CN111953225B - PWM rectifier system parameter identification method - Google Patents
PWM rectifier system parameter identification method Download PDFInfo
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- CN111953225B CN111953225B CN202010664223.3A CN202010664223A CN111953225B CN 111953225 B CN111953225 B CN 111953225B CN 202010664223 A CN202010664223 A CN 202010664223A CN 111953225 B CN111953225 B CN 111953225B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/66—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal
- H02M7/68—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters
- H02M7/72—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/79—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/797—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output with possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
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Abstract
The invention relates to a method for identifying parameters of a PWM rectifier system, and belongs to the technical field of electronics. The method comprises the following steps: s1: adopts a traditional control method of a PWM rectifier to roughly estimate the system inductance L and the inductance compensation quantity L * The sum is used as a decoupling feedforward parameter to operate the PWM rectifier; s2: controlling PWM rectifier to output reactive current I q * The method comprises the steps of carrying out a first treatment on the surface of the S3: enabling a parameter identification module to adopt an incremental PI algorithm, taking 0 as a given value and taking a filtering value PT_I as a given value d For feedback, performing closed-loop control on system parameters to obtain a system inductance compensation quantity L * The method comprises the steps of carrying out a first treatment on the surface of the S4: after the PWM rectifier system is stable, the final system inductance compensation quantity is latched, the reactive current is stopped to be output, and the parameter identification module is forbidden, so that the follow-up control of the PWM rectifier is realized. The method is simple and convenient, has short identification time, can obtain the system inductance value more accurately, and is favorable for improving the dynamic and static performances of the rectifier.
Description
Technical Field
The invention belongs to the technical field of electronics, and relates to a method for identifying parameters of a PWM rectifier system.
Background
Along with the continuous development of the power electronic technology, various converter devices such as a frequency converter, an inverter power supply and the like are widely applied to various fields of national economy. At present, most of current transformers require a rectifier link to obtain a dc voltage. Because the conventional rectifying link adopts a diode uncontrolled rectifying circuit or a thyristor phase-controlled rectifying circuit, a large amount of harmonic waves and reactive power are injected into the power grid. Therefore, rectifiers that are sources of "pollution" to the power grid have been the focus of academic research.
Over several decades of technical development, a PWM rectifier with bi-directional energy flow and its control strategy are becoming the mainstream of current rectifiers. The PWM rectifier adopting the traditional control strategy realizes the sine of the network side current and operates at the unit power factor, so that the real green electric energy conversion can be realized. However, the traditional control strategy needs to be established on an accurate model of the PWM rectifier, and particularly, an internal feedforward decoupling link is closely related to the inductive reactance parameter of the system, and if the inductive reactance parameter of the system is inaccurate, the dynamic and static performances of the system of the PWM rectifier can be influenced.
Because of the existence of transformers and various types of filters in the actual working conditions, parameters of the PWM rectifier system are not easy to calculate and measure. Therefore, research on how to implement PWM rectifier system parameter identification is necessary.
Disclosure of Invention
Therefore, the invention aims to provide a method for identifying system parameters of a PWM rectifier, which is characterized in that a system parameter identification module is added on the basis of a traditional PWM rectifier control strategy, and the system parameter identification is finished offline, so that accurate system inductance parameters are obtained, the accurate control of the PWM rectifier is realized, and the overall performance of the PWM rectifier system is improved.
In order to achieve the above purpose, the present invention provides the following technical solutions:
a method of PWM rectifier system parameter identification, the method comprising the steps of:
s1: adopts a traditional control method of a PWM rectifier to roughly estimate the system inductance L and the inductance compensation quantity L * The sum is used as a decoupling feedforward parameter to operate the rectifier;
s2: controlling PWM rectifier to output reactive current I q * At the same time for active current I d The output result of the loop PI is subjected to low-pass filtering to obtain a filtering value PT_I d ；
S3: enabling a parameter identification module to adopt an incremental PI algorithm, taking 0 as a given value and taking a filtering value PT_I as a given value d For feedback, performing closed-loop control on system parameters to obtain a system inductance compensation quantity L * ；
S4: after the PWM rectifier system is stable, the final system inductance compensation quantity is latched, the reactive current is stopped to be output, and the prohibition is realizedThe parameter identification module is used for identifying the parameters (L+L) * ) And the subsequent control of the PWM rectifier is realized as a decoupling feedforward parameter.
