Frequency response analysis for bidirectional series‐resonant DC/DC converter in discontinuous mode

The state-space modeling and related order reduction problems of switching DC-DC converters operating in discontinuous (D) mode are treated in this paper. A unified discrete-time full-order model is proposed assuming the discontinuous current and voltage mode (DCVM) as a general operation mode from which the discontinuous current mode (DCM), the discontinuous voltage mode (DVM), and continuous made (CM) derive as special cases. Such a model permits a straightforward study of the control-to-output response, in each operation mode. The order reduction of the transfer function is carried out by means of the principal component analysis considering the joint controllability and observability properties of the circuit. It is shown that a proper order reduction can be gained not only in DC mode, as expected, but also in DV and DCV modes. A substantial difference between DC and DV modes is also evidenced in terms of controllability. The frequency analysis and state-space model order reduction for a Cuk converter are proposed to show that the method is free of the limitations affecting other methods of analysis and that its predictions fit experimental measurements.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Sampled data techniques are used to examine the small signal characteristics of the series–parallel resonant converter in both the continuous and discontinuous parallel capacitor voltage modes of operation. The fourth-order characteristics of the converter are found to reduce to third order as the converter enters the discontinuous operating mode. The design and performance of an output voltage regulation loop is investigated for two converter designs: A, operating solely in the continuous mode, and B, operating in the discontinuous mode at full load. The latter is found to provide superior performance over a wide operating range.

Small-signal modeling of switched-mode converters has been developed in early 70s, when the state-space averaging (SSA) method was introduced for assessing the dynamics of direct-duty-ratio controlled converters in continuous conduction mode (CCM). It turned out that the direct circuit theoretical approach could not be applied to get accurate models also for discontinuous operation mode (DCM). We present in this paper a unified and consistent method for the modeling of switched-mode converters under direct-on-time control applicable to fixed-frequency and variable-frequency operation in DCM and CCM. The method is based on the direct estimation of the state-variable derivatives using their physical and circuit-theoretical dependence on the corresponding circuit elements.

This paper deals with the analysis and design of a high frequency isolated AC-DC flyback converter in discontinuous current mode (DCM) of operation used for power quality improvement at AC mains in vector controlled permanent magnet synchronous motor (PMSM) drive. The design of the flyback converter is carried out to feed a vector controlled PMSM drive system. Modeling and simulation are performed in a standard PSIM software environment. The obtained results demonstrate the effectiveness in improving the power quality at AC mains in the PMSM drive system.

High power reliability and high energy density are always in demand, and this is driving the evolution of power conversion technologies. People have begun to examine the potential positions of dc systems in both current and future power equipment due to the rise in the use of renewable energy and the implementation of energy storage in recent decades. Because of its efficiency and power density, dc voltage representation has found use in a wide range of fields, including data centres, the aerospace industry, and dc micro-grids. Resonant DC-DC converters, with their gentle switching and minimal EMI, provide a promising solution to these problems. Finding and examining the various modes of operation of the converter while employing the pulse-removal approach is the primary objective of this study. The new method of operation utilises variable frequency and variable phase displacement in sub-resonant mode, which promises to reduce the transformer size while also facilitating the soft-switching change of the insulated gate bipolar transistors (IGBTs) and line frequency diodes on the rectifier side. The pulse elimination approach, a revolutionary mode of operation for the converter, involves phase and frequency shift modulation at varying rates. Using the results of MATLAB/SIMULINK simulations, the suggested control technique may be utilised to establish the baseline switching function configuration necessary to attain high power efficiency.

A LC filter can be added to the input of the conventional buck converter to make the converter operate in discontinuous capacitor voltage mode. In this mode, the converter obtains the inherent power factor correction. Besides, both the input and output current will be continuous. This makes it possible for the converter operating at a high power level range. The input current will follow the input voltage automatically by a simple constant duty cycle control. This paper presents a detailed operation analysis of the converter operating in discontinuous capacitor voltage mode. And a 36V/100W prototype was built to verify the theoretical results.

