Discrete-time optimal active damping of LCL resonance in grid connected converters by proportional capacitor current feedback

Wagner, Martin; Barth, Tobias; Ditmanson, Chester; Alvarez, Rodrigo; Bernet, Steffen

doi:10.1109/ecce.2013.6646773

Cited by 19 publications

(25 citation statements)

References 10 publications

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“…1) If K AD <K ADMax_Lg , both the inner-loop stability and the dual-loop system stability are ensured since this situation is exactly the same as Case I. 2) If K AD >K ADMax_Lg , the dual-loop stability criterion is (21). To ensure GM(ω div )<0 when L 2 varies, it is necessary to study the property of GM(ω div ).…”

Section: Discussionmentioning

confidence: 99%

“…Thus, the robustness is poor. On the other hand, if the minimum value of ω res_Lg is less than ω div , the criterion for robustness is given in (22) because either (19) or (21) has to be fulfilled with the decrease of the real ω res_Lg . …”

Section: ) Case Ii: the Inner Ad Control Is Unstablementioning

confidence: 99%

“…In addition to the two approaches depending on the DSP working mode, the use of an extra phase compensator seemed to be an alternative choice. In [15], [17], [20] and [21], researchers tried several…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Stability Analysis and Improvement of the Capacitor Current Active Damping of the LCL Filters in Grid-Connected Applications

Xu¹,

Xie²,

Zhang³

2016

Journal of Power Electronics

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For grid-connected LCL-filtered inverters, dual-loop current control with an inner-loop active damping (AD) based on capacitor current feedback is generally used for the sake of current quality. However, existing studies on capacitor current feedback AD with a control delay do not reveal the mathematical relation among the dual-loop stability, capacitor current feedback factor, delay time and LCL parameters. The robustness was not investigated through mathematical derivations. Thus, this paper aims to provide a systematic study of dual-loop current control in a digitally-controlled inverter. At first, the stable region of the inner-loop AD is derived. Then, the dual-loop stability and robustness are analyzed by mathematical derivations when the inner-loop AD is stable and unstable. Robust design principles for the inner-loop AD feedback factor and the outer-loop current controller are derived. Most importantly, ensuring the stability of the inner-loop AD is critical for achieving high robustness against a large grid impedance. Then, several improved approaches are proposed and synthesized. The limitations and benefits of all of the approaches are identified to help engineers apply capacitor current feedback AD in practice.

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Section: Discussionmentioning

confidence: 99%

Section: ) Case Ii: the Inner Ad Control Is Unstablementioning

confidence: 99%

See 1 more Smart Citation

Stability Analysis and Improvement of the Capacitor Current Active Damping of the LCL Filters in Grid-Connected Applications

Xu¹,

Xie²,

Zhang³

2016

Journal of Power Electronics

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show abstract

“…(10), where K is the feedback matrix and I is the unit matrix. The following discussions are based on this transfer function.…”

Section: Fmentioning

confidence: 99%

A Modified Capacitor Current Feedback Active Damping Approach for Grid Connected Converters with an LCL Filter

Wan¹,

Xiong²,

Ji³

et al. 2015

Journal of Power Electronics

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Capacitor current feedback active damping is extensively used in grid-connected converters with an LCL filter. However, systems tends to become unstable when the digital control delay is taken into account, especially in low switching frequencies. This paper discusses this issue by deriving a discrete model with a digital control delay and by presenting the stable region of an active damping loop from high to low switching frequencies. In order to overcome the disadvantage of capacitor current feedback active damping, this paper proposes a modified approach using grid current and converter current for feedback. This can expand the stable region and provide sufficient active damping whether in high or low switching frequencies. By applying the modified approach, the active damping loop can be simplified from fourth-order into second-order, and the design of the grid current loop can be simplified. The modified approach can work well when the grid impedance varies. Both the active damping performance and the dynamic performance of the current loop are verified by simulations and experimental results.

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“…The active damping method can be used to damp out the resonance at no expense of efficiency. The state variable feedback, such as filter capacitor voltage [15,16] or filter capacitor current [17,18], is introduced to provide virtual resistance. Among them, the capacitor current feedback is a typical and widely used method.…”

Section: Introductionmentioning

confidence: 99%

Digital Controller Design Based on Active Damping Method of Capacitor Current Feedback for Auxiliary Resonant Snubber Inverter with LC Filter

et al. 2016

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Abstract:In some high-performance applications, an LC filter must be added to the auxiliary resonant snubber inverter (ARSI) to reduce the output current ripple. However, resonance occurs due to the additional LC filter, which makes the traditional closed-loop control not suitable to be used directly. Therefore, this paper presents a double-loop digital control based on the active damping method of capacitor current feedback to stabilize the system. Most of the studies on active damping methods are focused on the grid in consideration of zero resistance. However, the load resistance should not be neglected in the drive system. Therefore, the load resistance and digital control delays are considered in this paper. Moreover, an improved loading method is proposed to improve the duty ratio range. In order to verify the effectiveness of the controller, a prototype was developed. The simulation and experimental results demonstrate that soft-switching can be realized for the entire load range. The maximum duty ratio is improved by 0.01 by using the proposed loading method. The resonance can be eliminated by using the proposed control method.

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Discrete-time optimal active damping of LCL resonance in grid connected converters by proportional capacitor current feedback

Cited by 19 publications

References 10 publications

Stability Analysis and Improvement of the Capacitor Current Active Damping of the LCL Filters in Grid-Connected Applications

Stability Analysis and Improvement of the Capacitor Current Active Damping of the LCL Filters in Grid-Connected Applications

A Modified Capacitor Current Feedback Active Damping Approach for Grid Connected Converters with an LCL Filter

Digital Controller Design Based on Active Damping Method of Capacitor Current Feedback for Auxiliary Resonant Snubber Inverter with LC Filter

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