CN105467227A - Method for detecting output phase loss of frequency converter - Google Patents

Abstract

The invention provides a method for detecting the output phase loss of a frequency converter, and the method comprises the steps: firstly carrying out the AD sampling of a three-phase output current through the CPU of the frequency converter; converting the collected three-phase current alpha-beta into a two-phase coordinate, and respectively obtaining I<alpha> and I<beta>, which are orthogonal to each other; mapping I<alpha> and I<beta> to a composite plane, and enabling the composite plane to be divided into six sectors according to the polarity of the current; respectively placing a global variable in each sector, and continuously adding one to the global variables; taking the current output frequency of the frequency converter as a period, and judging the six global variables. If two or more global variables are zero, the frequency converter must be in a state of phase loss, and the frequency converter must be shut down. If no or one global variable is zero or all global variables are not zero, the frequency converter is normal, and the six global variables must be cleared as zero at this moment for next judgment.

Description

A kind of frequency converter exports the detection method of phase shortage

Technical field

The present invention relates to low voltage frequency converter field, particularly relate to the detection method that a kind of frequency converter exports phase shortage.

Background technology

At the industrial age that frequency conversion is universal, the defencive function of frequency converter is more and more perfect, also more and more important.Wherein, frequency converter output phase shortage is a very serious very thorny again fault, how to detect extremely important accurately.In frequency converter, usual output frequency is variable, and guard method is traditionally difficult to protect frequency converter; Further, the IGBT in frequency converter is very fragile, once cause output current seriously uneven because export phase shortage, greatly may damage IGBT, so it is extremely important to carry out detection to phase shortage fast and accurately.Some document proposes, frequency converter is exported three-phase current carry out AD sampling after and be mapped in complex plane after alpha-beta conversion, time fixing with one, base is to I _αand I _βcarry out the variable that 2 parameter arctangent cp cp operation obtain a rotation angle, and derivative operation is carried out to this rotation angle can judge whether phase shortage.This method really can complete phase shortage when three-phase is all sinusoidal wave and judge, but the output current wave of frequency converter is not complete sine wave, causes judging to be forbidden by having very large interference by 2 parameter arctangent cp cp operation.

Summary of the invention

For problems of the prior art, the object of the invention is to propose the detection method that a kind of frequency converter exports phase shortage, by the CPU of frequency converter, analysis is carried out to the global variable of each sector and can judge whether phase shortage.

The invention provides the detection method that a kind of frequency converter exports phase shortage, comprise the steps:

The CPU of frequency converter carries out AD sampling to three-phase output current;

The three-phase electricity flow valuve alpha-beta collected is transformed in two coordinates, obtains orthogonal I respectively _αand I _β;

By I _αand I _βbe mapped on complex plane, and complex plane is divided into 6 sectors by the polarity of electric current;

Place a global variable in each sector respectively and make it constantly add 1;

With frequency converter current output frequency for the cycle judges these 6 global variables, if there is two or more global variable to be 0, then prove frequency converter now certain phase shortage, the necessary hard stop of frequency converter; If not to be less than two global variables be 0 or be not 0, then represent frequency converter normal, now tackle 6 global variables and all reset wait and judge next time.

Described frequency converter provided by the invention exports the detection method of phase shortage, by the CPU of frequency converter, analysis is carried out to the global variable of each sector and can judge whether phase shortage, to carry out corresponding to default phase of frequency converter fault fast and to take appropriate measures, avoid to greatest extent because phase shortage causes IGBT or other damages.

Accompanying drawing explanation

Fig. 1 is the major loop figure that a kind of frequency converter provided by the invention exports frequency converter in the detection method of phase shortage;

Fig. 2 is the schematic diagram that a kind of frequency converter provided by the invention exports sector in complex plane in the detection method of phase shortage;

Fig. 3 is that a kind of frequency converter provided by the invention exports the N value schematic diagram that in the detection method of phase shortage, sector is corresponding.

Embodiment

Technical scheme of the present invention is further illustrated by embodiment below in conjunction with accompanying drawing:

The detection method utilizing a kind of frequency converter of the present invention to export phase shortage for the main circuit of frequency converter shown in Fig. 1 carries out output pile defection.

