One-cycle Control Research Articles

Hopf Bifurcation and Its Control in the One-Cycle Controlled Cuk Converter

One-cycle controlled Cuk converters are prone to exhibit oscillation at the input stage as a result of Hopf bifurcation. A controller based on time delay feedback is proposed to eliminate the oscillation and stabilize the converter. The controller introduces two new parameters, which are known as the feedback gain and the delayed time. These two parameters are of great importance in stabilizing the converter. The averaged model of the converter is adopted to select the parameters. A necessary condition for the converter to be stabilized gives an effective range of the two parameters. An experimental Cuk converter was constructed for verification purposes. The waveforms in front of load changes are provided. The results show that the proposed controller eliminated the oscillation in the input stage of the converter. The controller allows widening of the stability domain and decreases switch voltage stress in the input stage of the one-cycle controlled Cuk converter.

Experimental evaluation of active power factor correction techniques in a single‐phase AC‐DC boost converter

SummaryThe increasing need to improve power quality with the reduction of the harmonic content of current and voltage waveforms has been intensively analyzed in several studies, thus motivating the proposal of many high power factor rectifiers based on the classic converters such as boost and buck‐boost. Moreover, distinct control techniques have also been proposed due to the commercial availability of integrated circuits (ICs) dedicated to impose sinusoidal input currents in switch‐mode power supplies (SMPSs). The boost converter operating in continuous conduction mode (CCM) is by far the most traditional choice for this purpose due to circuit simplicity and low electromagnetic interference (EMI) levels. Within this context, this work analyzes some of the most important control techniques used in power factor correction (PFC). The performance of a single‐phase boost converter using peak current mode control (PCMC), average current mode control (ACMC), and one cycle control (OCC) is evaluated experimentally in detail. A comprehensive analysis of key aspects such as the input current waveform and respective harmonic content, dc output voltage, and dynamic response of the converter is also presented.

Design and operation of an OCC‐based scheme for a stand‐alone PV system powering DC loads

Distributed energy resources such as stand-alone photovoltaic (PV) systems have been widely used in electric systems in the last decades due to the increase in global energy demand, and the concern about the environmental problems caused by fossil fuels power generation. Owing to the fast growing of direct current (DC) microgrids and electronic devices, such as their current compatibility nature in relation to primary sources, a small-scale stand-alone PV system with battery storage for DC applications is proposed in this work. The system consists of three DC-DC converters which operate according to the PV panel power and the main bus load demand. The control of these converters considers the quality in power supply ensuring safety to the loads and batteries of the system. Thus, this study proposes the implementation of the control units through the use of one-cycle control (OCC) which allows fast response to transient conditions, great accuracy of convergence and has low-cost analogue implementation. In this study, one-cycle controllers' waveforms are analysed in steady-state conditions and its duty cycles are compared with the expected in relation to the system operation. Simulations of transition conditions were performed through real situations such as cloud-edge effects, slow passing clouds and absence of sunlight.

One‐cycle decoupling control method of multi‐leg switching power amplifier for magnetic bearing system

The traditional current control algorithm of the multi-leg switching power amplifier (SPA) is complicated since the control of different phase currents is intercoupling. To address this problem, a novel control strategy based on one-cycle control is proposed in this study, which can enforce the average current of each phase is equal to the reference in each control cycle. Since it sets the duty cycle of the neutral leg as a constant, this method presents significant advantages such as quick dynamic response, easy control and decoupling of the phase currents. Taking a five-phase six-leg SPA, e.g. the mathematic model of the system was built, the duty cycle of the neutral leg was analysed, the principle of the novel control strategy was introduced, and the detailed implemented process was presented. Thereby, a high-speed switched reluctance motor system using the magnetic bearing is constructed to test this method. Both the simulation and experimental results have demonstrated the simplicity and effectiveness of the proposed method.

