CN113037113B - Neutral point balance control method and system of three-level NPC inverter - Google Patents
Neutral point balance control method and system of three-level NPC inverter Download PDFInfo
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- CN113037113B CN113037113B CN202110489652.6A CN202110489652A CN113037113B CN 113037113 B CN113037113 B CN 113037113B CN 202110489652 A CN202110489652 A CN 202110489652A CN 113037113 B CN113037113 B CN 113037113B
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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
- 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
- H02M7/53—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 using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/53871—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
- H02M7/53875—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 using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current with analogue control of three-phase output
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
- H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
- H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
- H02P27/08—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation
- H02P27/12—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation pulsing by guiding the flux vector, current vector or voltage vector on a circle or a closed curve, e.g. for direct torque control
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Abstract
The invention discloses a neutral point balance control method and a system of a three-level NPC inverter, wherein the method comprises the following steps: determining a vector synthesis relation between a reference voltage vector and a plurality of basic voltage vectors and action time of the plurality of basic voltage vectors in each region when the reference voltage vector is in each sector based on a VSVPWM space vector diagram; generating a vector wave-sending time table of each region in each sector by adopting a preset segment VSVPWM wave-sending mode based on a vector synthesis relation and a plurality of basic voltage vector action times; and setting a first adjusting factor and a second adjusting factor according to a preset rule on the basis of the vector wave-sending time table, and adjusting the first adjusting factor or the second adjusting factor on the basis of the neutral point voltage deviation, the first preset voltage deviation threshold value and the second preset voltage deviation threshold value. The invention can carry out neutral point voltage balance control on each area in each sector, has simpler control, reduces the cost and realizes accurate control of the neutral point voltage balance.
Description
Technical Field
The invention relates to the technical field of converters, in particular to a neutral point balance control method and system of a three-level NPC inverter.
Background
In high-voltage high-power occasions, three-level inverters are increasingly used, and three-level NPC inverters are widely applied to industry. The three-level NPC inverter does not have the problem of dynamic voltage balancing, can realize static balance of neutral point voltage through a corresponding control strategy, and has lower THD and du/dt. Therefore, the method has the advantages that the output waveform can be improved to be closer to a sine wave, the voltage stress applied to a single switching tube is lower, and the electromagnetic interference is low. The neutral point voltage is easy to generate deviation, which is an inherent defect of the NPC type three-level inverter, the low harmonic content of the output voltage is increased due to the unbalanced neutral point voltage, the output voltage is distorted, and the quality of electric energy is reduced.
At present, in order to solve the problem of unbalanced neutral point voltage in the prior art, one method is to balance the neutral point voltage by adding hardware devices. Another approach is to achieve neutral point voltage balancing through software control methods, such as by software control strategies based on SVPWM control strategies, virtual SVPWM (vsvpm), and adjustable virtual space vector neutral point voltages.
However, in the prior art, the balance of the neutral point voltage is realized by adding hardware equipment, so that not only is the control difficulty increased, but also the cost is increased; the balance of neutral point voltage is realized based on the SVPWM control strategy, so that the control effect is obviously reduced under the condition of larger power factor or modulation degree; although the control strategy based on the virtual SVPWM can not cause the phenomenon of unbalanced voltage of the neutral point theoretically, the phenomenon of unbalanced voltage of the neutral point can be caused due to the influence of factors such as inherent errors of a circuit hardware manufacturing process and unequal initial voltage of a direct current side; when the neutral point voltage control strategy of the adjustable virtual space vector is adopted, vector action time is complex to calculate due to the fact that the vector amplitude changes in real time, and actual implementation is often not advisable.
Disclosure of Invention
The invention provides a neutral point balance control method of a three-level NPC inverter, aiming at solving the technical problems of inaccurate neutral point voltage balance control, complex control and high cost in the prior art.
The invention provides a neutral point balance control method of a three-level NPC inverter, which comprises the following steps:
a vector synthesis step, which is used for determining the vector synthesis relation between the reference voltage vector and a plurality of basic voltage vectors and the action time of the plurality of basic voltage vectors in each region when the reference voltage vector is in each sector based on a VSVPWM space vector diagram;
generating a vector wave-sending time table, namely generating the vector wave-sending time table of each region in each sector by adopting a preset segment VSVPWM wave-sending mode based on the vector synthesis relation and the action time of the plurality of basic voltage vectors;
and a vector action time adjusting step of setting a first adjusting factor and a second adjusting factor according to a preset rule based on the vector wave-sending time table, and adjusting the first adjusting factor or the second adjusting factor based on the neutral point voltage deviation, a first preset voltage offset threshold and a second preset voltage offset threshold to realize dynamic adjustment of the vector action time of each region in each sector.
