Design And Analysis Of Robust Active Damping For LCL Filtered Converter Based On Phase Compensation

In the distributed generation system,the power electronic converter acts as a transformation interface between different power supply buses,which plays a vital role in energy conversion.The performance of the converter directly affects the operational reliability of the entire grid system.The PWM converter has the characteristics of easy implementation,strong voltage and current regulation,and is commonly used in distributed power generation systems.However,due to the modulation characteristics of PWM,PWM converters often need to use filters to suppress switching harmonics.Single-inductor L-type filters are widely used in power electronic converters for harmonic suppression due to their simplicity and high stability.However,the L-type filter is bulky and heavy,and has a high cost.LCL filters are a solution to reduce filter inductance,cost and size with their higher frequency harmonic attenuation.However,as a third-order system,the LCL filter’s inherent resonant peaks can easily lead to system instability problems.It is necessary to add damping to the PWM control to ensure system stability.In this paper,the active damping control of LCL filter resonant peak is taken as the main research content.An active damping method based on phase compensation is proposed.By introducing an all-pass filter into the controller,the stability control of the current loop is realized.And the robustness of the filter capacitance parameter changes.In this paper,based on the current loop control of single-phase AC/DC rectifier,the relationship between the sampling frequency and the resonant frequency of the LCL filter in the continuous and discrete domains is discussed and the in-depth study is carried out.The impact of the system.In view of the unstable current loop control caused by the delay link,this paper introduces the passive damping and active damping traditionally used for resonant spike damping.In order to avoid the loss of passive power to the system power,this paper focuses on the active damping method,and performs the open-loop Bode diagram analysis and simulation verification for the commonly used active damping method.Finally,the paper proposes an active damping method based on phase compensation.The phase lead compensation and phase lag compensation are introduced to make the converter current loop control meet the Nyquist stability criterion.For the converter-side current feedback method,the all-pass filter is used to design the phase at a specific frequency,and the all-pass filter design method based on the capacitance parameter offset and the allowable variation range of the grid impedance is given.The essence is to ensure the current control stability under the change of the resonant frequency of the LCL filter through the reconfiguration of the-180°crossing phase.In order to verify the theoretical analysis and design criteria,this paper builds an experimental verification platform based on d SPACE DS1006,and validates the active damping method based on the all-pass filter under the converter-side current feedback control mode.The experimental results show that the active damping method proposed in this paper can effectively guarantee the current loop control stability of the rectifier,verify the design criteria of the proposed all-pass filter,and compare it under the condition of filter capacitor parameter drift and grid impedance change.High robustness.