Machine type communications are ubiquitous in electrical power systems. From the perspective of performance analysis for LoRa and NB-IoT systems of low power wide area network(LPWAN), this paper provides comparison results of service capabilities between LoRa and NB-IoT systems by wireless coverage and BER transmission performance simulations of 230 MHz, 900 MHz multi-bands, and urban area, suburban area multi-scenarios. Furthermore, parameter configuration and optimization design for LPWAN to enable QoS transmission of smart grid applications are given in this paper. The proposed results and scheme could effectively guide communication technology selection and network optimization for power Internet of Things.

The high bandwidth and low latency of 5th generation mobile networks (5G) play an important role in the construction of ubiquitous power Internet of Things (UPIoT), and provide strong protection for the goal of universal interconnection and human-computer interaction. This paper studies the application of 5G in UPIoT. Firstly, the mainstream IoT communication technology at home and abroad is summarized, the principle and characteristics of 5G are introduced emphatically. Secondly, the characteristics of UPIoT and the demand for communication services are analyzed deeply. The three major application scenarios of 5G and the possible power business of each scenario are studied. Thirdly, the application of 5G in the ubiquitous power Internet of Things is studied from the aspects of grid-connection of distributed new energy and energy storage, monitoring of power transmission and transformation operation, regulation and protection of distribution network, user load perception and regulation, collaborative scheduling and stability control, planning and investment, and comprehensive governance. Finally, the key technologies of 5G applied to the ubiquitous power Internet of Things are discussed from the aspects of power generation, transmission, substation, power distribution and power consumption, and the 5G network security protection technology is studied. 5G has broad application prospects in UPIoT, and has important engineering application value.

Digital technology is leading the development and evolution of the fourth industrial revolution, promoting the gradual transformation of industrial economy into digital economy.In the era of digital economy, digital power grid is a new idea, new way and new insight for the construction and development of smart grid driven by technological evolution and demand upgrading. The definition, composition and characteristics of digital twin are expounded. The paper first proposes the digital power grid based on digital twin, analyzes the concept, characteristics of digital power grid and its derivative relationship with smart power grid, constructs the digital power grid architecture including physical power grid, perception layer, transmission layer, data layer, platform layer and application layer, and summarizes the key technologies of digital power grid.The digital power grid realizes the twin interaction between the physical world and the digital world, supports the digital operation of the power grid and constructs the digital energy ecology by constructing the power grid data closed-loop empower system.

With the gradual development of digital power grid construction, power Internet of Things is becoming more and more important. However, the security threat will be more complex, which is mainly manifested in two aspects: the uncontrollable risk caused by the terminal equipment itself; and the risk of invasion of the power information network. It is necessary to use effective intrusion detection methods to prevent unknown network attacks, and the key technology is the accurate identification of the attack mode, which is conducive to the security operation and maintenance team to further analyze the enemy’s attack means, attack path and attack habits, and prepare for the next attack defense. In this paper, by improving the clustering analysis algorithm in machine learning, a network attack pattern recognition algorithm model based on clustering analysis is established. This model has the clustering analysis ability in the big data scenario. It can clear the isolated data, control the clustering categories and post process the clustered pattern data, so as to further improve the accuracy of attack pattern recognition. In addition, this paper also uses the open source network intrusion detection data set to analyze and verify the algorithm model, and evaluate its correctness and effectiveness. Finally, the algorithm is applied in practice.

Advanced sensing and measurement technology is the key to realize transparent power grid and power Internet of Things. In order to meet the measurement needs of the power Internet of Things, this paper developed a micro current sensor device based on giant magnetoresistance effect, including the design of the sensor architecture, signal processing circuit, digital processing circuit, self energy, wireless communication, temperature compensation and other functional modules, the sensor shell structure is designed and the special protection design of IP and insulation is carried out. Finally, the sensor has been applied in the field of low-voltage distribution for a long time. The results show that the current sensor can work stably and reliably for a long time. It has the advantages of miniaturization, high integration, convenient installation and remote management. It can provide more comprehensive and real-time information support for the operation of the distribution network and lay the foundation for the transparent management of the smart grid.

The LoRa (long range) technology in the low power wide area network (LPWAN) technology is applied to the ubiquitous power Internet of Things (UPIoT). For the role of the phase phasor acquisition unit (PMU) in the wide area measurement system (WAMS), the LoRa technology is used as the entry point, and it is integrated with the existing PMU technology. The feasibility of the solution is verified by the of LoRa technology’s PMU hardware system and software system performance tests.

