CN116961460B - Space vector pulse width modulation method and device based on virtual space vector - Google Patents

Abstract

The invention discloses a space vector pulse width modulation method and equipment based on virtual space vectors, and relates to the field of power electronic converter control. The method includes: calculating the virtual small vector according to the vector sum of the positive small vector and the negative small vector; calculating the virtual medium vector according to the virtual space vector distribution coefficient and the positive small vector and the medium vector in two different directions; for any fan area, according to the different overmodulation of the reference voltage vector and the amplitude of the reference voltage vector, the effect of the basic vector is calculated using the method based on the overmodulation compensation coefficient, the method based on the amplitude and phase hybrid compensation, or the method based on the simultaneous compensation of the amplitude and phase. time, thereby performing space vector pulse width modulation according to the action time of the basic vector. The invention can reduce output voltage harmonics and distortion.

Description

A space vector pulse width modulation method and equipment based on virtual space vector

Technical field

The invention relates to the field of power electronic converter control, and in particular to a space vector pulse width modulation method and equipment based on virtual space vectors.

Background technique

Compared with traditional two-level inverters, midpoint clamped (NPC) three-level inverters have more output levels, lower output voltage harmonic content, lower voltage conversion rate, and less electromagnetic interference. Small, high output efficiency, smaller switching losses, common mode voltage and midpoint potential can be suppressed by the same algorithm. At the same time, with the development of Space Vector Pulse Width Modulator (SVPWM) technology, three-level converters have gradually replaced two-level converters as the main topology structure. At the same time, the control strategy of three-level converters has been It has become a research hotspot in today’s power electronics technology.

Compared with the traditional PWM modulation algorithm, the output voltage of SVPWM technology is increased by about 15%. However, the SVPWM modulation technology itself has an over-modulation area. When the reference voltage amplitude exceeds a certain value, the voltage vector trajectory synthesized by the basic vector will no longer be Being circular, the output voltage and current will produce distortion and harmonics, and may even pollute the power grid.

Before the 1990s, most algorithm research was limited to the linear modulation region, and its modulation range was within 90%. In engineering applications, in order to improve the utilization rate of the DC bus by the converter, increase the output voltage amplitude of the inverter, improve the motor output torque and the low-voltage applicability requirements of the converter, domestic and foreign scholars have proposed relevant SVPWM overmodulation algorithms, such as dual-mode and single-mode overmodulation algorithms, have achieved certain results. However, these overmodulation strategies do not take into account the impact on the midpoint potential.

The basic vectors that synthesize the voltage vector of the three-level converter include small vectors, medium vectors and large vectors. The small vectors and medium vectors will generate midpoint current, causing the charge and discharge of the DC capacitor, causing midpoint potential fluctuations and causing the output voltage. Increase in fluctuations and harmonic components. Small vectors exist in pairs and the midpoint currents generated by positive and negative small vectors have opposite directions and have opposite effects on the midpoint potential. Their influence can be eliminated by allocating the action time; the midpoint vector exists alone, so it is uncontrollable in the traditional algorithm. When the voltage vector is synthesized in the modulation area, the midpoint vector accounts for a larger proportion, so the phenomenon of midpoint potential fluctuations is more obvious in the overmodulation area, and will produce fluctuations higher than the output frequency. Midpoint potential fluctuations and imbalances will cause a A series of hazards, such as increased output voltage harmonics, voltage distortion, pollution of the power grid, shortened device life, breakdown of power switching devices, etc.

Contents of the invention

Embodiments of the present invention provide a space vector pulse width modulation method and equipment based on virtual space vector (NTV2), which can reduce fluctuations and imbalances of midpoint potential and reduce output voltage harmonics and distortion.

In order to achieve the above objects, embodiments of the present invention adopt the following technical solutions:

In the first aspect, a space vector pulse width modulation method based on virtual space vectors is provided, including:

Obtain the space vector diagram corresponding to the voltage of the three-phase inverter circuit in one switching cycle; the space vector diagram includes: six sectors;

Calculate virtual small vectors based on the vector sum of positive small vectors and negative small vectors in the space vector diagram;

Calculate the virtual middle vector according to the virtual space vector distribution coefficient, two positive small vectors in different directions in the space vector diagram, and the middle vector in the space vector diagram;

For any sector, if the reference voltage vector is in the overmodulation I zone and the amplitude of the reference voltage vector is greater than the set value, the action time of the basic vector is calculated based on the overmodulation compensation coefficient; the basic vector includes: virtual small vector , virtual medium vectors and large vectors in space vector diagrams;

For any sector, if the reference voltage vector is in the overmodulation I zone and the amplitude of the reference voltage vector is less than or equal to the set value, the action time of the basic vector is calculated based on the amplitude phase hybrid compensation method;

For any sector, if the reference voltage vector is in the overmodulation II area, the action time of the basic vector is calculated based on the simultaneous amplitude and phase compensation method;

Within a switching cycle, space vector pulse width modulation is performed according to the action time of the basic vector.

