Systematic Design of the Lead-Lag Network Method for Active Damping in LCL-Filter Based Three Phase Converters

Abstract

Three-phase active rectifiers guarantee sinusoidal input currents and unity power factor at the price of a high switching frequency ripple. To adopt an LCL-filter, instead of an L-filter, allows using reduced values for the inductances and so preserving dynamics. However, stability problems can arise in the current control loop if the present resonance is not properly damped. Passive damping simply adds resistors in series with the LCL-filter capacitors. This simplicity is at the expense of increased losses and encumbrances. Active damping modifies the control algorithm to attain stability without using dissipative elements but, sometimes, needing additional sensors. This solution has been addressed in many publications. The lead-lag network method is one of the first reported procedures and continues being in use. However, neither there is a direct tuning procedure (without trial and error) nor its rationale has been explained. Thus, in this paper a straightforward procedure is developed to tune the lead-lag network with the help of software tools. The rationale of this procedure, based on the capacitor current feedback, is elucidated. Stability is studied by means of the root locus analysis in z-plane. Selecting the lead-lag network for the maximum damping in the closed-loop poles uses a simple optimization algorithm. The robustness against the grid inductance variation is also analyzed. Simulations and experiments confirm the validity of the proposed design flow.

Active damping techniques for LCL-filtered inverters-based microgrids

“…AD techniques can be classified into two categories. The first group includes schemes such as high-order controllers (filters) which do not require additional measurement [11]- [15]. Another group consists of extra feedback (multi-loop) based AD control approaches which use the feedback of filter capacitor current [4], [16], [17] or voltage [3], the virtual resistor scheme [9], [18], [19], and composite control method [20], [21].…”

“…11. G D (s) is a cascaded notch filter which its center frequencies has been tried to be consistent with the cable resonance peaks to damp resonant gains due to its reject-band filter characteristic and Z cable (s) is input impedance of the cable assuming that the cable is terminated with an voltage source, which can be defined as follows [8] (15) where Z= Z g / Z C . Z g is the impedance seen from the gridside, Z C = y z is the characteristic impedance of the feeder, and y z ⋅ = γ is the propagation constant.…”

A New Control Strategy for a Three-Phase PWM Current-Source Rectifier in the Stationary Frame

“…The Real Time Workshop (RTW) in Simulink is one of the DSP development tools, which has the capability to design a rapid prototyping system and to generate code directly from the Simulink models, and the entire running process is done automatically by using MATLAB/Simulink and Code Composer Studio (CCS V3.3) [34] [35]. In this study, the control strategy that was mentioned earlier in Section III is implemented using the TI C2000 package and TMS320F2808 toolbox, as shown in Fig.…”

Robust Active Damping Method for a PWM Converter Operating with an Unknown Inductance on the Power Grid

“…It is common to suppress the resonance of the LCL filter by feedback control of the capacitor current or voltage (2)- (5) . A sensorless active damper, to estimate the capacitor voltage or current of the LCL filter and suppress the high-frequency resonance, is proposed (6)- (11) . In some cases, a passive damper with a damping resistor is combined with an LCL filter to suppress the resonance (12)- (14) .…”