CN102082522B - Voltage step controlling method and step wave cascade multilevel inverter - Google Patents

Abstract

The present invention discloses a voltage step controlling method and a step wave cascade multilevel inverter, wherein the voltage step controlling method comprises the steps of: obtaining an output voltage of a photovoltaic cell; calculating voltage steps of the output voltage by using a step wave superposition method to obtain the voltages of n voltage steps, wherein the voltages of the n voltage steps are respectively represented by from u1 to un; normalizing the voltages of the n voltage steps to obtain results represented by from k1 to kn; calculating the conduction angles of the n voltage steps, wherein the conduction angles represented by from theta 1 to theta n respectively corresponds to from the 1st to the n-th voltage step; and respectively controlling the conduction of the 1stto the nth voltage steps by using the conduction angles represented by from theta 1 to theta n to convert a DC multilevel input into an AC level output. The conduction angles of the invention are calculated by normalizing the voltage steps and the voltage step differences can be different from each other. The technical scheme of the invention has an advantage of high inversion controlling precision and enables a photovoltaic cell outputting voltage with any amplitude cascaded.

Description

Voltage step control method and staircase waveform cascaded multilevel inverter

Technical field

The present invention relates to staircase waveform cascade connection multi-level inversion transformation technique field, relate in particular to a kind of voltage step control method and staircase waveform cascaded multilevel inverter.

Background technology

H bridge cascaded multilevel inverter has the plurality of advantages of multi-electrical level inverter, in occasions such as motor driving, High Power Active electric filterings, is widely used, and be one of important development direction of large power, electrically force transducer.Because the cascade multi-level inversion needs a plurality of independent DC power supplies, it is particularly suitable as the inverter of solar energy photovoltic power system.The staircase waveform stacked system is cascaded multilevel inverter groundwork pattern, and the advantage of this mode of operation maximum is: switching device operating frequency low (fundamental frequency), efficiency is high, electromagnetic interference (EMI) is little.

Existing cascaded multilevel inverter operation principle is as follows, calculating voltage step at first, and the voltage step between voltage step is poor to be equated, then derives the angle of flow of each voltage step, by controlling the angle of flow, realizes that direct current delivers stream.Impact due to discrete type, climate temperature and the installation site of the voltage-current characteristic of equipment, can cause the voltage step of stack poor not identical, and the inversion control error of prior art is larger; Equate in order to guarantee that voltage step is poor, need to limit the output voltage amplitude of the photovoltaic cell of cascade, the photovoltaic cell that prior art can not any output voltage amplitude of cascade.

Summary of the invention

The invention provides a kind of voltage step control method and staircase waveform cascaded multilevel inverter, its inversion control precision is high, but and the photovoltaic cell of any output voltage amplitude of cascade.

The voltage step control method of the staircase waveform cascaded multilevel inverter that different voltage is differential comprises:

A. obtain the output voltage of photovoltaic cell, utilize the voltage step of staircase waveform stacking method calculating output voltage, obtain the voltage of n voltage step, wherein, n voltage step is respectively the 1st, and 2 ..., i,, n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n;

B. to the voltage u of n voltage step ₁, u ₂..., u _i..., u _ncarry out normalized, obtain k ₁, k ₂..., k _i..., k _n, wherein, k _n=1;

C. calculate the 1st, 2 ..., i ..., the conduction angle of n-1 voltage step ₁, θ ₂..., θ _i..., θ _n-1:

$\left\{\begin{array}{c}{\mathrm{\θ}}_1=\frac{{\sin }^{-1}\left(k_1\right)}{2}\\ {\mathrm{\θ}}_2=\frac{{\sin }^{-1}\left(k_1\right)+{\sin }^{-1}\left(k_2\right)}{2}\\ ......\\ {\mathrm{\θ}}_i=\frac{{\sin }^{-1}\left(k_{i-1}\right)+{\sin }^{-1}\left(k_i\right)}{2}\\ ......\\ {\mathrm{\θ}}_{n-1}=\frac{{\sin }^{-1}\left(k_{n-2}\right)+{\sin }^{-1}\left(k_{n-1}\right)}{2}\end{array}\right.$

D. calculate the conduction angle of n voltage step _n:

-k ₁θ ₁+(k ₁-k ₂)θ ₂+…+(k _N-1-k _N)θ _N+90°=180°/π

Wherein, the constraints of the angle of flow is:

$\left\{\begin{array}{c}0<{\mathrm{\&theta;}}_1<{\sin }^{-1}{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ {\sin }^{-1}{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1<{\mathrm{\&theta;}}_2<{\sin }^{-1}{k}_2\\ {\sin }^{-1}{k}_2<{\mathrm{\&theta;}}_3<{\sin }^{-1}{k}_3\\ ...\\ {\sin }^{-1}{k}_{i-1}<{\mathrm{\&theta;}}_i<{\sin }^{-1}{k}_i\\ ...\\ {\sin }^{-1}{k}_{n-1}<{\mathrm{\&theta;}}_n<{\sin }^{-1}{k}_n=\frac{\mathrm{\&pi;}}{2}\end{array}\right.$

E. utilize the conduction angle calculated ₁, θ ₂..., θ _i..., θ _n-1, θ _n, control respectively the 1st, 2 ..., i ..., n-1, the conducting of n voltage step, become the many level inputs of direct current to exchange level output.

Preferably, steps A specifically comprises: obtain the output voltage of j group photovoltaic cell, obtain j output voltage; Utilize the voltage step of j output voltage of staircase waveform stacking method calculating, obtain the voltage of n voltage step, wherein, n voltage step is respectively the 1st, and 2 ..., i ..., n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n; Wherein, the quantity n of voltage step is:

for j output voltage carried out to permutation and combination, n ₀quantity for equivalent voltage after the voltage step stack.

Preferably, after step D, further comprise step F: calculate plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{u}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ \mathrm{\&Delta;}{u}_2=k_2-{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ ...\\ \mathrm{\&Delta;}{u}_i=k_i-k_{i-1}\\ ...\\ \mathrm{\&Delta;}{u}_n=k_{n-1}-k_n\end{array}\right.$

The general formula of output voltage is:

$u_m=u_n\underset{m=\mathrm{1,3,5,7,9}\&CenterDot;\&CenterDot;\&CenterDot;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{4}{\mathrm{m\&pi;}}[\mathrm{\&Delta;}{u}_1\cos m{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos m{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos m{\mathrm{\&theta;}}_n]\sin m\left(\mathrm{\&omega;t}\right)$

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

$u_1=u_n\frac{4}{\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos {\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos {\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos {\mathrm{\&theta;}}_n]\sin \left(\mathrm{\&omega;t}\right)$

Whether the fundamental voltage value that calculates of judgement belongs in preset benchmark fundamental voltage value scope, if so, and the output voltage of uncomfortable lay the grain volt battery, otherwise, adjust the output voltage of photovoltaic cell.

Preferably, after step D, further comprise step F:

Calculate plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{u}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ \mathrm{\&Delta;}{u}_2=k_2-{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ ...\\ \mathrm{\&Delta;}{u}_i=k_i-k_{i-1}\\ ...\\ \mathrm{\&Delta;}{u}_n=k_{n-1}-k_n\end{array}\right.$

The general formula of output voltage is:

$u_m=u_n\underset{m=\mathrm{1,3,5,7,9}\&CenterDot;\&CenterDot;\&CenterDot;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{4}{\mathrm{m\&pi;}}[\mathrm{\&Delta;}{u}_1\cos m{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos m{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos m{\mathrm{\&theta;}}_n]\sin m\left(\mathrm{\&omega;t}\right)$

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

$u_1=u_n\frac{4}{\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos {\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos {\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos {\mathrm{\&theta;}}_n]\sin \left(\mathrm{\&omega;t}\right)$

In general formula, m gets 3,5,7,9 ..., p; Calculate the 3rd, 5,7,9 of output voltage ..., p subharmonic voltage value, they are respectively u ₃, u ₅, u ₇, u ₉..., u _p:

$\left\{\begin{array}{c}{u}_3=u_n\frac{4}{3\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 3{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 3{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 3{\mathrm{\&theta;}}_n]\sin \left(3\mathrm{\&omega;t}\right)\\ u_5=u_n\frac{4}{5\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\mathrm{<figure-callout\; id="5"\; label="cos"\; filenames="H2009101941868E00032.png,H2009101941868E00033.png"\; state="\{\{state\}\}">cos</figure-callout>}5{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\mathrm{<figure-callout\; id="5"\; label="cos"\; filenames="H2009101941868E00032.png,H2009101941868E00033.png"\; state="\{\{state\}\}">cos</figure-callout>}5{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_{\mathrm{<figure-callout\; id="5"\; label="n\; cos"\; filenames="H2009101941868E00032.png,H2009101941868E00033.png"\; state="\{\{state\}\}">n</figure-callout>}}\cos 5{\mathrm{\&theta;}}_n]\sin \left(5\mathrm{\&omega;t}\right)\\ u_7=u_n\frac{4}{7\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_{1}7{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 7{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;\mathrm{\&Delta;}{u}_n\cos 7{\mathrm{\&theta;}}_n]\sin \left(7\mathrm{\&omega;t}\right)\\ u_9=u_n\frac{4}{9\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 9{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 9{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 9{\mathrm{\&theta;}}_n]\sin \left(9\mathrm{\&omega;t}\right)\\ ...\\ u_p=u_n\frac{4}{\mathrm{p\&pi;}}[\mathrm{\&Delta;}{u}_1\cos p{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos p{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos p{\mathrm{\&theta;}}_n]\sin \left(\mathrm{p\&omega;t}\right)\end{array}\right.$

Calculate the voltage total harmonic distortion of the 3rd time to the p time:

$\mathrm{THD}=\frac{\sqrt{\underset{m=\mathrm{3,5,7,9}...}{\overset{P}{\mathrm{\&Sigma;}}}{u}_m^2}}{u_1}$

Wherein, m=3,5,7,9 ..., p;

Whether the voltage total harmonic distortion that judgement calculates is less than preset reference voltage total harmonic distortion, if so, and the output voltage of uncomfortable lay the grain volt battery, otherwise, the output voltage of adjustment photovoltaic cell.

Preferably, after step D, further comprise step F:

Calculate plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{u}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ \mathrm{\&Delta;}{u}_2=k_2-{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ ...\\ \mathrm{\&Delta;}{u}_i=k_i-k_{i-1}\\ ...\\ \mathrm{\&Delta;}{u}_n=k_{n-1}-k_n\end{array}\right.$

The general formula of output voltage is:

$u_m=u_n\underset{m=\mathrm{1,3,5,7,9}\&CenterDot;\&CenterDot;\&CenterDot;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{4}{\mathrm{m\&pi;}}[\mathrm{\&Delta;}{u}_1\cos m{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos m{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos m{\mathrm{\&theta;}}_n]\sin m\left(\mathrm{\&omega;t}\right)$

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

$u_1=u_n\frac{4}{\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos {\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos {\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos {\mathrm{\&theta;}}_n]\sin \left(\mathrm{\&omega;t}\right)$

In general formula, m gets 3,5,7,9 ..., p; Calculate the 3rd, 5,7,9 of output voltage ..., p subharmonic voltage value, they are respectively u ₃, u ₅, u ₇, u ₉..., u _p:

$\left\{\begin{array}{c}{u}_3=u_n\frac{4}{3\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 3{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 3{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 3{\mathrm{\&theta;}}_n]\sin \left(3\mathrm{\&omega;t}\right)\\ u_5=u_n\frac{4}{5\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\mathrm{<figure-callout\; id="5"\; label="cos"\; filenames="H2009101941868E00032.png,H2009101941868E00033.png"\; state="\{\{state\}\}">cos</figure-callout>}5{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\mathrm{<figure-callout\; id="5"\; label="cos"\; filenames="H2009101941868E00032.png,H2009101941868E00033.png"\; state="\{\{state\}\}">cos</figure-callout>}5{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_{\mathrm{<figure-callout\; id="5"\; label="n\; cos"\; filenames="H2009101941868E00032.png,H2009101941868E00033.png"\; state="\{\{state\}\}">n</figure-callout>}}\cos 5{\mathrm{\&theta;}}_n]\sin \left(5\mathrm{\&omega;t}\right)\\ u_7=u_n\frac{4}{7\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_{1}7{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 7{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;\mathrm{\&Delta;}{u}_n\cos 7{\mathrm{\&theta;}}_n]\sin \left(7\mathrm{\&omega;t}\right)\\ u_9=u_n\frac{4}{9\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 9{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 9{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 9{\mathrm{\&theta;}}_n]\sin \left(9\mathrm{\&omega;t}\right)\\ ...\\ u_p=u_n\frac{4}{\mathrm{p\&pi;}}[\mathrm{\&Delta;}{u}_1\cos p{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos p{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos p{\mathrm{\&theta;}}_n]\sin \left(\mathrm{p\&omega;t}\right)\end{array}\right.$

Calculate the voltage total harmonic distortion of the 3rd time to the p time:

$\mathrm{THD}=\frac{\sqrt{\underset{m=\mathrm{3,5,7,9}...}{\overset{P}{\mathrm{\&Sigma;}}}{u}_m^2}}{u_1}$

Wherein, m=3,5,7,9 ..., p;

If the fundamental voltage value calculated belongs in preset benchmark fundamental voltage value scope, and the voltage total harmonic distortion calculated is less than preset reference voltage total harmonic distortion, the output voltage of uncomfortable lay the grain volt battery; Otherwise, the output voltage of adjustment photovoltaic cell.

A kind of staircase waveform cascaded multilevel inverter comprises:

The voltage step acquiring unit, for obtaining the output voltage of photovoltaic cell, utilize the voltage step of staircase waveform stacking method calculating output voltage, obtains the voltage of n voltage step; Wherein, n voltage step is respectively the 1st, and 2 ..., i ..., n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n;

Voltage step normalization unit, for the voltage u to n voltage step ₁, u ₂..., u _i..., u _ncarry out normalized, obtain k ₁, k ₂..., k _i..., k _n, wherein, k _n=1;

Angle of flow computing unit, for calculating the 1st, 2 ..., i ..., the conduction angle of n-1 voltage step ₁, θ ₂..., θ _i..., θ _n1:

$\left\{\begin{array}{c}{\mathrm{\&theta;}}_1=\frac{{\sin }^{-1}\left(k_1\right)}{2}\\ {\mathrm{\&theta;}}_2=\frac{{\sin }^{-1}\left(k_1\right)+{\sin }^{-1}\left(k_2\right)}{2}\\ ......\\ {\mathrm{\&theta;}}_i=\frac{{\sin }^{-1}\left(k_{i-1}\right)+{\sin }^{-1}\left(k_i\right)}{2}\\ ......\\ {\mathrm{\&theta;}}_{n-1}=\frac{{\sin }^{-1}\left(k_{n-2}\right)+{\sin }^{-1}\left(k_{n-1}\right)}{2}\end{array}\right.$

Calculate the conduction angle of n voltage step _n:

-k ₁θ ₁+(k ₁-k ₂)θ ₂+…+(k _N-1-k _N)θ _N+90°=180°/π

Wherein, the constraints of the angle of flow is:

$\left\{\begin{array}{c}0<{\mathrm{\&theta;}}_1<{\sin }^{-1}{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ {\sin }^{-1}{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1<{\mathrm{\&theta;}}_2<{\sin }^{-1}{k}_2\\ {\sin }^{-1}{k}_2<{\mathrm{\&theta;}}_3<{\sin }^{-1}{k}_3\\ ...\\ {\sin }^{-1}{k}_{i-1}<{\mathrm{\&theta;}}_i<{\sin }^{-1}{k}_i\\ ...\\ {\sin }^{-1}{k}_{n-1}<{\mathrm{\&theta;}}_n<{\sin }^{-1}{k}_n=\frac{\mathrm{\&pi;}}{2}\end{array}\right.$

Voltage step conducting control unit, the conduction angle calculated for utilization ₁, θ ₂..., θ _i..., θ _n-1, θ _n, control respectively the 1st, 2 ..., i ..., n-1, the conducting of n voltage step, become the many level inputs of direct current to exchange level output.

Preferably, the voltage step acquiring unit comprises:

The output voltage acquiring unit, for obtaining the output voltage of j group photovoltaic cell, obtain j output voltage;

The voltage step computing unit, for utilizing the voltage step of j output voltage of staircase waveform stacking method calculating, obtain the voltage of n voltage step, and wherein, n voltage step is respectively the 1st, and 2 ..., i ..., n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n;

Wherein, the quantity n of voltage step is:

for j output voltage carried out to permutation and combination, n ₀quantity for equivalent voltage after the voltage step stack.