In a first possible implementation method, combined with the first aspect, the action time of the basic vector is calculated based on the overmodulation compensation coefficient, which specifically includes:

If the motion trajectory of the reference voltage vector in a certain sector is a nonlinear area, the action time of the basic vector is calculated based on the switching period, the action time of the neutral vector, and the rotation angle;

If the motion trajectory of the reference voltage vector in a certain sector is a linear region, the action time of the basic vector is calculated based on the overmodulation compensation coefficient.

In the second possible implementation method, combined with the first aspect, the action time of the basic vector is calculated based on the amplitude phase mixing compensation method, which includes:

If the motion trajectory of the reference voltage vector in a certain sector is a nonlinear area, the action time of the basic vector is calculated based on the switching period, the action time of the neutral vector, and the rotation angle;

If the motion trajectory of the reference voltage vector in a certain sector is a linear area, the action time of the basic vector is calculated based on the overmodulation compensation coefficient;

If the motion trajectory of the reference voltage vector in a certain sector is a linear compensation area, the amplitude-phase hybrid compensation method is used to calculate the action time of the basic vector.

In a third possible implementation manner, combined with the first possible implementation manner of the first aspect, the reference voltage vector is in the overmodulation I region, the amplitude of the reference voltage vector is greater than the set value, and the reference voltage vector is in a certain sector. When the motion trajectory of the area is a nonlinear area, the calculation formula of the action time of the basic vector is:

in, Indicates the action time of the virtual vector;/> Represents the action time of a large vector;/> represents the action time of the virtual small vector; T _S represents the switching period; θ represents the rotation angle.

In a fourth possible implementation manner, combined with the first possible implementation manner of the first aspect, the reference voltage vector is in the overmodulation I region, the amplitude of the reference voltage vector is greater than the set value, and the reference voltage vector is in a certain sector. When the movement trajectory of the area is a linear area, the calculation formula of the action time of the basic vector is:

Among them, eta represents the over-modulation compensation coefficient; Indicates the action time of the virtual vector before compensation;/> Indicates the action time of the virtual small vector before compensation;/> Indicates the action time of the large vector before compensation.

In the fifth possible implementation manner, combined with the second possible implementation manner of the first aspect, if the reference voltage vector is in the overmodulation I region, the amplitude of the reference voltage vector is less than or equal to the set value and the reference voltage vector is in When the motion trajectory of a certain sector is a linear compensation area, the calculation formula of the action time of the basic vector is:

In a sixth possible implementation manner, combined with the first aspect, the calculation formula of the virtual small vector is:

Among them, V' _S1 represents a virtual small vector; V _S1+ represents a positive small vector; V _S1- represents a negative small vector.

In the seventh possible implementation method, combined with the first aspect, the calculation formula of the virtual vector is:

Among them, V′ _M represents the virtual medium vector; V _S1+ represents the positive small vector in one direction; V _S2+ represents the positive small vector in the other direction; V _M represents the medium vector in the space vector diagram; ξ represents the virtual space vector allocation. coefficient.

In an eighth possible implementation manner, combined with the first aspect, the setting value is 2/3.

In the second aspect, a space vector pulse width modulation device based on virtual space vectors is provided, including:

A space vector diagram acquisition unit is used to obtain a space vector diagram corresponding to the voltage of the three-phase inverter circuit within a switching cycle; the space vector diagram includes: six sectors;

A virtual small vector calculation unit, used to calculate virtual small vectors based on the vector sum of positive small vectors and negative small vectors in the space vector diagram;

A virtual mid-vector calculation unit, used to calculate the virtual mid-vector based on the virtual space vector distribution coefficient, two positive small vectors in different directions in the space vector diagram, and the mid-vector in the space vector diagram;

The first time calculation unit is used for calculating the action time of the basic vector based on the overmodulation compensation coefficient if the reference voltage vector is in the overmodulation I zone and the amplitude of the reference voltage vector is greater than the set value for any sector; Basic vectors, including: virtual small vectors, virtual medium vectors and large vectors in space vector diagrams;

The second time calculation unit is used to calculate the basic vector based on the amplitude phase hybrid compensation method for any sector, if the reference voltage vector is in the overmodulation I zone and the amplitude of the reference voltage vector is less than or equal to the set value. action time;

The third time calculation unit is used to calculate the action time of the basic vector based on simultaneous amplitude and phase compensation for any sector, if the reference voltage vector is in the overmodulation II area;

The pulse width modulation unit is used to perform space vector pulse width modulation according to the action time of the basic vector within a switching cycle.

