Power Management Using One Cycle Control Strategy for Triple Input Single Output Fly Back DC–DC Converter

In voltage‐controlled voltage source inverters (VSIs)‐based microgrids (MGs), the inner control is of prime interest task for guaranteeing safe and stable operation. In this paper, an in‐depth investigation of the modelling, control design, and analysis of the voltage and current inner control loops intended for single‐phase voltage‐controlled VSIs is established. The main objective of this work is to provide a comprehensive study of the mathematical modelling, control design, and performance evaluation of the inner control's loops considering different proportional‐integral (PI) controller types with and without compensation, and to determine the optimal scheme that can offer better performance in terms of implementation simplicity, robustness, and transient and steady‐state responses. Thus, the mathematical closed‐loop models of designed outer voltage and inner current control schemes based on PI, P, and feedforward controllers with and without compensation are, first, derived. Following this, a systematic and effective control design for tuning the different PI controllers’ parameters is proposed. Furthermore, an analysis revealing the performance of the designed voltage and current control schemes is provided. This analysis enables us to choose a P controller and PI feedforward controller for the current control loop and the voltage control loop, respectively. The chosen P and PI controllers should be simple; meanwhile, they should offer a wide bandwidth. A simulation study is carried out in MATLAB/Simulink software to assess the performance of the adopted inner control scheme for both linear and non‐linear loads. In addition, an experimental setup, based on a TMS320F2837xD μ C, of a single‐phase VSI supplying linear and non‐linear loads is built to verify the effectiveness and the robustness of the adopted inner controller. The results demonstrated: (1) the necessity of introducing the compensation term, which is responsible for offering control improvement against voltage perturbation, (2) the high tracking performance of the chosen controller in terms of dynamic and steady‐state responses as well as its simplicity of implementation.

Performance evaluation of isolated three-phase voltage source inverter with LC filter adopting different MPC methods under various types of load

This paper presents a novel current mode control technique using an Adaptive Neuro Fuzzy Inference system (ANFIS) for single phase power factor correction (PFC) with DC- DC Single Ended Primary Inductance converter (SEPIC). The proposed system uses cascade control strategy which comprises of outer voltage PI controller and an inner current controller. The outer PI controller coefficients are determined by appropriate tuning and inner current control is implemented with AnFIS. The performance of the proposed system is analysed using Matlab/Simulink based simulation studies. In order to ensure the robustness of the proposed controller the performance parameters such as Percentage Total Harmonic Distortion(%THD), Power factor (PF),%Voltage regulation, %Efficiency are analyzed. From the simulation results, it is inferred that the proposed method provides efficient tracking of output voltage and source current for step load, set point and line variations.

To realize accurate current control for a boost converter, a precise measurement of the inductor current is required to achieve high resolution current regulating. Current sensors are widely used to measure the inductor current. However, the current sensors and their processing circuits significantly contribute extra hardware cost, delay and noise to the system. They can also harm the system reliability. Therefore, current sensorless control techniques can bring cost effective and reliable solutions for various boost converter applications. According to the derived accurate model, which contains a number of parasitics, the boost converter is a nonlinear system. An Extended Kalman Filter (EKF) is proposed for inductor current estimation and output voltage filtering. With this approach, the system can have the same advantages as sensored current control mode. To implement EKF, the load value is necessary. However, the load may vary from time to time. This can lead to errors of current estimation and filtered output voltage. To solve this issue, a load variation elimination effect elimination (LVEE) module is added. In addition, a predictive average current controller is used to regulate the current. Compared with conventional voltage controlled system, the transient response is greatly improved since it only takes two switching cycles for the current to reach its reference. Finally, experimental results are presented to verify the stable operation and output tracking capability for large-signal transients of the proposed algorithm.

Microgrids are distributed generation structures that link groups of Distributed Generators (DGs) to either connect to the utility grid, or to operate as a standalone (islanded) system. However, the injected power from each DG must be carefully controlled to ensure reliable power distribution, balanced modular operation, and regulated voltages across the microgrid. It is commonly accepted that DG units cannot operate in current-control mode when islanded, because there is no stiff grid voltage available. Consequently they are usually operated in voltage control mode, with individual droop controllers regulating the inverter voltage magnitude and frequency to share active and reactive power. This paper presents a new approach to operate islanded microgrid DG units in current control mode, by combining linear current regulators with predictive voltage control. The result achieves a rapid load response while still maintaining well regulated voltage levels. A current magnitude droop controller is also proposed to maintain equal power sharing between the current controlled DG units.

The conventional one cycle control cannot realize the function of eliminating harmonic component in the output voltage waveform of a cascaded multilevel inverter. To overcome these problems, this paper proposes a modified one cycle control(OCC) scheme based on a sample time staggered technique. Through the stagger of the sample time in the control system of cascaded units, the output voltage waveform of the cascaded multilevel inverter controlled with the modified OCC is synthesized by the voltage waveforms of each unit. Then, specified harmonic components of the output voltage waveform can be eliminated. Furthermore, the modified OCC produces superior ability of suppressing the disturbances in the dc sources. The simulation results verify the feasibility of the modified one cycle control in cascaded multilevel inverters in comparison with phase shifted PWM.

On remote islands photovoltaic (PV) panels with battery energy storage systems (BESSs) supply electric power to customers in parallel operation with engine generators (EGs) to reduce fuel consumption and environmental burden. A BESS operates in voltage control mode when it supplies power to loads alone, while it operates in current control mode when it supplies power to loads in parallel with the EG. This paper proposes a smooth mode change of the BESS from current control to voltage control by using initial value at the output of integral part in the voltage controller, and a smooth mode change from voltage control to current control by tracking the EG output voltage to the BESS output voltage using a phase-locked loop (PLL). The feasibility of the proposed scheme was verified through computer simulations and experiments with a scaled prototype.

