Ali Jaafar

Experimental validation with a control point of view analysis of the SEPIC converter

This paper presents a theoretical study with experimental validation carried out on a DC-DC SEPIC converter operating in continuous conduction mode (CCM). Two dynamic modeling techniques are adopted and various aspects of the converters operating modes are analyzed. Simulations of transient and frequency responses are verified with experimental results. A PI control law is used to validate responses to load and reference voltage variations with parasitic losses taken into account. An in-depth analysis of the effects of unstable zeros of the transfer function, from the duty cycle to the output voltage, on the implementation of control laws is also presented. The frequency behavior of the converter along with the stability margins are found to be widely influenced by load resistance and duty cycle variations.

Nonlinear sliding mode observer and control of high order DC-DC converters

In this paper, the application of the Sliding Mode Theory, in terms of observer and control design, to the DC-DC Single-Ended Primary Inductor Converter (SEPIC) is investigated. The choice and influence of the sliding surface regarding the state vector is presented. Usual sliding surfaces chosen to control other high order DC-DC converters are found not to work on the SEPIC. Thus, other surfaces are proposed here and which require the presence of more than one state variable. Also, an extended sliding mode observer is proposed to estimate the state vector. Results are experimentally validated.

PI Stabilization of Power Converters With Partial State Measurements

In a recent paper a procedure to design globally asymptotically stabilizing linear proportional plus integral controllers for switched power converters was proposed. The construction requires the measurement of the full state of the system, which is often unavailable in practice. In this note we identify a class of converters for which an asymptotically convergent reduced order observer, preserving the aforementioned stability property of the closed-loop, can be designed. The class is characterized by a simple linear matrix inequality. The new controller is illustrated with the widely-popular, and difficult to control, single-ended primary inductor converter, for which simulation and experimental results are presented.

FPGA based sliding mode control for high frequency SEPIC

This paper presents the application of fixed frequency (or indirect) Sliding Mode Control (SMC) to the DC-DC Single-Ended Primary Inductor Converter (SEPIC) where the switching frequency is in the range of hundreds of kHz and consequently a FPGA is required. Due to the constraint of FPGA, only the output voltage is measured. As the proposed SMC requires the knowledge of all the states, an extended Kalman observer is introduced to estimate the state vector and the load variation. A multi-bit second-order Δ-Σ modulator is used to effectively achieve 11-bit resolution at high-frequency through only a 8-bit hardware Core Digital Pulse - Width - Modulator (DPWM). Simulation and experimental studies are conducted for a laboratory prototype with switching frequency of 500 kHz. Results proved the performance of the proposed solution.

FPGA based predictive deadbeat control for high switching frequency SEPIC

This paper presents the application of predictive deadbeat control to the high switching frequency DC/DC Single-Ended Primary Inductor Converter (SEPIC). An extended Kalman observer with load variation estimation is designed to achieve current sensorless operation of the controller. A hybrid Delta-Sigma (Δ-Σ) Digital Pulse Width Modulation (DPWM) is used to effectively achieve 11-bit resolution at high-frequency and reduce the system clock frequency. The proposed DPWM along with the predictive deadbeat control algorithm is validated by using a Virtex-II FPGA. Experimental studies are conducted for a laboratory prototype with switching frequency of 500kHz. Simulation and experimental results prove the performance of the proposed solution.

Observer-based PI stabilization of power converters

In a recent paper a procedure to design globally asymptotically stable linear proportional plus integral controllers for switched power converters was proposed. The construction requires the measurement of the full state of the system, which is often unavailable in practice. In this note we identify a class of converters for which an asymptotically convergent reduced order observer, preserving the aforementioned stability property of the closed-loop, can be designed. The class is characterized by a simple linear matrix inequality. The new controller is illustrated with the widely-popular, and difficult to control, single-ended primary inductor converter, for which experimental results are presented.