CN102761284B - Accuracy control method for single-phase diode clamping three level midpoint potential imbalance - Google Patents
Accuracy control method for single-phase diode clamping three level midpoint potential imbalance Download PDFInfo
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Abstract
The invention provides an accuracy control method for single-phase diode clamping three level midpoint potential imbalance, which specially aims at the accuracy control of the midpoint potential imbalance by analyzing the influence of the zero level to the direct current-side midpoint potential, and changing the distribution of the zero level among different bridge arms due to the symmetry and the redundancy under the condition that the outlet voltage wave form is not changed and the direct current component is not led, wherein the control method is only relevant to the modulating wave of each module, and is suitable for a large-scale cascade diode clamping topological structure. According to the method, the modulating wave of each module is divided into two parts, the two modulating waves are equal in size and reversed in directions and respectively control the left half bridge and the right half bridge of the diode clamping, and the required direct current component is injected into the modulating wave as required, so that the accuracy control of the midpoint potential can be formed, and additional auxiliary devices are not needed, therefore, the method is simple and easy. The simulation and experiment results show the exactness and the reliability of the method, so that a good reference value can be provided for the engineering application.
Description
Technical field
The invention belongs to field of power electronics, be specifically related to the uneven accuracy control method of a kind of single-phase diode clamper three level midpoint potentials.
Background technology
The thought of multi-level converter is proposed the beginning of the eighties by people such as Nabae the earliest.Its general structure is to approach sine output voltage by the synthetic staircase waveform of several level steps.Voltage with multiple levels code converter is compared with two traditional level converters, can produce M ladder output voltage, and the output voltage degree of freedom is many, is more suitable in coupling voltage levels; Switch element one-off dv/dt only has 1/ (M-1) of traditional double level conventionally, and electromagnetic interference (EMI) problem alleviates greatly; In order to eliminate same harmonic wave, the PWM control method switching frequency of two level employings is high, loss is large, and multi-electrical level inverter can carry out switch motion with lower frequency, switching frequency is low, loss is little, and efficiency improves.Due to above advantage, multi-level converter is at high voltage, and high-power aspect obtains applying more and more widely
[1-4].Multi-level converter can be divided into the topological structures such as diode clamp type multi-level converter, leap capacitor type multi-level converter and cascade multilevel converter.Compare with other two kinds of multi-level converters, diode clamp type multi-level converter is owing to can saving the number of high-voltage capacitance, and do not need independent DC power supply, and therefore at high voltage, the application in high-power field is more extensive.In all many level topologys, three-level NPC inverter is the topological structure of current application and most study.
When many level of Cascade H bridge structure applications is in 10KV, during the large capacity static state reactive generator of 35KV, every a lot of H bridge modules that need mutually to connect, control quite complicated.Single-phase diode clamper three level modules when adopting identity unit, withstand voltage can doubling than H bridge module.If the H bridge module of chain type static state reactive generator changes single-phase diode clamper three level modules into, number of modules can reduce half, and structure and control are simplified.In addition single-phase diode clamper three level topologys are also widely used in the commercial Application such as photovoltaic generation and high power switching power supply.But inconsistent due to switching device and DC bus capacitor characteristic, and the existence of disturbance, also have the difference of modulation system all likely to cause the fluctuation of midpoint potential.There is Neutral-point Potential Fluctuation and this intrinsic problem of skew in diode clamp topology.How to eliminate the fluctuation of midpoint potential, realize the balance of midpoint potential and control, be the focus that people study always, and have some relevant bibliographical informations
[5-15].From above-mentioned document, can find out, three-phase diode clamper three level topologys midpoint potential balances are controlled the research by extensively and profoundly.But seldom there is the midpoint potential balance of literature research single-phase diode clamper three-level converter to control.
