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This paper extensively analyzes the operation limits, system stability and disturbance rejection capability of the voltage control loops used in master-slave AC and DC Microgrids (MGs). Two different control schemes are studied analytically, simulated and experimentally tested, focusing on Constant Power Loads (CPL). Additionally, the use of the virtual capacitance (VC) as a tool for response enhancement...
Customers may have different power quality requirements, thus, the economic operational strategy can try to provide them with distinctive quality levels as customized service. An optimization based method is proposed in this paper to realize this functionality, offering the possibility that the customers can flexibly set and adjust their requirements. Converter interfaced distributed generators are...
Harmonic power sharing and PCC voltage quality are both important issues for the power quality of islanded microgrids. This paper proposes a new control scheme to deal with those two issues based on controlling the equivalent harmonic impedance of DGs. With the proposed control scheme, harmonic power is shared according to remaining power capacities of DGs and PCC voltage harmonics are effectively...
Day by day there is increase in use of renewable sources like solar, wind for generating power because of decrease in availability of non renewable resources of energy like coal, natural gas, oil and tremendous developments in energy storage devices. Microgrids incorporate large amount of non conventional and conventional distributed generation (DG) that are connected to the system either directly...
In the multi-bus islanded microgrids, the power quality requirements for different areas and buses can be different. This paper proposes a hierarchical control to realize optimal unbalance compensation for satisfying the power quality requirements in different areas. Primary and secondary controllers are applied to realize unbalance compensation for the critical bus(CB). In the secondary control,...
The utility interface (UI) converter is a three-phase power conversion unit equipped with energy storage which governs the interaction between the utility grid and the microgrid. The non-interruptive operation of UI is desired due to its several functions: 1) in grid-connected operation it performs as a voltage-supporting unit regulating the power flow through the microgrid point of common coupling,...
In this paper, a renewable energy based wind-PV microgrid is investigated for seamless transfer between the grid connected and isolated modes according to the grid availability. The VSC (Voltage Source Converter) based voltage and current controls are used to provide smoothness in both the operations. A battery bank is connected at the DC bus of VSC for load leveling during low power generations or...
Power Quality is playing an increasingly significant role both at supply and demand sides. With the advent of participation of private player's in distribution systems, the power quality is expected to be the pivotal decisive factor before the consumers. Due to ever growing application of switching devices, the power quality is bound to get deteriorated, at the same time such devices are also prone...
A distributed secondary voltage controller is designed for droop-controlled microgrids in power distribution networks to improve power quality. Microgrids are typically managed by the droop control mechanism that ensures stability but does not guarantee power quality of voltage magnitude. To solve this power quality problem, the proposed distributed secondary voltage controller maintains a constant...
Microgrids (MG) are turning out to be progressively appealing to consumers and an incredible number of them will be introduced at their premises in the near future as they allow utilization of freely available renewable energy sources. Because of high penetration of distributed generation units with distinctive sorts of loads, microgrids can be subjected to power quality and control issues. Some of...
In this paper, application of battery and supercapacitor units based hybrid energy storage system (HESS) integrated to the grid interactive microgrid environment is presented. HESS is nowadays most widely used in the electric vehicles, energy reserves, renewable energy sources (RES)based applications. These energy storage systems can also be added to the existing power conditioning units to improve...
This paper presents a new control method to regulate various parameters such as output voltage and power of the inverters interfaced with distributed generations (DGs) in the proposed microgrid system integrated with a distribution network device. Model Predictive Control (MPC) is used to control the inverters of the DGs using state-space model of the inverters in the proposed system. The distribution...
This paper presents a 5-level Cascaded H-Bridge Multilevel Inverter (CHMI) able to perform several tasks and applicable to a microgrid with multiple local power sources. The current control strategy is based on the conservative power theory (CPT) generating references for different modes of operation. The primary merits of multilevel cascade voltage source inverters are the possibility of having independent...
this paper presents a novel distributed generation (DG) control strategy under both distorted and unbalanced conditions. Actually the power quality of microgrid bus and the point of common coupling are the main concerns due to the determination of high-quality power energy to the main grid and sensitive loads connected to microgrid bus. To tackle this problem, three control schemes based on PIR cascaded...
Microgrids are becoming increasingly attractive to consumers as it allows utilization of freely available renewable energy sources. They are usually installed at consumer's sites i.e the distribution end. Due to high penetration of distributed generation units with different types of loads, microgrids can cause power quality and power control issues. Some of them are voltage swells and sags, and low...
In order to address the power quality enhancement in a given microgrid, independent control of reactive, unbalanced and distorted load current components, in a multi-inverter-based approach may be required. Therefore, this paper proposes a coordinated control strategy using the Conservative Power Theory (CPT) and assuming the contribution of all grid connected interfaces, especially those related...
In multi-inverter-based islanded microgrids with unbalanced and distorted loads, due to voltage drop across line, the load bus voltage is unbalanced and distorted, which shows the requirement for power quality increase at load bus. To address this problem, this paper presents master-slave-based cooperative operation of DGs with the implementation of Conservative Power Theory (CPT), in which in addition...
Due to the unbalance condition, the voltage of microgrid would be deteriorated. In this paper, a unify unbalance compensation strategy is proposed to suppress the unbalanced voltage and the voltage variation for islanded microgrid with unbalanced condition. Comparing to the traditional compensation strategy, where only negative sequence components of voltage are suppressed, in the proposed scheme,...
This paper discusses energy management and control algorithms of microgrid with energy storage. Specific management framework within microgrid presented here includes: a) help prioritizing the renewable energy sources (RES) to provide power to local loads, b) manage battery to avoid deep-discharging and overcharging, c) maintain dc link voltage at a specified value, and d) regulate ac voltage buses...
The paper presents a general control technique for Utility Interfaces acting in low-voltage microgrids. The Utility Interface (UI) is a three-phase power conversion unit, equipped with energy storage, which governs the interaction between the utility and the microgrid. It is in charge of several functions: in grid-connected operation, UI performs as a voltage-supporting unit and compensates for reactive...
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