Risk Assessment of Smart Grid Dispatching Considering Flexible Load

To strengthen the integration of the primary and secondary systems, a concept of Cyber Physical Systems (CPS) is introduced to construct a CPS in Power Systems (Power CPS). The most basic work of the Power CPS is to build an integration model which combines both a continuous process and a discrete process. The advanced form of smart grid, the Active Distribution Network (ADN) is a typical example of Power CPS. After designing the Power CPS model architecture and its application in ADN, a Hybrid System based model and control method of Power CPS is proposed in this paper. As an application example, ADN flexible load is modeled and controlled with ADN feeder power control by a control strategy which includes the normal condition and the underpowered condition. In this model and strategy, some factors like load power consumption and load functional demand are considered and optimized. In order to make up some of the deficiencies of centralized control, a distributed control method is presented to reduce model complexity and improve calculation speed. The effectiveness of all the models and methods are demonstrated in the case study.

As the proportion of flexible load resources in smart grids continues to rise, resulting in increasingly complex grid structures, significant changes in grid characteristics, and increased risks to grid operation and control, it will be difficult to intelligently regulate the grid solely by relying on traditional resource regulation methods, and the dispatchable space for traditional resources will become smaller and smaller. To this end, this paper conducts an exploratory investigation on the modeling techniques for flexible loads participation in smart grid dispatching. First, a classification of the flexible loads involved in grid regulation is made. Secondly, according to the flexible load classification, the modeling techniques of different classes of flexible loads are reviewed and studied; then, the flexible load dispatching modes for different operating states and different control tasks, and under different control methods are discussed deeply. Moreover, the technological economics and feasibility of these different flexible load dispatching modes are compared. Finally, an outlook and conclusion are made.

In view of the distribution network operation problems caused by many distributed generations integration to distribution network, and the increasingly serious peak valley imbalance in grid, this paper proposes a coordinated control system of source-network-load-storage based on virtual power plant technology, which is designed and implemented in the actual project. The system uses cloud platform technology and multi-energy complementary technology to realize coordination and optimization control mechanism between sources, network and loads in regional distribution network. The system is based on the distribution Internet of things cloud master platform. Through the virtual power plant technology, resources such as cogeneration, photovoltaic, wind, distributed energy storage, electric vehicles, flexible loads are aggregated to achieve coordinated and unified control, realize the optimal operation of multi-energy complementary. It can accept the control of the dispatching center, and participate in the power transaction of demand response. Based on the application scenario, this paper explains how to use virtual power plant technology to participate in demand response power transaction, and describes the transaction rules and processes. The system is beneficial to the safety and reliability of the distribution network. It can implement reasonable configuration and consumption of distribution generations. It can control controllable loads such as electric vehicle charging pile to participate in peak regulation of power grid, and provide strong technical support for the realization of demand response.

Big data technology is currently a real research hotspot in every field. Based on the big data technology, this paper discussed its application in distribution network operation and control. Firstly, the significance was illuminated that big data technology would bring into the development of power distribution system and this paper also has made a brief conclusion on the current application situation of big data technology in power distribution system, and analyze problems and optimization methods in the current distribution network operation and control. Then, based on big data technology, advanced operation management, maintenance arrangement, network planning and asset management in power distribution network was analyzed, and the distribution network aided decision-making platform was researched. Finally, the application of distribution network aided decision-making platform was explained in situation analysis and loads forecasting, and some suggestions were made to stimulate the development of big data and other big data-based applications in power distribution system have also been conjectured.

This paper shows that the smart loads could be effective in mitigating voltage problems caused by photovoltaic (PV) generation and electric vehicle (EV) charging in low voltage (LV) distribution networks. Limitations of the previously reported smart load configuration with only series reactive compensator (SLQ) (one converter) is highlighted in this paper. To overcome these limitations, an additional shunt converter is used in back-to-back (B2B) configuration to support the active power exchanged by the series converter, which increases the flexibility of the smart load without requiring any energy storage. Simulation results on a typical UK LV distribution network are presented to compare the effectiveness of a smart load with B2B converters (SLBC) against an SLQ in tackling under- and over-voltage problems caused by EVs or PV. It is shown that SLBCs can regulate the mains voltage more effectively than SLQs especially, under over-voltage condition. Although two converters are required for each SLBC, it is shown that the apparent power capacity of each converter is required to be significantly less than that of an equivalent SLQ.

