CN107196542B - A kind of selective harmonic elimination pulsewidth modulation becomes mode control method and its device - Google Patents
A kind of selective harmonic elimination pulsewidth modulation becomes mode control method and its device Download PDFInfo
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- CN107196542B CN107196542B CN201710417646.3A CN201710417646A CN107196542B CN 107196542 B CN107196542 B CN 107196542B CN 201710417646 A CN201710417646 A CN 201710417646A CN 107196542 B CN107196542 B CN 107196542B
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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
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
- H02M7/487—Neutral point clamped inverters
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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
Abstract
The invention discloses a kind of selective harmonic elimination pulsewidth modulations to become mode control method and its device, is used for NPC Multilevel Inverters, is included under power grid network pressure imbalance operating condition, calculates current voltage modulation ratio m and phase angle；Voltage modulated ratio is compared with default modulation ratio threshold value, if being less than default modulation ratio threshold value, the first control model is selected, if more than default modulation ratio threshold value, then selects the second control model；It is 0 that first control model, which is used to control the output current balance type of current transformer and whole odd harmonics, and the second control model is positive integer for controlling ± 1 subharmonic of n=6j as 0, j；Control model according to selection inquires corresponding preset switches angle storage table, obtains voltage modulated than corresponding switch angle；Pulse signal driving current transformer is generated according to phase angle and obtained switch angle.The present invention can guarantee to export controlled current flow as far as possible, and guarantee to reduce major harmonic as far as possible, improve control effect.
Description
Technical field
The present invention relates to current transformer control technology fields, become mode more particularly to a kind of selective harmonic elimination pulsewidth modulation
Control method and its device.
Background technique
Diode clamp bit-type (NPC, Neutral point clamped) three-level current transformer is very suitable for the middle big function of pressure
Rate industry unsteady flow is driven (such as locomotive traction, offshore wind farm, metallurgy rolling mill, mine hoist, marine propeller) field, in conjunction with
The high voltage of current transformer, strong fluidity excessively can be achieved in existing commercial high voltage large power semiconductor device (such as IGBT, IGCT, IEGT etc.)
Energy.The three-phase topology of NPC three-level current transformer is as shown in Figure 1, wherein S1、S2、S3、S4For full-controlled switch device, each is opened
Close device all one freewheeling diode (D of inverse parallel1~D4), D5、D6For clamp diode, DC bus capacitor C1=C2, capacitor electricity
Pressure value is Udc/ 2, output current of converter io.A, B, C refer respectively to the output of AC side of converter A phase, B phase, C phase
End, P, O, N are respectively the anode, neutral point, negative terminal of current transformer DC side.
Selective harmonic elimination pulsewidth modulation (SHEPWM) is also referred to as switching-node preset PWM modulation, is by staircase waveform
" groove " of preset appropriate location selectively eliminates specific subharmonic, due to that can completely eliminate low-order harmonic, is exporting
Have when waveform quality is identical compared with low switching frequency, is caused by solving because of factors such as device lifetime, switching loss, heat dissipation limitations
Middle pressure great power conversion circuit occasion devices switch frequency only has the effective ways of several hundred hertz and then the series of problems of initiation.By voltage
Output voltage itself is containing only odd harmonics known to the symmetry of waveform；Meanwhile for three-phase voltage balanced system, due to line electricity
3 subharmonic are cancelled out each other in pressure, therefore conventional method is the integral multiple surprise for ignoring 3 when establishing harmonic wave eliminating Nonlinear System of Equations
Subharmonic, only consider to eliminate 3 times for several times other than odd harmonics.
But as user steps up converter system grid adaptability requirement, tolerance unbalanced source voltage degree at
For a Key Performance Indicator for examining converter system.And in the SHEPWM modulated process of NPC three-level current transformer, in power grid
It is poor for the control effect of the control of output current balance type and harmonics restraint under uneven operating condition, it is easy to appear out-of-control phenomenon.
Therefore, how a kind of selective harmonic elimination pulsewidth modulation that control effect is good is provided and becomes mode control method and its dress
Setting is the current problem to be solved of those skilled in the art.
