Voltage Tracking Research Articles

Robust control of switch-mode rectifier considering nonlinear behaviour

This work presents the disturbance observer-based robust current and voltage controls for a digital signal processor (DSP)-based boost-type switch-mode rectifier (SMR) considering nonlinear behaviour. First, a robust current control scheme is developed to let the SMR inductor current waveform closely track its command around zero-crossing points, and hence the SMR possesses improved line drawn power quality. Then a robust voltage two-degrees-of-freedom control (2DOFC) scheme and its systematic design approach are proposed. In determining the power circuit components and the key parameters of the proposed robust control schemes, the compromise between the desired performance and the nonlinear behaviours is considered. Specifically, the adaptation of voltage robust compensation control is made according to the observed nonlinear phenomena. Experimental results confirm that robust and good voltage tracking and regulation responses are obtained by the developed SMR. Furthermore, the developed SMR is successfully applied to serve as a front-end converter of a switched reluctance motor drive, and its effectiveness in vibration reduction and power quality improvement is demonstrated experimentally.

Dual-Mode Time-Sharing Sinewave-Modulation Soft Switching Boost Full-Bridge One-Stage Power Conditioner Without Electrolytic Capacitor DC Link

This paper is aimed at presenting a novel system topology and control scheme of a selective dual-mode pulse-modulated high-efficiency single-phase sinewave power-conversion circuit for the new energy generation and storage applications. This power-conversion system is composed of a time-sharing-operated sinewave-absolute-modulation boost chopper with a bypass diode in the first power conditioning and processing stage and time-sharing sinewave partially pulse-modulated full-bridge inverter in the second stage. The proposed power conditioner is operated by a selective time-sharing dual-mode pulse pattern signal processing control scheme without electrolytic capacitor dc link. The unique operating principle of the two-power conditioning and processing stages with sectional time-sharing dual-mode partial sinewave-modulation scheme is described and discussed with a design example. In addition, this paper proposes also a sinewave tracking voltage controlled soft switching pulsewidth-modulation boost chopper with a bypass-diode loop, which includes a passive auxiliary edge-resonant snubber. The new conceptual operating principle and the control implementation of this novel power conditioner are presented and evaluated through experimental and simulation results

Linear and Nonlinear Control Techniques for a Three-Phase Three-Level NPC Boost Rectifier

This paper deals with three control techniques for a three-phase three-level neutral-point-clamped (NPC) boost rectifier to study their relative performance. Linear, nonlinear, and nonlinear model reference adaptive control (MRAC) methods are developed to control power factor (PF) and regulate output and neutral point voltages. These controllers are designed in Simulink and implemented in real time using the DS1104 DSP of dSPACE for validation on a 1.2-kW prototype of an NPC boost rectifier operating at 1.92 kHz. The performance of boost converter with three control methods has been investigated respectively in steady state in terms of line-current harmonic distortion, efficiency, and PF and during transients such as load steps, utility disturbances, reactive power control, and dc-bus voltage tracking behavior. The linear PI controllers are characterized by reduced complexity but poor performance, whereas the nonlinear control technique has improved the converter performance significantly, while nonlinear MRAC exhibits much better performance in a wide operating range

Maximum power tracking of piezoelectric transformer HV converters under load variations

The problem of maximum power point tracking of high output dc voltage converters that apply piezoelectric transformers (PT) and voltage doublers was studied theoretically and experimentally. It was shown that the operating frequency of the PT, at which maximum power is reached, is a function of the load. Hence, under load variations, and to overcome parameter instability, there is a need for some frequency tracking mechanism that will help to lock the operating frequency to the optimum one. The proposed method to achieve frequency tracking is based on a phase locked loop (PLL). The PLL inputs are the phase of the input voltage driving the PT and the phase of the current flowing through one of the voltage doubler diodes. Theoretical analysis, verified by experiments, shows that when the phase shift of the diode current relative the phase of the input voltage is zero, the voltage gain of the system is at its maximum. By applying this approach, the system's operation can be made independent of input voltage, load variations, temperature (within a permitted range), and the spread and nonlinearity of the PT parameters, as well as their drift with time.