In the neutral point balance control method of the three-level NPC inverter, the preset rule in the vector action time adjusting step specifically includes:
when the neutral point voltage deviation is small, setting the first adjustment factor for a small vector contained in the basic voltage vector;
and when the neutral point voltage deviation is larger or the modulation ratio is larger, setting the second adjusting factor for a small vector contained in a virtual middle vector in the basic voltage vectors.
In the neutral point balance control method of the three-level NPC inverter, the adjusting the first adjustment factor and the second adjustment factor in the vector action time adjusting step specifically includes:
setting a neutral point voltage deviation judgment condition based on the neutral point voltage deviation, the first preset voltage deviation threshold value and the second preset voltage deviation threshold value;
and adjusting the first adjusting factor or the second adjusting factor based on the neutral point voltage bias judgment condition to realize dynamic adjustment of the vector action time of each region in each sector.
In the neutral point balance control method of the three-level NPC inverter, the neutral point voltage deviation determination condition includes:
a first neutral point voltage deviation judgment condition, a second neutral point voltage deviation judgment condition and a third neutral point voltage deviation judgment condition;
the first neutral point voltage deviation determination condition includes: judging whether the absolute value of the neutral point voltage deviation is smaller than the first preset voltage deviation threshold value or not;
the second neutral point voltage deviation determination condition includes: judging whether the absolute value of the neutral point voltage deviation is greater than or equal to the first preset voltage deviation threshold value and less than or equal to the second preset voltage deviation threshold value or not;
the third neutral point voltage deviation determination condition includes: and judging whether the absolute value of the neutral point voltage deviation is greater than the second preset voltage deviation threshold value or not.
In the neutral point balance control method of the three-level NPC inverter, the adjusting the first adjustment factor or the second adjustment factor based on the neutral point voltage bias judgment condition in the vector action time adjusting step specifically includes:
when the first neutral point voltage deviation judgment condition is met, the values of the first adjustment factor and the second adjustment factor are not required to be adjusted, namely the values of the first adjustment factor and the second adjustment factor are both 0;
when the second neutral point voltage deviation judgment condition is met, the value of the second adjustment factor is not required to be adjusted, namely the value of the second adjustment factor is 0, the value of the first adjustment factor is adjusted, and the positive and negative of the first adjustment factor are determined according to the direction of neutral point current;
and when the third neutral point voltage deviation judgment condition is met, adjusting the value of the first adjustment factor to be +/-1 according to the direction of the neutral point current, adjusting the value of the second adjustment factor, and determining the positive and negative of the second adjustment factor according to the direction of the neutral point current.
In the neutral point balance control method of the three-level NPC inverter, values of the first adjustment factor and the second adjustment factor are obtained by adjusting the neutral point voltage deviation PI, and the value ranges of the first adjustment factor and the second adjustment factor are adjusted to-1.
In the neutral point balance control method of the three-level NPC inverter, the step of generating the vector wave-generating schedule specifically includes:
based on the vector synthesis relation and a plurality of basic voltage vector acting time, nine-segment VSVPWM wave sending is adopted, and based on only controlling one switch level action each time, a vector wave sending time table of each region in each sector is generated.
In the neutral point balance control method of the three-level NPC inverter, the vector wave-generating schedule in the vector wave-generating schedule generating step specifically includes:
vector order, neutral point current and vector action time for each region in each of the sectors.
In the neutral point balance control method of the three-level NPC inverter, the zones in the vector synthesis step are triangular zones, and the reference voltage vector in each zone is synthesized by basic voltage vectors at three vertices of the corresponding triangular zone.
The invention also provides a system for realizing the neutral point balance control method of the three-level NPC inverter, which comprises the following steps:
the vector synthesis module is used for determining the vector synthesis relation between the reference voltage vector and a plurality of basic voltage vectors and the action time of the plurality of basic voltage vectors in each region when the reference voltage vector is in each sector based on the VSVPWM space vector diagram;
the vector wave-sending time table generating module is used for generating a vector wave-sending time table of each area in each sector by adopting a preset segment VSVPWM wave-sending mode based on the vector synthesis relation and the action time of the plurality of basic voltage vectors;
and the vector action time adjusting module is used for setting a first adjusting factor and a second adjusting factor according to a preset rule based on the vector wave sending time table, adjusting the first adjusting factor or the second adjusting factor based on the neutral point voltage deviation, a first preset voltage deviation threshold value and a second preset voltage deviation threshold value, and realizing the dynamic adjustment of the vector action time of each area in each sector.
