CN111446873B - Nonlinear passive current control method - Google Patents

Nonlinear passive current control method Download PDF

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CN111446873B
CN111446873B CN202010363305.4A CN202010363305A CN111446873B CN 111446873 B CN111446873 B CN 111446873B CN 202010363305 A CN202010363305 A CN 202010363305A CN 111446873 B CN111446873 B CN 111446873B
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equation
current
rectifier
error
switch
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CN111446873A (en
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李萍
王久和
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Beijing Information Science and Technology 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
    • H02M7/23—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 arranged for operation in parallel
    • 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
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
    • H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
    • H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac 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
    • H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac 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

Abstract

The embodiment of the invention relates to a nonlinear passive current control method, which is applied to a novel hybrid rectifier, wherein the novel NTLUTHR comprises an SSPBR circuit and a three-level unidirectional T-shaped rectifier (TLUTR) which is connected in parallel, a compensation inductor is connected in series at the alternating current input end of the SSPBR circuit, and the method comprises the following steps: controlling the TLUTR circuit based on a TLUTR converter EL type passive current control new algorithm; and controlling the SSPBR circuit based on a new EL-type passive current control algorithm of the SSPBR converter.

Description

Nonlinear passive current control method
Technical Field
The embodiment of the invention relates to the technical field of electronics, in particular to a nonlinear passive current control method.
Background
In recent years, a hybrid rectifier which has a unit power factor, a high power density, a low cost and a simple structure and is suitable for medium and high voltage occasions becomes a hot point for research of scholars at home and abroad. The hybrid rectifier is formed by connecting a line-commutated converter (LCC) and a self-commutated converter (SCC) in parallel. The adopted LCC is formed by cascading a three-phase uncontrolled rectifier and a Boost circuit with a symmetrical structure to form an SSTPBR; the SCC adopts a VIENNA rectifier or a multi-level PWM rectifier formed by bidirectional switches with different topological structures.
The hybrid rectifier is characterized in that two rectifiers are combined, the purpose of improving the energy efficiency of the system is achieved by optimizing energy distribution, and meanwhile, the structure has energy one-way fluidity. The operation frequency and the power ratio of the two rectifiers are adjusted, so that the overall loss of the hybrid rectifier system can be reduced. SSPBR switching devices are few, and the operation is carried out in a low-frequency and high-power mode; the VIENNA rectifier or the PWM rectifier has relatively many switching devices and operates in a high frequency, low power mode. Therefore, the hybrid rectifier with the structure has the characteristics of high efficiency, high power density and the like, can be suitable for the fields of remote communication, X-ray, aerospace, new energy power generation and the like, and can effectively improve the cost benefit of the system.
Although the hybrid rectifier has advantages in energy efficiency, power density, capacity and the like, the existing current tracking control method is low in precision, so that the AC total input current sine degree of the hybrid rectifier is low, and the THD exceeds the GB/T14549 + 1993 (electric energy quality-public power grid harmonic regulation index), which influences the performance of the hybrid rectifier and limits the popularization and application of the hybrid rectifier.
Disclosure of Invention
In view of the above, to solve the above technical problems or some technical problems, embodiments of the present invention provide a nonlinear passive current control method.
The embodiment of the invention provides a nonlinear passive current control method, which is applied to a novel hybrid rectifier, wherein the novel NTLUTHR comprises an SSPBR circuit and a three-level unidirectional T-shaped rectifier (TLUTR) which is connected in parallel, a compensation inductor is connected in series at the alternating current input end of the SSPBR circuit, and the method comprises the following steps:
controlling the TLUTR circuit based on a TLUTR converter EL type passive current control new algorithm;
and controlling the SSPBR circuit based on a new EL-type passive current control algorithm of the SSPBR converter.
