A method for implementing SVPWM based on sequencing method

Abstract

The application provides an SVPWM implementation method based on a sorting method, which is used for implementing an inverter SVPWM, and is characterized in that: a sorting algorithm is used as a core to synthesize a modulation signal; firstly, the action time distribution of three-way switches in a current sector is calculated, and the action time length is sorted in descending order; secondly, according to the space vector variation law, the sorting of the action time length of the three-way switches in the current sector is calculated; then, the on-off of the switches corresponding to the action time is controlled according to the action time, so that the SVPWM signal synthesis in the current sector is realized. The application changes the algorithm core on the basis of the existing SVPWM implementation algorithm, uses the sorting method, simplifies the calculation mode of the on-off action time of the switches, reduces the calculation amount, is easier to realize digital control, and can improve the SVPWM modulation efficiency.

Description

Technical Field

[0001] The present invention relates to the field of power electronics, and in particular to an SVPWM implementation method based on a sequencing method. Background Art

[0002] SVPWM is widely used in the power electronics industry. The traditional three-level SVPWM (Space Vector Pulse Width Modulation) implementation method determines the sector where the reference voltage is located in a two-dimensional stationary coordinate system, then determines the vector combination at that moment, thereby determining the order and duration of each vector's action. This implementation process involves many calculation steps and complex programming.

[0003] The basic steps of the traditional SVPWM algorithm are: 1) determining the sector where the reference voltage vector is located; 2) calculating the action time of the basic vector in each sector; and 3) determining the switching points of each voltage space vector. The basic steps of the present invention are basically the same as those of the traditional algorithm, but innovative improvements are made to the algorithm implementation of each step.

[0004] In sector judgment, the traditional method constructs the state function based on the sector equivalence conditions of the space vector coordinate system, uses a list and then determines the sector through addition, subtraction and logical operations; in calculating the basic action time of the vector, the vector superposition and equivalence principles are used to calculate the action time of each sector vector separately; when determining the switching point of the voltage space vector, the triangular carrier is compared with the three-phase output voltage waveform to obtain the switching point of the voltage space vector.

[0005] The traditional SVPWM implementation method has many input and output parameters for each node, complex calculation content, complicated relationship conversion nodes, and complex digital control. Summary of the Invention

[0006] Aiming at the complex calculation method of traditional SVPWM, the present invention proposes a new modulation signal synthesis method based on logical comparison. It adopts the normalized duration calculation method to simplify the calculation process of the action state of each switch. Taking into account its periodicity, it can also reduce data calculation by querying the relationship table, thereby facilitating the realization of simple digital control.

[0007] The technical solution adopted by the present invention is: a SVPWM implementation method based on a sorting method, comprising the following steps:

[0008] Step 1: Calculate the switch action duration of each sector and sort them, and construct a descending array of durations;

[0009] Step 2: Sort the length of the on-time of each switch and construct a loop element array;

[0010] Step 3: Allocate the action time of each switch in sequence;

[0011] Fourth step: each switch is turned on and off according to the action time to realize SVPWM signal synthesis;

[0012] Beneficial effects:

[0013] The SVPWM implementation method based on the sorting method provided by the application is based on the traditional seven-segment SVPWM, and the reference voltage space vector angle is normalized to Then the space vector action time is calculated, the descending array is constructed with the time length as the order and the time length and the loop as the elements, the action state of each road switch is determined, and a new type of modulation switch state determination method is provided, so that the SVPWM calculation algorithm is simplified. Due to the periodicity of the vector space, the descending array of the loop time is also periodic, and the mathematical operation can be further reduced by table lookup method, and the modulation efficiency is improved. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a three-phase inverter modulation circuit schematic diagram adopted by the application;

[0015] Figure 2 is a vector superposition principle schematic diagram adopted by the application;

[0016] Figure 3 is a vector space sector division schematic diagram adopted by the application;

[0017] Figure 4 is a timing and switch action state schematic diagram adopted by the application;

[0018] Figure 5 is the S T_Max , S T_Mid , S T_Min switch state of the simulation result of the application;

[0019] Figure 6 is the T_Max, T_Mid, T_Min corresponding switch branch trend of the simulation result of the application;

[0020] Figure 7 is the a, b, c three-way switch state of the simulation result of the application;

[0021] Figure 8 is the voltage state of the simulation result U an , U ao , U ab , U on of the application;

