma Is a maximum value of u mb Is a median value of u mc Is the minimum value.
2. Determining zero sequence voltage u in load balancing z1
The three-phase vienna rectifier topology shown in fig. 1 when loadedA first resistor R 1 And a second resistor R 2 Are equal, i.e. R 1 =R 2 Representing load balance by time, and defining zero sequence voltage as u z1 U of the invention z1 The determination method comprises the following steps:
in the above formula, u z1 Representing the zero sequence voltage injected in load balancing; u. of max ,u mid ,u min A phase, B phase and C phase normalized sine wave u at a certain moment ma ,u mb ,u mc Maximum, median and minimum values of; min (-u) mid ,1-u max ) Expression to find-u mid And 1-u max Minimum value of (d): when-u mid ≤1-u max Hour, min (-u) mid ,1-u max )=-u mid When 1-u max <-u mid Hour, min (-u) mid ,1-u max )=1-u max ;max(-u mid ,-1-u min ) Expression to find-u mid And-1-u min Maximum value of (d): when-u mid ≥-1-u min Max (-u) mid ,-1-u min )=-u mid When 1-u min >-u mid Max (-u) mid ,-1-u min )=-1-u min 。
3. Obtaining three-phase modulated wave in load balance
Defining three-phase modulation waves of the Vienna rectifier after the zero-sequence component is injected into the three-phase modulation waves as u ref_x And x is a, b and c, and the method for obtaining the three-phase modulated wave in load balance comprises the following steps:
u ref_x =u mx +u z1 ,x=a,b and c (Ⅲ)
in the formula (III), u ref_x X ═ a, b, and c denotes the three-phase modulated wave of the wiener rectifier in load balance, u mx X ═ a, b, and c denotes a three-phase normalized sine wave, u z1 Representing the zero sequence voltage injected at load balance.
The three-phase vienna rectifier carrier intermittently modulates the clamping area in the first sector at load balancing as shown in fig. 4.
5. Determining zero sequence voltage u when load is unbalanced z2
FIG. 1 shows a three-phase Vienna rectifier topology when a load resistor R 1 ≠R 2 Representing load balance by time, and defining zero sequence voltage as u when load is unbalanced z2 U of the invention z2 The determination method comprises the following steps:
u z2 indicating zero sequence voltage, u, under load unbalance conditions or injection max ,u mid ,u min Phase A, phase B and phase C normalized sine wave u at a certain moment ma ,u mb ,u mc Maximum, median and minimum, U dc1 、U dc2 Respectively representing the upper side capacitor voltage and the lower side capacitor voltage, U, of the DC bus in FIG. 1 dc Represents the total DC side bus voltage, min (-u), in FIG. 1 mid ,2U dc1 /U dc -u max ) Represents obtaining-u mid And 2U dc1 /U dc -u max Minimum value of (d): when-u mid ≤2U dc1 /U dc -u max Hour, min (-u) mid ,1-u max )=-u mid When 2U is used dc1 /U dc -u max <-u mid Hour, min (-u) mid ,1-u max )=2U dc1 /U dc -u max ;max(-u mid ,-2U dc2 /U dc -u min ) Represents obtaining-u mid and-2U dc2 /U dc -u min Maximum value of (c): when-u mid ≥-2U dc2 /U dc -u min Max (-u) mid ,-1-u min )=-u mid When is-2U dc2 /U dc -u min >-u mid Max (-u) mid ,-1-u min )=-2U dc2 /U dc -u min 。
6. Obtaining three-phase modulated wave when load is unbalanced
Defining three-phase modulation waves of the Vienna rectifier after zero-sequence component injection as u respectively ref_x And x is a, b and c, and the method for obtaining the three-phase modulated wave when the load is unbalanced is as follows:
in the formula (V), u ref_x X ═ a, b, and c denotes a three-phase modulated wave of a wiener rectifier, u mx Where x is a, b, and c denotes a three-phase normalized sine wave, u z2 Indicating zero sequence voltage, U, under load unbalance conditions or injection dc1 、U dc2 Respectively representing the upper side capacitor voltage and the lower side capacitor voltage, U, of the DC bus in FIG. 1 dc The dc side bus total voltage in fig. 1 is shown.
