CN110971009A - Control method of wireless power transmission system - Google Patents
Control method of wireless power transmission system Download PDFInfo
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- CN110971009A CN110971009A CN201910987980.1A CN201910987980A CN110971009A CN 110971009 A CN110971009 A CN 110971009A CN 201910987980 A CN201910987980 A CN 201910987980A CN 110971009 A CN110971009 A CN 110971009A
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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
- H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
- H02J50/10—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling
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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
- H02J50/00—Circuit arrangements or systems for wireless supply or distribution of electric power
- H02J50/10—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling
- H02J50/12—Circuit arrangements or systems for wireless supply or distribution of electric power using inductive coupling of the resonant type
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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
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Abstract
The invention discloses a control method of a wireless electric energy transmission system, which comprises the steps of establishing a mathematical model of the wireless electric energy transmission system; and analyzing and calculating according to the system mathematical model to obtain the optimal duty ratio and the optimal working frequency, and predicting the output power of the system, wherein the process of establishing the mathematical model comprises the following steps: respectively calculating and obtaining the input power, the output power and the system working frequency of the wireless electric energy transmission system; according to the equivalent impedance ZrBy conversion of angular frequency to obtain ZrAfter the formula is converted, the load resistance R is respectively obtainedLAnd coil mutual inductance M; obtaining the load resistance R according to the timing diagramLThe coil mutual inductance M and the angle; the mathematical expression of the cost function is established by utilizing the new algorithm model predictive control, the optimal duty ratio of ideal output power is obtained through the minimization of the target function, the gain adjustment and the measurement are not needed, the cost and the complexity of the WPT system are greatly reduced, and the transmission efficiency of the system is improvedThe improvement is remarkable.
Description
Technical Field
The invention relates to the technical field of wireless power transmission, in particular to a control method of a wireless power transmission system.
Background
Wireless Power Transmission (WPT) is a novel power transmission mode, the traditional wired constraint is eliminated, the flexibility, the attractiveness and the safety of the power utilization equipment are greatly improved, faults such as line leakage are reduced, and personal safety and economy are guaranteed. The WPT system brings many technical difficulties in succession, and the misalignment between the coupling coils is inevitable, which causes the mutual inductance variation and thus the output power variation, and therefore, the control of the output power is indispensable. In order to reduce the cost, size and complexity of the WPT system, the controller should be implemented on the primary side without any measurement and communication equipment on the secondary side. The primary side control can realize the adjustment of the output voltage of the inverter through the inverter voltage control, and the phase shift control is a common technology in the WPT system because the output voltage does not contain a direct current component. Its harmonic content is lower than Asymmetric Duty Cycle (ADC) control and Asymmetric Clamped Mode (ACM) control techniques.
In the prior art, in order to adjust the output power according to the primary-side control method, the load resistance and the mutual inductance must be recognized throughout the operation. By switching an extra compensation capacitor to the main circuit, the system will operate in two different modes in which the identification equations for load impedance and mutual inductance can be derived. But the necessity of an additional capacitor switch and control increases the number of components, cost and complexity of the WPT system. The on-line estimation method based on the Goertzel algorithm needs to estimate the mean square errors corresponding to all mutual inductance values, and the method has large calculation amount, is difficult to realize and takes time. Although both resistance and mutual inductance can be estimated by measuring input voltage and current, it is a mathematical problem based on resonant frequency, which is extremely challenging.
Disclosure of Invention
In order to find a more effective implementation scheme, the invention provides a control method of a wireless power transmission system, which obtains the optimal duty ratio of ideal output power through the minimization of a target function, does not need to adjust gain and measure, greatly reduces the cost and complexity of the WPT system, and remarkably improves the transmission efficiency of the system.
In order to achieve the above object, the present invention discloses a control method of a wireless power transmission system, comprising:
establishing a mathematical model of the wireless electric energy transmission system;
and analyzing and calculating according to the system mathematical model to obtain the optimal duty ratio and the optimal working frequency, and predicting the output power of the system.
Preferably, the establishing a mathematical model of the wireless power transmission system includes:
respectively calculating and obtaining the input power, the output power and the system working frequency of the wireless electric energy transmission system;
according to the equivalent impedance ZrBy conversion of angular frequency to obtain ZrAfter the formula is converted, the load resistance R is respectively obtainedLAnd coil mutual inductance M;
obtaining the load resistance R according to the timing diagramLThe coil mutual inductance M and the angle;
and establishing a mathematical expression of the cost function by using the new algorithm model predictive control.
Preferably, the input power and the output power are respectively obtained through an equivalent circuit, and the working frequency of the system is obtained according to the input power and the output power, wherein the input power isThe output power is
Preferably, the equivalent impedance Zr=Rr+jXrWherein R isrAs an equivalent resistance component, XrIs equivalent reactance component and converts the angular frequency omega into the angular frequency omega of the system working at zero phase02Obtaining the R of the system frequency at the zero phaserAnd XcrAnd obtaining a new ZrMathematical expression, sequentially obtaining load resistance R according to transformation formulaLAnd a coil mutual inductance M.
