Zero-crossing Distortion Research Articles

Fast-scale non-linear distortion analysis of peak-current-controlled buck–boost inverters

ABSTRACTThis paper deals with fast-scale non-linear distortion behaviours including asymmetrical period-doubling bifurcation and zero-crossing distortion in peak-current-controlled buck–boost inverters. The underlying mechanisms of the fast-scale non-linear distortion behaviours in inverters are revealed. The folded bifurcation diagram is presented to analyse the asymmetrical phenomenon of fast-scale period-doubling bifurcation. In view of the effect of phase shift and current ripple, the analytical expressions for one pair of critical phase angles are derived by using the design-oriented geometrical current approach. It is shown that the phase shift between inductor current and capacitor voltage should be responsible for the zero-crossing distortion phenomenon. These results obtained here are useful to optimise the circuit design and improve the circuit performance.

Realization of current-mode fully integrated full-wave rectifier

In this paper, a new fully integrated high frequency current-mode full-wave rectifiers are presented. The proposed circuits rectify the input signals without diode, so the output signal confronts zero-crossing distortions because of the diode characteristics have been solved with this rectifier even in high frequencies. While the current rectifier has dual output, the voltage rectifier has one output. The presented circuits have a vastly superior zero crossing performance, good linearity, minimum number of transistors, wide frequency range, and they are suitable for monolithic integrated implementation. The performances of the proposed circuits are investigated through LTSpice. Monte-Carlo and Noise analyses have also been performed to show the effectiveness of the proposed circuits.

PFC Converter with Improved Input Current Zero-crossing Distortion

In this study, a voltage superposition concept is used without phase adjustment of the input current command and without enlarging the turn-on period of the switch in the vicinity of the zero input voltage, but only with a few components added to the PFC converter, so as to improve the zero-crossing distortion of the input current, thereby further reducing the total harmonic distortion. Eventually, the mathematical deductions and experimental results are provided to verify the effectiveness of the proposed circuit.

Topologies and Control Strategies of Cascaded Bridgeless Multilevel Rectifiers

This paper presents a new unidirectional cascaded bridgeless multilevel rectifier (CBR) well suited for serving as the rectifier stage of a transformerless cascaded multilevel converter. Compared to a traditional cascaded H-bridge rectifier, the proposed CBR utilizes fewer fully controlled switching devices by replacing the fully controlled H-bridge modules with bridgeless PFC modules, thus simplifying the control circuits, increasing the system reliability, and cutting down the implementation expenses. However, when a single-phase CBR is operating under a unity power factor, the input current will be severely distorted because of the unidirectional power flow property of the bridgeless PFC modules. Therefore, aiming at achieving a satisfactory current quality and power factor simultaneously, an improved control strategy and a revised topology for the single-phase CBR are provided as two effective solutions. Specifically, for the single-phase CBR under the improved control, the limitation of the maximum value of the boost inductance considering an acceptable power factor is derived. Besides, the method of determining the configuration of the modified single-phase CBR is given based on the steady-state analysis. In addition, for the three-phase CBR, the reason that the traditional control strategy is capable of realizing unity power factor rectification while mitigating input current zero-crossing distortion is analyzed. Finally, simulations in the MATLAB/Simulink environment and experimental results from scaled-down laboratory prototypes are provided to verify the proposed theories.

Design of GaN-Based MHz Totem-Pole PFC Rectifier

The totem-pole bridgeless power factor correction (PFC) rectifier has recently been recognized as a promising front-end candidate for applications like servers and telecommunication power supplies. This paper begins with a discussion of the advantages of using emerging high-voltage gallium-nitride (GaN) devices in totem-pole PFC rectifiers rather than traditional PFC rectifiers. The critical-mode operation is used in the totem-pole PFC rectifier in order to achieve both high frequency and high efficiency. Then, several high-frequency issues and detailed design considerations are introduced, including extending zero-voltage-switching operation for the entire line-cycle, a variable on-time strategy for zero-crossing distortion suppression, and interleaving control for ripple current cancellation. The volume reduction of differential-mode electromagnetic interference filters is also presented, which benefits greatly from MHz high-frequency operation and multiphase interleaving. Finally, a dual-phase interleaved GaN-based MHz totem-pole PFC rectifier is demonstrated with 99% peak efficiency and 220 W/in $^{\mathrm {{3}}}$ power density.