Summary of the invention
The object of the present invention is to provide a kind of selective harmonic elimination pulsewidth modulations to become mode control method and its device, can
Guarantee output controlled current flow as far as possible, and guarantee to reduce major harmonic as far as possible, improves control effect.
In order to solve the above technical problems, the present invention provides a kind of selective harmonic elimination pulsewidth modulations to become scheme control side
Method is used for diode clamp bit-type NPC Multilevel Inverters, comprising:
Under power grid network pressure imbalance operating condition, current voltage modulated ratio m and phase angle are calculated；
The voltage modulated ratio is compared with default modulation ratio threshold value, if being less than the default modulation ratio threshold value,
The first control model is selected, if more than the default modulation ratio threshold value, then selects the second control model；Wherein, first control
It is 0 that molding formula, which is used to control the output current balance type of the NPC Multilevel Inverters and whole odd harmonics, second control
Molding formula is 0, n=6j ± 1 for controlling nth harmonic, and j is positive integer；
Control model according to selection inquires corresponding preset switches angle storage table, obtains the voltage modulated than corresponding
Switch angle；
Pulse signal, which is generated, according to the phase angle and the obtained switch angle drives the more level unsteady flows of NPC
Device.
Preferably, second control model specifically includes the first subpattern and the second subpattern, first submodule
Formula is used to control the output current balance type of the NPC Multilevel Inverters and nth harmonic is 0, and second subpattern is for controlling
The output voltage balance and nth harmonic for making the NPC Multilevel Inverters are 0.
Preferably, described to be compared the voltage modulated ratio with default modulation ratio threshold value, if being less than the default tune
System then selects the first control model, if more than the default modulation ratio threshold value, then selects the process of the second control model than threshold value
Specifically:
By the voltage modulated than comparing respectively with the first default modulation ratio threshold value and the second default modulation ratio threshold value
Compared with；
If being less than the described first default modulation ratio threshold value, the first control model is selected；
If more than the described second default modulation ratio threshold value, then the second control model is selected.
Preferably, the acquisition process of preset switches angle storage table are as follows:
The first Nonlinear System of Equations is solved by Solving Nonlinear Systems of Equations function fsolve (), to determine first control
The corresponding switch angle vector of different voltages modulation ratio under conditions of molding formula；First Nonlinear System of Equations are as follows:
The second Nonlinear System of Equations is solved by the Solving Nonlinear Systems of Equations function fsolve (), to determine described the
The corresponding switch angle vector of different voltages modulation ratio under conditions of two control models；Second Nonlinear System of Equations are as follows:
Wherein, UdcFor the NPC Multilevel Inverters DC voltage.
In order to solve the above technical problems, the present invention also provides a kind of selective harmonic elimination pulsewidth modulations to become scheme control dress
It sets, is used for diode clamp bit-type NPC Multilevel Inverters, comprising:
Modulation ratio determining module, for calculating current voltage modulated ratio m and phase under the not uneven operating condition of power grid network pressure
Parallactic angle；
Mode selection module, for the voltage modulated ratio to be compared with default modulation ratio threshold value, if being less than described
Default modulation ratio threshold value, then select the first control model, if more than the default modulation ratio threshold value, then selects the second control mould
Formula；Wherein, first control model is used to control the output current balance type and whole odd-times of the NPC Multilevel Inverters
Harmonic wave is 0, and second control model is 0, n=6j ± 1 for controlling nth harmonic, and j is positive integer；
Switching angle enquiry module is inquired corresponding preset switches angle storage table for the control model according to selection, is obtained
The voltage modulated is than corresponding switch angle；
Pulse control module, for generating pulse signal driving according to the phase angle and the obtained switch angle
The NPC Multilevel Inverters；
Switching angle storage table generation module, for obtaining preset switches angle storage table.
Preferably, the mode selection module specifically includes:
First selecting unit obtains for the voltage modulated ratio to be compared with the first default modulation ratio threshold value
One comparison result；
Second selecting unit is obtained for that will be compared the voltage modulated ratio with the second default modulation ratio threshold value
Second comparison result；
Mode selecting unit, for being analyzed according to first comparison result and second comparison result, if institute
Voltage modulated ratio is stated less than the described first default modulation ratio threshold value, then selects the first control model, if the voltage modulated is than big
In the described second default modulation ratio threshold value, then the second control model is selected.