In one possible embodiment, the TLUTR converter EL-type passive current control new algorithm comprises:
f(Rv,xe,α)＝sat(Rv|xe|αsign(xe))
in the formula, 0<α<1, sat (x) is a saturation function,
Figure BDA0002475741150000021
in one possible embodiment, the new algorithm for the passive current control of the SSTPBR converter EL type comprises:
ug＝sat(Rba|xbe|αsign(xbe))；
in the formula, the same is 0<α<1, sat (x) is a saturation function,
Figure BDA0002475741150000022
the technical scheme provided by the embodiment of the invention provides an improved circuit aiming at a topological structure of a hybrid rectifier, a compensation inductor is connected in series at the SSPBR alternating current side and is used for weakening the peak generated at the synthesis position of the currents of two parallel rectifiers at a natural commutation point and inhibiting the electromagnetic interference generated by the peak, aiming at a three-phase hybrid rectifier control strategy, a passive control method adopting constant damping injection is adopted to generate a larger error when tracking a complex current waveform, a passive current control strategy adopting nonlinear virtual damping injection is provided, the current tracking control precision and the input current waveform quality are further improved, and the influence of current distortion on a power grid is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the embodiments of the present invention, and it is also possible for a person skilled in the art to obtain other drawings based on the drawings.
FIG. 1 is a schematic diagram of a novel three-level T-type uni-directional hybrid rectifier formed by TLUTR according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a TLUTR circuit topology according to an embodiment of the present invention;
FIG. 3 is an equivalent circuit schematic of a TLUTR architecture rectifier in accordance with an embodiment of the present invention;
FIG. 4 is a schematic diagram of a topology of an SSPBR conversion circuit according to an embodiment of the present invention;
fig. 5 is a schematic diagram of NTLUTHR rectifier control according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of a current waveform according to an embodiment of the present invention;
FIG. 7 is a schematic diagram of current tracking control waveforms of a Boost circuit in an SSPBR in accordance with an embodiment of the present invention;
FIG. 8 is a schematic diagram of an id-axis current tracking control waveform of a TLUTR input current in a d-q coordinate system according to an embodiment of the present invention;
fig. 9 is a schematic diagram of a total input waveform of a hybrid rectifier obtained by a conventional/novel passive current control method according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
For the convenience of understanding of the embodiments of the present invention, the following description will be further explained with reference to specific embodiments, which are not to be construed as limiting the embodiments of the present invention.
In the embodiment of the invention, the topological structure of the hybrid rectifier is improved, and in order to reduce di/dt of SSPBR input current, the novel hybrid rectifier is connected with a compensation inductor L in series at the alternating current input end of an SSPBR circuitz. The parallel VIENNA rectifier or PWM rectifier adopts a three-level unidirectional T-shaped rectifier, abbreviated as TLUTR, and is a simplified circuit obtained by optimizing a switching device by the VIENNA rectifier. FIG. 1 shows a Novel Three-level T-type Unidirectional Hybrid Rectifier (NTLUTHR) composed of TLUTR.
The input current of the hybrid rectifier has a relation of ij＝izj+ivj(j ═ a, b, c). Due to the different circuit structures of the SSTPBR and the TLUTR, the input current change rate is different. The diode conduction current changes dramatically (di) at the natural commutation point of SSTPBRzjLarge dt) with input inductance LvTLUTR input current ivjChanges are relatively slow (di)vjSmaller/dt). The superposition of the two currents can cause the peak of the total input current to cause electromagnetic interference, and the larger peak can cause the increase of the total input current THD of the hybrid rectifier. Therefore, the NTLUTHR topological structure is connected with the compensation inductor L in series at the alternating current input end of the original SSTPBR circuitzReducing current jump and izjAnd the change rate makes SSTPBR and TLUTR input currents symmetrical at the phase change point synthesis position so as to inhibit the generation of current spikes.
On the basis of improving the topological structure of the hybrid rectifier, the current tracking control precision needs to be further improved. The TLUTR circuit topology is shown in fig. 2.
The rectifier with the TLUTR structure has the characteristics of few power devices and high operation reliability. The schematic equivalent circuit is shown in fig. 3. S in FIG. 3j(j ═ a, b, c) is a bidirectional switch, and when the switch is on, S j1 is ═ 1; when the switch is turned off, S j0. The three-phase power supply is assumed to be balanced sinusoidal voltage, an ideal switch tube has no time delay and no loss, a direct-current side capacitor has no equivalent resistance, a filter reactor is a linear inductor, and a resistor is an equivalent input resistor of a rectifier. According to the equivalent circuit of fig. 3, a mathematical model is established as follows:
Figure BDA0002475741150000051
in the formula (I), the compound is shown in the specification,
Figure BDA0002475741150000052
ΔuDCis a capacitor C1And a capacitor C2Difference u of voltagec1-uc2. Defining a new switching function
Figure BDA0002475741150000053
The model (1) becomes:
Figure BDA0002475741150000054
the mathematical model of TLUTR under the synchronous rotation d-q coordinate system can be obtained as follows:
Figure BDA0002475741150000055
in the formula (d)d、dq、d0The components of the switching function on the d, q, 0 axes, respectively; i.e. id、iqThe components of the TLUTR three-phase alternating current on d-q axes respectively; u. ofd、uqIs the component of the TLUTR three-phase ac voltage on the d-q axis.
