CN110365228B - Single-phase PWM rectifier control method based on observer - Google Patents

Single-phase PWM rectifier control method based on observer Download PDF

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CN110365228B
CN110365228B CN201910631399.6A CN201910631399A CN110365228B CN 110365228 B CN110365228 B CN 110365228B CN 201910631399 A CN201910631399 A CN 201910631399A CN 110365228 B CN110365228 B CN 110365228B
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network side
pwm rectifier
phase pwm
voltage
observer
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CN110365228A (en
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王顺亮
刘小林
刘天琪
马俊鹏
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Sichuan University
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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
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without 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
    • H02M7/217—Conversion of ac power input into dc power output without 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
    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0025—Arrangements for modifying reference values, feedback values or error values in the control loop of a converter

Abstract

The invention discloses a single-phase PWM rectifier control method based on an observer, which comprises the following steps: acquiring network side voltage and network side current of the single-phase PWM rectifier system, or acquiring network side voltage and direct current output voltage of the single-phase PWM rectifier system; obtaining an estimated direct current output voltage through a self-adaptive state observer according to the network side voltage and the network side current, or obtaining an estimated network side current through the self-adaptive state observer according to the network side voltage and the direct current output voltage; and sending the obtained signal and the signal estimated by the self-adaptive state observer into a control system to complete the control of the single-phase PWM rectifier. The invention can achieve the same control effect of the three sensors by only using two sensors of the network side voltage and the network side current or the network side voltage and the direct current output voltage without changing a control algorithm, and can still obtain a good operation result on the basis of reducing the hardware cost of a system.

