CN105811448A - Switching theory-based wind electricity DC bus voltage control system and method - Google Patents

Switching theory-based wind electricity DC bus voltage control system and method Download PDF

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Publication number
CN105811448A
CN105811448A CN201610327838.0A CN201610327838A CN105811448A CN 105811448 A CN105811448 A CN 105811448A CN 201610327838 A CN201610327838 A CN 201610327838A CN 105811448 A CN105811448 A CN 105811448A
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China
Prior art keywords
switching
way
storage device
energy storage
current transformer
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CN201610327838.0A
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CN105811448B (en
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张承慧
李珂
王帆
田崇翼
严毅
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Shandong University
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Shandong University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E70/00—Other energy conversion or management systems reducing GHG emissions
    • Y02E70/30—Systems combining energy storage with energy generation of non-fossil origin

Abstract

The invention discloses a switching theory-based wind electricity DC bus voltage control system and method. The switching theory-based wind electricity DC bus voltage control system comprises a rectifier, a grid-connected inverter, a bi-directional DC/DC converter, a controller and an energy storage device, wherein the rectifier is used for converting AC output by a permanent magnet synchronous generator to DC; the grid-connected inverter is used for inverting the DC to constant-frequency and constant-voltage power frequency AC to be transformed into a grid; a DC side of the grid-connected inverter is connected to a draught fan DC side via the bi-directional DC/DC converter; the energy storage device is connected in parallel with a DC bus via the bi-directional DC/DC converter, and a working state of the energy storage device is in a constant bus voltage mode; and the controller is used for controlling on/off of the bi-directional DC/DC converter. In the system and the method, influence of all units to bus voltage is balanced, so that voltage surge caused by unmated power is effectively suppressed and reduced, the dynamic response speed of the system is accelerated, and the dynamic system power balance is ensured.