A Closed-Loop Modulation Scheme for Duty Cycle Compensation of PWM Voltage Distortion at High Switching Frequency Inverter

Wide bandgap semiconductors with fast switching speed capability are becoming an enabler to achieve the higher power density design. However, the further increase of switching frequency cannot continuously improve the power quality of ac-side waveforms in dc–ac/ac–dc application. The main reason is the distortion of pulsewidth modulation (PWM) voltage at switching point under high switching frequency. In general, there are two contributors causing PWM voltage distortions in bridge-based topologies. One is the deadtime, which occupies higher ratio in the small duty cycle case under high switching frequency and induces the voltage errors. The other one is the turn- off transient in the small load current or around the zero-crossing point of the ac-side current, because the relatively slow rising slope of the drain–source voltage will affect the right duty cycle. To solve this issue, this paper proposes a closed-loop modulation scheme to compensate the duty cycle distortion of PWM voltage based on one-cycle control or charge control. Compared to the traditional feedforward type of compensation, the proposed scheme does not need online calculation and instantaneous inductor current sampling, and it shows potential to be a general scheme for variety of topologies and modulations. Simulations and experiments are carried out on a 400-kHz single-phase full-bridge inverter with 400-Hz fundamental frequency to demonstrate the performance of the proposed approach.

One-Cycle Controlled Bridgeless SEPIC with Coupled Inductors for PAM Control-Based BLDC Drive

This paper presents a novel approach for the speed control of BLDC motor for residential air conditioning application, using pulse amplitude modulation (PAM) control of voltage source inverter (VSI). PAM control of VSI is accomplished by using a bridgeless SEPIC converter embedded with coupled inductors at the front end and adopting one-cycle control (OCC) technique in the inner voltage control loop. The DC reference voltage required for inner voltage control loop is obtained using a PI controller in the outer speed control loop and speed feedback signal. The PAM control (DC supply voltage control) of VSI reduces switching losses by allowing the operation of VSI at fundamental frequency. Bridgeless SEPIC with coupled inductors is designed to enable PAM control for VSI and is operated in discontinuous conduction mode (DCM) for the complete range of DC link voltage. DCM operation simplifies power factor correction control scheme to a simple voltage follower approach, since it has inherent input current shaping feature. The introduction of coupled inductors in the bridgeless SEPIC converter lowers the overall count of components, allows better integration and lowers the requirement of inductance, compared to conventional bridgeless SEPIC. OCC which is a nonlinear control technique, used in the voltage control loop, enhances the performance with improved startup and transient state response. It also improves the quality of supply current drawn by reducing the distortion compared to PI control technique. The proposed BLDC motor drive is modelled and simulated using MATLAB/Simulink. The performance of proposed system is evaluated for a wide range of speed control. The experimental prototype for bridgeless SEPIC with coupled inductors is implemented. The inherent power factor correction for supply voltage variations is validated using the results. The bridgeless operation of the converter with coupled inductor configuration is also described with experimental waveforms at rated supply voltage of 220 V.

A Modified One-Cycle-Control Method for Modular Multilevel Converters

In this paper, a new One-Cycle-Control (OCC) method is designed for a modular multilevel converter (MMC) based on the principle of the equivalent resistance constant. The proposed controller has a simple structure and a small amount of calculation by cancelling the current inner loop proportional integral (PI) controller and the inverse transform in the traditional direct-quadrature (DQ) control. Compared to the traditional OCC controller, the new one separates the control method from the modulation strategy, making it possible to use not only carrier-based pulse-width modulation (PWM), but also nearest level modulation PWM to generate drive signals. Besides, the independent control of the active and the reactive power is implemented by injecting a reference current with the same phase of the supply voltage or a reference current which lags the supply voltage by π/2 into the controller, so the converter can operate in four quadrants and it can work in either a grid-connect or off-grid environment. The feasibility and the performance of the proposed OCC method have been validated by both the simulation under the MATLAB/SIMULINK (R2012a) environment and experimental results.