Preferably, the switching angle storage table generation module specifically includes:
First mode determination unit, for solving the first non-linear side by Solving Nonlinear Systems of Equations function fsolve ()
Journey group, to determine the corresponding switch angle vector of different voltages modulation ratio under conditions of first control model；Described first
Nonlinear System of Equations are as follows:
Second mode determination unit, it is non-thread for solving second by the Solving Nonlinear Systems of Equations function fsolve ()
Property equation group, to determine the corresponding switch angle vector of different voltages modulation ratio under conditions of second control model；It is described
Second Nonlinear System of Equations are as follows:
The present invention provides a kind of selective harmonic elimination pulsewidth modulations to become mode control method and its device, is used for diode
Clamper type NPC Multilevel Inverters select phase according to voltage modulated ratio is currently calculated under unbalanced source voltage operating condition
The control model answered, in the case where voltage modulated is relatively low, current transformer is in complete to selection control output current balance type at this time
Controllable state, therefore whole odd harmonics 0 can be made；In the case that voltage modulated is relatively high, show that current transformer has gone out
The case where existing over-voltage, if wanting to guarantee that current transformer is controllable at this time, only controlling nth harmonic is 0, n=6j ± 1, and j is positive integer；
Corresponding switching angle is selected according to control model later and then output pulse signal drives NPC Multilevel Inverters.As it can be seen that this hair
It is bright to guarantee that current transformer is controllable always in the case where unbalanced source voltage, and export electric current and balance as far as possible, even if defeated
Current imbalance can also guarantee that main subharmonic is 0 out, and control effect is good.
Detailed description of the invention
It to describe the technical solutions in the embodiments of the present invention more clearly, below will be to institute in the prior art and embodiment
Attached drawing to be used is needed to be briefly described, it should be apparent that, the accompanying drawings in the following description is only some implementations of the invention
Example, for those of ordinary skill in the art, without creative efforts, can also obtain according to these attached drawings
Obtain other attached drawings.
Fig. 1 is the topological structure schematic diagram of diode clamp bit-type three-level current transformer；
Fig. 2 is the process for the process that a kind of selective harmonic elimination pulsewidth modulation provided by the invention becomes mode control method
Figure；
Fig. 3 is output single-phase voltage reason of the diode clamp bit-type three-level current transformer in selective harmonic elimination pulsewidth modulation
Think waveform diagram；
Fig. 4 is the positive-negative sequence current that a kind of selective harmonic elimination pulsewidth modulation provided by the invention becomes in mode control method
The schematic diagram of control process；
Fig. 5 is the structural schematic diagram that a kind of selective harmonic elimination pulsewidth modulation provided by the invention becomes mode control device.
Specific embodiment
Core of the invention is to provide a kind of selective harmonic elimination pulsewidth modulation and becomes mode control method and its device, can
Guarantee output controlled current flow as far as possible, and guarantee to reduce major harmonic as far as possible, improves control effect.
In order to make the object, technical scheme and advantages of the embodiment of the invention clearer, below in conjunction with the embodiment of the present invention
In attached drawing, technical scheme in the embodiment of the invention is clearly and completely described, it is clear that described embodiment is
A part of the embodiment of the present invention, instead of all the embodiments.Based on the embodiments of the present invention, those of ordinary skill in the art
Every other embodiment obtained without making creative work, shall fall within the protection scope of the present invention.
The present invention provides a kind of selective harmonic elimination pulsewidth modulations to become mode control method, is used for NPC (Neutral
Point clamped, diode clamp bit-type) Multilevel Inverters, shown in Figure 2, Fig. 2 is that one kind provided by the invention is specific
Harmonics elimination pulsewidth modulation becomes the flow chart of the process of mode control method；This method comprises:
Step s1: under power grid network pressure imbalance operating condition, current voltage modulated ratio m and phase angle are calculated；
Step s2: voltage modulated ratio is compared with default modulation ratio threshold value, if being less than default modulation ratio threshold value, is selected
The first control model is selected, if more than default modulation ratio threshold value, then selects the second control model；Wherein, the first control model is used for
Controlling the output current balance type of NPC Multilevel Inverters and whole odd harmonics is 0, and the second control model is for controlling n times
Harmonic wave is 0, n=6j ± 1, and j is positive integer；
Wherein, default modulation ratio threshold value here is preferably not less than the maximum of voltage modulated ratio under the first control model controllably
Value, because harmonic suppression effect is preferable and can control output current balance type, generally only in voltage under the first control model
Modulation ratio is excessively high, in the uncontrollable situation of the first control model, can just switch to the second control model and be controlled.
