Flyback Inverter Research Articles

Synchronization of Phase and Frequency in Flyback Inverter Using a New Ripple Hysteresis Controller

Synchronization of Phase and Frequency in Flyback Inverter Using a New Ripple Hysteresis Controller

Discontinuous Modulation Technique for Isolated Three-Phase Grid-Connected Flyback Inverter with Selective Harmonic Compensation for PV and Fuel Cell Systems

Discontinuous Modulation Technique for Isolated Three-Phase Grid-Connected Flyback Inverter with Selective Harmonic Compensation for PV and Fuel Cell Systems

Single Stage Grid-Connected Flyback Inverter with Optimal PID Controller for Harmonic Distortion Analysis

Single Stage Grid-Connected Flyback Inverter with Optimal PID Controller for Harmonic Distortion Analysis

A simple and highly efficient flyback inverter control strategy for AC module application

A simple and efficient control structure of a flyback converter is proposed in this paper considering its intrinsic dynamic characteristics. The proposed control strategy makes use of a PI controller with a low pass filter to overcome the limitations on determining the gains of the feedback control system result from the right-half-plane (RHP) zero and LC filter dynamics. Therefore, the target output current is properly tracked and the disturbances are attenuated by the proposed control system. Furthermore, the stability requirements are satisfied and a zero steady-state error is obtained by appropriately regulating the control signal. This control method is very fast applying the minimum number of delays in its scheme which causes the computational burden to be significantly reduced. Finally, the theoretical claims are confirmed by simulation and experimental results on a 200-W laboratory prototype.

In depth mathematical-analysis and experimentation of high-power SiC-FET based single-stage three-phase differential-based flyback inverter with practical design issues for grid-tied applications

This paper presents a detailed mathematical loss-modelling, design, hardware implementation issues, and experimental verification of high-power isolated single-stage three-phase differential-based flyback inverter (DBFI) for grid-tied photovoltaic applications. In addition, this paper studies the loss-modelling analysis of the DBFI components in terms of time and system parameters, which describes the power loss distribution over the circuit components for efficiency enhancement possibility. Also, it studies the practical design issues of DBFI; power stage design, HFT-based F3CC Nano-Crystalline C-Core design, passive elements selection effects on harmonics compensation of grid current waveforms, and the input DC current ripple for PV applications propriety. In addition, the input DC-voltage variation impact on the grid-current THD, system efficiency, and operational power factor are investigated. Also, continuous modulation scheme (CMS) is used to control the proposed DBFI for low-order harmonic components mitigation. The system is simulated by PSIM computer-aided simulator. Then, the proposed system is verified experimentally using a laboratory prototype controlled by TMS320C6713 DSP controller.

Design and analysis of a novel adaptive learning control scheme for performance promotion of grid-connected PV systems

This paper addresses a hybrid adaptive iterative learning control strategy for controlling power converters that are used in photovoltaic systems to enhance maximum power point tracking capability in the presence of variable atmospheric conditions. The adaptation of the controller to the fast-changing environmental conditions is provided by a fractional-order proportional-integral type learning control mechanism. The developed control scheme is integrated into a grid-connected current-source flyback inverter to highlight the improvements in performance criteria such as convergence speed during transients, tracking accuracy, steady-state oscillations, and robustness. The performance analyses are carried out under various scenarios. The obtained results reveal that the dynamic response of the system is considerably increased under erratic atmospheric conditions while steady-state oscillations are decreased for stable operation conditions. The maximum absolute error that indicates the robustness of the proposed controller is decreased from 2.3704 to 2.1920. In addition, the error deviations of the proposed control algorithm are below 10%. The variance of the error, which shows steady-state stability, is reduced from 2.5123 to 1.6152. Also, the proposed controller reduces the amount of control energy by 20% when compared to the PI controller. Furthermore, the values of IAE and ISE are reported 10% lower in the proposed controller.

A novel algorithm of MGWO-based PI controller for a single-stage grid-connected flyback inverter with ZVS

An effective approach on zero-voltage switching scheme for a single-stage grid-connected flyback inverter along with the introduction of Modified Grey Wolf Optimizer technique based on the proportional integral controller is proposed. A focus on soft-switching is attained by means of permitting the grid-side negative current along the bidirectional switches held in the transformer’s secondary side. Consequently, there is a discharge of metal–oxide–semiconductor field-effect transistor’s output capacitor. This function led the primary switch to turn ON at the condition of zero voltage. Therefore, it is essential to optimize the reactive current level for attaining zero-voltage switching. Generally, the basic Grey Wolf Optimization has some more disadvantages of accuracy-solving and less capability of finding the fitness solutions. Hence, to overcome this, optimizer can be modified for further enhancement in the optimization process. Modified Grey Wolf Optimizer based on the proportional integral controller with pulse width modulation technique is used for controlling the switches; thereby zero-voltage switching triggering takes place which results in decreased total harmonic distortion. Finally, the simulations can be carried out based on the total harmonic distortion which helps to illustrate the effectiveness of the suggested algorithm. A 24-V, 325-W prototype has been carried out to verify the proposed system.