When the load is unbalanced, the clamping area of the three-phase vienna rectifier carrier modulated intermittently in the first sector is shown in fig. 5, where fig. 5a represents R 1 <R 2 Clamping area of time, FIG. 5b shows R 1 >R 2 Clamping area of time.
According to the embodiment of the invention, a three-phase Vienna rectifier simulation model is built by means of PLECS software, and the effectiveness of the three-phase Vienna rectifier carrier intermittent modulation method is verified by means of simulation. Example simulation conditions were: the simulation step size is 3us, the effective value of the alternating voltage is 115V, the fundamental frequency is 400Hz, and the switching frequency of the switching tube is 100 kHz.
Fig. 6 is a simulation waveform diagram of the three-phase vienna rectifier carrier discontinuous modulation method in load balancing, wherein u is ma Is a-phase normalized sine wave, u, of a three-phase normalized sine wave z1 Is the zero sequence voltage, u, injected during load balancing ref_a Is a three-phase modulated wave in load balance, u a Is an AC side input voltage i a Is an input current of the AC side u AO Is the a phase leg voltage. A-P represents that the bridge arm voltage of the phase A is clamped to be P, A-O represents that the bridge arm voltage of the phase A is clamped to be 0, and A-N represents that the bridge arm of the phase AThe voltage is clamped to N. As can be seen from fig. 6a and 6b, when the inventive carrier intermittent modulation method is used in load balancing, under different modulation ratios, the modulation wave is clamped to 0 near the zero crossing of the current, which is consistent with the clamping area in fig. 4, and the quality of the current waveform is good, thereby verifying the effectiveness of the proposed carrier intermittent modulation method in load balancing. When the load resistors R in FIG. 1 are the same 1 =9Ω,R 2 =6Ω(R 1 >R 2 ) And R 1 =6Ω,R 2 =9Ω(R 1 <R 2 ) As can be seen from fig. 7a and 7b, when the load is unbalanced, the inventive carrier intermittent modulation method is adopted, the modulation wave is clamped to 0 near the zero crossing of the current, which is consistent with the clamping area in fig. 5a and 5b, and the quality of the current waveform is good, so that the effectiveness of the proposed carrier intermittent modulation method in the load imbalance is verified. Simulation shows that the three-phase Vienna rectifier carrier intermittent modulation method is simple in calculation and easy to realize.
The working principle and the working process of the invention are as follows:
obtaining the normalized sine waves of the phase voltage A, the phase voltage B and the phase voltage C which are respectively u phase voltage according to the three-phase normalization formula of the SPWM (sinusoidal pulse Width modulation) strategy of the three-phase Vienna rectifier ma ,u mb ,u mc (ii) a Defining the maximum value of three-phase normalized sine wave at a certain time as u max An intermediate value of u mid Minimum value of u min (ii) a The zero sequence voltage injected is u when the load is balanced z1 In u mid Time scale u is more than or equal to 0 z1 =max(-u mid ,-1-u min ) In u mid < 0 season u z1 =min(-u mid ,1-u max ) (ii) a When the load is unbalanced, the zero sequence voltage is injected into the load to be u z2 In u mid Time scale u is more than or equal to 0 z2 =max(-u mid ,-2U dc2 /U dc -u min ) In u mid < 0 season u z2 =min(-u mid ,2U dc1 /U dc -u max ) (ii) a And by applying a zero sequence voltage u z1 /u z2 And injecting a three-phase normalized sine wave to obtain a three-phase modulation wave of the three-phase Vienna rectifier. And a three-phase Vienna rectifier simulation model is built by means of PLECS softwareAnd verifying the effectiveness of the three-phase Vienna rectifier carrier intermittent modulation method by using simulation.