AC–DC–AC Three-Phase Converter Based on Three Three-Leg Converters Connected in Series

A unidirectional ac–dc–ac three-phase dc-link converter is proposed in this paper. It is composed of three unidirectional ac–dc–ac three-leg converters. The three-leg converter is composed of a noncontrolled leg, two controlled legs, and a dc-link. A suitable model and control strategy of the system, including a synchronization method, are proposed. The synchronization method, associated with the pulse width modulation (PWM) strategy, imposes that the grid currents and load voltages have the same phase angle of the converter voltages. This method ensures sinusoidal grid currents and mitigate the zero-crossing distortions normally caused by the use of diodes. Simulation and experimental results are also presented for validation purposes.

Inductor Compensation in Three Phase PFC Control with Decoupling the Input Voltage and Bus Voltage

As the nonlinear structure of the boost ac/dc topology, the PFC is difficult to be controlled. The average state space theory has revealed that the choke current is determined by duty-ratio coupled with input voltage and bus voltage, which makes the high-performance sine-wave current track control more challenging. To remove disturbing variables and reduce the zero-crossing distortion, the decoupling control strategy is presented. Also, it is shown in this paper that the variable inductance has a great influence on PFC and THDI. As the inductor in boost converter varies with the current, a compensating coefficient of current is also proposed. The decoupling strategy and the inductor compensation strategy are implemented on a UPS with three phase input voltage. Numerical simulation and experimental results has indicated the high-performance of these control strategy.

Nonlinear modeling and predictive functional control of Hammerstein system with application to the turntable servo system

This article deals with the identification of nonlinear model and Nonlinear Predictive Functional Controller (NPFC) design based on the Hammerstein structure for the turntable servo system. As a mechanism with multi-mass rotational system, nonlinearities significantly influence the system operation, especially when the turntable is in the states of zero-crossing distortion or rapid acceleration/deceleration, etc. The field data from identification experiments are processed by Comprehensive Learning Particle Swarm Optimization (CLPSO). As a result, Hammerstein model can be derived to describe the input–output relationship globally, considering all the linear and nonlinear factors of the turntable system. Cross validation results demonstrate good correspondence between the real equipment and the identified model. In the second part of this manuscript, a nonlinear control strategy based on the genetic algorithm and predictive control is developed. The global nonlinear predictive controller is carried out by two steps: (i) build the linear predictive functional controller with state space equations for the linear subsystem of Hammerstein model, and (ii) optimize the global control variable by minimizing the cost function through genetic algorithm. On the basis of distinguish model for turntable and the effectiveness of NPFC, the good performance of tracking ability is achieved in the simulation results.

Improved Elimination Scheme of Current Zero-Crossing Distortion in Unipolar Hysteresis Current Controlled Grid-Connected Inverter

In this paper, the generation reason and the improved elimination scheme of the current zero-crossing distortion (ZCD) of single-phase grid-connected inverter controlled by unipolar hysteresis current control containing band are investigated in detail. A current ZCD elimination scheme by exchanging the control signal of low-frequency leg of inverter ahead of the zero-crossing points of grid voltage is proposed. The effect of the variation of the amplitude and frequency of tied grid and the filter inductor on the optimal leading exchanging phase angle (LEPA) is analyzed. A single-phase hybrid filter-based enhanced phase-locked loop is proposed to estimate accurately the information of the grid, even under nonideal input conditions. Then, an online filter inductor estimation scheme is proposed to obtain the accurate actual inductor value. The former estimated parameters are used to calculate the exact optimal LEPA online to improve the performance of the current ZCD elimination scheme. Comprehensive experimental results are represented to verify the accuracy and feasibility of the theoretical analysis and the proposed improvement.

Microcontroller-based inverter topology integrated in PV systems

Purpose – The purpose of this paper is to study the problem of the leakage currents in transformerless inverter topologies. It proposes a novel topology and how important the adopted control strategy on the power quality produced by the inverter. Design/methodology/approach – The paper presents an investigation of a novel transformerless inverter topology. It adopted a control strategy in which the DC source is disconnected from the inverter when the zero vectors of the control are applied. By using such control strategy, the electrical efficiency of the whole system was improved and the leakage current was significantly reduced. Findings – The paper provides a solution to minimize the leakage current in transformerless inverter topologies. Besides, the problem of zero-crossing distortions was totally eliminated. Research limitations/implications – Because of the high conversion ratio of the boost converter, the efficiency of the whole system needs to be enhanced. Practical implications – The paper includes the experimental results of the proposed topology which are in good match with the simulation results. Originality/value – This paper identifies a need to study the leakage current phenomena in transformerless inverter topologies.