This paper presents implementation issues of a digital control system applied to a power factor correction (PFC) boost converter rated to a wide range of output power, operating in mixed conduction mode (MCM). The digital control system comprises an input current controller and an output voltage controller. The current controller is formed by two predictive model-based control laws, while the output voltage is regulated through a proportional-integral controller. The implementation requirements of this control system and the executed programming routines, highlighting the inductor current sampling process in different conduction modes are discussed. Experimental results applying a low cost microcontroller are shown to validate the operation of the current and voltage controllers.

The conventional one-cycle control (OCC) technique requires the integrator to reset instantaneously. However, it is very difficult to realize by hardware due to the finite time constant of a reset circuitry, which loads to a large DC offset in the output voltage. Therefore, the paper presents a new control scheme to resolve the problem, which is based on considering a singlephase full-bridge inverter as a buck converter in either positive or negative half load-cycle. Then the amplitude and frequency of the output voltage can be adjusted effectively. Furthermore, by using the dual-buck modulation, the inverter keeps one pair of switches shut during a half load-cycle, which reduces switching loss compared with that of the traditional OCC and avoids a waveform distortion brought by adding dead time. Through theoretical analysis and simulation comparison, it is verified that the half load-cycle OCC can solve the problem of DC offset in the output voltage of the inverter using traditional OCC, while the advantages of the OCC such as constant switching frequency, no multipliers, and simple circuitry are preserved.

A new large-signal nonlinear control technique is proposed to control the duty-ratio d of a switch such that in each cycle the average value of a switched variable of the switching converter is exactly equal to or proportional to the control reference in the steady-state or in a transient. One-cycle control rejects power source perturbations in one switching cycle; the average value of the switched variable follows the dynamic reference in one switching cycle; and the controller corrects switching errors in one switching cycle. There is no steady-state error nor dynamic error between the control reference and the average value of the switched variable. Experiments with a constant frequency buck converter have demonstrated the robustness of the control method and verified the theoretical predictions. This new control method is very general and applicable to all types of pulse-width-modulated, resonant-based, or soft-switched switching converters for either voltage or current control in continuous or discontinuous conduction mode. Furthermore, it can be used to control any physical variable or abstract signal that is in the form of a switched variable or can be converted to the form of a switched variable.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

One Cycle Control (OCC) is a non-linear switching strategy, which has the advantage of fast dynamic response and disturbance rejection. However, in spite of its several advantages, OCC has some limitations, such as finite reset time, dependency on integration accuracy etc. One typical limitation of OCC is that the output voltage may have a steady state error with respect to the reference. This paper addresses this issue, and proposes a simple and cost-effective solution for eliminating such steady state errors. This technique does not use any current sensor, works on only voltage sensing, and is effective over the entire load range of the converter. The technique is analyzed, a design method is proposed, and then the design is validated through simulation and experiments. The results prove the effectiveness of this strategy.

The distortion produced in the voltage waveform of the inverter hinders its operation at high power. To overcome this issue, this paper presents the modeling of the nine-level quadruple boost (NLQB) inverter and closed-loop control of the same using a proportional-integral (PI) controller. The single DCsourced NLQB inverter uses 10 insulated gate bipolar transistor switches and two switched capacitors. A cascaded PI controller is designed (for voltage and current control) in the aforementioned NLQB inverter to maintain its output voltage at a desirable level. Further, the performance of this inverter after employing a PI controller is studied with harmonic analysis using a fast Fourier transform. Compared with the open-loop operation of this NLQB inverter, the suggested cascaded PI-based closed-loop system produces lesser harmonics and total harmonic distortion.

Dynamic Voltage Restorer (DVR) is one of the most efficient and economical series connected custom power device having a major application in Power Quality Enhancement at consumer and distribution level. In the control structure, the DVR usually utilizes rotating reference frame, which comes with certain downsides. Main purpose of this study is to execute a performance analysis on both rotating and stationary reference frame based DVR's. Cascaded controllers with an outer voltage controller and an inner current controller have been used as control strategy. As current controllers, both Proportional Integral (PI) and Vector Proportional Integral (VPI) controllers are used separately to compare their performance using MATLAB/Simulink. This comparative analysis has been carried out by considering settling time, overshoot and error signals for linear as well as non-linear loads while taking the computational time delays into account.

Front-end power converters for satellite application demand better performance in terms of accurate reference tracking because of the wide-range input voltage of the solar panels. The very tight output voltage requirements demand for robust, reliable, and higher efficiency. The control of such converter is very complex and time consuming to design. Two commonly used control modes are current and voltage control. The design and implementation of a voltage controller for power converter is simpler but not do provide for overcurrent protection compared to current mode controller.

In this paper, a control strategy for a distributed generation (DG) unit that provides a seamless transition between grid connected mode and islanded mode is presented. Instead of switching between current control and voltage control modes as commonly proposed in the literature, a voltage control mode is used in both grid connected and standalone modes. The output voltage and frequency are controlled to regulate the reactive and real power injected into the grid, respectively. In the islanded mode, the output voltage and frequency of the DG unit are regulated at their nominal values. Therefore, transition between operation modes is achieved by switching the voltage and frequency references of the same voltage controller. When the grid is interrupted, the DG unit supplies only the load automatically with no abrupt transients in the local load voltage and current, even before the islanding is detected. The principle and implementation of the control strategy to detect the grid conditions and islanding, and to switch seamlessly between the two operating modes are developed. The control strategy is validated through simulations using a detailed switching models in the PSCAD/EMTDC environment.