CN106936313A - The sliding-mode control of Sofe Switch condition is realized based on SP type ICPT systems - Google Patents

Abstract

The present invention proposes a sliding mode control method based on the SP-type ICPT system to realize soft switching conditions, including the following steps: S1, the secondary side circuit of the resonance type inductive power transmission system is equivalent to the primary side circuit, according to the equivalent principle The side circuit solves the primary side resonant current; S2, the induced electromotive force is equivalent to a voltage source controlled by the primary side, and the secondary side rectifier circuit is equivalent to a turn ratio of Transformer; S3, the DC equivalent circuit of the resonant induction power transmission system is obtained, according to the differential equation of the DC equivalent circuit, the present invention controls from the primary side, and improves the efficiency of the circuit operation. The proposed second-order sliding mode control algorithm only needs the sampled value of the output voltage and the zero-crossing point of the resonant current, without the specific value of the current and any integral term.

Description

Sliding mode control method based on SP type ICPT system to realize soft switching conditions

technical field

The invention relates to the field of automation control, in particular to a sliding mode control method for realizing soft switching conditions based on an inductively coupled power transmission (ICPT) system.

Background technique

In the prior art, the traditional inductive power transfer system control algorithm does not have a second-order sliding mode control algorithm based on the primary side, and does not establish a second-order DC equivalent model for the primary-side series-secondary side parallel-connected inductive power transfer system. For the control The efficiency problem of the controller with the secondary side switch to adjust the output terminal voltage cannot be solved, and the controller is sensitive to load disturbance, and is greatly affected by the circuit parameters, so it cannot respond quickly and dynamically, and the controller design of the prior art requires current The sampling value and integral term of . The output voltage of the inductive power transfer system of the traditional controller needs a relatively long adjustment time to reach a steady state under the condition of load disturbance and coupling coefficient change. This just needs those skilled in the art to solve corresponding technical problem badly.

Contents of the invention

The invention aims at at least solving the technical problems existing in the prior art, and particularly innovatively proposes a sliding mode control method based on an SP-type ICPT system to realize soft switching conditions.

In order to achieve the above-mentioned purpose of the present invention, the present invention provides a kind of sliding mode control method that realizes soft switching condition based on ICPT system, comprises the steps:

S1, the secondary side circuit of the resonant inductive power transfer system is equivalent to the primary side circuit, and the primary side resonant current is calculated according to the equivalent primary side circuit;

S2, the induced electromotive force of the secondary side is equivalent to a voltage source controlled by the current of the primary side, and at the same time, the rectification circuit of the secondary side is equivalent to a turn ratio after Fourier transform the transformer;

S3, obtain the DC equivalent circuit of the resonant inductive power transfer system, set the reference voltage v _ref according to the differential equation of the DC equivalent circuit, and define the difference between the output voltage V and the reference voltage v _ref as a sliding mode variable The error signal value s;

S4. Set the dynamic parameter value β. When the initial state of s is negative, the switching condition of the state is s≥βs _m ; when the initial state of s is positive, the switching condition of the state is s≤βs _M. The controller structure is composed of two An energy injection state, two energy self-resonance states and an initial state;

S5, detecting the zero-crossing point of the resonant current on the primary side to ensure that the circuit works in a soft switching state;

S6, according to the real-time update of dynamic parameter values, the phase trajectory switches between the energy injection stage trajectory and the energy self-resonance stage trajectory, and finally reaches the sliding mode surface

In the sliding mode control method based on the ICPT system to realize soft switching conditions, preferably, the S1 includes:

Among them, ω ₀ - the natural frequency of the circuit, ω - the operating frequency of the resonant circuit, τ - the time constant of the resonant circuit, Q - the quality factor of the circuit, V _p is the primary voltage, and t is the time constant.