Power Budgeting of a Multiple-Input Buck-Boost Converter

The use of a multiple-input buck-boost converter for budgeting power between different energy sources is discussed. It is shown mathematically that the idealized converter can accommodate arbitrary power commands for each input source while maintaining a prescribed output voltage. Power budgeting is demonstrated experimentally for a real converter under various circumstances, including a two-input (solar and line-powered) system. A closed-loop control example involving simultaneous tracking of output voltage and set-point tracking of the solar array shows that an autonomous system is realizable.

NODAL VOLTAGE CONTROL IN POWER SYSTEMS BASED ON THE MODEL-REFERENCE ADAPTIVE APPROACH

The paper illustrates the design of a power system voltage control scheme based on the model reference adaptive approach. Firstly, for an assigned operating condition, a power system approximated linear model is build-up which represents the system dynamics as seen from the busbar at which the controller is connected. Then, by imposing a desired reference model, the controller parameters are obtained by solving the model-following problem which ensures that the controlled voltage tracks the voltage reference. In presence of unknown operating conditions changes, the regulator parameters are varied according to an adjustment laws designed on the basis of the gradient rule. The task of the adaptation mechanism is to counteract the effects of such changes. Referring to a Static VAR System (SVS) controllable compensator device the adopted model-reference adaptive control scheme has been designed and its performance analyzed by accurate numerical time simulation studies in the case of both unknown load variations and changes in the power system structure, in particular line opening.

High-performance flux-based two-degrees-of-freedom uninterruptible power supply

A three-phase flux-based two-degrees-of-freedom uninterruptible power supply with improved voltage regulation performance is presented. The proposed AC supply is controlled using an outer P+resonant voltage regulation loop to nullify voltage tracking errors and compensate for unbalanced voltages. Within this outer voltage loop is a flux-based two-degrees-of-freedom inner current regulation loop for the fast compensation of dynamic load changes and other external disturbances. This inner current regulator originates from the combined use of classical two-degrees-of-freedom control theory and a hysteretic flux modulation technique. By integrating the individual advantages of P+resonant compensators, two-degrees-of-freedom control and flux modulation, the proposed AC supply can achieve both precise steady-state tracking and a fast transient response. Theory and experimental results are presented to validate the performance of the proposed AC supply.

New high accuracy CMOS current conveyors

In this paper, a new CMOS CCII + is proposed. The circuit is characterized by high precision in voltage tracking and exhibits very low input resistance. An adaptive voltage offset cancellation methodology is introduced and then applied to the proposed circuit. As a result, a higher accuracy CCII + is presented. For both circuits, the voltage offset cancellation is independent of the input current and voltage. To demonstrate the strength of the proposed architectures, fair comparisons with Liu and Yodprasit CCII realizations are held.

Multilevel Dynamic Voltage Restorer

This letter presents the implementation and control of a high voltage dynamic voltage restorer (HVDVR) for use in power distribution network to compensate for sags in utility voltages. The proposed HVDVR is implemented using a multilevel inverter topology with isolated DC energy storage, allowing the direct connection of the HVDVR to the distribution network without using a bulky and costly series injection transformer. A control algorithm, incorporating P+resonant and Posicast compensators, is also presented for controlling the HVDVR with perfect reference voltage tracking and effective damping of transient voltage oscillations at the instant of sag compensation. Finally, simulation results are presented to verify the performance of the proposed multilevel HVDVR.

Closure on “Theoretical and Experimental Analyses of Photovoltaic Systems With Voltage and Current-Based Maximum Power Point Tracking”

Closure on “Theoretical and Experimental Analyses of Photovoltaic Systems With Voltage and Current-Based Maximum Power Point Tracking”

Discussion of “Theoretical and Experimental Analyses of Photovoltaic Systems With Voltage and Current-Based Maximum Power Point Tracking”

For original paper see Masoum et al. (IEEE Trans. Energy Conversion, vol.17, p.514-22, December 2002).

Discussion of “Theoretical and Experimental Analyses of Photovoltaic Systems With Voltage and Current-Based Maximum Power Point Tracking”

For original paper see Masoum et al. (IEEE Trans. Energy Convergence, vol.17, p.514-22, December 2002).