Description

A kind of wind power direct current busbar voltage theoretical based on switching controls system and method
Technical field
The present invention relates to a kind of wind power direct current busbar voltage theoretical based on switching and control system and method.
Background technology
In wind generator system, when power of fan changes, the power that generated output absorbs with energy-storage units, grid-connected side does not mate, and big ups and downs will occur DC voltage；If DC voltage fluctuates, it is possible to cause motor side current transformer power imbalances, grid stability is produced impact.
For suppressing DC bus-bar voltage fluctuation, existing method mostly is and is connected in parallel on dc bus by energy storage device by two-way DC/DC, works in permanent busbar voltage pattern.When DC bus-bar voltage raises, energy storage device, by the charging of two-way DC/DC changer, absorbs energy；When DC bus-bar voltage declines, energy storage device is put a little by two-way DC/DC changer, releases energy.
But when constant voltage unit adopts traditional controller, current perturbation change causes change in voltage, and DC/DC controller Voltage loop produces error, and due to the existence of regulating time and overshoot, electric current can not quickly and accurately adjust, and causes that busbar voltage is unstable.
So, for being operated in the DC/DC current transformer under the constant voltage mode of high-pressure side, it is badly in need of a rational control method and can reduce response time, quickly stabilize voltage.
Summary of the invention
The present invention is to solve the problems referred to above, propose a kind of wind power direct current busbar voltage theoretical based on switching and control system and method, the present invention is at the DC side of permanent-magnet synchronous wind-electricity integration system, energy storage device is added by two-way DC/DC converter unit, set up buck-boost circuit model, analyze the current perturbation impact on busbar voltage, DC/DC controller adds in modeling process current perturbation feedforward, a kind of switching law of design controls switch, energy storage device is made to absorb to dc bus rapidly and accurately or release energy, power is balanced, DC voltage is stabilized, when generated output changes, suppress the fluctuation of wind power system DC bus-bar voltage.
To achieve these goals, the present invention adopts the following technical scheme that
A kind of wind power direct current busbar voltage theoretical based on switching controls system, including commutator, combining inverter, two-way DC/DC current transformer, controller and energy storage device, wherein, the alternating current that magneto alternator exports is converted to unidirectional current by described commutator, and the industrial-frequency alternating current that its inversion is constant frequency and constant voltage is sent into electrical network by combining inverter；
The DC side of combining inverter accesses blower fan DC side by two-way DC/DC current transformer, and energy storage device is connected in parallel on dc bus by two-way DC/DC current transformer, and duty is permanent busbar voltage pattern；
Described controller controls cut-offfing of two-way DC/DC current transformer.
Further, described two-way DC/DC current transformer includes the first switching tube and second switch pipe, and second switch pipe is connected to one end of combining inverter, connects energy storage device, described first paralleled power switches is at energy storage device two ends, and controller triggers the first switching tube and the work of second switch pipe.
Preferably, described switching tube is insulated gate bipolar transistor.
Described two-way DC/DC current transformer is connected in parallel on the dc bus of combining inverter.
Described controller is that PI controls to control combination with switching theory.
A kind of wind power direct current busbar voltage control method theoretical based on switching, comprises the following steps:
(1) voltage of each element of Real-time Collection permanent-magnet synchronous wind-electricity integration system, current value, based on Kirchhoff's second law and current law, calculate next and control the state variable of two-way DC/DC current transformer during cycle；
(2) according to the power expectation balance point set, minimum projection's method is given, it is determined that switching law；
(3) determined the first switching tube of two-way DC/DC current transformer and the state of second switch pipe by projection value according to switching law, two-way DC/DC current transformer is made to be operated in buck or boost state, energy storage device is made to absorb to dc bus or release energy, balanced power.
In described step (2), switching law is that free position can select that a vector field pointing to expectation balance point all the time.
In described step (3), when the power of magneto alternator is more than grid-connected power, it is ensured that second open the light pipe conducting, two-way DC/DC current transformer is operated in buck pattern, energy storage device absorb energy.
In described step (3), when the power of magneto alternator is less than grid-connected power, it is ensured that the first switching tube conducting, two-way DC/DC current transformer is operated in boost pattern, and energy storage device releases energy.
The invention have the benefit that
(1) DC/DC current transformer modeling method is without approximate processing, and precision is high, and the feature that can embody discrete event dynamic system embodies again the feature of continuous time dynamic system；
(2) in conjunction with PI control and switching control, it is possible to be precisely controlled DC/DC current transformer, it is prevented that flow problem crossed by the device caused because of overshoot；
(3) coordinate each unit impact on busbar voltage, effectively suppress to reduce power and do not mate the voltge surge caused, improve system dynamics response speed, it is ensured that system power dynamic equilibrium.
Accompanying drawing explanation
Fig. 1 is permanent magnetism synchronous wind generating grid-connected system structural representation in the present invention；
Fig. 2 is DC/DC converter topology figure；
Fig. 3 is the control flow chart of handoff algorithms；
Fig. 4 is the calculating procedure chart of handoff algorithms；