In the sliding mode control method based on the ICPT system to realize soft switching conditions, preferably, the S3 includes:

The circuit parameter expression after DC equivalent is: DC voltage is DC inductance: L _equ ＝L _s , DC capacitance: C _equ ＝C _s , DC resistance:

in

Get the difference equation expression for the equivalent circuit

In the sliding mode control method based on the ICPT system to realize soft switching conditions, preferably, the S3 also includes:

Based on the differential equation expression, define s= _vo -v _ref , v _ref is the set reference voltage, and the first-order and second-order derivation equations of S are expressed as

It can be seen from the above formula that the relative order of the simplified circuit sliding dynamics is 2;

Consider using a second-order sliding mode controller, so the sliding mode surface is chosen as The following expression can be obtained by simplifying the first-order and second-order derivative equations of S

For the convenience of analysis, the circuit is placed in an open state, and the ICPT system is in an undamped state, which is equivalent to is zero;

Multiply the left and right sides of the equation by and points

set variable Will replace, get

energy injection stage,

energy self-resonance stage,

r _e , r _f are the radii of the phase trajectory diagrams in the energy injection stage and the energy self-resonance stage respectively, and their values are determined by the initial state of the circuit. Assuming the initial value is s ₀ , the switching of the circuit mode occurs at β _N s _m , β _N is a constant between 0 and 1, which determines the approaching process of the system, s _m is the minimum value of the energy injection stage, and the initial point is the (s ₀ , 0) phase trajectory diagram.

In the sliding mode control method based on the ICPT system to realize soft switching conditions, preferably, the S4 includes:

Find the β _N and β _P in the limit case, that is, after one switch, the phase trajectory reaches the sliding mode surface

In the actual circuit, in order to prevent the overshoot of the output voltage

Similarly, if the initial point is in the right half plane, find

Likewise, to prevent output voltage overshoot

The sliding mode control method based on the ICPT system to realize soft switching conditions, preferably, the S5 includes:

Detect the zero-crossing point of the resonant current on the primary side, and then correct the phase error caused by the sampling circuit through the phase correction circuit to ensure that each switching action is completed at the moment when the current zero-crossing point; under this condition, realize the second-order sliding mode control algorithm.

In summary, owing to adopting above-mentioned technical scheme, the beneficial effect of the present invention is:

The control scheme is controlled from the primary side, and the control method is realized on the basis of ensuring the realization of soft switching, which improves the working efficiency of the circuit.

The proposed second-order sliding mode control algorithm only needs the sampled value of the output voltage and the zero-crossing point of the resonant current, without the specific value of the current and any integral term.

The control algorithm has strong robustness to the uncertainty of circuit parameters and load disturbance.

This control algorithm is also applicable to ICPT (Inductively Coupled Power Transfer) circuits of other topologies.

Additional aspects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and comprehensible from the description of the embodiments in conjunction with the following drawings, wherein:

Fig. 1 is the circuit topology of the inductive power transmission system of the present invention in which the primary side is connected in series and the secondary side is connected in parallel;

Fig. 2 is the circuit after the secondary side is equivalent to the primary side in the present invention;

Fig. 3 is that the present invention equates the induced electromotive force into a preliminary secondary side equivalent circuit diagram;

Fig. 4 is the direct current equivalent circuit topology of the inductive power transmission system of the present invention in which the primary side is connected in series and the secondary side is connected in parallel;

Fig. 5 is a partial schematic diagram of energy injection and self-resonant phase trajectory clusters of the present invention;

Fig. 6 is the initial point (s ₀ , 0) phase locus diagram of the present invention;

The state machine diagram of the controller of Fig. 7 second-order sliding mode;

Fig. 8 is a schematic diagram of the second-order sliding mode approach process of the control method of the present invention.

detailed description

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

In describing the present invention, it should be understood that the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", The orientation or positional relationship indicated by "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than Nothing indicating or implying that a referenced device or element must have a particular orientation, be constructed, and operate in a particular orientation should therefore not be construed as limiting the invention.

In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be mechanical connection or electrical connection, or two The internal communication of each element may be directly connected or indirectly connected through an intermediary. Those skilled in the art can understand the specific meanings of the above terms according to specific situations.

