A heuristic approach to robust control design for boost power converters with harmonic reduction

The application of quantitative feedback theory (QFT) to design robust controller for a DC-DC boost converter operating in continuous conduction mode (CCM) is investigated in this paper. The controller is designed to provide good attenuation of the load disturbances in spite of practical limitations on the achievable closed-loop performance (i.e. right-half-plane zero) and in the presence of other design constraints including closed-loop tracking and robust stability. A prefilter is subsequently designed in order to improve the transient and steady state control responses. Tracking control characteristics are analyzed through computer simulation for a peak-current-mode (PCM) controlled boost converter in order to demonstrate the effectiveness of the proposed control methodology.

Due to the ever-expanding use of light emitting diodes (LED) lamps and the necessity of constant current to operate properly, a drive circuit is required for these types of lamps. Also, power factor correction (PFC) to eliminate harmonics, is required and must be included in these types of drivers based on the existing standards. Soft switching can effectively reduce the switching losses and electromagnetic noise. Consequently, high switching frequency operation is possible which reduces the converter weight and size, effectively and high power density is achieved. In this paper, continuous conduction mode (CCM) operation of a single-stage boost-flyback converter with active-clamp for LED driver applications is introduced. Its CCM operation leads to low input current ripple which reduces the input filter volume effectively. Also, low voltage and current stresses on the components are obtained. As a result, the converter can be used for high power applications compared with previously proposed discontinuous conduction mode (DCM) operation. Theory, simulation as well as practical results are presented below.

This paper presents a control method for three-phase inverter under grid fault condition based on a novel critical conduction mode (CRM)-based soft-switching modulation. In the soft-switching modulation, one phase is clamped to dc bus, other two phases operate in CRM and discontinuous conduction mode (DCM), respectively. The soft-switching technique with silicon carbide (SiC) power devices allows the inverter to operate at hundreds of kHz with high efficiency by reducing switching loss. In order to extend the modulation scheme to more practical cases, behavior of the inverter under grid fault conditions, specifically voltage sag, is investigated. During voltage sag, the grid voltage becomes unbalanced requiring unbalanced ac current reference for the avoidance of output active power oscillation. With the unbalanced grid voltage and ac current reference, continuous conduction mode (CCM) operation occurs where DCM operation is intended leading to high turn-on loss. To eliminate the CCM operation and reduce the turn-on loss, an improved modulation technique is proposed by using off-time extension concept in CRM phase. In this paper, how the CCM operation appears under grid fault condition, and details of the proposed control are discussed. Performance of the proposed control method is validated experimentally with SiC-based three -phase inverter laboratory prototype.

This paper discusses experimental validation of semi-bridgeless boost rectifier (SBBR) operation of continuous conduction mode (CCM) & discontinuous conduction mode (DCM) for power quality improvement in uninterrupted power supply (UPS) system. The double stage conversion in UPS attenuates power quality at the input side and output configuration of the system. Many researchers have proposed the improvement of power quality with CCM and DCM operations for ac-dc conversion stage in bridge and bridgeless rectifier, but there is lack of knowledge about their performance and drawbacks of CCM and DCM operation with SBBR topology. This paper focuses on experimental analysis of SBBR topology operating in CCM and DCM under different load ranges. The performance of power quality factors and efficiency of SBBR operating in CCM and DCM are addressed. To study the stability analysis of SBBR operation in CCM and DCM, a comprehensive small signal model is derived by analyzing the inductor current waveforms. PSCAD simulations have obtained theoretical study of SBBR with CCM and DCM operations and experimental validation is carried out through FPGA Spartan 3A processor.

This paper introduces an LED drive circuit implemented by series input connected converter cells with a common duty cycle control approach operating from a dc voltage bus. With this structure, low voltage high frequency ICs and low profile components can be applied in high voltage applications. Flexibility is provided for the cells to work under different voltage supply conditions by simply changing the number of series converters. With the converters operating in continuous conduction mode (CCM), the common duty cycle control approach enables automatic line voltage sharing and output current copying. The approach results in a control-to-output transfer function of the system that is close to that of a single converter for ease of feedback loop design. The modular approach also allows continued operation in the presence of open circuit LED failures. Design considerations and experimental results are presented for a 25 W 3-cell system with 9 Luxeon K2 high brightness LEDs, demonstrating line voltage sharing, output current copying and LED failure response.

