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Journal ArticleDOI

Modeling and Estimation of DC–DC Buck Converter Dynamics Using Relay Feedback Output With Performance Evaluation

TL;DR: The dynamics of a dc–dc buck converter is modeled using the limit cycle oscillations (LCO) induced by relay feedback test to get an accurate dynamic model of the converter.
Abstract: In this brief, the dynamics of a dc–dc buck converter is modeled using the limit cycle oscillations (LCO) induced by relay feedback test. The mathematical modeling of the converter is done based on sustained oscillatory output conditions and measurements made on LCO. The method is capable of identifying the model in presence of parameter variations. With the precise information of losses of the components available in the LCO, it is possible to get an accurate dynamic model of the converter. The identified dynamic model is validated with the step response. Also, the performance of the model is tested under different parameter perturbations. The proposed method is verified by simulation and experimental results.
Citations
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Journal ArticleDOI
TL;DR: This brief addresses the problem of instability occurring in the voltage control mode of a non-minimum phase (NMP) DC-DC boost converter with quantitative feedback theory (QFT) adapted to systematically design a robust proportional integral derivative (PID) controller.
Abstract: This brief addresses the problem of instability occurring in the voltage control mode of a non-minimum phase (NMP) DC-DC boost converter. To solve this instability issue in the presence of uncertainties and the external disturbances, quantitative feedback theory (QFT) is adapted to systematically design a robust proportional integral derivative (PID) controller, which is realized using only sensed output voltage as feedback. The advantages of the proposed PID design using the QFT are: (i) it eliminates the burden of tedious and ad-hoc tuning of PID gains using the conventional PID design approaches, (ii) current measurement is not required, (iii) disturbance dynamics (input voltage and load current variations) are included in the design stage itself, which further enhances the disturbance rejection performance of the output voltage, and (iv) it allows direct design for the non-minimum phase boost converter despite the bandwidth limitations. Extensive simulations and experiments are carried out to validate the efficacy of the proposed PID controller in the presence of the external disturbances and compared its superiority over a conventional PID controller.

44 citations


Cites background from "Modeling and Estimation of DC–DC Bu..."

  • ...THE GROWING applications of DC-DC boost converters in continuous conduction mode (CCM) have become prevalent in automotive, battery charging applications and so on, whose performance highly depends on the deployed control scheme [1]....

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Journal ArticleDOI
TL;DR: An online relay autotuning scheme for parameter estimation of a class of time delayed systems is presented and a pipe-line water pressure control system is identified as under-damped SOPDT transfer function model.
Abstract: In this brief, an online relay autotuning scheme for parameter estimation of a class of time delayed systems is presented. The identification method comprises a relay and a proportional-derivative (PD) controller which helps in yielding sustained oscillation or limit cycles at the system output around the user defined setpoint. Along with the relay and controller parameters, the important limit cycle information are measured and further substituted in the derived set of mathematical expressions required for the estimation of system unknown dynamic in the form of under-damped second-order plus dead-time (SOPDT) model. Simulations of well known model dynamics from the literature are considered to illustrate the efficacy of the proposed scheme in presence of noise and static load disturbance. For the real-time validation of the proposed scheme, a pipe-line water pressure control system is identified as under-damped SOPDT transfer function model.

16 citations


Cites background from "Modeling and Estimation of DC–DC Bu..."

  • ...Recently, relay based identification of DC–DC converter circuits [14], [15] and modeling of heterogeneous transmission lines [16] in transfer function form have drawn much attention....