Fig. 5 is the voltage x current instruction vector x of DC/DC current transformer*Produce figure；
Fig. 6 be DC/DC current transformer under boost pattern, use conventional PI control DC bus-bar voltage curve chart；
Fig. 7 be DC/DC current transformer under boost pattern, use switching theory control DC bus-bar voltage curve chart.
Detailed description of the invention:
Below in conjunction with accompanying drawing, the invention will be further described with embodiment.
Problem to be solved by this invention is, when generated output changes, it is suppressed that the fluctuation of wind power system DC bus-bar voltage.By a kind of wind power direct current busbar voltage stable control method theoretical based on switching, DC side in permanent-magnet synchronous wind-electricity integration system, energy storage device is added by two-way DC/DC converter unit, set up buck-boost circuit model, analyze the current perturbation impact on busbar voltage, DC/DC controller adds in modeling process current perturbation feedforward, a kind of switching law of design controls switch, energy storage device is made to absorb to dc bus rapidly and accurately or release energy, power is balanced, and DC voltage is stabilized.
It is illustrated in figure 1 the grid-connected system of wind driven generator that the invention process example provides, including magneto alternator (PMSM), generator rectifier, combining inverter.The rectified device of alternating current of electrical power generators output is converted to unidirectional current, sends into electrical network again through the industrial-frequency alternating current that inverter inversion is constant frequency and constant voltage.At DC side by two-way DC/DC current transformer parallel connection energy storage device, energy storage device accesses blower fan DC side by two-way DC/DC.As in figure 2 it is shown, two-way DC/DC is by two insulated gate bipolar transistors (Insulate-GateBipolarTransisitor, IGBT) being parallel with fly-wheel diode, resistance R, inductance L, electric capacity C forms.
Two-way DC/DC current transformer high-pressure side is connected on dc bus, then capacitance terminal voltage is busbar voltage.High-pressure side input current i0Electric current i is exported with low-pressure side1, flow into electric capacity C.
To the optimal control flow process of two-way DC/DC current transformer as shown in Figure 3.
According to control flow, as shown in Figure 4, concrete calculating process is as follows for computational methods:
Input current i0Equal to wind side currents iwindWith also current on line side igridDifference:
i0=iwind-igrid(1)
Making inductive current is iL, high side voltage is udc, energy storage device terminal voltage is us, inductance value is L, and the resistance value connected with inductance is R, and high-pressure side capacitance is C, and state variable vector isBased on Kirchhoff's second law and current law, state equation during switch S1 Guan Bi is expressed as:
x · = A 1 x + B 1 - - - ( 2 )
A 1 = - R / L 0 0 0 , B 1 = u s / L i 0 / C
State equation when switch S1 disconnects is expressed as:
x · = A 2 x + B 2 - - - ( 3 )
A 2 = - R / L - 1 / L 1 / C 0 , B 2 = u s / L i 0 / C
Switched system is one and by a serial continuous or discrete subsystem and coordinates to rise between these subsystems the hybrid system that the rule of switching forms.Above-mentioned two-way DC/DC current transformer is a kind of switched system, and formula (2) and formula (3) respectively describe its subsystem under different on off states.
Minimum projection's method: for a certain switched system(t, x) { 1,2...m} is switching signal to ∈ to σ.Assume that equilibrium point is initial point, then subsystem fσ(t,x)(x (t), u (t)) being projected as on state variable x (t):
Γσ(t,x)(x)=xTfσ(t,x)(x(t),u(t))/||x||,x≠0(4)
Work as Γσ(t,x)During (x) < 0, it was shown that system is along vector field fσ(t,x)(x (t), u (t)) is constantly to equilibrium point convergence.Projection value is more little, and the convergence rate of system is more fast.
The expectation balance point assuming system is x*, based on minimum projection's method, design switching law:
σ (t, x)=argmin{ (x-x*)TPfσ(t,x)(x(t),u(t))}(5)
For two-way DC/DC current transformer, select energy-storage travelling wave tube value as positive definite matrix P, then
P = L 0 0 C - - - ( 6 )
The expectation balance point assuming system is x*, based on minimum projection's method, design switching law:
&sigma; ( t , x ) = arg min i = 1 , 2 { ( x i ( t + &Delta; T ) - x * ) T P ( x i ( t + &Delta; T ) - x * ) } - - - ( 7 )
This switching law is to can select that is pointed to an equilibrium point x all the time in free position*Vector field.
X (t) represents state variable vector during current time t；If the control cycle is Δ T, then xi(t+ Δ T) represents under i-th subsystem, state variable vector during next control moment in cycle t+ Δ T, its solution procedure such as formula (8),
x i ( t + &Delta; T ) = G i &CenterDot; x ( t ) + H i G i = e A i &CenterDot; &Delta; T H i = ( &Integral; 0 &Delta; T e A i &CenterDot; &Delta; T d t ) B i - - - ( 8 )
Difference quotient is replaced to carry out discretization by the business of state variable difference:
xi(t+ Δ T)=(Ai·ΔT+Ie)·x(t)+Bi·ΔT(9)
IeFor unit matrix.
Determine equilibrium pointurefGive for DC voltage, current instruction value irefProduced through PI controller by voltage error, as shown in Figure 5.
Making the power that electromotor sends is Pw, grid-connected power is Pg, work as Pw>PgTime, S2 triggers, and DC/DC is operated in buck pattern, and energy storage device absorbs energy；Work as Pw<PgTime, S1 triggers, and DC/DC is operated in boost pattern, and energy storage device releases energy.
MATLAB is used to emulate:
When 1s, wind speed changes, and wind power is reduced to 3.6kW by 14.4kW, and DC bus-bar voltage is as shown in Figure 5,6.
By comparison of wave shape, using switching theoretical method to be controlled, DC bus-bar voltage remains stable for, and is absent from fluctuation.
The specific embodiment of the present invention is described in conjunction with accompanying drawing although above-mentioned; but not limiting the scope of the invention; one of ordinary skill in the art should be understood that; on the basis of technical scheme, those skilled in the art need not pay various amendments or deformation that creative work can make still within protection scope of the present invention.

