System of control of nonlinear dynamics of direct step-down voltage converter

FIELD: electricity.

SUBSTANCE: invention relates to the field of electrical equipment and can be used in digital control systems of DC voltage converters with the function of suppression of the hazardous oscillations of output voltage occurring at a certain set of parameters of the system. In the nonlinear dynamics control system the control system consisting of the main subsystem and the control auxiliary subsystem, approximators on the basis of neural networks is connected to the power part of the converter. The converter control signal provides the stabilization of average value of output voltage. In the system the correction of error signal is provided, thus the stabilization of the design dynamic mode (1 cycle) is provided.

EFFECT: ensuring of pre-set nonlinear dynamic properties of the system and pre-set parameters of speed and accuracy of output voltage stabilization in case of refusal from parametrical synthesis.

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The claimed invention relates to Converter equipment and can be used to implement digital control systems, DC-to-DC function the suppression of dangerous fluctuations in output voltage that occurs when a particular set of system parameters.

The known method International Journal of Circuit Theory and Applications, [1], called method with delayed feedback, where for the stabilization of unstable periodic trajectories assumes the use of a feedback delay that is approximately equal to the period of the stabilized periodic mode.

Stabilization of the project is due to the fact that the control signal after the controller standard control system is added two corrective signal: scaled difference between the current in the stroboscopic times and current at stroboscopic times, detained for the period of pulse width modulation; the scaled difference between the voltage on the capacitor in the strobe time and the voltage on the capacitor at stroboscopic times, detained for the period of pulse width modulation, which allows to adjust the vector of the driving influences from the point of view of the system of differential equations describing the system,and provide periodic project mode.

Disadvantages of the method include the difficulty of choosing a time delay and parameters of the control system, resulting in no guarantee the correct operation of the device in a wide range of changes in its parameters.

The object of the invention is to control the nonlinear dynamics of the system to ensure its operation in the project periodic mode with small amplitude oscillations in a wide range of control system parameters or the input voltage with the possibility of work in the areas of multistability.

This problem is solved due to the fact that the power part of the Converter, made on the basis of direct down Converter, the LC filter connected control system consisting of two subsystems: the main subsystem, consisting of a subtractor forming a difference of the reference signal and the feedback signal (error signal), the scaling amplifier feedback voltage, a proportional controller, the input of which is fed with the error signal, and the output signal is input to the comparator, the second input of which receives the signal from the generator deploys voltage, synchronous with the reference generator, which allows to generate a control signal transmitter, to ensure stabilization of the average value of the output is tense�I; auxiliary control subsystem, characterized in that the method does not use the time delay in the stabilization of the project, and introduced the perceptron-based neural networks, using the current value of the setpoint voltage of the input voltage and the load impedance form a vector specifying the (current of the inductor and capacitor voltage) at a fixed point display 1-cycle, subtract vector from which feedback state variables at stroboscopic times, output devices sample-and-hold with the use of the scaling amplifier is implemented using visitarla, next, the result of the subtraction is amplified scaling amplifiers and fed to the subtractor of the main control subsystem to adjust the error signal, thereby providing stabilization project dynamic regime (1 cycle).

Functional diagram of the control system (CS) immediate step-down DC-DC Converter shown in Fig.1.

In SU is allocated two subsystems:

- the main control subsystem (SDAS) provides stabilization of the average value of the output voltage without considering the nonlinear dynamic properties;

auxiliary subsystem management (SPM) provides stabilises�Yoo design dynamic regime (1 cycle).

Standard automatic feedback-control the average value of the output voltage pulse Converter is described by the function strobe display [2]

Xk=eAaXk-1+(eAa-eA(1-zk)a)A-1B,

where the vector of state variables X=[iLUc,]T, iL- current inductor; Uc- the voltage on the capacitor; zk- the fill factor of the PWM on the k-clock interval; Xk-1the vector of system state variables at the beginning of the k-th clock interval. The matrix of system parameters and A vector of the driving influences B are presented in [2]. The matrix a depends on the inductance L, capacitance C, the parasitic resistance of the inductor R and the load resistance RH. The vector B depends on the input voltage of the Converter E0and the inductance of the inductor L.

In the standard control system for the institution feedback voltage scaling is used the amplifier to�fficient β. The subtractor B calculates an error voltage UOshthat is fed into a proportional controller with a coefficient α. As a job on the average value of the output voltage signal is used UW. The control signal after the controller Uyis fed to the noninverting input of the comparator. The inverting input of the comparator is fed razvertyvaemye voltage Upfrom generator deploys voltage UAH. Output pulses of the comparator Uandcontrol power transistor VT is the immediate step-down Converter.

In the present case, the standard SU introduced two additional governors impact ΔUOSCand ΔUOSC(Fig.1), which are defined by the expression

ΔUOSC=K1(URMS-Uck)

ΔUOSC=K2(ULk-ILk),

where URMSULkthe reference signals for the voltage on the capacitor and the current of the inductor, respectively, in the stroboscopic time points (fixed point display); Uck- scaled capacitor voltage at stroboscopic times; ILk- scaled current throttle at stroboscopic times.

The expression for the function stroboscopic display SU is

Xk =eAaXk-1+(eAa-eA(1-(zk+Δzk))a)A-1B,

where Δzk- increment the fill factor on the k-clock interval.

The specified increment is calculated on the basis of the expression

Δzk=α(ΔUoW1k+ΔUoW2k)Upm,

where Upm- the amplitude deploys the voltage at the output UAH.