The invention proposes a second-order sliding mode control method for realizing soft switching conditions for the inductive electric energy transmission system. By replacing the primary side with a DC source and simplifying the rectification circuit of the secondary side, a second-order DC equivalent model for the primary-side series-series inductive power transfer system is established. And a second-order sliding mode controller is designed to adjust the output voltage by controlling the primary side switch, which is realized by a digital state machine. The parameters of the controller are derived from a simplified DC model. The controller has fast dynamic response performance and robustness to load disturbance and parameter uncertainty, and at the same time, the sampling value and integral term of the current are not needed in the design of the controller. The output voltage of the system can reach a steady state with few switching actions under the condition of load disturbance and coupling coefficient change. Figure 1 shows the circuit topology of the inductive power transfer system in which the primary side is connected in series and the secondary side is connected in parallel. Note: V _g - input voltage, C _p - primary side resonant capacitance, L _p - primary side resonant inductance, R _p - primary side resonant inductance, capacitance equivalent resistance, C _s - secondary side resonant capacitance, L _s - secondary Side resonant inductance, R _s - secondary side resonant inductance, capacitor equivalent resistance, L _out - filter inductance, C _out - filter capacitor, R _e - equivalent resistance of components in the dotted line, M is the difference between primary side inductance and secondary side inductance mutual inductance between. On the left side of M is the primary side of the resonant inductive power transfer system, and on the right side of M is the secondary side of the resonant inductive power transfer system,

Among them, the resonant inductive power transfer system contains a considerable number of nonlinear switches, and there are many energy storage elements. The actual system presents complex high-order switch nonlinear behavior, so the sliding mode control strategy has strong applicability to the system. control method. Compared with the traditional control scheme, the main advantage of sliding mode control lies in the robustness of the parameters, and it is insensitive to the disturbance of the parameters of the linear or nonlinear system and the change of the load. Dynamic and Steady State Response.

Circuit equivalent process: Equivalent the secondary side circuit to the primary side to obtain the circuit topology shown in Figure 2, and the circuit after the secondary side is equivalent to the primary side. Where _Re is the equivalent resistance.

Through this circuit, the expression of the primary side resonant current can be solved:

Note: ω ₀ - the natural frequency of the circuit, ω - the operating frequency of the resonant circuit, τ - the time constant of the resonant circuit, Q - the quality factor of the resonant circuit. V _p is the primary voltage, and t is the time constant.

Therefore, the secondary side circuit is equivalent to that shown in Figure 3, where V _oc (t)=wMi _p (t) is the induced electromotive force of the secondary side, and the induced electromotive force is equivalent to a voltage source controlled by the primary side current. A preliminary equivalent circuit diagram of the secondary side is formed. At the same time, after Fourier transform, the rectifier circuit can be equivalent to a turn ratio of the transformer. After equivalent, the secondary side circuit after rectification equivalent can be obtained as shown in Figure 4 .

nv _oc equivalent induced electromotive force, I _s /n equivalent secondary current, Ls, C _s equivalent inductance and capacitance, C _out filter capacitor, L _out filter inductance, R _load load resistance.

Further, we get the DC equivalent diagram of the circuit, as shown in Figure 5, the DC equivalent topology diagram of the inductive power transfer system with the primary side connected in series and the secondary side connected in parallel.

Fig. 6 is a partial schematic diagram of energy injection and self-resonant phase trajectory clusters of the present invention;

The circuit parameter expression after DC equivalent is: DC voltage is DC inductance: L _s , DC capacitance: C _s , DC resistance:

in

According to Figure 5, the difference equation expression of the equivalent circuit is obtained

Based on the differential equation expression, define s= _vo −v _ref , where v _ref is a set reference voltage. The first-order second-order derivative equation of S is expressed as

It can be seen from the above formula that the relative order of the simplified circuit sliding dynamics is 2.

Consider using a second-order sliding mode controller, so the sliding mode surface is chosen as

set variable Will Substituting, we get

energy injection stage, energy self-resonance stage,

r _e , r _f are the radii of the phase locus diagrams in the energy injection stage and the energy self-resonance stage respectively, and their values are determined by the initial state of the circuit. Assuming that the initial value is s ₀ , the switching of the circuit mode occurs at β _N s _m (β _N is a constant between 0 and 1, which determines the approach process of the system), that is, as shown in Figure 7, s _m is The minimum value for the energy injection phase. s _M is the maximum value in the energy injection stage. The initial point is the (s ₀ , 0) phase locus diagram. Substitutions made to simplify the equation.