Document [5] adopts the different conditions at switch to come alignment electric charge to discharge and recharge to reach the balance of mid point according to the sense of current, this method is controlled well at current potential that can alignment, but because the quantity of electric charge injecting under each on off state is uncertain, the size of the quantity of electric charge injecting can not accurately be controlled, and causes the fluctuation of midpoint potential.Bangbang controls
[6-7]action effect by the Redundanter schalter state alignment current potential that exists reaches inhibition Neutral-point Potential Fluctuation on the contrary, this control method is simple and can control well the fluctuation of midpoint potential, but this control is owing to can not accurately controlling the quantity of electric charge that injects mid point, midpoint potential is in very large range fluctuateed, and its control mechanism is identical with document [5] in essence.Document [8] reaches the control of alignment current potential by increasing ancillary hardware unit, this control method realizes simple, but has additionally increased cost.Modulator approach based on space vector
[9-15], reach good adjusting mid point the action time by small vector in regulating fluctuates, and controls effect fine, but due to the complexity of space vector modulation, is difficult to it to be applied in the middle of cascade connection multi-level.Document [16-17] is based on proposing in three-phase system when adopting carrier modulation, by adding residual voltage to control the fluctuation of midpoint potential, the injection of residual voltage not only can suppress midpoint potential fluctuation, and can improve DC side utilance.If but this thought is applied in uniterm system, will in mutually, introduce direct current interference volume, must try every possible means to remove this interference volume.What the Accurate Analysis of document [18-20] by three-phase system found can alignment potential balance to work is even-order harmonic, therefore by building corresponding load in load-side or injecting corresponding even-order harmonic and eliminate mid point imbalance in modulating wave, still implement very complicated.
A kind of control method based on passing through to inject DC component has been proposed herein, labor the working mechanism of single-phase diode clamper three level, by zero level is analyzed the impact of DC side midpoint potential, in the situation that not changing outlet voltage waveform and not introducing DC component, the distribution that utilizes redundancy to change the zero level between different brachium pontis reaches the unbalanced accurate control of alignment current potential
[21-25].
Below provide the pertinent literature of retrieval
[1] Li Yongdong, Gao Yue, waits pavilion. large capacity PWM Control Technology in Multilevel Converters present situation and progress. and power electronic technology [J] .2005,39 (5): 2-6.
[2]Akira?Nabae，Isao?Takahashi，Hirofumi?Akagi.A?new?neutral-point?clamped?PWM?inverter[J].IEEE?Trans.On?Industry?Application，1981，17(5)：518-523.
[3] Liu Fengjun writes. multi-level inverse conversion technology and application thereof [M]. and Beijing: China Machine Press, 2007.1.
[4] Li Yongdong, waits and writes. large capacity multi-level converter: principle is controlled application [M]. and Beijing: Science Press, 2005.10.
[5] Yan Shichao, Tang Qingquan, Liu Zhengzhi. the analysis [J] of DC capacitor voltage during half-bridge three-level inverter output asymmetrical alternating current, electrician's electric energy new technology, 2007,26 (2): 50-52.
[6] fourth is triumphant. hybrid multilevel inverter topology and modulator approach research thereof, doctor's scientific paper, 2004.
[7] permitted Yun, Zou Yunping, Liu Xiong, etc. the research of Single-phase Three-level PWM Rectifier Double Loop Control System, power electronic technology, 2008,42 (9).
[8]Annette?von?Jouanne，Shaoan?Dai，et?al.A?Multilevel?inverter?Approach?Providing?DC-Link?Balancing，Ride-Through?Enhancement，and?common-Mode?Voltage?Elimination[J]IEEE?Trans?on?power?Electronics，，2002，49(4)：740-745.
[9] Song Wenxiang, Chen Guochen. the research [J] of three level Neutral-point-clamped inverter SVPWM methods.Electrician's electric energy new technology, 2004,23 (4): 30-33.
[10] Zhan Changjiang, Han Yu, etc. the novel three level high-frequency rectifier researchs [J] based on space vector of voltage PWM pulse width modulation mode. electrotechnics journal, 1999,, 14 (2) .:60-64.
[11] Jin Shun, Zhong Yanru. a kind of three-level pwm method [J] of controlling midpoint potential and eliminating burst pulse. Proceedings of the CSEE, 2003,23 (10): 114-118.
[12] woods is of heap of stone, Zhou Yunping, etc. diode clamping three-level inverter control system research [J]. Proceedings of the CSEE, 2005,25 (15): 33-39.
[13]Cleanovic?N，Boroyevich?D.A?comprehensive?study?of?neutral-point?voltage?balancing?problem?in?three-level?neural-point-clamped?voltage?source?PWM?inverter[J]IEEE?Trans?on?power?Electronics，，2000，15(3)：242-249..
