Multivariable Grid Admittance Identification for Impedance Stabilization of Active Distribution Networks

Abstract

Estimating grid admittance is essential for assessing impedance stability and for designing adaptive controllers for distributed generation (DG) units. This paper proposes a new multivariable grid admittance identification algorithm that involves adaptive model order selection as an ancillary function within inverter-based DG controllers. Cross-coupling between d-and q-axis grid admittances necessitates multivariable estimation. To ensure persistence of excitation for grid admittance, sensitivity analysis is first employed in order to determine the injection of controlled voltage pulses by the DG. Grid admittance is then estimated from the processing of the extracted grid dynamics by the refined instrumental variable method for continuous-time system identification (RIVC) algorithm. The theoretical background underlying the RIVC algorithm is introduced, along with its integration within the proposed method for adaptive model order selection. Unlike nonparametric identification algorithms, the proposed RIVC algorithm provides a parametric multivariable model of grid admittance, which is essential for designing DG adaptive controllers. A hardware-in-the-loop application using OPAL-RT real-time simulators has been used to validate the proposed algorithm for both grid-connected and isolated active distribution networks.Index Terms-Distributed generation (DG), impedance stability, multivariable grid admittance identification, refined instrumental variable method for continuous-time system identification (RIVC).

Voltage Regulation in Smart Grids

“…The central control unit receives the desired SOCs and sends the charging decisions to all vehicles in the parking lots. An OPAL real-time simulator (RTS) is used to model the visual test network using the SimPowerSystems blockset, which is available in Simulink/ Matlab, and an ARTEMiS plug-in [22]. The network, PEV, and DG models are distributed between the RTS cores for performing parallel computations.…”

“…, a maximum power point tracking (MPPT) algorithm along with a DC link voltage controller is employed [7]. On the other hand, I ref d can be calculated, as in (22), to regulate the output reactive power, thus, providing voltage support.…”

Observer-Based Pulsed Signal Injection for Grid Impedance Estimation in Three-Phase Systems

“…For the excitation signal, several approaches have been proposed: 1) Pulsed Signal Injection (PSI) [9], [23]- [25]; 2) High Frequency Signal Injection (HFSI) at constant high frequency [18], [19], [26]- [28]; 3) current regulator reaction [19]; 4) Low Frequency Signal Injection (LFSI) [20], [29], [30]; 5) Binary Sequence Signal Injection (BSSI) [21], [31], [32].…”

“…The results in [24] are related to the ones presented in this paper, but they are only focused on a pure inductive three phase balanced impedance. The method proposed in [23] is based on parameter identification using the pulse response and an adaptive model approach. The authors claim the method is able to estimate the grid admitance even with the presence of other power converters connected to the grid.…”

New Trends in Active Power Filter for Modern Power Grids

“…Nevertheless, current researches point out to replace its representation by equivalent impedances that are dynamically modified due to a considerable amount of nonlinear loads, which are dynamically connected and removed from the power grid. This issue becomes more important nowadays due to the proliferation of renewable energy sources with power converter interface [10][11][12][13]. Figure 2 illustrates a simplified scheme of the series active filter compensating harmonics and voltage sag, with the reference voltage (v*) being determined through the applied control algorithms, which presents the grid current (i S ), grid voltage (v S ), and the DC-link voltage (v DC ) as inputs.…”