| With the vigorous development of society,as one of the indispensable resources in daily life,the demand for electricity energy is increasing.At the same time of social development,attention should also be paid to environmental protection.Offshore wind resources are abundant,offshore wind speed is stable,and offshore wind power generation hours are high.Large-scale wind power has always been the focus of development and utilization.In recent years,the DC transmission scheme of offshore wind power based on uncontrolled diode rectifier has attracted wide attention due to its small size,low cost and simple operation control.The existing literature rarely comprehensively analyzes the stability of the system.In this context,this paper studies the broadband oscillation of offshore wind power through diode-based rectifier DC transmission system and the optimization of control parameters.The main research contents and innovative work include :Firstly,the structure and control principle of offshore wind power DC transmission system with diode-based rectifier and the conventional method of sequence impedance modeling are introduced.The offshore wind farm in this paper is composed of direct-drive wind turbines.Around the control strategy of direct-drive wind turbines,a mathematical model including fullpower converter,wind turbine and permanent magnet synchronous generator is established.Around the form of sequence impedance,the impedance modeling method in synchronous rotating coordinate system and stationary natural coordinate system is described.Finally,the characteristics of the two modeling methods are compared.Secondly,using the harmonic linearization method,the sequential impedance models of the power feeder rectifier station of the offshore wind farm and the diode-based rectified high-voltage DC system are built respectively;the basic principles of the wide-band oscillation of the interconnected system from different angles,the inverse Nyquist criterion,the relationship between the interconnected system impedance ratio and the control bandwidth,the damping ratio,and the advantages of the zero-pole distribution diagram are integrated,and a control parameter optimization design method is proposed.The control parameters of the wind turbine gridconnected inverter are optimized.The accuracy of the sequential impedance model is validated by building a frequency-scanning platform,and the experimental simulation model is validated by proving the reasonable design of the parameter optimization.Lastly,the DC side input impedance model and AC side output impedance model of the onshore inverter station of the diode-based rectifier HVDC system are established,and an adaptive impedance optimization method is proposed to solve the broadband oscillation problem caused by the change of operation condition,and the complete parameter design process is given.Finally,the effectiveness of the method is verified by time domain simulation model. |
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