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Journal ArticleDOI
TL;DR: This article addresses the infeasibility issue by adding an external control loop on top of the autotuning unit that adjusts the reference crossover frequency until the phase margin specification is fulfilled.
Abstract: Possible dynamic interactions among multiple dc microgrid power converters that are connected to a common dc bus can lead to performance degradation or even stability issues in some control loops Thus, in order to maintain a desired dynamic behavior when operating conditions or system parameters are changing, an interesting approach is to adopt autotuning for the controller parameters In general, existing autotuning methods are based on the evaluation of the stability specifications (eg, the crossover frequency and the phase margin) and the adaptation of the controller to ensure the specified dynamic properties However, the desired bandwidth and phase margin may not be achievable due to parameter changes, unexpected additional delays, or unmodeled dynamics in the feedback loop This article addresses the infeasibility issue by adding an external control loop on top of the autotuning unit This external loop adjusts the reference crossover frequency until the phase margin specification is fulfilled As a result, the proposed scheme is capable of tracking the highest bandwidth at which the reference phase margin is achievable, ie, the maximum allowable bandwidth The proposed method is applied to a dc microgrid prototype, and the simulation and experimental results are discussed

6 citations

Journal ArticleDOI
TL;DR: On-line identification scheme is proposed where the system characteristics is extracted with respect to proportional-integral (PI) controller dynamics in terms of sustained oscillatory responses broadly known as limit cycle at the system output.
Abstract: This brief presents a symmetrical relay-based identification scheme for a class of linear time-invariant systems with time delay. During off-line identification, the adverse effect of static load disturbance may lead to erroneous system model parameters. Therefore, on-line identification scheme is proposed where the system characteristics is extracted with respect to proportional-integral (PI) controller dynamics in terms of sustained oscillatory responses broadly known as limit cycle at the system output. Utilizing the relay settings (amplitude and hysteresis width), controller parameters and limit cycle information, an explicit set of mathematical expressions for on-line parameter estimation of system dynamics in terms of a stable first order plus time delay (FOPTD) model is deduced from frequency domain and state space analyses. As compared to recent relay-based identification methods, the proposed set of explicit expressions does not require any prior guess of initial values of the system model parameters for the simultaneous solution of a nonlinear set of mathematical equations. Simulation of a benchmark example from literature and experimental results from the coupled tanks system are included for validation of the proposed identification algorithms using the deduced set of mathematical expressions.

5 citations


Cites background from "Modeling and Estimation of DC–DC Bu..."

  • ...The authors have derived off-line/on-line frequency domain [12], [14] and off-line state space [13] based mathematical expressions which are sensitive to both load disturbance and measurement noise due to lack of PI control....

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Journal ArticleDOI
TL;DR: In this paper , an external control loop is added to the autotuning unit to adjust the reference crossover frequency until the phase margin specification is fulfilled, which is capable of tracking the highest bandwidth at which the reference phase margin is achievable.
Abstract: Possible dynamic interactions among multiple dc microgrid power converters that are connected to a common dc bus can lead to performance degradation or even stability issues in some control loops. Thus, in order to maintain a desired dynamic behavior when operating conditions or system parameters are changing, an interesting approach is to adopt autotuning for the controller parameters. In general, existing autotuning methods are based on the evaluation of the stability specifications (e.g., the crossover frequency and the phase margin) and the adaptation of the controller to ensure the specified dynamic properties. However, the desired bandwidth and phase margin may not be achievable due to parameter changes, unexpected additional delays, or unmodeled dynamics in the feedback loop. This article addresses the infeasibility issue by adding an external control loop on top of the autotuning unit. This external loop adjusts the reference crossover frequency until the phase margin specification is fulfilled. As a result, the proposed scheme is capable of tracking the highest bandwidth at which the reference phase margin is achievable, i.e., the maximum allowable bandwidth. The proposed method is applied to a dc microgrid prototype, and the simulation and experimental results are discussed.

4 citations

References
More filters
Journal ArticleDOI
TL;DR: This paper presents a modified correlation method for system identification of power converters with digital control by injecting a multiperiod pseudo random binary signal to the control input of a power converter, derived by cross-correlation of the input signal and the sensed output signal.
Abstract: For digitally controlled switching power converters, on-line system identification can be used to assess the system dynamic responses and stability margins. This paper presents a modified correlation method for system identification of power converters with digital control. By injecting a multiperiod pseudo random binary signal (PRBS) to the control input of a power converter, the system frequency response can be derived by cross-correlation of the input signal and the sensed output signal. Compared to the conventional cross-correlation method, averaging the cross-correlation over multiple periods of the injected PRBS can significantly improve the identification results in the presence of PRBS-induced artifacts, switching and quantization noises. An experimental digitally controlled forward converter with an FPGA-based controller is used to demonstrate accurate and effective identification of the converter control-to-output response.