The invention has the technical effects or advantages that:
the invention provides a neutral point balance control method of a three-level NPC inverter, which comprises the following steps: the method comprises the steps of determining a vector synthesis relation between a reference voltage vector and a plurality of basic voltage vectors in each region and a plurality of basic voltage vector acting time when the reference voltage vector is in each sector based on a VSVPWM (virtual synchronous pulse width modulation) space vector diagram, generating a vector wave-sending time table of each region in each sector by adopting a preset segment VSVPWM (virtual synchronous pulse width modulation) wave-sending mode based on the vector synthesis relation and the plurality of basic voltage vector acting time, setting a first regulating factor and a second regulating factor according to a preset rule based on the vector wave-sending time table, and regulating the first regulating factor or the second regulating factor based on neutral point voltage deviation, a first preset voltage deviation threshold and a second preset voltage deviation threshold to realize dynamic regulation of the vector acting time of each region in each sector. The neutral point balance control method of the three-level NPC inverter provided by the invention is based on the main circuit topological structure of the three-level inverter, realizes motor driving, vector synthesis, vector wave sending and vector regulation control through a hardware circuit, can perform neutral point voltage balance control on each area in each sector by setting the first regulation factor and the second regulation factor, is simpler in control, reduces the calculation which is not comparative, reduces the cost and realizes the accurate control of the neutral point voltage balance.
Drawings
Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention.
Fig. 1 is a topology structure diagram of a main circuit of a three-level NPC inverter according to an embodiment of the present invention;
FIG. 2 is a space vector diagram of a conventional three-level NPC inverter provided by an embodiment of the present invention;
FIG. 3 is a space vector diagram of a VSVPMs three-level NPC inverter provided by an embodiment of the present invention;
FIG. 4 is a vector diagram of a sector participating in composition provided by embodiments of the present invention;
FIG. 5 is a flow chart of a method of neutral point balance control for a three-level NPC inverter provided by an embodiment of the present invention;
fig. 6 is a block diagram of a system for implementing a neutral point balance control method for a three-level NPC inverter according to an embodiment of the present invention;
in the above figures:
1. a vector composition module; 2. a vector wave-sending time table generating module; 3. and the vector action time adjusting module.
Detailed Description
In order to make the technical solutions of the present invention better understood by those skilled in the art, the present invention will be further described in detail with reference to the accompanying drawings and the detailed description. Although embodiments of the invention are disclosed in the accompanying drawings, it should be understood that the invention can be embodied in any form and should not be construed as limited to the embodiments set forth herein.
In the description of the present invention, it is to be understood that the terms "inside", "outside", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are only for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. The terms "first," "second," "third," and the like, herein are used to describe various elements, components, regions, layers and/or sections, but only to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Terms such as "first," "second," "third," and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context.
In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the term "connected" is to be interpreted broadly, e.g. as a fixed connection, a detachable connection, or an integral connection; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
In order to solve the technical problems of inaccurate neutral point voltage balance control, complex control and high cost in the prior art, the invention provides a neutral point balance control method of a three-level NPC inverter, which is based on a main circuit topological structure of the three-level inverter, realizes motor drive, vector synthesis, vector wave generation and vector regulation control through a hardware circuit, can perform neutral point voltage balance control on each area in each sector by setting a first regulation factor and a second regulation factor, is simpler in control, reduces incomparable calculation, reduces cost and realizes accurate control of neutral point voltage balance.
The technical solution of the present invention will be described in detail below with reference to the specific embodiments and the accompanying drawings.
The embodiment relates to a neutral point balance control method of a three-level NPC inverter, which comprises the following steps:
a vector synthesis step S1, which is to determine the vector synthesis relation between the reference voltage vector and a plurality of basic voltage vectors in each region and the action time of the plurality of basic voltage vectors when the reference voltage vector is in each sector based on the VSVPWM space vector diagram;
a vector wave-sending time table generation step S2, which is to generate a vector wave-sending time table of each area in each sector by adopting a preset segment VSVPWM wave-sending mode based on the vector synthesis relation and the plurality of basic voltage vector action times;
and a vector action time adjusting step S3, setting a first adjusting factor and a second adjusting factor according to a preset rule based on the vector wave-sending time table, and adjusting the first adjusting factor or the second adjusting factor based on the neutral point voltage deviation, the first preset voltage deviation threshold and the second preset voltage deviation threshold to realize the dynamic adjustment of the vector action time of each area in each sector.
According to the neutral point balance control method of the three-level NPC inverter, neutral point voltage balance control can be performed on each area in each sector by setting the first adjustment factor and the second adjustment factor, the control is simpler, the calculation which is not comparative is reduced, the cost is reduced, and the accurate control of the neutral point voltage balance is realized.