Optionally, in the step S1, the system inductance value L of the PWM rectifier is roughly estimated by the system line inductance and the incoming filter inductance.
Optionally, in the step S1, an inductance compensation amount L * The initial value is 0.
Optionally, in the step S2, the PWM rectifier is controlled to output the reactive current I q * For capacitive reactive current, the current is positive by the grid flow direction rectifier, I q * Setting to a positive value;
controlling PWM rectifier to output reactive current I q * The inductive reactive current is positive by the current flowing to the rectifier of the power grid, I q * Is set to a negative value.
Optionally, in the step S2, a first-order low-pass filter is used to filter the active current I d And filtering the output result of the loop PI.
Optionally, the transfer function of the first-order low-pass filter is:
where Ti is a first order low pass filter time constant.
Optionally, in the step S3, an expression of the incremental PI algorithm is:
u(k)＝u(k-1)+K p Δe(k)+K i e(k)
where u (K) is the kth control output, e (K) is the kth error amount, Δe (K) =e (K) -e (K-1), K p Is a proportionality coefficient, K i Is an integral coefficient.
Optionally, in the step S3, the reactive current I is output in the form of feedback by the PWM rectifier q * Is determined by the characteristics of the (c).
Optionally, the PWM rectifier outputs reactive current I q * In the case of capacitive reactive current, step S3 takes the form of positive feedback, wherein the current is in the form ofThe grid flow direction rectifier is positive, I q * Setting to a positive value;
PWM rectifier output reactive current I q * When the current is inductive reactive current, the step S3 adopts a negative feedback mode, wherein the current takes the grid flow direction rectifier as positive, I q * Is set to a negative value.
The invention has the beneficial effects that:
(1) The invention adopts an offline parameter identification method, the structure of the original control strategy is slightly changed, and the parameter identification module does not influence the control effect of the original strategy under the condition of incapacitation. The method has the advantages of short identification time, accurate precision and good effect, and can greatly improve the effect of the traditional control strategy and improve the dynamic and static performance of the PWM rectifier system in the situation that the system parameters are undefined.
(2) The invention carries out parameter identification by controlling the mode of outputting reactive current by the PWM rectifier, has simple operation and easy realization, basically does not generate energy loss in the whole process, and can be widely applied to various power electronic occasions.
(3) The invention adopts the incremental PI algorithm to carry out closed-loop control on the inductive reactance compensation quantity of the system, only the control increment is needed to be calculated in each control period, the parameter identification process is gentle, and the impact on the system is small.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and other advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the specification.
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For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in the following preferred detail with reference to the accompanying drawings, in which:
FIG. 1 is a schematic block diagram of a parameter identification method of a PWM rectifier system according to the present invention;
FIG. 2 is a flowchart of a method for identifying parameters of a PWM rectifier system according to the present invention;
FIG. 3 shows a method for identifying parameters of a PWM rectifier system according to the present invention, which outputs a per unit value of 0.5 (capacitive) reactive current I q * Experimental waveform diagrams;
FIG. 4 shows a method for identifying parameters of a PWM rectifier system according to the present invention, which outputs a per unit value of-0.5 (inductive) reactive current I q * Experimental waveform diagrams.
Detailed Description
Other advantages and effects of the present invention will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present invention with reference to specific examples. The invention may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present invention. It should be noted that the illustrations provided in the following embodiments merely illustrate the basic idea of the present invention by way of illustration, and the following embodiments and features in the embodiments may be combined with each other without conflict.
Wherein the drawings are for illustrative purposes only and are shown in schematic, non-physical, and not intended to limit the invention; for the purpose of better illustrating embodiments of the invention, certain elements of the drawings may be omitted, enlarged or reduced and do not represent the size of the actual product; it will be appreciated by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.
The same or similar reference numbers in the drawings of embodiments of the invention correspond to the same or similar components; in the description of the present invention, it should be understood that, if there are terms such as "upper", "lower", "left", "right", "front", "rear", etc., that indicate an azimuth or a positional relationship based on the azimuth or the positional relationship shown in the drawings, it is only for convenience of describing the present invention and simplifying the description, but not for indicating or suggesting that the referred device or element must have a specific azimuth, be constructed and operated in a specific azimuth, so that the terms describing the positional relationship in the drawings are merely for exemplary illustration and should not be construed as limiting the present invention, and that the specific meaning of the above terms may be understood by those of ordinary skill in the art according to the specific circumstances.