Step s3: the control model according to selection inquires corresponding preset switches angle storage table, obtains voltage modulated comparison
The switch angle answered；
Step s4: pulse signal driving NPC Multilevel Inverters are generated according to phase angle and obtained switch angle.
Wherein, voltage modulated ratio refers to current transformer output AC voltage fundamental voltage amplitude and current transformer input direct-current voltage value
The ratio between.
It is understood that phase angular region and voltage modulated corresponding to different control models are preparatory than range
It is determined by experiment.Preset switches angle storage table is to determine switch angle and voltage modulated ratio under different control models in advance
Corresponding relationship and obtain after being stored.
Specifically, the acquisition process of preset switches angle storage table here are as follows:
The first Nonlinear System of Equations is solved by Solving Nonlinear Systems of Equations function fsolve (), to determine the first control mould
The corresponding switch angle vector of different voltages modulation ratio under conditions of formula；First Nonlinear System of Equations are as follows:
The second Nonlinear System of Equations is solved by Solving Nonlinear Systems of Equations function fsolve (), to determine the second control mould
The corresponding switch angle vector of different voltages modulation ratio under conditions of formula；Second Nonlinear System of Equations are as follows:
Selective harmonic elimination pulsewidth modulation (SHEPWM, Selective Harmonic Elimination in the present invention
Pulse Width Modulation), also referred to as switching-node preset PWM modulation, the realization principle of SHEPWM be to phase voltage into
Row Fourier decomposition, pressure fundamental voltage amplitude are particular value, and by preset on staircase waveform " groove " appropriate come selectively
Make selected several low frequency subharmonic zero, the determination of " groove " position need to establish to eliminate specific subharmonic as objective function non-
System of linear equations solves the information of each switching angle by numerical value calculating.Common practice is preparatory solution nonlinear equation at present
Gained " groove " position angle information is switched after group to be stored in memory, it is (i.e. default to open by tabling look-up when normal operation
Close angle storage table) read corresponding switch angle information.
Shown in Figure 3, Fig. 3 is that diode clamp bit-type three-level current transformer is defeated in selective harmonic elimination pulsewidth modulation
Single-phase voltage ideal waveform figure out；Waveform, about α=pi/2 axial symmetry, is [0,2 π] in a primitive period in [0, π] section
About point (π, 0) central symmetry in section.(or it is radian, is denoted as comprising N number of perfect switch angle in a quarter period
α1、α2、…、αk、…、αN).Wherein, the moment of α=0 zero level, α=pi/2 moment are positive level, and N is odd number, and N number of switching angle
Numerical relation following relationship shown in:
For phase voltage u0, the output voltage itself known to the symmetry of waveform is free of even-order harmonic, humorous containing only odd-times
Wave, i.e. phase voltage u0It can be analyzed to:
Wherein, ω is the angular frequency of phase voltage, bnIt may be expressed as:
The Nonlinear System of Equations relational expression write is arranged the vector being made of each switching angle are as follows:
It is further known that for three-phase three-line system, when not considering voltage harmonic, power grid phase voltage uga,b,cIt can table
Show as follows:
Wherein, V+、V-Respectively voltage positive sequence, the amplitude of negative sequence component,For corresponding initial phase.If V-=
0 network voltage balance；Otherwise V-≠ 0 unbalanced source voltage.
Since current transformer is by adjusting itself output voltage uca,b,cIn real time change be added in filter (mainly filter inductance,
Assuming that Three-phase electric-wave filter parameter is consistent) the voltage u at both endsLa,b,cTo control the variation of output electric current, therefore (to export fundamental wave electricity
For the grid-connected converter of stream), to guarantee to export current balance type, need to be added in the balance of voltage on three pole reactor, i.e. VL-For
0, uLa,b,cIt is represented by following relational expression:
Wherein, VL、The respectively amplitude of inductive drop, initial phase.
