Sathish Kumar Kollimalla

Design and Analysis of Novel Control Strategy for Battery and Supercapacitor Storage System

In this paper, a simple novel control strategy is designed and analyzed for a hybrid energy storage system (HESS). In the proposed method, batteries are used to balance the slow changing power surges, whereas supercapacitors (SC) are used to balance the fast changing power surges. The main advantage of the proposed control strategy is that, the slow response of battery system including dynamics of battery, controller, and converter operation, is overcome by diverting the power surges to the SC system. The proposed method inherits charge/discharge rate control to improve the life span and reduce the current stresses on battery. The proposed method features less computational burden as it uses simple control strategy. The detailed experimental results presented validate the proposed control strategy for sudden changes in photovoltaic (PV) generation and load demand.

Variable Perturbation Size Adaptive P&O MPPT Algorithm for Sudden Changes in Irradiance

In this paper, a variable perturbation size adaptive perturb and observe (P&O) maximum power point tracking (MPPT) algorithm is proposed to track the maximum power under sudden changes in irradiance. The proposed method consists of three algorithms, namely current perturbation algorithm (CPA), adaptive control algorithm (ACA), and variable perturbation algorithm (VPA). CPA always tries to operate the photovoltaic (PV) panel at maximum power point (MPP). ACA sets the operating point closer to MPP, only if the operating limits are violated. These operating limits are expressed in terms of the operating current range of the PV panel and the sudden changes in irradiance. VPA dynamically reduces the perturbation size based on polarity of change in power. Two-stage variable size perturbation is proposed in this paper. The proposed algorithm is realized using a boost converter. The effectiveness of proposed algorithm in terms of dynamic performance and improved stability is validated by detailed simulation and experimental studies.

A Novel Adaptive P&O MPPT Algorithm Considering Sudden Changes in the Irradiance

In this paper, a short-circuit current-based adaptive perturb and observe maximum power point tracking algorithm is proposed to extract the maximum power from photovoltaic (PV) panel under sudden changes in the irradiance. This scheme is divided into two algorithms: 1) current perturbation algorithm; and 2) adaptive control algorithm. The current perturbation algorithm makes the PV panel operate at maximum power point. The adaptive control algorithm identifies the operating limit violation and sets a new operating point nearer to maximum power point. These limits are derived in terms of changes in the irradiance and current. The new operating point is set by estimating the short-circuit current. This algorithm proposes variable current perturbation, which varies continuously with the irradiance. A boost converter is used to realize the proposed algorithm. The proposed algorithm is compared with a conventional algorithm and validated for sudden changes in the irradiance through the experimental results.

Dynamic energy management of micro grids using battery super capacitor combined storage

The energy flow between source and the load of micro grid must be balanced to have a constant dc grid voltage. Due to intermittency in the natural sources and the variations in load, energy balance operation demands storage. The commonly preferred choice of energy storage in micro grid is valve regulated lead acid batteries. When batteries are used as energy storage, due to its low power density, the charge and discharge rate is low. It causes severe stress on the battery under quick load fluctuations and results in increase in the number of charge/discharge cycles. Hence, the lifetime of the battery reduces. The super capacitors have high power density and it can react speedily to quick load fluctuations. However, super capacitors alone cannot be used as energy storage as it cannot supply load for a longer time. Hence, this paper proposes a combined energy storage using batteries and super capacitors with high energy and power density. The photovoltaic (PV) based micro grid with combined energy storage is designed and the control strategy is validated for different atmospheric and load conditions.

Adaptive perturb & observe MPPT algorithm for photovoltaic system

Maximum power point tracking (MPPT) techniques are used in photovoltaic (PV) systems to extract maximum power from the PV module. There are number of techniques available in literature. Perturb and observe (P &O) method is widely used because of its low-cost and ease of implementation. The P&O method oscillates close to maximum power point (MPP), when atmospheric conditions are constant or slowly varying. However, when irradiance and temperature are changing rapidly, this method fails to track MPP with rapid speed. In order to consider rapidly varying atmospheric conditions an adaptive control algorithm is proposed, by measuring the short circuit current at different irradiance levels and temperatures. In this proposed method current perturbation is considered instead of voltage perturbation. The proposed method has faster dynamics and improved stability compared to the conventional P&O method. The effectiveness of proposed MPPT algorithm is verified using digital simulations.