Preferably, further comprise the output voltage adjustment unit;

The output voltage adjustment unit is for calculating plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ \mathrm{\&Delta;}{u}_2=k_2-{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ ...\\ \mathrm{\&Delta;}{u}_i=k_i-k_{i-1}\\ ...\\ \mathrm{\&Delta;}{u}_n=k_{n-1}-k_n\end{array}\right.$

The general formula of output voltage is:

$u_m=u_n\underset{m=\mathrm{1,3,5,7,9}\&CenterDot;\&CenterDot;\&CenterDot;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{4}{\mathrm{m\&pi;}}[\mathrm{\&Delta;}{u}_1\cos m{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos m{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos m{\mathrm{\&theta;}}_n]\sin m\left(\mathrm{\&omega;t}\right)$

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

${\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1=u_n\frac{4}{\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos {\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos {\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos {\mathrm{\&theta;}}_n]\sin \left(\mathrm{\&omega;t}\right)$

Whether the fundamental voltage value that calculates of judgement belongs in preset benchmark fundamental voltage value scope, if so, and the output voltage of uncomfortable lay the grain volt battery, otherwise, adjust the output voltage of photovoltaic cell.

Preferably, further comprise the output voltage adjustment unit;

The output voltage adjustment unit is for calculating plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ \mathrm{\&Delta;}{u}_2=k_2-{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ ...\\ \mathrm{\&Delta;}{u}_i=k_i-k_{i-1}\\ ...\\ \mathrm{\&Delta;}{u}_n=k_{n-1}-k_n\end{array}\right.$

The general formula of output voltage is:

$u_m=u_n\underset{m=\mathrm{1,3,5,7,9}\&CenterDot;\&CenterDot;\&CenterDot;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{4}{\mathrm{m\&pi;}}[\mathrm{\&Delta;}{u}_1\cos m{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos m{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos m{\mathrm{\&theta;}}_n]\sin m\left(\mathrm{\&omega;t}\right)$

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

${\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1=u_n\frac{4}{\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos {\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos {\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos {\mathrm{\&theta;}}_n]\sin \left(\mathrm{\&omega;t}\right)$

In general formula, m gets 3,5,7,9 ..., p; Calculate the 3rd, 5,7,9 of output voltage ..., p subharmonic voltage value, they are respectively u ₃, u ₅, u ₇, u ₉..., u _p:

$\left\{\begin{array}{c}{u}_3=u_n\frac{4}{3\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 3{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 3{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 3{\mathrm{\&theta;}}_n]\sin \left(3\mathrm{\&omega;t}\right)\\ u_5=u_n\frac{4}{5\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 5{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 5{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 5{\mathrm{\&theta;}}_n]\sin \left(5\mathrm{\&omega;t}\right)\\ u_7=u_n\frac{4}{7\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_{1}7{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 7{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;\mathrm{\&Delta;}{u}_n\cos 7{\mathrm{\&theta;}}_n]\sin \left(7\mathrm{\&omega;t}\right)\\ u_9=u_n\frac{4}{9\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 9{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 9{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 9{\mathrm{\&theta;}}_n]\sin \left(9\mathrm{\&omega;t}\right)\\ ...\\ u_p=u_n\frac{4}{\mathrm{p\&pi;}}[\mathrm{\&Delta;}{u}_1\cos p{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos p{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos p{\mathrm{\&theta;}}_n]\sin \left(\mathrm{p\&omega;t}\right)\end{array}\right.$

Calculate the voltage total harmonic distortion of the 3rd time to the p time:

$\mathrm{THD}=\frac{\sqrt{\underset{m=\mathrm{3,5,7,9}...}{\overset{P}{\mathrm{\&Sigma;}}}{u}_m^2}}{{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1}$

Wherein, m=3,5,7,9 ..., p;

Whether the voltage total harmonic distortion that judgement calculates is less than preset reference voltage total harmonic distortion, if so, and the output voltage of uncomfortable lay the grain volt battery, otherwise, the output voltage of adjustment photovoltaic cell.

Preferably, further comprise the output voltage adjustment unit;

The output voltage adjustment unit is for calculating plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ \mathrm{\&Delta;}{u}_2=k_2-{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ ...\\ \mathrm{\&Delta;}{u}_i=k_i-k_{i-1}\\ ...\\ \mathrm{\&Delta;}{u}_n=k_{n-1}-k_n\end{array}\right.$

The general formula of output voltage is:

$u_m=u_n\underset{m=\mathrm{1,3,5,7,9}\&CenterDot;\&CenterDot;\&CenterDot;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{4}{\mathrm{m\&pi;}}[\mathrm{\&Delta;}{u}_1\cos m{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos m{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos m{\mathrm{\&theta;}}_n]\sin m\left(\mathrm{\&omega;t}\right)$

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

${\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1=u_n\frac{4}{\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos {\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos {\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos {\mathrm{\&theta;}}_n]\sin \left(\mathrm{\&omega;t}\right)$

In general formula, m gets 3,5,7,9 ..., p; Calculate the 3rd, 5,7,9 of output voltage ..., p subharmonic voltage value, they are respectively u ₃, u ₅, u ₇, u ₉..., u _p:

$\left\{\begin{array}{c}{u}_3=u_n\frac{4}{3\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 3{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 3{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 3{\mathrm{\&theta;}}_n]\sin \left(3\mathrm{\&omega;t}\right)\\ u_5=u_n\frac{4}{5\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 5{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 5{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 5{\mathrm{\&theta;}}_n]\sin \left(5\mathrm{\&omega;t}\right)\\ u_7=u_n\frac{4}{7\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_{1}7{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 7{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;\mathrm{\&Delta;}{u}_n\cos 7{\mathrm{\&theta;}}_n]\sin \left(7\mathrm{\&omega;t}\right)\\ u_9=u_n\frac{4}{9\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 9{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 9{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 9{\mathrm{\&theta;}}_n]\sin \left(9\mathrm{\&omega;t}\right)\\ ...\\ u_p=u_n\frac{4}{\mathrm{p\&pi;}}[\mathrm{\&Delta;}{u}_1\cos p{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos p{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos p{\mathrm{\&theta;}}_n]\sin \left(\mathrm{p\&omega;t}\right)\end{array}\right.$

Calculate the voltage total harmonic distortion of the 3rd time to the p time:

$\mathrm{THD}=\frac{\sqrt{\underset{m=\mathrm{3,5,7,9}...}{\overset{P}{\mathrm{\&Sigma;}}}{u}_m^2}}{{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1}$

Wherein, m=3,5,7,9 ..., p;

If the fundamental voltage value calculated belongs in preset benchmark fundamental voltage value scope, and the voltage total harmonic distortion calculated is less than preset reference voltage total harmonic distortion, the output voltage of uncomfortable lay the grain volt battery; Otherwise, the output voltage of adjustment photovoltaic cell.

Beneficial effect of the present invention: in the present invention, obtain the output voltage of photovoltaic cell, utilize the voltage step of staircase waveform stacking method calculating output voltage, obtain the voltage of n voltage step, wherein, n voltage step is respectively the 1st, and 2 ... i,, n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n; Voltage u to n voltage step ₁, u ₂..., u _i..., u _ncarry out normalized, obtain _k1, k ₂..., k _i..., k _n, wherein, k _n=1; Calculate the 1st, 2 ..., i ..., the conduction angle of n-1 voltage step ₁, θ ₂..., θ _i..., θ _n-1; Calculate the conduction angle of n voltage step _n; Utilize θ ₁, θ ₂..., θ _i..., θ _n-1, θ _n, control respectively the 1st, 2 ..., i ..., n-1, the conducting of n voltage step, become the many level inputs of direct current to exchange level output.The angle of flow of the present invention is calculated by voltage step normalization, and voltage step is poor can be not identical, and without the output voltage amplitude of the photovoltaic cell that limits cascade, the technical program inversion control precision is high, but and the photovoltaic cell of any output voltage amplitude of cascade.

The accompanying drawing explanation

The method flow diagram that Fig. 1 is the embodiment of the present invention one;

The cascaded multilevel inverter schematic diagram that Fig. 2 is the embodiment of the present invention one;

The normalization value schematic diagram that Fig. 3 is the embodiment of the present invention one;

The output voltage that Fig. 4 is the embodiment of the present invention one synthesizes schematic diagram;

The cascaded multilevel inverter schematic diagram of three groups of voltage cascades that Fig. 5 is the embodiment of the present invention two;

The output voltage that Fig. 6 is the embodiment of the present invention two and the analogous diagram of load current waveform;

The spectrogram of the output voltage that Fig. 7 is the embodiment of the present invention two;

The spectrogram of the load current that Fig. 8 is the embodiment of the present invention two.

Embodiment

Embodiment mono-

Referring to Fig. 1 to Fig. 4, below in conjunction with accompanying drawing, the present invention is described in detail.