Analysis and Simulation of Current-source Flyback Inverter with Efficient BCM Control Strategy

The Flyback inverter is a single-stage power inverter which represent an attractive solution for photovoltaic (PV) grid-tied inverter application. The main advantages of a current-source flyback inverter are high power density and high efficiency due to its small, as well as low total harmonic distortion (THD) operation. However, a flyback topology works with Discontinuous Conduction Mode (DCM) control strategy has lower efficiency and poor THD values. In this paper, an efficient current-source flyback inverter topology works with Boundary Conduction Mode (BCM) control strategy is presented. Besides, an efficient incremental conductance (IC) maximum power point tracking (MPPT) is used to extract the maximum power from the PV module. To verify the proposed control a power simulator (PSIM) software is used. As a result, the simulation results indicates that the BCM control is more efficient than the DCM method for various weather conditions. Finally, the proposed BCM strategy is compared with DCM control in terms of THD and thus it is achieved lower THD contain in the injection current of grid.

LCL filter design for grid-connected single-phase flyback microinverter: a step by step guide

<span lang="EN-US">Recently, <em>LCL</em> has become amongst the most attractive filter used for grid-connected flyback inverters. Nonetheless, the switching of power devices in the inverter configuration creates harmonics that affect the end application behavior and might shorten its lifetime. Furthermore, the resonance frequencies produced by the <em>LCL</em> network contribute to the system instability. This paper proposes a step-by-step guide to designing an <em>LCL</em> filter by considering several key aspects such as the resonance frequency and maximum current ripple. A single-phase grid-connected flyback microinverter with an <em>LCL</em> filter was designed then constructed in the MATLAB/Simulink environment. Several different parameter variations and damping solutions were used to analyze the performance of the circuit. The simulation result shows a promising total harmonic distortion (THD) value below 5% and harmonic suppression up to 14%.</span>

Three-Phase PWM Inverter for Isolated Grid-Connected Renewable Energy Applications

This paper proposes a three-phase isolated flyback inverter (IFBI) for single-stage grid-tied solar PV applications, considering a simple sinusoidal pulse-width modulation (SPWM) scheme. The proposed single-stage inverter employs a reduced passive elements count by considering three input-parallel output-differential (IPOD) flyback converter modules. Additionally, a single small size LC-input low-pass filter is utilized at the input paralleling point for ripple-free input current operation, which is essential in grid-connected renewable energy applications. In addition, a mathematical model of the IFBI is presented to confirm the existence of its low-order harmonic components. A simple PI controller-based control scheme, considering only two loops and five sensors, is used to control the proposed grid-tied IFBI. Continuous modulation scheme (CMS) combined with SPWM is used to diminish the low-frequency harmonic components. Moreover, a simple selective harmonic elimination (SHE) loop is used for second-order harmonic components (SOHC) elimination from grid-injected currents. The SHE has decreased the SOHC from 43% to 0.96%, which improves the grid current THD from 39% to 3.65%, to follow the IEEE harmonic standard limits. Additionally, the harmonic elimination technique decreases the circulating power between the inverter paralleled modules, which enhances the grid currents power factor. The proposed inverter is verified through a grid-connected 200 V, 1.6 kW, 60 Hz experimental prototype, and the switching frequency is 50 kHz. TMS-based DSP controller is used to control the grid-injected power to follow the reference power set-point.

An Efficient Grid-tied Flyback Micro-inverter with DCM Control Strategy

In two-stage micro-inverter photovoltaic (PV) applications, DC/DC converter is used to obtain the highest DC power from the PV module. In this type of inverter, the rising of voltage from the PV module to a grid voltage level is limited to a certain value. Moreover, the absence of the isolation between the input and output makes it is less efficient. For these reasons, an efficient single-stage grid-tied flyback PV micro-inverter with discontinuous conduction mode (DCM) control strategy is proposed to feed an alternating current (AC) to the main grid with a lower value of the total harmonic distortion (THD). The control strategy is based on a sine sinusoidal pulse width modulation (SPWM) technique to control the main switch of flyback inverter. Also, a simple perturb and observe (P&O) maximum power point tracking (MPPT) technique has been presented to obtain the MPP point from the PV module for any environmental conditions. The proposed control was verified using PSIM software and simulation results is obtained. The proposed control is tested under different weather conditions for solar irradiance and temperature, as a result, a pure sin wave current has been injected into the grid with a lower harmonics value. Finally, the small size, low cost and high reliability of single stage flyback micro-inverter is presented without the need for DC/DC converter.

