Random discrete PWM method for DC-DC power converters

A random discrete pulse-width modulation (RDPWM) scheme is examined and compared with the randomised pulse-position modulation (RPPM) method for DC-DC power conversion. The RDPWM method has no switching harmonics while the RPPM method has significant switching harmonics. Power spectral characteristics of the two methods are presented and discussed     

NEW PERTURBATION TECHNIQUE FOR TRANSIENT ANALYSIS AND ITS APPLICATIONS IN DC-DC PWM SWITCHING POWER CONVERTERS

An improved perturbation technique proposed in a recent paper (Int. J. Electronics, vol. 63, pp.403-414) has been successfully applied to steady-state analysis of PWM switching converters. This paper extends the algorithm to transient analysis of a broader class of non-linear systems. As an example, the transient response of a Boost PWM switching converter is analyzed to demonstrate its simplicity and accuracy.     

PWM zero-voltage switching boost-derived converters with outputisolation

In this paper, the basic operations and steady-state analysis for three modified boost-derived power converter topologies are presented. Unlike the conventional boost topology, these power converters provide electrical isolation and zero-voltage switching, while having identical component stresses as those in the conventional boost power converters. Zero-voltage switching and proper transformer-core resetting are achieved from the resonance that occurs between the parasitic capacitance of the power switch and the transformer magnetizing inductance. By introducing a lossless clamping circuit, the voltage stresses across the switching devices are limited to the reflected output voltage to the primary side     

Dynamics analysis and controller synthesis forzero-voltage-transition PWM power converters

A small signal model for zero-voltage-transition pulse width modulation (ZVT-PWM) buck converters is proposed in this paper. It shows that the ZVT-PWM buck converter exhibits better dynamical behavior than the conventional PWM buck converter. Based on the derived model consisting of line voltage disturbances and load variations, μ-synthesis is applied for a robust controller design to achieve performance requirement. In addition, a classical controller and a sliding mode controller with modified integral variable structure are also designed for performance comparisons. Finally, simulation and experimental results are presented to verify the requirement for robust performance of ZVT-PWM converters     

Capacitor loss analysis method for power electronics converters

A capacitor is a major component that contributes to reducing the reliability of high-power density power electronics converters. The lifetime and reliability of capacitors are strongly influenced by temperature. An accurate loss measurement method is necessary to estimate temperature rise. However, practical capacitor loss measurement systems used in power electronics converters have not yet been developed because capacitor loss data provided by the manufacturer is usually measured under sinusoidal excitation, which is different from actual excitations of electronics converters. In this study, a capacitor loss measurement system for power electronics converters is proposed. The proposed measurement system can be used for fast capacitor loss measurement with high accuracy in a real circuit and capacitor loss analysis for each switching period of power electronics converters. To verify the accuracy of the loss measurement, the measured loss value of a filter capacitor used in a pulse width modulated inverter is compared with the calculated value. The experimental results show good agreement with the calculated capacitor loss.     

A carrier-based PWM method for three-phase four-leg voltage source converters

In this paper a voltage modulation method based on a triangular carrier wave for the three-phase four-leg voltage source converter is described. The four-leg converter can produce three output voltages independently with one additional leg. The proposed modulation method for the four-leg converter can be implemented with a single carrier by a simple but useful "offset voltage" concept. The method is equivalent to the so called three-dimensional space vector PWM method, but its implementation is much easier. The maximum magnitude of the balanced three-phase voltage and the maximum magnitude of zero sequence voltage, which can be synthesized simultaneously, are derived. The feasibility of the proposed modulation technique is verified by computer simulation and experimental results. These results show that a proposed carrier-based pulsewidth modulation (PWM) technique can be easily implemented without conventional computational burden.     

