CN103281027B - Frequency converting air-conditioner compressor starts and low-frequency torque compensation method - Google Patents

Abstract

The invention discloses a kind of frequency converting air-conditioner compressor to start and low-frequency torque compensation method, comprise startup and frequency converting air-conditioner compressor low-frequency torque compensation two processes of frequency converting air-conditioner compressor, after start, compressor starts is run with open loop situations, the initial time of compressor start, the initial velocity of a given fixed step size and a fixed step size initia start-up current until start, according to the variance difference calculated after successfully starting scope, determine compensation policy.Present invention achieves the successful startup of compressor, the switching of breathing crack strategy belongs to soft handover, avoid the impact that control chip is subject to large starting resistor, electric current, extend the useful life of control chip, start success rate and control start-up time at about 500ms higher than 99.99%; Avoiding feedforward to table look-up the limitation of compensatory control, being common to the compressor of each model, convertible frequency air-conditioner 5 ~ 40Hz long-term stability can being realized and run.

Description

Frequency converting air-conditioner compressor starts and low-frequency torque compensation method

Technical field

The present invention relates to a kind of starting method and low-frequency torque compensation method of frequency converting air-conditioner compressor, specifically, the present invention relates to a kind of low-frequency torque compensation method after the efficient soft-start method of frequency converting air-conditioner compressor and compressor start success.

Background technology

In current existing frequency converting air-conditioner compressor starting method, the starting method of compressor is normally in official hour, the space voltage vector that given compressor drum amplitude is certain, angle is certain, although can successfully start under the active force haled, but compressor is once starting given such voltage vector to the impact being just equivalent to receive a pulse voltage control chip, run the useful life that will shorten controller for a long time.

When convertible frequency air-conditioner starts low-frequency operation successfully, in the air-breathing of compressor of air conditioner in a Machine cycle, compression, exhaust process, loading moment pulsation is very large, the low-frequency range working procedure execution cycle is long, and load torque is very large because integral action causes compressor speed to fluctuate.Known according to the experiment of 1kW convertible frequency air-conditioner low-frequency operation, when compressor operating is in 10Hz, in a Machine cycle, air-breathing and the frequency fluctuation compressed in these two processes reach 60% of setpoint frequency; When compressor operating is in 40Hz, in a Machine cycle, air-breathing and the frequency fluctuation compressed in this process of two are only 8% of setpoint frequency.Compressor operating frequency more slow-speed of revolution fluctuation is more difficult to stable operation more greatly, therefore, must carry out compensated torque to during frequency converting air-conditioner compressor low-frequency operation.

The control program great majority of current frequency converting air-conditioner compressor drive motors are Field orientable control, the block diagram of Field orientable control as shown in Figure 1, its principle is: using the error of speed outer shroud through the set point of proportional, integral (PI) computing as quadrature axis current, direct-axis current set point is decided to be zero, again using the error of two electric current loops through the set point of PI computing as rectangular axis voltage, rectangular axis voltage setting value just can by the calculating of programming realization space vector pulse width modulation (SVPWM) after mathematic(al) manipulation, calculate the switch that the three tunnel duty ratios made new advances drive three-phase inverter IGBT, the closed-loop vector finally realizing drive motor for compressor controls.The method that most air-conditioning manufacturer all adopts current feed-forward to table look-up to compensate on this basis realizes the compensation of low-frequency torque, specific practice is the compensation that on the quadrature axis current that calculated at Field orientable control by look-up table, superposition feed-forward component completes low-frequency torque, this feed-forward component is divided into amplitude parts and angle part, the offset that each Frequency point correspondence one is fixing, feedforward look-up table is completely based on debugging the specific compensation meter obtained, can only for the compensated torque under a certain model nominal situation, versatility is not high, even if the method cannot be made and adjusting timely when operational environment acute variation is taken in by same air-conditioning.

Summary of the invention

The problem that the present invention is pulsed in order to the soft start and low-frequency torque solving frequency converting air-conditioner compressor, proposes and solves frequency converting air-conditioner compressor startup and low-frequency torque compensation method.Concrete grammar comprises:

One, the startup control method of frequency converting air-conditioner compressor

The startup control method of described frequency converting air-conditioner compressor comprises the following steps:

Step1: after the given initial launch frequency start of convertible frequency air-conditioner, compressor starts is run with open loop situations, definition open loop operation parameter: electric current is from adding maximum time T_imax (300ms<T_imax<700ms), speed is from adding maximum time T_speedmax (1500ms<T_speedmax<2500ms), and the electric current run in the divided ring time and speed carry out amplitude limit, be respectively I_max (digital quantity, 5000<I_max<6000) with speed_max (1100rpm<speed_max<1300rpm),