A method to obtain the exact control-to-output and input-to-output transfer functions for switched DC-to-DC pulse-width modulated power converters is applied to different combinations of operating conditions such as continuous conduction mode (CCM), discontinuous conduction mode (DCM), and discontinuous voltage mode (DVM) and methods of control such as normal voltage mode (NVM), current programming mode (CPM), and V-squared control. The majority of these combinations have not previously had their transfer functions of interest derived to the accuracy provided by the method. The derivation of the method is covered, and the results from its application are verified by simulation. The simulation method is also justied and proposed as an improvement to the methods used by simulation engines for switched mode power supply design such as SIMPLIS.

Switching power converters with synchronous rectification utilize transitioning between inductor's current continuous and discontinuous conduction operation modes (CCM and DCM) in order to achieve improved power efficiency across wide load and input voltage ranges. The inductor current zero crossing is sensed in order to detect the operation modes transition point between CCM and DCM. The challenges associated with this include inductor current zero crossing point sensing accuracy, noise effect near the zero crossing point, and the sensing circuitry speed and power loss. Moreover, additional hardware such as analog-to-digital converter is required if the controller used is a fully digital controller. In this letter, a control scheme for sensorless operation and detection of CCM and DCM in a switching power converter is presented. The presented controller utilizes dual control loops and does not require sensing the inductor current or any current in the converter, which eliminates or reduces challenges associated with inductor current sensing for the zero point detection. The presented controller is discussed, and proof-of-concept experimental prototype results are presented.

A method and apparatus for providing a differential microphone with a desired frequency response are disclosed. The desired frequency response is provided by operation of a filter, having an adjustable frequency response, coupled to the microphone. The frequency response of the filter is set by operation of a controller, also coupled to the microphone, based on signals received from the microphone. The desired frequency response may be determined based upon the orientation angle and the distance between the microphone and a source of sound. The frequency response of the filter may comprise the substantial inverse of the frequency response of the microphone to provide a flat response. In a preferred embodiment, the gain of the differential microphone is adjusted so that the output level is effectively independent of microphone position relative to the source. In particular embodiments, the controller may determine, based on the distance from the sound source, whether to operate the differential microphone in a nearfield mode of operation or a farfield mode of operation.

In general, high-voltage DC power supplies employing a variety of high-frequency inverters are implemented for constant value control schemes. In particular, their good transient and steady-state performances cannot be achieved under wide load variations involved in a medical-use X ray tube drive high voltage generator ranging from 20 kV to 150 kV in the output voltage and from 0.5 mA to 1250 mA, respectively. A high-voltage power supply designed for X ray power generator applications is considered, which uses series resonant inverter-linked multistage DC voltage multiplier instead of a conventional high voltage diode module rectifier connected to the second-side of a high-voltage transformer, a constant on-time/variable frequency control scheme of this converter operating at zero-current switching modes is described. Introducing the capacitor-diode based multistage voltage multiplier, the secondary turn numbers and stray capacitance of the high-voltage high-frequency transformer as well as the rectifier diode voltage ratings can be greatly reduced. It is proven that the proposed converter control scheme of the 2 step frequency selected switching is more effective for improving output voltage responses. A series resonant high-frequency transformer-linked voltage-multiplying rectifier is evaluated for any ray high-voltage generator on the basis of simulation analysis and observed data in experiment.

This paper proposes an autonomous control scheme to mitigate voltage-frequency excursions observed in a network of grid forming (GFM) and grid following (GFL) inverters in a power electronics dominated grid (PEDG). The proposed control scheme leverages GFL inverter's ability to dynamically adjust their power set-points as well as change their operation mode on-the-fly to enhance the PEDG resiliency. A supervisory controller (SC) comprising of a Droop-ΔP estimator coupled with an optimal power allocator (OPA) module dynamically adjusts the power injections from GFL inverters to maintain the power balance and restore frequency in response to disturbances. Moreover, the proposed self-ranking based coordinated mode selection (SR-CMS) algorithm dynamically reconfigures the inverter's operation mode (either GFM or GFL) to enhance the PEDG resiliency in response to events and ensure GFM inverter allocation in grid clusters. Several case studies are performed to validate the feasibility, performance, and robustness of proposed autonomous control. Finally, the proposed scheme is experimentally validated on a small-scale hardware testbed.

