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This paper proposes a frequency‐control scheme for Doubly Fed Induction Generator (DFIG)‐based (Type‐3) wind turbines to improve the primary‐frequency‐control when the grid power balance is disturbed. The increasing penetration level of renewable energy sources, like wind power plants, reduces the total available inertia of modern grids, which deteriorate the frequency response in case of sudden power‐mismatches. The proposed closed‐loop participation of wind power plant interacts with the thermal units to reduce the frequency nadir and frequency settling‐time, during the inertial and primary stages. The designed disturbance observer decreases the uncertainties in the estimation of grid parameters, which results in robust PI performance in adjusting the ancillary power provided by wind turbines. Certain measures considered within the control loop to limit the rate‐of‐change‐of‐frequency within the permissive range to avoid the protective relays tripping. Comparative simulations studies on modified IEEE 9‐bus and 68‐bus test systems verify the effectiveness and advantages of the proposed method.

To obtain efficient photovoltaic (PV) systems, optimum maximum power point tracking (MPPT) algorithms are inevitable. The efficiency of MPPT algorithms depends on two MPPT parameters, i. e., perturbation amplitude and perturbation period. The optimization of MPPT algorithms affect both the tracking speed and steady-state oscillation. In this paper, optimization methods of MPPT parameters are reviewed and classified into fixed and variable methods. The fixed MPPT parameters are constant during MPPT performance, and a trade-off should be made between the tracking speed and steady-state oscillation. However, the variable MPPT parameters will be changed to improve both the tracking speed and the steady-state oscillations. Moreover, some of them are simulated, compared, and discussed to evaluate the real contributions of the optimization methods to the MPPT efficiency. Furthermore, significant features of the optimization methods, i.e., noise immunity, robustness, and computation effort, are investigated.

Photovoltaic systems have a nonlinear characteristic in which there is one optimum operating point called Maximum Power Point (MPP). However, when PV panels are partially shaded by surrounding objects, there are several MPPs, of which one of them is Global MPP (GMPP). Therefore, conventional Maximum Power Point Tracking (MPPT) algorithms get trapped into local MPPs. As a result, a multitude of Global MPPT (GMPPT) algorithms have been proposed. An outstanding GMPPT algorithm as well as the fast-tracking speed should find GMPP in complicated shading patterns where not only there are lots of MPPs, but also the peaks are close together. Therefore, in this paper, a novel GMPPT based on firework algorithm is proposed which is able to find GMPP in complicated shading patterns with fast tracking speed. Moreover, the firework is combined with Perturb-and-Observe (P&O) algorithm to reduce the computational effort in a way that the firework is only used to recognize GMPP; afterwards, P&O algorithm completes the tracking. Furthermore, the variable sampling time technique, based on the system settling time, speeds up the tracking process considerably. Finally, the proposed method is compared with previous works, simulated, and implemented on an experimental setup to prove its superiority.

In this paper, a new nonisolated interleaved boost topology with ultralarge step voltage ratio based on coupled inductors (CIs) and switched capacitors is proposed. CI applied in the low voltage side along with the interleaved structure and utilizing new topology provide ripple cancelation and considerably reduce the input current ripple and current stress through power switches and magnetic elements. In addition, utilizing CIs in the high voltage side provides a high-voltage gain with an appropriate duty ratio. Voltage lift capacitors used in this structure not only alleviate the voltage spikes across the power switches but also increase the voltage gain. Zero current switching (ZCS) turn-on condition for switches and ZCS turn-off condition for diodes are achieved by employing CIs without any auxiliary circuit. This feature degrades the reverse recovery losses and improves the efficiency of the converter. The voltage stress of the power switches is noticeably lower than the output voltage, especially at high output voltages. Therefore, the low-voltage rated switches can be adopted. This topology provides autocurrent sharing without any controller. Finally, a 600-W, 24-V/480-V laboratory prototype has been built to verify the performance.

