CN103944438A - Rapid n-level multi-level inverter space vector pulse width modulation algorithm - Google Patents

Abstract

The invention discloses a rapid n-level multi-level inverter space vector pulse width modulation algorithm. According to the algorithm, the non-homogeneous linear equation system, mapped between a basic vector and switching state vectors, in the SVPWM algorithm is converted into the homogeneous equation system by establishing a constraint function under the specific conditions, the unique switching state vector corresponding to the basic vector under the specific constraint conditions can be obtained by solving the new homogeneous equation system, an appropriate switching state vector corresponding to the basic vector is prevented from being found in multiple redundant switching state vectors, and the switching state vector corresponding to the basic vector can be rapidly and accurately calculated. The n-level multi-level inverter SVPWM algorithm is simplified, and therefore the SVPWM algorithm is suitable for any n-level multi-level inverters, and the SVPWM algorithm can be easily popularized to be applied to the n-level multi-level inverters.

Description

One is n level multi-electrical level inverter space vector modulation algorithm fast

Technical field

The present invention relates to cascaded multilevel inverter modulation field, refer in particular to one n level multi-electrical level inverter space vector modulation (being called for short SVPWM) algorithm fast.

Background technology

Voltage stress on cascaded multilevel inverter switching device is little, the degree of modularity is high, be easy to expansion and control, good reliability, harmonic wave of output voltage distortion factor is little, failure tolerant ability is strong, it realizes the conversion of high-power electric energy with low-voltage power electronic device, can be applicable in the high-power device such as the energy source regeneration apparatus such as high voltage direct current transmission, STATCOM and Active Power Filter-APF, photovoltaic generation and fuel cell power generation and the driving of high-power high voltage variable-frequency motor.

Space vector pulse width modulation (SVPWM) technology is Using Sinusoidal Pulse Width Modulation (SPWM) technology and directly a kind of PWM control technology of combination of motor flux chain circular trace, this modulation technique has the advantages such as direct voltage utilance is high, switching frequency is low, switching loss is little, about SVPWM technology is applied to cascaded multilevel inverter and has caused the close attention of Chinese scholars.

Current cascaded multilevel inverter SVPWM technology is nearly all to convert three-phase reference voltage to reference voltage vector in a certain specific two-dimensional coordinate system, then according to weber equilibrium principle, utilize the basic vector in two-dimensional coordinate to approach reference voltage vector, by calculating threephase switch state vector corresponding to basic vector in two dimensional surface coordinate system, with the output of threephase switch state vector control three-phase inverter, implementation space Vector Modulation.Calculating threephase switch state vector by basic vector is a Linear Equations, the solution of Linear Equations has infinite, consider the limited constraint of practical cascade inversion unit number, can obtain limited and separate, have the corresponding multiple switch state vectors of a basic vector (being called Redundanter schalter state vector).Due to the existence of Redundanter schalter state vector, in current practical application, space vector modulation algorithm is limited in three grades of following cascaded inverters.

The increase of counting n along with cascade inversion unit, the Redundanter schalter state vector quantity that basic vector is corresponding will increase greatly, and how from multiple switch state vectors, selecting quickly and accurately most suitable switch state vector is the key issue of cascaded multilevel inverter space vector modulation algorithm.

Summary of the invention

The object of the invention is the problems referred to above that exist for current n level multi-electrical level inverter space vector modulation algorithm, one n level multi-electrical level inverter space vector modulation algorithm is fast proposed, this algorithm does not need to calculate all switch state vectors that basic vector is corresponding, only on the basis of SVPWM algorithm definition, by building the method for constraint function, the Linear Equations of shining upon between basic vector and switch state vector in SVPWM algorithm is converted to homogeneous equation group, solve new homogeneous equation group, can obtain switch state vector corresponding to basic vector under particular constraints condition.This simplify of arithmetic cascaded multilevel inverter SVPWM algorithm, makes SVPWM algorithm be applicable to any n level multi-electrical level inverter.

For achieving the above object, technical scheme of the present invention is:

One is n level multi-electrical level inverter space vector modulation algorithm fast, comprises the following steps:

The first step, the basic vector of traditional SVPWM algorithm and the mapping function of switch state vector are:

$\begin{array}{c}\left\{\begin{array}{c}\mathrm{\α}=\frac{1}{3}(2a-b-c)\\ \mathrm{\β}=\frac{\sqrt{3}}{3}(b-c)\end{array}\right.\\ s.t.\left|a\right|\≤n,\left|b\right|\≤n,\left|c\right|\≤n\end{array}---\left(1\right)$

Can find out from formula (1), it is upper that basic vector (α, β) is distributed in non-integer coordinates point, and because formula (1) is Linear Equations, switch state vector (a, b, c) exists redundancy.

