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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 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...
Conventional droop controls have been widely studied for load sharing in dc Microgrids. However, unlike ac Microgrids, transmission line impedances can undermine the controller's performance, and it might fail to provide regulated rated voltage and proportional load sharing. Herein, a distributed secondary controller is introduced that includes two modules; a voltage regulator and a current regulator...
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...
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...
This paper proposes an autonomous active and reactive power distribution strategy that can be applied directly on current control mode (CCM) inverters, being compatible as well with conventional droop-controlled voltage control mode (VCM) converters. In a microgrid, since renewable energy sources (RES) units regulate different active power, the proposed reactive power distribution is adaptively controlled...
This paper proposes a novel approach to compensate the voltage at the point of common coupling (PCC) and the grid line current harmonics through a distributed generation (DG) interfacing converter in a weak microgrid. In the proposed approach, the PCC voltage is indirectly derived from the measured converter output voltage, DG line current and line impedance. A voltage closed-loop controller and a...
A microgrid is an integration of distributed energy sources, loads and energy storage systems. Indeed, energy storage systems are required in order to ensure reliability and power quality because of the intermittent nature of renewable energy sources and changes of load demand. Apart from that, the use of distributed energy storage units provides redundancy to the system and support possible increments...
This paper details the development of a microgrid laboratory test rig capable of emulating linear and non-linear loads as well as dynamically varying electrical machinery such as wind turbine generators, flywheel energy storage systems and other motor/generator equipment. This test-rig is comprised of two 15 kW dc-ac converters connected in a back-to-back configuration together with a rapid control...
Renewable-intensive microgrids are mainly actualized using voltage-source inverters (VSI). Voltage-controlled and current-controlled VSIs can manage voltage/frequency and active/reactive power flow in microgrids, respectively. A two-layer cooperative strategy is proposed that simultaneously controls both the voltage/frequency as well as the active/reactive power flow. The proposed strategy is fully...
The conventional droop control method, which does not require communication lines, is an effective control scheme to dispatch power among inverters in the microgrid. However, this method has inherent tradeoffs: frequency vs. active power accuracy and amplitude regulation vs. reactive power sharing accuracy. To cope with this problem, this paper presents a novel active power control strategy to improve...
This paper proposes a new distributed battery energy architecture based on the micro-bank modules for DC microgrids. The benefits of the proposed architecture include 1) no voltage sharing problem and no overcharge/overdischarge problem; 2) high compatibility and reliability 3) high energy utilization efficiency; 4) reduced volume and weight of the BMS. Taking advantage of the battery recovery effect,...
This paper presents an islanded AC microgrid composed of multi-DGs and an energy storage system. The point of common coupling (PCC) frequency and voltage magnitude are controlled by the ESS while other DGs can export active power and reactive power independently. A nonlinear energy management control strategy is proposed by utilizing the PCC frequency as an agent for all constituent units, which avoids...
Maintaining a reliable operation in microgrids has significant importance. One factor required for the reliable microgrid operation is to keep certain energy reserve without sacrificing the cost for satisfying any load variation. Reliability and cost optimization of photovoltaic and fuel cell based microgrid system is investigated in this paper. A typical residential load is considered in order to...
In this paper, an improved power flow analysis algorithm for distributed generation (DG) units controlled with P/Q droop functions and virtual impedances in a low voltage (LV) microgrid is proposed. The proposed analysis provides in contrast to conventional power flow calculation techniques: (i) consideration of virtual impedance parameters and (ii) higher accuracy in reactive power flow calculation...
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