Referring to fig. 5, the neutral point balance control method of the three-level NPC inverter provided in the present embodiment includes the following steps:
and a vector synthesis step S1, wherein the vector synthesis relation between the reference voltage vector and the plurality of basic voltage vectors in each region and the action time of the plurality of basic voltage vectors are determined based on the VSVPWM space vector diagram.
In this embodiment, the regions in the vector synthesis step S1 are triangular regions, and the reference voltage vector in each region is synthesized by the basic voltage vectors of the three vertices of the corresponding triangular region.
In a specific application, as an example, the following specifically describes the division of each sector and small region of the space vector diagram of the vsvsvsvspwm-based three-level NPC inverter, specifically as follows:
as shown in FIG. 1, in a general state, with the O point as a reference point of zero potential of the three-level NPC inverter, each bridge arm only has Udc/2, 0 and-UdcAnd/2, three possible output levels, namely, a positive state (P), a zero state (O) and a negative state (N) are respectively arranged on each phase output. As shown in fig. 2, according to the output state of each phase of the three-level NPC inverter, the corresponding relationship between the space vector of the three-level NPC inverter on the α β plane and the switch combination can be obtained(i.e., three-level NPC inverter space vector diagram). As shown in fig. 3, according to the three-level space vector diagram, the hexagon of the α β plane can be divided into six large sectors, starting from the α axis, and named as I-VI six large sectors according to the counterclockwise direction, in each sector, the level state is considered and divided into a plurality of small regions, and the vsvsvsvspwm adds a virtual vector on the basis of SVPWM, so as to obtain the vsvsvpm space vector diagram. Wherein, the labels I, II, III, IV, V, VI correspond to 6 large sectors, each large sector is divided into 5 small areas, and the labels 1, 2, 3, 4, 5 correspond to 5 small areas in each large sector. Taking the first sector I as an example, define:
wherein, VMDirection and origin vector VPONSame direction, VMIs changed into V PON2/3, the virtual medium vector V is found based on the above formulaMCurrent i flowing into neutral point O during action timea、ibAnd icThe action time is equal, so that the average current flowing through the neutral point O is 0, and the voltage of the neutral point is not influenced. The zero vector comprises OOO, NNN and PPP, the large vector comprises PNN and PPN, and the zero vector and the large vector have no influence on the voltage balance of the neutral point because no current exchange exists between the neutral point and the load; the small vectors comprise PPO, OON, ONN and POO, wherein PPO and ONN are positive small vectors, OON and POO are negative small vectors, the small vectors appear in pairs, the action time of the positive small vectors is equal to that of the negative small vectors, the current flowing through the neutral point is equal in magnitude and opposite in direction, and the influence on the voltage of the neutral point can be mutually offset.
In the present embodiment, as an example, the process of the vector synthesis step S1 is specifically described, and as shown in fig. 4, the reference voltage vector in each small area is synthesized by three basic voltage vectors of corresponding triangles. Taking the first sector I as an example, suppose that the reference voltage vector is in the small region 1, and the basic voltage vector participating in the synthesis is V0(OOO、NNN、PPP)、V1(ONN, POO) and V2(PPO, OON); the reference voltage vector is in the small area 2, and the basic voltage vector participating in the synthesis is V1(ONN、POO)、V2(PPO, OON) and VM(ONN, PON, PPO); when the reference voltage vector is in the small region 3, the basic voltage vector participating in the synthesis is V1(ONN、POO)、V3(PNN) and VM(ONN, PON, PPO); when the reference voltage vector is in the small region 4, the basic voltage vector participating in the synthesis is V2(PPO、OON)、V4(PPN) and VM(ONN, PON, PPO); when the reference voltage vector is in the small area 5, the basic voltage vector participating in the synthesis is V3(PNN)、V4(PPN) and VM(ONN, PON, PPO). Setting a basic voltage vector V0The action time is T0Basic voltage vector V1The action time is T1Basic voltage vector V2The action time is T2Basic voltage vector V3The action time is T3The action time of the basic voltage vector V4 is T4Basic voltage vector (virtual medium vector) VMThe action time is TM. According to the process of vector synthesis of the first sector I, the vector synthesis relationship of the remaining sectors can be obtained in the same manner, which is not described in detail in this embodiment.
And a vector wave-sending time table generating step S2, wherein a preset segment VSVPWM wave-sending mode is adopted to generate a vector wave-sending time table of each area in each sector based on the vector synthesis relation and the plurality of basic voltage vector acting times.