Preferably, the load resistor RLComprises the following steps:
preferably, the equivalent impedances R are respectively obtained by obtaining voltage relational expressions at two sides of the inverter according to the conduction of the MOSFET (metal-oxide-semiconductor field effect transistor) of the upper and lower bridge armsLThe relation of the mutual inductance M of the coil and the angle,
preferably, the specific process of establishing the mathematical expression of the cost function by using the new algorithm model predictive control is as follows:
determining the relationship between the output power and the duty ratio at any moment, and respectively deriving the relational expressions of the output power, the input direct-current bus voltage, the load equivalent resistance, the mutual inductance coefficient and the duty ratio D;
determining a relational expression between the output power and the duty ratio D at the next moment of any moment;
establishing a cost function according to the relation between the output power and the duty ratio D at any moment and the next moment
Preferably, the relationship between the output power and the duty ratio D at any time is as follows:
the relation between the output power and the duty ratio D at the next moment of any moment is as follows:
preferably, the optimal duty cycle and the optimal operating frequency are obtained through analysis and calculation according to the system mathematical model, and the specific process of predicting the output power of the system is as follows:
determining the optimal solution of the cost function J, namely the minimum value of the cost function J according to the expression of the cost function, and calculating the obtained load equivalent resistance R according to the known input voltageLAnd obtaining the optimal duty ratio D (K) by the coil mutual inductance M.
Preferably, the MOSFET is controlled to be switched on and off according to the obtained optimal duty ratio D (K), and the inversion frequency of the system is determined.
Compared with the prior art, the control method of the wireless power transmission system has the following beneficial effects:
the technical scheme includes that a new control algorithm is used for predicting and controlling a model MPC to obtain a circuit equivalent diagram of a WPT system, a mathematical expression of mutual inductance coefficients of a load resistor and a coil is established to obtain a mathematical expression of output power and a duty ratio D, and an optimal function expression J is established through the MPC algorithm to obtain the optimal duty ratio D. Compared with the traditional methods, namely a PWM carrier method and a PI control method, the controller has higher response speed than the traditional PI controller. The optimal duty ratio is obtained in real time according to the load resistance change, the system efficiency is higher, the gain does not need to be adjusted, the measurement is not needed, and the cost, the size and the complexity of the WPT system are greatly reduced.
Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
figure 1 is an equivalent circuit diagram a of a WPT system;
figure 2 is an equivalent circuit diagram b of the WPT system;
FIG. 3 is a simplified circuit diagram c of FIG. 1 obtained by equivalent conversion of the circuit impedance to the primary side;
FIG. 4 is a general equivalent diagram of a wireless power transmission system of the present invention;
fig. 5 is a schematic diagram of the phase shift control of the full bridge inverter according to the gating signal and the corresponding waveform of the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the drawings are illustrative only and should not be construed as limiting the invention.
Referring to fig. 1 to 5, the present invention discloses a method for controlling a wireless power transmission system, including:
establishing a mathematical model of the wireless electric energy transmission system;
the establishing of the mathematical model of the wireless power transmission system comprises the following steps:
respectively calculating and obtaining the input power, the output power and the system working frequency of the wireless electric energy transmission system;
wherein, the input power and the output power are respectively obtained through the circuit basic formulas of the equivalent circuit diagram b and the equivalent circuit diagram c, the working frequency of the system is obtained according to the input power and the output power, and the input power isThe output power isThe output power and the input power are obtained from equivalent circuit diagrams 2 and 3 according to basic formulas of the circuit, and R1, L1, R2, L2, C2 and M (design values) in the circuit are known.
While operating at zero phase angle frequency depending on frequency to obtain a value of C1, i.e. The first order zero phase angle frequency is designed to be the second order resonant frequency.
According to the equivalent impedance ZrBy conversion of angular frequency to obtain ZrAfter the formula is converted, the load resistance R is respectively obtainedLAnd coil mutual inductance M;
the equivalent impedance Zr=Rr+jXrWherein R isrAs an equivalent resistance component, XrFor equivalent reactive components, the angular frequency ω is converted into an angular frequency ω at which the system operates at zero phase02Obtaining the R of the system frequency at the zero phaserAnd XcrAnd obtaining a new ZrMathematical expression, sequentially obtaining load resistance R according to transformation formulaLAnd a coil mutual inductance M.