Description

Single-phase PWM rectifier control method based on observer
Technical Field
The invention belongs to the field of converter control, and particularly relates to a single-phase PWM rectifier control method based on an observer.
Background
Compared with the traditional converter, the PWM rectifier has the advantages of sine current on the network side, high dynamic response speed, bidirectional energy flow, unit power factor on the network side, adjustable voltage on the intermediate direct current side and the like, so that the PWM rectifier is widely applied in various fields and has a good effect. Therefore, the PWM rectifier can realize real 'green electric energy conversion', and the control technology of the PWM rectifier is greatly extended and expanded. The method is not only applied to static reactive compensation, uninterruptible power supplies, active power filtering, unified power flow control, grid-connected power generation of renewable energy sources such as solar energy and wind energy, and the like, but also has a good application effect in the field of railway locomotive traction.
At present, traction converters in the field of traction of railway locomotives in China all adopt single-phase PWM rectifiers, and under the working condition of train traction, the single-phase PWM rectifiers play a role in rectification and convert single-phase alternating current absorbed from a traction power supply network into direct current; under the braking condition of the train, the single-phase PWM rectifier has an inversion function, and converts direct current into alternating current to be fed back to the traction power supply network. Therefore, as an important component of an ac transmission system, a single-phase PWM rectifier has been the focus of research.
The control strategy of the single-phase PWM rectifier is related to the performance of the single-phase PWM rectifier. Different control strategies may highlight different performance characteristics of the rectifier. Current phase control strategies can be broadly divided into two categories: a current control strategy and a power control strategy. No matter what kind of control strategy is adopted, the grid side voltage, the grid side current and the direct current output voltage need to be sampled and calculated, and sometimes a load current sensor is even added for higher response speed. Too many sensors inherently improve the control performance of the system, but also increase the hardware cost and reduce the reliability of the system.
Disclosure of Invention
The technical problem to be solved by the invention is to provide the observer-based single-phase PWM rectifier control method, the use of system sensors is reduced, the state estimation is carried out on the unmeasured signals through the observer theory, the original control method is not changed, and the normal operation of the single-phase PWM rectifier is realized.
In order to solve the technical problems, the invention adopts the technical scheme that:
an observer-based single-phase PWM rectifier control method comprises the following steps:
step 1: acquiring network side voltage and network side current of the single-phase PWM rectifier, or acquiring network side voltage and direct current output voltage of the single-phase PWM rectifier;
step 2: obtaining an estimated direct current output voltage through a self-adaptive state observer according to the network side voltage and the network side current, or obtaining an estimated network side current through the self-adaptive state observer according to the network side voltage and the direct current output voltage; the state equation of the self-adaptive state observer is as follows:
Figure GDA0002508401360000021
wherein A (t), B (t), C (t), D (t) are system matrixes of the single-phase PWM rectifier, X (t) is a system state variable, Y (t) is a system output,
Figure GDA0002508401360000022
is an estimated value of a system state variable, u (t) is an input variable, theta (t) is a disturbance variable, gamma (t),Σ, k (t) are matrices of sizes conforming to the matrix calculation rule, γ (t) is a signal matrix generated by a ordinary differential equation, k (t) is an error feedback matrix, Γ is a positive angle matrix for balancing the convergence speed of the state and disturbance parameters, Σ is a matrix for weighting different output components, Γ and Σ are constant matrices, and therefore the "(t)" suffix is not added;
and step 3: and sending the obtained signal and the signal estimated by the self-adaptive state observer into a control system to complete the control of the single-phase PWM rectifier.
Furthermore, the characteristic value of the adaptive state observer A (t) -K (t) C (t) is set to be 5-10 times of the pole of the single-phase PWM rectifier A (t).
Compared with the prior art, the invention has the beneficial effects that: the state observability of the single-phase PWM rectifier is utilized, and the adaptive observer is used for estimating the state of the non-sampled state, so that the use of sensors is reduced, and the economic benefit of the system is improved; meanwhile, under the condition of not changing a system control strategy, the system performance under the control of the reduced sensor is almost the same as that under the control of the full sensor.
Drawings
FIG. 1 is a control structure diagram of a single-phase PWM rectifier;
FIG. 2 is a diagram of a single phase PWM rectifier sensor less control architecture;
FIG. 3 is a diagram of simulation results of a conventional control method for a single-phase PWM rectifier;
FIG. 4 is a diagram of simulation results of a single-phase PWM rectifier non-output DC voltage sensor;
FIG. 5 is a graph comparing the output voltage observer waveform with the actual output voltage waveform;
FIG. 6 is a simulation result diagram of a non-grid side current sensor of the single-phase PWM rectifier;
fig. 7 is a graph comparing the waveform of the net side current observer and the actual net side current waveform.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
The operation structure of the single-phase PWM rectifier is shown in figure 1.U in FIG. 1s、is、iL、udcRespectively representing the network side voltage, the network side current, the load current and the direct current output voltage. R, L, CdcRespectively representing a network side resistor, a network side filter inductor and a direct current side capacitor. By making a pair us、is、udcSampling control is carried out to obtain an AC side voltage modulation wave uabAnd obtaining a corresponding switching signal through an SPWM algorithm to complete the control of the single-phase PWM rectifier.
The corresponding state space equation is:
Figure GDA0002508401360000041
wherein: d represents the duty cycle of a single switching cycle, which varies with the operation of the single-phase PWM rectifier.
Observer-based sensor-less control is: only the network side voltage and the network side current or the network side voltage and the direct current output voltage are sampled, the non-sampled signals are subjected to real-time state estimation by adopting the principle of an adaptive observer, so that state information required by all control is obtained, and then the sensor signals and the estimated signals are sent to a control system to complete the control of the single-phase PWM rectifier.
Principle of adaptive observer: for an observational system, if there are unknown disturbance parameters, in which case it is desirable to construct an adaptive system that can both determine the unknown parameters and estimate the state variables, such an adaptive system is an adaptive observer.
The state space equation of the single-phase rectification system is
Figure GDA0002508401360000042
Wherein X (t) represents system variables, A (t) represents a system matrix, B (t) represents an input matrix, u (t) represents input variables,
Figure GDA0002508401360000043
representsThe disturbance matrix, θ (t) represents disturbance variable, C (t) represents output matrix, and Y (t) represents system output variable.
Corresponding to the state space equation of the single-phase PWM rectifier
Figure GDA0002508401360000044
u＝us，θ＝iL
Figure GDA0002508401360000045
When no net side current sampling is performed, C is (10); when the direct current output voltage is not sampled, C is (01);
the state equation of the adaptive observer is:
Figure GDA0002508401360000051
wherein the content of the first and second substances,
Figure GDA0002508401360000052
is an estimated value of the system state variable, and gamma (t), gamma, sigma, K (t) is a matrix conforming to the size of the matrix calculation rule; γ (t) is a signal matrix generated by ordinary differential equations, Γ is a positive angular matrix used to balance the convergence speed of the state and disturbance parameters, Σ is a matrix used to weight different output components, and since there is only one output quantity, the matrix is constant and can be set to be constant 1. K (t) is an error feedback matrix, the pole allocation of the adaptive system is achieved by setting parameters of the matrix, and the characteristic value of the observer system A (t) -K (t) C (t) is usually set to be 5-10 times of the pole of the single-phase rectification system A (t).
The control structure of the single-phase PWM rectifier based on the adaptive observer without output DC voltage or network side current sensor is shown in FIG. 2, wherein
Figure GDA0002508401360000053
Respectively representing the output DC voltage and the estimate of the network-side currentAnd (6) evaluating.
The following compares the results of the conventional control with the method proposed by the present invention by way of specific examples. The main circuit parameters shown in fig. 2 are as follows: r is 0.2 omega, L is 4mH, C is 10mF, RLoad11.2 Ω, ac voltage usThe effective value is 1500V, the AC fundamental frequency is 50Hz, the control system adopts the same method and structure, the control mode of a voltage outer ring and a current inner ring is adopted, the given value of a DC output voltage outer ring is 2600V, and the switching frequency is 15 kHz. The observer parameters were: the k (t) matrix is a variation matrix, so that the poles of the observer system a (t) -k (t) c (t) are always 5 times the poles of the original system, and then the k (t) matrix can be obtained, the γ (t) matrix is obtained by iteration of formula (3), where Γ and Σ are constant values, and in this example, Γ is 100 and Σ is 1, so that all coefficient parameter values in formula (3) are obtained. To embody the observer with disturbance rejection, R is taken at 0.4sLoadThe mutation was 8.4 Ω.
1. Single-phase PWM rectifier non-DC voltage sensing control
Fig. 3 is a diagram showing a simulation result of a conventional control scheme, fig. 4 is a diagram showing a simulation result of a non-output dc voltage sensor, and it can be seen from fig. 3 and 4 that waveforms obtained by the non-output dc voltage sensing system and the conventional method are substantially identical, which illustrates that the waveforms after the sensor reduction of the present invention have no influence on the system compared with the results of the conventional method. When the system fluctuates, namely the load changes at 0.4s, the method of the invention and the traditional method run consistently. The voltage observer output waveform and the actual waveform are in a pair, such as shown in fig. 5, and it can be seen that the observer waveform and the actual voltage waveform are almost consistent, the observation effect is accurate, and the observer can still track the load quickly even after the load changes.
2. Current-free sensor control for single-phase PWM rectifier
The output waveforms and the comparison graphs are shown in fig. 3, fig. 6 and fig. 7, and it can be seen that the results obtained by the method of the present invention are basically consistent with those obtained by the conventional method, the waveform of the observer is consistent with the actual waveform after transient response, the actual current waveform can still be quickly tracked when the load changes, and the analysis conclusion is consistent with the control without voltage sensing.