248 citations


Additional excerpts

  • ...Different other methods are proposed by authors to identify the converter model [11], [12]....

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Journal ArticleDOI
TL;DR: The process models with time delay mainly adopted for identification in the literature are presented with a classification on different response types, along with two specific categories for robust identification against load disturbance and the identification of multivariable or nonlinear processes.

183 citations


"Modeling and Estimation of DC–DC Bu..." refers background in this paper

  • ...Many researchers identified different plant models using relay test [6]–[8]....

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Journal ArticleDOI
TL;DR: In this paper, a simple autotuning technique for digitally controlled dc-dc converters is proposed based on the relay feedback method and introduces perturbations on the output voltage during converter soft-start.
Abstract: This paper proposes a simple autotuning technique for digitally controlled dc-dc converters. The proposed approach is based on the relay feedback method and introduces perturbations on the output voltage during converter soft-start. By using an iterative procedure, the tuning of proportional-integral-derivative parameters is obtained directly by including the controller in the relay feedback and by adjusting the controller parameters based on the specified phase margin and control loop bandwidth. A nice property of the proposed solution is that output voltage perturbations are introduced while maintaining the relay feedback control on the output voltage. The proposed algorithm is simple, requires small tuning times, and it is compliant with the cost/complexity constraints of integrated digital integrated circuits. Simulation and experimental results of a synchronous buck converter and of a dc-dc boost converter confirm the effectiveness of the proposed solution

167 citations


"Modeling and Estimation of DC–DC Bu..." refers methods in this paper

  • ...In the earlier studies on DC-DC converters, the relay is used for auto-tuning of controllers [9], [10] but this is not used for the identification of the converter....

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Journal ArticleDOI
01 Sep 1999
TL;DR: In this paper, a set of general expressions derived from a single asymmetrical relay feedback test for online plant identification is derived, and conditions for the existence of limit cycles in unstable FOPDT and SOPDT processes are derived.
Abstract: A set of general expressions is derived from a single asymmetrical relay feedback test for online plant identification. The expressions also remain valid for an odd symmetrical limit cycle test method. Using the expressions, the exact parameters of open-loop stable and unstable first-order plus time delay (FOPDT) and second-order plus time delay (SOPDT) transfer function models may be obtained from simple measurements made on the limit cycle. The approach can also be used to identify transfer functions of integrating processes. Conditions for the existence of limit cycles in unstable FOPDT and SOPDT processes are derived. The design of controllers for these processes is then considered and a simple, but very effective, approach using standard forms with a variable zero is presented. The advantages of using PI-PD control, compared with conventional PID or PI-D control, particularly for unstable and integrating processes is clearly shown. Examples are given to illustrate the value of the proposed general identification method and the improved system performance provided by the proposed controllers.

149 citations


"Modeling and Estimation of DC–DC Bu..." refers background in this paper

  • ...Many researchers identified different plant models using relay test [6]–[8]....

    [...]

Journal ArticleDOI
TL;DR: A dynamic hysteresis control of the buck converter for achieving high slew-rate response to disturbances is proposed and the technique is verified with the experimental results of a 50 W buck converter.
Abstract: A dynamic hysteresis control of the buck converter for achieving high slew-rate response to disturbances is proposed. The hysteresis band is derived from the output capacitor current that predicts the output voltage magnitude after a hypothesized switching action. Four switching criteria are formulated to dictate the state of the main switch. The output voltage can revert to the steady state in two switching actions after a large-signal disturbance. The technique is verified with the experimental results of a 50 W buck converter.

141 citations


"Modeling and Estimation of DC–DC Bu..." refers background in this paper

  • ...Different control methods are proposed in [13] and [14] to get good transient performances....

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