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This paper shows an innovative improvement of the constant on time (COT) control of transition mode boost PFC. The proposed control method employs a minimum current comparator to improve the harmonic distortion and power factor of the converter while maintaining the same complexity of the constant on time control. An overview and the enhancements of this method are presented in comparison to the standard...
A new method to selectively control the amount of dc-link voltage ripple by processing the desired reactive power by a DC/DC converter in an isolated AC/DC or AC/DC/AC system is proposed. The concept can reduce the dc-link capacitors used for balancing the input and output power and thereby limiting the voltage ripple. It allows the use of a smaller dc-link capacitor and hence a longer lifetime and...
This paper presents a novel loss balancing modulation method for more evenly distributing semiconductor losses in multilevel active neutral-point-clamped (ANPC) converters. The presented method is achieved by optimally utilizing the redundant switching states of space vector pulse width modulation (SVPWM) in ANPC converters. A comparison of the effect of losses distribution between the proposed loss...
In this paper is presented a shunt active power filter with a reduced number of inductors for harmonic and reactive power compensation in three-phase three-wire electrical systems. The proposed configuration is based on two single-phase shunt active power filters connected to a three-phase three-wire grid. The two single-phase cells can be achieved by a three-leg singlephase to single-phase ac-dc-ac...
As the development and installation of photovoltaic (PV) systems are still growing at an exceptionally rapid pace, relevant grid integration policies are going to change consequently in order to accept more PV systems in the grid. The next generation PV systems will play an even more active role like what the conventional power plants do today in the grid regulation participation. Requirements of...
This paper proposes a virtual series impedance emulation control strategy for current controlled remote PV or wind farms, in order to enhance the power transfer capability of the transmission line. This approach can be regarded as integrating the functions of the FACTS devices, such as series capacitors, into the grid-side converters of PV or wind farms, by utilizing the reactive power capability...
This paper concentrates on the control of the integrated battery storage Power Conditioning Systems (PCS) parallel system in Microgrid (MG). The theoretical analysis of the different operation modes are clearly studied, including grid-connected and islanded mode. To improve the power sharing accuracy during the islanded operation, an enhanced droop controller is introduced. The proposed approach is...
A controller for single phase DC/AC converters is proposed that is analogous with the droop control method used in synchronous generator technology. Its approach is different from the existing droop techniques adopted for power electronic inverters where consistently the output voltage is controlled through an explicit voltage control loop. The proposed method indirectly controls the output voltage...
A strategy to improve the power factor (PF) at the point of common coupling (PCC) for microgrid applications is presented in this paper. The position of the compensating unit is selected to correct the power factor and reduce the harmonic levels of the grid current and PCC voltage in microgrid connected distributed renewable energy sources. The proposed compensation system for power factor improvement...
This paper proposes an improved modulated carrier control for single-phase shunt active power filter, which eliminates harmonic and reactive currents at ac sources drawn by nonlinear loads. This control method directly shapes line current to be sinusoidal and in phase with grid voltage by comparing a modulated carrier signal to the average line current and making duty ratio doubled. Since the line...
This paper presents a decoupled and adaptive droop strategy to coordinate parallel operation of inverters. This strategy neatly combines a novel decouple method and an adaptive power sharing strategy. The decouple method guarantees the system stability by defining a pair of virtual power and utilizing a low pass filter to achieve dynamic decoupling. And the adaptive power sharing method is included...
Soft-switching ac-link buck-boost converters, also known as ac-link universal power converters and partial resonant ac-link converters, have received remarkable attention during the last few years. These converters, which can be configured as dc-dc, dc-ac, ac-dc, or ac-ac (single-phase or multi-phase), are compact, reliable, and expected to offer longer lifetime compared to the other types of converters...
LCL filter is becoming an attractive choice over conventional L filters for grid-connected voltage source inverters (VSI) due to smaller inductor size and better attenuation of the ripple components in the grid current. The modulation of the VSI generates switched voltages which results in distorted currents. In this paper, a simple closed form analytical expression is derived for the higher order...
Conventional AC-DC driver circuits for Light-Emitting Diode (LED) lamps require large output capacitance across the LED load to minimize the low frequency current ripple. This large capacitance is usually achieved by using an electrolytic capacitor, which has a lifetime that is at least two times less than that of a LED device. To match the potential lifetime of the LEDs, a new isolated single switch...
For a conventional offline Buck-Boost LED driver, significant low frequency ripple current is produced when a high power factor has been achieved. In this paper, an innovative LED driver technology based on the Buck-Boost topology has been proposed. The featured configuration has greatly reduced the low frequency ripple current without compromising power factor performance. High efficiency and low...
In many rural areas, due to unavailability of three-phase AC power, three-phase Variable Frequency Drives (VFDs) are often required to operate from single-phase AC source. Powering up three-phase VFDs from single-phase AC source requires addressing many issues — higher rms value of input diode current, higher ripple voltage across the DC bus capacitor, higher peak input current, higher input current...
A grid-tie solar inverter with capacitor-supported series voltage compensator for reduction of high-voltage dc-link capacitance is proposed in this paper. The series compensator generates a voltage to counteract the voltage ripple on dc-link capacitor. As the magnitude of the AC voltage ripple is smaller than the dc-link DC voltage, the required voltage-current rating of the compensator is small....
This paper introduces a soft-switched high-frequency-link inverter for grid-tied PV systems. This single-stage inverter can perform the step-up/down operation and also has the ability to effectively harvest the highest possible power from the PV array. The high-frequency link is formed by an ac inductor and a small ac capacitor without the use of bulky short-life electrolytic capacitors. The link...
This paper proposes an improved space vector modulation (SVM) method for the 3-level neutral point clamped (NPC) inverter that serves as a bidirectional power conversion system for renewable energy micro-grid. Conventional SVM for the NPC converter majorly deals with neutral point (NP) balance issue without considering switching loss. The proposed SVM method balances the NP voltage and minimize the...
Droop control and some improved droop control methods are adopted to control microgrid inverters not only in island mode, but also in grid-connected mode. This paper presents a state space model of three phase paralleled inverters in grid-connected microgrid based on droop control to facilitate the control design and stability analysis. This model is established in rotation framework based on modern...
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