Typical Scenarios and Technical Requirements of China’s Power Grid towards 2030 for Power System Transformation

A large number of applications of distributed energy storage, electric vehicles, air conditioning and other flexible resources provide abundant adjustable resources for the power grid. It is of great significance to realize the aggregation of multiple kinds of load-side resources, give play to the flexibility and complementarity of resources, and improve the adjustment ability of load-side resources. This paper proposes a load side resource aggregation method considering complementary characteristics and scenario requirements. Firstly, based on the correlation theory and the regulation characteristic theory, the complementary characteristic indexes including the regulation capacity complementarity rate, the response speed complementarity rate and the dispatch duration ratio complementarity rate were proposed. Then, by Revolving Door Algorithm, the daily load curve was analyzed in segments to obtain the periods of three typical balance scenes of power grid, namely, climbing, peaking and valley filling, and analyze the characteristics of the scene demands. Based on the comprehensive consideration of the resource regulation potential of multiple types of load side, combined with the demand characteristics of scenarios such as peak cutting and valley filling and climbing, load side resources were screened and aggregated with the target of scene fitness to obtain the load persistence curve (resource pool) of different typical scenarios in this period. Finally, simulation verification was carried out on the actual power grid example of a region. The load duration curves of load side resources for different typical power grid balance scenarios are obtained to provide technical support for power grid regulation decision.

A high-quality set of typical scenarios is significant for power grid planning. Existing construction methods for typical scenarios do not account for the spatiotemporal correlations among renewable energy plant outputs, failing to adequately reflect the distribution characteristics of original scenarios. To address the issues mentioned above, this paper proposes a construction method for typical scenarios considering spatiotemporal correlations, providing high-quality typical scenarios for power grid planning. Firstly, a symmetric spatial correlation matrix and a temporal autocorrelation matrix are defined, achieving quantitative representation of spatiotemporal correlations. Then, distributional differences between typical and original scenarios are quantified from multiple dimensions, and a scenario reduction model considering spatiotemporal correlations is established. Finally, the genetic algorithm is improved by incorporating adaptive parameter adjustment and an elitism strategy, which can efficiently obtain high-quality typical scenarios. A case study involving five wind farms and fourteen photovoltaic plants in Belgium is presented. The rate of error between spatial correlation matrices of original and typical scenario sets is lower than 2.6%, and the rate of error between temporal autocorrelations is lower than 2.8%. Simulation results demonstrate that typical scenarios can capture the spatiotemporal correlations of original scenarios.

With the increasing proportion of renewable energy units in the power grid, in order to better plan the operation of the power system, it is necessary to predict and simulate the typical application scenarios of renewable energy. The medium and long-term planning and economic operation optimization of power system need to construct typical scenarios through historical data that can reflect the characteristics of renewable energy. In this paper, a renewable typical scenario construction method based on improved FCM clustering algorithm is proposed and applied to renewable energy absorption capacity assessment of power system with renewable energy. Taking a regional power grid in China as an example, the performance of scenario construction method based on improved clustering algorithm, annual time series method and typical day method is compared in the field of power system operation cost optimization. The results show that the improved clustering algorithm used in this paper has both computational accuracy and efficiency, and has practical application value.

Given the lack of distributed PV power generation operation and management capability, this paper profoundly analyzes the current situation of the application of big data technology in the process and management of PV power generation in China and proves the necessity and importance of promoting new equipment, new technology, and new mode based on traditional power system operation and management, using the extensive data information formed in the process and management of power plants, meteorology, environment, and power grid, and launching ample data analysis research. In addition, the typical application scenarios of big data technology in the operation and management of distributed PV power generation are explored, and a new mode of operation and management of distributed PV power generation at the power plant, grid, and government levels is explored and constructed. The study shows that with the dramatic increase in the number of distributed PV power generation, the use of big data technology in scenarios such as the power generation side and grid side has excellent potential to provide adequate support for PV power generation operation, grid scheduling, market-based transaction settlement, and government decision-making.

