CN103944438B - A kind of quickly n level multi-electrical level inverter space vector modulation algorithm - Google Patents

Abstract

The invention discloses a kind of quickly n level multi-electrical level inverter space vector modulation algorithm.This algorithm is by building the constraint function under specified conditions, the Linear Equations mapped between basic vector and switch state vector in SVPWM algorithm is converted to homogeneous equation group, by solving new homogeneous equation group, i.e. can get unique switch state vector that basic vector under the conditions of particular constraints is corresponding, avoid finding suitable switch state vector corresponding to basic vector from multiple Redundanter schalter state vectors, it is achieved basic vector correspondence switch state vector quick, accurately calculate.This algorithm simplifies cascaded multilevel inverter SVPWM algorithm so that SVPWM algorithm is applicable to any n level multi-electrical level inverter, contributes to SVPWM algorithm and is applied to n level multi-electrical level inverter.

Description

A kind of quickly n level multi-electrical level inverter space vector modulation algorithm

Technical field

The present invention relates to cascaded multilevel inverter modulation field, refer in particular to a kind of quickly n level multi-electrical level inverter empty Between Vector Modulation (be called for short SVPWM) algorithm.

Background technology

Voltage stress on cascaded multilevel inverter switching device is little, the degree of modularity is high, be prone to extension and control, can Good by property, harmonic wave of output voltage distortion factor is little, failure tolerant ability is strong, it realizes the big merit of high pressure with low-voltage power electronic device Rate electric energy is changed, and can be applicable to D.C. high voltage transmission, STATCOM and Active Power Filter-APF, photovoltaic generation and fuel In the high pressure higher power device such as the energy source regeneration apparatus such as cell power generation and high-power high voltage frequency conversion motor driving.

Space vector pulse width modulation (SVPWM) technology is Sinusoidal Pulse Width Modulation (SPWM) technology and motor magnetic A kind of PWM control technology that logical chain circular trace directly combines, this modulation technique has DC voltage utilization rate height, switching frequency The advantages such as low, switching loss is little, are applied to cascaded multilevel inverter about SVPWM technology and cause the close of Chinese scholars Pay close attention to.

Current cascaded multilevel inverter SVPWM technology is nearly all that three-phase reference voltage is converted into a certain specific two dimension Reference voltage vector in coordinate system, then according to voltage-second balance principle, utilizes the basic vector in two-dimensional coordinate to approach reference Voltage vector, by calculating the threephase switch state vector that in two dimensional surface coordinate system, basic vector is corresponding, with threephase switch shape State vector controls the output of three-phase inverter, it is achieved space vector modulation.Being calculated threephase switch state vector by basic vector is One Linear Equations, the solution of Linear Equations has infinite, it is considered to practical cascade inversion unit number is limited Constraint, available limited solves, and i.e. there is corresponding multiple switch state vectors (the referred to as Redundanter schalter state of a basic vector Vector).Due to the existence of Redundanter schalter state vector, in currently practical application, space vector modulation algorithm is limited in three grades In following cascaded inverter.

Along with the increase of cascade inversion unit number n, the Redundanter schalter state vector quantity that basic vector is corresponding will increase Adding, how selecting most suitable switch state vector from multiple switch state vectors quickly and accurately is that cascade connection multi-level is inverse Become the key issue of device space vector modulation algorithm.

Summary of the invention

It is an object of the invention to the problems referred to above existed for current n level multi-electrical level inverter space vector modulation algorithm, Proposing a kind of quickly n level multi-electrical level inverter space vector modulation algorithm, this algorithm need not calculate a basic vector Corresponding all switch state vectors, only on the basis of SVPWM algorithm defines, by the method building constraint function, The Linear Equations mapped between basic vector and switch state vector in SVPWM algorithm is converted to homogeneous equation group, Solve new homogeneous equation group, i.e. can get the switch state vector that basic vector under the conditions of particular constraints is corresponding.This algorithm letter Change cascaded multilevel inverter SVPWM algorithm so that SVPWM algorithm is applicable to any n level multi-electrical level inverter.

For reaching above-mentioned purpose, the technical scheme is that

A kind of quickly n level multi-electrical level inverter space vector modulation algorithm, comprises the following steps:

The first step, the tradition basic vector of SVPWM algorithm with the mapping function of switch state vector is:

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

From formula (1) it can be seen that basic vector (α, β) is distributed on non-integer coordinates point, and due to formula (1) right and wrong System of homogeneous linear equations, (c) there is redundancy in a, b to switch state vector.

Second step, rotationally-varying by coordinate, it is α ', β ' coordinate α, β Coordinate Conversion so that basic vector is distributed in On the rounded coordinate point of α ', β ' plane, basic vector (α ', β ') and switch state vector under α ', β ' coordinate (a, b, c) between Mapping function is:

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

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

F [a, b, c, Φ (t)]=C (3)

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

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

5th step, calculates, according to the sampling number in a cycle, the switch state vector that each basic vector is corresponding.

Compared with prior art, the such scheme of the present invention, only according to desired output voltage performance index and inverter The requirement structure constraint function of performance, simultaneous constraint function can calculate corresponding unique of each basic vector with mapping function Switch state vector, it is not necessary to calculate Redundanter schalter state vector, simplifies the workload of SVPWM algorithm, improves SVPWM The speed of algorithm.

Accompanying drawing explanation

Fig. 1 is the enforcement flow chart of steps of the present invention.

Detailed description of the invention

As a example by three grade of seven electrical level inverter.Basic vector (α ', β ') and switch state vector under α ', β ' coordinate (a, b, C) mapping function between is:

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

The residual voltage of desired output three-phase voltage is minimum, i.e. 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 i.e. can get unique switch state vector that any basic vector is corresponding.

Claims (4)

1. a quick n level multi-electrical level inverter space vector modulation algorithm, it is characterised in that: this algorithm is based on rotational coordinates Conversion and particular constraints function, in the new coordinate system of rotating coordinate transformation, basic vector is entirely located in rounded coordinate point, Under new coordinate, the mapping function between basic vector and switch state vector is:This algorithm Achieve the quick location of the switch state vector of cascaded multilevel inverter space vector modulation algorithm.

2. the most quick n level multi-electrical level inverter space vector modulation algorithm, it is characterised in that according to inversion Device desired output voltage performance index and the requirement of inverter performance, structure constraint function f [a, b, c, Φ (t)]=C.

3. the most quick n level multi-electrical level inverter space vector modulation algorithm, it is characterised in that under new coordinate The homogeneous equation group that mapping function and constraint function form 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.\\ \begin{array}{cc}s.t.& \left|a\right|\≤n,\left|b\right|\≤n,\left|c\right|\≤n\end{array}\end{array}.---\left(1\right)$

4. quickly n level multi-electrical level inverter space vector modulation algorithm as claimed in claim 3, it is characterised in that utilize public affairs Formula (1) can calculate unique switch state vector corresponding to any basic vector (α ', β ') (a, b, c).