This paper maps the expected and possible adverse consequences for power quality of introducing several smart distribution-grid technologies and applications. The material presented in this paper is the result of discussions in an international CIGRE-CIRED joint working group. The following technologies and applications are discussed: 1) microgrids; 2) advanced voltage control; 3) feeder reconfiguration; and 4) demand-side management. Recommendations are given based on the mapping.

In this paper, a novel configuration of a three-level neutral-point-clamped (NPC) inverter that can integrate solar photovoltaic (PV) with battery storage in a grid-connected system is proposed. The strength of the proposed topology lies in a novel, extended unbalance three-level vector modulation technique that can generate the correct ac voltage under unbalanced dc voltage conditions. This paper presents the design philosophy of the proposed configuration and the theoretical framework of the proposed modulation technique. A new control algorithm for the proposed system is also presented in order to control the power delivery between the solar PV, battery, and grid, which simultaneously provides maximum power point tracking (MPPT) operation for the solar PV. The effectiveness of the proposed methodology is investigated by the simulation of several scenarios, including battery charging and discharging with different levels of solar irradiation. The proposed methodology and topology is further validated using an experimental setup in the laboratory.

As distribution networks become increasingly variable and generation becomes increasingly decentralised, voltage standards are becoming more liable to violation. Accordingly, intelligent voltage management strategies are required to enable standards compliance without unduly increasing network maintenance or infrastructure costs. The relationship between network power and voltages, however, is complex, non-linear and interdependent, and thus is difficult to conceptualise and use for decision-making and control purposes. This paper introduces a software toolkit that simplifies the development of voltage management strategies by the application of sensitivity analysis. Sensitivity analysis reduces complex network P - Q - |V| relationships to simple linear equations, and thus enables easy and comprehensive conceptualisation of the effect of network modifications. Sensitivity data is obtained through a unique `perturb-and-observe' algorithm built on top of an open-source simulation package. The toolkit enables the rapid development of sensitivity-driven network experimentation and is highly extensible. A number of applications that demonstrate the usefulness of these techniques are presented, including the development of a reactive power control algorithm for the mitigation of inverter-based, distributed generation (DG)-induced voltage rise, and the verification of voltage-support-capacitor-bank placement for a real Australian semi-rural network. Finally, this paper presents some suggestions for possible future applications of data-driven, simulator-augmented sensitivity analysis techniques.

Microgrid systems located within commercial premises are becoming increasingly popular and their dynamic behavior is still uncharted territory in modern power networks. Improved understanding in design and operation is required for the electricity utility and building services design sectors. This paper evaluates the design requirements for a commercial building microgrid system to facilitate seamless mode transition considering an actual commercial building microgrid system. A dynamic simulation model of the proposed microgrid system is established (utilizing DIgSILENT Power Factory) to aid the development of planning and operational philosophy for the practical system. An economic operational criterion is developed for the microgrid to incorporate selective mode transition in different time intervals and demand scenarios. In addition, a multi-droop control strategy has been developed to mitigate voltage and frequency variations during mode transition. Different system conditions considering variability in load and generation are analyzed to examine the responses of associated microgrid network parameters (i.e., voltage and frequency) with the proposed mode transition strategy during planned and unplanned islanding conditions. It has been demonstrated that despite having a rigorous mode transition strategy, control of certain loads such as direct online (DOL) and variable-speed-drive (VSD) driven motor loads is vital for ensuring seamless mode-transition, in particular for unplanned islanding conditions.

Frequency support from renewable power generators is critical requirement to ensure the frequency stability of remote area pow-er supply (RAPS) systems with high penetration of renewable power generation. However, traditional control strategies and the stochastic nature of wind resource constrain wind energy conver-sion system (WECS) such as permanent magnet synchronous generator (PMSG) from participating in frequency regulation. This work proposes to integrate hybrid energy storage including ultracapacitors (UCs) and lead-acid batteries (LABs) into a PMSG to provide frequency support. The UCs deal with fast changing frequency by emulating conventional inertial response, whereas the LABs mimic automatic governor response (i.e., pri-mary frequency response). The mechanical power reserved in wind turbine using suboptimal maximum power point tracking (SOPPT) strategy is utilized to restore system frequency (i.e., sec-ondary frequency response). Moreover, supplementary control strategies are proposed to enable the UCs and LABs to assist primary frequency response and secondary frequency response respectively. Simulation study and experimental test are carried out to validate the effectiveness of frequency response provided by the multilevel energy storage. The multilevel energy storage solution can effectively regulate RAPS system frequency while avoiding abrupt and frequent charging/discharging of the LABs and significant mechanical/electromagnetic stress on the WECS.