Further, according to Kirchhoff's second law (KVL), there is uca,b,c=uga,b,c+uLa,b,c, i.e. current transformer exports electric
Press uca,b,cAre as follows:
Wherein, Vc+、Vc-Respectively output voltage positive sequence, the amplitude of negative sequence component,For corresponding initial phase
Position.
According to relation above formula it is found that under unbalanced source voltage operating condition, it is ensured that output current balance type, current transformer are defeated
Voltage is inevitable uneven out, and harmonic wave cannot cancel out each other 3 odd-multiple for several times in three-phase voltage at this time.Therefore to guarantee unsteady flow
Device exports electric current, and without 3 odd-multiple, harmonic wave, Nonlinear System of Equations can be refined as the first Nonlinear System of Equations for several times:
In addition, if keeping current transformer output voltage balance, (output electric current is uneven under unbalanced source voltage operating condition
Weighing apparatus), then 3 odd-multiple for several times cancel out each other by harmonic wave in three-phase voltage, does not need additionally to limit 3 at this time in Nonlinear System of Equations
Harmonic wave is 0 to odd-multiple for several times, and need to only limit n=6j ± 1 (j is positive integer) subharmonic is 0, under this restrictive condition, even if
Modulation ratio exceeds the control range of the first control model, can also be controlled by the second control model, therefore the second control model
Corresponding Nonlinear System of Equations can be refined as the second Nonlinear System of Equations:
Wherein, UdcFor the NPC Multilevel Inverters DC voltage,One group of switch for switching angle composition is angular
Amount；αkFor k-th of switching angle vector.
It can be obtained by experiment, after solving the first Nonlinear System of Equations using function fsolve (), voltage modulated can be obtained
The controlled range section of ratio be approximately m ∈ [0,1), using function fsolve () solve the second Nonlinear System of Equations after, can be obtained
The controlled range section of voltage modulated ratio be approximately m ∈ [0,1.6), therefore, can m ∈ [0,1) in section using the first control
Molding formula is controlled, beyond m ∈ [0,1) controlled using the second control model behind section, certainly, the present invention does not limit
The specific value of default modulation ratio threshold value.
Preferably, the second control model specifically includes the first subpattern and the second subpattern, and the first subpattern is used
It is 0 in the output current balance type and nth harmonic of control NPC Multilevel Inverters, the second subpattern becomes for controlling the more level of NPC
The output voltage balance and nth harmonic for flowing device are 0.
Wherein, depending on the first subpattern of specific choice or the second subpattern can be needed by user's foundation, the present invention is unlimited
Alternative condition between fixed two modes.
In addition, the process of step s2 specifically:
By voltage modulated than being compared respectively with the first default modulation ratio threshold value and the second default modulation ratio threshold value, if
Less than the first default modulation ratio threshold value, then the first control model is selected, if more than the second default modulation ratio threshold value, then selects second
Control model.
It is understood that the first default modulation ratio threshold value is less than the second modulation ratio threshold value, it is between the two pattern switching
Transition region.In pattern switching transition region, control model is still in the control model before switching transition, pattern switching transition region
Play the role of delay variation, for example, being at this time the first control less than the first default modulation ratio threshold value before voltage modulated ratio
Mode, voltage modulated ratio enters pattern switching transition region later, still keeps the first control model at this time.