According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

The embodiment of the present invention reduces the midpoint potential fluctuation caused by the original small vector by calculating a virtual small vector to replace the original small vector in the space vector diagram; according to the virtual space vector distribution coefficient and two positive small vectors in different directions and the original medium vector Calculate the virtual neutral vector and replace the original neutral vector with the virtual neutral vector, retaining the neutral vector's participation in the synthesis of the reference voltage vector, ensuring the characteristics of the three-level converter and reducing the harmonics and distortion of the output voltage.

Description of the drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the drawings of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is a flow chart of a space vector pulse width modulation method based on virtual space vectors provided by an embodiment of the present invention;

Figure 2 is a schematic structural diagram of a three-level inverter;

Figure 3 is the original space vector diagram of the three-level inverter;

Figure 4 is a schematic diagram of the division of areas in a sector when the virtual vector allocation coefficient ξ>2/3;

Figure 5 is a schematic diagram of the division of areas in a sector when the virtual vector allocation coefficient ξ<2/3;

Figure 6 is a motion trajectory diagram when the virtual vector distribution coefficient ξ>2/3 and the reference voltage vector falls in the overmodulation I zone;

Figure 7 is a motion trajectory diagram when the virtual vector distribution coefficient ξ<2/3 and the reference voltage vector falls in the overmodulation I zone;

Figure 8 is a motion trajectory diagram for controlling the reference voltage vector in the overmodulation II area;

Figure 9 is a schematic structural diagram of a space vector pulse width modulation device based on virtual space vectors provided by yet another embodiment of the present invention;

Figure 10 is a schematic structural diagram of yet another space vector pulse width modulation device based on virtual space vectors provided by yet another embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

An embodiment of the present invention provides a space vector pulse width modulation method based on virtual space vectors, as shown in Figure 1, including:

S101. Obtain a space vector diagram corresponding to the voltage of the three-phase inverter circuit within a switching cycle; the space vector diagram includes: six sectors.

Among them, the output performance of the three-level inverter mainly depends on the modulation algorithm. Since SVPWM technology has the advantages of easy digital implementation, high voltage utilization and low harmonic content of the output waveform, in the three-level inverter circuit, Its switching state can be illustrated using a space vector diagram.

For example, the space vector area is evenly divided into six sectors counterclockwise, including a first sector, a second sector, a third sector, a fourth sector, a fifth sector and a sixth sector. Each sector is divided into five cells, and each sector includes a zero vector; two small vectors, a virtual composite medium vector, and two large vectors; each small vector includes a positive small vector and a negative small vector.

S102. Calculate the virtual small vector according to the vector sum of the positive small vector and the negative small vector in the space vector diagram.

The calculation formula of the virtual small vector is:

Among them, V' _S1 represents a virtual small vector; V _S1+ represents a positive small vector; V _S1- represents a negative small vector.

In this step, the mean of the vector sum of the original positive small vector and the original negative small vector is used to replace the original small vector to reduce the midpoint potential fluctuation caused by the original small vector.

S103. Calculate the virtual middle vector according to the virtual space vector distribution coefficient, two positive small vectors in different directions in the space vector diagram, and the middle vector in the space vector diagram.

The calculation formula of the virtual vector is:

Among them, V′ _M represents the virtual medium vector; V _S1+ represents the positive small vector in one direction; V _S2+ represents the positive small vector in the other direction; V _M represents the medium vector in the space vector diagram; ξ represents the virtual space vector allocation. coefficient.

In this step, the vector sum of the original positive small vectors (V _S1+ and V _S2+ ) and the original mid vector (V _M ) in different directions is used to replace the original mid vector, and the mid vector is retained to participate in the synthesis of the reference voltage vector to ensure a three-level converter. characteristics to reduce the harmonics of the output voltage.

S104. For any sector, if the reference voltage vector is in the overmodulation I zone and the amplitude of the reference voltage vector is greater than the set value, calculate the action time of the basic vector based on the overmodulation compensation coefficient; the basic vector includes: virtual Small vectors, virtual medium vectors, and large vectors in space vector diagrams.

First, the modulation area of the reference voltage is introduced. The modulation area is divided into modulation I area and modulation II area based on the value of the reference voltage modulation ratio M. When 0.907<M<0.9535, the reference voltage falls in the over-modulation I area; when M >0.9535, the reference voltage falls in the overmodulation II zone.

S104, specifically including:

If the movement trajectory of the reference voltage vector in a certain sector is in a nonlinear area, the action time of the basic vector is calculated based on the switching period, the action time of the neutral vector and the rotation angle; if the movement trajectory of the reference voltage vector in a certain sector is a linear region, then the action time of the basic vector is calculated based on the overmodulation compensation coefficient.