According to the above analysis, the state machine diagram of the controller based on the second-order sliding mode is shown in Fig. 8, which describes the working principle of the controller.

It can be seen from the figure that the controller needs to determine the parameters β _N and δ, and δ can be determined according to the limit operating frequency of the switching devices in the circuit. Therefore, the value of β _N needs to be obtained. It can be seen from Figure 7 that the best effect of switching is that after the energy injection stage is switched to the energy self-resonance stage, the phase trajectory just reaches the origin along the self-resonance trajectory. can be obtained at this time

In the actual circuit, in order to prevent the overshoot of the output voltage

Similarly, if the initial point is in the right half plane, we can find

Likewise, to prevent output voltage overshoot

(β _N and β _P are a constant between 0 and 1, which determine the approach process of the system, and δ is a hysteresis constant to prevent the switching frequency from being too high.)

As shown in the second-order sliding mode approach process of the control algorithm, β _N can determine the number of switching between energy switching and self-resonance when the output value reaches the reference value. Among them, Limit Trajectories is the limit trajectory, Energy injection is the energy injection process, Free oscillation is the free resonance process, and Actual Trajectory is the actual trajectory.

Fig. 1 is the circuit topology of the inductive power transmission system of the present invention in which the primary side is connected in series and the secondary side is connected in parallel;

Fig. 2 is the circuit after the secondary side is equivalent to the primary side in the present invention;

Fig. 3 is that the present invention equates the induced electromotive force into a preliminary secondary side equivalent circuit diagram;

Fig. 4 is the direct current equivalent circuit topology of the inductive power transmission system of the present invention in which the primary side is connected in series and the secondary side is connected in parallel;

Fig. 5 is a partial schematic diagram of energy injection and self-resonant phase trajectory clusters of the present invention;

Fig. 6 is the initial point (s ₀ , 0) phase locus diagram of the present invention;

The state machine diagram of the controller of Fig. 7 second-order sliding mode;

Fig. 8 is a schematic diagram of the second-order sliding mode approach process of the control method of the present invention.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structures, materials or features are included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications, substitutions and modifications can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the invention is defined by the claims and their equivalents.

Claims (6)

1. a kind of sliding-mode control that Sofe Switch condition is realized based on SP type ICPT systems, it is characterised in that including following step Suddenly：

S1, the secondary circuit of mode of resonance inductive electric energy transmission system is equivalent to primary circuit, asked according to equivalent primary circuit Solution primary side resonance current；

S2, the voltage source by primary current control is equivalent to by the induced electromotive force of secondary, while by Fourier transformation by pair Side rectification circuit is equivalent to a turn ratioTransformer；

S3, obtains the pc equivalent circuit of the mode of resonance inductive electric energy transmission system, according to the difference side of the pc equivalent circuit Journey, setting reference voltage v_ref, by output voltage V and reference voltage v_refDifference be defined as the error signal value s of sliding variable；

S4, when setting the original state of dynamic parameter value β, s to bear, the switching condition of state is s >=β s_m；The original state of s is Timing, the switching condition of state is s≤β s_M, controller architecture is by two energy injection states and two energy self-resonance shapes State and an original state composition；

S5, detects the zero crossing of primary side resonance current, it is ensured that circuit is operated in Sofe Switch state；

S6, according to the real-time update of dynamic parameter value, phase path is in the track in energy injection stage and energy self-resonance stage Track mutually switches, and eventually arrives at sliding-mode surface

2. the sliding-mode control that Sofe Switch condition is realized based on SP type ICPT systems according to claim 1, its feature It is that the S1 includes：

Wherein, ω₀The natural frequency of-circuit, the working frequency of ω-resonance circuit, the time constant of τ-resonance circuit, Q- circuits Quality factor,V_pIt is original edge voltage, t is time constant.