In this embodiment, the step S2 of generating the vector wave-sending schedule specifically includes:
based on the vector composition relation and a plurality of basic voltage vector acting time, nine-segment VSVPWM wave sending is adopted, and based on only controlling one switch level action each time, a vector wave sending time table of each area in each sector is generated.
In this embodiment, the vector wave-sending time table generating step S2 specifically includes:
vector order, neutral point current and vector action time for each region in each sector.
A vector action time adjusting step S3, setting a first adjusting factor k according to a preset rule based on a vector wave sending time table1And a second adjustment factor k2Based on neutral point voltage deviation Δ UdcA first predetermined voltage offset threshold value delta Udc1And a second preset voltage offset threshold DeltaUdc2Adjusting the first adjustment factor k1Or a second adjustment factor k2And dynamic adjustment of the vector action time of each region in each sector is realized.
In this embodiment, the first predetermined voltage offset threshold Δ Udc1And a second preset voltage offset threshold DeltaUdc2Can be set according to actual needs, and the first preset voltage deviation threshold value delta Udc1And a second preset voltage offset threshold DeltaUdc2The specific value of (a) is not specifically limited in this embodiment, and in this embodiment, Δ Udc1<ΔUdc2Wherein the first predetermined voltage deviation threshold value Δ Udc1And a second preset voltage offset threshold DeltaUdc2Are all positive values.
The embodiment sets the first adjustment factor k1And a second adjustment factor k2The neutral point voltage balance control can be carried out on each area in each sector, the control is simpler, the calculation which is not compared is reduced, the cost is reduced, and the accurate control of the neutral point voltage balance is realized.
In this embodiment, the rule preset in the vector action time adjusting step S3 specifically includes:
voltage deviation delta U when neutral pointdcWhen smaller, a first adjustment factor k is set for the small vectors contained in the basic voltage vector1；
Voltage deviation delta U when neutral pointdcWhen the modulation ratio is larger or larger, a second adjustment factor k is set for a small vector contained in a virtual middle vector in the basic voltage vectors2。
In a specific application, the first adjustment factor k1Adjusting the action time of the positive and negative small vectors by a second adjustment factor k2The action time of three vectors corresponding to the virtual middle vector is adjusted, in the embodiment, the neutral point voltage deviation is providedThe volume can be represented as:
ΔUdc＝Udc1-Udc2
wherein, in the above formula, Δ UdcExpressed as neutral point voltage deviation; u shapedc1Expressed as bus capacitance C1Voltage across; u shapedc2Expressed as bus capacitance C2The voltage across (c). In this embodiment, take the first sector I as an example, and include the first adjustment factor k1And a second adjustment factor k2The vector wave-generating table of (2) is shown in table 1. Similarly, the remaining sectors contain the first adjustment factor k1And a second adjustment factor k2The vector wave-launching table can also be obtained according to the method, and details are not described in this embodiment.
TABLE 1 VSVPWM WAVE TIME TABLE BASED ON DOUBLE-REGULATING FACTOR
In the present embodiment, the first adjustment factor k is adjusted in the vector action time adjustment step S31And a second adjustment factor k2The method specifically comprises the following steps:
based on neutral point voltage deviation delta UdcA first predetermined voltage offset threshold value delta Udc1And a second preset voltage offset threshold DeltaUdc2Setting a neutral point voltage deviation judgment condition;
adjusting a first adjustment factor k based on the neutral point voltage bias determination condition1Or a second adjustment factor k2And dynamic adjustment of the vector action time of each region in each sector is realized.
In this embodiment, the neutral point voltage deviation determination condition includes:
a first neutral point voltage deviation judgment condition, a second neutral point voltage deviation judgment condition and a third neutral point voltage deviation judgment condition;
the first neutral point voltage deviation determination condition includes: judging neutral point voltage deviation delta UdcIs less than a first predetermined voltage offset threshold value deltaudc1；
The second neutral point voltage deviation determination condition includes: judging neutral point voltage deviation delta UdcIs greater than or equal to a first predetermined voltage offset threshold value DeltaUdc1And is less than or equal to a second preset voltage offset threshold delta Udc2；
The third neutral point voltage deviation determination condition includes: judging neutral point voltage deviation delta UdcIs greater than a second predetermined voltage offset threshold value deltaudc2。
In a specific application, the second neutral point voltage deviation determination condition specifically includes:
judging neutral point voltage deviation delta UdcWhether the voltage is greater than or equal to a first preset voltage deviation threshold value delta Udc1And is less than or equal to a second preset voltage offset threshold delta Udc2；
Judging neutral point voltage deviation delta UdcWhether the voltage is greater than or equal to a second preset voltage deviation threshold value delta Udc2Is less than or equal to a first preset voltage offset threshold value delta Udc1The opposite number of (c).