Among them, when the reference voltage vector is in the overmodulation I area, the amplitude of the reference voltage vector is greater than the set value, and the motion trajectory of the reference voltage vector in a certain sector is a nonlinear area, the calculation formula for the action time of the basic vector is:

in, Indicates the action time of the virtual vector;/> Represents the action time of a large vector;/> represents the action time of the virtual small vector; T _S represents the switching period; θ represents the rotation angle.

Among them, when the reference voltage vector is in the overmodulation I area, the amplitude of the reference voltage vector is greater than the set value, and the motion trajectory of the reference voltage vector in a certain sector is a linear area, the calculation formula for the action time of the basic vector is:

Among them, eta represents the over-modulation compensation coefficient; Indicates the action time of the virtual vector before compensation;/> Indicates the action time of the virtual small vector before compensation;/> Indicates the action time of the large vector before compensation.

It should be noted that T is the action time before compensation, and T' is the action time after compensation, that is They are all corresponding to the action time of each vector after overmodulation compensation. Subsequent space vector pulse width modulation is performed according to this action time, which can ensure the characteristics of the three-level converter and reduce the harmonics and distortion of the output voltage.

In addition, as an example, the setting value may be 2/3.

S105. For any sector, if the reference voltage vector is in the overmodulation I zone and the amplitude of the reference voltage vector is less than or equal to the set value, calculate the action time of the basic vector based on the amplitude phase hybrid compensation method. Specifically include:

If the movement trajectory of the reference voltage vector in a certain sector is in a nonlinear area, the action time of the basic vector is calculated based on the switching period, the action time of the neutral vector and the rotation angle; if the movement trajectory of the reference voltage vector in a certain sector is a linear area, then the action time of the basic vector is calculated based on the overmodulation compensation coefficient; if the motion trajectory of the reference voltage vector in a certain sector is a linear compensation area, the amplitude-phase hybrid compensation method is used to calculate the action time of the basic vector .

Among them, if the reference voltage vector is in the overmodulation I area, the amplitude of the reference voltage vector is less than or equal to the set value, and the motion trajectory of the reference voltage vector in a certain sector is a linear compensation area, the calculation formula of the action time of the basic vector is for:

S106. For any sector, if the reference voltage vector is in the overmodulation II area, calculate the action time of the basic vector based on simultaneous amplitude and phase compensation.

S107. Within a switching cycle, perform space vector pulse width modulation according to the action time of the basic vector.

This embodiment reduces the algorithm module of the controller, has simple control, does not increase the hardware structure, increases the modulation range and improves the DC bus utilization, reduces the fluctuation and imbalance of the midpoint potential, and reduces the output voltage harmonics and distortion. .

An example is given below, and the space vector pulse width modulation method based on virtual space vectors is further described in detail with reference to Figures 2 to 8.

First, the three-level inverter is introduced.

Referring to Figure 2, the three-level inverter has three bridge arms of the ABC phase. The main circuit of each bridge arm is composed of four controllable power switching tubes IGBT, and by changing the four IGBTs in different on-off states, Each bridge arm can be made to work in the following three states:

①0-That is, zero level. The bridge arm outputs 0 level at this time. The status of the switch tube from top to bottom is 0110, 1 means off, and 0 means on;

②N- means low (negative) level. The bridge arm outputs -V _dc /2 level at this time, the status of the switch tube is 0011 respectively, and V _dc is the DC side voltage output by the converter;

③P- is the high (positive) level. The bridge arm outputs V _dc /2 level at this time, and the switching tube status is 1100 respectively.

Therefore, 000 means that the working status of the three bridge arms of ABC are all at 0 level. Similarly, PPN means that phase A and B are at high level and phase C is at low level.

At the same time, 000/NNN/PPP corresponds to the 0 vector in the original vector space, and PPN/PNN corresponds to the large vector in the element vector space.

Taking phase A as an example, as shown in Figure 2, phase A has four controllable power switch tubes, namely S _A1 , S _A2 , S _A3 and S _A4 . There are three working states of phase A: P high level, 0 zero level, N low level, corresponding to the switch tubes respectively: PS _A1 , S _A2 are on, S _A3 , S _A4 are off; 0-S _A2 , S _A3 On, S _A1 and S _A4 are off; NS _A1 and S _A2 are off, S _A3 and S _A4 are on.

The original space vector diagram of the three-level inverter is shown in Figure 3. The original space vector diagram is divided into 6 large sectors, and the voltage vector (small vector, medium vector and large vector) status corresponding to each sector is shown in Table 1.