In the embodiment, the system capacity of the PWM rectifier is 250kVA, the power grid side voltage is 380V/50Hz, the alternating current side incoming line reactor L=0.22 mH, and the system line inductance and the filter inductance are artificially set to L s =0.2 mH, dc side capacitance c=4.7 uF, dc voltage control target U dc * =700V. The control chip adopts TMS320C28346 of TI company, and the software interrupt period is the sampling period T s =250us. The system control schematic block diagram is shown in fig. 1, the method for identifying the system parameters of the PWM rectifier is adopted on the basis of the traditional PWM rectifier control strategy, the specific implementation steps are shown in fig. 2, and the method comprises the following four steps:
S1：T 1 at time=0.05s, the conventional control method of PWM rectifier is adopted to roughly estimate the system inductance L (0.22 mH) and the inductance compensation quantity L * (0 mH) operating the rectifier as a decoupled feed forward parameter;
S2：T 2 time=0.5s, control PWM rectifier output reactive current I q * At the same time for active current I d The output result of the loop PI is subjected to first-order low-pass filtering, the filter cut-off frequency f is selected to be 10Hz, and a filtering value PT_I is obtained d 。
The output reactive current is divided into I q * And respectively setting the two working conditions of a per unit value of 0.5 (capacitive reactive current) and-0.5 (inductive reactive current) for example verification.
The transfer function of the first-order low-pass filter is as follows:
by first-order backward difference methodDiscretizing the transfer function to obtain a system difference equation:
t in s Is a sample period value of 250us.
According to the first order filter difference equation and the required filter cut-off frequency, the final discretization equation can be obtained as follows:
Y(n)＝0.0025X(n)+0.9975Y(n-1)
S3：T 3 at time=1.0s, set en=1, enable the parameter identification module, use the incremental PI algorithm, given 0, filter the value pt_i d For feedback, performing closed-loop control on system parameters to obtain a system inductance compensation quantity L * 。
The expression formula of the incremental PI regulator is as follows:
u(k)＝u(k-1)+K p Δe(k)+K i e(k)
in order to reduce the oscillation and impact caused by the change of the inductance parameter of the system, the PI adjusting parameter is obtained by trial and error method, wherein the proportion adjusting parameter K p ＝0.01，K i ＝0.1。
When the PWM rectifier outputs a per unit value of 0.5 (capacitive reactive current), the step S3 adopts a positive feedback mode; when the PWM rectifier outputs per unit value-0.5 (inductive reactive current), step S3 adopts a negative feedback form.
S4：T 4 At time=1.5s, the PWM rectifier system is stable, the final system inductance compensation amount is latched, the output of reactive current is stopped, en=0 is set, the parameter identification module is disabled, and the PWM rectifier system is controlled to (l+l) * ) And the subsequent control of the PWM rectifier is realized as a decoupling feedforward parameter.
FIG. 2 shows the output per unit value of 0.5 (capacitive) reactive current I of a PWM rectifier using the method of the present invention q * Experimental waveform diagrams. As can be seen from FIG. 2, the inductance compensation L obtained after the system parameter identification by the method of the present invention * 0.1947mH, L is set according to practical human s (0.2 mH) differs by 0.0053mH.
FIG. 3 shows the output per unit value of the PWM rectifier-0.5 (inductive) reactive current I using the method of the present invention q * Experimental waveform diagrams. As can be seen from FIG. 3, the inductance compensation L obtained after the system parameter identification by the method of the present invention * 0.1964mH, L is set according to practical human s (0.2 mH) differs by 0.0036mH.
As can be seen from the experimental waveforms of fig. 2 and 3, the numerical value obtained by identifying the system parameters by the method has smaller difference from the actual parameter numerical value, which proves that the method has strong identifying capability and high accuracy, can obtain more accurate system parameters through a short-time identifying process, and is beneficial to improving the follow-up stable control of the PWM rectifier. Meanwhile, the identification module does not affect the original control structure block diagram after being forbidden to be enabled, so that the offline identification process can be well realized, and the method is suitable for most power electronic occasions.
Finally, it is noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the present invention, which is intended to be covered by the claims of the present invention.