Obtaining RrAnd XcrThen obtaining new ZrThe mathematical expression is that the expression is,
and sequentially obtaining the load resistance R according to a transformation formulaLAnd a coil mutual inductance M.
obtaining the load resistance R according to the timing diagramLThe coil mutual inductance M and the angle;
obtaining voltage relational expressions of two sides of the inverter according to the conduction of the MOSFET (metal-oxide-semiconductor field effect transistor) tubes of the upper bridge arm and the lower bridge arm, and respectively calculating equivalent impedance RLThe relation of the mutual inductance M of the coil and the angle,
and establishing a mathematical expression of the cost function by using the new algorithm model predictive control.
The specific process of establishing the mathematical expression of the cost function by utilizing the new algorithm model predictive control is as follows:
determining the relationship between the output power and the duty ratio at any moment, and respectively deriving the relational expressions of the output power, the input direct-current bus voltage, the load equivalent resistance, the mutual inductance coefficient and the duty ratio D;
determining a relational expression between the output power and the duty ratio D at the next moment of any moment;
establishing a cost function according to the relation between the output power and the duty ratio D at any moment and the next moment
And analyzing and calculating according to the system mathematical model to obtain the optimal duty ratio and the optimal working frequency, and predicting the output power of the system.
The relation between the output power and the duty ratio D at any moment is as follows:
the relation between the output power and the duty ratio D at the next moment of any moment is as follows:
it should be noted that, in this scheme, fig. 1 is an equivalent circuit diagram of the WPT system, and a simplified circuit diagram of fig. c can be obtained by equivalent conversion of circuit impedance to the primary side, and a vector Zin is an equivalent impedance of the whole circuit as viewed from the power supply terminal,where Zr is Rr + jXr (in abc the primary side of the coil is counted as the secondary side, etcThe effective impedance),
the optimal duty ratio and the optimal working frequency are obtained through analysis and calculation according to the system mathematical model, and the specific process of predicting the output power of the system is as follows:
determining the optimal solution of the cost function J, namely the minimum value of the cost function J according to the expression of the cost function, and calculating the obtained load equivalent resistance R according to the known input voltageLAnd obtaining the optimal duty ratio D (K) by the coil mutual inductance M.
And controlling the on and off of the MOSFET according to the obtained optimal duty ratio D (K) to determine the inversion frequency of the system, wherein the controller has higher response speed than a traditional PI controller compared with a traditional PWM carrier method and a PI control method. The optimal duty ratio is obtained in real time according to the load resistance change, and the system efficiency is higher.
The technical scheme obtains the optimal duty ratio of ideal output power through the minimization of the objective function, is simple and feasible, does not need to adjust gain and measure, greatly reduces the cost, size and complexity of the WPT system, has a simple structure and low cost, improves the efficiency of the system, accords with the theme of pursuing high-efficiency and resource saving in the current market, and has more significance for the practical application value.
The foregoing is only a partial embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A method for controlling a wireless power transfer system, comprising:
establishing a mathematical model of the wireless electric energy transmission system;
and analyzing and calculating according to the system mathematical model to obtain the optimal duty ratio and the optimal working frequency, and predicting the output power of the system.
2. The method of claim 1, wherein the establishing a mathematical model of the wireless power transfer system comprises:
respectively calculating and obtaining the input power, the output power and the system working frequency of the wireless electric energy transmission system;
according to the equivalent impedance ZrBy conversion of angular frequency to obtain ZrAfter the formula is converted, the load resistance R is respectively obtainedLAnd coil mutual inductance M;
obtaining the load resistance R according to the timing diagramLThe coil mutual inductance M and the angle;
and establishing a mathematical expression of the cost function by using the new algorithm model predictive control.
4. The method of claim 2, wherein the equivalent impedance Z isr=Rr+jXrWherein R isrAs an equivalent resistance component, XrIs equivalent reactance component and converts the angular frequency omega into the angular frequency omega of the system working at zero phase02Obtaining the R of the system frequency at the zero phaserAnd XcrAnd obtaining a new ZrMathematical expression, sequentially obtaining load resistance R according to transformation formulaLAnd a coil mutual inductance M.
7. the method of claim 6, wherein the step of establishing the mathematical expression of the cost function by using the new algorithm model predictive control comprises:
determining the relationship between the output power and the duty ratio at any moment, and respectively deriving the relational expressions of the output power, the input direct-current bus voltage, the load equivalent resistance, the mutual inductance coefficient and the duty ratio D;
determining a relational expression between the output power and the duty ratio D at the next moment of any moment;
9. the method according to claim 8, wherein the step of obtaining the optimal duty cycle and the optimal operating frequency according to the system mathematical model analysis and calculation and predicting the output power of the system comprises:
determining the optimal solution of the cost function J, namely the minimum value of the cost function J according to the expression of the cost function, and calculating the obtained load equivalent resistance R according to the known input voltageLAnd obtaining the optimal duty ratio D (K) by the coil mutual inductance M.
10. The method of claim 9, wherein the MOSFET is controlled to turn on and off according to the obtained optimal duty ratio d (k), and the inversion frequency of the system is determined.
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