Feedforward pulse width modulators for switching power converters

This paper describes pulse width modulators (PWMs) that employ feedforward compensation to improve the steady-state and dynamic responses of power converters. It is shown how ideal feedforward PWMs (FF-PWMs) can be constructed for all duty-ratio controlled switch-mode power converters operating in the continuous conduction mode. A power converter with FF-PWM behaves at low frequencies as a linear power amplifier with constant gain independent of operating conditions. The proposed FF-PWM can be easily implemented using the same building blocks found in conventional PWM controllers. Experimental and simulation examples are included to illustrate applications of the FF-PWM     

Complex behavior in switching power converters

Power electronics circuits are rich in nonlinear dynamics. Their operation is characterized by cyclic switching of circuit topologies, which gives rise to a variety of nonlinear behavior. This paper provides an overview of the chaotic dynamics and bifurcation scenarios observed in power converter circuits, emphasizing the salient features of the circuit operation and the modeling strategies. In particular this paper surveys the key publications in this field, reviews the main modeling approaches, and discusses the salient bifurcation behaviors of power converters with particular emphasis on the disruption of standard bifurcation patterns by border collisions     

Sampled-data modelling and analysis of the power stage of PWM DC-DC converters

The power stage of the PWM DC–DC converter is modelled and analysed using the sampled-data approach. The work addresses both continuous and discontinuous conduction mode under voltage mode control, and continuous conduction mode under current mode control. For each configuration, nonlinear and linearized sampled-data models, and control-to-output transfer functions are derived. Using this approach, both current mode control and discontinuous conduction mode can be handled systematically in a unified framework, making the modelling for these cases simpler than with the use of averaging. The results of this paper are similar to results of Tymerski, but they are presented in a simpler manner tailored to facilitate immediate application to specific circuits. It is shown how sampling the output at certain instants improves the obtained phase response. Frequency responses obtained from the sampled-data model are more accurate than those obtained from various averaged models. In addition, a new (‘lifted’) continuous-time switching frequency-dependent model of the power stage is derived from the sampled-data model. Detailed examples illustrate the modelling tools presented here and also provide a means for comparing results obtained from the sampled-data approach with those obtained from averaging.     

A novel current-control method for three-phase PWM AC/DCvoltage-source converters

This paper presents a novel current-control-based control strategy, obtained in stationary frame, for a three-phase pulsewidth-modulated AC/DC voltage-source converter. In this control strategy, an error voltage is produced from the comparison of the output DC voltage with a DC reference voltage. This error voltage is then utilized by a proportional plus integral controller to generate a command signal for the input line current amplitude and is automatically controlled to the desired value. Therefore, there is no need to measure the input line currents. Stability analysis of the closed-loop system is made, and the stability region for proportional and integral gains which makes the operating point stable is also found. The resulting closed-loop system not only exhibits good transient response, but also provides sinusoidal line currents and unity power factor, both in the rectifying and regenerating modes. Experimental results are presented and compared with simulations     

Zero-voltage-zero-current switching in high-output-voltagefull-bridge PWM converters using the interwinding capacitance

A novel zero-voltage and zero-current-switching (ZVZCS) full-bridge (FB) pulsewidth-modulated (PWM) power converter is proposed. The new converter uses the interwinding capacitance and a small primary-side inductor to achieve a zero-current-zero-voltage turn off and a zero-current turn on of the passive-to-active leg transistors. The turn off of the active-to-passive leg transistors is with zero voltage, and the turn on is with zero voltage and zero current across them. The ringing caused by the parasitic interwinding capacitance and by the reverse recovery of the rectifiers is reduced. The new converter is attractive for high-output-voltage applications (600-1000 V), where the interwinding capacitance is sufficiently dominant. In addition, switches such as insulated gate bipolar transistors (IGBTs) and MCTs can be used at higher frequencies which is particularly desirable for high-power application (above 2 kW). The experimental results obtained from an IGBT-based 62.5-kHz DC/DC power converter with a rated output voltage of 600 V and a nominal power of 1.2 kW are presented     

Advanced regular-sampled PWM control techniques for drives andstatic power converters

Regular-sampled PWM techniques have been developed to reproduce the harmonic-elimination and harmonic minimization PWM power convertor characteristics. These new regular-sampled PWM control strategies significantly reduce the computational requirements for real-time microprocessor-based PWM implementation. This results in simplified and more efficient microprocessor software/hardware requirements, leading to real-time PWM generation with minimized harmonics, suitable for drives and uninterruptible power supplies     