Table 1 Voltage vector state table

This example includes the following steps for the space vector pulse width modulation process based on virtual space vectors:

(1) Figures 4 and 5 correspond to the schematic diagrams of the area division of the reference voltage vector's motion trajectory in the first sector under two typical virtual vector distribution coefficients. By redefining the virtual middle vector and small vector, the midpoint potential balance is achieved and the three parameters are retained. Level characteristics, reducing harmonics.

As shown in Figure 4 and Figure 5, the mean of the sum of the original positive and negative small vectors is used to replace the original small vector:

Compared with the traditional SVPWM modulation algorithm, positive and negative small vectors in the same direction exist simultaneously during the PWM modulation process, so that the midpoint currents caused by the appearance of the positive and negative small vectors cancel each other out within the cycle, thus suppressing the current caused by the small vectors. The fluctuation problem of midpoint potential.

Use the sum of the original midvector and the original positive small vectors in different directions to replace the original midvector:

Among them, when two original negative small vectors in different directions participate in modulation, they will produce midpoint current vectors of two different phase currents. The synthesized equivalent current vector in the period is in the opposite direction to the midpoint current vector generated by the original midpoint vector. Therefore, the midpoint current generated by the original neutral vector is offset to a certain extent, thereby suppressing the fluctuation of the midpoint potential caused by the neutral vector.

The original neutral vector is retained when synthesizing the virtual neutral vector, so that the converter retains the three-level characteristics and does not introduce harmonics.

The virtual vector distribution coefficient is introduced to dynamically adjust the proportion of the original middle vector and the original positive and negative small vectors in the synthesized virtual vector according to the change of the reference voltage vector, further suppressing the fluctuation of the midpoint potential.

(2) Figures 6 and 7 show the movement trajectories of the reference voltage vector in the over-modulation zone I based on the virtual vector space coordinates, and Figure 8 shows the movement trajectories of the reference voltage vector based on the virtual vector space coordinates in the over-modulation II zone respectively. The overmodulation I area adopts the voltage vector amplitude and phase mixed compensation method, and the overmodulation II area adopts the voltage vector amplitude and phase simultaneous compensation method.

In Figure 6 and Figure 7, θ' is the dividing angle between the nonlinear region BC segment and the linear region OA and OD when the reference voltage vector V _ref falls in the overmodulation II region. The specific physical meaning is that with O as the center, |V _ref | is the angle at the intersection of the circle with radius and triangle AOD. θ1' is the boundary angle between the nonlinear zone BC segment and the linear zone BB', CC' when the reference voltage vector V _ref falls in the overmodulation I zone and the virtual vector distribution coefficient ξ<2/3. Its physical meaning is the same as θ' same. θ2' is the boundary angle between the linear area BB', CC' and the linear compensation area OA', OD' when the reference voltage vector V _ref falls in the over-modulation I area and the virtual vector distribution coefficient ξ<2/3, the specific physical meaning is the angle at the intersection of a circle with O as the center and |V _ref | as the radius and the dividing line of small sectors 4 and 5 (the straight line where A'B' is located).

As shown in Figure 6 to Figure 8, the thick solid line is the motion trajectory of the reference voltage vector set in the overmodulation I area, and the dotted arc is the original motion trajectory of the reference voltage vector. Combined with the virtual vector distribution coefficient: when the reference voltage vector amplitude When it is larger (ξ>2/3), the motion trajectory of the reference voltage vector in the first sector can be divided into linear areas AB, CD and nonlinear area BC. Compared with the original motion trajectory, the BC segment falls on the six sides of the linear modulation. On the boundary of the shape, the original modulation algorithm can be used to synthesize the reference voltage vector. When the voltage vector falls on the COB, it can be compensated for the BC segment, synthesized from the basic vectors V′ _S1 , V′ _M and V _L1 ( _VPPN ) ( Rotation angle θ<30°), or synthesized by basic vectors V′ _S2 , V′ _M and V _L2 (V _PNN ) (rotation angle θ>60°), and the action time is respectively

Sure. V _L1 (V _PPN ) is a large vector in one direction, that is, phase A and B work in the P high-level state, and phase C works in the N low-level state; V _L2 (V _PNN ) is the vector in the other direction. Big vector. Represents the action time of another large vector V _L2 that is different from the direction of the large vector V _L1 ;/> Indicates the action time of another virtual small vector V′ _S2 with a direction different from that of the virtual small vector V′ _S1 . T _S represents the switching cycle, that is, the opening and closing time of the three-phase controllable power switch tube.

The resulting resulting voltage vector amplitude decreases. The AB and CD sections are inside the linear modulation hexagon and have a large voltage amplitude adjustment margin. The over-modulation compensation coefficient η is introduced, and the formula is:

M represents the modulation ratio of the reference voltage vector. Where |V _ref | is the amplitude of the converter reference voltage.