Variable Frequency Constant Current Control Method for Switched-Capacitor Converter Based Automotive LED Driver

A variable-frequency constant-current control (VFCCC) method with the constant ON-time is proposed in this paper for a switched-capacitor (SC) converter-based automotive LED driver. This control method is based on the one-cycle control method. The stable load current regulation could be achieved with the simple analog topology. The variable load current is conveniently set by changing the reference value. In order to reduce the current spikes, the SC topology presented in this paper introduces an inductor in the charge loop. To verify the performance of the proposed control method, a 36-W SC converter is constructed. The VFCCC-controlled SC converter is tested under different operation conditions with the different input voltages and variable constant ON-time. The experimental and simulated results show that with the proposed control method, the external disturbance could be rejected with the fast-dynamical response speed and robust performance. With the SC converter, the high-power density could be realized for the automotive LED driver. The VFCCC control method is suited for the different topologies of SC converters. It could facilitate the SC applications for the automotive LED driver.

One-Cycle Control Based Vienna Rectifiers with Input Power Factor Regulation

In this paper, a crucial technique for incorporating reactive power compensation functionality into Vienna rectifiers is discussed and a modified one-cycle-control (MOCC) scheme is proposed for regulating three-phase Vienna rectifiers operating under leading, lagging or unity power factor with sinusoidal input current. The operating principle of the conventional OCC (COCC) strategy is reviewed simply at first, then the MOCC scheme with input current phase-shift control is discussed in detail. To mitigate input current distortion caused by the current phase-shift, a method by injecting some components to the current command signals is further presented. The implementation of the proposed MOCC scheme is as simple as that of the COCC scheme. In addition, all other advantages exhibited by the COCC scheme, such as no phase-locked loop, no frame transformation and constant switching frequency are also retained by MOCC scheme. The theoretical analysis of the proposed MOCC schemes is fully verified by simulations.

Outer loop filter for improvement of one‐cycle controller

The One‐Cycle Control (OCC) has the ability to operate in line disturbance rejection and provide a faster dynamic response. However, when used as a controller in dc−dc converters, it might contribute to steady‐state error. Furthermore, the non−ideal circuit components may cause a duty cycle error due to the error of converter output voltage. We proposed a new technique to address the error in OCC by using the technique of an outer loop filter based on OCC, called Outer Loop Filter for improvement of One‐Cycle Control (OLF−OCC). This technique maintains a constant output voltage, despite power source voltage perturbation and error from the control circuit, such as circuit integrator voltage slope or input voltage offset. Variation results show that the performance of the proposed technique is more effective and reliable than the traditional approach when compared to the experimental state. OLF–OCC performance is discussed in terms of variation of power source voltage or internal disturbance from the control, such as circuit integrator voltage slope or input voltage offset. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Line Frequency Instability of One-Cycle-Controlled Boost Power Factor Correction Converter

Power Factor Correction (PFC) converters are widely used in engineering. A classical PFC control circuit employs two complicated feedback control loops and a multiplier, while the One-Cycle-Controlled (OCC) PFC converter has a simple control circuit. In OCC PFC converters, the voltage loop is implemented with a PID control and the multiplier is not needed. Although linear theory is used in designing the OCC PFC converter control circuit, it cannot be used in predicting non-linear phenomena in the converter. In this paper, a non-linear model of the OCC PFC Boost converter is proposed based on the double averaging method. The line frequency instability of the converter is predicted by studying the DC component, the first harmonic component and the second harmonic component of the main circuit and the control circuit. The effect of the input voltage and the output capacitance on the stability of the converter is studied. The correctness of the proposed model is verified with numerical simulations and experimental measurements.

