Sharif Digital Repository

Nowadays, reduced switch rectifiers are more interested because of less expense. Control of these rectifiers is an important part of their designing process. In this paper, a method is proposed for four-switch rectifier to continue working under unbalanced input voltage. To achieve this goal, first a method is introduced to separate positive and negative sequences of dq components. Also, the necessary condition is determined. Considering this condition, the control method is modified and new reference value for the control signals is calculated. Finally, the system is simulated in Simulink and the results are provided. These results confirm the accuracy of the developed model, and also the... 

In this paper, a small signal model is proposed for four-switch rectifier with input power factor correction. The required transfer functions are determined and calculated for a typical rectifier. This model is used to design an appropriate controller with defined characteristic to improve the rectifier performance. Another controller is used to compensate capacitors dc voltage difference. The system is simulated in Simulink and the results are provided. These results confirm the accuracy of the developed model, and also the effectiveness of the proposed controllers  

The design strategy and efficiency optimization of UHF micro-power rectifiers using a novel diode connected MOS transistor is presented. The proposed diode connected MOS transistor uses a new bulk connection which leads to reduce the threshold voltage and leakage current in compare to conventional diode connected transistors. Using the proposed diode in typical rectifiers makes a significant improvement in output voltage and current therefore the efficiency is increased comparing to the same rectifier architectures using conventional diodes. Also a design procedure for efficiency optimization is presented and a superposition method is used to optimize the performance of multiple output... 

In this study, a simple and novel control technique for Power Factor Correction (PFC) is introduced, which is a SEPIC-based (Single-ended Primary-inductor Converter based) rectifier with high input power factor. Operation of the proposed method is based on sampling of input and output voltages in SEPIC rectifier. Using samples of input and output voltage, this control system makes the input current to follow a sinusoidal path. As a result, the line current?'s Total Harmonic Distortion (THD) is reduced and the input power factor is improved. This paper also compares the new method with the conventional control method for the power factor correction. In order to examine the proposed control... 

A space vector modulation (SVM) approach is proposed to control a four-switch rectifier with power factor correction and compensating the effect of capacitors voltage ripple. The theory and performance of this method are presented, and the method effectiveness is demonstrated by extensive simulations. The simulation results show that the capacitor voltage ripple effects in the output voltage and current shaping can be omitted and the rectifier can work agreeably under high power factor condition although capacitors voltage is not balance. The allowable amount of this unbalanced value of filter capacitors is determined  

Rectifiers are an integral part of power harvesting systems. In this paper, the literature on RF power rectifiers is surveyed, starting from the well-known voltage doubler. Effects of using low turn-on voltage devices on forward and reverse losses, and therefore, on conversion efficiency, is discussed. Samples of rectifiers with external devices, such as Schottky diodes are presented. Idea of external Vth cancellation through a rechargeable battery, self Vth cancellation, and floating gate transistors with charge injection onto the gates are demonstrated. Then, standard bridge rectifier and its modified versions, including Vth cancellation technique, are explained. Using low voltage devices... 

Unidirectional current flow is at the heart of modern electronics, which has been conceived by making p–n junctions or Schottky barriers between different kinds of materials. Within such elements, however, synthesis of thin film lateral heterostructures has so far remained challenging. Here, a one-step simple synthesis of p-type, n-type, and metallic lateral heterostructures using bipolar electrodeposition (BPE) technique is reported. Molybdenum oxides and sulfides with gradient of oxygen and sulfur are deposited at a metallic substrate. A lateral heterostructure is achieved with electrical properties that change from p- to n-type semiconductor and then to metal by moving in the plane of the... 

In new 400 volt energy distribution systems for telecommunication sites and data centers power density is an influential factor which is commonly desired to be provided such that the systems occupy a small space. On top of that in 400 volt energy distribution systems galvanic isolation is investigated to be inevitable. In this paper a new method is presented that makes it possible to interleave the topology of an isolated low-cost low-size rectifier in which the DC link capacitor of power factor correction stage and DC-DC stage inductor are eliminated and as result it is shown that all the benefits of interleaving such as low current ripple and higher power density are combined with the... 

Power density is an influential factor in 400 volt telecom energy distribution systems. In addition, systems are desired to reach an acceptable efficiency while they take advantage of a galvanic isolation. This paper presents a new architecture that is based on push pull topology and its power switches perform ZVS in both their turn on and turn off conditions. Besides, the presented topology uses an interleaving technique that has made it desirable for high power applications. Power loss for the presented topology is calculated and compared to conventional topologies. Finally, by considering the efficiency and power density of the presented topology, it is concluded why this topology is... 

Depending on the reference frame, a proportional integral (PI) or proportional resonant (PR) controller is often utilized for current control in the three-phase PWM rectifiers. Due to the fact that the controller bandwidth is either smaller than the frequency of a specific order harmonic or the controller gain at that frequency is too low the harmonics cannot be effectively eliminated. Among all approaches introduced for harmonic elimination, selective harmonic compensation is believed to have a better performance. Selective harmonic compensation can successfully compensate for harmonics. It, however, forces a considerable computation burden on DSP. This paper proposes a new compensation... 

