An adaptive PI control scheme to balance the neutral-point voltage in a solar PV fed grid connected neutral point clamped inverter. (September 2019)

• Record Type: Journal Article
• Authors: Malakondareddy, B.; Senthil Kumar, S.; Ammasai Gounden, N.; Anand, I.
• Is Part Of: International journal of electrical power & energy systems. Volume 110(2019)
• Page Start: 318
• Page End: 331
• Publication Date: 2019-09
• Subjects: PV system -- MPPT -- Multi-level inverter (MLI) -- NPC inverter -- Single stage conversion -- Grid connected PV system -- Adaptive PI controller; Electrical engineering -- Periodicals; Electric power systems -- Periodicals; Électrotechnique -- Périodiques; Réseaux électriques (Énergie) -- Périodiques; Electric power systems; Electrical engineering; Periodicals; 621.3
• DOI: 10.1016/j.ijepes.2019.03.012
• Languages: English
• ISSNs: 0142-0615

Abstract

Highlights: API controller is developed to balance Neutral Point voltage in PV fed NPC inverter. API controller is mathematically modelled and tested with closed loop stability. API balances the NP voltage with less settling time and reduces grid current THD. A dq axes power controller is also implemented for power balance along with MPPT. The performance of the controller is validated in simulation and experimentation. Abstract: In the context of current harmonics mitigation in inverter, neutral point clamped (NPC) inverter is the promising one because of its robustness. Owing to the advantages of NPC inverter, this paper considers a PV fed grid connected NPC inverter. However, the main concern with the NPC inverter is the unbalance in the DC link capacitor voltage due to non-idealities such as DC offset in modulating signals, dissimilarities in the DC link capacitors and asymmetric gating signals, which lead to non-zero neutral point voltage. To address this issue, this paper proposes a simple adaptive proportional integral (API) controller and operates in conjunction with the dq axes power controller for PV fed Grid connected NPC inverter. Comprehensive mathematical expressions are derived for the design of API controller and the control parameters are adjusted continuously based on maximum PV power, PV voltage and modulation index for achieving the faster dynamic response. The closed loop stability of the proposed API controller is verified under the deviation in neutral point voltage using root locus plot. The effectiveness of the API with dq axes power controller is analysed and validated through MATLAB simulations and experimentation under the various dynamic operation of the PV- grid interactive system.