Second step, change by rotation of coordinate, α, β Coordinate Conversion is α ', β ' coordinate, make basic vector be distributed in α ', the rounded coordinate point of β ' plane is upper, α ', basic vector under β ' coordinate (α ', β ') with the mapping function between switch state vector (a, b, c) be:

$\begin{array}{c}\left\{\begin{array}{c}{\mathrm{\α}}^{\′}=a-c\\ {\mathrm{\β}}^{\′}=-a+b\end{array}\right.\\ s.t.\left|a\right|\≤n,\left|b\right|\≤n,\left|c\right|\≤n\end{array}---\left(2\right)$

The 3rd step, according to the requirement of desired output voltage performance index and inverter performance, structure constraint function

f[a，b，c，Φ(t)]＝C (3)

The 4th step, simultaneous constraint function and α ', the mapping function under β ' coordinate between basic vector and switch state vector obtains:

$\begin{array}{c}\left\{\begin{array}{c}{\mathrm{\α}}^{\′}=a-c\\ {\mathrm{\β}}^{\′}=-a+b\\ f[a,b,c,\mathrm{\Φ}\left(t\right)]=C\end{array}\right.\\ s.t.\left|a\right|\≤n,\left|b\right|\≤n,\left|c\right|\≤n\end{array}---\left(4\right)$

The 5th step, calculates according to the sampling number of one-period the switch state vector that each basic vector is corresponding.

Compared with prior art, such scheme of the present invention, only require structure constraint function according to desired output voltage performance index and inverter performance, simultaneous constraint function can calculate with mapping function unique switch state vector that each basic vector is corresponding, do not need to calculate Redundanter schalter state vector, simplify the workload of SVPWM algorithm, improved the speed of SVPWM algorithm.

Brief description of the drawings

Fig. 1 is implementation step flow chart of the present invention.

Embodiment

Taking three grade of seven electrical level inverter as example.α ', basic vector under β ' coordinate (α ', β ') with the mapping function between switch state vector (a, b, c) be:

$\begin{array}{c}\left\{\begin{array}{c}{\mathrm{\α}}^{\′}=a-c\\ {\mathrm{\β}}^{\′}=-a+b\end{array}\right.\\ s.t.\left|a\right|\≤3,\left|b\right|\≤3,\left|c\right|\≤3\end{array}---\left(5\right)$

The residual voltage minimum of desired output three-phase voltage, constraint function is:

$f[a,b,c,\mathrm{\Φ}\left(t\right)]=\lim \left(\frac{a+b+c}{3}\right)---\left(6\right)$

Simultaneous formula (5) and (6) can obtain:

$\begin{array}{c}\left\{\begin{array}{c}{\mathrm{\α}}^{\′}=a-c\\ {\mathrm{\β}}^{\′}=-a+b\\ f[a,b,c,\mathrm{\Φ}\left(t\right)]=\lim \left(\frac{a+b+c}{3}\right)\end{array}\right.\\ s.t.\left|a\right|\≤3,\left|b\right|\≤3,\left|c\right|\≤3\end{array}---\left(7\right)$

Solve formula (7) and can obtain unique switch state vector that any basic vector is corresponding.

Claims (6)

1. a n level multi-electrical level inverter space vector modulation algorithm fast, is characterized in that: the method for rapidly positioning of the switch state vector of the cascaded multilevel inverter space vector modulation algorithm based under rotating coordinate transformation and particular constraints function condition.

2. n level multi-electrical level inverter space vector modulation algorithm fast as claimed in claim 1, is characterized in that being all positioned at rounded coordinate point through basic vector in the new coordinate system of rotating coordinate transformation.

3. n level multi-electrical level inverter space vector modulation algorithm fast as claimed in claim 1, is characterized in that under new coordinate, the mapping function between basic vector and switch state vector is:

$\begin{array}{c}\left\{\begin{array}{c}{\mathrm{\α}}^{\′}=a-c\\ {\mathrm{\β}}^{\′}=-a+b\end{array}\right.\\ s.t.\left|a\right|\≤n,\left|b\right|\≤n,\left|c\right|\≤n\end{array}---\left(1\right)$

4. n level multi-electrical level inverter space vector modulation algorithm fast as claimed in claim 1, is characterized in that according to the requirement of inverter desired output voltage performance index and inverter performance structure constraint function f [a, b, c, Φ (t)]=C.

5. n level multi-electrical level inverter space vector modulation algorithm fast as claimed in claim 1, is characterized in that under new coordinate, the homogeneous equation group of mapping function and constraint function composition is:

$\begin{array}{c}\left\{\begin{array}{c}{\mathrm{\α}}^{\′}=a-c\\ {\mathrm{\β}}^{\′}=-a+b\\ f[a,b,c,\mathrm{\Φ}\left(t\right)]=C\end{array}\right.\\ s.t.\left|a\right|\≤n,\left|b\right|\≤n,\left|c\right|\≤n\end{array}---\left(2\right)$

6. n level multi-electrical level inverter space vector modulation algorithm fast as claimed in claim 1, it is characterized in that according to the homogeneous equation group of claim 5 can calculate any basic vector (α ', β ') corresponding unique switch state vector (a, b, c).