[14] Song Wenxiang, Chen Guocheng, Wu Hui, etc. a kind of 3 level space vector modulator approach and realization [J] thereof with midpoint potential equilibrium function, Proceedings of the CSEE, 2006,26 (12): 96-100.
[15] Shi Xiaofeng. diode-clamped multi-electrical level inverter capacitance voltage equilibrium problem research [D]. master thesis, 2009.
[16] Wang Guangzhu. the research [J] of the uneven base reason of diode clamping formula multi-electrical level inverter DC capacitor voltage, Proceedings of the CSEE, 2002,22 (12): 111-117.
[17] Meng Yongqing, Shen Chuanwen, etc. the research [J] of the three level neutral point clamp rectifier midpoint potential control methods of injecting based on residual voltage, Proceedings of the CSEE, 2007,27 (10): 93-96.
[18]H.duT.Mouton.Natural?balancing?of?Th?ree-Level?neutral?point?clamped?PWM?Inverters[J]..IEEE?Trans?onindustrial.Electronics.，2002，49(5).1017-1025.
[19]Mohzani，Z.；McGrath，B.P.；Holmes，D.G..Natural?Balancing?of?the?Neutral?Point?Voltage?for?a?Three-Phase?NPC?Multilevel?Converter[J]IEEE?Industral?Electronics?Society，2011，：4445-4450.
[20]Jie?shen，Stefan?Schroder.A?Comprehensive?Study?of?Netural-Point?Self-Balancing?Effect?in?Neutral-Point-clamped?Three-Level?Inverter[J]IEEE?Transactions?on?power?Electronics，2011，11(26)：3084-3095.
[21] Zhang Chongwei, emerging .PWM rectifier and control [M] thereof. Beijing: the .2003 of China Machine Press
[22]Fei?Wang，Rixin?Lai，et?al.Failure-Mode?Analysis?and?Protection?of?Three-Level?Netural-Point-Clamped?PWM?Voltage?Source?Converters[J]IEEE?Trans?on?power?Electronics，，2010，46(2)：866-874.
[23]B.-R.Lin，D.-J.Chen.Single-phase?neutral?point?clamped?AC/DC?converter?with?the?function?of?power?factor?corrector?and?active?filter[J]IEEE?Trans?on?power?Electronics，，2002，149(1)：19-30.
[24] Wang little Feng, Deng Yan, He Xiangning. the single-carrier modulated of three-phase tri-level diode-clamped rectifier and neutral balance control strategy research [J]. Proceedings of the CSEE; 2006,26 (8).
[25] Wang Zhaoan, Liu Jinjun. power electronic technology the 5th edition [M]. Beijing: China Machine Press, 2010.
Summary of the invention
The present invention proposes the unbalanced accuracy control method of a kind of single-phase diode clamper three level midpoint potential, be exactly by zero level is analyzed the impact of DC side midpoint potential specifically, in the situation that not changing outlet voltage waveform and not introducing DC component, the distribution that utilizes symmetry and redundancy to change the zero level between different brachium pontis reaches the unbalanced accurate control of alignment current potential, and this control method is only relevant with the modulating wave of each module, is adapted to extensive cascade diode clamper topological structure.In order to achieve the above object, the present invention is by the following technical solutions:
Comprise the following steps:
The DC voltage control that step 1 is total
Step 1.1, detects all diode clamp topology unit module DC voltage u of single-phase cascade diode clamper topology grid-connected converter
dc_i(i=1,2...N), the upper and lower capacitance voltage u of each diode clamp topology DC side
dc_iP, u
dc_in(i=1,2...N) and compensator output current I, obtain all DC voltages and u
sumand mean value u
ave.
Step 1.2, by all module DC voltages and with total DC voltage set-point u
refafter single channel subtracter subtracts each other again through ratio scaling, and the cosine amount cos ω t of the result after ratio scaling and the phase-locked standard fundamental positive sequence value obtaining of line voltage is multiplied each other through multiplier, after being added, the result of multiplier output and offset current set-point adjust through single channel proportional and integral controller, the sinusoidal quantity sin ω t of the phase-locked standard fundamental positive sequence value obtaining of the output valve of single channel proportional integral device and line voltage multiply each other (the phase-locked location of line voltage sinwt), obtain the fundamental active current instruction Δ i that cascade diode clamper topology grid-connected converter regulates for total DC voltage
p.