Step2: open-loop start-up requires the initial time at compressor start, the initial velocity of a given fixed step size Speed_inc and the initia start-up current of a fixed step size I_inc, and the calculating formula of Speed_inc and I_inc is respectively:

$\mathrm{Speed}\_\mathrm{inc}=\frac{\mathrm{speed}\_\max \&times;K_s\&times;p}{T\_\mathrm{speed}\max \&times;n\&times;60}$

Wherein, p is drive motors number of pole-pairs, and n is sample frequency (6kHz<n<20kHz), K _sfor the index of modulation without symbol 16 bit format;

$I\_\mathrm{inc}=\frac{(I\_\max -I\_\mathrm{init})}{T\_i\max \&times;K_I}$

Wherein, I_init (digital quantity, 1500<I_init<2000), K _ifor being the index of modulation without symbol 16 bit format;

Step3: toggle speed is started from scratch, take 1/n as computing cycle, progressively adds up by fixed step size Speed_inc; Starting current starts to force given initial value I_init, take 1/n as computing cycle, progressively adds up by fixed step size I_inc;

Step4: while open loop operation, result open loop calculated is introduced closed loop and is carried out Field orientable control computing, by the speed speed_startup of current time, current signal I_startup incorporates motor electrical degree and motor quadrature axis current respectively into after data processing, and the result of closed loop computing can obtain the current time motor speed estimated;

Step5: record velocity error in the error convergence territory of regulation and continuous 50 convergences, then think and starts successfully, closedown open loop program, the computing of system closed loop; Otherwise time delay was restarted once after 3 minutes, so repeatedly until successfully start.

Two, frequency converting air-conditioner compressor low-frequency torque compensation method

Start successfully, just can compensate control to frequency converting air-conditioner compressor low-frequency torque, the method comprises step:

Step1: the drive motors of frequency converting air-conditioner compressor is permagnetic synchronous motor, adopts Field orientable control method, and the set point of regulation direct-axis current the independence that can realize torque in compressor and magnetic flux like this controls, and determines that low-frequency torque compensation scope is 5 ~ 40Hz;

Step2: the expression formula of compressor controlling electromagnetic torque is:

T _e=1.5pψ _fi _q

Wherein: ψ _ffor permanent magnet magnetic flux, i _qfor quadrature axis current, the present invention is by realizing the compensation of electromagnetic torque to the compensation of quadrature axis current;

Step3: when compressor high frequency (80 ~ 110Hz) stable operation, if its frequency departure is within ± 0.5Hz, utilizes following formulae discovery frequency variance σ ²:

${\mathrm{\&sigma;}}^2=\frac{1}{m}\underset{i=1}{\overset{m}{\mathrm{\&Sigma;}}}{({\hat{f}}_{\mathrm{ei}}-f_e^{*})}^2$

Wherein: m is compressor frequency sample, for setpoint frequency, be i-th group of sample frequency.

Work as m=m _s, and m _sduring >10000, the frequency variance that above-mentioned formulae discovery obtains is called standard variance

Step4: the frequency information under Real-time Collection compressor low frequency (5 ~ 40Hz) running status, with m _r(m _r>=1000) organize based on sample, as m=m in Step3 formula _rtime, calculate real-time frequency variance signal and be designated as itself and standard variance are subtracted each other the difference obtaining two prescription differences:

${\mathrm{\&Delta;e}}_{{\mathrm{\&sigma;}}^2}={\mathrm{\&sigma;}}_r^2-{\mathrm{\&sigma;}}_s^2;$

Meanwhile, acquisition current time quadrature axis current value is designated as the base value of quadrature axis current set point according to the difference determination quadrature axis current offset of variance size, compressor can reduction be sinusoidal wave at the waveform of Machine cycle internal burden torque, the expression formula of quadrature axis current offset is written as:

$i_{\mathrm{qc}}^{*}=A\sin ({\widehat{\mathrm{\&omega;}}}_{e}t+\mathrm{\&theta;})$

Wherein: A is the current amplitude size compensated, θ is the current angle size compensated, for the motor speed of sampling, and have

(I) according to the variance difference calculated scope, determine compensation policy.If the then base value of corresponding reduction quadrature axis current set point, until level off to zero;

(II) if or then quadrature axis current is carried out to the compensation of amplitude and phase place, amplitude is different with the interval of angle compensation in both cases, increases quadrature axis current set point first within the specific limits, judges can be converged near zero, if can not, be then multiplied by SIN function on this basis again with offset angle, the angle of compensation is also with current motor rotor-position for base value, and near base value, dynamic optimization in certain limit, judges again can be converged near zero, if still do not restrain, then perform again once (II), so repeatedly until meet control overflow;

(III) if compensation method is as (II), and now torque pulsation is violent, and compensation rate is strengthened on the basis of (II), and be multiplied by coefficient μ (1≤μ≤1.5) in (II) amplitude compensation part, angle compensation is constant.