Interleaved high power improved two-stage flyback inverter for photovoltaic applications

The interleaved flyback converter is used to increase the power level and decrease the current ripple, Harmonics, passive component size, and total cost. The topology of flyback is used for lower output power in micro inverters. The flyback converter in this paper is designed for high output power. The grid is developed based on the interleaved topology of flyback converter, which is connected to central type photovoltaic inverter. The principles of the converter operation are discussed in detail. In MATLAB software the designed converter is simulated. Dual-stage flyback converter interleaving is being investigated for flyback inverter design rated at 01KW. The conversion system is run in DCM, providing a quick, easy to monitor dynamic response and no losses due to switchover action. As 90.16 percent, 3.9 percent and 0.998, the proposed efficiency of flyback inverter, total harmonic distortion, and the power factor were calculated.

Performance optimisation of the grid‐connected flyback inverter under improved hybrid conduction mode

In the unfolding-type interleaved two-switch flyback inverter (ILTFI) operating in discontinuous conduction mode (DCM), the hybrid control strategy combining the one-phase DCM and the two-phase DCM has a significant impact on improving the efficiency under all load conditions. In the situation where the marginal power of this control strategy is increased, the converter may enter CCM. Consequently, the converter cannot track the reference current and the output current quality is notably decreased. To tackle this issue, a novel hybrid control method is proposed which varies the switching frequency based on the output power. The proposed approach is immune to the loss analysis and power losses of the components. Hence, it is independent of components selection and their characteristics. In this case, the smooth transition between the one-phase and the two-phase operation modes is guaranteed without affecting the output power quality and the stability of the converter in DCM. The control complexity of the proposed scheme is low and the converter can be easily controlled in DCM. The performance of the flyback microinverter with the proposed hybrid control scheme is verified by the simulation and the experimental results together with the loss analysis.

Bidirectional Operation Scheme of Grid-Tied Zeta Inverter for Energy Storage Systems

The zeta inverter has been used for single-phase grid-tied applications. For its use of energy storage systems, this paper proposes the bidirectional operation scheme of the grid-tied zeta inverter. A shoot-through switching state is introduced, providing reliable bidirectional operation modes. A shoot-through duty cycle is utilized for the bidirectional grid current control of the inverter. The grid current is bidirectionally controlled by the shoot-through duty cycle, which enables the inverter to operate with seamless change of operation modes. Over the state-of-the art techniques using flyback and Cuk inverter topologies, the grid-tied zeta inverter using the proposed operation scheme provides advantages of high efficiency, low cost, and high reliability. The operation principle is presented by describing the operation mode and control method for the grid-tied zeta inverter. A 500 W prototype has been built and tested to verify its operation principle.

An Active-Clamp Forward Inverter Featuring Soft Switching and Electrical Isolation

Traditional photovoltaic (PV) grid-connection inverters with sinusoidal pulse-width modulation (SPWM) control suffer the problem of buck-typed conversion. Additional line-frequency transformers or boost converters are required to step-up output voltage, leading to low system efficiency and high circuit complexity. Therefore, many flyback inverters with electrical isolation have been proposed by adopting a flyback converter to generate a rectified sine wave, and then connecting with a bridge unfolder to control polarity. However, all energy of a flyback inverter must be temporarily stored in the magnetizing inductor of transformer so that the efficiency and the out power are limited. This paper presents a high-efficiency active-clamp forward inverter with the features of zero-voltage switching (ZVS) and electrical isolation. The proposed inverter circuit is formed by adopting a forward converter to generate a rectified sine wave, and combining with the active-clamp circuit to reset the residual magnetic flux of the transformer. Due to the boost capability of the transformer, this inverter is suitable for the PV grid-connection power systems with wide input-voltage variation. The operation principles at steady-state are analyzed, and the mathematical equations for circuit design are conducted. Finally, a laboratory prototype is built as an illustration example according to proper analysis and design. Based on the experimental results, the feasibility and satisfactory performance of the proposed inverter circuit are verified.