In this paper, a new topology to achieve ultrahigh step-up voltage conversion ratio and very low input current ripple is introduced for nonisolated high-power applications by using interleaved structure combined with coupled inductors (CIs) and switched capacitors. Using voltage lift capacitors in this topology not only recycles the energy related to leakage inductance of CIs and alleviates the voltage spike across the power switches but also increases the voltage gain of the converter. Moreover, utilizing CI structure provides zero-current switching (ZCS) turn-on condition for power switches and reducing the diodes reverses recovery losses and also improves the voltage gain of the converter. Using the interleaved structure in the low-voltage side noticeably decreases the input current ripple and current stress through magnetic elements. In addition, utilizing the voltage multiplier cell structure in the high-voltage side provides a high-voltage gain. The voltage stress across the power switches is considerably lower than the output voltage. Hence, the low-voltage-rated switches can be employed. Based on the mentioned advantages, the efficiency of this implementation is improved significantly. Finally, to validate the performance of the proposed converter, a 600-W, 24-V/520-V prototype circuit is implemented.

Wireless charging is widely considered a safe and reliable way for powering biomedical implants, as it avoids problems like surgical infection. Wireless power transfer (WPT) systems are desired to work efficiently against variations in coil–coil distance or output load. On the other hand, to maintain the maximum overall efficiency of the WPT system, the high frequency (HF) power amplifier, used to feed the WPT system, must operate at optimal zero-voltage switching (ZVS) conditions. In this paper, an automated dual-objective control strategy adaptive to variations in coil–coil distance or output load is proposed which ensures both targets of tracking maximum power point and operating at optimal ZVS condition by adjusting operating frequency and duty-cycle of switching voltage of HF power amplifier, respectively; that is while there have been few studies which have addressed both the two targets. To evaluate the effectiveness of the proposed strategy, a PCB prototype, operating at 800 kHz, is fabricated. Experimental results, demonstrating the proposed strategy increases transferred power from 23 mW to about 45 mW, are in good agreement with theoretical predictions. Additionally, while implanting the receiver coil in real biological tissue, experiments show only 2% of degradation in power transfer efficiency as well as no frequency shift.

In this study, a new non-isolated interleaved bidirectional DC-DC converter with a high step voltage ratio based on coupled inductors (CIs) is introduced. The CIs significantly increase the voltage conversion ratio and provide soft-switching conditions for the switches at turn-on instant. Also, employing an interleaved structure combined with the CI in the low-voltage side noticeably reduces the current ripple and this feature has a vital role in the high-power applications. Also, this topology provides auto-current sharing for the two phases of the interleaved structure. The CIs in the high-voltage side, supply a steep gain in both buck and boost modes with an appropriate duty cycle. The proposed method provides zero current switching (ZCS) turn-off condition for all diodes and ZCS turn-on condition for all switches without requiring any auxiliary circuit. So the undesirable reverse recovery effects of diodes are considerably reduced. The proposed converter has the minimum number of switches for two-phase bidirectional structures. Also, a simple passive clamp circuit is proposed for the converter to limit the voltage spikes of CIs. Finally, a 600 W, 30/300 V laboratory prototype is implemented to verify the performance.

Selective harmonic elimination pulse-width modulation (SHEPWM) is a widely adopted method to eliminate harmonics in multilevel inverters, yet solving harmonic amplitude equations is both time consuming and not accurate. This method is applied here for a 7-level cascaded multilevel inverter (CMLI) with erroneous DC sources. To meet the seven harmonic amplitude equations, two notches are applied with the use of higher switching frequency than nominal. These notches can be placed in six different positions in the voltage wave, and each was assessed in a separate manner. In order to solve the equations, a hybrid algorithm composed of genetic algorithm (GA) and Newton–Raphson (N-R) algorithm is applied to achieve faster convergence and maintain the accuracy of stochastic methods. At each step of the modulation index (M), different positions for the notches are compared based on the distortion factor (DF2%) benchmark, and the position with lowest DF2% is selected to train an artificial neural fuzzy interface system (ANFIS). ANFIS will receive the DC sources’ voltages together with required M and will produce one output; thus, eight ANFISs are applied to produce seven firing angles, and the remaining one is to determine which one of the notches’ positions should be used. Software simulations and experimental results confirm the validity of this proposed method. The proposed method achieves THD 8.45% when M is equal to 0.8 and is capable of effectively eliminating all harmonics up to the 19th order.

A new non-isolated high-voltage gain three-port converter for standalone photovoltaic systems is proposed. The magnetic element of this converter is only one coupled inductor. The primary winding of the coupled inductor is shared between battery charger circuit and main converter. Leakage inductance energy of the coupled inductor is either transferred to battery or is regenerated via the passive-clamp circuit. Using switched capacitor and voltage lift techniques, the voltage gain is significantly increased for both low-voltage ports. Single magnetic element, high-voltage gain with reasonable duty cycle, low-voltage stress on the switches, low winding turn ratio of coupled inductor and high efficiency are the merits of this converter. The operation principles and the steady-state analysis are described for the three modes of: single-input single-output, single-input dual-output and dual-input single-output. To verify the theoretical analysis, a laboratory prototype with 28 V input, 48 V battery voltage and 380 V output voltage is implemented and tested.