According to the formula of TLUTR mathematical model (3), the Euler-Lagrange (EL) mathematical model can be used to describe:
Figure BDA0002475741150000069
in the formula (I), the compound is shown in the specification,
Figure BDA0002475741150000061
Figure BDA0002475741150000062
ud＝Um(amplitude of phase voltage of AC power supply), uq＝0。
MTTA positive definite diagonal matrix is formed; j. the design is a squareTTAs an antisymmetric matrix, JTT＝-JTT TThe matrix reflects the mutual coupling among the state variables of the system; rTTThe system is a symmetric positive definite matrix and reflects the dissipation characteristic of the system; u represents external input energy. It can be seen that the rectifier is non-linearly coupled. If h (x) x (1/2) xTMTTx is the total stored energy of the rectifier, the energy H (x) is derived over time as:
Figure BDA0002475741150000063
in the formula, xTJTTIf the two sides of the above equation are integrated with time, the stored energy of the rectifier is equal to the external supply energy minus the dissipated energy, and the system with the structural characteristics is passive.
Considering an error energy storage function of
Figure BDA0002475741150000064
In the formula, xe＝x-x*The derivative of the error energy over time is:
Figure BDA0002475741150000065
EL model formula (4) with xeThe variable is expressed as
Figure BDA0002475741150000066
Advance in
Figure BDA0002475741150000067
Fast convergence to zero requires injection of virtual damping RaAdding R simultaneously to both sides of formula (6)axeAnd let Rd＝RTT+RaTo do so by
Figure BDA0002475741150000068
The expression (5) is carried out
Figure BDA0002475741150000071
To satisfy
Figure BDA0002475741150000072
Convergence rate and RdIt is related. The passive control law is designed as
Figure BDA0002475741150000073
Substituting the matrix coefficients into equation (8) and letting udc,d＝dd uDC/2，udc,q＝dq uDCAnd/2, taking a voltage equation about the inductance in the equation set after expansion, and calculating the voltage equation by using udc,dAnd udc,qThe equation expressed is:
Figure BDA0002475741150000074
the formula is a voltage modulation equation of passive controlIn, R is the rectifier equivalent damping, RaIs a fixed virtual damping for the injection.
Novel algorithm based on EL type passive current control
Substituting the voltage modulation equation (9) into equation (3) can obtain:
Figure BDA0002475741150000075
the current error x of equation (12)eAs a variable, obtain a general formula of the equation set
Figure BDA0002475741150000076
Wherein k ═ R + Ra)/L。
Figure BDA0002475741150000077
Therefore, for the given EL type passive control law that the constant current component adopts the known rectifier internal resistance, the decoupling between state variables and the current tracking without static difference can be realized, and the tracking speed is determined by the injected virtual damping. However, the current tracking has no static error, and requires accurate estimation of the equivalent resistance of the system, the larger the injected virtual damping parameter in the linear working range, the faster the convergence speed, but the overlarge virtual damping can enter the nonlinear working range, and the system stability is affected.
If there is no estimated rectifier equivalent resistance in the passive control law (8), the fixed virtual damping R is still injectedaThe control mode of (2) is also substituted into a matrix coefficient and a corresponding modulation equation, and the current control equation after arrangement is as follows:
Figure BDA0002475741150000081
the current error x of equation (12)eFor the variables:
Figure BDA0002475741150000082
the general formula for the system of equations (13) can be written as:
Figure BDA0002475741150000083
wherein k is a constant current error feedback control coefficient, and k is Ra/L；r0(t) can be regarded as a variable including external disturbance of the system, equation (14) is a current closed-loop control equation, and if the error variable is caused to converge to zero as much as possible under the action of disturbance, x is multiplied by the two sides of the equationeObtaining:
Figure BDA0002475741150000084
to make the patient feel
Figure BDA0002475741150000085
Then
Figure BDA0002475741150000086
According to the inequality | a-b>A to b, which are required to satisfy
Figure BDA0002475741150000087
And (4) conditions.