The voltage step control method of the staircase waveform cascaded multilevel inverter that different voltage is differential comprises:

Step 101. is obtained the output voltage of photovoltaic cell, utilizes the voltage step of staircase waveform stacking method calculating output voltage, obtains the voltage of n voltage step, wherein, n voltage step is respectively the 1st, and 2 ..., i,, n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n;

The voltage u of step 102. a couple n voltage step ₁, u ₂..., u _i..., u _ncarry out normalized, obtain k ₁, k ₂..., k _i..., k _n, wherein, k _n=1;

Step 103. calculates the 1st, 2 ..., i ..., the conduction angle of n-1 voltage step ₁, θ ₂..., θ _i..., θ _n-1, θ ₁~ θ ₆be taken at θ _{i+1, i}with θ _{i, i+1}centre position: $\left\{\begin{array}{c}{\mathrm{\&theta;}}_1=\frac{{\sin }^{-1}\left(k_1\right)}{2}\\ {\mathrm{\&theta;}}_2=\frac{{\sin }^{-1}\left(k_1\right)+{\sin }^{-1}\left(k_2\right)}{2}\\ ......\\ {\mathrm{\&theta;}}_i=\frac{{\sin }^{-1}\left(k_{i-1}\right)+{\sin }^{-1}\left(k_i\right)}{2}\\ ......\\ {\mathrm{\&theta;}}_{n-1}=\frac{{\sin }^{-1}\left(k_{n-2}\right)+{\sin }^{-1}\left(k_{n-1}\right)}{2}\end{array}\right.$ Formula 1

Calculate the conduction angle of n voltage step _n:

-k ₁θ ₁+ (k ₁-k ₂) θ ₂+ ... + (k _n-1-k _n) θ _n+ 90 °=180 °/π formula 2

Wherein, the constraints of the angle of flow is: $\left\{\begin{array}{c}0<{\mathrm{\&theta;}}_1<{\sin }^{-1}{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ {\sin }^{-1}{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1<{\mathrm{\&theta;}}_2<{\sin }^{-1}{k}_2\\ {\sin }^{-1}{k}_2<{\mathrm{\&theta;}}_3<{\sin }^{-1}{k}_3\\ ...\\ {\sin }^{-1}{k}_{i-1}<{\mathrm{\&theta;}}_i<{\sin }^{-1}{k}_i\\ ...\\ {\sin }^{-1}{k}_{n-1}<{\mathrm{\&theta;}}_n<{\sin }^{-1}{k}_n=\frac{\mathrm{\&pi;}}{2}\end{array}\right.$ Formula 6

The conduction angle that step 104. utilization calculates ₁, θ ₂..., θ _i..., θ _n-1, θ _n, control respectively the 1st, 2 ..., i ..., n-1, the conducting of n voltage step, become the many level inputs of direct current to exchange level output.

The angle of flow of the present invention is calculated by voltage step normalization, and voltage step is poor can be not identical, and without the output voltage amplitude of the photovoltaic cell that limits cascade, the technical program inversion control precision is high, but and the photovoltaic cell of any output voltage amplitude of cascade.The different voltages of this programme are differential, refer to different voltage steps poor.

In the present embodiment, step 101 specifically comprises: obtain the output voltage of j group photovoltaic cell, obtain j output voltage; Utilize the voltage step of j output voltage of staircase waveform stacking method calculating, obtain the voltage of n voltage step, wherein, n voltage step is respectively the 1st, and 2 ..., i ..., n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n; Wherein, the quantity n of voltage step is:

for j output voltage carried out to permutation and combination, n ₀quantity for equivalent voltage after the voltage step stack.As another kind of preferred implementation, the quantity n of voltage step is: this mode does not need to deduct the quantity of the rear equivalent voltage of stack.The quantity n computational methods of two kinds of above-mentioned voltage steps, can select according to actual conditions.

In the present embodiment, judge whether to need to adjust the output voltage of photovoltaic cell by the fundamental voltage value that calculates and/or voltage total harmonic distortion, following three kinds of preferred implementations are provided.These three kinds of modes can be selected according to actual environment.

Optimal way one:

Calculate plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n: $\left\{\begin{array}{c}\mathrm{\&Delta;}{u}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ \mathrm{\&Delta;}{u}_2=k_2-{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ ...\\ \mathrm{\&Delta;}{u}_i=k_i-k_{i-1}\\ ...\\ \mathrm{\&Delta;}{u}_n=k_{n-1}-k_n\end{array}\right.$ Formula 3

The general formula of output voltage is: $u_m=u_n\underset{m=\mathrm{1,3,5,7,9}\&CenterDot;\&CenterDot;\&CenterDot;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{4}{\mathrm{m\&pi;}}[\mathrm{\&Delta;}{u}_1\cos m{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos m{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos m{\mathrm{\&theta;}}_n]\sin m\left(\mathrm{\&omega;t}\right)$ Formula 4

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

${\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1=u_n\frac{4}{\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos {\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos {\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos {\mathrm{\&theta;}}_n]\sin \left(\mathrm{\&omega;t}\right)$

Whether the fundamental voltage value that calculates of judgement belongs in preset benchmark fundamental voltage value scope, if so, and the output voltage of uncomfortable lay the grain volt battery, otherwise, adjust the output voltage of photovoltaic cell.

Optimal way two:

Calculate plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ \mathrm{\&Delta;}{u}_2=k_2-{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ ...\\ \mathrm{\&Delta;}{u}_i=k_i-k_{i-1}\\ ...\\ \mathrm{\&Delta;}{u}_n=k_{n-1}-k_n\end{array}\right.$

The general formula of output voltage is:

$u_m=u_n\underset{m=\mathrm{1,3,5,7,9}\&CenterDot;\&CenterDot;\&CenterDot;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{4}{\mathrm{m\&pi;}}[\mathrm{\&Delta;}{u}_1\cos m{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos m{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos m{\mathrm{\&theta;}}_n]\sin m\left(\mathrm{\&omega;t}\right)$

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

${\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1=u_n\frac{4}{\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos {\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos {\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos {\mathrm{\&theta;}}_n]\sin \left(\mathrm{\&omega;t}\right)$

In general formula, m gets 3,5,7,9 ..., p; Calculate the 3rd, 5,7,9 of output voltage ..., p subharmonic voltage value, they are respectively u ₃, u ₅, u ₇, u ₉..., u _p: $\left\{\begin{array}{c}{u}_3=u_n\frac{4}{3\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 3{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 3{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 3{\mathrm{\&theta;}}_n]\sin \left(3\mathrm{\&omega;t}\right)\\ u_5=u_n\frac{4}{5\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 5{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 5{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 5{\mathrm{\&theta;}}_n]\sin \left(5\mathrm{\&omega;t}\right)\\ u_7=u_n\frac{4}{7\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_{1}7{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 7{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;\mathrm{\&Delta;}{u}_n\cos 7{\mathrm{\&theta;}}_n]\sin \left(7\mathrm{\&omega;t}\right)\\ u_9=u_n\frac{4}{9\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 9{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 9{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 9{\mathrm{\&theta;}}_n]\sin \left(9\mathrm{\&omega;t}\right)\\ ...\\ u_p=u_n\frac{4}{\mathrm{p\&pi;}}[\mathrm{\&Delta;}{u}_1\cos p{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos p{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos p{\mathrm{\&theta;}}_n]\sin \left(\mathrm{p\&omega;t}\right)\end{array}\right.$ Formula 7

Calculate the voltage total harmonic distortion of the 3rd time to the p time:

$\mathrm{THD}=\frac{\sqrt{\underset{m=\mathrm{3,5,7,9}...}{\overset{P}{\mathrm{\&Sigma;}}}{u}_m^2}}{{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1}$ Formula 5

Wherein, m=3,5,7,9 ..., p;

Whether the voltage total harmonic distortion that judgement calculates is less than preset reference voltage total harmonic distortion, if so, and the output voltage of uncomfortable lay the grain volt battery, otherwise, the output voltage of adjustment photovoltaic cell.

The span of P is unsuitable excessive, also unsuitable too small, can determine according to actual requirement.