In this paper, a high gain modular multilevel dc-dc converter topology is proposed. As compared with the conventional modular multilevel step-up converters, the proposed converter offers an additional degree of control-freedom and higher steady-state voltage gain. The proposed converter operates in continuous conduction mode. A detailed small-signal modeling for the proposed converter based on state-space average modeling is presented. In addition, this study covers both the small-signal and steady-state analysis for the high gain modular multilevel dc-dc converter operating in continuous conduction mode. The performance of the proposed converter is compared with conventional modular multilevel dc-dc converter. To confirm this design, simulations have been carried out on a 1 kW, 48 V to 288 V converter system. Finally, the validity of the converter is verified by simulation results.

The flyback converter is widely used in modern power conversion systems due to its simple topology, single switch, low component count, and inherent galvanic isolation. This paper investigates the performance characteristics of flyback converters by analyzing their operation in Continuous Conduction Mode (CCM) and Discontinuous Conduction Mode (DCM), with particular emphasis on voltage spike behavior. The main contribution of this study is the development of a mathematical model that correlates the operating mode (CCM or DCM) with the voltage spike across the power switch. In addition, the study examines the impact of duty cycle variations on voltage spike behavior. The results show that, for comparable operating conditions and moderate duty cycles, CCM operation generally results in lower voltage spikes than DCM due to reduced peak magnetizing current, while at higher duty cycles and load levels, CCM may exhibit increased voltage stress. The proposed approach was validated through MATLAB/Simulink simulations and a scaled-down experimental prototype. A proportional integral (PI) controller is implemented in simulation to ensure regulated output voltage under practical operating conditions. The results demonstrate that optimizing the duty cycle and accounting for the influence of conduction mode can enhance the reliability of flyback converters, making them suitable for applications requiring galvanic isolation and cost-effective solutions.

Introduction. This paper describes the simulation and the robustness assessment of a DC-DC power converter designed to interface a dual-battery conversion system. The adopted converter is a Buck unidirectional and non-isolated converter, composed of three cells interconnected in parallel and operating in continuous conduction mode. Purpose. In order to address the growing challenges of high switching frequencies, a more stable, efficient, and fixed-frequency-operating power system is desired. Originality. Conventional sliding mode controller suffers from high-frequency oscillation caused by practical limitations of system components and switching frequency variation. So, we have explored a soft-switching technology to deal with interface problems and switching losses, and we developed a procedure to choose the high-pass filter parameters in a sliding mode-controlled multicell converter. Methods. We suggest that the sliding mode is controlled by hysteresis bands as the excesses of the band. This delay in state exchanges gives a signal to control the switching frequency of the converter, which, in turn, produces a controlled trajectory. We are seeking an adaptive current control solution to address this issue and adapt a variable-bandwidth of the hysteresis modulation to mitigate nonlinearity in conventional sliding mode control, which struggles to set the switching frequency. Chatter problems are therefore avoided. A boundary layer-based control scheme allows multicell converters to operate with a fixed-switching-frequency. Practical value. Simulation studies in the MATLAB / Simulink environment are performed to analyze system performance and assess its robustness and stability. Thus, our converter is more efficient and able to cope with parametric variation.

This paper presents a dynamic voltage scaling (DVS) compatible single-inductor multiple-output (SIMO) voltage regulation module that enables smaller passives for a given output power, while maintaining power quality (low output ripple), suppressing cross regulation, and improving efficiency at high switching frequency. First, continuous-conduction mode (CCM) operation is utilized to deliver higher output power for a smaller inductance; the cross-regulation in CCM operation is suppressed using a novel power-weighted CCM controller. Second, a modified power stage filter is presented using floating capacitors that utilize the Miller effect to reduce the switching frequency of the output, while maintaining the power quality. The operating principles, stability, and circuit level design of the proposed SIMO VR are presented. The design is demonstrated through a 130-nm CMOS test chip that generates four outputs, each ranging from 200 to 600 mV, from a 1.2-V input. The measurements demonstrate a 20-MHz operation, the pulse width modulation signal of the power stage with 500-nH inductor, and 1-μF total load capacitance, while delivering a output power density of 150 mW/μH·μF. The test chip demonstrates DVS speed of 120 mV/μs, 73% peak efficiency at a load of 40 mA, and as high as 40% efficiency improvement using the modified power filer.

