Random and programmed pulse-width modulation techniques for DC-DC converters

In this work, a novel grouped clocking technique is applied to the programmed pulse width modulation(PPWM) clock control circuits, the purpose of this technique is to broaden the spectrum and mitigate electromagnetic interference of the output waveform in continuous conduction mode(CCM) DC-DC converters. Different from the traditional clocking control technique, the number of optimization variables in grouped PPWM is reduced by dividing these parameters into several groups with same periods and duty ratios. Due to less variables, the design of control circuits can be well simplified. For validation, the genetic algorithm is employed in the grouped clocking technique to implement mitigation of EMI in a traditional continuous conduction mode DC-DC converter. The numerical results show that the EMI is well reduced by using the grouped clocking technique in PPWM control.

Power Line Communication (PLC) technologies are being used in many applications and offer the advantage of utilizing existing power cables for both power and data transmission, thus minimizing cost and complexity. Nevertheless, PLC technology requires further investigation to solve possible co-existence issues. Indeed, recent studies confirmed that alternative modulation schemes such as Random Pulse Width Modulation (RPWM), applied to switching-mode power converters to minimize conducted emissions, detrimentally interfere with the PLC system. This paper presents an experimental test campaign aimed at investigating the effects of RPWM on the G3-PLC system, with the final goal of understanding the conditions under which RPWM schemes can be considered as an effective alternative to conventional Pulse Width Modulation (PWM) in applications involving PLC systems. In details, the effects of different RPWM parameters such as switching frequency, modulation index, and Random Number Update Rate (RNUR) on the G3-PLC is investigated. In addition, different RPWM schemes such as Random Frequency Modulation (RFM) and Random Pulse Position Modulation (RPPM) are compared in terms of performance so as to highlight which RPWM is best suited to assure coexistence with PLC systems. The impact of RPWM on the communication channel is evaluated in terms of Frame Error Rate (FER), Channel Capacity, and Channel Capacity Loss metrics. Experimental results confirmed that randomly modulated converters with switching frequencies near the G3-PLC bandwidth cause more significant disturbance and possible coexistence issues than the switching frequencies out of this range. Results also show that the modulation index and the RNUR of RPWM have a direct effect on the communication channel. Moreover, a trade-off between Electromagnetic Interference (EMI) reduction and coexistence issues is observed: RFM, which is very effective for EMI reduction, is found to be very disruptive for G3-PLC, compared to alternative random modulation techniques such as RPPM.

Programmed PWM techniques are some of the control methods used in voltage/current source converters. However, challenges are the task of defining and solving a set of nonlinear transcendental equations in order to obtain the switching angles. The paper presents an efficient Differential Evolution (DE) algorithm that significantly reduces the computational burden resulting in a fast convergence. The design procedure of a Programmed Pulse Width Modulation (PPWM) rectifier using Matlab/Simulink Blockset and code generation tools for Microchip dsPIC Digital Signal Controller (DSC) is also presented. The proposed approach follows the standard practice to utilize Matlab/ Simulink and related toolboxes as the design framework to develop a rapid prototype system in a reliable procedure. The design procedure uses Simulink model of the AC-DC converter system, drive circuitry, Matlab Real-Time Workshop, and Microchip MPLAB IDE development tools. The generated and self-developed codes on dsPIC 30F4013 are tested with the dsPICDEM 2 Development Board. The output rectifier waveform and spectrum results from simulation and experimental DSC PPWM are presented.

Low switching frequency operation is preferred to improve the system efficiency as well as for optimal use of inverter rating in variable speed drive systems. Low switching frequency operation presents stability and performance issues during transition from lower to higher speed operations using asynchronous to synchronous programmed pulse width modulation (PWM) operation of the inverter. The paper presents a sensorless vector control strategy for the permanent magnet synchronous motor (PMSM) drive operating at low switching frequency with programmed PWM methods. Specifically for the reduced switching frequency operation, the analysis, design and implementation of the key control subsystems consisting of the current controller, back EMF observer and position tracking controller in the drive system are developed and presented. Experimental results validate the design methodology, system performance including the efficiency improvement with the proposed control strategy.