Optimal way three:

Calculate plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ \mathrm{\&Delta;}{u}_2=k_2-{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ ...\\ \mathrm{\&Delta;}{u}_i=k_i-k_{i-1}\\ ...\\ \mathrm{\&Delta;}{u}_n=k_{n-1}-k_n\end{array}\right.$

The general formula of output voltage is:

$u_m=u_n\underset{m=\mathrm{1,3,5,7,9}\&CenterDot;\&CenterDot;\&CenterDot;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{4}{\mathrm{m\&pi;}}[\mathrm{\&Delta;}{u}_1\cos m{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos m{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos m{\mathrm{\&theta;}}_n]\sin m\left(\mathrm{\&omega;t}\right)$

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

${\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1=u_n\frac{4}{\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos {\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos {\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos {\mathrm{\&theta;}}_n]\sin \left(\mathrm{\&omega;t}\right)$

In general formula, m gets 3,5,7,9 ..., p; Calculate the 3rd, 5,7,9 of output voltage ..., p subharmonic voltage value, they are respectively u ₃, u ₅, u ₇, u ₉..., u _p:

$\left\{\begin{array}{c}{u}_3=u_n\frac{4}{3\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 3{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 3{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 3{\mathrm{\&theta;}}_n]\sin \left(3\mathrm{\&omega;t}\right)\\ u_5=u_n\frac{4}{5\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 5{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 5{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 5{\mathrm{\&theta;}}_n]\sin \left(5\mathrm{\&omega;t}\right)\\ u_7=u_n\frac{4}{7\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_{1}7{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 7{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;\mathrm{\&Delta;}{u}_n\cos 7{\mathrm{\&theta;}}_n]\sin \left(7\mathrm{\&omega;t}\right)\\ u_9=u_n\frac{4}{9\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 9{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 9{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 9{\mathrm{\&theta;}}_n]\sin \left(9\mathrm{\&omega;t}\right)\\ ...\\ u_p=u_n\frac{4}{\mathrm{p\&pi;}}[\mathrm{\&Delta;}{u}_1\cos p{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos p{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos p{\mathrm{\&theta;}}_n]\sin \left(\mathrm{p\&omega;t}\right)\end{array}\right.$

Calculate the voltage total harmonic distortion of the 3rd time to the p time:

$\mathrm{THD}=\frac{\sqrt{\underset{m=\mathrm{3,5,7,9}...}{\overset{P}{\mathrm{\&Sigma;}}}{u}_m^2}}{{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1}$

Wherein, m=3,5,7,9 ..., p;

Whether the fundamental voltage value that calculates of judgement belongs in preset benchmark fundamental voltage value scope, and whether the voltage total harmonic distortion that judgement calculates is less than preset reference voltage total harmonic distortion; If the fundamental voltage value calculated belongs in preset benchmark fundamental voltage value scope, and the voltage total harmonic distortion calculated is less than preset reference voltage total harmonic distortion, uncomfortable lay the grain lies prostrate the output voltage of battery, otherwise, the output voltage of adjustment photovoltaic cell.

Said reference fundamental voltage value scope and reference voltage total harmonic distortion are and set in advance, and for the technical indicator that this programme expectation reaches, if can't reach technical indicator, carry out the adjustment of the output voltage of photovoltaic cell.After adjusting, rerun step 101, what obtain is the output voltage after adjusting, and then recalculates, and judges whether again to adjust.

The output voltage of above-mentioned adjustment photovoltaic cell, can, for adjusting the output voltage of photovoltaic cell itself, send to multi-electrical level inverter by the output voltage after adjusting; Also can, for after multi-electrical level inverter receives the output voltage of photovoltaic cell, the output voltage received be adjusted.

Below the derivation of the angle of flow is described so that the reader understands the present invention theoretically, be conducive to enforcement of the present invention.Referring to Fig. 2 to Fig. 4.

Enumerate 4 staircase waveforms, set up staircase waveform normalization model.

$\left\{\begin{array}{c}\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ \mathrm{\&Delta;}{u}_2=k_2-{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ \mathrm{\&Delta;}{u}_3=k_3-k_2\\ \mathrm{\&Delta;}{u}_4=k_4-k_3\\ k_4=1\end{array}\right.$

Determine the value constraints of the angle of flow.

$\left\{\begin{array}{c}0<{\mathrm{\&theta;}}_1<{\sin }^{-1}{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ {\sin }^{-1}{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1<{\mathrm{\&theta;}}_2<{\sin }^{-1}{k}_2\\ {\sin }^{-1}{k}_2<{\mathrm{\&theta;}}_3<{\sin }^{-1}{k}_3\\ {\sin }^{-1}{k}_3<{\mathrm{\&theta;}}_4<{\sin }^{-1}{k}_4=\frac{\mathrm{\&pi;}}{2}\end{array}\right.$

Deriving, a kind of On-line Control algorithm---entire area equates control algolithm.The 4 rank systems of Fig. 3 of take are the example analysis, and in the scale value situation, in (0-π) scope, the sinusoidal wave area surrounded with staircase waveform is respectively:

Make S ₁=S ₂, obtain:

-k ₁θ ₁+(k ₁-k ₂)θ ₂+(k ₂-k ₃)θ ₃+(k ₃-k ₄)θ ₄+90°=180°/π

Be generalized to the N rank, obtain general formula and be:

-k ₁θ ₁+(k ₁-k ₂)θ ₂+…+(k _N-1-k _N)θ _N+90°=180°/π

For the ease of peek, determine following principle:

θ _imeet value constraints;

θ _i(i=2 ... N-1) be θ ₁integral multiple or be taken at θ _{i-1, i}with θ _{i, i+1}centre position;

θ _nby general formula, determine;

0<θ ₁<sin ^-1(k ₁)=sin ^-1(Δu ₁)。

Analyze the relation of the angle of flow and output harmonic wave, further determine θ _ivalue principle:

θ ₁value at θ ₁₂/ 2, i.e. sin ^-1(Δ u ₁left and right)/2 is proper;

θ _i(i=2 ... N-1) be taken at θ _{i-1, i}with θ _{i, i+1}between, i.e. sin ^-1k _i-1with sin ^-1k _ibetween, electricity consumption pressure reduction means, exists with

between;

Work as θ ₁～θ _n-1after determining, θ _nby general formula, determine.

Embodiment bis-

Referring to Fig. 5 to Fig. 8, the present embodiment with solar energy photovoltic power system as an example.The cascaded multilevel inverter of the present embodiment specifically refers to H bridge cascaded multilevel inverter.Suppose that the output voltage that three groups of photovoltaic cells obtain through the MPPT algorithm is respectively U _dc1=120V, U _dc2=150V, U _dc3=170V, three groups of outputs are respectively three H bridge cascaded multilevel inverters and are powered.Utilize the staircase waveform stacking method can calculate these three groups of input voltages and can access 7 voltage steps, be respectively u ₁=120V, u ₂=150V, u ₃=170V, u ₄=270V, u ₅=290V, u ₆=320V, u ₇=u _dcmax=440V.7 voltage steps are carried out to normalized, obtain k ₁=0.27, k ₂=0.34, k ₃=0.39, k ₄=0.61, k ₅=0.66, k ₆=0.73, k ₇=1, according to above-mentioned formula 3, plateau voltage normalization difference DELTA u ₁～Δ u ₇value is:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1=0.27\\ \mathrm{\&Delta;}{u}_2=k_2-{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1=0.34-0.27=0.07\\ \mathrm{\&Delta;}{u}_3=k_3-k_2=0.39-0.34=0.05\\ \mathrm{\&Delta;}{u}_4=k_4-k_3=0.61-0.39=0.22\\ \mathrm{\&Delta;}{u}_5=k_6-{\mathrm{<figure-callout\; id="5"\; label="k"\; filenames="H2009101941868E00032.png,H2009101941868E00033.png"\; state="\{\{state\}\}">k</figure-callout>}}_5=0.66-0.61=0.05\\ \mathrm{\&Delta;}{u}_6=k_7-k_6=0.73-0.66=0.07\\ \mathrm{\&Delta;}{u}_7=1-k_7=1-0.73=0.27\end{array}\right.$

According to above-mentioned formula 6, conduction angle ₁~ θ ₇value constraints be:

According to above-mentioned formula 1, conduction angle ₁~ θ ₆be respectively:

By k ₁～k ₇with θ ₁~ θ ₆substitution formula 2:

Therefore obtain θ ₇=61.2 °.

By θ ₁~ θ ₇and Δ u ₁~ Δ u ₇value substitution formula 4, make m=1, calculate the fundamental voltage value:

If frequency is 2000Hz, can calculate the fundamental voltage value is 240.8V.

