A comprehensive study on low-carbon impact of distributed generations on regional power grids: A case of Jiangxi provincial power grid in China

With the problem of energy shortage and environmental pollution becoming more and more serious, the realization of full clean energy power generation has become the goal of energy development in the world. Firstly, this paper introduces the characteristics of power grid structure, clean energy development planning and power mutual aid in Europe and China, and points out the problems of limited grid carrying capacity, safety and stability, and new energy consumption faced by the high proportion of clean energy development in the Three North region of China. Based on this, taking a provincial power grid in China as an example, this paper analyzes the security and stability problems of peak load regulation, overload, frequency and voltage existing in the power grid in the phase of gradual decommissioning of thermal power and realization of full clean energy transformation, which are verified by the actual power grid. Finally, based on the experience of European power grid planning and new technology application, this paper discusses the measures and suggestions of realizing full clean energy transformation of provincial and regional power grids in China.

It is the key problem in automatic voltage control of large-scale power grids to quantitatively assess the reactive power regulation capability of provincial power grid to determine the control range of reactive power between provincial and regional power grids. Based on the concept of layered decoupling, firstly the definition of average coordination power factor limits (ACPFL) is given to evaluate the reactive power limit of provincial power grid, and the optimized mathematical model of ACPFL is solved to obtain the correlation curve between ACPFL and load level transmitted from provincial power grid to subordinate power networks; then according to the differences among loads of 500kV substations, the approximate linearization calculation of limit value of the upstream gateway coordinated power factor is performed, and taking it as the constraint a calculation model and fast estimation method for the limit value of downstream gateway coordinated power factor are established to implement dynamic setting of parameters of AVC system; finally a method to implement the AVC system based reactive power coordinated control at the gateway between provincial and regional power grids is given. Simulation results of applying the proposed method to a certain regional power grid in Guangdong power grid show that the proposed method is favorable for energy-saving and loss-reduction, improving voltage quality, enhancing security margin of voltage and reactive power in provincial power grid and bringing the potential of area substation capacity into play.

Peak shaving operation of hydro-thermal-nuclear plants serving multiple power grids by linear programming

There is a common lack of flexible power to quickly follow peak loads of many coal-dominated provincial power grids (PPGs) in China. A regional power grid (RPG) that covers several provinces is responsible for scheduling the power plants it manages and allocating their power to subordinate PPGs in response to different peak loads. This process is more difficult than conventional peak operations for a single PPG. A methodology for hydrothermal system generation scheduling considering multiple provincial peak-shaving demands is developed. This methodology utilizes a novel load subsection optimization model to smooth local frequent load fluctuations. The model divides the provincial load curve into several subsections to construct an expected residual load profile with the average load of each subsection in advance. Minimizing deviation between the expected and calculated load profiles is then formulated as the optimization objective. Three practical algorithms, named the multistep progressive optimality algorithm, the heuristic algorithm, and an improved load shedding method, are integrated to determine the power generation for hydropower plants, pumped-storage plants, and thermal plants, respectively. Moreover, a variable neighborhood search algorithm is proposed to coordinate the allocation of the power generation among PPGs. This methodology has been implemented for the operations of the East China Grid, which is the largest RPG in China. Comparisons with an existing optimization model and a conventional method are, respectively, given in two cases. The first case shows that the peak-shaving demands in subordinate PPGs are effectively met. The load fluctuations in local hours are smoothed, with an average reduction of 6.3% in allan variance of residual loads. The second case implies that the proposed method deals better with the load differences in multiple power grids. It should also be noted that the operating flexibility of different power plants has a significant effect on smoothing fluctuations in residual loads.

The installed capacity of photovoltaic generation is increasing rapidly in recent years in China. Photovoltaic generation tends to be affected by environmental conditions such as temperature and radiation. The voltage of photovoltaic plant may fluctuate simultaneously with the fluctuation of photovoltaic generation. The reactive power and voltage optimization problem is modelled as quadratic constrained quadratic programming, which helps to reduce the difficulty of program implementation and improves the reliability of optimization algorithms. The photovoltaic plant has the ability of continuous reactive power adjustment, which can quickly respond to the voltage adjustment demand of the power grid, and then reduce the adjustment times of the capacitive reactor and main transformer tap. The idea of this paper can be extended to consider the voltage control of wind farms. The proposed AVC system helps to reduce the voltage fluctuation and carbon emissions, and can be widely implemented in regional power grids in China.