A unified analysis of PWM converters in discontinuous modes

Three discontinuous operating modes of PWM (pulsewidth modulated) converters are considered: the discontinuous inductor current mode (DICM), the discontinuous capacitor voltage mode (DCVM), and a previously unidentified mode called the discontinuous quasi-resonant mode (DQRM). DC and small-signal AC analyses are applicable to all basic PWM converter topologies. Any particular topology is taken into account via its DC conversion ratio in the continuous conduction mode. The small-signal model is of the same order as the state-space averaged model for the continuous mode, and it offers improved predictions of the low-frequency dynamics of PWM converters in the discontinuous modes. It is shown that converters in discontinuous modes exhibit lossless damping similar to the effect of the current-mode programming     

A new control philosophy for power electronic converters asfictitious power compensators

A new philosophy utilizing both thyristor-controlled reactive sources (TCR) and dynamic power filters (DPF) is proposed for applications in fictitious power compensation. The necessary network parameters for the control loops are calculated from digital time-domain, cross correlation signal processing techniques implemented with the aid of a microcomputer. Practical results that illustrate this control philosophy were obtained for a 15 kVA three-phase dynamic power filter     

Current-mode analogue integrated circuit for sliding-mode controlof switching power converters

An analogue integrated circuit designed to implement sliding-mode control laws for high frequency switching DC-DC power converters is presented. The circuit operates in current-mode, providing high speed, modularity and the capability of including compensating dynamics. Experimental results for a 0.8 μm complementary metal-oxide-semiconductor (CMOS) technology prototype validate the high-speed functionality of the proposed sliding-mode controller implementation     

Graphical phasor analysis of three-phase PWM converters

A graphical steady-state analysis technique based on the complex 0-sequence, forward-rotating, and backward-rotating (0fb) phasors is described for balanced three-phase PWM inverters, rectifiers and cycloconverters. The technique avoids the cumbersome algebra of the 0fb transformation, and the coupling between the subcircuits resulting from the real direct-axis/quadrature-axis (dq) transformation. Using symmetric and de-coupled subcircuits that are time-invariant under steady state, the graphical method makes the analysis of three-phase converters straightforward and insightful. In the paper, time-invariant transient models with respect to an arbitrary reference node are first derived for all three-phase converter components. Application of the component models to steady-state analysis is demonstrated for the buck-boost inverter. The steady-state equivalent circuits for the popular buck and boost inverters, rectifiers, and cycloconverters are given along with the steady-state values for their capacitor voltages and inductor currents     

A PWM method for reduction of switching loss in a full-bridgeinverter

This paper presents the “hybrid pulsewidth modulation” (HPWM) method which requires only two of the four switches in a full-bridge inverter to be pulsewidth-modulated at high frequency, thus significantly reducing the switching losses in the other two switches. For triangular carriers, HPWM has the same frequency spectrum and switching losses as the conventional unipolar PWM (UPWM). A low-frequency model for a fast-switching HPWM full-bridge inverter with high-quality output is described, and is substantiated by experimental data     

Novel real-time harmonic minimized PWM control for drives andstatic power converters

This paper shows how a novel harmonic minimized PWM control strategy, based on regular-sampling PWM techniques, can be used to significantly reduce the computational requirements for real-time microprocessor-based PWM implementation. This results in greatly simplified and more efficient microprocessor software/hardware requirements, leading to real-time PWM generation with minimized harmonics, suitable for all power-electronic PWM control applications     

A new multilevel PWM method: a theoretical analysis

Generalization of the pulsewidth modulation (PWM) subharmonic method to control single-phase or three-phase multilevel voltage source inverters (VSI) is considered. An analytical expression of the spectral components of the output waveforms covering all the operating conditions is derived. The analysis is based on an extension of Bennet's method. The improvements in harmonic spectrum are pointed out, and several examples are presented, which prove the validity of the multilevel modulation     

A high performance amplitude/phase modulated digital-to-synchro switching power converters

In this paper, a high performance three-phase switching digital-to-synchro (D/S) power converter is proposed for driving high power synchro motors. An amplitude/phase modulation algorithm is implemented with digitally controlled sinusoidal pulse-width-modulation. Design methodology and synchronization improvement are also presented. The generated synchro format output is first verified by simulation and then by a digital signal processor controlled hardware prototype testing. Experimental results indicate that the switching amplifier based D/S converter not only shrinks the size over the conventional linear amplifier based unit, but also demonstrates superior performance to the commercially available unit.