The action time of the voltage vectors in segments AB and CD can be expressed by compensation coefficients respectively as:

Indicates the action time before compensation of another virtual small vector V _S ′ ₂ with a direction different from that of the virtual small vector V _S ′ ₁ , Indicates the action time before compensation of another large vector V _L2 with a direction different from that of the large vector V _L1 .

The voltage amplitude margin is used to compensate for the reference voltage amplitude loss in the BC segment, so that the amplitude of the voltage vector output by the modulation algorithm is maximized and stable within the cycle, reducing harmonics; when the reference voltage vector amplitude is small (ξ< 2/3), the motion trajectory of the reference voltage vector in the first sector can be divided into nonlinear area BC, linear area B'B, C'C and linear compensation area OA', OD', BC, B'B and C The modulation strategy in segment C is the same as when ξ>2/3. When the reference voltage vector falls in the 3 and 4 regions, the voltage amplitude adjustment margin is small. Amplitude and phase hybrid compensation is used, and the original length vector is used to represent the reference voltage vector. , the action times are:

(2) As shown in Figure 8, the thick solid line is the motion trajectory of the reference voltage vector set in the overmodulation II area, and the dotted arc is the original motion trajectory of the reference voltage vector. The motion trajectory of the reference voltage vector in the first sector can be It is divided into linear compensation areas OA, OD and nonlinear area BC. The BC section has the same modulation strategy as the overmodulation I area nonlinear area; when the reference voltage vector falls on the sector AOB and COD (still a linear modulation area), the reference voltage amplitude The adjustment margin is too small to compensate for the voltage loss in the BC segment. The amplitude and phase simultaneous compensation strategy is adopted - OA and OD replace the original reference voltage vector motion trajectory to correct the voltage vector within the cycle.

In this embodiment, the virtual vector distribution coefficient is used to adjust the proportion of the original small and medium vectors in the virtual small and medium vector synthesis according to the reference voltage vector amplitude, so as to maximize the offset of the influence of the original medium vector on the midpoint potential; an optimized dual-mode overmodulation algorithm is used to partition the Consider the over-modulation problem to improve the utilization of DC voltage and reduce the output voltage distortion; use the over-modulation compensation coefficient to compensate the output voltage amplitude and reduce distortion; use the amplitude and phase angle hybrid compensation of the reference voltage in the over-modulation I area to reduce over-modulation The strategy of simultaneously compensating the reference voltage amplitude and phase angle in zone II achieves maximum compensation for the reference voltage drop caused by over-modulation time allocation.

The space vector pulse width modulation method based on virtual space vectors in the above embodiment has the following advantages:

1) Introduce a virtual vector distribution coefficient, replace the traditional SVPWM switch state vector with a dynamic virtual space vector, and achieve the suppression of midpoint potential fluctuations in the over-modulation area without adding hardware; 2) Combine the virtual vector distribution coefficient with optimized over-modulation The algorithm is combined to further compensate for the reference voltage drop under high modulation ratio; 3) The nearest three vector (NTV) principle is still used to synthesize the reference voltage vector in the over-modulation area to ensure the three-level characteristics of the converter and effectively reduce the output voltage harmonics. ; 4) Through the algorithm of this technical solution, the distortion of the converter output voltage is effectively reduced; 5) Through the algorithm of this technical solution, the utilization rate of DC voltage is effectively improved.

Yet another embodiment of the present invention provides a space vector pulse width modulation device based on virtual space vectors, as shown in Figure 9, including:

The space vector diagram acquisition unit 011 is used to obtain a space vector diagram corresponding to the voltage of the three-phase inverter circuit within a switching cycle; the space vector diagram includes: six sectors.

The virtual small vector calculation unit 012 is used to calculate the virtual small vector according to the vector sum of the positive small vector and the negative small vector in the space vector diagram.

The virtual mid-vector calculation unit 013 is used to calculate the virtual mid-vector based on the virtual space vector distribution coefficient, two positive small vectors in different directions in the space vector diagram, and the mid-vector in the space vector diagram.

The first time calculation unit 014 is used for calculating the action time of the basic vector based on the overmodulation compensation coefficient if the reference voltage vector is in the overmodulation I zone and the amplitude of the reference voltage vector is greater than the set value for any sector; so The basic vectors include: virtual small vectors, virtual medium vectors and large vectors in space vector diagrams.

The second time calculation unit 015 is used for any sector, if the reference voltage vector is in the over-modulation I zone and the amplitude of the reference voltage vector is less than or equal to the set value, then calculate the basic value based on the amplitude-phase hybrid compensation method. Vector action time.