The third neutral point voltage deviation determination condition specifically includes:
judging neutral point voltage deviation delta UdcWhether or not it is greater than a second predetermined voltage deviation threshold value delta Udc2；
Judging neutral point voltage deviation delta UdcWhether or not it is less than a second preset voltage offset threshold value delta Udc2The opposite number of (c).
In the present embodiment, the first adjustment factor k is adjusted based on the neutral point voltage bias judgment condition in the vector application time adjustment step S31Or a second adjustment factor k2The method specifically comprises the following steps:
when the first neutral point voltage deviation judgment condition is met, the first adjustment factor k does not need to be adjusted1And a second adjustment factor k2Taking the value of (A); in particular, the first adjustment factor k need not be adjusted1And a second adjustment factor k2Is a first adjustment factor k10 and a second adjustment factor k2＝0；
When the second neutral point voltage deviation judgment condition is satisfied, the second adjustment factor k does not need to be adjusted2Is a second adjustment factor k2Adjusting the first adjustment factor k to 01And according to the neutral point current iNPDetermines a first adjustment factor k1Positive and negative; in this embodiment, the first adjustment factor k1And a second adjustment factor k2Value of UdcpIout is regulated by a neutral voltage deviation PI, a first regulation factor k1And a second adjustment factor k2The value range of (a) is-1 to 1. In particular, the first adjustment factor k1The value range of (a) is-1 to 1; according to neutral point current iNPDetermines a first adjustment factor k1The positive and negative specifically mean: when current of neutral point iNP>At 0, k1Taking a negative value, when the current i is at neutral pointNP<At 0, k1Taking a positive value;
referring to small region 1 in Table 1, a positive small vector ONN acts on the corresponding neutral point current iaIf i isa>0, the time of action, k, of the positive small vector ONN needs to be reduced1Taking a negative value, i.e. k1＝-fabs(UdcPI _ out); if ia<0, the action time, k, of the positive small vector ONN needs to be increased1Take a positive value, i.e. k1＝fabs(Udc_PI_out)。
When the third neutral point voltage deviation judgment condition is met, according to the neutral point current iNPBy a first adjustment factor k1Taking the value as +/-1 and adjusting a second adjusting factor k2Is calculated according to the neutral point current iNPDetermines a second adjustment factor k2Positive and negative. In this embodiment, the first adjustment factor k1And a second adjustment factor k2Value of UdcpIout is regulated by a neutral voltage deviation PI, a first regulation factor k1And a second adjustment factor k2The value range of (a) is-1 to 1. Utensil for cleaning buttockIn general terms, according to the neutral point current iNPBy a first adjustment factor k1The value of ± 1 means specifically: when current of neutral point iNP>When 0, then k is taken11, neutral point current iNP<When 0, then k is taken11 is ═ 1; second adjustment factor k2The value range of (a) is-1 to 1; adjusting the second adjustment factor k2Is calculated according to the neutral point current iNPDetermines the second adjustment factor k2The positive and negative specifically mean: when current of neutral point iNP>At 0, k2Taking a negative value, when the current i is at neutral pointNP<At 0, k2Take a positive value.
Referring to the small region 4 in Table 1, the positive small vector PPO effect corresponds to a neutral point current of icIf i isc>0, the action time, k, of the positive small vector PPO needs to be reduced1-1; if ic<0, the action time of the positive small vector PPO needs to be increased, k 11. The neutral point current corresponding to the middle vector PON action is ibIf i isb>0, then the active time of the medium vector PON needs to be reduced, k2Taking a negative value, i.e. k2＝-fabs(UdcPI _ out); if ib<0, the action time, k, of the middle vector PON needs to be increased2Take a positive value, i.e. k2＝fabs(Udc_PI_out)。
In this embodiment, the voltage deviation Δ U to the neutral pointdcThree threshold intervals are set, and active and hysteresis control methods are adopted for vector action time under different threshold intervals to obtain a first adjustment factor k1And a second adjustment factor k2The vector wave-sending time table avoids unnecessary adjustment, so that the control method is more reasonable and effective, and the control precision is faster and more accurate.
The neutral point balance control method of the three-level NPC inverter provided in this embodiment is based on a main circuit topology structure of the three-level NPC inverter, and realizes motor driving, vector synthesis, vector wave generation, and vector adjustment control through a hardware circuit, and can perform neutral point voltage balance control on each area in each sector by setting a first adjustment factor and a second adjustment factor, and the control is simpler, thereby reducing unnecessary calculation, reducing cost, and realizing accurate control of neutral point voltage balance.