Claims (6)
1. The carrier intermittent modulation method of the three-phase Vienna rectifier is characterized in that a three-phase normalization formula of a SPWM (sinusoidal pulse Width modulation) strategy of the three-phase Vienna rectifier is used for obtaining a normalized sine wave of an A phase, a normalized sine wave of a B phase and a normalized sine wave of a C phase which are respectively u ma ,u mb ,u mc (ii) a Defining the maximum value of A-phase, B-phase and C-phase normalized sine waves at a certain moment as u max An intermediate value of u mid Minimum value of u min (ii) a When the load is balanced, the zero sequence voltage is injected to be u z1 The modulation method of the invention is in mid Time scale u is more than or equal to 0 z1 =max(-u mid ,-1-u min ) In u mid < 0 season u z1 =min(-u mid ,1-u max ) (ii) a When the load is unbalanced, the injected zero sequence voltage is u z2 The modulation method of the invention is in mid Time scale u is more than or equal to 0 z2 =max(-u mid ,-2U dc2 /U dc -u min ) In u mid < 0 season u z2 =min(-u mid ,2U dc1 /U dc -u max ) (ii) a And by applying a zero sequence voltage u z1 /u z2 And injecting a three-phase normalized sine wave to obtain a three-phase modulation wave of the Vienna rectifier.
2. The method as claimed in claim 1, wherein the a-phase voltage normalized sine wave u is obtained from a three-phase normalization formula of a three-phase vienna rectifier SPWM modulation strategy ma B-phase voltage normalization sine wave u mb C-phase voltage normalization sine wave u mc And obtaining the maximum value u of the normalized three-phase sine wave max Middle value u mid Minimum value u min The specific method comprises the following steps:
obtaining the A-phase voltage normalization sine wave u according to the three-phase normalization formula ma B-phase voltage normalization sine wave u mb C-phase voltage normalized sine wave u mc Is normalizedThe formula is as follows:
in the formula, f g For the grid frequency, m is the modulation ratio, m is the (0,1), and the modulation ratio m can be expressed by the formulaIs obtained by m Representing the amplitude, U, of the AC reference phase voltage dc Expressing the voltage of a direct current side bus to obtain a normalized sine wave u of phase voltage A, phase voltage B and phase voltage C at a certain moment ma ,u mb ,u mc Respectively is u max 、u mid 、u min 。
3. Method for the discontinuous modulation of the carrier of a three-phase vienna rectifier according to claim 1, characterised in that said zero sequence voltage u z1 The determination method of (2) is as follows:
in the above formula, u z1 Representing the zero sequence voltage injected in load balancing; u. of max ,u mid ,u min A-phase, B-phase and C-phase normalized sine wave u at a certain moment ma ,u mb ,u mc Maximum, median and minimum values of; min (-u) mid ,1-u max ) Represents obtaining-u mid And 1-u max Minimum value of (d): when-u mid ≤1-u max Hour, min (-u) mid ,1-u max )=-u mid When 1-u is max <-u mid Hour, min (-u) mid ,1-u max )=1-u max ;max(-u mid ,-1-u min ) Represents obtaining-u mid And-1-u min Maximum value of (d): when-u mid ≥-1-u min Max (-u) mid ,-1-u min )=-u mid When 1-u min >-u mid Max (-u) mid ,-1-u min )=-1-u min 。
4. The method according to claim 1, wherein the three-phase modulation waves of the vienna rectifier after the zero-sequence component is injected are defined as u, respectively ref_x X ═ a, b, and c, the calculation method is as follows:
u ref_x =u mx +u z1 ,x=a,b and c (Ⅲ)
in the above formula, u ref_x X ═ a, b, and c denote three-phase modulated waves of a vienna rectifier, u mx Represents a three-phase normalized sine wave, u z1 Representing the zero sequence voltage injected at load balance.
6. the method according to claim 1, wherein the three-phase modulation waves of the vienna rectifier after the zero-sequence component is injected are defined as u, respectively ref_x X ═ a, b, and c, the calculation method is as follows:
in the above formula, u ref_x X ═ a, b, and c denotes a three-phase modulated wave of a wiener rectifier, u mx X ═ a, b, and c denotes a three-phase normalized sine wave, u z2 Indicating load unbalance conditions or injectionZero sequence voltage of (U) dc1 、U dc2 Respectively representing the upper and lower capacitor voltages, U, of the DC-side bus dc Representing the total dc side bus voltage.
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