This study presents a comprehensive detailed analysis of the effect of five different random modulation switching schemes and their randomness levels on the elector magnetic interference (EMI) of designed simple and interleaved DC-DC buck converters for smartphone applications. The analyzed switching schemes are pulse width modulation (PWM), random pulse width modulation (RPWM), random pulse position modulation (RPPM), random carrier frequency modulation various duty (RCFMVD), and random carrier frequency modulation fixed duty (RCFMFD). The experimental analysis is performed for all aforementioned switching modulation schemes at the switching frequency of 20 kHz and different randomness levels (RL) (30% to 85%). For a fixed RL of 40%, the switching current harmonics/conducted emission (CE) levels are 5–10 dB/11 dBμV and 17 dB/14 dBμV lower for the RCFMVD case when compared to conventional PWM for both simple and interleaved buck-converters, respectively. The observed switching current harmonics and CE levels for interleaved schemes are around 23 dB and 12 dBμV lower when compared to the conventional simple buck converter scheme for the analyzed circuit configurations. The EMI levels decrease with the increase in the randomness levels from 30% to 85% with less variations in the output voltage level. The findings suggest that a interleaved buck converter circuit with the least-independent switching mechanisms and higher randomness is more appropriate for the reduction of both current spikes and CE levels with RCFMFD as the switching modulation scheme.

This paper presents an electromagnetic interference analysis of the random modulation switching schemes based on the switching current harmonics and conducted emission (CE) levels of a buck converter. The analyzed switching schemes are pulse width modulation (PWM), random pulse width modulation (RPWM), random pulse position modulation (RPPM), random carrier frequency modulation various duty (RCFMVD), and random carrier frequency modulation fixed duty (RCFMFD). The conducted experimental analysis suggests that the utilization of the RCFMFD did not only reduces the harmonics and CE levels but also produces the desired output voltage value of the buck converter.

This paper proposes a bi-directional dc-dc z-source converter. Z-source dc-dc converter has an impedance network which performs buck-boost operations. In this the input current is continuous and also the voltage stress across the switches is less. It can also boost the input voltage using reduced passive component with better reliability and decreased cost. Compared to the existing dc-dc converter circuits, they reduce in-rush and harmonic current. Therefore this paper aims at a soft switched quasi z-source converter. That the proposed converter has the better voltage profile with most reduction of voltage regulation. H-bridge dc-dc sources are preferably connected to the voltage sources and sometimes current sources. This is used to minimize the current stress as well as to improve the system efficiency. Z-source isolated bi-directional dc-dc converter boosts the dc voltage up to the 600 V, which is used to supply to the inverter. Inverter is being incorporated with space vector modulation technique for its driver circuit control. From this that the inverted output is supplied to the asynchronous motor drive to get the dynamic responses of the drive from its performance parameters like stator phasor current, torque and speed. Respective results are analyzed by using MATLAB software.

Spectral fusion is a process by which elements of sound are grouped into unified auditory source percepts. The grouping processes use acoustic cues such as the presence of sub‐audio frequency modulation, its coherence among spectral components and the constancy of the spectral envelope. Both periodic (vibrato) and random (jitter) modulation can contribute to fusion. The rms deviation of modulation must be greater than the modulation detection threshold found for these complex tones (16 harmonies of 220 Hz). When the modulation imposed on the ensemble of spectral components is incoherent or does not maintain the harmonic relation (i.e., is not proportional to frequency for all harmonics), less fusion is perceived. There are indications that the detection of coherence of modulation occurs in the higher harmonic numbers. Those modulations which mitigate against fusion also contribute to an increase in spectral resolution. The spectral resolution indicated in these experiments appears to bc greater than that for unmodulated signals classically reported. With more complex spectral envelopes, like vowels, a greater degree of fusion is reported when the spectral envelope is constant, i.e., a concurrent amplitude modulation accompanies frequency modulation and “traces out” the spectral envelope. This may indicate that grouping processes favor fixed‐resonance structures. Musical examples illustrating the use of these principles in computer synthesis will be played.

An improved random SVPWM for zero voltage switching three phase inverter

This paper focuses on designing and implementing a grid-tie inverter, which can convert DC voltage from the PV systems into an AC voltage using pulse width modulation technique. The proposed inverter is synchronized with the local grid to provide an alternate solution for the energy generation. To obtain the maximum power from the inverter maximum power point tracking technology is used. Using MPPT, approximately 95% power efficiency was achieved. Boost converter is designed to boost the voltage from solar panels to 240V. Phase locked loop circuit is utilized to synchronize the output frequency of the inverter with that of the local utility grid. Phase locked loop circuit uses phase detector to detect the phase difference between the reference (utility grid) frequency and the quiescent (required) frequency set in Voltage Controlled Oscillator. This quiescent frequency is converted to match with the reference frequency. This converted or synchronized frequency is then used as a reference for pulse width modulation controller to generate Pulse Width Modulation waveform. Using PLL, phase or frequency matching between utility grid’s electricity and inverter’s electricity was achieved in just 0.6 seconds. In the end, filtering system is designed using LMS filter and KALMAN filter to remove the noise from inverter output. A total of -22.63 dB total harmonic distortion was achieved using Kalman filter and were proved to be better than LMS filter. The simulation results provided in this report show the efficacy of the proposed grid-tie inverter.

