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The objective of this research is to analyze and evaluate the performance of the proposed shunt-series switched multi-functional grid-connected inverter (SSS-MFGCI) for mitigating unbalanced voltage sag and swell problem in distributed generation system or microgrid. Three quantitative performance evaluation factors, namely fault level factor, rating factor, and grid stiffness factor, are proposed...
In this paper, a wireless modular control strategy for input-series output-parallel (ISOP) inverter system is proposed to ensure equal sharing of input voltage and output current among the constituent inverters. Compared with existing control strategies for the ISOP inverter system, such as centralized control which restricts the modularity of the system and distributed control which realizes voltage...
Unbalanced operation between panel-level modular inverters constrains the operating range of grid-tied cascaded H-bridge Photovoltaic (PV) inverter system when the active and reactive power of the architecture changes. The main objective of this paper is to propose a distributed control approach for balancing reactive power among inverters. The distributed controller allows fully decentralized architecture...
This paper puts forth a vision for scalable distribution grid integration of energy resources such as rooftop photovoltaics (PVs) and electric vehicles (EVs). The output of these resources vary temporally in an unpredicted manner. Therefore, they bring substantial challenges to utilities vis-a-vis massive deployment of such resources. By leveraging the fact that most of the distributed energy resources...
The well-known droop control and master-slave control methods are two dominant coordinative control schemes for inverter interfacing parallel distributed energy resources (DERs) in islanded AC microgrids. However, both these two control methods have some drawbacks and inherent limitations in practical application. After analyzing their complementary strengths and weaknesses, this paper proposed a...
This paper introduces a three-phase grid-connected inverter for commercial-scale photovoltaic systems. The circuit topology combines an electrolytic-capacitor-less and ac-inductor-less active bridge with a parallel-connected PWM inverter acting as an instantaneous reactive power compensator. The active bridge, called a 120°-conduction inverter, operates at the switching frequency equal to the grid...
Advanced control techniques such as Volt-Watt and Volt-VAR Control have been developed for high integration of distributed renewable energy, such as Photovoltaic (PV) resources, on an electric distribution system. However, designing these control parameters which yields the best results in the system is complicated and depends on feeder conditions. This paper proposes a method to properly design the...
Electrical energy generation is evolving from centralized towards distributed energy resources (DER) like wind and solar power plants. In such power systems, new challenges arise for the design of voltage source converter (VSC) control strategies. In the last few years synchronverters have gained interest from the research community due to their capability of emulating synchronous machines (SMs) and...
This paper proposes a power factor correction method of a non-resonant IPT system using a four-winding transformer. The proposed technique is applied to the IPT system with a dual active bridge converter to reduce conduction loss and winding loss. When two pairs of the primary-side and the secondary-side wires are connected in parallel, the low coupling coefficient between the wires driven by in-phase...
Nowadays, due to the high-scale penetration of photovoltaic systems, reliable and efficient photovoltaic grid-connected systems using the advances of power electronics and advanced control techniques are desirable. In this paper, using the general structure for synchronous dq0 frame, a single-stage three-phase grid-connected photovoltaic inverter with a nonlinear control strategy is developed to generate...
The proportional power sharing has been identified as an important issue to guarantee reliability on the operation of low voltage AC-Microgrids. However, inaccurate reactive power sharing in scenarios with line impedance mismatches, and slow transient response remain important limitations of most of the conventional power sharing controllers. In this context, an improved method for power sharing control...
Semiconductor power modules are widely used in machine drive applications. The temperature distribution in the power module is the result of load properties and the drive cooling. The temperature induced thermal-mechanical stress in the power module bond wires is critical for the power module reliability and lifetime. In this paper, a two level, three phase Silicon-Carbide (SiC) inverter power module...
Single-phase grid-connected inverters with LCL filter are widely used to connect photovoltaic systems to the utility grid. Among the existing control schemes, predictive control methods are faster and more accurate but also more complicated to implement. Recently, the Model Predictive Control (MPC) algorithm for single-phase inverter has been presented, where the algorithm implementation is straightforward...
In this paper, reactive power variation based on positive feedback is proposed for improving islanding detection in the distributed generation. The proposed reactive power variation method consists of two parts, where the first part has a fundamental amplitude as +5%Pinv or −5%Pinv, and the second part has a positive feedback using a frequency deviation. Polarity and amplitude of RPV method are determined...
To address the DC link voltage regeneration issue in parallel Uninterruptible Power Supply (UPS) system, a DC link voltage protection (DCVP) method through online virtual resistance regulation is proposed. The proposed control strategy is able to protect the DC link from overvoltage that may trigger the protection mechanism of the UPS system. Moreover, a current sharing control strategy by regulating...
Because of the differences in line impedances, parallel inverters with conventional droop control will have huge circulating current, which does not flow through the loads. To mitigate the circulating current, the research in this paper finds out that parallel-operated inverters should have the impedance in inverse proportion to their capacities, which is difficult to realize in practice. To meet...
Voltage unbalance in a three-phase system introduces oscillations to the DC Link voltage and power. Moreover, it causes performance deterioration of a pulsewidth modulation (PWM) of the back-to back voltage source converter systems (BTB-VSC) by producing the double-line-frequency ripples in the dc link voltage and power. This paper proposes a new control strategy by developing the conventional vector...
In order to address the economical dispatch problem in cascaded microgrids, this digest proposes an optimal economical-sharing scheme via decentralized approach only with the local information. This overcomes the limitations of centralized control, where the central controller and external information exchange are needed. The frequency and current are used as carriers driven the distributed generators...
A method for generating reactive power in photovoltaic (PV) inverters is presented. This method is based on the extraction of active and reactive components present in the output current of a PV-Inverter using a scheme consisted of low pass filter. The extraction results, together with the unity sinusoidal signal obtained from the phase lockup loop is used to generate a reference for current controller...
This paper investigates the effects of unintended island operation mode on parallel inverters' performance for microgrid applications. In the grid-connected mode, each inverter has a different power set point. The power flows between the inverters and the grid. In the islanding mode, the power flows inherently from the inverter that has higher set point power to the inverter has lower one leading...
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