Current tracking steady state error or range of static error and | r0(xeT) |/k is proportional and inversely proportional to k; the convergence speed decays approximately to the exponential power of k. Increasing k corresponds to increasing the injected virtual damping parameter, which improves the steady-state accuracy and dynamic response speed. But a higher virtual damping parameter RaIf the PWM modulation ratio exceeds the linear range, the PWM modulation ratio is easily increased, and other complex nonlinear phenomena such as overmodulation and the like are caused; if integral feedback is introduced, the control quantity is saturated, nonlinearity is generated, the system becomes sluggish, oscillation is easy to generate, and the current tracking control precision is influenced. For the case where the tracking is given as a non-linear periodic signal, the current tracking capability of injecting a fixed virtual damping is limited. Modifying a passive control law with injection of fixed virtual damping to nonThe passive control law of linear virtual damping injection is as follows:
Figure BDA0002475741150000088
wherein 0< alpha <1, and
ui＝f(Rv,xe,α)＝Rv|xe|αsign(xe) (17)
uifor the current feedback control law, RvTo inject a virtual damping coefficient, 0<α<1. And the improved passive control law is also substituted into the mathematical model to obtain a current feedback closed-loop control equation:
Figure BDA0002475741150000091
equation (18) can be written as:
Figure BDA0002475741150000092
equation (19) is also expressed in general form as:
Figure BDA0002475741150000093
in the formula, r0(t) is considered as an external disturbance to the system, k ═ RvAnd L. Multiplying both sides by | xe|αsign(xe) Obtaining:
Figure BDA0002475741150000094
to make the patient feel
Figure BDA0002475741150000095
Then
Figure BDA0002475741150000096
Also, according to the inequality | a-b | > | a | - | b |, therefore, it is necessary to satisfy
Figure BDA0002475741150000097
In general k>>|r0(xeT) |, and 0<α<1, then
Figure BDA0002475741150000098
Therefore, when the feedback gain k exceeds the disturbance | r0(t) | action Range, 0<α<A power-1 reduction reduces the steady state error by an order of magnitude. The nonlinear feedback steady state error is much smaller than the linear feedback steady state error of the constant damping injection. From the view of convergence speed and disturbance suppression capability, the nonlinear virtual damping injection control has higher efficiency of exponential power error attenuation than the injection of fixed virtual damping control in finite time error attenuation, the feedback of large power is not as good as the feedback of small power, and the efficiency of increasing feedback gain is not as good as the effect of reducing power.
The voltage modulation equation using the nonlinear current feedback control law is as follows:
Figure BDA0002475741150000101
Figure BDA0002475741150000102
wherein m is a modulation ratio and is usually 0<m<1, if m>1 overmodulation affects current tracking accuracy and stability, so current feedback u needs to be limitediAnd the value range of the modulation ratio m is met. Amplitude limiting is added to the nonlinear current feedback control law to prevent overmodulation.
f(Rv,xe,α)＝sat(Rv|xe|αsign(xe)) (25)
Wherein sat (x) is a saturation function,
Figure BDA0002475741150000103
novel passive current control algorithm for EL model of SSPBR converter
The topological structure of the SSTPBR conversion circuit is shown in figure 4, uPNFor the output voltage of a three-phase uncontrollable rectifier, also the input voltage of a cascade Boost circuit, uDCFor Boost output voltage, iLIs the inductor current in the Boost circuit. The inductor, the capacitor and the diode are all regarded as ideal elements, the power switch device is regarded as an ideal switch, and the PWM duty ratio of the power switch is set as uG. A voltage loop dynamic equation listed by a Boost circuit in the SSPBR converter is as follows:
Figure BDA0002475741150000104
in the formula, C is C1And C2And equivalent capacitance is connected in series.