Step 1.3, the fundamental active current instruction Δ i that step 1.2 is obtained
pwith feedback current i
cthrough single channel subtracter, subtract each other, its output is adjusted through single channel proportional and integral controller, and the output valve of single channel proportional integral device is as total modulating wave command voltage u of this loop
diode.
The Pressure and Control of each diode clamp three level intermodule of step 2
Step 2.1, by the mean value u of diode clamp unit module DC voltage
a_avewith with each unit module DC voltage set-point u
refthrough single channel subtracter, compare, its output is adjusted through single channel proportional and integral controller, the actual current i of the output valve of single channel proportional integral device and current transformer output
bmultiply each other, obtain the fine setting command voltage Δ u regulating for modules DC voltage in grid-connected converter
diode_1.
Step 2.2, according to step 2.1 requirement, obtains respectively cascade connection multi-level second to the fine setting command voltage Δ u of N-1 diode clamp topology modules voltage-regulation
diode_2... Δ u
diode_ (N-1).
Step 2.3, by total modulating wave command voltage u
diodethe fine setting command voltage Δ u of the modules obtaining with step 2.2
diode_1, Δ u
diode_2... Δ u
diode_Nafter addition as the PWM modulating wave instruction u of each module
diode_1... u
diode_N(after normalization).
The command voltage of step 3 based on midpoint potential unbalance control forms
Step 3.1 remains unchanged in order to guarantee the output waveform of current transformer outlet, adopts the modulation system of two symmetric modulation ripples to carry out the unbalanced control of mid point here, the PWM modulating wave instruction u of the modules forming for step 2.3
diode_1... u
diode_N, before carrying out PWM modulation it respectively divided by 2,
as the instruction of the left half-bridge modulating wave of each diode clamp module,
as the instruction of the right half-bridge modulating wave of each diode clamp module.
Step 3.2, can alignment current potential generation effect be the time of zero level effect, as long as accurate, control the time size of our needed zero levels within each primitive period, the imbalance of DC side midpoint potential just can be well controlled, and by adding DC quantity just can change the time of zero level effect in modulating wave.According to the direction of each diode clamp module left half-bridge modulating wave instruction and compensator output current I, be divided into four intervals and calculate respectively the DC component size adding in modulating wave.
When
Time, the DC component size that left half-bridge modulating wave instruction is injected is x=(1-Msin ω t)
When
Time, the DC component size that left half-bridge modulating wave instruction is injected is x=-(1-Msin ω t)
When
Time, the DC component size that left half-bridge modulating wave instruction is injected is x=(1-Msin ω t)
When
Time, the DC component size that left half-bridge modulating wave instruction is injected is x=-(1-Msin ω t)
Step 3.3, the value of the DC component x obtaining according to step 3.2, in order to guarantee that total current transformer outlet waveform remains unchanged, must inject identical DC component x in the instruction of right half-bridge modulating wave, and each total module modulating wave instruction u
diode_i=S
diode_ai+ x-(S
diode_bi+ x)=S
diode_ai-S
diode_biremain unchanged.
Step 3.4, according to step 3.2, obtain add DC component little after the final modulating wave command voltage of each module left and right half-bridge S
diode_ai± x (S
diode_bi± x) carry out PWM modulation with phase shift triangular wave, the switching signal that generates each module removes to drive converter module.
Above-mentioned steps can three control rings, and wherein step 1 is first control ring, and step 2 is second control ring, and step 2 is the 3rd control ring.
The present invention is divided into two by each module ground modulating wave, this two modulating wave opposite sign but equal magnitude and control respectively diode clamp left and right half-bridge, in modulating wave, inject as required the accurate control of needed DC component formation alignment current potential, without extra servicing unit, method is simple.From simulation result, can see, the present invention can realize well for the balance of diode clamp DC side mid-point voltage and controlling.In laboratory, built capacity is 5kVA simultaneously, the small test model machine of a single-phase diode clamp, method in the present invention has been carried out to experimental verification, and emulation and experimental result have all proved correct, the reliability of the method, for engineering application provides good reference value.