The present embodiment also provides a system for implementing a neutral point balance control method of a three-level NPC inverter, referring to fig. 6, including: the device comprises a vector synthesis module 1, a vector wave-sending time table generation module 2 and a vector action time adjusting module 3, wherein the vector synthesis module 1 is connected with the vector wave-sending time table generation module 2, and the vector wave-sending time table generation module 2 is connected with the vector action time adjusting module 3. Specifically, the method comprises the following steps:
the vector synthesis module is used for determining the vector synthesis relation between the reference voltage vector and a plurality of basic voltage vectors in each region and the action time of the plurality of basic voltage vectors when the reference voltage vector is in each sector based on the VSVPWM space vector diagram;
the vector wave-sending time table generating module is used for generating a vector wave-sending time table of each area in each sector by adopting a preset segment VSVPWM wave-sending mode based on a vector synthesis relation and a plurality of basic voltage vector action times;
and the vector action time adjusting module is used for setting a first adjusting factor and a second adjusting factor according to a preset rule based on the vector wave sending time table, adjusting the first adjusting factor or the second adjusting factor based on the neutral point voltage deviation, the first preset voltage deviation threshold and the second preset voltage deviation threshold, and realizing the dynamic adjustment of the vector action time of each area in each sector.
The system for realizing the neutral point balance control method of the three-level NPC inverter provided by this embodiment is based on a main circuit topological structure of the three-level inverter, realizes motor driving, vector synthesis, vector wave generation and vector regulation control through a hardware circuit, and can perform neutral point voltage balance control on each area in each sector by setting a first regulation factor and a second regulation factor, and the control is simpler, thereby reducing the calculation which is not comparative, reducing the cost and realizing the accurate control of the neutral point voltage balance.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims (6)
1. A neutral point balance control method of a three-level NPC inverter is characterized by comprising the following steps:
a vector synthesis step, which is used for determining the vector synthesis relation between the reference voltage vector and a plurality of basic voltage vectors and the action time of the plurality of basic voltage vectors in each region when the reference voltage vector is in each sector based on a VSVPWM space vector diagram;
generating a vector wave-sending time table, namely generating the vector wave-sending time table of each region in each sector by adopting a preset segment VSVPWM wave-sending mode based on the vector synthesis relation and the action time of the plurality of basic voltage vectors;
a vector action time adjusting step of setting a first adjusting factor and a second adjusting factor according to a preset rule based on the vector wave-sending time table, and adjusting the first adjusting factor or the second adjusting factor based on the neutral point voltage deviation, a first preset voltage offset threshold and a second preset voltage offset threshold to realize dynamic adjustment of the vector action time of each region in each sector;
the preset rule specifically comprises: when the neutral point voltage deviation is small, setting the first adjustment factor for a small vector contained in the basic voltage vector; when the neutral point voltage deviation is large or the modulation ratio is large, setting the second adjusting factor for a small vector contained in a virtual middle vector in the basic voltage vectors;
adjusting the first adjustment factor and the second adjustment factor specifically includes: setting a neutral point voltage deviation judgment condition based on the neutral point voltage deviation, the first preset voltage deviation threshold value and the second preset voltage deviation threshold value; based on the neutral point voltage bias judgment condition, adjusting the first adjustment factor or the second adjustment factor to realize dynamic adjustment of the vector action time of each region in each sector;
the neutral point voltage deviation judgment condition includes: a first neutral point voltage deviation judgment condition, a second neutral point voltage deviation judgment condition and a third neutral point voltage deviation judgment condition; the first neutral point voltage deviation determination condition includes: judging whether the absolute value of the neutral point voltage deviation is smaller than the first preset voltage deviation threshold value or not; the second neutral point voltage deviation determination condition includes: judging whether the absolute value of the neutral point voltage deviation is greater than or equal to the first preset voltage deviation threshold value and less than or equal to the second preset voltage deviation threshold value or not; the third neutral point voltage deviation determination condition includes: judging whether the absolute value of the neutral point voltage deviation is greater than a second preset voltage deviation threshold value or not;
adjusting the first adjustment factor or the second adjustment factor based on the neutral point voltage bias judgment condition specifically includes: when the first neutral point voltage deviation judgment condition is met, the values of the first adjustment factor and the second adjustment factor are not required to be adjusted, namely the values of the first adjustment factor and the second adjustment factor are both 0; when the second neutral point voltage deviation judgment condition is met, the value of the second adjustment factor is not required to be adjusted, namely the value of the second adjustment factor is 0, the value of the first adjustment factor is adjusted, and the positive and negative of the first adjustment factor are determined according to the direction of neutral point current; and when the third neutral point voltage deviation judgment condition is met, adjusting the value of the first adjustment factor to be +/-1 according to the direction of the neutral point current, adjusting the value of the second adjustment factor, and determining the positive and negative of the second adjustment factor according to the direction of the neutral point current.