In this paper, a stacked half bridge converter with automatic current balance and soft-switching is proposed. Here, an LED driver is taken as an example to analyze. Based on the ampere-second balance principle, the proposed LED driver can realize automatic current balance. The proposed converter adopts a small inductor to form a resonant tank, which achieves zero current switching (ZCS) in the discontinuous operation mode (DCM) and zero voltage switching (ZVS) in the continuous operation mode (CCM). By using frequency doubling technology, switching losses are reduced by half under the same hardware conditions. A 15.8W experimental prototype with 100V input voltage and 25V output voltage is established in the laboratory, verifying the feasibility of the stacked half bridge converter.

The amount of solid and liquid organic waste and wastewater is continuously increasing all over the world. The necessity of their reuse and recycling is, therefore, becoming more and more pressing. Furthermore, the limited fossil fuel resources, in conjunction with the need to reduce greenhouse gas emissions, advocate the production of renewable fuels. In this work, we analyze a sustainable second-generation process to produce biodiesel by transesterification of waste cooking oil, coupled with a third-generation process in cascade for recycling the incoming wastewater. Since this latter is rich in glycerol, it is used as a feed for microalgae, from which oil can be extracted and added to the waste cooking oil to further produce biodiesel and close the cycle. We studied the influence of different factors like temperature, catalyst load, and reactants ratio on the kinetics of transesterification of the waste oil and estimated the kinetic parameters by different kinetic schemes. The obtained values of activation energies and pre-exponential factors at chosen conditions of T = 60 °C and catalyst load of 0.6% w/w in methanol are: Ea,direct = 35,661 J mol−1, Ea,reverse = 72,989 J mol−1, k0,direct = 9.7708 [dm3 mol−1]3 min−1, and k0,reverse = 24,810 [dm3 mol−1]3 min−1 for the global fourth-order reversible reaction scheme and Ea = 67,348 J mol−1 and k0 = 2.157 × 109 min−1 for the simplified pseudo-first-order irreversible reaction scheme; both in strong agreement with literature data. Furthermore, we designed very efficient conditions for discontinuous and continuous operating mode, both at lab-scale and pilot-scale. The quality of the biodiesel produced from waste cooking sunflower oil is compared with that of biodiesel produced by different kinds of virgin vegetable oils, showing that the former possesses acceptable quality standards (Cetane number = 48 and LHV = 36,600 kJ kg−1). Finally, the recycling of wastewater rich in glycerol as a nutrient for mixotrophic microalgae nurturing is discussed, and microalgae growing kinetics are evaluated (k1 about 0.5 day−1), endorsing the possibility of algae extraction each 4–5 days in a semi-continuous operating mode. The experimental results at the pilot scale finally confirm the quality of biodiesel, and the obtained yields for a two-stage process prove the competitiveness of this sustainable process on the global market.

In this article, a fully soft switched interleaved bidirectional buck/boost converter with high voltage conversion ratio (VCR) and no pulsating current at low voltage source is proposed. Winding cross-coupled inductors technique is employed in order to increase VCR and mitigate current ripple at low voltage side. Moreover, soft switching conditions for all semiconductor devices are provided and the leakage inductances energy of coupled inductors are absorbed in both high step-up/down operating modes. Furthermore, the reverse recovery problem of all diodes is removed due to zero current switching turn <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> . All the mentioned advantages are achieved for a bidirectional converter with two interleaved phases in both high step-up/down operating modes by only one clamp circuit consisting of a clamp capacitor and two active switches. Also, the body diodes of the main switches are utilized as the main diodes to reduce the element count. The converter performance is validated by theoretical analysis and an 800 W prototype circuit in both operating modes.

This paper proposes a new two-switch flyback converter that allows its switches to operate with less peak voltage stress than other flyback converters and with double their power transfer frequency. Moreover, the converter can operate with zero-voltage switching (ZVS) using just one auxiliary switch. In the paper, the operation of the proposed converter is explained. The converter's modes of operation are discussed in detail and analyzed so that the converter's steady-state characteristics can be determined. Based on these characteristics, a procedure for the design of the converter is established and the procedure is demonstrated with a detailed design example. Experimental results obtained from a prototype converter that confirm the feasibility of the converter are presented.