Make m=3, according to above-mentioned formula 7, calculate the 3rd subharmonic voltage value:

In like manner, can calculate the 5th, 7 ..., the harmonic voltage value of 39 times.Result of calculation reference table 1:

Harmonic number	1	3	5	7	9	11	13	15	17	19
											Amplitude	442.3	6.07	6.9	2.6	10.8	14.2	2.12	13.4	0.21	8.1
Harmonic number	21	23	25	27	29	31	33	35	37	39
											Amplitude	13	3.8	1.6	11	4.9	7.2	3.1	8.5	3.1	0.2

Table 1

According to formula 5, establish p=39, calculate the voltage total harmonic distortion of the 3rd time to the p time:

$\mathrm{THD}=\frac{\sqrt{\underset{m=\mathrm{3,5,7},...}{\overset{39}{\mathrm{\&Sigma;}}}{u}_m^2}}{{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1}$

$=\frac{\sqrt{{6.07}^2+{6.9}^2+{2.6}^2+\&CenterDot;\&CenterDot;\&CenterDot;+{0.2}^2}}{442.3}$

$=33.7/442.3$

$=7.61\%$

If in the technical indicator set in advance, benchmark fundamental voltage value scope is (210V, 250V), and the reference voltage total harmonic distortion is 10%.This example judges fundamental voltage value and voltage total harmonic distortion simultaneously, to determine whether to need to adjust output voltage.Because the fundamental voltage value of this example belongs in preset benchmark fundamental voltage value scope, and the voltage total harmonic distortion is less than preset reference voltage total harmonic distortion, therefore do not need to adjust the output voltage of photovoltaic cell.

The present invention has widened the range of application of cascaded multilevel inverter; The range of application of cascaded multilevel inverter is extended to the fields such as new forms of energy, combination UPS.The present invention has simplified the algorithm of trapezoidal wave superposing control cascaded multilevel inverter; Succinctly, the scope of application wide, simplified system, engineering practicability is strong.The present invention can realize inverter control system in line computation, control precision is high, the inverter output waveforms quality is good.

Embodiment tri-

A kind of staircase waveform cascaded multilevel inverter comprises:

The voltage step acquiring unit, for obtaining the output voltage of photovoltaic cell, utilize the voltage step of staircase waveform stacking method calculating output voltage, obtains the voltage of n voltage step; Wherein, n voltage step is respectively the 1st, and 2 ..., i ..., n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n;

Voltage step normalization unit, for the voltage u to n voltage step ₁, u ₂..., u _i..., u _ncarry out normalized, obtain k ₁, k ₂..., k _i..., k _n, wherein, k _n=1;

Angle of flow computing unit, for calculating the 1st, 2 ..., i ..., the conduction angle of n-1 voltage step ₁, θ ₂..., θ _i..., θ _n-1:

$\left\{\begin{array}{c}{\mathrm{\&theta;}}_1=\frac{{\sin }^{-1}\left(k_1\right)}{2}\\ {\mathrm{\&theta;}}_2=\frac{{\sin }^{-1}\left(k_1\right)+{\sin }^{-1}\left(k_2\right)}{2}\\ ......\\ {\mathrm{\&theta;}}_i=\frac{{\sin }^{-1}\left(k_{i-1}\right)+{\sin }^{-1}\left(k_i\right)}{2}\\ ......\\ {\mathrm{\&theta;}}_{n-1}=\frac{{\sin }^{-1}\left(k_{n-2}\right)+{\sin }^{-1}\left(k_{n-1}\right)}{2}\end{array}\right.$

Calculate the conduction angle of n voltage step _n:

-k ₁θ ₁+(k ₁-k ₂)θ ₂+…+(k _N-1-k _N)θ _N+90°=180°/π

Wherein, the constraints of the angle of flow is:

$\left\{\begin{array}{c}0<{\mathrm{\&theta;}}_1<{\sin }^{-1}{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ {\sin }^{-1}{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1<{\mathrm{\&theta;}}_2<{\sin }^{-1}{k}_2\\ {\sin }^{-1}{k}_2<{\mathrm{\&theta;}}_3<{\sin }^{-1}{k}_3\\ ...\\ {\sin }^{-1}{k}_{i-1}<{\mathrm{\&theta;}}_i<{\sin }^{-1}{k}_i\\ ...\\ {\sin }^{-1}{k}_{n-1}<{\mathrm{\&theta;}}_n<{\sin }^{-1}{k}_n=\frac{\mathrm{\&pi;}}{2}\end{array}\right.$

Voltage step conducting control unit, the conduction angle calculated for utilization ₁, θ ₂..., θ _i..., θ _n-1, θ _n, control respectively the 1st, 2 ..., i ..., n-1, the conducting of n voltage step, become the many level inputs of direct current to exchange level output.

Preferably, the voltage step acquiring unit comprises:

The output voltage acquiring unit, for obtaining the output voltage of j group photovoltaic cell, obtain j output voltage;

The voltage step computing unit, for utilizing the voltage step of j output voltage of staircase waveform stacking method calculating, obtain the voltage of n voltage step, and wherein, n voltage step is respectively the 1st, and 2 ..., i ..., n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n;

Wherein, the quantity n of voltage step is:

for j output voltage carried out to permutation and combination, n ₀quantity for equivalent voltage after the voltage step stack.

The present embodiment further comprises the output voltage adjustment unit, in the present embodiment, provides following three kinds of preferred implementations, and these three kinds of modes can be selected according to actual environment.

Optimal way one:

The output voltage adjustment unit is for calculating plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ \mathrm{\&Delta;}{u}_2=k_2-{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ ...\\ \mathrm{\&Delta;}{u}_i=k_i-k_{i-1}\\ ...\\ \mathrm{\&Delta;}{u}_n=k_{n-1}-k_n\end{array}\right.$

The general formula of output voltage is:

$u_m=u_n\underset{m=\mathrm{1,3,5,7,9}\&CenterDot;\&CenterDot;\&CenterDot;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{4}{\mathrm{m\&pi;}}[\mathrm{\&Delta;}{u}_1\cos m{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos m{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos m{\mathrm{\&theta;}}_n]\sin m\left(\mathrm{\&omega;t}\right)$

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

${\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1=u_n\frac{4}{\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos {\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos {\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos {\mathrm{\&theta;}}_n]\sin \left(\mathrm{\&omega;t}\right)$

Whether the fundamental voltage value that calculates of judgement belongs in preset benchmark fundamental voltage value scope, if so, and the output voltage of uncomfortable lay the grain volt battery, otherwise, adjust the output voltage of photovoltaic cell.

Optimal way two:

The output voltage adjustment unit is for calculating plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ \mathrm{\&Delta;}{u}_2=k_2-{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ ...\\ \mathrm{\&Delta;}{u}_i=k_i-k_{i-1}\\ ...\\ \mathrm{\&Delta;}{u}_n=k_{n-1}-k_n\end{array}\right.$

The general formula of output voltage is:

$u_m=u_n\underset{m=\mathrm{1,3,5,7,9}\&CenterDot;\&CenterDot;\&CenterDot;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{4}{\mathrm{m\&pi;}}[\mathrm{\&Delta;}{u}_1\cos m{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos m{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos m{\mathrm{\&theta;}}_n]\sin m\left(\mathrm{\&omega;t}\right)$

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

${\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1=u_n\frac{4}{\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos {\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos {\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos {\mathrm{\&theta;}}_n]\sin \left(\mathrm{\&omega;t}\right)$

In general formula, m gets 3,5,7,9 ..., p; Calculate the 3rd, 5,7,9 of output voltage ..., p subharmonic voltage value, they are respectively u ₃, u ₅, u ₇, u ₉..., u _p:

$\left\{\begin{array}{c}{u}_3=u_n\frac{4}{3\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 3{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 3{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 3{\mathrm{\&theta;}}_n]\sin \left(3\mathrm{\&omega;t}\right)\\ u_5=u_n\frac{4}{5\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 5{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 5{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 5{\mathrm{\&theta;}}_n]\sin \left(5\mathrm{\&omega;t}\right)\\ u_7=u_n\frac{4}{7\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_{1}7{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 7{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;\mathrm{\&Delta;}{u}_n\cos 7{\mathrm{\&theta;}}_n]\sin \left(7\mathrm{\&omega;t}\right)\\ u_9=u_n\frac{4}{9\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 9{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 9{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 9{\mathrm{\&theta;}}_n]\sin \left(9\mathrm{\&omega;t}\right)\\ ...\\ u_p=u_n\frac{4}{\mathrm{p\&pi;}}[\mathrm{\&Delta;}{u}_1\cos p{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos p{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos p{\mathrm{\&theta;}}_n]\sin \left(\mathrm{p\&omega;t}\right)\end{array}\right.$

Calculate the voltage total harmonic distortion of the 3rd time to the p time:

$\mathrm{THD}=\frac{\sqrt{\underset{m=\mathrm{3,5,7,9}...}{\overset{P}{\mathrm{\&Sigma;}}}{u}_m^2}}{{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1}$

Wherein, m=3,5,7,9 ..., p;

Whether the voltage total harmonic distortion that judgement calculates is less than preset reference voltage total harmonic distortion, if so, and the output voltage of uncomfortable lay the grain volt battery, otherwise, the output voltage of adjustment photovoltaic cell.