Claims (1)
1. A method for identifying parameters of a PWM rectifier system, comprising: the method comprises the following steps:
s1: adopts a traditional control method of a PWM rectifier to roughly estimate the system inductance L and the inductance compensation quantity L * The sum is used as a decoupling feedforward parameter to operate the rectifier;
s2: controlling PWM rectifier to output reactive current I q * At the same time for active current I d The output result of the loop PI is subjected to low-pass filtering to obtain a filtering value PT_I d ；
S3: enabling a parameter identification module to adopt an incremental PI algorithm, taking 0 as a given value and taking a filtering value PT_I as a given value d For feedback, performing closed-loop control on system parameters to obtain a system inductance compensation quantity L * ；
S4: after the PWM rectifier system is stable, the final system inductance compensation quantity is latched, the reactive current is stopped to be output, and the control is forbiddenThe parameter identification module is used for identifying the parameter (L+L) * ) The subsequent control of the PWM rectifier is realized as a decoupling feedforward parameter;
in the step S1, a system inductance value L of the PWM rectifier is roughly estimated by a system line inductance and an incoming line filter inductance;
in the step S1, the inductance compensation amount L * The initial value is 0;
in the step S2, the PWM rectifier is controlled to output reactive current I q * For capacitive reactive current, the current is positive by the grid flow direction rectifier, I q * Setting to a positive value;
controlling PWM rectifier to output reactive current I q * The inductive reactive current is positive by the current flowing to the rectifier of the power grid, I q * Setting to a negative value;
in the step S2, a first-order low-pass filter is adopted for the active current I d Filtering the output result of the loop PI;
the transfer function of the first-order low-pass filter is as follows:
wherein Ti is a first-order low-pass filtering time constant;
in the step S3, the expression of the incremental PI algorithm is:
u(k)＝u(k-1)+K p Δe(k)+K i e(k)
where u (K) is the kth control output, e (K) is the kth error amount, Δe (K) =e (K) -e (K-1), K p Is a proportionality coefficient, K i Is an integral coefficient;
in the step S3, the reactive current I is output by the PWM rectifier in the form of feedback q * Is determined by the characteristics of (1);
the PWM rectifier outputs reactive current I q * When the current is the capacitive reactive current, the step S3 adopts a positive feedback mode, wherein the current is positive by the grid flow direction rectifier, I q * Setting to a positive value;
PWM rectifier output reactive current I q * When the current is inductive reactive current, the step S3 adopts a negative feedback mode, wherein the current takes the grid flow direction rectifier as positive, I q * Is set to a negative value.
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|---|---|---|---|---|
| JP2004064980A (en) * | 2002-07-31 | 2004-02-26 | Takeshi Funaki | Control system of self-excitation converter |
| CN105680752A (en) * | 2016-04-08 | 2016-06-15 | 中车株洲电力机车研究所有限公司 | Identification method and system for saturated inductance parameters of PMSM (Permanent Magnet Synchronous Motor) |
| CN110545057A (en) * | 2019-08-12 | 2019-12-06 | 北京交通大学 | feedforward voltage compensation based compensation method for compensating parameters below basic speed of permanent magnet synchronous motor |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6545887B2 (en) * | 1999-08-06 | 2003-04-08 | The Regents Of The University Of California | Unified constant-frequency integration control of three-phase power factor corrected rectifiers, active power filters and grid-connected inverters |
| US7336509B2 (en) * | 2005-09-28 | 2008-02-26 | Rockwell Automation Technologies, Inc. | Method and apparatus for estimating line inductance for PWM rectifier control |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004064980A (en) * | 2002-07-31 | 2004-02-26 | Takeshi Funaki | Control system of self-excitation converter |
| CN105680752A (en) * | 2016-04-08 | 2016-06-15 | 中车株洲电力机车研究所有限公司 | Identification method and system for saturated inductance parameters of PMSM (Permanent Magnet Synchronous Motor) |
| CN110545057A (en) * | 2019-08-12 | 2019-12-06 | 北京交通大学 | feedforward voltage compensation based compensation method for compensating parameters below basic speed of permanent magnet synchronous motor |
Non-Patent Citations (2)
| Title |
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| 刘峰等.《系统辨识与建模》.中国地质大学出版社,2019,第25-27页. * |
| 熊国忠.《运动控制技术与应用》.中国轻工业出版社,2016,第95-97页. * |
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