Dynamic response of boost power factor correction (PFC) converter operating in continuous-conduction mode (CCM) is heavily influenced by low-bandwidth of voltage control loop. A novel tri-state boost PFC converter operating in pseudo-continuous-conduction mode (PCCM) is proposed in this paper. An additional degree of control-freedom introduced by a freewheeling switching control interval helps to achieve PFC control. A simple and fast voltage control loop can be used to maintain a constant output voltage. Furthermore, compared with boost PFC converter operating in conventional discontinuous-conduction mode (DCM), boost PFC converter operating in PCCM demonstrates greatly improved current handling capability with reduced current and voltage ripples. Analytical and simulation results of the tri-state boost PFC converter have been presented and compared with those of the boost PFC converter operating in conventional CCM and DCM. Simulation results show excellent dynamic performance of the tri-state boost PFC converter.

This paper presents the analysis of an isolated three-phase rectifier with high power factor using a Zeta converter operating in continuous conduction mode. The structure is particularly simple and robust. Its main features are one power processing stage (which can operate as step-down or step-up voltage), lower harmonic distortion of the input current, and natural isolation. The converter works with constant frequency and pulsewidth modulation. The principle of operation, design procedure, and experimental results are presented.

For most actual power applications, power-factor correction (PFC) converters usually operate in the stable continuous conduction mode (CCM), but input current distortion will occur as long as these converters operate in oscillatory condition. This distortion usually manifests itself as a local oscillation within one line cycle. Typically, a Zeta PFC converter under the general pulse-width modulated (GPWM) control possesses high performance, and requires simpler control circuitry with fewer external components. However, due to the large-signal nonlinearity of the GPWM controller, the dynamic analysis and modeling of the input current distortion in its PFC converters remains vacant. In this paper, a large-signal average SPICE model is derived to capture the time-domain waveforms of the input current and output voltage. A power-balance approach for the PFC converter operating in CCM is developed, which can predict the steady-state values of the converters by using the Fourier series expansion. Analysis of the distortion behavior is provided in terms of the proposed model and the unbalanced power transfer mode. Experimental results are presented to verify the proposed method.

Robust velocity and height control problem is dealt with for hypersonic vehicles subject to highly nonlinearity and uncertainties. The linear robust controller design for nonlinear systems suffers from the conservation problem, because the nonlinear dynamics are considered as uncertainties. In this paper, a feedback linearization controller is firstly applied to achieve the dynamic decoupling of the velocity and height channels. Then, robust controllers are designed for each channel to restrain the effects of the parametric uncertainties, external disturbances, and nonlinear dynamics, which cannot be counteracted accurately by the feedback linearization technique. This method can guarantee the robust stability and robust tracking properties of the closed-loop control system, while the conservation of the robust controller design can be reduced because the nonlinear information of dynamic system is used. Simulation comparisons are given to show the advantages of the proposed robust nonlinear control method.

This paper deals with design of a robust control for two level Boost DC-DC converter (TLBC) operating in continuous conduction mode (CCM). The switched model describing the converter operation is presented and the design procedure of sliding mode control taked as of robust law is described. For validation, Matlab/Simulink software has been used. The robustness of the controller is tested for input voltage variations and load changes. The simulation results show that the efficiency and robustness of this controller are better than those of the cascade PI controller.

The growing demand on the renewable energy systems that work through battery cells has provided a high interest in the DC/DC Buck-Boost converters due to their capability to both amplify and attenuate the voltage that is supplied from such cells. An important feature in the design of these converters is the ability to operate in continuous conduction mode (CCM) so as to lower harmonic distortion and avoid the need for active control on inductors. In this paper, we investigate the design requirements for CCM operation in a reported single switch quadratic DC/DC converter by constructing a simulation model to validate the theoretical gain equations of the converter and check their agreement with the reported results. The simulation results obtained not only revealed inaccuracies in the reported gain equations but also confirmed the agreement between the proposed gain equations in this paper with the expected behavior of the converter.