The model of a Boost type DC/DC converter EL in SSPBR obtained by the formula (26) is as follows:
Figure BDA0002475741150000105
in the formula (I), the compound is shown in the specification,
Figure BDA0002475741150000106
Figure BDA0002475741150000107
according to Jb＝-Jb TIt is known that Boost type DC/DC converters have the EL equation passive property. Also set xbe＝xb-xb *Selecting an error energy storage function as follows:
Figure BDA0002475741150000111
and the error energy storage function is derived over time as:
Figure BDA0002475741150000112
to accelerate the rate of error energy convergence, a virtual damping R is injectedbaAnd R isba>>RbSo that:
Figure BDA0002475741150000113
in the formula, Rbd＝Rb+RbaThen the passive control law is:
Figure BDA0002475741150000114
in the formula, Rba＝diag{rba1,1/rba2}(rbai>0, i-1, 2) is a damping injection matrix. Substituting equation (28) into the parameter matrix yields:
Figure BDA0002475741150000115
can also be written as:
Figure BDA0002475741150000116
wherein D is 1-uPN/uDC，
Figure BDA0002475741150000117
Substituting equation (29) into the equation (26) for the current loop equation, yields:
Figure BDA00024757411500001111
using the current error of equation (31)
Figure BDA0002475741150000118
Is shown as
Figure BDA0002475741150000119
Wherein k is rba1/2LbMultiplication of both sides of the equation by xbe
Figure BDA00024757411500001110
Steady state error is zero, error is e-ktIs reduced.
If the nonlinear current feedback control law is
ug＝f(Rba,xbe,α)＝Rba|xbe|αsign(xbe) (34)
The passive control law is
Figure BDA0002475741150000121
By substituting equation (35) into the parameter matrix, the result is obtained
Figure BDA0002475741150000122
The equation (36) is also introduced into the equation for the voltage loop in equation (26) to obtain
Figure BDA0002475741150000123
The current error x of equation (37)beIs expressed as a variable
Figure BDA0002475741150000124
Multiplying both sides by xbeTo obtain
Figure BDA0002475741150000125
Figure BDA0002475741150000126
The steady state error is zero. When 0 is present<α<When 1, the expression for solving the formula (39) is
Figure BDA0002475741150000127
Error xbeWith t ═ xbe(0)|1-αThe/k (1-alpha) decays to zero for a finite time.
It can be seen that although the steady-state error is zero in the current feedback control law of linear damping injection and non-linear damping injection, the analysis of the error attenuation characteristic shows that 0<α<Nonlinear control law of 1 time, decaying to zero in finite time, and linear control law with e-ktThe transient error is greater than the nonlinear control law.
The method does not need to be used as a disturbed load parameter, does not need to detect the input voltage of a Boost circuit, and does not need to utilize the nonlinear current feedback control rate of output voltage participating in operation
ug＝sat(Rba|xbe|αsign(xbe)) (41)
In the formula, 0<α<1, control quantity ugComparing with triangular wave to obtain PWM signal u of power switchG。
The NTLUTHR rectifier is controlled by adopting a voltage and current double closed-loop control method, the voltage outer loop adopts a traditional PI control method, and the current inner loop adopts the novel passive current tracking control strategy. The NTLUTHR pulse width modulation uses SVPWM modulation method, and the neutral point potential balance control at the DC side is realized by adjusting the action time of the redundant small vector. The control block diagram of the NTLUTHR rectifier is shown in fig. 5.
According to the obtained new EL-type passive current control algorithm and the new SSPBR converter EL model passive current control algorithm, the three-level unidirectional T-shaped rectifier is controlled based on the new EL-type passive current control algorithm, and the SSPBR circuit is controlled based on the new SSPBR converter EL model passive current control algorithm.