[0022] Figure 9 is the output current state of the three-phase inverter of the simulation result of the application. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part 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 ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] According to an embodiment of the present invention, a novel modulation signal synthesis method based on logic comparison is proposed. According to the space vector angle of the reference voltage, the sector is determined, and then the relevant space vector action time (descending order) is calculated and converted into the action state of the road switch (referring to the first switch S1_g, S2_g, S3_g of each road, see Figure 1 , the same below), and then determine the order of the switch action duration (descending order) based on the space vector change law. The corresponding relationship between the durations can be used to determine the action state of each switch within the sampling period, thereby realizing the synthesis of the SVPWM signal. Specifically, it includes the following four steps:

[0025] Step 1: Calculate the switch action duration of each sector and sort them, and construct a descending array of durations;

[0026] Same as the traditional SVPWM method, see Figure 2 , taking the reference voltage space vector angle θ as a variable, according to the vector superposition principle:

[0027] T0=T z -T1-T2

[0028]

[0029] T2=m*T z sin(θ)

[0030] Among them, the reference voltage space vector angle θ needs to be normalized to m is the modulation parameter, T0, T1, T2 are the action time of zero vector and two non-zero vectors, T z is the sampling period. According to the order of space vector action (U4→U6→U2→U3→U1→U5→U4, see Figure 3 , counterclockwise order), it can be seen that as the space vector changes in the sector, when V1>V2 (V1 is the first counterclockwise space vector in the sector, and V2 is the second counterclockwise space vector), V1(T1) and V2(T2) need to be exchanged to satisfy T1 corresponds to the smaller space vector value and T2 corresponds to the larger space vector value.

[0031] After the exchange, calculate the duration of each switch action and determine the switch status during the action:

[0032]

[0033] t c is the sampling center time, t is the current action time, Si is the state of each switch, the value is 1 during the action time, indicating that the switch is currently on, and the value is 0 during the non-action time, indicating that the switch is currently off, T_Max is the longest switch action time, and the corresponding branch switch state is S T_Max , T_Mid is the middle duration of the switch action, and the corresponding branch switch state is S T_Mid , T_Min is the shortest switch action time, and the corresponding branch switch state is S T_Min ,like Figure 4 As shown. This forms a time length descending array T = [T_Max, T_Mid, T_Min] and a switch state array S = [S T_Max , S T_Mid , S T _ Min ]. Then for the two space vectors V1 and V2 of a sector, we have: S T_Max The corresponding space vector element is always 1, S T_Min The corresponding space vector element is always 0, S T_Mid Then corresponding to the remaining space vector elements (element values ​​0 & 1), Figure 5 The distribution of the switch state array S of the three-way switch over time is given.

[0034] For example, the two space vectors in the first sector are U4 (100) & U6 (110), V1 = U4; V2 = U6, and the space vector action times are T1 and T2 respectively. Since 4 (binary 100) < 6 (binary 110), T1 and T2 do not need to be exchanged, and the first element of the space vector is always 1, and the corresponding switch state is S T_Max ; The second element of the space vector changes from 0 to 1, and the corresponding switch state is S T_Mid ; The third element of the space vector is always 0, and the corresponding switch state is S T_Min .

[0035] Step 2: Sort the length of the on-time of each switch and construct a loop element array;

[0036] Referring to the change order of each space vector, it can be seen that the order of the action time length of each switch changes according to the sine function with respect to the sector number z (0-5), and the phase angle difference is 2π / 3. The positive selection function can be used to fit the order of the three-way action time length, which is:

[0037]

[0038] Construct the path duration array T′=[T′ a , T′ b , T′ c ], T′ i Positively correlated with duration, then T′ i , i=a, b, c corresponding to the array number is element (1, 2, 3), with the action duration T′ i The size of the array is constructed in descending order, that is, the loop element array:

[0039] P=[P max(T′) , P mid(T′) , P min(T′) ], P mid(T′) =6-P max(T′) -P min(T′)

[0040] Among them, P max(T’) Indicates the element number corresponding to the maximum element in the duration array T', P min(T’) Indicates the element number corresponding to the minimum element in the duration array T', P mid(T’) Indicates the element number corresponding to the center element in the duration array T'.

[0041] Figure 6 The changes of the branches corresponding to each time length over time are given. For example, in sector 0, the time length order is (123), which means that branch 1 / a is always 1, branch 2 / b changes from 0 to 1, and branch 3 / c is always 0. Therefore, the space vector is (100)->(110), that is, U4->U6.

