Ram Krishan

Small signal stability analysis of grid connected distributed PV and wind energy system

Reliability and sustainability are the real problems of todays complex power systems. These challenges are met by increasing the renewable generation. With increase in penetration of renewable resources, mostly solar and wind generation, power systems are expected to experience changes in operational and dynamic characteristic. This work investigates the impact of penetration of distributed solar photovoltaic generation and DFIG based wind generation on small signal stability of power systems. In this paper, the eigenvalue analysis of proposed grid connected distributed photovoltaic generation and wind energy system is carried out to allocate the different modes (local mode, inter-area mode and critical mode) of the system. The simulation results with different cases demonstrate the effectiveness of the proposed approach.

An efficient approach to tune modern power system stabilizers using harmony search

A multiband power system stabilizer tuning method, in which objective is to enhance the damping of the rotor oscillations and system stability is proposed in this paper. This tuning approach is based on an efficient search algorithm known as harmony search algorithm. Robust design problem of PSS4B is considered as an optimization problem with nonlinear simulation based objective function. A single machine infinite bus (SMIB) system is evaluated under large range of loading conditions and disturbances for performance investigation of the proposed design. In order to demonstrate the effectiveness of designed PSS4B stabilizers, time domain simulations are carried out for SMIB system. Superiority of the proposed PSS4B design is proved by comparative study of transient responses with existing model of PSS4B.

Optimal Coordination of Overcurrent Relays Using Gravitational Search Algorithm With DG Penetration

Modern distribution systems consist of various distributed generators (DG) to make reliable power system. In this DG integrated distribution systems, coordination of overcurrent relays is a big challenge for protection engineers. At addition of DG, distribution system experiences change in the short circuit level of the system and thus earlier relay settings causes mal operation of relays. Nowadays, various programming optimization techniques are frequently used to find optimal relay settings of overcurrent (OC) relays. This paper presents a comparative study of Particle Swarm Optimization (PSO) and Gravitational Search Algorithm for the coordination of overcurrent relay for a system containing DG. A proper combination of primary and backup relay is selected to avoid mal operation of relays and unwanted outages when DG is penetrated. A four bus radial system is simulated in PSCAD/EMTDC platform and programming is done using MATLAB software.

Optimal coordination of overcurrent relays using gravitational search algorithm with DG penetration

Modern distribution systems consist of various distributed generators (DG) to make reliable power systems. In these DG integrated distribution systems, coordination of overcurrent relays is a big challenge for protection engineers. With the addition of DG, distribution system experiences change in the short-circuit level of the system and thus earlier relay settings causes mal operation of relays. Nowadays, various programming optimization techniques are frequently used to find optimal relay settings of overcurrent relays. This paper presents a comparative study of particle swarm optimization and Gravitational Search Algorithm for the coordination of overcurrent relay for a system containing DG. A proper combination of primary and backup relay is selected to avoid mal operation of relays and unwanted outages when DG is penetrated. Practical cases with different DG penetration level and fault types are also thoroughly discussed. A 4-bus radial system is simulated in PSCAD/Simulink platform and programming is done using MATLAB software.

Voltage regulation of residential DC distribution feeder using coordinated battery energy storage units

The active residential DC distribution feeder operation under integration of distributed solar photovoltaic generations (DSPVG) is expecting poor voltage profiles due to increasing demand of SPVG and load. This paper discusses, the dynamic droop based coordinated controlled voltage regulation approach to address the rise/drop of voltage in an active DC power distribution system (DCPDS). Modern DCPDSs are integrated with several SPVG and battery energy storage units (BESU). As in DCPDS, there is no reactive power, voltage profile can be regulated by controlling the active power injection into the system. During the peak generation of SPVG, charging of BESUs in DCPDS has been controlled based on state of charge (SoC) of the battery. Similarly, SoC based coordinated discharging approach has been presented during peak demands in reduced SPVG to support the voltage drop. A detailed investigation of voltage regulation of a residential DC distribution system (DCDS) is given to demonstrate the effectiveness of the proposed approach.