A Phase-based Control Method to Control Power Flow of a Grid-connected Solar PV through a Single Phase Micro-inverter

This paper presents micro-inverter to regulate power delivery from a small scale solar photovoltaics using a phase-based control technique. The micro-inverter used is a flyback-type inverter. Instead of controlling the voltage magnitude, the proposed control method uses power angle as control parameter to yield maximum power. The phase angle is obtained from MPPT algorithm and then employed as the phase reference for shifting the power angle of sinusoidal signal from PLL block. Several simulation experiments are performed to examine the design. A conventional technique is also presented for comparison. The simulated data shows that the implementation of this phase-based flyback inverter exhibits satisfactory results and hence can be used as an alternative method.

Microinverter for wireless charging

This paper presents a multi stages grid connecting single phase micro-inverter for photo voltaic utilisation. Conventional single switch flyback inverter suffers from high voltage transients across switch, which leads to a significant reduction in efficiency, the stress on the device causes an increase in cooling arrangements and also underutilization of the device as far as the ratings are concerned. The proposed topology will have an additional switch and two clamped diodes at the primary side so as to have a reduction in the switch stress which increases the efficiency. Converter is operated in Discontinuous conduction mode to have a simple control and to avoid the stability issues. Simulation results authenticate the concert of the proposed method.

Soft switching flyback inverter for photovoltaic AC module applications

The soft switching flyback inverters still cannot provide high efficiency and low output current total harmonic distortion (THD) in all load ranges. Therefore, a new flyback inverter with soft switching for photovoltaic AC module applications is presented in this study. The introduced inverter is simple and a small auxiliary circuit is added to the conventional topology of the flyback inverter. Since the primary current of the transformer is not affected by the auxiliary branch, the output current THD does not increase. In addition, all of the high-frequency switches of the proposed topology are switched under soft switching condition, which allows high-switching frequency. Hence, high efficiency, as well as compact design, can be achieved in the proposed inverter. Moreover, the voltage overshoot of the main switch during the turn-off process is limited. This effect decreases the conduction losses because the lower voltage rating switch can be used. Furthermore, a new control method is presented, which provides high efficiency in all load ranges. The operations of the introduced flyback inverter and component selection have been discussed in detail. The performance of the proposed inverter with the auxiliary circuit and corresponding controllers are validated with the help of experimental results.

A novel ANFIS-based MPPT controller for two-switch flyback inverter in photovoltaic systems

Solar energy is recognized as one of the most popular renewable energy sources due to its availability around the world. Because of the intermittent generation of solar power, it is vital to extract the maximum power available from solar panels all day long. For this purpose, Maximum Power Point Tracking (MPPT) techniques are investigated in several papers. In this paper, an Adaptive Neuro-Fuzzy Inference System (ANFIS)-based MPPT controller with just one current sensor has been proposed to achieve that intent. To extract the maximum power from the solar panel, a DC-AC isolated two-switch flyback inverter is connected between the solar panel and the load. To transfer the maximum power to the load, the duty cycle of this converter must be generated with the aid of the proposed ANFIS method. This ANFIS structure takes the voltage and the current of the photovoltaic (PV) module as inputs and generates the maximum power point voltage as the output. Then, with the aid of a fuzzy controller, an appropriate duty cycle will be generated to control the switches of the two-switch flyback inverter. To validate this proposed system, the MATLAB-PSIM co-simulation was done. The results prove that the proposed MPPT controller for a two-switch flyback inverter can track the maximum power under different atmospheric conditions (irradiance and temperature), as well as other advantages from our investigation.

Fault Ride-Through Capability Enhancement for Microinverter Applications

Due to the fast growth of single-phase grid-connected photovoltaic (PV) systems, the existing grid codes are expected to be modified to guarantee the availability, quality, and reliability of the electrical system. Therefore, the future single-phase PV systems should become smarter and support low voltage ride-through (LVRT) capability, which are required for three-phase wind power systems. In this paper, the operation principle of a flyback inverter in a low-voltage ride-through operation is demonstrated in order to map future challenges. The steady state performance of the flyback inverter under voltage rise and drop conditions at boundary conduction mode (BCM) and discontinues conduction mode (DCM) is studied theoretically. The simulation results of the flyback inverter for various grid faults are presented to verify the theoretical analyses. The results indicate the fact that the flyback inverter at BCM condition can provide LVRT capability for photovoltaic microinverter applications in distributed generation (DG) systems, even though it does not need any auxiliary control branches and any limitations in components design.