One-cycle Control Research Articles

A New Discrete Four-Quadrant Control Technique for Grid-Connected Full-Bridge AC–DC Converters

This paper presents a new control technique for grid-connected full-bridge AC–DC converters. The proposed control scheme is based on one-cycle control approach and enables the converter to process power in all four quadrants. In the proposed method, switching pulses are generated using a discrete control law with a superimposed fictitious reactive current term. This term enables seamless four-quadrant operation of the converter. Implementation of the discrete controller includes estimation of the current ripple based on measured values of the input current and voltages, sampled at the beginning of each switching cycle. The estimated current ripple is then used for a carrier-less implementation of the proposed control technique. A detailed controller stability analysis using Lyapunov theory is also presented. Theoretical analysis, simulation results, and experimental results show fast dynamic response for the grid current.

The fundamental phase shift compensation scheme in a digital-controlled VIENNA rectifier with variable carrier-fundamental frequency ratio under unbalanced grid conditions

In the DC power distribution systems, One-cycle control (OCC) based three-phase VIENNA rectifiers achieves high power factor (PF) easily. However, under unbalanced grid conditions, the fundamental phase shift between the input current and corresponding phase voltage obviously deteriorates PF, especially when carrier-fundamental frequency ratio varies. In this paper, based on the mathematical model of the rectifier with OCC control under unbalanced grid conditions, the fundamental phase shift problem is analyzed in detail, including variable carrier-fundamental frequency ratio. Moreover, aiming at solving this problem, a fundamental phase shift compensation scheme is proposed. By introducing a second order generalized integrator (SOGI) to generate the complex vector grid currents feedback, which combines with unbalanced grid voltages, three-phase modulation signals are dynamically modified to eliminate the fundamental phase shift. To facilitate the digital control for the rectifier, the digital implementation of the proposed compensation scheme is described in this paper. At last, a digital-controlled VIENNA rectifier experimental test bench is built, and the effectiveness of the proposed scheme is verified by experimental results.

Power Quality Enhancement of the Distribution Network by Multilevel STATCOM-Compensated Based on Improved One-Cycle Controller

Power Quality Enhancement of the Distribution Network by Multilevel STATCOM-Compensated Based on Improved One-Cycle Controller

DC-Link Capacitor Voltage Balancing Control of a Five-Level Regenerative AC Electronic Load Using One-Cycle Control

High voltage electric power equipment requires rigorous regulation testing to specific standards which ensure proper and safe operation in the grid. Manufacturers conduct these tests in order to prove standard compliance and product liability. Variable linear or nonlinear loads are necessary for testing medium voltage (MV) high power AC power converters. Generally, those AC power converters or power supplies require performance validation, burn-in and/or lifetime testing under different load conditions, defined by the end-user or standards for the given applications. For flexible and efficient MV verification testing, this paper presents a five-level multilevel converter-based MV regenerative AC electronic load with one-cycle control (OCC), which is based on five-level diode-clamped multilevel converters with back-to-back structure and can emulate any impedance load. In this paper, especially the dc-link capacitor voltage balance of the proposed multilevel MV regenerative AC load is deeply analyzed. Simulation and experimental results are presented to verify the dc-link voltage balance performance of the proposed multilevel MV regenerative AC electronic load.

One-Cycle Control of Three-Phase Five-Level Diode-Clamped STATCOM

This paper presents a new multilevel one-cycle control (OCC) technique for a five-level diode-clamped multilevel converter (DCMC)-based static VAR compensator (STATCOM). The OCC algorithm in combination with multi-carrier level-shifted PWM control is used in the proposed five-level DCMC-based STATCOM. The automatic dc link voltage balance is simply realized by four voltage compensators presented as the part of the OCC controller. In this paper the OCC principle of a two-level converter-based STATCOM is reviewed and extended to the five-level DCMC-based STATCOM. The proposed multilevel OCC control method of the five-level DCMC-based STATCOM in steady-state and dynamic operation modes is verified by simulation and experimental results.