Aiming at the problem that customer satisfaction with electricity consumption will affect the implementation effect of demand response. This paper proposes a virtual power plant scheduling model considering the satisfaction of users with different flexible loads. Firstly, the flexible load is divided into three categories: reducible load, transferable load and substitutable load. By analyzing the factors that affect the satisfaction of electricity consumption, the satisfaction models of customers with different flexible loads are constructed respectively. Secondly, a virtual power plant scheduling model considering different flexible load demand response models is established. Finally, the scheduling model is simulated and solved based on MATLAB, and the validity of the proposed virtual power plant scheduling model considering the satisfaction of users with different flexible loads is verified.

Voltage control in distribution networks becomes increasingly important with an increasing penetration of distributed generation (DG). As distribution networks are much more resistive than transmission networks, the conventional technique of reactive power compensation in order to control the voltage cannot be applied very well. For that reason other voltage control techniques have to be applied. In this contribution several options for voltage control in distribution networks are analyzed and related to important grid parameters such as the short-circuit ratio and the X/R ratio of the grid. For networks with a high X/R ratio reactive power can be used for voltage control. For networks with a low X/R ratio several new voltage control techniques are proposed. These techniques are voltage control with active power, inserting a controllable inductance in the grid and series compensation by DG unit converters.

This paper studies the participation of doubly-fed induction wind generator (DFIG), as a continuous variable, in dynamic optimization of reactive power and voltage control in the distribution network by obtaining the reactive power capability through controlling the power electronic interfaces and taking DFIG rated parameters into accounts. Given the fluctuation in the DFIG output active power, a time partition method based on the variance of the DFIG output active power has been proposed. According to the results of the time partition method, the operational requirements and the characteristics of the control variables in the distribution network, different dynamic optimization algorithms have been applied in different optimization time. The simulation based on the improved IEEE 33-bus system has been conducted to validate the effectiveness of the proposed optimization strategy.

LofoSwitch: An online policy for concerted server and disk power control in content distribution networks

Control mode of distribution power grid dispatching was studied and frame of ‘Generation-Grid-Load-Energy storage’ (GGLE) coordinating control system was built. This system took controlling resources into regulative scope such as distributed energy source, energy storage system and flexible load. On this basis, coordinated optimizing control strategy such as multi-source information fusion, feeder level load forecasting and operation control of distribution network was designed, thus enhancing the safe and reliable operation of active distribution network and diversifying the ability of load to participate in peak load regulation of power grid, which contributed to the reasonable allocation and consumption of distributed power supply. The GGLE coordinated control system has been successfully constructed in a 10kV switching station on Ninghai Avenue in Qinhuangdao, realizing a reasonable control of energy and load, and improving of the energy efficiency and power distribution reliability. The pilot project could be a basic guidance for large-scale construction of active distribution grid.

With numerous diverse flexible loads widely connected to power grid, the heterogeneity of flexible loads has become difficult to adapt to the large-scale power balance demand of the power grid. Optimal configuration of energy storage considering the heterogeneous flexible loads is the key to realize the power balance of the regional power grid. Firstly, based on the differentiated characteristics and power consumption curve of heterogeneous loads, the heterogeneous loads are classified as transferable loads, cuttable loads and adjustable loads. Then, the coordinated optimization strategy is proposed for heterogeneous loads and multi-type energy storages. the optimal configuration of multi-type energy storages is achieved by mixed integer linear programming (MILP). Finally, compared to flexible loads or energy storages participating in grid regulation alone, the proposed optimization strategy can not only achieve power balance of the regional grid, but also reduce the system operation cost and improve the economic benefits of the grid.

Intelligent optimal scheduling strategy of IES with considering the multiple flexible loads

Optimal control of water distribution networks without storage

After integrating distributed generators (DGs), the voltage/var control in distribution networks requires addressing multiple objectives, including power loss reduction, lifetime saving of mechanical switching voltage control devices and uncertain power output of DGs. Therefore, this paper proposes a two-stage voltage/var control method for distribution networks with uncertain power generation from DGs. A dynamic voltage/var optimisation model is formulated in the primary optimisation stage. It dispatches all the voltage/var controllers to minimise the action times of mechanical switching devices and the total active power loss over the day. The second stage consists of a stochastical optimisation model in which probabilistic scenarios replace the deterministic parameters of DGs and loads. The Monte Carlo approach and K-mean clustering technic are utilised to generate the scenarios to be used in the second stage. The DGs’ setpoints are recursively calculated to address the uncertainties. The proposed method is tested on a modified IEEE 33-node distribution network. The effectiveness of the method is demonstrated through the simulation results.

Optimum VAR control of radial primary power distribution networks by shunt capacitor installation