[0042] Step 3: Allocate the action time of each switch in sequence;

[0043] Since array T = [T_Max, T_Mid, T_Min] and array P = [P max(T′) , P mid(T′) , P min(T′) ] are sorted in descending order according to the duration of action, so the P i The duration of the circuit switch action is T i , thus the status of each switch can be determined, see Figure 7 .

[0044] Step 4: Each switch is turned on and off according to the action time to realize SVPWM signal synthesis;

[0045] By P i The duration of the road is T i The Pth can be determined according to the switch state array S i The switch status of the road is The three-way switching control is performed according to the timing state to realize the synthesis of SVPWM signals. Figure 8 and Figure 9 , which are the distribution of inverter output voltage and three-phase AC current respectively.

[0046] The method of the present invention simplifies the calculation process of the action status of each switch, and considering its periodicity, it can also reduce data calculation by querying the relationship table, making it easier to achieve simple digital control.

[0047] In order to verify the SVPWM algorithm of the present invention, MATLAB was used for simulation. The simulation model used a DC voltage of 600V, a reference voltage of 320V, and a sampling period of 0.001s for calculation. The simulation results achieved the same processing effect as the classical method and realized the inversion of DC to three-phase AC current. Figure 9 The simulation results show that the proposed method of realizing SVPWM by using the action time sequencing method is feasible and more suitable for digital processing and control. The new method is more direct, has less computational complexity and is more efficient.

[0048] Although the above describes the illustrative specific embodiments of the present invention to facilitate understanding of the present invention by those skilled in the art, and it should be clear that the present invention is not limited to the scope of the specific embodiments, it is obvious to those skilled in the art that as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

Claims

1. A SVPWM implementation method based on a sorting method, characterized in that: The steps include: Step 1: Calculate the switch action duration of each sector and sort them, and construct a descending array of durations; Step 2: Sort the length of the on-time of each switch and construct a loop element array; Step 3: Allocate the action time of each switch in sequence; Step 4: Each switch is turned on and off according to the action time to realize SVPWM signal synthesis; According to the principle of vector superposition: in, Normalized to angle, is the action time of zero vector and two non-zero vectors, T z is the sampling period, m is the modulation parameter; According to the order of space vector action, as the space vector changes in the sector, when calculating the action time, is the first space vector in the counterclockwise direction of the sector, is the second counterclockwise space vector, if > , you need to ( )and ( ) exchange to satisfy Corresponding to the smaller value of the space vector, Corresponding to the larger value of the space vector; After the exchange, calculate the duration of each switch action and determine the switch status during the action: in, is the central sampling time, t is the current action time, S i The value is 1 during the action time, indicating that the switch is currently on. The value is 0 during the non-action time, indicating that the switch is currently off. T_Max is the longest switch action time, and the corresponding branch switch state is S T_Max , T_Mid is the middle duration of the switch action, and the corresponding branch switch state is S T_Mid , T_Min is the shortest switch action time, and the corresponding branch switch state is S T_Min , thus forming a descending array of duration and switch status array , then for two space vectors in a sector and have: The corresponding space vector element is always 1, The corresponding space vector element is always 0, Then it corresponds to the remaining space vector elements; The second step is to sort the on-time lengths of the switches and construct a loop element array, specifically including: Referring to the change order of each space vector, it can be seen that the order of the length of the action time of each switch changes according to the sine function with respect to the sector number z (0-5), and the phase angle difference is , using the positive selection function to fit the three-way action duration sorting, we have: Constructing a road duration array ,in It is positively correlated with the duration of the switch action, and then The corresponding array number is element (1, 2, 3), and the duration of action is The size of the array is constructed in descending order, that is, the loop element array: ， Among them, P max(T’) Indicates the element number corresponding to the maximum element in the duration array T', P min(T’) Indicates the element number corresponding to the minimum element in the duration array T', P mid(T’) Indicates the element number corresponding to the center element in the duration array T'; The third step is to sequentially allocate the action time of each switch, specifically including: Since the array and arrays They are sorted in descending order according to the duration of action, so The duration of the switch action of the circuit is , thus the status of each switch can be determined; The fourth step of switching on and off each switch according to the action time to realize SVPWM signal synthesis specifically includes: Depend on The duration of the road is According to the switch state array Determine the The switch status of the road is , the three-way switching control is performed according to the timing state, thereby realizing the synthesis of SVPWM signals.

Images