The frequency converting air-conditioner compressor soft start that the present invention adopts and low-frequency torque compensation control method, achieve the successful startup of compressor, the switching of breathing crack strategy belongs to soft handover, avoid the impact that control chip is subject to large starting resistor, electric current, extend the useful life of control chip, start success rate and to control start-up time at about 500ms higher than 99.99%; In addition, the low-frequency torque compensation method based on frequency variance that the present invention adopts, avoiding feedforward and to table look-up the limitation of compensatory control, being common to the compressor of each model, can realizing convertible frequency air-conditioner 5 ~ 40Hz long-term stability and run.

Accompanying drawing illustrates:

Fig. 1 is the frequency converting air-conditioner compressor vector control block diagram of institute of the present invention belt compensated torque controller;

Fig. 2 is frequency converting air-conditioner compressor starting current, speed control curve proposed by the invention.

Embodiment:

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further details.

Example adopts certain brand 1kW convertible frequency air-conditioner as testing machine, comprises startup control method and the low-frequency torque compensation method of frequency converting air-conditioner compressor.

Embodiment 1

First, the initial launch frequency no matter control command sends is xHz (5≤x≤120), and compressor all first will run to 40Hz, stops 10s and to rerun setpoint frequency point.As shown in Figure 2, after control command is assigned, compressor just starts open-loop start-up for frequency converting air-conditioner compressor starting current, speed control curve, is divided into following two parts:

(α) speed of regulation electric motor starting is from 0Hz, with 1 (8KHz) s for the cycle, is that step-length increases with following formula:

$\mathrm{Speed}\_\mathrm{inc}=\frac{\mathrm{speed}\_\max \&times;K_s\&times;p}{T\_\mathrm{speed}\max \&times;n\&times;60}$

Wherein: speed_max=1200rpm, p=3, n=8000Hz, T_speedmax=2000ms, K _s=65536, it is T_speedmax that this process performs maximum time, and the motor speed calculated in real time is designated as speed_startup;

(β) electric current of regulation electric motor starting is from digital quantity initial value I_init, with 1 (8kHz) for the cycle, is that step-length increases with following formula:

$I\_\mathrm{inc}=\frac{(I\_\max -I\_\mathrm{init})}{T\_i\max \&times;K_I}$

Wherein, I_init=1752, I_max=5525, T_imax=500ms, K _iit is T_imax that=32767 these processes perform maximum time, and the current of electric calculated in real time is designated as I_startup.

Secondly, real-time speed previous step obtained is divided by sample frequency and integration obtains the real-time open loop electrical degree θ of compressor _eo, its expression formula is:

${\mathrm{\&theta;}}_{\mathrm{eo}}=\&Integral;\left(\frac{\mathrm{speed}\_\mathrm{startup}}{n}\right)\mathrm{dt}$

Electric current I _ startup previous step calculated is as quadrature axis current set point by the result that open loop calculates and θ _eobring closed loop computing into, closed loop computing can obtain the motor speed estimated will with current time motor speed set point compare (see Fig. 1), if velocity deviation is continuous be converged in 30rpm 50 times within, then show open-loop start-up success, close open loop program, the computing of incision closed-loop vector; Otherwise time delay was restarted once after 3 minutes, so repeatedly until successfully start.

Described compressor low-frequency torque compensation control method is as follows:

First, allow compressor operating in 100Hz, if now frequency error is within ± 0.5Hz, is the reliability of the standard variance improving setting, gathers 15000 group frequency information, with formula:

${\mathrm{\&sigma;}}^2=\frac{1}{15000}\underset{i=1}{\overset{15000}{\mathrm{\&Sigma;}}}{({\hat{f}}_{\mathrm{ei}}-100)}^2$

Calculating above formula variance and arranging this prescription difference is standard variance

Secondly, for the arbitrary frequency point between 5 ~ 40Hz, 3 variablees in Fig. 1 must be gathered, i.e. the speed of motor current time electrical degree and quadrature axis current base value and speedometer is shown as frequency form gather 1000 group frequency information, to ongoing frequency set point with 1000 groups of estimated values do variance, and often gather those group data that one group of new frequency data just abandons initial collection, to ensure that each calculating has 1000 groups of dynamic frequency data, in order to solve variance, this variance is designated as

Finally, the difference calculating real-time variance and standard variance is designated as concrete compensating control method is described below:

If x () now namely sample variance is less than standard variance, for energy-conservation consideration, now suitably can reduce the base value of quadrature axis current set point amplitude A, reduction scope is within the scope of this with for step-length, program cycle once just exists basis on cut but can only cut at most until match closest to zero but minus new quadrature axis current set point, its expression formula is:

$i_{\mathrm{qbnew}}^{*}=(1-\mathrm{\&alpha;})i_{\mathrm{qb}}^{*}$

If cannot match expected results, maintaining quadrature axis current set point is base value