Accompanying drawing explanation
Fig. 1 diode clamp three level grid-connected converter main circuit structures;
The control system block diagram that Fig. 2 diode clamp three level grid-connected converters are total;
Midpoint potential balance accuracy-control system block diagram in Fig. 3 the present invention;
The simulation waveform of upper and lower two capacitance voltages of diode clamp three level grid-connected converter DC bus when Fig. 4 (a) does not add Fig. 3 control ring;
The simulation waveform of the grid-connected DC side midpoint potential of diode clamp three level when Fig. 4 (b) does not add Fig. 3 control ring;
The simulation waveform of upper and lower two capacitance voltages of diode clamp three level grid-connected converter DC bus when Fig. 5 (a) adds Fig. 3 control ring;
The simulation waveform of the grid-connected DC side midpoint potential of diode clamp three level when Fig. 5 (b) adds Fig. 3 control ring;
Feasibility and validity experimental waveform that the mid-point voltage that Fig. 6 the present invention proposes in perceptual situation is controlled.
Feasibility and validity experimental waveform that the mid-point voltage that Fig. 7 the present invention proposes in capacitive situation is controlled.
Feasibility and validity experimental waveform that the mid-point voltage that Fig. 8 the present invention proposes from 11A-18A (peak-to-peak value) sudden change situation at perceptual situation power network current is controlled.
Feasibility and validity experimental waveform that the mid-point voltage that Fig. 9 the present invention proposes from 8A-12A (peak-to-peak value) sudden change situation at capacitive situation power network current is controlled.
Feasibility and validity experimental waveform that the mid-point voltage that Figure 10 the present invention proposes from capacitive to perception sudden change situation is controlled.
Feasibility and validity experimental waveform that the mid-point voltage proposing in Figure 11 DC side shock load of the present invention situation is controlled.Figure 12 is the partial enlarged drawing of Figure 10.
Embodiment
With reference to Fig. 1, between electrical network and load, connect diode clamp topology three level grid-connected converters, this grid-connected converter is done reactive-load compensator operation, in order better to verify the control effect of this control method alignment, at the C of DC side
1end has added very little resistance R
1simulate its very lossy, so can use very large active component in experiment electric current.The main circuit structure of many level of diode clamp grid-connected converter, mainly comprises: 1 diode clamp topography module, 1 inlet wire inductance, load-side.Each diode clamp topography module is comprised of two DC side storage capacitor elements and voltage-source type PWM current transformer, wherein DC side energy-storage travelling wave tube generally consists of power capacitor connection in series-parallel, and voltage-source type pwm converter adopts full control device as compositions such as IGBT, GTO.
Inlet wire inductance one end is connected on diode clamp topography module, and an end is connected between electrical network and load, and the selection of its parameter depends primarily on the switching frequency of diode clamp topography module.
In order to narrate conveniently, in the present invention, the module of take is elaborated as example.Line voltage is designated as V
g, power network current is designated as i
g, load current is designated as i
l; Left half-bridge Injection Current is designated as i
a, right half-bridge Injection Current is designated as i
b, the total output current of current transformer is designated as i
c; Diode clamp topology grid-connected converter DC voltage u
dc_pn, the upper and lower capacitance voltage u of diode clamp topology DC side
dc_P, u
dc_n.
With reference to Fig. 2, Fig. 3, many level of diode clamp grid-connected converter direct current bus voltage control method in the present invention and the control method of DC side midpoint potential balance, it is characterized in that three control rings in above-mentioned steps, wherein step 1 is first control ring, object is from electrical network, to absorb active current by controlling whole many level of series diode clamper grid-connected converter, the loss producing to offset whole grid-connected converter; Step 2 is each module DC bus-bar voltage Pressure and Control ring, object is to finely tune the distribution instruction voltage of high-low pressure module, redistribute the active power that modules absorbs, make the active power of this module actual absorption just can offset the loss of this module self, and then make the stable operation under specified command voltage value of high-low pressure module; Step 3 is for calculating the DC component size control ring add, and object is that the zero level ON time size that can exert an influence according to alignment current potential determines the value of the DC component adding at different time, guarantees the accurate control of alignment current potential.
