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In this paper a Genetic Algorithm (GA) is used to partition a distribution network with the aim to minimize the energy exchange among the microgrids (i.e. maximize self-consumption) in presence of distributed generation. The proposed GA is tested on the IEEE prototypical network PG & E 69-bus. The microgrid partitioning is tested over a period of one year with hourly sampled data of real household...
A key objective to be fulfilled by distributed voltage source inverters working in parallel in islanded MicroGrids (MGs) is to ensure active power sharing while keeping the frequency at a desired setpoint. Recently, consensus-based control techniques have been applied at the secondary control level for active power sharing while correcting the frequency deviation that the droop control implemented...
Microgrids have become an alternative to increase the controlability and resilience of the electrical system due to the local and efficient energy management they provide. Additionally, when the microgrid has a main DC bus it does not require synchronization hence the control scheme is simplified allowing to improve the dynamics of currents and voltages. These DC microgrids are usually controlled...
A microgrid powered by inverters has become a typical approach to efficient use of renewable energy source. However, the behavior of constantcurrent of the inverters will make it difficult to protect the network. To solve this problem, this paper offers the directional interlocking overcurrent protection for the microgrid powered by the inverters injected with characteristic current. When a fault...
This paper proposes a new control scheme for harmonic power sharing and PCC voltage harmonics compensation in islanded microgrids by adopting virtual harmonic impedance method. Firstly, a droop relationship between the equivalent harmonic impedance of distributed generation (DG) units and their remaining power capacities (ZDG_h_eq-SDG_remaining droop relationship) is put forward. Then, a virtual harmonic...
The voltage source inverters operating in islanded microgrid are used as sources of power similar to synchronous generators (SG) in conventional power system. Unlike synchronous generators, these inverters neither have a natural droop (P-f and Q-V) characteristics nor rotational inertia. The electrical time constant is much lesser than mechanical time constant and hence the load changes will show...
This paper proposes an adaptive power management strategy with reduced sensor requirement for grid connected hybrid microgrid system under faulty conditions which occur in grid tied converters. Generally parallel combination of grid tied converters (GTCs) are used as an interface between microgrid and grid, which are responsible for power transfer among renewable energy sources (RES), hybrid energy...
This paper proposes a power sharing scheme for an Islanded DC microgrid with hybrid energy storage system (HESS). HESS comprises of battery and supercapacitor (SC), where the usage of supercapacitor reduces the current stresses on the battery. This scheme reduces the losses in the HESS interfacing converters along with State of Charge (SOC) balancing. To maintain a constant DC link voltage a DC link...
This paper proposes a novel distributed control scheme for DC microgrids to acquire minimum generation cost and recover the global average voltage with consideration of capacity constraints. Our main focus is on constrained problems where the power of each distributed generator (DG) is restricted to lie in the feasible region. In this paper, a global load observer (GLO) is introduced that uses neighbor's...
This paper proposes a multi-port solid state transformer (SST) to integrate a hybrid microgrid with 380 V dc, 48 V dc and 415 V ac sub-grids to the medium voltage distribution network. The system replaces multiple single phase transformers in the conventional SST with one multi-winding transformer thereby reducing the magnetics involved. Moreover, the individual dual active bridges (DAB) in the conventional...
This paper investigates the problem of accurate active power sharing in virtual flux droop where flux angle droop control is used for DG controllers instead of traditional frequency droop control. Firstly, the virtual flux droop control method is introduced. Then, the reasons for inaccurate active power sharing in flux angle droop are analysed. Further, to solve this problem, an active power compensation...
DC (Direct Current) microgrid has gained more attention caused by the development of distributed generations and DC loads. The control objectives for DC microgrid are voltage regulation and current sharing. In order to achieve these objectives, consensus based control methods with communication have been extensively studied recently. It is a common strategy to modify the voltage set point of local...
The high R/X ratio of distributed lines in low voltage microgrid causes the coupling between the active and reactive power control. Forcing the output impedance to achieve the decoupling through additional virtual inductor impedance loop heavily causes the voltage amplitude drop at the point of common coupling. Such voltage drop deteriorates the microgrid voltage stability. To avoid the problem of...
In industrial microgrids with medium power rating photovoltaic systems, the low-voltage ride-through capability should be incorporated to help keep power system stability. The goal of this paper is to present a control strategy that allows taking advantage of the maximum capability of the inverters to support the most dropped phase in a photovoltaic-based industrial microgrid during voltage sags....
An energy management system of a microgrid (MG) has several basic objectives; e.g. to maximize the utilization of renewable energy resources (RES), to protect the internal components from overloading, and to ensure that the MG operates reliably under any operating conditions. Although many control techniques are available in the literature to monitor and control the energy flows among distributed...
In this paper, the concept of P-Z-N distributed bipolar DC system is proposed in differentiation with existing PN distributed bipolar DC system. Such configuration enables each pole with independent operation capability and shows higher system reliability. Operation of P-Z-N distributed bipolar system involves coordination of PZ sub-microgrid and ZN sub-microgrid. In comparison with voltage balancer...
In DC microgrid, it is common that constant power loads (CPLs) exhibit negative impedance characteristics, which degrades the stability margin of the whole system. This paper focuses on the stability problem of isolated DC microgrid with multiple DC voltage control units and constant power loads. Taking controllers into account, the detailed impedance model of DC microgrid is established, and it shows...
Increased proliferation of the renewable energy sources (RES) brings more power electronic devices to the power distribution. Modularity on the converter level is one of the key concepts enabling flexibility, scalability and high availability of the new solutions for the distribution networks(e.g. for low voltage DC). To understand the trends and performance trade-offs it is important to describe...
Cascaded H-bridge converters based islanded microgrids are applied to integrate the distributed generators (DGs). The accurate load sharing is an important task for the research of microgrids. Due to the characteristics of series connection, all DGs share a single common current. In this paper, the power factor of each DG is assigned to be consistent via regulating both the frequency and voltage....
We propose an autonomous hybrid AC/DC microgrid system that uses a triple active bridge (TAB) converter as a power routing unit. A TAB converter that can independently control transmission power among three ports is suitable for constructing the microgrid system. We made a prototype TAB converter rated at 400 V, 20 kHz, and 10 kW and demonstrated that it can control the transmission power when the...
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