Aiming at the development status and existing problems of sensor access technologies for wireless Internet of Things (IoT), to avoid similar situations in the application of Internet of Things in energy (IoTE), the present sensor access technology should be optimized and improved. At first, this paper introduces the network characteristics and structure of IoTE, which can be flexibly selected according to different application scenarios for the IoT field network. Then, according to the low power consumption requirements of IoT sensors, an efficient wake-up mechanism suitable for IoTE networks is proposed. By applying the mechanism, the low power nodes can quickly identify the invalid wake-up frames and return to sleep quickly. Finally, theoretical analysis and calculation of power consumption are carried out for the wireless IoT network. Compared with the traditional wake-up mechanism, the proposed passive wake-up mechanism has obvious advantages in low power consumption and low latency.

Aiming at the actual situation of high failure rate of communication modules of smart meters, the reliability evaluation of communication modules of smart meters is carried out. By reliability accelerated life test method, reliability tests are performed under five different stress combinations of temperature and humidity. Based on the goodness-of-fit tests of the two-parameter exponential distribution, Weibull distribution, normal distribution, and log-normal distribution on the failure data, the failure of the smart meter communication module is most consistent with the two-parameter exponential distribution model. Using the Peck acceleration model and extrapolating the test data, the reliability function of the smart meter communication module is obtained. Its ten-year unreliability is 0.126, which does not meet the overall lifespan requirement of smart meter, and the paper proposes several measures to improve the reliability of the communication modules of smart meters.

This paper proposes the expansion scheme of the converter station based on paralleled VSC and LCC convertor in order to solve the problem of insufficient transmission capacity in the traditional HVDC project and make full use of the transmission line corridor. The sending-end adopts two paralleled LCC converters structure and the receiving-end adopts paralleled LCC and VSC converter structure to reduce the expansion cost. The VSC converter of receiving-end also makes the best of quick independent control of active and reactive power, and improves the ability of LCC converter to prevent commutation failure. To prevent commutation failure, the LCC is usually equipped with a prediction control module. In this paper, the association model between LCC and VSC is established, and it is derived that the prediction control still has some effect in this scheme. Then the VSC and LCC’s reactive coordination control scheme is put forward, which increases the turn-off angle of LCC in the event of failure and maintains the voltage of the power grid to prevent commutation failure. Finally, the correctness and validity of the reactive coordination control of the expansion scheme are verified in the PSCAD/EMTDC simulation environment.

With the large amount of distributed energy entering power grid and the increase of DC load, multi-terminal AC/DC distribution network becomes the future development trend, and multi-port power electronic transformer becomes the core equipment. In the multi-port power electronic transformer with series connection H-bridge (CHB)structure, there are a lot of full bridge modules and bidirectional active bridge (DAB)modules. At the same time, many factors such as high switching frequency make it very difficult to simulate switching devices model of the multi-port power electronic transformer. Especially in the case of AC/DC distribution network with multiple power electronic transformers interconnected, the system simulation is almost impossible to be completed. In order to solve the above problems, a transient average model is proposed. By modeling and simplifying the multi-port power electronic transformer and simulating it with unlocking model in steady state, research and simulation on system level verification such as coordinated control of multi-terminal system, can be supported. In case of fault, the system fault simulation is completed by switching between unlocking equivalent circuit and locking equivalent circuit, which improves the simulation speed. Finally, the correctness of the proposed model is proved by comparing the simulation results under DC fault.

Combined with the custom gamma angle measurement principle and the working state of the evolutional line commutated converter (ELCC), the ELCC’s extinction angle measurement method and control output flow are designed. A new ELCC model with a extinction angle measurement output module is established in PSCAD/EMTDC, and compared with the CIGRE standard test model under different conditions of transient stability. The results show that the new ELCC model and the CIGRE standard test model have high equivalence under steady-state conditions; during the fault period, the new ELCC model has stronger AC single-phase fault resilience than the CIGRE standard test model, effectively preventing the occurrence of commutation failure. The accuracy of the ELCC turn-off angle measurement output module is verified, which also provides a reference for the renovation design of the converter valve topology.

To realize automatic conformance test on IEC 61850 server, an highly reusable automatic test system is proposed to reasonably abstract IEC 61850 test cases, a set of description rules based on XML is defined, and the test logic and test data of closed-loop tests are fully described. The test software framework uses a highly extensible and maintainable object-oriented mechanism and performs parsing and execution of test scripts. The test system is highly reusable, and guarantees the comprehensiveness and adequacy of the test by taking the following measures. Summarizing the commonality of IEC 61850 test cases, and abstractly representing test logic; operation objects support dynamic configuration, and automatically maps to specific data objects in the device model during operation; operation parameter values support key word setting or saved data referencing, and automatically converts to specific values based on the relevant data status or configuration during operation; test data can be expanded easily without modifying the software framework; operation type can be expanded easily by coding the desired operation class in the software framework; providing support for comprehensive test data processing, rich test criteria; providing support for multi-client test by role designation and the host judges the test results. The proposed test script and test software framework design can give reference to the development of automatic test tools.