Improved transient and steady‐state performance of series resonant ZCS high‐frequency inverter‐coupled voltage multiplier converter with dual mode PFM control scheme

AbstractA variety of switched‐mode high‐voltage DC power supplies using voltage‐fed‐type or current‐fed‐type high‐frequency transformer resonant inverters with MOS gate bipolar power transistors (IGBTs) have been recently developed for medical‐use X‐ray high power generators. In general, the high‐voltage high‐power X‐ray generator using voltage‐fed high‐frequency inverter with a high‐voltage transformer link has to meet some performances such as (i) short rising period in start transient of X‐ray tube voltage, (ii) no overshoot transient response in tube voltage, (iii) minimized voltage ripple in periodic steady‐state under extremely wide load variations and filament heater current fluctuation conditions of the X‐ray tube.This paper presents two lossless inductor snubber‐assisted series resonant zero current soft switching high‐frequency inverters using a diode‐capacitor ladder‐type voltage multiplier called Cockcroft‐Walton circuit, which is effectively implemented for a high DC voltage X‐ray power generator. This DC high‐voltage generator which incorporates a pulse frequency modulated series resonant inverter using IGBT power module packages is based on the operation principle of zero current soft switching commutation scheme under discontinuous resonant current and continuous resonant current transition modes. This series capacitor compensated for transformer resonant power converter with a high‐frequency transformer‐linked voltage boost multiplier can efficiently work a novel selectively changed dual mode PFM control scheme in order to improve the start transient and steady‐state response characteristics and can completely achieve stable zero current soft switching commutation tube filament current dependent on wide load parameter setting values with the aid of two lossless inductor snubbers. It is proved on the basis of simulation and experimental results in which a simple and low cost control implementation based on selectively changed dual‐mode PFM for high‐voltage X‐ray DC‐DC power converter with a voltage multiplier strategy has some specified voltage pattern tracking voltage response performances under rapid rising time and no overshoot in start transient tube voltage as well as the minimized steady‐state voltage ripple in tube voltage. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 149(4): 60–72, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10345

New Wide Band Low Power CMOS Current Conveyors

New Class-A second-generation CMOS current conveyor (CCII) suitable for high frequency applications is proposed. It provides low input impedance and accurate voltage and current tracking. Targeting low power dissipation, the Class-AB version of the proposed Class-A architecture is introduced as well. Simulation results are included.

A Robust Approach to Controller Design for DC-DC Quasi-Resonant Converters

DC-DC quasi-resonant converters (QRCs) have a highly nonlinear and time-varying behavior as well as other types of DC-DC resonant converters such as conventional and multi-resonant converters. Changing in operating conditions, mainly due to variation in load and line disturbance, leads to significant changes on system dynamics so that desired performance and even stability are lost. Taking into consideration the uprising need for high-quality resonant power converters has opened a new research window on the control of these systems using modern and systematic approaches.In this paper in order to achieve both stability and desired performance, such as reduced sensitivity to load variations, desired disturbance rejection, reduced output impedance and attenuated transfer from input to output, we have proposed a methodology based on μ-synthesis technique for DC-DC QRCs controller design. The μ-analysis is used to verify the robustness of the designed controller. The proposed control strategy is applied to a typical zero-current switching QRC and nonlinear simulation is performed using nonlinear model of converter circuit. The simulation results demonstrate the good reference voltage tracking, line disturbance rejection and show that the designed procedure guarantees the robust stability and robust performance for a wide range of load variation.

Sliding mode control of boost and buck‐boost power converters using the dynamic sliding manifold

AbstractNon‐minimum phase tracking control is studied for boost and buck‐boost power converters. A sliding mode control algorithm is developed to track directly a causal voltage tracking profile given by an exogenous system. The approximate causal output non‐minimum phase asymptotic tracking in non‐linear boost and buck‐boost power converters is addressed via sliding mode control using a dynamic sliding manifold (DSM). Use of DSM allows the stabilization of the internal dynamics when the output tracking error tends asymptotically to zero in the sliding mode. The sliding mode controller with DSM links features of conventional sliding mode control (insensitivity to matched non‐linearities and disturbances) and a conventional dynamic compensator (accommodation to unmatched disturbances). Numerical examples demonstrate the effectiveness of the sliding mode controller even for a known time‐varying load. Copyright © 2003 John Wiley & Sons, Ltd.