The third time calculation unit 016 is used for calculating the action time of the basic vector based on simultaneous amplitude and phase compensation for any sector, if the reference voltage vector is in the overmodulation II area.

The pulse width modulation unit 017 is used to perform space vector pulse width modulation according to the action time of the basic vector within a switching cycle.

The above-mentioned modulation equipment can be used in inverters, uninterruptible power supplies (Uninterruptible PowerSupply, UPS) and static var compensators (Static Var Compensator, SVC) and other occasions.

The space vector pulse width modulation device provided by the embodiment of the present invention replaces the original small vector in the space vector diagram by calculating a virtual small vector, thereby reducing the midpoint potential fluctuation caused by the original small vector; according to the virtual space vector allocation coefficient and two different The positive small vector in the direction and the original middle vector calculate the virtual middle vector, and the virtual middle vector replaces the original middle vector, retaining the middle vector's participation in the synthesis of the reference voltage vector, ensuring the characteristics of the three-level converter and reducing the output voltage harmonics and distortion.

Yet another embodiment of the present invention provides a space vector pulse width modulation device based on virtual space vectors. As shown in Figure 10, the device includes:

Processor 021, Communications Interface 022, Memory 023, Control Bus 024.

The processor 021, the communication interface 022, and the memory 023 complete communication with each other through the control bus 024.

Communication interface 022 is used to communicate with network elements.

The processor 021 is configured to execute the program 025. Specifically, it can execute the relevant steps in the method embodiment shown in Figure 1.

Sampling unit 026, and inverter unit 027. Sampling unit 026 is used to obtain current data information and voltage data information of the external power grid. Inverter unit 027 is used to execute the output result of the target vector in space vector pulse width modulation to form control loop to obtain the output voltage value.

Specifically, program 025 may include program code including computer operating instructions.

The processor 021 may be a central processing unit CPU, or an application specific integrated circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present invention.

Memory 023 is used to store program 025. The memory 023 may include high-speed RAM memory, and may also include non-volatile memory (non-volatile memory), such as at least one disk memory. Program 025 may specifically include:

Obtain the space vector diagram corresponding to the voltage of the three-phase inverter circuit within a switching cycle; the space vector diagram includes: six sectors;

Calculate virtual small vectors based on the vector sum of positive small vectors and negative small vectors in the space vector diagram;

Calculate the virtual middle vector according to the virtual space vector distribution coefficient, two positive small vectors in different directions in the space vector diagram, and the middle vector in the space vector diagram;

For any sector, if the reference voltage vector is in the overmodulation I zone and the amplitude of the reference voltage vector is greater than the set value, the action time of the basic vector is calculated based on the overmodulation compensation coefficient; the basic vector includes: virtual small vector , virtual vectors and large vectors in space vector diagrams;

For any sector, if the reference voltage vector is in the overmodulation I zone and the amplitude of the reference voltage vector is less than or equal to the set value, the action time of the basic vector is calculated based on the amplitude phase hybrid compensation method;

For any sector, if the reference voltage vector is in the overmodulation II area, the action time of the basic vector is calculated based on the simultaneous amplitude and phase compensation method;

Within a switching cycle, space vector pulse width modulation is performed according to the action time of the basic vector.

For the specific implementation of each module in program 025, please refer to the corresponding module in the embodiment shown in Figure 9, and will not be described again here.

The space vector pulse width modulation device provided by the embodiment of the present invention replaces the original small vector in the space vector diagram by calculating a virtual small vector, thereby reducing the midpoint potential fluctuation caused by the original small vector; according to the virtual space vector allocation coefficient and two different The positive small vector in the direction and the original middle vector calculate the virtual middle vector, and the virtual middle vector replaces the original middle vector, retaining the middle vector's participation in the synthesis of the reference voltage vector, ensuring the characteristics of the three-level converter and reducing the output voltage harmonics and distortion.

In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of the units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components may be combined or can be integrated into another system, or some features can be ignored, or not implemented. On the other hand, the connections shown or discussed may be through some interfaces, which may be electrical, mechanical or other forms.

In addition, in the devices and systems in various embodiments of the present invention, each functional unit can be integrated into one processing unit, each unit can be physically included separately, or two or more units can be integrated into one unit. And each of the above units can be implemented in the form of hardware or in the form of hardware plus software functional units.