With the development of intelligent modern power systems, real-time sensing and monitoring of system operating conditions have become one of the enabling technologies. Due to their flexibility, robustness and broad serviceable scope, wireless sensor networks have become a promising candidate for achieving the condition monitoring in a power grid. In order to solve the problematic power supplies of the sensors, energy harvesting (EH) technology has attracted increasing research interest. The motivation of this paper is to investigate the profiles of harnessing the electric and magnetic fields and facilitate the further application of energy scavenging techniques in the context of power systems. In this paper, the fundamentals, current status, challenges, and future prospects of the two most applicable EH methods in the grid—magnetic field energy harvesting (MEH) and electric field energy harvesting (EEH) are reviewed. The characteristics of the magnetic field and electric field under typical scenarios in power systems is analyzed first. Then the MEH and EEH are classified and reviewed respectively according to the structural difference of energy harvesters, which have been further evaluated based on the comparison of advantages and disadvantages for the future development trend.

Nowadays with enlargement of power grid and increasing renewable energy integration, uncertainties and randomness challenge traditional power system analysis methods. Scenarios are widely applied to deal with power system uncertainties. Especially power flow examination in transmission expansion planning needs typical scenarios to verify normal power flow, and provide useful information for auxiliary planning strategies by studying typical extreme scenarios. In order to perform large-scale and multidimensional scenario analysis in power flow examination, this paper proposes an improved initial-center-refined and weighted K-means (ICRW K-means) method to improve efficiency and reduce computational time. Taking extreme scenarios into account, an extreme scenario reduction method is presented to retain typical extreme scenarios, maintaining more features of scenario reduction results. A real network is studied using proposed ICRW K-means and extreme scenario reduction method to perform power flow examination in transmission expansion planning. Numerical results demonstrate the effectiveness of proposed method, providing suggestions for auxiliary planning strategies to enhance power grid in resisting extreme conditions and reducing economic losses.

With renewable energy sources (RESs) highly penetrating into the power system, new problems emerge for the independent system operator (ISO) to maintain and keep the power system safe and reliable in the day-ahead dispatching process under the fluctuation caused by renewable energy. In this paper, considering the small hydropower with no reservoir, different from the other hydro optimization research and wind power uncertain circumstances, a day-ahead scheduling model is proposed for a distributed power grid system which contains several distributed generators, such as small hydropower and wind power, and energy storage systems. To solve this model, a two-stage stochastic robust optimization approach is presented to smooth out hydro power and wind power output fluctuation with the aim of minimizing the total expected system operation cost under multiple cluster water inflow scenarios, and the worst case of wind power output uncertainty. More specifically, before dispatching and clearing, it is necessary to cluster the historical inflow scenarios of small hydropower into several typical scenarios via the Fuzzy C-means (FCM) clustering method, and then the clustering comprehensive quality (CCQ) method is also presented to evaluate whether these scenarios are representative, which has previously been ignored by cluster research. It can be found through numerical examples that FCM-CCQ can explain the classification more reasonably than the common clustering method. Then we optimize the two stage scheduling, which contain the pre-clearing stage and the rescheduling stage under each typical inflow scenario after clustering, and then calculate the final operating cost under the worst wind power output scenario. To conduct the proposed model, the day-ahead scheduling procedure on the Institute of Electrical and Electronics Engineers (IEEE) 30-bus test system is simulated with real hydropower and wind power data. Compared with traditional deterministic optimization, the results of two-stage stochastic robust optimization structured in this paper, increases the total cost of the system, but enhances the conservative scheduling strategy, improves the stability and reliability of the power system, and reduces the risk of decision-making simultaneously.