2. The neutral point balance control method of the three-level NPC inverter according to claim 1, wherein the values of the first and second adjustment factors are obtained by adjusting the neutral point voltage deviation PI, and the values of the first and second adjustment factors are adjusted to be-1.
3. The neutral point balance control method of the three-level NPC inverter according to claim 1, wherein the vector wave-generating schedule generating step specifically includes:
and generating a vector wave-sending time table of each region in each sector by adopting nine-segment VSVPWM wave-sending based on the vector synthesis relation and a plurality of basic voltage vector acting time and controlling only one switch level action each time.
4. The neutral point balance control method of the three-level NPC inverter according to any one of claims 1 or 3, wherein the vector wave-generating schedule generating step, in the vector wave-generating schedule, specifically includes:
vector order, neutral point current and vector action time for each region in each of the sectors.
5. The neutral point balance control method of a three-level NPC inverter according to claim 1, wherein the zones in the vector synthesizing step are triangular zones, and the reference voltage vector in each zone is synthesized from basic voltage vectors of three vertices of the corresponding triangular zone.
6. A system for implementing a neutral point balance control method for a three-level NPC inverter, comprising:
the vector synthesis module is used for determining the vector synthesis relation between the reference voltage vector and a plurality of basic voltage vectors and the action time of the plurality of basic voltage vectors in each region when the reference voltage vector is in each sector based on the VSVPWM (virtual synchronous pulse width modulation) space vector diagram;
the vector wave-sending time table generating module is used for generating a vector wave-sending time table of each area in each sector by adopting a preset segment VSVPWM wave-sending mode based on the vector synthesis relation and the action time of the plurality of basic voltage vectors;
the vector action time adjusting module is used for setting a first adjusting factor and a second adjusting factor according to a preset rule based on the vector wave sending time table, adjusting the first adjusting factor or the second adjusting factor based on neutral point voltage deviation, a first preset voltage offset threshold value and a second preset voltage offset threshold value, and realizing dynamic adjustment of the vector action time of each area in each sector;
the preset rule specifically comprises: when the neutral point voltage deviation is small, setting the first adjustment factor for a small vector contained in the basic voltage vector; when the neutral point voltage deviation is large or the modulation ratio is large, setting the second adjusting factor for a small vector contained in a virtual middle vector in the basic voltage vectors;
adjusting the first adjustment factor and the second adjustment factor specifically includes: setting a neutral point voltage deviation judgment condition based on the neutral point voltage deviation, the first preset voltage deviation threshold value and the second preset voltage deviation threshold value; adjusting the first adjustment factor or the second adjustment factor based on the neutral point voltage bias judgment condition to realize dynamic adjustment of the vector action time of each region in each sector;
the neutral point voltage deviation judgment condition includes: a first neutral point voltage deviation judgment condition, a second neutral point voltage deviation judgment condition and a third neutral point voltage deviation judgment condition; the first neutral point voltage deviation determination condition includes: judging whether the absolute value of the neutral point voltage deviation is smaller than the first preset voltage deviation threshold value or not; the second neutral point voltage deviation determination condition includes: judging whether the absolute value of the neutral point voltage deviation is greater than or equal to the first preset voltage deviation threshold value and less than or equal to the second preset voltage deviation threshold value or not; the third neutral point voltage deviation determination condition includes: judging whether the absolute value of the neutral point voltage deviation is greater than a second preset voltage deviation threshold value or not;
adjusting the first adjustment factor or the second adjustment factor based on the neutral point voltage bias judgment condition specifically includes: when the first neutral point voltage deviation judgment condition is met, the values of the first adjustment factor and the second adjustment factor are not required to be adjusted, namely the values of the first adjustment factor and the second adjustment factor are both 0; when the second neutral point voltage deviation judgment condition is met, the value of the second adjustment factor is not required to be adjusted, namely the value of the second adjustment factor is 0, the value of the first adjustment factor is adjusted, and the positive and negative of the first adjustment factor are determined according to the direction of neutral point current; and when the third neutral point voltage deviation judgment condition is met, adjusting the value of the first adjustment factor to be +/-1 according to the direction of the neutral point current, adjusting the value of the second adjustment factor, and determining the positive and negative of the second adjustment factor according to the direction of the neutral point current.
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