Claims (2)

1. An observer-based single-phase PWM rectifier control method comprises the following steps:
step 1: acquiring network side voltage and network side current of the single-phase PWM rectifier, or acquiring network side voltage and direct current output voltage of the single-phase PWM rectifier;
step 2: obtaining an estimated direct current output voltage through a self-adaptive state observer according to the network side voltage and the network side current, or obtaining an estimated network side current through the self-adaptive state observer according to the network side voltage and the direct current output voltage;
the state space equation of the single-phase rectification system is
Figure FDA0002725371340000011
Wherein X (t) represents system variables, A (t) represents a system matrix, B (t) represents an input matrix, u (t) represents input variables,
Figure FDA0002725371340000012
representing a disturbance matrix, theta (t) representing a disturbance variable, C (t) representing an output matrix, and Y (t) representing a system output variable;
corresponding to a single-phase PWM rectifier state space equation
Figure FDA0002725371340000013
Figure FDA0002725371340000014
When no net side current sampling is performed, C is (10); when the direct current output voltage is not sampled, C is (01);
us、is、iL、udcrespectively representing the network side voltage, the network side current and the load currentOutputting a direct current voltage; r, L, CdcRespectively representing a network side resistor, a network side filter inductor and a direct current side capacitor; d (t) represents the duty cycle of a single switching cycle, which varies with the operation of the single-phase PWM rectifier system;
the state equation of the self-adaptive state observer is as follows:
Figure FDA0002725371340000021
wherein the content of the first and second substances,
Figure FDA0002725371340000022
is an estimate of the state variable of the system,
Figure FDA0002725371340000023
representing the estimation value of disturbance variable of the single-phase PWM rectifier, superscript "·" represents the differential of the variable, gamma (t) is a signal matrix generated by an ordinary differential equation, K (t) is an error feedback matrix, r is a positive angle matrix used for balancing the convergence speed of a state and disturbance parameters, and Σ is a matrix used for weighting different output components;
and step 3: and sending the obtained signal and the signal estimated by the self-adaptive state observer into a control system to complete the control of the single-phase PWM rectifier.
2. The observer-based single-phase PWM rectifier control method according to claim 1, wherein the adaptive state observer A (t) -K (t) C (t) is set to have a characteristic value 5-10 times that of a pole A (t) of the single-phase PWM rectifier.
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