3. the sliding-mode control that Sofe Switch condition is realized based on SP type ICPT systems according to claim 1, its feature It is that the S3 includes：

Circuit parameter expression formula after direct current is equivalent is：DC voltage isDC inductance：L_equ=L_s, direct current Electric capacity：C_equ=C_s, D.C. resistance：

Wherein

Obtain the difference equation expression formula of equivalent circuit

${\stackrel{\·}{v}}_o=-\frac{8v_o}{{\mathrm{\π}}^2{C}_s{R}_{load}}+\frac{i_s}{2{\mathrm{nC}}_s}$

${\stackrel{\·}{i}}_s=\frac{(V_{equ}-v_o)}{L_s}.$

4. the sliding-mode control that Sofe Switch condition is realized based on SP type ICPT systems according to claim 3, its feature It is that the S3 also includes：

Based on difference equation expression formula, s=v is defined_o-v_ref, v_refIt is the reference voltage for setting, the single order second order derivation equation table of S It is shown as

$\stackrel{\·}{s}=-\frac{8v_o}{{\mathrm{\π}}^2{C}_s{R}_{load}}+\frac{i_s}{2{\mathrm{nC}}_s}$

$\stackrel{\·\·}{s}=\[\frac{64}{{\left({\mathrm{\π}}^2{C}_s{R}_{load}\right)}^2}-\frac{1}{L_s{C}_s}\]v_{out}-\frac{8i_s}{{\mathrm{\π}}^2{C}_s{R}_{load}}+\frac{V_{equ}}{L_s{C}_s}$

From above formula, it is 2 that the circuit after simplifying slides dynamic Relative order；

Consider to use Second Order Sliding Mode Control device, therefore, choosing sliding-mode surface isBy the single order second order derivation equation of S Letter can obtain expressions below

$\stackrel{\·\·}{s}+\frac{8}{{\mathrm{\π}}^2{C}_s{R}_{load}}\stackrel{\·}{s}+\frac{1}{L_s{C}_s}s=\frac{V_{equ}-V_{ref}}{L_s{C}_s}$

For simplicity is analyzed, circuit is placed in open-circuit condition, ICPT systems are in undamped state, equivalent toIt is zero；

$\stackrel{\·\·}{s}+\frac{1}{L_s{C}_s}s=\frac{V_{equ}-V_{ref}}{L_s{C}_s}$

Equation the right and left is multiplied byAnd integrate

Variable is setWillReplace, obtain

The energy injection stage,

The energy self-resonance stage,

r_e, r_fThe respectively phase path radius of graph in energy injection stage and energy self-resonance stage, their value is by circuit Original state is determined, it is assumed that initial value is s₀, the switching generation of the pattern of circuit is in β_Ns_m, β_NIt is a constant between 0 to 1, The approach procedure of decision systems, s_mIt is the minimum value in energy injection stage, initial point is (s₀, 0) and phase path figure.

5. the sliding-mode control that Sofe Switch condition is realized based on SP type ICPT systems according to claim 1, its feature It is that the S4 includes：

Obtain the β under limiting case_NAnd β_P, i.e., by once switching, phase path reaches sliding-mode surface

${\mathrm{\β}}_{N\min }=1-\frac{s_m+2V_{ref}}{2V_{equ}}=1-\frac{V_{ref}}{\frac{\mathrm{\π}}{\sqrt{2}}\frac{(Q+1)M}{L_p}{V}_P}$

In side circuit, in order to prevent the overshoot of output voltage

${\mathrm{\β}}_N\≥1-\frac{V_{ref}}{\frac{\mathrm{\π}}{\sqrt{2}}\frac{(Q+1)M}{L_p}{V}_P}$

Similarly, if initial point is in RHP, can obtain

${\mathrm{\β}}_{P\min }=\frac{1}{2}\left(\frac{S_M+2V_{ref}}{\frac{\mathrm{\π}}{2\sqrt{2}}\frac{(Q+1)M}{L_p}{V}_P}\right),$

Equally, to prevent output voltage overshoot

s_mIt is the minimum value in energy injection stage, s_MIt is the energy injection stage Maximum.

6. the sliding-mode control that Sofe Switch condition is realized based on SP type ICPT systems according to claim 1, its feature It is that the S5 includes：

The zero crossing of primary side resonance current is detected, then correcting the phase brought due to sample circuit by phase-correcting circuit is missed Difference, it is ensured that each switch motion was completed at the current zero-crossing point moment；Under the conditions of this is ensured, then realize that Second Order Sliding Mode Control is calculated Method.