Transformer less 1Φ Inverter for Grid-Connected PV Systems with an Optimized Control

This paper investigates the transformerless single-phase inverter incorporates with the photovoltaic system along with the support of grid voltage. Solar Energy is a Non-Conventional Energy source which is mandatory for power generation due to their immeasurable parade and green pleasant nature. One-cycle control (OCC), Ruggedness and consistency which makes the interfacing with the grid easily. For grid interfacing, the inverter circuit does not need phase locked loop facility and are gradually being working for such solicitations. The strategy of the OCC inverter of one stage for solar PV applications is supported by means of a Sinusoidal Pulse Width Modulation to enhance inverter enactment at both low and high insolation levels. These factors allows the plan of a MPPT along P&O controller that pointedly progresses inverter playacting. Though, the OCC-based structures testified previous sensing of the grid voltage which slightly equalizers the strength of its characteristics, In order to dazed the restriction of prior researches, an One Cycle Control based grid-connected one-stage PV system is suggested. The sustainability of the suggested scheme is inveterate by performance simulation justification.

Dual-Comparison One-Cycle Control for Single-Phase Bidirectional Power Converters

Dual-comparison one-cycle control for the bidirectional power flow in single-phase grid-connected converters is proposed in this paper. Advantages of dual-comparison one-cycle control when compared to conventional one-cycle control is that it does not give any steady-state dc offset, no light-load instability, and implements unipolar pulsewidth modulation without having to sense the grid voltage. Addition of a fictitious current term, which is generated from the gating signal of one of the active devices, using a bandpass filter, enables the bidirectional power flow. The quality factor of the bandpass filter is shown to impact the total harmonic distortion in current, fundamental displacement angle, and steady-state dc offset. The optimal value of a quality factor, obtained with aid of simulations, gives a superior performance. The current drawn or injected into the grid is seen to lag the grid voltage. The reason for a nonunity displacement power factor is analyzed and a compensation to achieve a unity displacement power factor is also proposed in this paper. Detailed simulation and experimental studies are carried out to validate the proposed control and the high performance that can be obtained.

One Cycle Control for Battery Connected Standalone Photovoltaic Systems for DC Loads

This paper proposes the utilization of one-cycle controller for multi proposal tasks in a stand-alone photovoltaic system that supplies power to direct current (DC) applications. The photovoltaic system proposed in this paper is composed of one photovoltaic panel, a battery bank as an energy storage system and two DC-DC converters: one for track the maximum power point and the other to regulate the bus voltage for DC applications. Both of the converters are switched by controllers that utilizes the one-cycle control technique instead of the classical pulse width modulation. The one-cycle control technique has been used in the switching converters in this work to allow fast response to transients, no overshoots, zero steady state error and low cost implementation due to the controller analogic circuitry simplicity

Design of a Novel Underground Coal Mine 127V Power Supply

In view of the current disadvantages of the large size, high cost and low power factor of custom transformers in China’s coal mine 127V power supply system, a novel type of unit-power factor rectifier based on OCC (One-Cycle Control) is proposed to supply the underground coal mine lighting system. The power supply consists of three stages, including a Vienna rectifier, a high frequency isolated DC-DC converter and an inverter. However, the first two stages of the control circuit use a coordinated control. The circuit is simple to control, unit power factor operation can be realized without the multiplier and input voltage detection and half of the voltage stress of the switching device can be reduced as well. The paper analyses in detail the basic working principle and double closed-loop control strategy of the new rectifier circuit. The correctness is fully verified by simulations.

The Application of One-Cycle Control Technology in Electric Spring System

This paper first introduced the function, application and the control algorithm of the electric spring (ES), then the working principle of ES are explained. Aiming at the problems that the existing control algorithms have complex structures and are not conducive to accurate tracking of AC voltage signals on sensitive loads, this paper proposes the ES control strategy based on one-cycle control (OCC) technology. In Matlab/SimulinK, the ES system based on the OCC strategy is modeled and simulated. Through the waveform analysis, it is known that when the power of the photovoltaic system injected into the power grid fluctuates, the ES based on the OCC strategy system can operate in a capacitive, inductive or resistive mode automatically, which can achieve a direct and accurate tracking of a given AC voltage signal under the condition that a small amount of reactive power is injected into the grid, thus the voltage of the sensitive load is stabilized, and at the same time the voltage fluctuations on the grid side voltage can be transferred to non-sensitive loads in series with the ES.