Sliding mode control of boost and buck-boost power converters using method of stable system centre

Nonminimum phase tracking control is studied for boost and buck-boost power converters. The sliding mode controller is designed to track directly a causal voltage tracking profile given by an exogenous system. The nonminimum phase output tracking problem is reduced to a state tracking problem. Bounded state tracking profiles are generated by equations of stable system centre. Numerical examples demonstrate the effectiveness of the sliding mode control design.

Input-output linearization and zero-dynamics control of three-phase AC/DC voltage-source converters

Nonlinear differential-geometric techniques are proposed for the design of a feedback controller for three-phase voltage-source pulsewidth modulation (PWM) AC/DC boost converters under a cascade control structure. The input-output linearizability of the system modeled in d-q synchronous reference frames is examined. The results lead to a decoupled d-q current control scheme. For the internal DC-bus voltage dynamics (zero dynamics), by considering the d-axis current command as control input and using a square transform on DC-bus voltage, it is shown that this remaining system contains an input memoryless nonlinearity of conic sector type and satisfies the conditions for a Lur'e plant. This suggests a new outer-loop control strategy to control the square of the DC output voltage, rather than DC output voltage itself, utilizing a simple proportional plus integral (PI) controller cascaded to the d-axis current loop. Since most results do not consider the control of zero dynamics, the strategy for the control of zero dynamics via cascade control structure may provide valuable insight for the design of input-output linearized systems in which zero dynamics contain some desired control variables. The absolute tracking concept for Lur'e plants is introduced to prove the global tracking capability with zero steady-state error of the voltage loop. The controlled PWM AC/DC converter has the features of global stability, fast (exponential) tracking of DC-bus voltage command with zero steady-state error, asymptotic rejection of load disturbance, robustness against parameter uncertainties and decoupled dynamical responses between d and q current loops. Also, measurement of load current is not required. All these features are confirmed via laboratory experiments on a 1.5 kVA PC-based controlled prototype.

Robust multivariable control design for HVDC back to back schemes

A robust multivariable control design procedure for HVDC back-to-back schemes is presented. HVDC links are commonly controlled with a decentralised structure, whereby in normal operation the rectifier may track direct current and the inverter may track direct voltage, firing angle or extinction angle. In the case of a back-to-back HVDC link the measurements of control variables of both sides are physically close, hence it is possible to apply a true multivariable controller whereby current and voltage are controlled by rectifier and inverter together. H-infinity control theory is used for a systematic tuning procedure which incorporates robustness against uncertainty in the short-circuit levels of both rectifier and inverter side AC systems. The linear control transfer functions for rectifier and inverter controllers are arrived at simultaneously thereby removing iterative design steps to find the best combination of control parameters for both rectifier and inverter controllers. The decoupling effect resulting from the multivariable controller structure reduces the interaction between tracking of direct current and direct voltage. It is verified by nonlinear EMTDC simulation that the designed controller is robust and can contribute to good fault recovery when integrated with other control loops and nonlinear control functions as implemented in manufactured controls.

Nonlinear state feedback control design for three-phase PWM boost rectifiers using extended linearisation

The technique of extended linearisation is proposed to design state feedback controllers for three-phase PWM boost rectifiers to achieve DC-bus voltage tracking and unity power factor. Despite the nonminimum phase feature of the boost rectifier, this approach provides direct DC-bus voltage control capability. A nonlinear state feedback law that smoothly interpolates stabilising gains at operating points with infinitesimally small distances is synthesised. The design process involves messy but routine symbolic computation of linear algebraic equations, and is accomplished with the help of MAPLE computer software. Experimental verification of the proposed control algorithm is conducted on a laboratory prototype. Comparisons with a Lyapunov-based controller and a linear PI-based controller are also provided, which demonstrate the salient performance of the proposed design.