Bifurcation Control Method for Buck-Boost Converters Based on Energy Balance Principle

With the variation of parameters, the performance of the buck-boost converters may degrade due to the nonlinear phenomenon, such as Neimark–Sacker bifurcation, period doubling bifurcation, even chaos. In this article, a method to suppress the bifurcation and improve system stability through improving the control principle is indicated. By changing the control principle of the conventional one-cycle control (OCC), the proposed one-cycle energy balance control method achieves the one cycle control by keeping the energy balance of the circuit in each switching cycle. Then the poles of system transfer function are adjusted and the parameter stability range is extended, which achieve the objective of suppressing the bifurcation. Furthermore, such adjustments do not increase the order of the transfer function, thus there is no increase in the computational complexity. Compared with the conventional OCC method, the theoretical analysis based on the sampled-data model demonstrates the ability of the proposed method to suppress the bifurcation and extend the parameter range. Further simulation and experimental results also validate the theoretical analysis.

FPGA collaborated one cycle control method in VSC for standalone self-excited induction generator

The building up of voltage in the three‐phase self‐excited induction generator (SEIG) is created by the residual magnetic-flux or excitation-capacitors. The frequency as well as voltage of the SEIG is reliant to the excitation-capacitors, prime mover speed, magnetization characteristics, and loads. Generally, the electrical loads are continuously changing, with respect to the prime mover speed. Commonly, in SEIG the speed control regulators are used regulate prime movers. On the other hand, this method is equally expensive besides, unable deal transient epochs. There are control methods have been literature for frequency and voltage control regulations of SEIG. The SRF and IRP methods are very attractive method to deal these cases of transient periods. However, these methods are influenced when the reactive power variation fails on one occasion stator is not pay compensation with load. Henceforward, an alternate method is recommended using a one-cycle control (OCC) for voltage-source converter (VSC) connected with DC link chopper (DC-Side), which keeps better frequency and voltage regulation of SEGI. Field programmable gate array (FPGA) digital implementation for power electronics claims has revealed an emergent interest of many electrical researchers. Intellectual property (IP) cores are the essential technology, since the power electronics controllers demands higher end pulse width modulation and controller design in power electronic applications assertions. In this paper the experimental investigation of OCC supports SEIG to cope up requirement to connected standalone load. The system is an analyzed for different frequency control study. In this study, the complete OCC and outside system loops are employed in Xilinx system generator collaborated Spartan FPGA-3A board.

Stability analysis of DC-DC converters with energy balance control

With variation of parameters, DC-DC converters may change from stable state to an unstable state, which degrades the performances of the converter system severely. In this article, by establishing the state-space average model, the stability and bifurcation of a boost and a buck-boost converter with the energy balance control (EBC) is studied, respectively. Then the stability boundary and stable parameter domains are accurately predicted. The obtained stability region provides parameter regulating range for converter design. Furthermore, compared with the one-cycle control (OCC) method, the EBC possesses an extended stable parameter domain, which avoiding the unstable behaviors such as Hopf bifurcation, Quasi-periodic Oscillation even chaos, etc. The theoretic analysis is well validated though simulation and experiment.

Improved and accurate low‐frequency average modelling and control of a conventional power factor correction boost converter in continuous conduction mode

When dealing with power factor correction (PFC) rectifiers that require the use of high filter capacitances, conventional small-signal modelling techniques are not capable of reproducing the converter behaviour accurately owing to the impact of the low-frequency dynamics on the system. In this context, this work presents an improved modelling technique applied to a conventional PFC boost converter operating in continuous conduction mode (CCM). The proposed approach leads to a more accurate analysis than the traditional modelling developed for dc–dc converters, which is often extended to rectifiers. It consists of a fast and concise solution for the implementation of several PFC techniques from the derived transfer functions. The introduced method is described aiming at the development of a boost-based PFC stage using the well-known one-cycle control technique (OCC). Simulation and experimental results are presented and thoroughly discussed to validate the theoretical assumptions.

One Cycle Control of a PWM Rectifier a New Approach

This paper analyzes a Digital Signal Processor (DSP) based One Cycle Control (OCC) strategy for a Power Factor Corrector (PFC) rectifier with Common-mode Voltage (CMV) immunity. It is proposed a strategy that utilizes an emulated-resistance-controller in closed-loop configuration to set the dc-link voltage to achieve unity power factor (UPF). It is shown that if the PFC can achieve UPF condition and if the phase voltage is only affected by CMV, then phase current is free from CMV, as well as a lead-lag compensator (LLC) to average phase current.