Performance Analysis of Current Injection Techniques for Shunt Active Power Filter

Shunt Active Power Filter (SAPF) can be used for compensation of current harmonics generated by non-linear loads. The process involves an injection of equal but opposite current to mitigate the distortion current supplied back by nonlinear load to the voltage supply. Thus, the injected current will shape the supply current to a sinusoidal. SAPF consists of signal processing part and injection part. Processing part generates reference current wave and the injection part injects the reference current parallel to the load. In this paper a comparison is made between three different control strategies for current injection in three-phase three-wire shunt active power filter. The current injection is performed by generating gate pulses pattern for the voltage source inverter using a suitable controller. In this paper three control techniques are compared including Hysteresis Current Control (HCC), Delta Modulation Control (DMC) and One Cycle Control (OCC). The performance of these techniques is evaluated by the accuracy of the injected current in parallel to the load by comparing the required current to be injected and the measured value of the injected current. The performance is also evaluated by measuring Total Harmonic Distortion (THD) of the source current before and after compensation. The results are evaluated and compared using Matlab/Simulink.

Modeling and Analysis of Variable Frequency One-Cycle Control on High-Power Switched-Capacitor Converters

Switched-capacitor (SC) converter is a type of variable structure systems. SC converters are typically equipped with open-loop control or some linear feedback control methods. However, these approaches provide slow dynamic response speed, small operation region, and large voltage ripple. Some new nonlinear control methods have been proposed in the literature to overcome these barriers. However, such control methods are usually proposed for applications involving low-power SC converters due to the limitations of them. This paper presents a nonlinear constant on-time variable frequency one-cycle control (CVFOCC) strategy based on dynamic capacitor ampere-second balance transient calculation (CASBTC) modeling method and one-cycle control (OCC) technique for high-power SC converters. This method successfully addresses the regulation issue of high-power SC converters. A high-power 3X Two-switch Boosting Switched-Capacitor converter (TBSC) is employed as an example topology. Simulation and experimental results both demonstrate that CVFOCC method could significantly improve the dynamic response speed and achieve excellent line and load regulation for the high-power SC converter in wide operation range.

Triple Line-Voltage Cascaded VIENNA Converter Applied as the Medium-Voltage AC Drive

A novel rectifier based on a triple line-voltage cascaded VIENNA converter (LVC-VC) was proposed. Compared to the conventional cascaded H-bridge converters, the switch voltage stress is lower, and the numbers of switches and dc capacitors are fewer under similar operating conditions in the proposed new multilevel converter. The modeling and control for the LVC-VC ware presented. Based on the analysis of the operation principle of the new converter, the power factor correction of the proposed converter was realized by employing a traditional one-cycle control strategy. The minimum average value and maximum harmonic components of the dc-link voltages of the three VIENNA rectifier modules ware calculated. Three VIENNA dc-link voltages were unbalanced under the unbalanced load conditions, so the zero sequence current was injected to the three inner currents for balancing three VIENNA dc-link voltages. Simulation and the results of the experiment verified the availability of the new proposed multilevel converter and the effectiveness of the corresponding control strategy applied.

Hybrid one‐cycle control technique for three‐phase power factor control

One-cycle control technique has been a prominent and suitable solution for improving power quality with the help of three-phase rectifiers. This study proposes a generalised control strategy for the three-phase power factor rectifier based on both the one-cycle control technique and the hybrid pulse-width modulation (PWM) strategy. Improvement of the performance while providing very low-current total harmonic distortion (THD) is achieved with the proposed scheme. Discontinuous and/or continuous PWM operation is possible with advantages of simplicity, robustness, and low cost. Simulation and experimental results confirm the feasibility of the proposed controller.