Optimal way three:

The output voltage adjustment unit is for calculating plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

$\left\{\begin{array}{c}\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1={\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ \mathrm{\&Delta;}{u}_2=k_2-{\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">k</figure-callout>}}_1\\ ...\\ \mathrm{\&Delta;}{u}_i=k_i-k_{i-1}\\ ...\\ \mathrm{\&Delta;}{u}_n=k_{n-1}-k_n\end{array}\right.$

The general formula of output voltage is:

$u_m=u_n\underset{m=\mathrm{1,3,5,7,9}\&CenterDot;\&CenterDot;\&CenterDot;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\frac{4}{\mathrm{m\&pi;}}[\mathrm{\&Delta;}{u}_1\cos m{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos m{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos m{\mathrm{\&theta;}}_n]\sin m\left(\mathrm{\&omega;t}\right)$

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

${\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1=u_n\frac{4}{\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos {\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos {\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos {\mathrm{\&theta;}}_n]\sin \left(\mathrm{\&omega;t}\right)$

In general formula, m gets 3,5,7,9 ..., p; Calculate the 3rd, 5,7,9 of output voltage ..., p subharmonic voltage value, they are respectively u ₃, u ₅, u ₇, u ₉..., u _p:

$\left\{\begin{array}{c}{u}_3=u_n\frac{4}{3\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 3{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 3{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 3{\mathrm{\&theta;}}_n]\sin \left(3\mathrm{\&omega;t}\right)\\ u_5=u_n\frac{4}{5\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 5{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 5{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 5{\mathrm{\&theta;}}_n]\sin \left(5\mathrm{\&omega;t}\right)\\ u_7=u_n\frac{4}{7\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_{1}7{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 7{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;\mathrm{\&Delta;}{u}_n\cos 7{\mathrm{\&theta;}}_n]\sin \left(7\mathrm{\&omega;t}\right)\\ u_9=u_n\frac{4}{9\mathrm{\&pi;}}[\mathrm{\&Delta;}{u}_1\cos 9{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos 9{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos 9{\mathrm{\&theta;}}_n]\sin \left(9\mathrm{\&omega;t}\right)\\ ...\\ u_p=u_n\frac{4}{\mathrm{p\&pi;}}[\mathrm{\&Delta;}{u}_1\cos p{\mathrm{\&theta;}}_1+\mathrm{\&Delta;}{u}_2\cos p{\mathrm{\&theta;}}_2+\&CenterDot;\&CenterDot;\&CenterDot;+\mathrm{\&Delta;}{u}_n\cos p{\mathrm{\&theta;}}_n]\sin \left(\mathrm{p\&omega;t}\right)\end{array}\right.$

Calculate the voltage total harmonic distortion of the 3rd time to the p time:

$\mathrm{THD}=\frac{\sqrt{\underset{m=\mathrm{3,5,7,9}...}{\overset{P}{\mathrm{\&Sigma;}}}{u}_m^2}}{{\mathrm{<figure-callout\; id="1"\; label="u"\; filenames="H2009101941868E00021.png"\; state="\{\{state\}\}">u</figure-callout>}}_1}$

Wherein, m=3,5,7,9 ..., p;

If the fundamental voltage value calculated belongs in preset benchmark fundamental voltage value scope, and the voltage total harmonic distortion calculated is less than preset reference voltage total harmonic distortion, the output voltage of uncomfortable lay the grain volt battery; Otherwise, the output voltage of adjustment photovoltaic cell.

The adjustment of above-mentioned output voltage adjustment unit to the output voltage of photovoltaic cell, can, for adjusting the output voltage of photovoltaic cell itself, send to multi-electrical level inverter by the output voltage after adjusting; Also can, for after multi-electrical level inverter receives the output voltage of photovoltaic cell, the output voltage received be adjusted.

Above content is only preferred embodiment of the present invention, for those of ordinary skill in the art, according to thought of the present invention, all will change in specific embodiments and applications, and this description should not be construed as limitation of the present invention.

Claims (8)

1. the voltage step control method of the differential staircase waveform cascaded multilevel inverter of different voltage, is characterized in that, comprising:

A. obtain the output voltage of photovoltaic cell, utilize the staircase waveform stacking method to calculate the voltage step of described output voltage, obtain the voltage of n voltage step, wherein, n voltage step is respectively the 1st, and 2 ..., i,, n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n;

B. to the voltage u of n voltage step ₁, u ₂..., u _i..., u _ncarry out normalized, obtain k ₁, k ₂..., k _i..., k _n, wherein, k _n=1;

C. calculate the 1st, 2 ..., i ..., the conduction angle of n-1 voltage step ₁, θ ₂..., θ _i..., θ _n-1:

D. calculate the conduction angle of n voltage step _n:

-k ₁θ ₁+(k ₁-k ₂)θ ₂+…+(k _n-1-k _n)θ _n+90 ⁰=180 ⁰/π

Wherein, the constraints of the angle of flow is:

F: calculate plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

The general formula of output voltage is:

Wherein, m=1,3,5,7,9 ...., ∞;

In described general formula, m gets 1, calculates the fundamental voltage value of output voltage:

Judge whether the described fundamental voltage value calculated belongs in preset benchmark fundamental voltage value scope, if so, the output voltage of uncomfortable lay the grain volt battery, carry out step e; Otherwise, adjust the output voltage of photovoltaic cell, and return to steps A;

E. utilize the conduction angle calculated ₁, θ ₂..., θ _i..., θ _n-1, θ _n, control respectively the 1st, 2 ..., i ..., n-1, the conducting of n voltage step, become the many level inputs of direct current to exchange level output.

2. the voltage step control method of the differential staircase waveform cascaded multilevel inverter of different voltage, is characterized in that, comprising:

A. obtain the output voltage of photovoltaic cell, utilize the staircase waveform stacking method to calculate the voltage step of described output voltage, obtain the voltage of n voltage step, wherein, n voltage step is respectively the 1st, and 2 ..., i,, n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n;

B. to the voltage u of n voltage step ₁, u ₂..., u _i..., u _ncarry out normalized, obtain k ₁, k ₂..., k _i..., k _n, wherein, k _n=1;

C. calculate the 1st, 2 ..., i ..., the conduction angle of n-1 voltage step ₁, θ ₂..., θ _i..., θ _n-1:

D. calculate the conduction angle of n voltage step _n:

-k ₁θ ₁+(k ₁-k ₂)θ ₂+…+(k _n-1-k _n)θ _n+90 ⁰=180 ⁰/π

Wherein, the constraints of the angle of flow is:

F. calculate plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

The general formula of output voltage is:

wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

In general formula, m gets 3,5,7,9 ..., p; Calculate the 3rd, 5,7,9 of output voltage ..., p subharmonic voltage value, they are respectively u ₃, u ₅, u ₇, u ₉..., u _p:

Calculate the voltage total harmonic distortion of the 3rd time to the p time:

Wherein, m=3,5,7,9 ..., p;

Judge whether the described voltage total harmonic distortion calculated is less than preset reference voltage total harmonic distortion, if so, the output voltage of uncomfortable lay the grain volt battery, carry out step e; Otherwise, adjust the output voltage of photovoltaic cell, and return to steps A;

E. utilize the conduction angle calculated ₁, θ ₂..., θ _i..., θ _n-1, θ _n, control respectively the 1st, 2 ..., i ..., n-1, the conducting of n voltage step, become the many level inputs of direct current to exchange level output.