Although China's new energy power generation industry has developed, how to efficiently use clean energy and ensure safe supply needs further research. As a clean, pollution-free and high calorific value energy, hydrogen provides a solution for absorbing renewable energy and ensuring the stable operation of the power system. Based on the public goods attribute of system security and system operation behavior, this paper analyzes how to express the cultural value of energy supply security through economic means, and makes configuration adjustment under different interaction modes with the power grid, so as to achieve the effect of energy supply security. A multi-objective planning and operation optimization model is established, and the resource, social, economic and environmental benefits are analyzed. The model is solved by NSGA-II. The results show that the energy waste rate of hydrogen microgrid system can be reduced by 37.16%. The probability of power failure can be reduced to 0. Typical scenarios in both off-grid mode and grid-connected mode can increase economic income. In addition, up to more than 1000 tons of carbon emissions per day could be reduced under a typical scenario.

With the transformation from smart grid to power Internet of Things, new power businesses such as power grid automation and power quality monitoring are constantly emerging. The load environment of power grid is changeable. In order to meet the needs of multi-service, the integrated access scheme for power grid resources in power enterprises is gradually diversified, which brings challenges to the unified management and control of power grid communication network. In this paper, SDN technology is used to improve the operation and maintenance management and control of power communication network, which aims at the integration scheme of power grid resources in power enterprises. Based on the controller cluster technology, combined with the new power business requirements, this paper designs a software-defined network centralized control architecture of the new business of power communication network. The architecture realizes the operation and maintenance management of network resources under the centralized control architecture of typical enterprise scenarios, such as power grid enterprises. The convergence speed is improved by 27%. The minimum value of iterative convergence is 31% better than that of other methods. The system requirement is reduced by 13.5%, which is helpful to improve the efficiency of node dynamic allocation and ensure the need of large-capacity data transmission of smart grid. The research in this paper can realize the two-way interaction, real-time expansion and unified deployment of power business in the future, and promote the intensive and lean development of power communication network.

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Automated control equipment is being progressively integrated into the power grid. Automated process control in the electric power industry involves the ability to control the position of electrical switching devices, monitor their current status, as well as display numeric data on currents, voltages, etc. Disruptions in the automated operations control facilities (AOCF) cause defects in power systems and grid equipment. AOCF failures impair condition monitoring of power grids and operation of switching devices. Due to the impossibility of real-time remote management of power supply installations, the power provider is unable to guarantee continuous power supply. The article analyzes the AOCF equipment currently in operation as part of distributed systems at power substations, looks into the advantages and drawbacks of specific facilities, suggests methods to increase the dependability of equipment operation in the context of a 35-110 kV distributed power supply network. An AOCF equipment certification procedure is proposed. It is also suggested to provide process control documentation for power supply facilities that contain operator process control facilities (OPCF). The documentation is to be stored in maintenance areas as hard copies and at the IT portal as scans. The availability of the documentation at power supply facilities increases labor productivity of engineering personnel that perform operational checks and accident recovery activities. Apart from the mandatory set of substation documents (for the operational, maintenance and RPEA personnel), it is suggested to equip substations with OPCF equipment diagrams. This optimization minimizes time expenditures and errors made during maintenance and repair activities on automated supervisory and process equipment at power supply facilities. That enables remote management of systems operation recovery (power supply, resetting of sensors, controllers, data collection and communication devices, etc.). The efficiency of operational checks by engineering personnel is increased. The absence of emergencies ensures uninterrupted power supply to all categories of consumers and thus increases the overall investment potential of the power supply industry. Therefore, the fail-safe operation of equipment is an obvious factor of Russian technology development as well as complies with the Rosseti regulations regarding the common engineering policy in the integrated power grid.