Preferably, shown in Figure 4, Fig. 4 is that a kind of selective harmonic elimination pulsewidth modulation provided by the invention becomes mould
The schematic diagram of positive-negative sequence current control process in formula control method；Wherein, SwTo become mode selection switch, using positive and negative sequence
Under dq synchronous coordinate system current separation control (subscript+,-respectively indicate positive and negative sequence synchronous coordinate system, subscript d, q respectively indicates
D axis, q axis component under synchronous coordinate system)； For d axis, the instruction of q shaft current, i under positive sequence coordinate systemd+(id-)、iq+(iq-) be
D axis, q shaft current feedback quantity, u under positive (negative) sequence coordinate systemd+(ud-)、uq+(uq-) d axis, q shaft voltage under (negative) the sequence coordinate system that is positive
Feedforward amount, U+(U-)、θ+(θ-) reference voltage amplitude, phase under (negative) the sequence coordinate system that is positive, ma,b,c、θa,b,cFor three-phase ABC seat
Voltage modulated ratio, phase under mark system.After selecting control model, the process tool of the reference voltage of NPC Multilevel Inverters is controlled
Body are as follows:
Determine that NPC Multilevel Inverters are just under various control models according to positive-negative sequence voltage magnitude phase relation formula is preset
Negative phase-sequence reference voltage；
Default positive sequence voltage amplitude phase relational expression are as follows:
Default negative sequence voltage amplitude phase relational expression are as follows:
Determine that how electric NPC is under various control models according to positive-negative sequence reference voltage and three-phase voltage amplitude phase relational expression
The three-phase reference voltage of flat current transformer；
It should be noted that aforesaid operations are before formal modulation control, artificial control becomes mode selection switch in advance
Conduction mode, and calculate the modulation ratio range under the mode and phase angular region, above-mentioned three-phase reference voltage is modulation ratio model
It encloses and the intermediate parameter during the range computation of phase angle.
It is understood that separating control strategy by using positive-negative sequence current, can guarantee in certain modulation ratio model
Enclose under interior unbalanced source voltage operating condition output current of converter balance and THD (Total Harmonic Distortion,
Total percent harmonic distortion) it is minimum.
Preferably, the present invention can be used for two level current transformer of diode clamp bit-type or three-level current transformer or other
The current transformer of level, specifically can as needed depending on.
The present invention provides a kind of selective harmonic elimination pulsewidth modulations to become mode control method, is used for diode clamp bit-type
NPC Multilevel Inverters, it is more corresponding than selecting according to the voltage modulated being currently calculated under unbalanced source voltage operating condition
Control model, in the case where voltage modulated is relatively low, current transformer is in fully controllable to selection control output current balance type at this time
State, therefore whole odd harmonics 0 can be made；In the case that voltage modulated is relatively high, show that current transformer had already appeared
The case where pressure, if wanting to guarantee that current transformer is controllable at this time, only controlling nth harmonic is 0, n=6j ± 1, and j is positive integer；Later
Corresponding switching angle is selected according to control model and then output pulse signal drives NPC Multilevel Inverters.As it can be seen that the present invention exists
It in the case where unbalanced source voltage, can guarantee that current transformer is controllable always, and export electric current and balance as far as possible, even if output electricity
Stream imbalance can also guarantee that main subharmonic is 0, and control effect is good.
The present invention also provides a kind of selective harmonic elimination pulsewidth modulations to become mode control device, is used for diode clamp bit-type
NPC Multilevel Inverters, shown in Figure 5, Fig. 5 is that a kind of selective harmonic elimination pulsewidth modulation provided by the invention becomes mode control
The structural schematic diagram of device processed.The device includes:
Modulation ratio determining module 1, under the not uneven operating condition of power grid network pressure, calculate current voltage modulated ratio m and
Phase angle；
Mode selection module 2, for voltage modulated ratio to be compared with default modulation ratio threshold value, if being less than default modulation
Than threshold value, then the first control model is selected, if more than default modulation ratio threshold value, then selects the second control model；Wherein, the first control
It is 0 that molding formula, which is used to control the output current balance type of NPC Multilevel Inverters and whole odd harmonics, and the second control model is used
It is 0, n=6j ± 1 in control nth harmonic, j is positive integer；
Switching angle enquiry module 3 is inquired corresponding preset switches angle storage table for the control model according to selection, is obtained
Voltage modulated is than corresponding switch angle；
Pulse control module 4, for generating pulse signal according to the phase angle being calculated and obtained switch angle
Drive NPC Multilevel Inverters；
Switching angle storage table generation module 5, for obtaining preset switches angle storage table.
Wherein, mode selection module 2 specifically includes:
First selecting unit obtains the first ratio for voltage modulated ratio to be compared with the first default modulation ratio threshold value
Relatively result；
Second selecting unit obtains second for that will be compared voltage modulated ratio with the second default modulation ratio threshold value
Comparison result；
Mode selecting unit, for being analyzed according to the first comparison result with the second comparison result, if voltage modulated ratio
Less than the first default modulation ratio threshold value, then the first control model is selected, if voltage modulated ratio is greater than the second default modulation ratio threshold value,
Then select the second control model.