With the increasing deployment of photovoltaic (PV) sources in the power grid and their contribution to power generation, it is imperative to obtain accurate models for the reliability and stability of these plants. In this paper, a novel method is proposed for reliability assessment for the different structures involved in the implementation of PV plants, in which the failure rate of system components is calculated using the FIDES Guide standard, taking into account environmental conditions such as radiation curves, temperature, and humidity. Failure rates of the insulated gate bipolar transistor and converter capacitor were found to be greater than other components. After precise calculation of failure and repair rates, the probability of functioning in three states of full generation, partial failure, and down was obtained through Monte Carlo simulations. Considering the effect of the system's structure on its stability, the reliability of the system can be increased by adding inverter paths to its structure. Several such structures are proposed, and the most economical design is identified by analyzing load duration curves to obtain the energy loss in each configuration. The proposed algorithm was implemented in Isfahan University's 20 kW PV power plant. Simulations demonstrate the efficiency of the proposed algorithm in design and evaluation of economic system structures.

In this study, a high-performance controller is proposed for single-phase grid-tied energy storage systems (ESSs). To control power factor and current harmonics and manage time-shifting of energy, the ESS is required to have low steady-state error and fast transient response. It is well known that fast controllers often lack the required steady-state accuracy and trade-off is inevitable. A hybrid control system is therefore presented that combines a simple yet fast proportional derivative controller with a repetitive controller which is a type of learning controller with small steady-state error, suitable for applications with periodic grid current harmonic waveforms. This results in an improved system with distortion-free, high power factor grid current. The proposed controller model is developed and design parameters are presented. The stability analysis for the proposed system is provided and the theoretical analysis is verified through stability, transient and steady-state simulations.

High performance grid-tied inverters have stringent control requirements both under steady-state and under transient conditions. Many different control systems have been applied to grid-tied inverters. However, there are few publications reviewing the literature on these control systems and their classification, particularly with regard to recent developments in this area. In this paper, a review of solutions for the control of grid-tied inverters is carried out. These control systems are compared and classified as implementation platform, reference frame, output filter of inverter, control strategy, modulation method, and controller. The major advantages and disadvantages of these parameters are highlighted and compared. Then, the most important characteristics of these parameters have been presented in a table to show which parameters can be used in various control systems for grid-tied inverters.

In this paper, a high-performance control structure is designed, implemented, and applied to a three-phase series–parallel uninterruptible power supply (UPS). This kind of UPS system provides input power factor correction, output voltage conditioning, and high efficiency. The control strategy proposed in this paper is based on voltage control of the parallel converter and current control of the series converter. It is shown that this strategy improves the system operation, specifically resulting in a smoother and more seamless transition between UPS operating modes. The controller in the proposed strategy is based on combination of two control methods with different characteristics and is therefore called a hybrid structure. To enhance the steady-state performance of the UPS and reach fast error convergence, a repetitive controller is used. In addition, to reach a fast transient response required for control of output voltage, a fast deadbeat is used. The stability of this hybrid controller is dis...

In this paper, a rotary electromagnetic microgenerator is analyzed, designed and built. This microgenerator can convert human motions to electrical energy. The small size and use of a pendulum mechanism without gear are two main characteristics of the designed microgenerator. The generator can detect small vibrations and produce electrical energy. The performance of this microgenerator is evaluated by being installed peak-to-peak during normal walking. Also, the maximum harvested electrical energy during normal walking is around 416.6μW. This power is sufficient for many applications.

In photovoltaic (PV) systems, maximum power point tracking (MPPT) techniques are used in order to extract the maximum power from PV panels. So far, different MPPT methods have been presented. In all of these methods, two MPPT parameters, perturbation amplitude $(\Delta \mathbf{D})$ and perturbation period $(T_{p})$, have a great effect on the MPPT efficiency. In this paper, first, the dynamic behavior of PV systems are assessed in both steady and transient states with the use of the small signal model and the simulation. The PV operating point has different behavior in the steady and transient states; therefore, in the proposed method, first, a state of the system is identified. Afterwards based on characteristics of each state which are assessed in the dynamic behavior of the PV system, the MPPT parameters are optimized. $\Delta \mathbf{D}$ is variable and based on the slope of the P-V curve with two different scaling factors; furthermore, the linear and exponential functions are used to determine the variable $T_{p}$ based on an operating state. In order to prove the superiority of the proposed method over the existing methods, the simulations are done in MATLAB/Simulink and PSIM software, and also comparison is conducted between the proposed method and the previous works.