A 10-bit 1.8 V 45 mW 100 MHz CMOS transmitter chip for use in an XDSL modem in a home network

This paper describes a 10-bit 1.8 V 45 mW 100 MHz transmitter chip (TX chip) that is fabricated using 0.18 μm 1P6 M CMOS technology for use in an xDSL modem in a home network. The chip is composed of a 10-bit segmented digital-to-analog converter (DAC) and a fully differential adaptive line driver (LD). In designing the DAC, the switched-current method is used to increase the conversion speed; the anti-process-variation current cell with threshold-voltage compensation is used to reduce the linearity error, and the current cell, with differential input and gain boosting, is used to minimize the feedthrough error and tapered error distribution. The circuit layout of the current source has four-phase symmetry, not only to increase the linearity but also to eliminate the gradient error. To design a fully differential adaptive LD, the feed-forward capacitor and quiescent current control circuit are used to reduce the zero-crossing distortion and to minimize the second-order harmonic. Additionally, the power efficiency is increased using an output-impedance matching circuit. Measurements reveal that, for a TX chip at a differential load of 100 Ω and a supplied voltage of 1.8 V, the efficient number of bits, operating frequency, output voltage, output current, power consumption, differential nonlinearity error and integral nonlinearity error are 9 bits, 100 MHz, ± 0.874 V, ± 10 mA, 45.8 mW, ?0.80 to +0.62 LSB, and ?0.92 to +0.82 LSB, respectively.

Single-Phase to Three-Phase DC-Link Converters With Reduced Controlled Switch Count

This paper presents single- to three-phase dc-link converters with a reduced number of controlled switches for either usual or reduced currents in switches of the rectifier. A suitable model and a control strategy, including a synchronization approach, are developed to obtain the maximum dc-link voltage utilization. Such a synchronization method, associated with the pulse-width-modulated generation signal, forces the input current to have the same phase angle as the input voltage. The main advantage of the proposed converters along with the synchronization method is the reduction of the zero-crossing distortion normally caused by the use of diodes. Simulated and experimental results are presented to confirm the validity of the theoretical expectations.

Suppression of zero-crossing distortion for single-phase grid-connected photovoltaic inverters with unipolar modulation

For single-phase grid-connected photovoltaic inverters, current-control with unipolar modulation can reduce the losses of power tubes and improve the efficiency compared with using the bipolar modulation. However, it suffers inherent zero-crossing distortion which is related to the grid current and voltage. In this paper, the reason for zero-crossing distortion is analyzed and simulated, also a novel current-control approach with commutating in advance is proposed to resolve this problem. This approach obtains a leading angle of the grid current by using the feedback of proportional-integral controller of the unipolar inverter, and then set the working mode of power tubes according to this angle through commutation.

Analysis and Solution of Current Zero-Crossing Distortion With Unipolar Hysteresis Current Control in Grid-Connected Inverter

In this paper, a kind of zero-crossing distortion (ZCD) generated in the grid-connected current of a single-phase grid-connected inverter with unipolar hysteresis current control is investigated. By establishing the mathematical model of the grid-connected inverter around the zero-crossing points (ZCPs), the reason for causing the current ZCD is presented. It is ascribed to the slope of the actual current less than that of the reference one around the ZCPs. The expressions of the critical phase angle (the starting point of the current ZCD) and the amplitude of the current distortion corresponding to the parameters of the inverter and connected utility grid are obtained, and the solution for the ZCD based on on-line leading phase angle compensation is proposed. Simulation and experimental results verify the accuracy and feasibility of the theoretical analysis and the proposed solution.

Design and Implementation of Motion Control System with Precise Driving Mechanism

In this paper, a motion control system based on 2-axis gimbal system is designed and implemented to drive a high speed and precision. The proposed system consists of the RS-422 interface, 2-axis gimbal platform, SCU (servo control unit) integrated with a high speed DSP chipset, SAU (servo amplifier unit), potentiometer sensor unit, and resolver sensor unit. The SCU using the DSP firmware is designed to get a fast response without an overshoot with step input and a RMS error of low probability with ramp input. The SAU using a voltage control is designed to resolve the zero-crossing distortion for precise motion. To verify the performance and stability of the implemented system, experiments are performed through a measurement of the time and frequency domain response in a laboratory environment by using a PXI (PCI extentions for instrumentation).