In order to prove the feasibility of the NTLUTHR rectifier topological structure and the proposed current tracking control method, an NTLUTHR circuit model is established in a Matlab/Simulink simulation environment. The simulation parameter is that the power line voltage is UN34V, DC bus voltage output UDC80V, DC bus series capacitor C1＝C2TLUTR ac side inductor L1000 μ Fv2mH SSTPBR with inductor L connected in seriesb20mH, ac side inductor LzSwitching frequency f of TLUTR rectifier 30 muHTLUTRSwitching frequency f of SSTPSR rectifier at 20kHzBOOST＝5kHz。
The waveforms of the input currents of the two parallel rectifiers in the hybrid rectifier are shown in fig. 6, wherein the input currents of the SSTPBR circuit are respectively 6-frequency-doubled cosine waveform, flat-top + 6-frequency-doubled cosine, flat-top + 6-frequency-doubled circular arc waveform, and flat-top + 6-frequency-doubled pseudo-triangular waveform. Different waveforms and different form factors affect the total loss of the hybrid rectifier, so the optimal form and form factor are selected to optimize the system efficiency for different circuit topologies and device parameters.
The peak generated by the superposition of parallel interleaving currents can be eliminated and the electromagnetic interference is inhibited by adding the inductor Lz for delaying the current change at the alternating current side of the improved hybrid rectifier SSTPBR and the TLUTR and SSTPBTR passive current control strategies; the current tracking control precision is improved, and the THD of the total input current is reduced.
As shown in fig. 7, the Boost circuit current tracking control waveforms in SSTPBR (fig. 7(a1), (b1), (c1)), and the corresponding SSTPBR input current waveforms (fig. 7(a2), (b2), (c 2)). The purple red in the figure is a given current waveform of the Boost circuit,blue is the tracking current waveform. FIG. 7(a1) shows a conventional passive current control method, damping coefficient rba128. FIG. 7(b1) also shows the fixed damping injection control method, damping coefficient rba1Fig. 7(c1) shows a passive current control method for nonlinear damping injection, with damping coefficient r being 800ba128, α is 0.25. Fig. 7(a2), 9(b2), and 9(c2) correspond to current waveforms of the SSTPBR input at different Boost tracking currents, respectively.
As shown in fig. 8, for the TLUTR input current in d-q coordinate system, the id-axis current tracking control waveform, magenta for the given current waveform, and blue for the tracking current waveform. FIG. 8(a) is a diagram of a conventional current control method with fixed virtual damping injection, damping coefficient RaFig. 8(b) shows a current control method of nonlinear damping injection with the same damping coefficient R as 30v30, α is 0.06. It can be seen that the non-linear control method has a smaller tracking error than the linear control.
As shown in fig. 9, (a) and (b) in fig. 9 are total input waveforms of the hybrid rectifier obtained by the conventional passive current control method, and fig. 9(c) is total input waveform of the hybrid rectifier obtained by the nonlinear control method.
In the embodiment of the invention, on the basis of analyzing the topological structure and the working principle of the existing UHTPVSR circuit, an improved circuit which is added with compensation inductance and reduces the sudden change of SSTPSR input current is provided. TLUTR and SSTPBR rectifier EL mathematical models in an NTLUTHR rectifier are respectively established. Aiming at TLUTR, a nonlinear virtual damping injected passive current control algorithm which accords with modulation ratio constraint under a d-q coordinate system is provided; a nonlinear virtual damping injection type direct current feedback passive control algorithm meeting duty ratio constraints is provided for an SSPBR rectifier. An NTLUTHR system simulation model is established in a Matlab/Simulink simulation environment, and feasibility and accuracy of a control strategy are verified. An experimental principle prototype is further developed, and experimental results show that high input current sine degree, high current control precision, low THD and power factor close to 1 of an NTLUTHR alternating current side are achieved, and feasibility and effectiveness of a new passive current control strategy are proved.