Wherein, switching angle storage table generation module 5 specifically includes:
First mode determination unit, for solving the first non-linear side by Solving Nonlinear Systems of Equations function fsolve ()
Journey group, to determine the corresponding switch angle vector of different voltages modulation ratio under conditions of the first control model；First non-linear side
Journey group are as follows:
Second mode determination unit, for solving the second non-linear side by Solving Nonlinear Systems of Equations function fsolve ()
Journey group, to determine the corresponding switch angle vector of different voltages modulation ratio under conditions of the second control model；Second non-linear side
Journey group are as follows:
UdcFor the NPC Multilevel Inverters DC voltage,For one group of switching angle vector of switching angle composition；αkFor
K-th of switching angle vector.
Preferably, the present invention can be used for two level current transformer of diode clamp bit-type or three-level current transformer or other
The current transformer of level, specifically can as needed depending on.
The present invention provides a kind of selective harmonic elimination pulsewidth modulations to become mode control device, is used for diode clamp bit-type
NPC Multilevel Inverters, it is more corresponding than selecting according to the voltage modulated being currently calculated under unbalanced source voltage operating condition
Control model, in the case where voltage modulated is relatively low, current transformer is in fully controllable to selection control output current balance type at this time
State, therefore whole odd harmonics 0 can be made；In the case that voltage modulated is relatively high, show that current transformer had already appeared
The case where pressure, if wanting to guarantee that current transformer is controllable at this time, only controlling nth harmonic is 0, n=6j ± 1, and j is positive integer；Later
Corresponding switching angle is selected according to control model and then output pulse signal drives NPC Multilevel Inverters.As it can be seen that the present invention exists
It in the case where unbalanced source voltage, can guarantee that current transformer is controllable always, and export electric current and balance as far as possible, even if output electricity
Stream imbalance can also guarantee that main subharmonic is 0, and control effect is good.
Each embodiment in this specification is described in a progressive manner, the highlights of each of the examples are with other
The difference of embodiment, the same or similar parts in each embodiment may refer to each other.For device disclosed in embodiment
For, since it is corresponded to the methods disclosed in the examples, so being described relatively simple, related place is said referring to method part
It is bright.
It should also be noted that, in the present specification, relational terms such as first and second and the like be used merely to by
One entity or operation are distinguished with another entity or operation, without necessarily requiring or implying these entities or operation
Between there are any actual relationship or orders.Moreover, the terms "include", "comprise" or its any other variant meaning
Covering non-exclusive inclusion, so that the process, method, article or equipment for including a series of elements not only includes that
A little elements, but also including other elements that are not explicitly listed, or further include for this process, method, article or
The intrinsic element of equipment.In the absence of more restrictions, the element limited by sentence "including a ...", is not arranged
Except there is also other identical elements in the process, method, article or apparatus that includes the element.
The foregoing description of the disclosed embodiments enables those skilled in the art to implement or use the present invention.
Various modifications to these embodiments will be readily apparent to those skilled in the art, as defined herein
General Principle can be realized in other embodiments without departing from the spirit or scope of the present invention.Therefore, of the invention
It is not intended to be limited to the embodiments shown herein, and is to fit to and the principles and novel features disclosed herein phase one
The widest scope of cause.
Claims (7)
1. a kind of selective harmonic elimination pulsewidth modulation becomes mode control method, diode clamp bit-type NPC Multilevel Inverters are used for,
It is characterised by comprising:
Under power grid network pressure imbalance operating condition, current voltage modulated ratio m and phase angle are calculated；
The voltage modulated ratio is compared with default modulation ratio threshold value, if being less than the default modulation ratio threshold value, is selected
First control model then selects the second control model if more than the default modulation ratio threshold value；Wherein, the first control mould
It is 0 that formula, which is used to control the output current balance type of the NPC Multilevel Inverters and whole odd harmonics, the second control mould
Formula is 0, n=6j ± 1 for controlling nth harmonic, and j is positive integer；
Control model according to selection inquires corresponding preset switches angle storage table, obtains the voltage modulated than corresponding switch
Angle；Pulse signal, which is generated, according to the phase angle and the obtained switch angle drives the NPC Multilevel Inverters.