정밀구동메커니즘 적용 모션제어시스템 설계 및 구현

In this paper, a motion control system based on 2-axis gimbal system is designed and implemented to drive a high speed and precision. The proposed system consists of the RS-422 interface, 2-axis gimbal platform, servo control unit integrated with a high speed DSP chip-set, servo amplifier unit, potentiometer sensor unit, and resolver sensor unit. The servo control unit using the high speed DSP firmware is designed to get a fast response without an overshoot with step input and a RMS error of low probability with ramp input. The servo amplifier unit using a voltage control is designed to resolve the zero-crossing distortion for precise motion. To verify the performance and stability of the implemented system, experiments are performed through a measurement of the time and frequency domain response in a laboratory environment by using a PXI(PCI eXtentions for Instrumentation).

Cascade Dual Buck Inverter With Phase-Shift Control

This paper presents a new type of cascade inverter based on dual buck topology and phase-shift control scheme. The proposed cascade dual buck inverter with phase-shift control inherits all the merits of dual buck type inverters and overcomes some of their drawbacks. Compared to traditional cascade inverters, it has much enhanced system reliability thanks to no shoot-through problems and lower switching loss with the help of using power MOSFETs. With phase-shift control, it theoretically eliminates the inherent current zero-crossing distortion of the single-unit dual buck type inverter. In addition, phase-shift control and cascade topology can greatly reduce the ripple current or cut down the size of passive components by increasing the equivalent switching frequency. A cascade dual buck inverter has been designed and tested to demonstrate the feasibility and advantages of the system by comparing single-unit dual buck inverter, 2-unit and 3-unit cascade dual buck inverters at the same 1 kW, 120 V ac output conditions.

Design of Zero-crossing Distortion of Boost Power Factor Correction (PFC) Based on Feedforward Current Control Slope Compensation

该文提出了一种前馈电流控制的斜坡补偿方法，将该方法引入到临界导通Boost 功率因数校正(PFC)转换器的设计中，以减小零交越失真问题，改善谐波电流和频率对系统的限制。基于临界导通Boost PFC转换器的拓扑结构，理论分析了前馈电流控制斜坡补偿技术对脉冲宽度调制(PWM)信号占空比的调制作用，推导出补偿斜率与输入线电压的关系式，迫使线电压零交越点附近的电流跟随电压变化。仿真和测试结果表明，该方法可有效抑制零交越失真现象，提高系统的动态性能，尤其在高频及轻负载情况下。测得Boost PFC转换器的总谐波失真(THD)仅为3.8%，功率因数0.988，负载调整率3%，线性调整率小于1%，效率达到97.3%。有效芯片面积为1.611.52 mm2。

The Zero-Crossing Distortion and One Cycle Control in Single-phase PFC

Input current distortion in the vicinity of input voltage zero crossing of Boost single-phase active power factor corrected rectifier in high line frequency is studied based on one cycle control method in this paper. The current loop model and input admittance model of active power correction based on one cycle control is particularly analyzed. The results point out that its equivalent power stage of current loop is a 1st order system, and that its input admittance is the pure resistive around low frequency domain and the capacitive characteristics above 1 kHz. From about the frequency 1 kHz, then, the input line current phase leads input voltage. However, it is does not matter in aero ac power system with 400Hz or 360~800Hz line frequency in the future, and it is suitable for applications as front converter in aero power supply system.

Current Phase Lead Compensation in Single-Phase PFC Boost Converters With a Reduced Switching Frequency to Line Frequency Ratio

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Traditional design of the current loop controller in a single-phase power factor correction boost converter is not suitable for applications with higher line frequencies (up to 800 Hz) because of the zero-crossing distortion and high harmonic content due to the current phase lead effect. Increasing the control bandwidth and switching frequency in order to avoid this effect would reduce converter efficiency and is objectionable. The paper presents the leading-phase admittance cancellation (LPAC) technique, which improves the current-shaping control structure and eliminates the current phase lead without increasing the bandwidth requirement. The LPAC method extends the allowable line frequency range from 1/150 to 1/5 of the current loop bandwidth. The LPAC method is load-invariant and superior to other previously proposed methods. The LPAC network can be added to existing designs, which would require only two passive components in the simplest case. </para>