First, the AD device of CPU carries out AD conversion to the three-phase current that frequency converter exports, and analog current discretize is obtained the instantaneous value I of three-phase current _a, I _b, I _c, after alpha-beta (Clark) conversion, obtain orthogonal I _αand I _β.By the two-phase quadrature current that obtains through following formula:

$\left\{\begin{array}{c}{I}_1=I_{\mathrm{\&alpha;}}\\ I_2=\frac{\sqrt{2}*I_{\mathrm{\&beta;}}-I_{\mathrm{\&alpha;}}}{2}\\ I_3=\frac{\sqrt{2}\&times;I_{\mathrm{\&beta;}}+I_{\mathrm{\&alpha;}}}{2}\end{array}\right.$

Carry out conversion and obtain I ₁, I ₂, I ₃these three values are converted through following formula by three values again:

$\left\{\begin{array}{c}{A}_r={\mathrm{sgn}}^{+}\left(I_1\right)\\ B_r={\mathrm{sgn}}^{+}\left(I_2\right)\\ C_r={\mathrm{sgn}}^{+}\left(I_3\right)\end{array}\right.$

Obtain Ar, Br, Cr tri-parameters respectively, by this three number again through following formula operation:

N＝4*Cr+2*Br+Ar

Analyze as shown in Figure 2 and Figure 3 to the value of N, determine 6 sectors.

CPU arranges a global variable in each sector and makes it constantly add 1, if the output current of frequency converter 3 phase all exists, the track so rotated in three-phase current vector complex plane should successively: 1.-2.-3.-4.-5.-6. sector or 6.-5.-4.-3.-2.-1. sector; Consider that the output current of frequency converter all contains harmonic wave usually, the rotational trajectory causing three-phase current vector in complex plane is not a standard round but the circle of a distortion, so there is individual sector can not enter, but, as long as three-phase current all exists and imbalance is not too serious, so the rotational trajectory of three-phase current vector in complex plane can not skip at most two sectors; Especially, when frequency converter exports phase shortage, the current phase of two non-phase shortages of frequency converter should become 180 ° of reverses, being embodied in current phasor complex plane should be only move in two sectors of symmetry and skipped other 4 sectors, global variable in the sector be skipped can not increase, because CPU does not perform the instruction that it adds 1, so in the cycle of an output frequency, as long as judged whether that whether plural sector global variable is 0 and can judges whether phase shortage.

As can be seen here:

1, frequency converter export there is no a phase shortage time, 1.-2.-3.-4.-5.-6. or 6.-5.-4.-3.-2.-1. the rotational trajectory of three-phase current vector in complex plane should be a circle, and its sector order turned over should successively:;

2, when frequency converter exports phase shortage, the track that three-phase current vector rotates in complex plane should be a straight line passing at 0, has and swinging back and forth only two sectors.

Therefore, CPU only needs to judge whether current phasor has been skipped plural sector and just can have been judged frequency converter whether phase shortage.Simultaneously, because the time shared by each sector reaches 1/6th of frequency converter output frequency, any one interference also can not reach in so far, so application this method detection output phase shortage antijamming capability is extremely strong, can think that detecting each time is all accurately; Again because do not need to perform 2 parameter tan computings consuming time, save cpu resource greatly, so be very easy to implement.

Invention has been described above; obvious realization of the present invention is not subject to the restrictions described above; as long as have employed the various improvement that method of the present invention is conceived and technical scheme is carried out; or the design of invention and technical scheme directly applied to other occasion, all in protection scope of the present invention without to improve.

Claims (1)

1. frequency converter exports a detection method for phase shortage, it is characterized in that, comprises the steps:

The CPU of frequency converter carries out AD sampling to three-phase output current;

The three-phase electricity flow valuve alpha-beta collected is transformed in two coordinates, obtains orthogonal I respectively _αand I _β;

By I _αand I _βbe mapped on complex plane, and complex plane is divided into 6 sectors by the polarity of electric current;

Place a global variable in each sector respectively and make it constantly add 1;

With frequency converter current output frequency for the cycle judges these 6 global variables, if there is two or more global variable to be 0, then prove frequency converter now certain phase shortage, the necessary hard stop of frequency converter; If not to be less than two global variables be 0 or be not 0, then represent frequency converter normal, now tackle 6 global variables and all reset wait and judge next time.