Simulations and experimental validation of one cycle controlled nine-level inverter using FPGA

This paper presents an extensive simulation-based and experimental validation of One-Cycle Control (OCC) over a nine-level power inverter using Cyclone III FPGA from Intel. OCC is a technique that exploits the nonlinear nature of multilevel power converters to overcome issues such as fast dynamic response, robustness and perturbations on either the source or the load side. Simulations performed in Modelsim demonstrate the elimination of dynamic and steady-state error between the switched output and reference signals on application of OCC. Simulink-based development and testing of the multilevel inverter model is also carried out under varying load conditions to record the reference signal, current, power factor and total harmonic distortion. The applied control scheme exhibits negligible current distortion and instability concerns when the converter is lightly loaded. Altera Quarturs II is further used for the VHDL-based implementation and experimental testing of the developed algorithm thus, validating the robustness of the control strategy.

Soft-Switching Technology of Three-Phase Six-Switch PFC Rectifier

An active clamp, three-phase, six-switch power factor correction rectifier with a one-cycle controller is proposed, which can effectively suppress the reverse recovery of the reverse parallel diode of the bridge arm switch and reduce the reverse recovery loss. The main switches and auxiliary switch are both zero-voltage switches. It works in a fixed switching frequency and low power stress during the switching period. The specific working process and control circuit are analyzed in detail, and the model simulation is carried out. The experimental platform of a 2.5 KW prototype, with a complete test and verification of the soft switch technology proposed in this paper, was set up in the laboratory.

Stability Enhancement of One-Cycle Controlled Buck-Boost Converters With a Composite Function Embedded

Rich non-linear phenomena, such as Neimark-Sacker bifurcation and chaos and so on, are proven to exist and cause instability in one-cycle controlled (OCC) buck-boost converters. This paper presents a composite function embedded method based one-cycle control (CFOCC) to resolve such problems. By modifying the conventional OCC through embedding a composite function, the non-linear stability performances of the system are considerably improved to avoid bifurcation phenomena and the stable region is enlarged. Further, various commonly used functions, such as the logarithmic function, the arc-tangent function, etc., can be used as the embedded composite functions. The effectiveness of the proposed control method is verified by simulation and experiment.

Effect of Modal Interaction on Transient Behavior in Double-Input SEPIC DC–DC Converters

In this paper, we exploit an idea of nonlinear modal series method to investigate the effects of modal interaction in the one-cycle controlled (OCC) double-input SEPIC DC–DC converter. Based on the proposed nonlinear averaged model, the analytical approximate solutions are obtained to characterize the dynamic response characteristic of the transient behaviors in the double-input SEPIC converters. The fundamental modal analysis is utilized to identify the dominant oscillation modes and discover the relationship between parameters, fundamental modes and state variables. Furthermore, the second-order interaction indices are proposed to uncover the underlying mechanism of nonlinear interaction behaviors. In particular, the correlation between parameters and modal interaction are derived to optimize the transient process of the double-input SEPIC converters. Finally, numerical simulations are performed to verify the theoretical analysis.

Derivation of OCC Modulator for Grid-Tied Single-Stage Buck-Boost Inverter Operating in the Discontinuous Conduction Mode

This paper is concerned with the derivation of a one-cycle controller for driving a single-stage buck-boost DC-AC micro-inverter in grid-tied applications. The topology under study is based on a full-bridge switch arrangement with no unfolder circuit. The proposed micro-inverter attains a high gain by applying a multi-winding tapped inductor and, therefore, can operate at grid-level voltage without using a DC-DC step-up stage. To minimize the switching loss, the proposed inverter is operated in the discontinuous conduction mode. The operation principles of the proposed topology in the discontinuous conduction mode are discussed and analyzed. Based on the analysis, the one-cycle control law and modulator circuitry needed to control the proposed micro-inverter are developed. The feasibility of the proposed modulation scheme is verified by simulation.

Enhanced One-Cycle Control for Multicell Power Converters

In this article, we propose an enhanced one-cycle control (EOCC) strategy for high-voltage gain multicell converters, aiming to resolve the existing issues that exist in the conventional one-cycle control techniques, such as intolerance to load disturbances and inapplicability to multicell converters. The proposed EOCC method is able to overcome these limitations while effectively suppressing input voltage fluctuations and having great responsiveness. Simulation and experimentation on an improved four-cell switched inductor with the proposed EOCC are conducted, which agree well with the theoretical analyses and demonstrate a range of favorable features of the EOCC method, revealing its great feasibility and wide applicability.