Novel adaptive P&O MPPT algorithm for photovoltaic system considering sudden changes in weather condition

The output power of the PV system continuously varies with change in irradiance and temperature. At a specified irradiance and temperature, the output power of the PV system can be varied from zero to maximum depending on the operating voltage and current. There are number of maximum power point tracking (MPPT) methods available in literature to operate the PV system at maximum power point (MPP). Among different MPPT methods, perturb and observe (P&O) method is widely used because of its low-cost and ease of implementation. When irradiance and temperature are constant or slowly varying, the P&O method tracks MPP steadily. However it fails to track MPP with rapid speed, for rapidly varying irradiance and temperature. In order to consider rapidly varying atmospheric conditions an adaptive control algorithm is proposed, by estimating the short circuit current. In this proposed method, current perturbation is considered to improve the tracking speed. The effectiveness of proposed MPPT algorithm in terms of faster dynamics and reduced oscillations compared to conventional P&O algorithm is verified using digital simulations.

A new adaptive P&O MPPT algorithm based on FSCC method for photovoltaic system

Maximum power point tracking (MPPT) techniques are used in photovoltaic (PV) systems to extract maximum power from the PV module. There are number of techniques available in literature. In this paper, an adaptive P&O MPPT algorithm is proposed using conventional perturb and observe (P&O) and fractional short circuit current (FSCC) methods. P&O method is widely used because of its low-cost and ease of implementation. The P&O method oscillates close to maximum power point (MPP), when atmospheric conditions are constant or slowly varying. However, when irradiance and temperature are changing rapidly, this method fails to track MPP with rapid speed. In order to consider rapidly varying atmospheric conditions an adaptive control algorithm is proposed, by measuring the short circuit current at different irradiance levels and temperatures. In this proposed method current perturbation is considered instead of voltage perturbation. The proposed method has faster dynamics and improved stability compared to the conventional P&O method. The effectiveness of proposed MPPT algorithm is verified using digital simulations.

Coordinated control and energy management of hybrid energy storage system in PV system

The present work deals with development of new control strategy for hybrid energy storage system (HESS), consisting of photovoltaic (PV) system, battery, supercapacitor (SC) and load. Due to the variable characterstics of non-conventional power generation and variable load demand, batteries can undergo irregular, partial charge/discharge cycles. It has detrimental effects on battery life span and rating. The proposed strategy uses the DC bus voltage and battery state of charge (SOC) for charging/discharging of battery. In the proposed method, the battery system is coordinated with SC by diverting short-term charge/discharge cycles to SC if the SOC is within the limits. In case of SOC limit violation, battery SOC is controlled by diverting charge/discharge currents to SC. The digitial simulation results are presented and discussed to verify the validity of the proposed control strategy.

A new control strategy for interfacing battery supercapacitor storage systems for PV system

In this paper, a new control strategy is proposed for hybrid energy storage system (HESS) for remote area power supply system consisting of PV, battery, supercapacitor (SC) and load. Since the PV generation and load demand varies continuously, batteries can undergo irregular, partial charge/discharge cycles. It has detrimental effects on battery life span and rating. Therefore in the proposed method, batteries are used to balance the low frequency power surges, because of its low power density and low charge/discharge rates. Whereas SCs are used to balance the high frequency power surges, because of its high power density and high charge/discharge rates. The control of the battery system is coordinated with SC to improve the life span and reduce the stress on battery. The proposed control strategy is compared with the conventional strategy and validated for sudden changes in PV generation and load demand through digital simulation.

DC Grid Voltage Regulation Using New HESS Control Strategy

The power generation from renewable power sources is variable in nature, and may contain unacceptable fluctuations in case of the wind power generation. High fluctuations in power generation may negatively impact the voltage stability of the microgrid. This problem can be alleviated by using hybrid energy storage system consisting of batteries and supercapacitors (SCs) at DC grid. A new control scheme is proposed to control the power sharing between batteries and SCs to match the generation-demand mismatch and hence to regulate the grid voltage. In the proposed control strategy, the SC supplies error component of the battery current in addition to the fast transient power demand. This added feature not only improves the DC grid voltage regulation capability but also reduces the stress levels on the battery and hence increases the life span of the battery. The main advantage of the scheme is that, the uncompensated power due to slow dynamics of the battery is diverted to the SC and keeps the state of charge within the limits for longer duration, as compared to the conventional strategy. The proposed scheme is validated through detailed experimental studies.