Claims (9)

1. one kind controls system based on the wind power direct current busbar voltage that switching is theoretical, it is characterized in that: include commutator, combining inverter, two-way DC/DC current transformer, controller and energy storage device, wherein, the alternating current that magneto alternator exports is converted to unidirectional current by described commutator, and the industrial-frequency alternating current that its inversion is constant frequency and constant voltage is sent into electrical network by combining inverter；
The DC side of combining inverter accesses blower fan DC side by two-way DC/DC current transformer, and energy storage device is connected in parallel on dc bus by two-way DC/DC current transformer, and duty is permanent busbar voltage pattern；
Described controller controls cut-offfing of two-way DC/DC current transformer.
2. a kind of wind power direct current busbar voltage theoretical based on switching controls system as claimed in claim 1, it is characterized in that: described two-way DC/DC current transformer includes the first switching tube and second switch pipe, second switch pipe is connected to one end of combining inverter, connect energy storage device, described first paralleled power switches is at energy storage device two ends, and controller triggers the first switching tube and the work of second switch pipe.
3. a kind of wind power direct current busbar voltage theoretical based on switching controls system as claimed in claim 1, it is characterized in that: described switching tube is insulated gate bipolar transistor.
4. a kind of wind power direct current busbar voltage theoretical based on switching controls system as claimed in claim 1, it is characterized in that: described two-way DC/DC current transformer is connected in parallel on the dc bus of combining inverter.
5. a kind of wind power direct current busbar voltage theoretical based on switching controls system as claimed in claim 1, it is characterized in that: described controller is that PI controls to control combination with switching theory.
6., based on the wind power direct current busbar voltage control method that switching is theoretical, it is characterized in that: comprise the following steps:
(1) voltage of each element of Real-time Collection permanent-magnet synchronous wind-electricity integration system, current value, based on Kirchhoff's second law and current law, calculate next and control the state variable of two-way DC/DC current transformer during cycle；
(2) according to the power expectation balance point set, minimum projection's method is given, it is determined that switching law；
(3) determined the first switching tube of two-way DC/DC current transformer and the state of second switch pipe by projection value according to switching law, two-way DC/DC current transformer is made to be operated in buck or boost state, energy storage device is made to absorb to dc bus or release energy, balanced power.
7. a kind of wind power direct current busbar voltage control method theoretical based on switching as claimed in claim 6, is characterized in that: in described step (2), switching law is that free position can select that a vector field pointing to expectation balance point all the time.
8. a kind of based on switching theoretical wind power direct current busbar voltage control method as claimed in claim 6, it is characterized in that: in described step (3), when the power of magneto alternator is more than grid-connected power, ensure the conducting of second switch pipe, two-way DC/DC current transformer is operated in buck pattern, and energy storage device absorbs energy.
9. a kind of based on switching theoretical wind power direct current busbar voltage control method as claimed in claim 6, it is characterized in that: in described step (3), when the power of magneto alternator is less than grid-connected power, ensure the first switching tube conducting, two-way DC/DC current transformer is operated in boost pattern, and energy storage device releases energy.
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CN113937814A (en) * 2021-10-26 2022-01-14 中国华能集团清洁能源技术研究院有限公司 Double-wind-wheel double-motor direct-current series-parallel switching unified grid-connected system

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CN113937814A (en) * 2021-10-26 2022-01-14 中国华能集团清洁能源技术研究院有限公司 Double-wind-wheel double-motor direct-current series-parallel switching unified grid-connected system
CN113937814B (en) * 2021-10-26 2023-11-07 中国华能集团清洁能源技术研究院有限公司 Double wind wheel double motor direct current series-parallel connection switching unified grid-connected system

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