Voltage Balancing Control of Cascaded Single-Phase VIENNA Converter Based on One Cycle Control With Unbalanced Loads

A research study on a type of cascaded single-phase VIENNA converter (CSVC) is presented in this paper. And a type of DC voltage balancing control strategy for each cascaded module of the CSVC based on improved one-cycle control (I-OCC) is proposed, in which voltage balancing signals are added to the conventional OCC (C-OCC) control loop to cause a difference in the modulation signals of each of the cascaded modules, so that the DC voltages of all modules can be quickly balanced under unbalanced loads. At the same time, the average modulation wave maintains a constant value so that the CSVC achieves a unity power factor operation. The operating principle of the I-OCC strategy is discussed in detail, and the corresponding mathematical relationships are derived. In the proposed strategy, the ability to adjust the DC voltages is also analyzed. Finally, the simulation and experiment results are provided to verify the validity and feasibility of this I-OCC-based voltage balancing control strategy. The control strategy proposed by this paper is also applicable to all other cascaded unidirectional rectifiers.

Stability and Evolutionary Trend of Hopf Bifurcations in Double-Input SEPIC DC–DC Converters

In this paper, the stability and evolutionary trend of Hopf bifurcations are investigated thoroughly for the double-input SEPIC DC–DC converter with one-cycle control (OCC), which is widely used in hybrid power systems. By means of cycle-by-cycle simulations, the evolutionary trend of bifurcation behaviors is identified. The inherent mechanisms of two types of bidirectional Hopf bifurcations are uncovered based on the proposed averaged model. Moreover, stability boundaries in the parameter space are derived with the help of eigenvalue analysis to optimize the circuit design. Furthermore, some important indices with respect to coupling effects are evaluated to assess the coupling effects in the system. Finally, PSpice circuit experiments are performed to verify the bifurcation analysis.

A Feedback-Based Passive Islanding Detection Technique for One-Cycle-Controlled Single-Phase Inverter Used in Photovoltaic Systems

Single-stage, single-phase photovoltaic (PV) distributed generation (DG) systems rated below 5 kW are becoming popular because of the reduction in the cost of PV panels and also due to various policy initiatives. One cycle control (OCC) based inverters are ideally suitable for such DG systems because of its cost-effectiveness, simple structure, and phase-locked loop free implementation. These inverter-based DG systems should have a robust islanding detection method (IDM) incorporated into it and should fulfill the recent standard requirements. This article proposes a novel feedback-based passive IDM, which is suitable for OCC-based grid-connected PV inverter system. The proposed method relies on the inbuilt feedback nature of OCC-based system, which drives the voltage at the point of common coupling outside the normal range of operation during an islanding condition. The proposed IDM works effectively under the new standard requirements with negligible nondetection zone. The IDM does not rely on additional computational effort or injection of external disturbance into the grid. Simulation studies are performed to verify the effectiveness of the proposed IDM. A laboratory prototype has been developed, and experimental studies are conducted to ascertain the viability of the proposed method.

A Modified One-Cycle Control for Vienna Rectifiers with Functionality of Input Power Factor Regulation and Input Current Distortion Mitigation

In this paper, aiming at incorporating reactive power compensation functionality into the Vienna rectifiers, a modified one-cycle-control (MOCC) strategy is proposed by which the three-phase Vienna rectifier can be regulated in leading, lagging or unity power factors with near-sinusoidal input current waveform. First, a brief review of the working principle of the conventional OCC (COCC) strategy is conducted. Then, the MOCC strategy with the functionality of input current phase-shift control is discussed in detail. To mitigate input current distortion caused by the current phase-shift, a method whereby the signal of one phase current which is flowing in an uncontrollable region is injected into the other two phases’ current command signals is further presented. The constraints to the implementation of the MOCC scheme and the reactive power compensation capacity of the rectifier under MOCC control are analyzed as well. The proposed MOCC strategy is as easy to implement as the COCC strategy. Moreover, the MOCC strategy also preserves all other advantages of the COCC strategy, such as no phase-locked loop, no frame transformation and constant switching frequency. Finally, the theoretical analysis of the proposed MOCC strategy is fully verified by simulation and experimental results from a 1 kV·A three-phase Vienna rectifier prototype.