A new virtual harmonic impedance scheme for harmonic power sharing in an islanded microgrid

Direct Control of the Inverter Impedance to Achieve Controllable Harmonic Sharing in the Islanded Microgrid

“…current harmonics. The voltage quality in islanded microgrid can be improved either by compensating the harmonic voltage drop in the network elements [13][14][15] or by proper nonlinear load current sharing [16][17][18][19][20][21][22][23]. This paper deals with the latter approach to share the nonlinear load current harmonics while enhancing the voltage quality.…”

“…The reported work in the area of harmonic current sharing can be classified into communication based techniques [16][17] and decentralized techniques [8], [18][19][20][21][22][23]. In communication based techniques the PCC voltage is sent through communication links to a centralized controller to achieve harmonic current sharing.…”

“…Among these approaches, the decentralized control is preferable as it does not require any communication infrastructure and can improve the system reliability. Harmonic current sharing using decentralized techniques can be further classified into virtual resistance/impedance techniques [8], [18][19][20][21][22] and virtual conductance technique [23]. The concept of harmonic power sharing using the virtual resistance was first proposed in [8].…”

“…This technique modifies the effective line impedance by including a virtual harmonic resistance at the inverter output. Several variations of [8] have been reported later in [18][19][20][21]. Of which, the positive harmonic resistance technique presented in [18][19][20] increases the effective line impedance and thereby worsens the voltage quality at all buses.…”

“…Of which, the positive harmonic resistance technique presented in [18][19][20] increases the effective line impedance and thereby worsens the voltage quality at all buses. Alternatively, the negative virtual harmonic impedance concept developed in [21] achieves harmonic sharing without affecting the voltage quality. However, the negative virtual harmonic technique requires the prior knowledge of line impedance and it can provide compensation only up to the value of line impedance.…”