2. the method according to claim 1, wherein second control model specifically include the first subpattern with
And second subpattern, first subpattern are used to control the output current balance type and nth harmonic of the NPC Multilevel Inverters
It is 0, second subpattern is used to control the output voltage balance of the NPC Multilevel Inverters and nth harmonic is 0.
3. according to the method described in claim 2, it is characterized in that, described by the voltage modulated ratio and default modulation ratio threshold value
It is compared, if being less than the default modulation ratio threshold value, the first control model is selected, if more than the default modulation ratio threshold
Value, then select the process of the second control model specifically:
By the voltage modulated than being compared respectively with the first default modulation ratio threshold value and the second default modulation ratio threshold value；
If being less than the described first default modulation ratio threshold value, the first control model is selected；
If more than the described second default modulation ratio threshold value, then the second control model is selected.
4. according to the method described in claim 3, it is characterized in that, the acquisition process of preset switches angle storage table are as follows:
The first Nonlinear System of Equations is solved by Solving Nonlinear Systems of Equations function fsolve (), to determine the first control mould
The corresponding switch angle vector of different voltages modulation ratio under conditions of formula；First Nonlinear System of Equations are as follows:
The second Nonlinear System of Equations is solved by the Solving Nonlinear Systems of Equations function fsolve (), to determine second control
The corresponding switch angle vector of different voltages modulation ratio under conditions of molding formula；Second Nonlinear System of Equations are as follows:
Wherein, UdcFor the NPC Multilevel Inverters DC voltage,For one group of switching angle vector of switching angle composition；αkFor
K-th of switching angle vector.
5. a kind of selective harmonic elimination pulsewidth modulation becomes mode control device, diode clamp bit-type NPC Multilevel Inverters are used for,
It is characterised by comprising:
Modulation ratio determining module, for calculating current voltage modulated ratio m and phase under the not uneven operating condition of power grid network pressure
Angle；
Mode selection module, for the voltage modulated ratio to be compared with default modulation ratio threshold value, if being less than described default
Modulation ratio threshold value then selects the first control model, if more than the default modulation ratio threshold value, then selects the second control model；Its
In, first control model is used to control the output current balance type of the NPC Multilevel Inverters and whole odd harmonics
It is 0, second control model is 0, n=6j ± 1 for controlling nth harmonic, and j is positive integer；
Switching angle enquiry module is inquired corresponding preset switches angle storage table for the control model according to selection, is obtained described
Voltage modulated is than corresponding switch angle；
Pulse control module, for being generated described in pulse signal driving according to the phase angle and the obtained switch angle
NPC Multilevel Inverters；
Switching angle storage table generation module, for obtaining preset switches angle storage table.
6. device according to claim 5, which is characterized in that the mode selection module specifically includes:
First selecting unit obtains the first ratio for the voltage modulated ratio to be compared with the first default modulation ratio threshold value
Relatively result；
Second selecting unit obtains second for that will be compared the voltage modulated ratio with the second default modulation ratio threshold value
Comparison result；
Mode selecting unit, for being analyzed according to first comparison result and second comparison result, if the electricity
It presses modulation ratio to be less than the described first default modulation ratio threshold value, then selects the first control model, if voltage modulated ratio is greater than institute
The second default modulation ratio threshold value is stated, then selects the second control model.
7. device according to claim 6, which is characterized in that the switching angle storage table generation module specifically includes:
First mode determination unit, for solving the first nonlinear equation by Solving Nonlinear Systems of Equations function fsolve ()
Group, to determine the corresponding switch angle vector of different voltages modulation ratio under conditions of first control model；Described first is non-
System of linear equations are as follows:
Second mode determination unit, for solving the second non-linear side by the Solving Nonlinear Systems of Equations function fsolve ()
Journey group, to determine the corresponding switch angle vector of different voltages modulation ratio under conditions of second control model；Described second
Nonlinear System of Equations are as follows:
UdcFor the NPC Multilevel Inverters DC voltage,For one group of switching angle vector of switching angle composition；αkFor kth
A switching angle vector.
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