Nonlinear analysis of complex dynamics displayed by current mode dc–dc converter and idea of Lyapunov exponents assignment by ramp compensator in order to control chaotic behavior is proposed in this article. A discrete-time iterative nonlinear mapping model is derived. The occurrence of the complex behaviors of bifurcation and chaos generated by varying the circuit parameters are investigated through numerical analysis and software implementation of the circuit. Next, in order to control bifurcation and chaos in these converters, the ramp compensation method is used. By inserting the ramp compensation parameter in the dynamical equations of the system, these complex behaviors are examined theoretically and numerically as well. It is proved that through this method, the stable period-one operation of the converter can be extended. By evaluating the Lyapunov exponents (LEs) of the system, the impact of the slope on the location of LEs are determined analytically. This leads to a design methodology for control of chaos in this converter based on LEs assignment in desired values by proper selection of compensator slope. By developing an experimental set up, practical results are obtained to confirm the theoretical analysis and simulations.

In this paper, the frequency splitting phenomenon is precisely investigated based on the concept of the maximum power transfer theorem for a two-coil wireless power transfer (WPT) system. Here, unlike the previous studies, in which the analysis were performed by the reflected impedance, the scrutiny is conducted based on the thevenin equivalent impedance. First, the cause of the frequency splitting phenomenon is described using the frequency characteristics of the thevenin impedance and the load power. Second, the splitting equation is derived and the splitting frequencies are calculated through it. Eventually, some methods, that have been used so far to improve the power transfer capability, in the presence of the frequency splitting phenomenon, are mentioned. In addition, using simulation results by MATLAB software, these methods are compared together and the best method is obtained.

This paper proposes a new method based on a Markov model to calculate the reliability of grid-connected photovoltaic (PV) systems. This system is a grid-connected PV system consisting of PV modules, a multiphase DC–DC converter, an inverter, an inverter controller, and an maximum power point tracking (MPPT) controller at University of Isfahan. This system is considered repairable. Also, different levels of operation are considered for the system equipment. Reliability of the PV modules, the multiphase DC–DC converter, and the inverter has been calculated by the Markov model. Finally, the reliability of the entire PV system is calculated by the Markov model. The proposed algorithm is applied to the PV system positioned at University of Isfahan. Simulation results show the applicability of this method for calculating the reliability of grid-connected PV systems.

A hierarchical control structure is proposed for hybrid energy systems (HES) which consist of wind energy system (WES) and energy storage system (ESS). The proposed multilevel control structure consists of four blocks: reference generation and mode select, power balancing, control algorithms, and switching control blocks. A high performance power management strategy is used for the system. Also, the proposed system is analyzed as an active power filter (APF) with ability to control the voltage, to compensate the harmonics, and to deliver active power. The HES is designed with parallel DC coupled structure. Simulation results are shown for verification of the theoretical analysis.

In this paper, a novel algorithm for PD localization in power transformers based on wavelet de-noising technique and energy criterion is proposed. Partial discharge is one of the main failures in power transformers. The localization of which could be very useful for maintenance systems. Acoustic signals due to a PD event are transient, irregular and non-repetitive. So wavelet transform is an efficient tool for this signal processing problem that gives a time-frequency demonstration. First, different wavelet based de-noising methods are analyzed. Then, a reasonable structure for threshold value determining and applying manner on signals is presented. Evaluated errors are good evidences for choices. Next, applying the elimination low energy frequency bands is discussed and developed as a de-noising method. Time differences between signals are used for PD localization. Different ways in time arrival detection are introduced and a novel approach in energy criterion method is presented. At the end, the quality of algorithm is verified through the different assays in lab.

