Henrik W. Bindner

An overview of trends in distribution network planning: A movement towards smart planning

Distribution network planning, historically known as a ‘predict and provide’ process, seeks to determine a set of optimal network solutions for supplying electric demands spatially distributed over a geographic area. Today, the rapid development and deployment of distributed generation and smart grid products (e.g., control, communication, and new economic measures) call for urgent improvements in distribution network planning to allow the utilities to proactively modernize their existing distribution grids. This paper reviews the current practices in this area and the emerging trends towards smart planning. Some challenges with smart planning are identified and briefly discussed.

Network constrained transactive control for electric vehicles integration

Electric vehicles (EVs) are commonly recognized as smart grid assets in addition to their environmental benefits. However, uncoordinated charging or sole cost minimization based charging of electric vehicles may bring undesirable peak demands and voltage violations in the distribution system. This paper applies the transactive control concept to integrate electric vehicles into the power distribution system with the purpose of minimizing the charging cost of electric vehicles as well as preventing grid congestions and voltage violations. A hierarchical EV management system is proposed where three actors are considered: distribution system operator (DSO), fleet operators and EV owners. In the lower level of the hierarchy, the fleet operator centrally manages the charging schedule of electric vehicles; in the upper level of the hierarchy, the DSO uses transactive control technique to coordinate the aggregated charging behavior of fleet operators. Detailed models are presented to illustrate the operation of the hierarchical EV management system. In the end, simulations are presented to show the effectiveness of the proposed solutions.

Identification of requirements for distribution management systems in the smart grid context

The integration of significant volumes of distributed and renewable energy resources directly connected to the distribution network raises new requirement to maintain and operate the power system in secure state. Thus the Distribution Management System (DMS) needs to be updated and integrated with new functionality to provide effective support for the operators. The DMS is a control center solution that provides the needed functionality for the management of medium and low voltage distribution networks. This paper aims to provide an overview of the main functions present in todays DMS platforms and to identify the new requirements to better serve in a smart grid context.

Activate distributed energy resources' services: Hierarchical voltage controller as an application

The flexibilities from controllable distributed energy resources (DERs) offer the opportunities to mitigate some of the operation problems in the power distribution grid. The provision of system services requires the aggregation and coordination of their flexibilities, in order to obtain the flexible capacity of large scale. In this paper, a hierarchical controller is presented to activate the aggregation, and tries to obtain a global optimum of the grid operation. A distribution grid with large penetration of highly varying generation or load is under the risk that the voltage quality delivered to the end users is very poor. Hence, a coordinated voltage control function is investigated given such control hierarchy utilizing the flexibilities from the DER units to obtain an optimal voltage profile along the distribution feeder. The results are two folded: the controller enables the efficient aggregation and dispatch, and it simplifies the optimization complexity; the involvement of DER flexibilities in voltage services can significantly improve the voltage quality and reduce the grid power loss without additional regulating devices.

Hybrid control scheme for distributed energy resource management in a market context

In modernizing the electricity grid, distributed energy resources (DERs) can play an important role in accommodating intermittent energy sources, assisting system operation and the transition to a smart grid. Proper aggregation and coordination of the available DER units is required to provide flexibility to meet regular demand from the distribution system operator (DSO). By considering both their physical constraints and the economical system operation, this paper proposes a realtime hybrid management system for DER units in a market environment, which considers both the request from the DSO and their local conditions. Voltage regulation service is formulated and implemented in the control frame. The performance is evaluated through simulation on an existing Danish MV and LV distribution grid and is compared with a local control method and the passive operation condition.

Assessment of distribution grid voltage control strategies in view of deployment

Increasing integration of distributed energy resources (DER) and available monitoring devices in the power distribution grid make system services provided by DERs possible and an integral part of distribution grid operation. Numerous publications have proposed various control solutions by utilizing different capabilities of DERs and regulating devices to assist grid operation. However, very few of them have discussed the opportunities and barriers of deploying the control strategies in practice. This paper reviews some typical control solutions on providing voltage control services. Furthermore, it provides some qualitative discussions on the challenges in view of deployment. Several qualifying metrics are listed to specify the challenges from different perspectives. A metrics comparison diagram is proposed to asses deployment of a control strategy. Five case studies are presented to identify the corresponding advantages and challenges of deployment.

Coordinated voltage control scheme for distribution grid with on-load tap-changer and distributed energy resources in a market context

The evolutionary changes in the electricity system are reshaping the system operation and control to achieve a more sustainable environment. In this transition, distributed energy resources (DERs) may introduce some problems, such as intermittent features, but could also play an important role on accommodating the intermittence and assisting system operation. A proper aggregation and coordination scheme of DER units is required to enable the flexibility provision in an economical and efficient manner. In the meanwhile, nondistruptive control of the units is essential to guarantee their long-term active participation. In addition, a newly established system should also allow and coordinate other controllable grid facilities. This paper proposes a hierarchical operating framework for DER units and controllable grid assets in a market environment. Voltage regulation as a common distributed system service is used for case study. The necessity of the coordination between DER units and the grid facilities, e.g., on-load tap-changer (OLTC), is addressed.

Improved power quality monitoring through phasor measurement unit data interpretation

The observability needs in future power systems will change radically due to the continuing implementation of renewable energy sources at all voltage levels. Especially in distribution grids new observables will be needed in order to monitor the state of the power system sufficiently and to perform the correct actions for operating the system. In future power systems more measuring sensors including phasor measurement units will be available distributed all over the power system. They can and should be utilized to increase the observability of the power system. In this paper the impact of photovoltaic and wind power production on the voltage unbalance was analyzed. PMU data and NTP-synchronized data from two different MV networks were used. It has been found that PV production has only a minor negative impact on the voltage unbalance whereas the wind power production has a great positive impact. The voltage unbalance factor (VUF) could be a `new observable for a particular power system condition. Information about the actual injected wind power for a certain grid area could be derived without knowing/measuring the real wind power injection.