At present, the research on the grid connection characteristics of photovoltaic system mainly focuses on the steady-state characteristics of photovoltaic grid connection interface. Such as photovoltaic grid connected power quality characteristics, low voltage ride through characteristics, islanding detection methods and so on. Under the condition of grid failure, the voltage and current characteristics of photovoltaic grid connected system have not formed an accurate analysis model, which brings great trouble to the fault analysis and relay protection setting calculation of large-scale photovoltaic grid connected system. With the continuous improvement of the penetration rate of grid connected photovoltaic power generation, the research focus of photovoltaic power generation has gradually shifted from the steady-state characteristics of power quality of photovoltaic power generation to the transient characteristics of grid operation faults caused by grid connected power generation. Because the working principles and connection modes of various photovoltaic power generation are quite different from those of traditional generators, the research methods and tools of conventional power system fault analysis and setting calculation are difficult to be applied to large-scale photovoltaic grid connected systems. Therefore, it is urgent to study the transient characteristics of large-scale photovoltaic access ports in power system on the basis of in-depth understanding of power system fault calculation, photovoltaic power generation electromagnetic transient modeling method and simulation principle. The current research mainly focuses on the following three aspects: first, the dynamic mechanism analysis of photovoltaic grid connection and the mathematical model of electromagnetic dynamics; the second is the characterization of photovoltaic grid connected port based on dynamic simulation model; the third is the research on the interaction characteristics of photovoltaic and power system under typical application scenarios. The research results could further improve the stability of photovoltaic power station and power grid and ensure the safe and efficient operation of the whole system. It also provides theoretical basis and technical support for grid connected operation detection technology of photovoltaic power station. It can also provide reliable parameters for the power grid in line with the operation characteristics of renewable energy generation without changing the classical calculation methods such as relay protection setting calculation. It aims to enhance the operational ability of system and solve a series of problems caused by the connection of renewable energy to the power grid, which has irreplaceable special significance for the development of the power industry in the future.

The primary reason for interconnections among different power grids is to reduce the overall economic costs as well as increase reliability and security of supplying electricity services. Thus, for electrical power flow from one power system or grid to another power system or grid a simple, reliable and low cost interconnection is needed. In this paper, a flexible ac power transmission link technology has been proposed for linking two asynchronous independent power systems. The proposed flexible asynchronous ac link (FASAL) system essentially consists of a rotating transformer which is put in the ac tie line between two separate power systems or grids. It controls the power transmission between these power systems which are asynchronous under some or all operating conditions. The direction and the magnitude of power flow is controlled by controlling voltage and/or frequency. Simulink model of proposed FASAL system has been developed for the analytical study and the result verifies the power transfer capability of the proposed system.

With the rapid development of ultra-high voltage (UHV) inter-regional interconnected power grid and the wide application of a large number of power electronic devices, the security and stability characteristic of power grid is becoming more and more complex, and the risk of safe operation is increasing day by day. To further adapt to the power grid situation, in recent years, the State Grid Corporation of China has put forward the requirement of building a comprehensive security defense system for the large power grid, namely “system protection”. System protection is an emergency control system based on wide area information collection, rapid fault diagnosis and isolation, multi-resource collaboration, and other functions. It covers many sites and the coupling relationship between device strategies is complex. At the same time, due to the limitation of control resources, the cross configuration between strategies is gradually increasing, and the influence range of local system anomalies is becoming larger and larger. Its complexity and hidden dangers lead to a significant increase in the risk of power grid operation. At present, there is little literature on how to reduce the risk of power grid safe and stable operation caused by the failure of the system protection itself through effective coordinated adjustment. In this paper, a coordinated adjustment method based on typical expected fault scenarios of system protection is proposed. For typical expected fault scenarios of system protection with unacceptable risks, certain measures are taken in advance to reduce the possible risks to the power system.

In view of the characteristics of intermittence and fluctuation of wind power output and the trend of large scale grid connection of wind power and power grid to assume the function of renewable energy consumption, this paper proposes a multi-objective coordinated planning method based on AP (Affinity Propagation) clustering algorithm combined with improved MPGA (Multi-Population Genetic Algorithm) for power grid considering wind power integration. Firstly, the AP clustering algorithm is used to cluster the typical wind farm operation scenarios. Then, the power grid planning optimition model considering wind power consumption and line load balancing rate is established. Finally, the feasibility and validity of the proposed method are verified in the IEEE 18-bus system.