This paper addresses the preparation of polyaniline (PAni) and polypyrrole (PPy) nanostructures as humidity sensor elements. The semicrystalline microstructure and chemical structure of synthesized PAni and PPy were studied by X-ray diffraction and Fourier transform infrared spectroscopy, respectively. The morphology of these polymers was studied by scanning electron microscopy and transmission electron microscopy, indicating fibrillar and tubular nanostructures for PAni and PPy, respectively. The humidity sensing performances of sensors based on the prepared nanostructural PAni and PPy were investigated, and the sensing mechanisms of both systems have been discussed. The interesting reverse behaviors during humidity exposure of PAni- and PPy-based sensors in different water vapor concentrations have been comprehensively justified. The temperature dependency of the electrical conductivity for PAni and PPy samples was investigated. The UV–vis spectroscopy was used to study the effect of moisture on the electronic transport properties of PAni and PPy nanostructures.

The present article provides an analysis of complex dynamics displayed by Power-Factor-Correction Boost Converter under Peak Current-Mode Control. PFC Boost converter has been studied with nonlinear analysis and the discrete-time modeling approach has been used. In order to increase stable period-1 operation range, new application of ramp compensation approach has been used, also slope of the compensating ramp that guarantees the stable operation of the PFC Boost converter is investigated. Finally, results are proven by simulation and theoretical analysis.

The present article provides an analysis of complex dynamics displayed by current mode controlled switching dc-dc converter. Current-mode controlled boost converter has been studied with nonlinear analysis and the discrete-time modeling approach has been used. By changing circuit parameters, complex behaviors like chaos and bifurcation occur in the switching dc-dc converter. For increasing stable period-1 operation range, the ramp compensation approach has been used and by changing its slope, its effect in the converter will be shown. Finally, the largest average lyapunov exponent for different slopes is reviewed and simulated.

This paper is concerned with the current control of grid connected inverters based on a simple frequency adaptive repetitive controller. A grid-tie inverter is desired to behave as a robust current source inverter with the high gain in order to improve both the reference current tracking and disturbance rejection capabilities. The variations of grid impedance and frequency in distribution networks are some important challenges in the design of grid interfaced converters. In this research, the performance of a frequency adaptive repetitive controller (RC), which is based on the internal model principle (IMP), is investigated for a single-phase grid connected inverter.

This paper presents design consideration and performance analysis of novel reduced parts on-line three-phase uninterruptible power supply (UPS) system. The proposed UPS system is based on reduced switch count dual bridge matrix converter. It employs only six power switches, results in reducing the cost of the system compared to conventional on-line UPS topologies, while achieving excellent performance. The performance of proposed system is evaluated through simulation in term of input/output waveforms quality and shows the viability of topology.

Many conventional incremental conductance (INC) methods are used for maximum power point tracking (MPPT) of photovoltaic (PV) arrays. In these methods the step size determines the speed of MPPT. Fast tracking can be achieved with bigger increments but the system might not operate exactly at the MPP and may oscillate about it instead; so there is a tradeoff between the time needed to reach the MPP and the oscillation error. The main purpose of this paper is to present an adaptive step size in the INC to improve solar array performance. Conventional proportional integral (PI) controller is applied the MPP to the PV output voltage terminals; however, in this paper brain emotional learning based intelligent controller (BELBIC) is used as an adaptive step size in the INC. This controller decrease the oscillation error, so there will be a considerable increase in system accuracy. At the end, the effectiveness of the proposed method is verified by simulation results at different operating conditions and comparing them with simulation results of conventional method.

This paper presents design consideration and performance analysis of novel reduced parts online three-phase uninterruptible power supply (UPS) system. The proposed UPS system is based on reduced switch count dual bridge matrix converter. It employs only six power switches and results in reducing the cost of the system compared to conventional online UPS topologies, while achieving excellent performance. The performance of the proposed system is evaluated through simulation in terms of input/output waveforms quality and shows the viability of topology.

This paper is concerned with the control of three-phase Uninterruptible Power Supply (UPS) systems based on a B-spline Network (BSN). A UPS must be able to maintain regulated output voltage in the face of all line/load disturbances. To achieve this, the control system of a UPS must have a fast transient response and a low steady-state error. Fast controllers cannot always maintain the required steady-state accuracy. Therefore, in this paper, a hybrid control solution is proposed. In the proposed method, a fast yet simple controller based on deadbeat (DB) control law is used to achieve the fast transient response required for UPS output voltage control. A B-spline based controller is added to the deadbeat controller to improve steady-state performance of the UPS system. This results in distortion-free output voltage along with a fast error convergence. The system modeling and controller design for the proposed structure are presented in this paper. Simulations results are shown for verification of the theoretical analysis.