When implementing the algorithm to control the most important task is the calculation of the fixed point of the stroboscopic display, which is using the method of equations of frames [2]. However, when using this method, the microcontroller SU has to implement one of the numerical methods for solving systems of nonlinear transcendental equations that Tr�Buet serious enough computing resources. To simplify this task, we used two neural networks (HC1 and HC2), each of which calculates its vector component of the fixed point 1-display cycle X*=[URMS, iLk]T.

As input variables of neural networks (factors regression) are the parameters in the system can vary within wide limits. The factors used in the regression models are specifying the voltage UW, input voltage (E0and the load resistance Rnwhich is calculated using the sensor signals of the load current and sensor output voltage. This approach can significantly reduce the time of calculation of fixed points, and achieved the accuracy of the approximation is acceptable from the practical point of view. In the considered control system neural network implemented a regression model of the form X*=F(P)=[f1(U3E0, Rn), f2(UWE0, Rn)], where f1and f2- nonlinear three-parameter functions - components of the vector function F implemented HC1 and HC2, respectively, P=[UWE0, Rn]Tis a vector of factors regression. The calculation of the current load unit is the transmitter load resistance VSN.

Feedback p� state variables at stroboscopic times in the proposed system (Fig.1) is carried out using devices sample-and-hold (UVH and OVH in Fig.1). As can be seen from Fig.1, memory voltage on the output capacitor C and current of the inductor L, scaled with coefficients β1and β2accordingly, at the beginning of each clock interval when applying for WMDs Gating pulse from the master oscillator MO, which operates synchronously with the generator deploys voltage UAH. With the help of two visitarla (B1 and B2 in Fig.1) calculate the deviation of the current position of the point of the mappings from the specified subsequent scaling coefficients (K1and K2the corresponding components of the vector of misalignment ΔX=[ΔUckThat ΔiLk]T. The calculated increment ΔUOSCand ΔUOSCcombined with the error voltage SDA UOshby calling on each clock interval of the stabilizing design mode increment the fill factor Δzk. When setting in system design 1-cycle ΔUOSC=ΔUOSC=0, and Δzk=0.

The proposed structure of the control system is implemented fairly large range of modern digital signal microcontrollers or low-cost programmable logic integrated circuits. If you use the latter significantly simplifies the calculation of the assignment for fixed point 1-cycle with the use of neural networks.

To analyze the proposed �], performed computer modeling, the results of which are shown in Fig.2, 3 in the form of maps of dynamic regimes, showing the characteristics of a partition of the space of system parameters on stability of different modes. The simulation was carried out with the following system parameters: L=0.1 GN, C=1 µf, R=10 Ω; Rn=100 Ω; α=60; β=0,01; UW=5 B; Upm=10 B; a=0,0001 c; K1=-0,9; K2=-0,9; β1Of =0.01; β2=0,1.

When you build maps of dynamic regimes (Fig.2, 3) is chosen sufficiently large, the gain of the controller of α=60, which allowed to assess the possibilities of the method when the system is in rather difficult conditions. As can be seen from Fig.2, area 1-cycle of the system without control of nonlinear dynamics is neodnovidnoe and its area is relatively small.

Fig.3 shows a chart of dynamical regimes, the analysis of which shows that the region of a 1-cycle (P1) is significantly increased in comparison with the region 1-cycle in Fig.2. In particular, when the input voltage is E0<1500 B over the entire range of voltage variation of the task in the system has a stable 1-cycle. At E0>500 B and at UW>8 B on the map area appear chaotic oscillations, the area is relatively small. The use of this method of management has significantly improved nonlinear dynamic properties of the system�we in this case, the proportional gain of the controller remains unchanged, allowing it to maintain a given static error UOsh.

Simulation demonstrates the effectiveness of a method for control of nonlinear dynamics direct step-down voltage Converter. The use of this method of control will allow to refuse parametric synthesis, while ensuring the given nonlinear dynamical properties of the system and ensure specified performance and accuracy of output voltage stabilization.

Literature

1. Batlle C. Stabilization of periodic orbits of the buck converter by time-delayed feedback / C. Batlle, E. Fossas, G. Olivar // International Journal of Circuit Theory and Applications. - 1999. - Vol.27, No. 3. - P. 617-631.

2. Kobzev, A. B., " Nonlinear dynamics of semiconductor converters / B. A. Kobzev, G. Y. Mikhalchenko, A. I. Andriyanov, S. G. Mikhalchenko - Tomsk: Tomsk state University of control systems and Radioelectronics, 2007. - 224 p.

Management system, implemented due to the fact that the power part of the Converter, made on the basis of direct down Converter, ZC-filter connected control system consisting of two subsystems: the main subsystem, consisting of a subtractor forming a difference of the reference signal and the feedback signal (error signal), the scaling amplifier return with�yahzee voltage, proportional regulator, the input of which is fed with the error signal, and the output signal is input to the comparator, the second input of which receives the signal from the generator deploys voltage, synchronous with the reference generator, which allows to generate a control signal transmitter, to ensure stabilization of the average value of the output voltage; an auxiliary control subsystem, characterized in that the perceptron-based neural networks, using the current values for the setpoint voltage, the input voltage and the load resistance (the calculator calculates resistance load), form a vector specifying the (current of the inductor and the voltage across the capacitor) on the fixed point display 1-cycle, subtract vector from which feedback state variables at stroboscopic times, output devices sample-and-hold with the use of the scaling amplifier is implemented using visitarla, then the result of the subtraction is amplified scaling amplifiers and fed to the subtractor of the main control subsystem to adjust the error signal, thereby providing stabilization project dynamic regime (1 cycle).



 

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