If y () now then show that torque pulsation is larger, now need to introduce quadrature axis current and compensate, that first compensate is the amplitude A of quadrature axis current, suitably can increase the base value of quadrature axis current set point, increases the scope compensated and is within the scope of this with for step-length, program cycle once just exists basis on increase but can only increase at most until match still be greater than the new quadrature axis current set point of zero closest to zero, its expression formula is:

$i_{\mathrm{qbnew}}^{*}=(1+\mathrm{\&beta;})i_{\mathrm{qb}}^{*}$

If cannot expected results be matched, introduce angle θ on this basis again and compensate, by the motor speed of sampling the motor electrical degree of current time can be calculated angle compensation is on the basis of prime amplitude compensation, be multiplied by a SIN function wherein θ exists dynamic optimization in scope, until match still be greater than the new quadrature axis current set point of zero closest to zero, its expression formula is:

$i_{\mathrm{qbnew}}^{*}=(1+\mathrm{\&beta;})i_{\mathrm{qb}}^{*}\&times;\sin \left[(1+\mathrm{\&gamma;}){\widehat{\mathrm{\&theta;}}}_e\right]$

If still can not target setting be met, then perform again once (y), so repeatedly until meet control overflow.

If z () now then show that torque pulsation is very large, now need to introduce quadrature axis current and compensate, that first compensate is the amplitude A of quadrature axis current, and suitably can increase the base value of quadrature axis current set point, increasing the scope compensated is within the scope of this with for step-length, program cycle once just exists basis on increase but can only increase at most until match still be greater than the new quadrature axis current set point of zero closest to zero, its expression formula is:

$i_{\mathrm{qbnew}}^{*}=(1+\mathrm{\&epsiv;})i_{\mathrm{qb}}^{*}$

If cannot expected results be matched, introduce angle θ on this basis again and compensate, by the motor speed of sampling the motor electrical degree of current time can be calculated angle compensation is on the basis of prime amplitude compensation, be multiplied by a SIN function wherein θ exists dynamic optimization in scope, until match still be greater than the new quadrature axis current set point of zero closest to zero, its expression formula is:

$i_{\mathrm{qbnew}}^{*}=(1+\mathrm{\&epsiv;})i_{\mathrm{qb}}^{*}\&times;\sin \left[(1+\mathrm{\&lambda;}){\widehat{\mathrm{\&theta;}}}_e\right]$

If still can not target setting be met, then perform again once (z), so repeatedly until meet control overflow.

If w () now then show that frequency pulsation is violent, compensation method, as (z), compensation rate will be strengthened in the basis of (z), is multiplied by coefficient μ (1≤μ≤1.5) in (z) amplitude compensation part, angle compensation is constant, and its expression formula is:

$i_{\mathrm{qbnew}}^{*}=\mathrm{\&mu;}\&CenterDot;(1+\mathrm{\&epsiv;})i_{\mathrm{qb}}^{*}\&times;\sin \left[(1+\mathrm{\&lambda;}){\widehat{\mathrm{\&theta;}}}_e\right]$

The present invention is not limited to above-mentioned example, and every change made on basis of the present invention staff in the art, adds or delete, all belonging to protection scope of the present invention.

Claims (1)

1. frequency converting air-conditioner compressor starting method, is characterized in that comprising the following steps:

The startup of frequency converting air-conditioner compressor, comprises the following steps:

Step1: after the given initial launch frequency start of convertible frequency air-conditioner, compressor starts is run with open loop situations, definition open loop operation parameter: electric current is from adding maximum time =500ms, speed is from adding maximum time =2000ms, and the electric current run in the divided ring time and speed carry out amplitude limit, are respectively , for digital quantity, =5525, and =1200rpm;

Step2: open-loop start-up requires the initial time at compressor start, a given fixed step size initial velocity and a fixed step size initia start-up current, calculating formula be:

Wherein, for drive motors number of pole-pairs, for sample frequency, , for the index of modulation without symbol 16 bit format;

Wherein, for forcing given starting current initial value, digital quantity, , for the index of modulation without symbol 16 bit format;

Step3: toggle speed is started from scratch, with for computing cycle, press to fixed step size progressively add up; Starting current is to force given initial value , with for computing cycle, press to fixed step size progressively add up;

Step4: while open loop operation, result open loop calculated is introduced closed loop and is carried out Field orientable control computing, by the speed of current time , current signal after data processing, incorporate motor electrical degree and motor quadrature axis current respectively into, the result of closed loop computing can obtain the current time motor speed estimated;

Step5: record velocity error in the error convergence territory of regulation and continuous 50 convergences, then think and starts successfully, closedown open loop program, the computing of system closed loop; Otherwise time delay was restarted once after 3 minutes, so repeatedly until successfully start.