Optimization of peak loads among multiple provincial power grids under a central dispatching authority

A mixed integer linear programming model for unit commitment of thermal plants with peak shaving operation aspect in regional power grid lack of flexible hydropower energy

The development of low-carbon electric power industry is a key way to deal with the greenhouse effect and lower the PM2.5. When integrated into power grid, renewable energy can efficiently cut down the output of the thermal power and reduce the carbon emission of the grid significantly. However, it lacks a more comprehensive and systematic approach to forecast a medium and long-term carbon emission for provincial power grid. Thus, in this paper, life cycle assessment (LCA) method and gray prediction model are used to forecast the medium and long-term carbon emission. In addition, the carbon intensity of provincial power grid is evaluated based on historical data such as electricity consumption, gross domestic product (GDP), carbon emission coefficient. Taking Jiangxi power grid as the example, the results indicate that the proposed method is of good accuracy and the integration of renewable energy can effectively reduce the carbon emission and the carbon intensity.

With the raise of Global Energy Interconnection, long-distance bulk energy transmission will become more and more common. In the future, multiple HVDC infeed is an important feature of receiving-end power grid in China. To improve security and stability of multi-infeed DC system, the structure of power grid should be comprehensively optimized. A modularized optimization method for power system with multiple HVDC infeed is proposed in this paper. This method includes three modules, which are HVDC termination location selection, power grid structure optimization and dynamic reactive power compensation configuration. A regional power grid in China, which is a typical multi-infeed DC system, is used as example and the effectiveness of this proposed method is validated by simulation results.

Chapter 11 - Construction of UHV Power Grids in China

Short-term peak shaving operation for multiple power grids with pumped storage power plants

Carbon neutrality is transitioning from a global consensus to global action. The power industry must urgently address carbon reduction and establish an effective evaluation system. However, current standard systems and literature studies both domestically and internationally reveal significant issues with the scientific, systematic, and operational aspects of carbon performance index systems. Therefore, this paper proposes the development of a carbon performance evaluation system for electric power enterprises, comprising of two subsystems: carbon management and carbon reduction. The evaluation system takes into full consideration the transmission and distribution characteristics of power grid companies, and conducts an empirical analysis on a regional power grid in China, including four provincial power grid companies A, B, C, and D. The findings indicate that the regional Power Grid has been committed to low-carbon initiatives for an extended period of time, with a greater emphasis on carbon reduction performance rather than carbon management performance between 2012 and 2021. To further enhance the potential for carbon reduction, it is imperative to prioritize carbon management in subsequent phases.

Currently, research on wind power integration capacity based on peak load regulation constraint is mainly aimed at provincial power grids. Regional and provincial power grids are quite different, and wind power integration capacity of provincial grids is of little reference value for regional wind power planning. In this paper, According to the basic principles of wind power capacity assessment, the maximum output factor under certain probability is taken as the regional wind power output coefficient. Then, the assessment method of wind power capacity is proposed for receiving-end and sending-end power grids, considering the interregional tie-line power adjustment and unit maintenance. Finally, the wind power integration capacity of a regional power grid is assessed as an example to prove the validity of the proposed method. Keywordswind power integration capacity; regional power grid; peak load regulation constraint; tie-line power adjustment; unit maintenance.

Real-time operation risk assessment of power grid is not only an important content of power grid dispatching and operation control, but also an important reference factor in power grid accident disposal. It is difficult for the traditional evaluation methods to meet power system online operation control requirements, because of their complex process and long calculation time. To this end, a real-time power grid operation risk assessment method based on random forest intelligent algorithm is proposed in this paper, The basic concepts and implementation points of random forest algorithm is introduced. The implementation framework of real-time operation risk assessment based on random forest is proposed taking the need of power grid operation risk assessment into consideration. Compared with the traditional evaluation method, this method can calculate the power grid operation risk level directly according to some key operation indexes without complex power grid analysis, such as N-1 security check. Finally, the two-years practical application in a certain provincial power grid in China shows that the method has high evaluation accuracy and computational efficiency, which can match the traditional evaluation method and improve the calculation efficiency and accuracy of risk assessment.

Since the power generation structures and load characteristics in each province in China are quite different, the distribution of peak regulating resources and demands are extremely imbalance. Restricted by a low power marketization degree, peak regulating resource shortages, and transmission channel blocks, the efficient utilization of new energy is facing greater pressures. In order to improve the mutual aid in regional power grids and to obtain more precise simulation results, this paper proposes a two-layer optimization dispatching model, considering the mutual aid of peak regulation resources between each province. It determines the optimal startup mode and the units’ power output in each province and obtains the power output arrangements for all the units and the technical and economic indicators. The model and the solution method are original and innovative. And it effectively solved the unequal distribution problem between the peak regulating demands and resources of each provincial power grid. Finally, taking an actual regional power grid in China as an example, the simulation results show that the proposed model can significantly improve the utilization rate of new energy, which verifies the effectiveness and feasibility of the proposed model and methods presented in this paper.