Project Introduction:

The project has developed DC transmission systems and new energy models that meet the needs of different scenarios, and proposed adaptability evaluation and improvement plans for the wind farm aggregation model taking into account the LVRT curve; proposed switching pulse compensation algorithm to eliminate unrealistic fluctuations in HV DC transient simulation; reveals the coupling mechanism of AC and DC in close electrical distance, multiple DC electromagnetic, and electromechanical transient, and proposes evaluation indicators such as voltage stability, multiple DC effects, harmonic instability, and subsynchronous oscillation risks to evaluate coupled operation; Comprehensive measures to improve the reliability of power transmission from large energy bases, such as strengthening the grid structure, optimizing thermal power transient reactive capabilities, DC controller design and parameter tuning, are proposed. Strong wind and wind fluctuations, easy disconnection from the grid, and weak reactive power support are evaluated. Coupled risks with disturbances in multiple DC systems in close electrical distances, network source response strategies are proposed; The power security defense system for Ningxia's large-scale energy base has been developed, which has functions and characteristics such as online/offline integrated modeling, electromechanical and electromagnetic simulation, and dynamic security assessment. Obtained 1 authorized utility model patent.

2. The technical principles and performance indicators topic relies on the actual physical scene of high-voltage AC and DC transmission in Ningxia's 10-kilowatt large-scale energy base, and focuses on the energy base's large-scale concentration of new energy and conventional energy, distributed access coexistence, high-proportion, high-density wind, wind and light. In-depth research work has been carried out in aspects such as simulation modeling, characteristic analysis, safety and stability control technology, and the design and research and development of the energy base's security defense system. It has broken through several key technologies for power security in large energy bases.

(1) New energy models and adaptability research that meet the needs of different scenarios. Wind power and photovoltaic models are consistent with the understanding of the physical laws of actual equipment and have practical application value. The evaluation index considering the equivalent accuracy of LVRT, the structure and parameter conversion method of the single-machine equivalent doubling aggregation model and the multi-machine equivalent doubling aggregation model for new energy power stations are proposed.

(2) Research on DC transmission system models and adaptability to meet the needs of different scenarios. A detailed electromagnetic transient simulation model consistent with the characteristics of Ningxia Power Grid DC engineering is established in ADPSS, and compared with PSCAD for verification. Establish a DC electromechanical transient simulation model in PSASP that reflects the actual control and protection characteristics. The adaptability evaluation indicators of the established refined models at different scales under different scenarios of Ningxia Power Grid simulation are proposed.

(3) Coupling mechanism of electromagnetic and electromechanical transient characteristics of AC and DC and multi-DC transmitting terminal systems Establish a DC electromagnetic transient simulation model consistent with the characteristics of the actual DC transmission control and protection system, and simulate and analyze DC systems under various types of AC faults near the transmitting terminal. Coupling relationship. Study the interaction mechanism between AC and DC systems caused by DC system faults, and study and propose problems and measures that need to be prevented or improved when multiple DC projects are connected to the AC system at the transmitting end. Study the evaluation indicators of the impact of AC and DC coupling on the sending end system.

(4) The operating coupling mechanism of large-scale new energy and multiple DC systems proposes the laws and countermeasures of the coupling impact of wind, solar and DC systems under new energy fluctuations. The laws and countermeasures of the coupling influence of new energy and DC systems under typical disturbances such as DC lockout are proposed. The changes in system frequency characteristics and safety control strategies under large-scale new energy access are proposed, as well as their impact on DC systems and countermeasures.

(5) The research on the mechanism and response strategies of subsynchronous oscillation in coal-fired-intensive multi-DC transmitting terminal systems covers various influencing factors such as AC system conditions, DC operating parameters, and electrical distance between DC, and conducts a comprehensive analysis of the damping characteristics of the system. Based on different types of design principles, the effects of DC additional damping control (SSDC) and generator additional excitation damping control (SEDC) on suppressing subsynchronous oscillation are studied and clarified.

(6) The online and offline integrated modeling method proposed by the power security defense system of large energy bases can realize the automatic use and splicing of online computing data. It can store 1 year's raw SCADA operating data; prompts and alarms are given when the disk capacity is less than 20%; the time for importing SCADA raw data into the database is less than 5 seconds; the statistical analysis time for operating data is less than 10 seconds; the result display time is less than 1 second; The statistical time of the specified time period can at least count all time section data within a 5-day time range; the accuracy rate of statistical data results is greater than 95%. Establish a maintenance mechanism for online update submission after offline verification to ensure efficient maintenance of online security and stability analysis. Analyze the impact of DC, new energy (wind turbines, photovoltaic), high energy-carrying loads, etc. on power grid simulation calculation when they are equated into load models, and provide calculation basis for offline fast and automatic expansion technology.

Creativity of results

advanced nature

(1) In view of the insufficient accuracy of HVDC transmission transient simulation in Ningxia's tens of millions of kilowatt wind power base, an adaptability evaluation and improvement plan for the wind farm aggregation model based on LVRT control curve is proposed; a switching pulse compensation algorithm is proposed to eliminate unrealistic fluctuations in HVDC transient simulation.

(2) A series of evaluation indicators are proposed to comprehensively evaluate the risk of voltage stability, power-angle oscillation, multiple DC interactions, harmonic instability, and subsynchronous oscillation of coupled operation of AC and DC and multiple DC transmitting terminal systems in a tens of millions of kilowatt energy base.

(3) Comprehensive measures are proposed to improve the reliability of high-voltage AC and DC power transmission in large energy bases, such as strengthening the grid structure, optimizing the internal potential of the power source in the thermal power base, and adjusting the parameters of the DC system body.

(4) It reveals the coupled operation risks of strong wind and wind fluctuations, easy disconnection from the grid, weak reactive power support and disturbance impacts on the transmitting and receiving terminals of multiple high-voltage DC systems in close electrical distances, and proposes a coordinated response strategy for network and source.

(5) Propose the overall implementation plan for the power security defense system of Ningxia's 10 million-kilowatt large-scale energy base, which has online/offline integrated modeling, all-digital electromechanical-electromagnetic simulation simulation, historical/real-time dynamic security assessment, and new energy production simulation. and other functions and characteristics.

Technology maturity

The key power safety technologies and defense systems developed by the scope of application and safety project have practical conditions and have been applied to the Ningxia Electric Power Dispatching Control Center. The results are suitable for promotion to large-scale wind power and photovoltaic new energy access systems, which are close to DC electrical; access to high-penetration and fluctuating wind and light, with changeable currents, and complex coupling characteristics with AC and DC systems; low inertia, weak reactive power support, wind and light access with uncertain fault ride through capabilities; centralized construction of large thermal power bases, making it difficult to control short-circuit current in local areas; close electrical distance between multiple DC rectifier stations; Large-scale wind, solar and thermal energy bases are coupled with UHV/HV DC and AC systems and have the characteristics of power grids and energy bases.

Application situation and existing problems

The key power security technologies and defense systems developed by the project have been put into operation in Ningxia Electric Power Dispatching and Control Center, with a high degree of integration with the regulation and control system, and the overall operation is good.