Concrete steps are as follows:
The DC voltage control that step 1 is total
Step 1.1, detects all diode clamp topology unit module DC voltage u of single-phase cascade diode clamper topology grid-connected converter
dc_i(i=1,2...N), the upper and lower capacitance voltage u of each diode clamp topology DC side
dc_iP, u
dc_in(i=1,2...N) and compensator output current I, obtain all DC voltages and u
sumand mean value u
ave.
Step 1.2, by all module DC voltages and with total DC voltage set-point u
refafter single channel subtracter subtracts each other again through ratio scaling, and the cosine amount cos ω t of the result after ratio scaling and the phase-locked standard fundamental positive sequence value obtaining of line voltage is multiplied each other through multiplier, after being added, the result of multiplier output and offset current set-point adjust through single channel proportional and integral controller, the sinusoidal quantity sin ω t of the phase-locked standard fundamental positive sequence value obtaining of the output valve of single channel proportional integral device and line voltage multiply each other (the phase-locked location of line voltage sinwt), obtain the fundamental active current instruction Δ i that cascade diode clamper topology grid-connected converter regulates for total DC voltage
p.
Step 1.3, the fundamental active current instruction Δ i that step 1.2 is obtained
pwith feedback current i
cthrough single channel subtracter, subtract each other, its output is adjusted through single channel proportional and integral controller, and the output valve of single channel proportional integral device is as total modulating wave command voltage u of this loop
diode.
The Pressure and Control of each diode clamp three level intermodule of step 2
Step 2.1, by the mean value u of diode clamp unit module DC voltage
a_avewith with each unit module DC voltage set-point u
refthrough single channel subtracter, compare, its output is adjusted through single channel proportional and integral controller, the actual current i of the output valve of single channel proportional integral device and current transformer output
bmultiply each other, obtain the fine setting command voltage Δ u regulating for modules DC voltage in grid-connected converter
diode_1.
Step 2.2, according to step 2.1 requirement, obtains respectively cascade connection multi-level second to the fine setting command voltage Δ u of N-1 diode clamp topology modules voltage-regulation
diode_2... Δ u
diode_ (N-1).
Step 2.3, by total modulating wave command voltage u
diodethe fine setting command voltage Δ u of the modules obtaining with step 2.2
diode_1, Δ u
diode_2... Δ u
diode_Nafter addition as the PWM modulating wave instruction u of each module
diode_1... u
diode_N(after normalization).
The command voltage of step 3 based on midpoint potential unbalance control forms
Step 3.1 remains unchanged in order to guarantee the output waveform of current transformer outlet, adopts the modulation system of two symmetric modulation ripples to carry out the unbalanced control of mid point here, the PWM modulating wave instruction u of the modules forming for step 2.3
diode_1... u
diode_N, before carrying out PWM modulation it respectively divided by 2,
as the instruction of the left half-bridge modulating wave of each diode clamp module,
as the instruction of the right half-bridge modulating wave of each diode clamp module.
Step 3.2, can alignment current potential generation effect be the time of zero level effect, as long as accurate, control the time size of our needed zero levels within each primitive period, the imbalance of DC side midpoint potential just can be well controlled, and by adding DC quantity just can change the time of zero level effect in modulating wave.According to the direction of each diode clamp module left half-bridge modulating wave instruction and compensator output current I, be divided into four intervals and calculate respectively the DC component size adding in modulating wave.
When
Time, the DC component size that left half-bridge modulating wave instruction is injected is x=(1-Msin ω t)
When
Time, the DC component size that left half-bridge modulating wave instruction is injected is x=-(1-Msin ω t)
When
Time, the DC component size that left half-bridge modulating wave instruction is injected is x=(1-Msin ω t)
When
Time, the DC component size that left half-bridge modulating wave instruction is injected is x=-(1-Msin ω t)
Step 3.3, the value of the DC component x obtaining according to step 3.2, in order to guarantee that total current transformer outlet waveform remains unchanged, must inject identical DC component x in the instruction of right half-bridge modulating wave, and each total module modulating wave instruction u
diode_i=S
diode_ai+ x-(S
diode_bi+ x)=S
diode_ai-S
diode_biremain unchanged.
Step 3.4, according to step 3.2, obtain add DC component little after the final modulating wave command voltage of each module left and right half-bridge S
diode_ai± x (S
diode_bi± x) carry out PWM modulation with phase shift triangular wave, the switching signal that generates each module removes to drive converter module.
