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With the advancements of the battery energy storage systems (BESSs), reduction of their manufacturing costs and government subsidies, the BESS uptake is likely to increase rapidly in power distribution networks. This paper investigates the effects of residential BESSs on low-voltage (LV) networks using the actual household load profiles equipped with BESS and solar-photovoltaic (PV) systems. The electricity consumption data collected via smart meters (2200 households with PV/BESS, 1950 households with PV only and 1000 households without a PV or a BESS) at different solar-PV penetration levels and network types are used to simulate real network operating scenarios. A real LV distribution network in Australia is analysed in DIgSILENT PowerFactory under different scenarios, such as, customers with and without a solar-PV/BESS, with a solar-PV but without a BESS, and without a solar-PV, by using both the power flow and quasi-dynamic simulation studies under balanced and the unbalanced network loading conditions. According to the study, customers experience large voltage excursions from solar-PV power exports, which could be resolved by the household BESS, provided that the BESS charging is coordinated with the solar-PV production. Moreover, quasi-dynamic simulation shows that the BESS could reduce the violation of the over-voltage limit during the solar peak hours (midday) by lowering the worst-case feeder voltage by 3%. Finally, extreme-event (high solar PV generation scenario) simulation shows that the implementation of the BESS controller to facilitate charging BESS during afternoon solar-PV export may reduce the negative grid impact and will assist to avoid network upgrades. [ABSTRACT FROM AUTHOR]

Series-cascaded microgrids (MGs) are gaining increasing popularity because of their control flexibility and ability to synthesize high voltage levels from low power rated modules. Several control schemes have been reported for autonomous power sharing in series-cascaded MGs that incorporate dispatchable distributed generators (DGs) only. In contrast, this article develops a series-cascaded MG formed by dispatchable and nondispatchable DGs. Achieving power balance as well as voltage and frequency regulation in this MG configuration is a challenging task. In this article, we propose a decentralized master–slave control scheme that regulates voltage and frequency and maintains power balance. The proposed scheme ensures the maximum utilization of nondispatchables, incorporates autonomous power curtailment under light-load conditions, and offers system reliability comparable with the traditional parallel structure. The proposed MG configuration and control scheme are thoroughly validated via simulations and experiments under various operating scenarios. [ABSTRACT FROM AUTHOR]

This paper proposes and investigates a novel near-optimal finite-control-set model predictive control (NOP-MPC) algorithm to control the grid-connected, pulsewidth-modulator-driven voltage source converters with LCL filters. Exploiting the convex and elliptical paraboloid properties of the cost error, NOP-MPC adopts a systematic iterative algorithm within each control cycle to progressively synthesize finite sets of virtual voltage vectors (VVs) for the control optimization stage. The synthesis has the inherent features of respecting the converter voltage limits and converging the sets of VV candidates toward the global optimal point. The fixed-switching-frequency feature of NOP-MPC is expected to ease the LCL filter design. Effects of computational delay, pulsewidth modulation delay, and deadtime are considered and compensated successfully. A two-vector-variable cost function is used to actively damp the inherent LC resonance through an adjustable, weighting-factor-based damping level. This paper is substantiated by theoretical consideration, simulation and experimental results, parameter sensitivity study, and a comparative study with the standard finite-control-set model predictive control that uses only actual VVs. [ABSTRACT FROM AUTHOR]

Decentralized economic operation schemes have several advantages when compared with the traditional centralized management system for microgrids. Specifically, decentralized schemes are more flexible, less computationally intensive, and easier to implement without relying on communication infrastructure. Economic operation of existing decentralized schemes is also usually achieved by either tuning the droop characteristics of distributed generators (DGs) or prioritizing their dispatch order. For the latter, an earlier scheme has tried to prioritize the DG dispatch based on their no-load generation costs. Although the prioritization works well with some generation costs saved, its reliance on only the DG no-load generation costs does not allow it to operate well under certain conditions. This paper thus presents a more comprehensive economic dispatch scheme, which considers the DG generation costs, their power ratings, and other necessary constraints, before deciding the DG dispatch priorities and droop characteristics. The proposed scheme also allows online power reserve to be set and regulated within the microgrid. This, together with the generation cost saved, has been verified experimentally under different reserve, load, and DG conditions. [ABSTRACT FROM PUBLISHER]

This paper presents two linear power sharing schemes for distributed generators (DGs). The purpose is to reduce the total generation cost (TGC) of the considered autonomous microgrid. The saving in cost is realized by tuning the DG droop gradients in accordance to their respective maximum or mean generation costs. Compared with the existing nonlinear cost-based schemes, the proposed schemes use linear droop functions, which are easier to tune and implement in practice for a greater reduction in TGC. The proposed schemes have been tested experimentally with an example microgrid powered first by dispatchable DGs only, and then by a combination of dispatchable and nondispatchable DGs. Experimental results obtained have demonstrated the anticipated outcomes under different operating conditions. [ABSTRACT FROM AUTHOR]

This paper presents two cost-prioritized droop sche- mes for distributed generators (DGs) in a rural or islanded microgrid. Dispatch prioritization of the schemes allows autonomous identification of the appropriate DGs for generation, in accordance to the overall load conditions of the microgrid. The result is a lower total generation cost for the microgrid when compared to other droop schemes. An experimental system has been implemented and tested with results showing a higher saving achieved by the proposed schemes. [ABSTRACT FROM AUTHOR]

Droop schemes have traditionally been applied to the control of parallel synchronous generators in power systems. It has subsequently been brought over to the control of distributed generators (DGs) in microgrids with the same retained objective of proportional power sharing based on ratings. This objective might, however, not suit microgrids well since DGs are usually of different types, unlike synchronous generators. Other factors like cost, efficiency, and emission penalty of each DG at different loading must be considered since they contribute directly to the total generation cost (TGC) of the microgrid. To reduce this TGC without relying on fast communication links, an autonomous droop scheme is proposed here, whose resulting power sharing is decided by the individual DG generation costs. Comparing it with the traditional scheme, the proposed scheme retains its simplicity and it is hence more likely to be accepted by the industry. The reduction in TGC has been verified by experiment. [ABSTRACT FROM PUBLISHER]

Although many droop schemes have been proposed for distributed generator (DG) control in a microgrid, they mainly focus on achieving proportional power sharing based on the DG kVA ratings. Other factors like generation costs, efficiencies, and emission penalties at different loads have not been considered even though they are different for different types of DGs. This letter thus proposes an alternative droop scheme, which can better distinguish the different operating characteristics and objectives of the DGs grouped together in a weighted droop expression. The power sharing arrived in the steady state will meet the intended objectives, as demonstrated in the experiment with a defined objective of minimizing the total microgrid operating cost. [ABSTRACT FROM AUTHOR]

Microgrids are small grids formed by clustering modern generating sources, storage systems, and loads together. Being independent, the formed microgrids can, in principle, operate at their own preferred voltages and frequencies. Tying them to the mains grid or another microgrid would therefore require some interlinking power converters, whose control should preferably be autonomous without depending on fast communication links. Contributing to this theme of research, a distributed power management scheme has been proposed in this paper for interlinking two or more independent microgrids operating at different voltages and frequencies. The proposed scheme allows sources in the microgrids to concentrate more on active power harnessing, while the interlinking converters focus more on meeting the load reactive demand. If necessary, backup active power from an underloaded microgrid can also be transferred to an overloaded microgrid, allowing it to supply loads in excess of its rated capacity. The performance of the proposed scheme has already been tested in experiment. [ABSTRACT FROM AUTHOR]