Showing papers by "Rajiv K. Varma published in 2020"
TL;DR: This paper presents a novel fast frequency response and power oscillation damping control by large-scale PV plants controlled as STATCOM, termed PV-STATCOM, to simultaneously enhance frequency regulation and small signal stability of power systems.
Abstract: This paper presents a novel fast frequency response and power oscillation damping control by large-scale PV plants controlled as STATCOM, termed PV-STATCOM, to simultaneously enhance frequency regulation and small signal stability of power systems. Frequency deviations typically occur together with power oscillations in large power systems. The proposed controller comprises: first, power oscillation damping controller based on reactive power modulation and second, fast frequency response controller based on real power modulation, both of which are applied to the plant level controller of PV-STATCOMs. The proposed composite control is shown to successfully reduce frequency deviations, damp power oscillations, and provide voltage regulation both during over-frequency and under-frequency events. The proposed smart inverter control makes effective utilization of the PV inverter capacity and available solar power. For large power flows, the proposed control is shown to be superior than the conventional droop control recommended by North American Electric Reliability Corporation for generating plants. MATLAB/Simulink-based simulations are conducted on two-area power system using generic PV plant dynamic models developed by Western Electricity Coordinating Council, for a wide range of system operating conditions. Such grid support functionality is expected to bring new revenue making opportunities for PV solar farms.
77 citations
TL;DR: It is shown that the proposed PV-STATCOM control mitigates FIDVR even if solar farm is located more than 100 km from motor loads, is more effective than reactive power support required by German Grid Code and is equally effective as a STATCOM connected locally at motor loads.
Abstract: This paper presents a novel day-and-night control of large PV solar farm as STATCOM, termed PV-STATCOM, for FIDVR alleviation. The proposed control involves dynamic modulation of both reactive and real power during day, and of reactive power during night. The active and reactive power output of solar farm are based on the sensitivity of solar plant voltage to active and reactive power injections. Enhanced voltage control up to utility Transient Overvoltage Limit is utilized. Eigenvalue analysis is done to study the sensitivity of proposed controller performance to various power system and PV plant parameters. Extensive PSCAD simulation studies of FIDVR are performed in a realistic power transmission system with large-scale PV plant and comprehensive IM loads. It is shown that the proposed PV-STATCOM control: (i) mitigates FIDVR even if solar farm is located more than 100 km from motor loads, (ii) is more effective than reactive power support required by German Grid Code, (iii) is equally effective as a STATCOM connected locally at motor loads, and (iv) stabilizes motors at night which is beyond Grid Code requirements. The PV-STATCOM potentially provides significant cost savings to utilities and new revenue stream for solar plants in providing 24/7 FIDVR mitigation service.
23 citations
TL;DR: In this article, the impact of filters of grid voltage feed-forward signals on the coupling between dc-link voltage and ac voltage controllers in smart photovoltaic (PV) solar systems which are used for voltage control in distribution systems is studied.
Abstract: This paper presents a novel study of impact of filters of grid voltage feed-forward signals on the coupling between dc-link voltage and ac voltage controllers in smart photovoltaic (PV) solar systems which are used for voltage control in distribution systems. A comprehensive linearized state space model of a PV system including the dynamics of grid voltage feed-forward filters, dc-link voltage and ac voltage controllers is developed for the first time. This model is validated by electromagnetic transients software PSCAD/EMTDC. This model is used to identify the coupling between dc-link voltage and ac voltage controllers by eigenvalue and participation factor analyses. The impact of time constant of feed-forward filters on this coupling is studied by eigenvalue sensitivity analysis for PV systems with proportional and proportional integral type ac voltage controllers. The range of time constants over which the filters interact with controllers and create instability for systems with different strengths and X/R ratios is identified. Insights are provided on the choice of time constants of grid voltage feed-forward filters for the stable system design. The developed state-space model can also be used for impact studies of various other parameters, e.g., system strength, X/R ratios, types and gains of controllers, on system stability.
12 citations
09 Nov 2020
TL;DR: In this article, a review of case studies and operational experiences of smart inverters in increasing hosting capacity in real distribution systems, worldwide is presented, and a comparative evaluation of different smart inverter functions such as constant power factor, volt-var, and volt-watt in improving hosting capacity is presented.
Abstract: This paper presents a review of case studies and operational experiences of smart inverters in increasing hosting capacity in real distribution systems, worldwide The phenomenal increase in penetration of solar PV systems has caused several grid integration challenges Overvoltage due to active power injection by solar PV systems is a prominent factor that restricts hosting capacity of PV systems in distribution networks Smart inverter functions on PV inverters have been shown to obviate this challenge and enhance hosting capacity This paper presents a comparative evaluation of different smart inverter functions such as constant power factor, volt-var, and volt-watt in improving hosting capacity Key takeaways from various simulation studies and operating experiences of smart inverters in actual distribution systems across the world are described This paper provides useful insights to utilities in understanding the impact of smart inverters for improving PV hosting capacity in their distribution systems
9 citations
02 Aug 2020
TL;DR: In this paper, a new smart inverter control of battery energy storage systems (BESS) and PV solar system as STATCOMs, both during night and day, is proposed to reduce system energy demand by simultaneous optimization of line loss and conservation voltage reduction.
Abstract: This paper presents a novel concept of system energy demand reduction by simultaneous optimization of line loss reduction and Conservation Voltage Reduction (CVR). This is accomplished by a new smart inverter control of Battery Energy Storage Systems (BESS) and PV solar system as STATCOMs, both during night and day. Both the BESS and PV systems provide dynamic voltage control utilizing inverter capacities available after real power exchange, for reactive power control. The combination of BESS and PV system enhances the total available reactive power capacity for voltage control more than with BESS alone for achieving the above-stated objective. The effectiveness of the proposed control is demonstrated on a modified IEEE 14 bus system using optimal power studies performed with PSS/E software. With the rapid growth of PV systems and BESS in power systems, the proposed combined smart inverter control of BESS and PV systems can be effectively employed to reduce overall system energy demand.
4 citations
TL;DR: The proposed PV-STATCOM control is a substantially cost-effective alternative to the installation of expensive STATCOMs or static var compensators for stabilizing critical motors.
Abstract: New multimode control for PV-STATCOM operation of a photovoltaic (PV) solar plant is presented for preventing the instability of remotely located critical induction motors (IMs) whose shutdown during faults can cause significant financial loss to industries. The proposed control operates in four different modes that are determined by PV plant voltage, IM terminal voltage, and high-voltage ride-through limits of the PV plant. The proposed PV-STATCOM control ensures the stability of remote IM even if a PV plant is located up to 40 km away, a very large delay occurs in communicating motor terminal voltage to PV plant, and the system parameters and operating conditions vary over a wide range. The remote PV-STATCOM provides a similar motor stabilization as locally connected STATCOM. Furthermore, the PV plant with PV-STATCOM control can stabilize remote IM, while the dynamic current injection by PV plant as specified in grid codes’ fails to do so. The effectiveness of the proposed PV-STATCOM control is examined on a realistic distribution feeder in Ontario and is field demonstrated on a 10 kW PV plant in the network of Bluewater Power Distribution Corporation, Sarnia, ON, Canada. The proposed PV-STATCOM control is a substantially cost-effective alternative to the installation of expensive STATCOMs or static var compensators for stabilizing critical motors.
4 citations