Brief view on control of grid‐interfacing AC‐DC‐AC converter and active filter under unbalanced and distorted voltage conditions

Abstract

Purpose -The purpose of this paper is to consider both sides of a back-to-back AC-DC-AC interface. Design/methodology/approach -The paper presents a mathematical analysis, simulation, laboratory test in scaled model. Findings -The two main findings comprised concept of control methods for grid AC-DC-AC converter applied in renewable energy sources with variable speed operation under distorted grid. Active filtering functionality in case of non-linear current of a parallel load. Second, a control algorithm dedicated for two-level AC-DC converter applied in industrial networks with high-order harmonics compensation working under hard conditions -balanced and unbalanced voltage dips.Research limitations/implications -The paper shows preliminary results for AC-DC-AC converter and active filter (AF) during voltage dips and for harmonics compensation. Control methods and/or topology should be improved and tested in scale and after at high-power system. Practical implications -Power quality supplied/received to/from the grid can be increased. In case of low-cost system only AF can be applied to existing non-linear receivers. Moreover, in case of full AC-DC-AC converter energy saving and production is possible. Originality/value -Presented control methods give satisfactory results. Paper presents laboratory results for grid and machine side two different power circuits during steady states and transients. Moreover, active filtering operation during voltage dips is presented.

Effective and Simple Control of Grid-Connected Three-Phase Converter Operating at a Strongly Distorted Voltage

“…If the grid voltages are symmetrical and pure sinusoidal, the converter currents are kept sinusoidal as well. However, the distorted grid voltage causes the higher order harmonics in the converter currents, which cannot be eliminated by classical VOC and it demands additional current distortion mitigation method [10], [21].…”

“…In the case of a stationary αβ reference frame, the current is controlled by PR controllers, which can be realized by Second Order Generalized Integrator (SOGI) used as resonant bank [9], [10]. PR controller is capable to control positive and negative sequence components simultaneously, what slightly reduces the computational load in comparison to control in a synchronous rotating reference frame.…”

“…PR controller is capable to control positive and negative sequence components simultaneously, what slightly reduces the computational load in comparison to control in a synchronous rotating reference frame. Moreover, a multiresonant controller can be tuned individually for selected harmonics in order to compensate the current distortions [10]. In literature are also proposed a combination of PI and PR controllers in the synchronous rotating frame, where PI is tuned to control fundamental harmonic and PR controllers are tuned to eliminate selected high-order harmonics [12].…”

Fuzzy logic in decision support system as a simple Human/Internet of Things interface for shunt active power filter

“…Fig. 6 presents a block diagram of such algorithm based on transformations into synchronous reference frames (SRFs) [33,36]. Currents measured in PCC are transformed into stationary reference frame (αβ stationary) and then to synchronously rotating frame (marked as dq), which synchronously rotates with selected higher harmonics frequency nφ.…”

“…Outputs of the power PI controllers are reference values for space vector modulator (SVM) [32][33][34][35].…”