3. the voltage step control method of the differential staircase waveform cascaded multilevel inverter of different voltage, is characterized in that, comprising:

A. obtain the output voltage of photovoltaic cell, utilize the staircase waveform stacking method to calculate the voltage step of described output voltage, obtain the voltage of n voltage step, wherein, n voltage step is respectively the 1st, and 2 ..., i,, n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n;

B. to the voltage u of n voltage step ₁, u ₂..., u _i..., u _ncarry out normalized, obtain k ₁, k ₂..., k _i..., k _n, wherein, k _n=1;

C. calculate the 1st, 2 ..., i ..., the conduction angle of n-1 voltage step ₁, θ ₂..., θ _i..., θ _n-1:

D. calculate the conduction angle of n voltage step _n:

-k ₁θ ₁+(k ₁-k ₂)θ ₂+…+(k _n-1-k _n)θ _n+90 ⁰=180 ⁰/π

Wherein, the constraints of the angle of flow is:

F: calculate plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

The general formula of output voltage is:

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

In general formula, m gets 3,5,7,9 ..., p; Calculate the 3rd, 5,7,9 of output voltage ..., p subharmonic voltage value, they are respectively u ₃, u ₅, u ₇, u ₉..., u _p:

Calculate the voltage total harmonic distortion of the 3rd time to the p time:

Wherein, m=3,5,7,9 ..., p;

If the fundamental voltage value calculated described belongs in preset benchmark fundamental voltage value scope, and the described voltage total harmonic distortion calculated is less than preset reference voltage total harmonic distortion, and the output voltage of uncomfortable lay the grain volt battery, carry out step e; Otherwise, adjust the output voltage of photovoltaic cell, and return to steps A;

E. utilize the conduction angle calculated ₁, θ ₂..., θ _i..., θ _n-1, θ _n, control respectively the 1st, 2 ..., i ..., n-1, the conducting of n voltage step, become the many level inputs of direct current to exchange level output.

4. the voltage step control method of differential staircase waveform cascaded multilevel inverter according to the described different voltage of claims 1 to 3 any one, is characterized in that, steps A specifically comprises:

Obtain the output voltage of j group photovoltaic cell, obtain j output voltage;

Utilize the staircase waveform stacking method to calculate the voltage step of a described j output voltage, obtain the voltage of n voltage step, wherein, n voltage step is respectively the 1st, and 2 ..., i ..., n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n;

Wherein, the quantity n of voltage step is:

for j output voltage carried out to permutation and combination, n ₀quantity for equivalent voltage after the voltage step stack.

5. a staircase waveform cascaded multilevel inverter, is characterized in that, comprising:

The voltage step acquiring unit, for obtaining the output voltage of photovoltaic cell, utilize the staircase waveform stacking method to calculate the voltage step of described output voltage, obtains the voltage of n voltage step; Wherein, n voltage step is respectively the 1st, and 2 ..., i ..., n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n;

Voltage step normalization unit, for the voltage u to n voltage step ₁, u ₂..., u _i..., u _ncarry out normalized, obtain k ₁, k ₂..., k _i..., k _n, wherein, k _n=1;

Angle of flow computing unit, for calculating the 1st, 2 ..., i ..., the conduction angle of n-1 voltage step ₁, θ ₂..., θ _i..., θ _n-1:

Calculate the conduction angle of n voltage step _n:

-k ₁θ ₁+(k ₁-k ₂)θ ₂+…+(k _n-1-k _n)θ _n+90 ⁰=180 ⁰/π

Wherein, the constraints of the angle of flow is:

Voltage step conducting control unit, the conduction angle calculated for utilization ₁, θ ₂..., θ _i..., θ _n-1, θ _n, control respectively the 1st, 2 ..., i ..., n-1, the conducting of n voltage step, become the many level inputs of direct current to exchange level output;

Further comprise the output voltage adjustment unit;

The output voltage adjustment unit is for calculating plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

The general formula of output voltage is:

Wherein, m=1,3,5,7,9 ...., ∞;

In described general formula, m gets 1, calculates the fundamental voltage value of output voltage:

Judge whether the described fundamental voltage value calculated belongs in preset benchmark fundamental voltage value scope, if so, the output voltage of uncomfortable lay the grain volt battery, otherwise, adjust the output voltage of photovoltaic cell.

6. a staircase waveform cascaded multilevel inverter, is characterized in that, comprising:

The voltage step acquiring unit, for obtaining the output voltage of photovoltaic cell, utilize the staircase waveform stacking method to calculate the voltage step of described output voltage, obtains the voltage of n voltage step; Wherein, n voltage step is respectively the 1st, and 2 ..., i ..., n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n;

Voltage step normalization unit, for the voltage u to n voltage step ₁, u ₂..., u _i..., u _ncarry out normalized, obtain k ₁, k ₂..., k _i..., k _n, wherein, k _n=1;

Angle of flow computing unit, for calculating the 1st, 2 ..., i ..., the conduction angle of n-1 voltage step ₁, θ ₂..., θ _i..., θ _n-1:

Calculate the conduction angle of n voltage step _n:

-k ₁θ ₁+(k ₁-k ₂)θ ₂+…+(k _n-1-k _n)θ _n+90 ⁰=180 ⁰/π

Wherein, the constraints of the angle of flow is:

Voltage step conducting control unit, the conduction angle calculated for utilization ₁, θ ₂..., θ _i..., θ _n-1, θ _n, control respectively the 1st, 2 ..., i ..., n-1, the conducting of n voltage step, become the many level inputs of direct current to exchange level output;

Further comprise the output voltage adjustment unit;

The output voltage adjustment unit is for calculating plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

The general formula of output voltage is:

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

In general formula, m gets 3,5,7,9 ..., p; Calculate the 3rd, 5,7,9 of output voltage ..., p subharmonic voltage value, they are respectively u ₃, u ₅, u ₇, u ₉..., u _p:

Calculate the voltage total harmonic distortion of the 3rd time to the p time:

Wherein, m=3,5,7,9 ..., p;

Judge whether the described voltage total harmonic distortion calculated is less than preset reference voltage total harmonic distortion, if so, the output voltage of uncomfortable lay the grain volt battery, otherwise, the output voltage of adjustment photovoltaic cell.

7. a staircase waveform cascaded multilevel inverter, is characterized in that, comprising:

The voltage step acquiring unit, for obtaining the output voltage of photovoltaic cell, utilize the staircase waveform stacking method to calculate the voltage step of described output voltage, obtains the voltage of n voltage step; Wherein, n voltage step is respectively the 1st, and 2 ..., i ..., n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n;

Voltage step normalization unit, for the voltage u to n voltage step ₁, u ₂..., u _i..., u _ncarry out normalized, obtain k ₁, k ₂..., k _i..., k _n, wherein, k _n=1;

Angle of flow computing unit, for calculating the 1st, 2 ..., i ..., the conduction angle of n-1 voltage step ₁, θ ₂..., θ _i..., θ _n-1:

Calculate the conduction angle of n voltage step _n:

-k ₁θ ₁+(k ₁-k ₂)θ ₂+…+(k _n-1-k _n)θ _n+90 ⁰=180 ⁰/π

Wherein, the constraints of the angle of flow is:

Voltage step conducting control unit, the conduction angle calculated for utilization ₁, θ ₂..., θ _i..., θ _n-1, θ _n, control respectively the 1st, 2 ..., i ..., n-1, the conducting of n voltage step, become the many level inputs of direct current to exchange level output;

Further comprise the output voltage adjustment unit;

The output voltage adjustment unit is for calculating plateau voltage normalization difference DELTA u ₁, Δ u ₂..., Δ u _i..., Δ u _n:

The general formula of output voltage is:

Wherein, m=1,3,5,7,9 ...., ∞;

In general formula, m gets 1, calculates the fundamental voltage value of output voltage:

In general formula, m gets 3,5,7,9 ..., p; Calculate the 3rd, 5,7,9 of output voltage ..., p subharmonic voltage value, they are respectively u ₃, u ₅, u ₇, u ₉..., u _p:

Calculate the voltage total harmonic distortion of the 3rd time to the p time:

Wherein, m=3,5,7,9 ..., p;

If the fundamental voltage value calculated described belongs in preset benchmark fundamental voltage value scope, and the described voltage total harmonic distortion calculated is less than preset reference voltage total harmonic distortion, the output voltage of uncomfortable lay the grain volt battery; Otherwise, the output voltage of adjustment photovoltaic cell.

8. according to the described staircase waveform cascaded multilevel inverter of claim 5 to 7 any one, it is characterized in that, described voltage step acquiring unit comprises:

The output voltage acquiring unit, for obtaining the output voltage of j group photovoltaic cell, obtain j output voltage;

The voltage step computing unit, calculate the voltage step of a described j output voltage for utilizing the staircase waveform stacking method, obtains the voltage of n voltage step, wherein, n voltage step is respectively the 1st, and 2 ..., i,, n voltage step, the voltage of n voltage step is respectively u ₁, u ₂..., u _i..., u _n;

Wherein, the quantity n of voltage step is:

for j output voltage carried out to permutation and combination, n ₀quantity for equivalent voltage after the voltage step stack.

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