This paper describes design considerations and performance analysis of a novel on-line singlephase to three-phase uninterruptible power supply (UPS) with reduced number of switches. The proposed topology uses only 5 active switches reducing the cost of the system compared to the traditional 10-switch topologies. The proposed UPS consists of a single-phase rectifier/charger, a two-leg/three-phase inverter connected to load, battery bank, DC link capacitor and an AC inductor. Detailed circuit operation and analysis as well as simulation results are also presented to verify its feasibility.

High performance UPS inverters have stringent control requirements both under steady-state and under transient conditions. Many different control techniques have been applied to UPS inverters. However, there are few publications reviewing the literature on these control techniques and classifying the same, particularly with regard to the recent developments in this area. In this paper, a review of the most solutions for control of UPS inverters is carried out. These control techniques are classified as conventional or classical control, predictive control, learning control and nonlinear control. The major advantages and disadvantages of these methods are highlighted and compared. Then, five control methods were compared using simulation and a hybrid controller (Repetitive Controller plus Deadbeat Controller) is evaluated by using experiments.

Transformers are a major capital item and the cost of a failure is high both in direct costs and downtime. For this reason they are monitored using a variety of methods. Partial discharges in power transformers are often a predecessor of a serious fault for this reason. Partial discharge measurements are an important diagnostic tool to monitor the insulation condition of a transformer. For on-line measurements, a detection method based on the acoustic signals emitted by the discharging source is used and can be detected. Moreover, the acoustic technique offers the possibility to locate and identify the PD source. This paper covers general aspects of acoustic methods for PD detection and localization in time, frequency and time-frequency domain.

Due to the growing use of photovoltaic (PV) systems in recent years, the reliability of these systems as one of the most important issues regarding durability and correct performance is important. This paper presents a comprehensive assessment of the reliability of Residential PV System (RPVS) in various conditions based on the Markov model. The systems taken into considerations consist of PV modules, a DC-DC converter, an inverter, an inverter controller, and a maximum power point tracking (MPPT) controller. These systems are considered repairable. To evaluate the effect of the three-phase boost converter and the PV modules on reliability, these systems have been considered towards this specific perspective. Furthermore, the impact of various factors on the reliability of the system components and the entire system is evaluated. Simulation results demonstrate the capacity of the proposed method to assess and comparison of the reliability of different RPVS. Also, the results indicate the impact of various factors such as temperature on it.

Uninterruptible power supplies (UPS) play an important role in supplying critical loads. The majority of UPS systems employ batteries as a mean of energy storage. Since typical loads are supplied by AC voltage, an inverter is an indispensable part of a UPS to convert DC voltage to AC. Conventional control methods for single phase inverters suffers from many drawbacks like slow dynamic/transient response, oscillatory no-load behavior and distorted waveform in presence of non-linear loads. This paper in concerned with the control loop design for a single-phase voltage source inverter when employed in UPS applications. The regulation of the output voltage is done based on reference tracking to ensure good steady-state and dynamic performance. The control loop is designed taking into consideration the low damping during light loads. Three control strategies are proposed. The first is based on modified PID controller which demonstrated moderate performance and is suitable for low cost applications. The second method is based on an additional current control loop which has the benefit of inherent inverter protection. The last method is based on the theory of "internal model controller" which gives nearly ideal steady-state regulation. Key points in implementing controllers with digital controllers are addressed. An experimental system is built to verify the validity of theoretical results

This study is concerned with the control of three-phase uninterruptible power supply (UPS) systems based on a hybrid controller. A UPS must be able to maintain regulated output voltage in the face of all line/load disturbances. In order to achieve this, the control system of a UPS must have a fast transient response and a low steady-state error. Fast controllers cannot always maintain the required steady-state accuracy. Therefore in this study, a hybrid control solution is proposed. In the proposed method, a fast, yet simple, controller based on deadbeat (DB) control law is used to achieve the fast transient response required for UPS output voltage control. Noting that non-linear loads that tend to distort UPS output voltage in steady-state have periodic waveforms in nature, a type of learning controller known as a repetitive controller is added to the DB controller to improve steady-state performance of the UPS system. This results in distortion-free output voltage along with a fast error convergence. The system modelling and controller design for the proposed structure are presented in this study. A brief stability analysis is given. Both simulations and experimental results are shown for verification of the theoretical analysis.