Those of skill would further appreciate that the various illustrative components and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied in hardware, a software module executed by a processor, or a combination of the two. A software module may reside in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims (1)

1. A nonlinear passive current control method is applied to a three-level unidirectional T-type hybrid rectifier, wherein the three-level unidirectional T-type hybrid rectifier comprises a single-switch three-phase boost rectifier circuit and a three-level unidirectional T-type rectifier circuit connected with the single-switch three-phase boost rectifier circuit in parallel, a compensation inductor is connected with an alternating current input end of the single-switch three-phase boost rectifier circuit in series, and the method comprises the following steps:
controlling the three-level unidirectional T-shaped rectifier circuit based on a three-level unidirectional T-shaped rectifier Euler-Lagrange equation type passive current control algorithm;
controlling a single-switch three-phase boost rectifier circuit based on a single-switch three-phase boost rectifier Euler-Lagrange equation type passive current control algorithm;
the Euler-Lagrange equation type passive current control algorithm of the three-level unidirectional T-type rectifier comprises the following steps:
Figure FDA0003147388550000011
wherein 0< alpha <1, and
ui＝f(Rv,xe,α)＝Rv|xe|αsign(xe) (17)
uifor the current feedback control law, MTTA positive definite diagonal matrix is formed; j. the design is a squareTTIs an antisymmetric matrix, u represents the external input energy, x is the system state variable, RvTo inject a virtual damping coefficient, 0<α<1, substituting an improved passive control law into a mathematical model to obtain a current feedback closed-loop control equation;
f(Rv,xe,α)＝sat(Rv|xe|αsign(xe))
in the formula, 0<α<1，xeSat (x) is a saturation function for the current error,
Figure FDA0003147388550000012
the Euler-Lagrange equation type passive current control algorithm of the single-switch three-phase boost rectifier comprises the following steps:
in the circuit topology of single-switch three-phase boost rectifier, uPNFor the output voltage of a three-phase uncontrollable rectifier, also the input voltage of a cascade Boost circuit, uDCFor Boost output voltage, iLFor the inductive current in the Boost circuit, an inductor, a capacitor and a diode are all regarded as ideal elements, a power switch device is regarded as an ideal switch, and the PWM duty ratio of the power switch is set as uG(ii) a Single switch three-phase boost rectificationA Boost circuit in the device lists a voltage loop dynamic equation;
the Boost type DC/DC converter EL model in the single-switch three-phase Boost rectifier can be obtained as follows:
Figure FDA0003147388550000021
in the formula (I), the compound is shown in the specification,
Figure FDA0003147388550000022
Figure FDA0003147388550000023
according to Jb＝-Jb TThe Boost type DC/DC converter has the passive property of EL equation and is also set to xbe＝xb-xb *Selecting an error energy storage function as follows:
Figure FDA0003147388550000024
and the error energy storage function is derived over time as:
Figure FDA0003147388550000025
to accelerate the rate of error energy convergence, a virtual damping R is injectedbaAnd R isba>>RbSo that:
Figure FDA0003147388550000026
in the formula, Rbd＝Rb+RbaThen the passive control law is:
Figure FDA0003147388550000027
in the formula, Rba＝diag{rba1,1/rba2}(rbai>0, i-1, 2) is the damping injection matrix, and equation (28) is substituted into the parameter matrix, yielding:
Figure FDA0003147388550000028
can also be written as:
Figure FDA0003147388550000029
wherein D is 1-uPN/uDC，
Figure FDA00031473885500000210
Substituting equation (29) into the equation (26) for the current loop equation, yields:
Figure FDA0003147388550000031
using the current error of equation (31)
Figure FDA0003147388550000032
Is shown as
Figure FDA0003147388550000033
Wherein k is rba1/2LbMultiplication of both sides of the equation by xbe
Figure FDA0003147388550000034
Steady state error is zero, error is e-kt(ii) a velocity decay;
let the nonlinear current feedback control law be
ug＝f(Rba,xbe,α)＝Rba|xbe|αsign(xbe) (34)
The passive control law is
Figure FDA0003147388550000035
By substituting equation (35) into the parameter matrix, the result is obtained
Figure FDA0003147388550000036
The equation (36) is also introduced into the equation for the voltage loop in equation (26) to obtain
Figure FDA0003147388550000037
The current error x of equation (37)beIs expressed as a variable
Figure FDA0003147388550000038
Multiplying both sides by xbeTo obtain
Figure FDA0003147388550000039
Figure FDA00031473885500000310
The steady state error is zero; when 0 is present<α<When 1, the expression for solving the formula (39) is
Figure FDA00031473885500000311
Error xbeWith t ═ xbe(0)|1-αA limited time decay of/k (1- α) to zero;
the method does not need to be used as a disturbed load parameter, does not need to detect the input voltage of a Boost circuit, and does not need to utilize the nonlinear current feedback control rate of output voltage participating in operation
ug＝sat(Rba|xbe|αsign(xbe))；
In the formula, the same is 0<α<1，RbaFor virtual damping, xbeSat (x) is a saturation function for the current error,
Figure FDA0003147388550000041
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