Fig. 4,5 has provided the simulation waveform that adopts control method in the present invention, the simulation waveform of DC voltage while not adding control ring respectively, while having added control ring.From simulation waveform, can find out that this control method can well control the imbalance of DC side mid point.
Fig. 6-12 have provided the experimental waveform that adopts control method in the present invention on the experimental prototype of building in laboratory.In Fig. 6, each passage is expressed as: CH1: line voltage (100V/div); CH2: DC capacitor voltage 1 (20V/div); CH3: DC capacitor voltage 2 (20V/div); CH4: power network current (8A/div).In Fig. 7, each passage is expressed as: CH1: line voltage (100V/div); CH2: DC capacitor voltage 1 (20V/div); CH3: DC capacitor voltage 2 (20V/div); CH4: power network current (8A/div).In Fig. 8, each passage is expressed as: CH1: line voltage (100V/div); CH2: DC capacitor voltage 1 (20V/div); CH3: DC capacitor voltage 2 (20V/div); CH4: power network current (8A/div).In Fig. 9, each passage is expressed as: CH1: line voltage (100V/div); CH2: DC capacitor voltage 1 (20V/div); CH3: DC capacitor voltage 2 (20V/div); CH4: power network current (8A/div).In Figure 10, each passage is expressed as: CH1: line voltage (100V/div); CH2: DC capacitor voltage 1 (20V/div); CH3: current transformer port voltage (100V/div); CH4: power network current (8A/div).In Figure 11, each passage is expressed as: CH1: line voltage (100V/div); CH2: DC capacitor voltage 1 (20V/div); CH3: DC capacitor voltage 2 (20V/div); CH4: power network current (5A/div).Figure 12 is the partial enlarged drawing of Figure 10.When DC side load changing, DC voltage can produce fluctuation, but midpoint potential keeps balance always.
From experimental waveform, can find out that this control method can well control the imbalance of DC side mid point.
The result of invention
In the present invention, provide single-phase diode clamper midpoint potential imbalance and carried out the control method of accurately controlling.And utilize the simulink module in MATLAB to carry out simulating, verifying to this control method, in laboratory, built capacity is 5kVA simultaneously, the small test model machine of a single-phase diode clamp topology, method in the present invention has been carried out to experimental verification, emulation and experimental result have all proved and can carry out accurate balance control to diode clamp topology DC side imbalance, the method is correct, reliable, for the application of diode clamp topological structure on Practical Project provides good reference value.
Claims (3)
1. uneven accuracy control methods of single-phase symmetrical diode clamp three level midpoint potentials, current transformer is wherein connected in parallel between electrical network and load, current transformer is comprised of the diode clamp three level grid-connected converter modules of N cascade, it is characterized in that, comprises the following steps:
Step 1: total DC voltage control
Step 1.1, detects each converter module DC voltage u
dc_i, i=1,2...N, the upper and lower capacitance voltage u of each DC side
dc_iP, u
dc_in(i=1,2...N) and compensator output current I, obtain all DC voltages and u
sumand mean value u
ave;
Step 1.2, by all module DC voltages and with total DC voltage set-point u
refafter single channel subtracter subtracts each other again through ratio scaling, and the cosine amount cos ω t of the result after ratio scaling and the phase-locked standard fundamental positive sequence value obtaining of line voltage is multiplied each other through multiplier, after being added, the result of multiplier output and offset current set-point adjust through single channel proportional and integral controller, the sinusoidal quantity sin ω t of the phase-locked standard fundamental positive sequence value obtaining of the output valve of single channel proportional integral device and line voltage multiplies each other, and obtains the fundamental active current instruction Δ i that cascade diode clamper three level grid-connected converters regulate for total DC voltage
p;
Step 1.3, the fundamental active current instruction Δ i that step 1.2 is obtained
pwith feedback current i
cafter single channel subtracter subtracts each other, its output is adjusted through single channel proportional and integral controller, and the output valve of single channel proportional and integral controller is as total modulating wave command voltage u
diode;
The Pressure and Control of each diode clamp three level grid-connected converter intermodule of step 2