All or part of the steps to implement the above method embodiments can be completed by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When the program is executed, the steps including the above method embodiments are executed; The aforementioned storage media include: U disk, mobile hard disk, read only memory (ROM), random access memory (RAM), magnetic disk or optical disk, etc. that can store program code. medium.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention. should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims (5)

1. A space vector pulse width modulation method based on virtual space vectors, comprising:

acquiring a space vector diagram corresponding to the voltage of the three-phase inverter circuit in one switching period; the space vector diagram comprises: six sectors;

calculating a virtual small vector according to the vector sum of the positive small vector and the negative small vector in the space vector diagram;

calculating a virtual middle vector according to the virtual space vector distribution coefficient, the positive small vectors in two different directions in the space vector diagram and the middle vector in the space vector diagram;

for any sector, if the reference voltage vector is in the overmodulation I region and the amplitude of the reference voltage vector is larger than a set value, calculating the acting time of the basic vector based on the overmodulation compensation coefficient; the base vector includes: virtual small vectors, virtual medium vectors and large vectors in the space vector diagram;

if the motion track of the reference voltage vector in a certain sector is a nonlinear region, calculating the action time of the basic vector according to the switching period, the action time of the intermediate vector and the rotation angle:

；

wherein,representing the time of action of the virtual vector; />Representing the time of action of the large vector; />Representing the time of action of the virtual small vector; />Representing a switching period; />Indicating the rotation angle;

if the motion track of the reference voltage vector in a certain sector is a linear region, calculating the acting time of the basic vector according to the overmodulation compensation coefficient:

；

wherein,representing the time of action of the virtual vector; />Representing the time of action of the large vector; />Representing the time of action of the virtual small vector;ηrepresenting an overmodulation compensation coefficient; />Representing the time of action of the vector in the virtual before compensation; />Representing the action time of the virtual small vector before compensation; />Representing the time of action of the large vector before compensation;

for any sector, if the reference voltage vector is in the overmodulation I region and the amplitude of the reference voltage vector is smaller than or equal to a set value, calculating the acting time of the basic vector based on an amplitude-phase hybrid compensation mode;

if the motion track of the reference voltage vector in a certain sector is a nonlinear region, calculating the acting time of the basic vector according to the switching period, the acting time of the middle vector and the rotation angle;

if the motion track of the reference voltage vector in a certain sector is a linear region, calculating the acting time of the basic vector according to the overmodulation compensation coefficient;

if the motion trail of the reference voltage vector in a certain sector is a linear compensation area, calculating the acting time of the basic vector by adopting an amplitude-phase hybrid compensation mode:

；

wherein,representing the time of action of the virtual vector; />Representing the time of action of the large vector; />Representing the time of action of the virtual small vector; />Representing a switching period;

for any sector, if the reference voltage vector is in the overmodulation II area, calculating the acting time of the basic vector based on the mode of amplitude phase simultaneous compensation;

and in one switching period, performing space vector pulse width modulation according to the action time of the basic vector.

2. The space vector pulse width modulation method based on the virtual space vector according to claim 1, wherein the calculation formula of the virtual small vector is:

；

wherein,representing a virtual small vector; />Representing a positive small vector; />Representing a negative small vector.

3. The space vector pulse width modulation method based on virtual space vector according to claim 1, wherein the calculation formula of the virtual middle vector is:

；

wherein,representing a virtual mid-vector; />Representing a positive small vector in one direction; />Representing a positive small vector in the other direction;V _M representing a middle vector in the space vector diagram; />Representing the virtual space vector allocation coefficients.

4. The space vector pulse width modulation method based on the virtual space vector according to claim 1, wherein the set value is 2/3.

5. A space vector pulse width modulation apparatus based on a virtual space vector, to which the space vector pulse width modulation method according to any one of claims 1 to 4 is applied, comprising:

the space vector diagram acquisition unit is used for acquiring a space vector diagram corresponding to the voltage of the three-phase inverter circuit in one switching period; the space vector diagram comprises: six sectors;

a virtual small vector calculation unit for calculating a virtual small vector from the vector sum of the positive small vector and the negative small vector in the space vector diagram;

the virtual middle vector calculation unit is used for calculating a virtual middle vector according to the virtual space vector distribution coefficient, the positive small vectors in two different directions in the space vector diagram and the middle vector in the space vector diagram;

the first time calculation unit is used for calculating the acting time of the basic vector based on the overmodulation compensation coefficient if the reference voltage vector is in the overmodulation I area and the amplitude of the reference voltage vector is larger than a set value for any sector; the base vector includes: virtual small vectors, virtual medium vectors and large vectors in the space vector diagram;

the second time calculation unit is used for calculating the acting time of the basic vector based on the mode of amplitude-phase hybrid compensation if the reference voltage vector is in the overmodulation I area and the amplitude of the reference voltage vector is smaller than or equal to a set value for any sector;

the third time calculating unit is used for calculating the acting time of the basic vector based on the mode of amplitude phase simultaneous compensation if the reference voltage vector is in the overmodulation II area for any sector;

and the pulse width modulation unit is used for carrying out space vector pulse width modulation according to the action time of the basic vector in one switching period.