Voltage source converter based multi - terminal DC grids (VSC - MTDC) are widely used for integration of renewable resources. Control of these grids requires vector control method, which includes inner and outer current controllers, tuning of these controllers is very important. Conventionally used tuning methods consider approximated linear model to tune the proportional - integral (PI) parameters of voltage source converter (VSC) which fails to produce optimum disturbance rejection results. In this research an Ant Colony Optimization (ACO) technique is used to get the optimum parameters of inner and outer power control layers for multi - terminal DC system. ACO is applied simultaneously on... 

Voltage source converter based multi - terminal DC grids (VSC - MTDC) are widely used for integration of renewable resources. Control of these grids requires vector control method, which includes inner and outer current controllers, tuning of these controllers is very important. Conventionally used tuning methods consider approximated linear model to tune the proportional - integral (PI) parameters of voltage source converter (VSC) which fails to produce optimum disturbance rejection results. In this research an Ant Colony Optimization (ACO) technique is used to get the optimum parameters of inner and outer power control layers for multi - terminal DC system. ACO is applied simultaneously on... 

Battery and plug-in hybrid vehicles equipped with bidirectional battery chargers are capable of supplying power to the electric grid according to power system demand. This technology is called 'vehicle to grid' or V2G. A bidirectional on-board charger can be used to improve the charge availability. An on-board charger should have small size and light weight. On the other hand, the charger must minimize power quality impact, draw current at high power factor to maximize power from an outlet. In this paper, a new three-phase integrated bidirectional isolated soft-switched battery charger is proposed which is appropriate for vehicle to grid technology. The charger utilizes a 4-switch... 

In this paper, a new zero-voltage-switching, high power-factor, bridgeless rectifier is introduced. In this topology, an auxiliary circuit provides soft switching for all of the power semiconductor devices. Thus the switching losses are reduced and the highest efficiency can be achieved. The proposed converter has been analyzed and a design procedure has been introduced. The control circuit for the converter has also been developed. Based on the given approach, a 250 W, 400 Vdc prototype converters has been designed at 100 kHz for universal input voltage (90-264 Vrms) applications. A maximum efficiency of 94.6% and a power factor correction over 0.99 has been achieved. The simulation and... 

This study presents an analytical approach for proper selection of output functions to be regulated for the Vienna rectifier such that the resultant closed-loop systems are minimum phase. Specifically, two different adaptive control methodologies based on the input-output linearisation are developed and categorised. In the first category, three output functions are introduced and imposed to be zero by using three dynamic feedback laws. On the basis of states to be regulated, four different cases are studied and it is shown that only one of these cases results in a one-dimensional zero dynamics with an asymptotically stable equilibrium point. In the second category, two output functions are... 

In this paper, a new zero-voltage-switching high power-factor (PF) rectifier with Line-Modulated Fixed-Off-Time current control is introduced, that off time is a function of the instantaneous line voltage. The auxiliary circuit provides soft switching for all semiconductor devices, without any extra current and voltage stress on the main switches. The proposed converter is bridgeless, and all semiconductor devices are soft switched. In addition, there is no extra stress on the switches. Thus, the conduction and switching losses are reduced and maximum efficiency is achieved. A 250W, with an input ac voltage of 90265 Vrms and an output voltage 400 Vdc, 100 kHz is designed and simulated to... 

Development of high frequency power electronic devices leads to high performance and flexible switch mode AC voltage stabilizers instead of traditional electromechanical types. This paper introduces a novel double stage topology for switch mode AC voltage regulators. The system produces a continuous adjustable isolated AC voltage providing a constant output voltage for sensitive loads. In order to simplify the control strategy, a symmetrical PWM is used. In contrast with conventional AC choppers, the proposed circuit does not need any snubber circuits or voltage and current sensors which leads to a simpler and more reliable circuit. Detailed analysis and simulation results show the... 

This paper presents a high performance Direct Torque Control (DTC) theme for the induction motor using Indirect Matrix Converter (IMC). To improve the dynamic behavior of motor, Active Learning Method (ALM) is implemented on the DTC. The ALM uses its own modeling technique called the ink drop spread (IDS) method. Functionally the IMC is very similar to the Direct Matrix Converter (DMC) but it has separate line and load bridges. In the inverter stage, the classical DTC method is employed. In the rectifier stage, in order to reduce losses caused by snubber circuit the rectifier four-step commutation method is employed. By suitably selecting switching pattern and using Active Learning Method... 

Single-phase power factor correction (PFC) converter circuits are non-linear systems due to the contribution of their multiplier. This non-linearity causes difficulties in analysis and design. Models that reduce the system to a linear system involve considerable approximation, and produce results that are susceptible to instability problems. In this paper a piecewise affine (PWA) system is introduced for describing the nonlinear averaged model. Then robust output feedback controllers are established in terms of the linear matrix inequality (LMI). Simulation and experiments results show the effectiveness of the proposed control method  

In this paper a single stage structure is proposed for realizing a three-phase unity power factor rectifier. This topology utilizes a forward/flyback transformer to allow the high-frequency isolation. The principle of the operation and the applied control concept is discussed. Space vector modulation is used in order to achieve unity power factor and to have the output voltage be regulated. Furthermore, the system transient is analyzed during turn-on and a novel method is applied to the control system in order to limit inrush current during startup. The proper operation of the soft-start method is confirmed by numerical simulation of a 6KW, 380V/48Vdc. The stability of the closed-loop as...