Step 2.1, by the mean value u of each module DC voltage
a_avewith with each module DC voltage set-point u
refthrough single channel subtracter, compare, its output is adjusted through single channel proportional and integral controller, the actual current i of the output valve of single channel proportional and integral controller and current transformer output
bmultiply each other, obtain the fine setting command voltage Δ u regulating for each current transformer DC voltage
diode_1;
Step 2.2, according to step 2.1 requirement, obtains respectively cascade second to the fine setting command voltage Δ u of N-1 module
diode_2... Δ u
diode_ (N-1);
Step 2.3, by total modulating wave command voltage u
diodethe fine setting command voltage Δ u of the modules obtaining with step 2.2
diode_1, Δ u
diode_2... Δ u
diode_Nafter addition as the PWM modulating wave instruction u of each module
diode1... u
diode_N;
The command voltage of step 3 based on midpoint potential unbalance control forms
Step 3.1 remains unchanged in order to guarantee the output waveform of current transformer outlet, adopts the modulation system of two symmetric modulation ripples to carry out the unbalanced control of mid point here, the PWM modulating wave instruction u of the modules forming for step 2.3
diode_1... u
diode_N, before carrying out PWM modulation it respectively divided by 2,
as the instruction of the left half-bridge modulating wave of each module,
as the instruction of the right half-bridge modulating wave of each module;
Step 3.2 adds DC quantity to change the time of zero level effect in modulating wave, is divided into four intervals calculates respectively the DC component size adding in modulating wave according to the direction of the left half-bridge modulating wave instruction of each module and compensator output current I:
When
Time, the DC component size that left half-bridge modulating wave instruction is injected is x=(1-Msin ω t);
When
Time, the DC component size that left half-bridge modulating wave instruction is injected is x=-(1-Msin ω t);
When
Time, the DC component size that left half-bridge modulating wave instruction is injected is x=(1-Msin ω t);
When
Time, the DC component size that left half-bridge modulating wave instruction is injected is x=-(1-Msin ω t);
Step 3.3, the value of the DC component x obtaining according to step 3.2, makes right half-bridge modulating wave instruction component also equal x and remains unchanged to guarantee converter module outlet waveform; And each total module modulating wave instruction u
diode_i=S
diode_ai+ x-(S
diode_bi+ x)=S
diode_ai-S
diode_biremain unchanged;
Step 3.4, what according to step 3.2, obtain adds the final modulating wave command voltage of each the module left and right half-bridge S after DC component
diode_ai± x (S
diode_bi± x) carry out PWM modulation with phase shift triangular wave, the switching signal that generates each module removes to drive converter module.
2. method according to claim 1, is characterized in that: described in be cascaded as serial or parallel connection.
3. method according to claim 1, is characterized in that: the sin ω t in described step 1.2 obtains by phase-locked loop.
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| CN105406746B (en) * | 2014-09-16 | 2018-08-14 | 上海三菱电梯有限公司 | Three level power converter neutral-point potential balance control methods |
| CN104779821A (en) * | 2015-03-26 | 2015-07-15 | 西南交通大学 | Space vector modulation method for diode-clamping type three-level pulse rectifier with reverse vector |
| CN104967342B (en) * | 2015-06-03 | 2017-08-01 | 厦门理工学院 | The midpoint potential forecast Control Algorithm of diode-clamped three-level converter |
| CN105450076A (en) * | 2015-09-15 | 2016-03-30 | 珠海格力电器股份有限公司 | Z-source three-level inverter and air conditioning system |
| CN106208775B (en) * | 2016-08-29 | 2019-06-11 | 东北电力大学 | Half period three-phase T-type three-level current transformer capacitor neutral-point voltage balance method |
| CN109713925B (en) * | 2019-01-11 | 2020-04-17 | 闽南理工学院 | DC side voltage-sharing control method of three-phase four-wire three-level inverter |
| CN111327215B (en) * | 2020-03-09 | 2021-03-16 | 西南交通大学 | Method for optimizing and controlling network side current of single-phase rectifier |
| CN111711353B (en) * | 2020-06-17 | 2023-06-20 | 中国国家铁路集团有限公司 | Reactive component detection method, control method and device of single-phase rectifier |
| CN112187079B (en) * | 2020-10-14 | 2021-08-06 | 河南科技大学 | Single-phase three-level converter system and control method thereof |
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