This study introduces design, integration, control, and analysis of a hybrid microgrid (MG) testbed including a 300 kW wind energy plant of three 100-kW permanent magnet synchronous generators (PMSGs), 50 kW solar energy plant of 200 solar panels, and a 50 kW fuel cell stack. Generation side of the hybrid plant coupled on 120V dc bus where wind energy plant consists of uncontrolled diode rectifier and dc-dc buck converter rail while the solar and fuel cell plants are just controlled by dc-dc buck converters. The energy conversion of solar energy plant is operated by using proportional-integral (PI) controller assisted perturb and observe (P&O) maximum power point tracking (MPPT) algorithm. The dc-dc converters of the left generators are operated with PI controllers. All the dc-dc converters are constituted with mosfets that are switched at 30 kHz. The islanded AC grid of the plant is built by three-phase inverter that generates 480 V 60 Hz industrial voltages of the U.S. The inverter is operated by a sinusoidal pulse width (SPWM) modulator where the modulation index is set to 0.8 and switching frequency to 5 kHz. The proposed testbed is assumed essential to test and validate several case studies in terms of MG and renewable energy source integration issues. The most recent power control methods (PQ) and amplitude controls (V-f) can also be implemented by using the presented testbed.

This paper presents simulation of DC-DC converter with matrix converter as its basic topology. The proposed converter performs the four quadrant chopper operation. This topology can perform many different converter functions. This DC-DC converter can be utilized in speed control of dc motor in electric automobiles and traction where supply is dc voltage. The simulation model was developed in MATLAB/Simulink environment. Pulse width modulation technique is used for output synthesis of the converter. The analysis of converter was done considering resistive and inductive both loads separately.

In a photovoltaic (PV)- or fuel-cell-based grid-connected power system, a high step-up dc-dc converter is required to boost the low voltage of a PV or fuel cell to a relatively high bus voltage for the downstream dc-ac grid-connected inverter. To integrate the advantages of the high voltage gain of a switched-capacitor (SC) converter and excellent output regulation of a switching-mode dc-dc converter, a method of combining the two types of converters is proposed in this paper. The basic idea is that when the switch is turned on, the inductor is charged, and the capacitors are connected in series to supply the load, and when the switch is turned off, the inductor releases energy to charge multiple capacitors in parallel, whose voltages are controlled by a pulsewidth modulation technique. Thus, a high voltage gain of the dc-dc converter can be obtained with good regulation. Based on this principle, a series of new topologies are derived, and the operating principles and voltage gains of the proposed converters are analyzed. Finally, the design of the proposed converter is given, and the experiment results are provided to verify the theoretical analysis.

This paper presents a novel control method to improve the efficiency of low-voltage DC-DC converters at light loads. Pulse Width Modulation (PWM) converters have poor efficiencies at light loads, while pulse frequency modulation (PFM) control is more efficient for the same cases. Switching losses constitute a major portion of the total power loss at light loads. To decrease the switching losses and to increase efficiency, converters based on soft-switching are utilized. This paper presents the design of a soft-switching DC-DC buck converter in a 90-nm CMOS technology. Simulation results by HSPICE shows a 21 mV output ripple on a 0.5 V output voltage for an input voltage of 1.4 V. Finally, the efficiency of 95% at a load current of 50 mA having 74 mA of current ripple is achievable.

This paper proposes fuzzy based Random Pulse Width Modulation (RPWM) technique to trim down the overriding harmonic clusters in the output current's spectrum. Asynchronous Motor is fed by PWM inverter and current is controlled by Field Oriented Control (FOC) algorithm. When an inverter with constant switching frequency is used, it would result in narrow-band harmonics. These harmonic clusters can make acoustic noises and Electromagnetic Interference (EMI). In order to diminish the noises and EMI consequence of these harmonic clusters, adaptive fuzzy controller based random-switching PWM strategies have been introduced. The concept of RPWM technique is to spread the original narrow-band harmonic throughout a wide range of frequencies. Acoustic noises and EMI are reduced uniformly in output current's spectrum. Proposed switching pattern is compared with conventional switching pattern that is proposed earlier. Simulation results of conventional and proposed method are obtained by using MATLAB/Simulink Software.