Design of Multi-Machine Power System Stabilizers with Forecast Uncertainties in Load/Generation

ABSTRACT Oscillatory instability in modern power system has increased due to increasing complexity and integration of dynamic loads. Stability analysis of such interconnected power system is very prominent in the presence of uncertain load/generation. In this paper, a power system stabilizer (PSS) design approach, which aims at enhancing the oscillatory stability of the multi-machine power system over the specified uncertainty range in forecasted load/generation, is presented. With non-statistical uncertainty, problem of selecting design parameters of the PSS is formulated as an optimization problem with minimization of eigenvalues and damping ratios based multi-objective function. In order to account the non-statistical uncertainties, a boundary active power loss (BAPL) based objective function is proposed. This non-linear BAPL objective function is minimized for determining the optimal setting of the generators voltage and taps of the online tap changing transformers (OLTC) under various power system constraints. In this paper, both the objective functions are solved by a new metaheuristic technique known as gray wolf optimization (GWO). Boundary value-based approach is used to minimize the repeated load flows under uncertain load/generation scenarios. Improved small-signal stability (SSS) is achieved with optimal active power loss of uncertain power system. Eigenvalue and time domain analysis for New England system are carried out under wide range of disturbances to demonstrate the potential of the proposed approach.

Robust tuning of power system stabilizers using hybrid intelligent algorithm

In this paper, a bio inspired hybrid algorithm namely bacterial foraging differential evolution (BFDE) is proposed for design of robust power system stabilizer (PSS) over wide range of operating and system conditions. The benefits of two optimization techniques are integrated in this hybrid algorithm. A multi objective optimization problem with eigenvalue based objective functions is solved for optimal tuning of PSS. The convergence with proposed BFDE algorithm is evaluated for investigation of robustness and effectiveness over the wide range of system conditions. Eigenvalue analysis and time domain responses against different type of disturbances for single machine infinite bus (SMIB) system are demonstrated.

An efficient multi objective optimization approach for robust tuning of power system stabilizers

This paper presents the robust tuning of power system stabilizer (PSS) with modified harmony search (MHS) algorithm. The problem of selecting appropriate design parameters of PSS is formulated as an optimization problem with minimization of eigenvalue based multi objective function. This objective function is optimized to alleviate the poorly damped or unstable oscillatory modes of the power system in order to meet the guaranteed stability. The proposed design of PSS under large disturbances includes the Integral of Time Square Error (ITSE) index in the objective function. The performance of proposed modified harmony search based PSS (MHSPSS) and robust modified harmony search based PSS (RMHSPSS) under different operating conditions and disturbances are investigated for Single Machine Infinite Bus (SMIB) system. The effectiveness of the approach is demonstrated with eigenvalue analysis and nonlinear time domain simulations for the given system.

A novel PV inverter control for maximization of wind power penetration

The active power distribution network operation with the integration of various renewable distributed generations (DGs), storage units, and dynamic loads are attracting a lot of interest due to substantial benefits in maximizing the penetration of available renewable energy resources (RES). However, the risk of voltage violation in the active distribution system (ADS) is exacerbated due to increasing penetration of DGs. It has become a bottleneck to maximize the DG penetration into the system. This bottleneck can be handled by effective voltage regulation and reactive power support into ADS. Nowadays, power electronic devices are frequently used for voltage and reactive power support over the conventional approaches. In this paper, an approach to maximize the penetration of RES, such as solar, wind, etc., into ADS by maximum utilization of existing solar photovoltaic inverters (SPVI) in the system is presented. Optimal utilization of SPVI may enhance the voltage stability of the ADS and wind power penetration into the system. The proposed SPVI control approaches are depended on active power generation of solar photovoltaic (SPVG), rating and capability of SPVI, and required reactive power in the ADS. In this paper, the problem of maximum penetration of RES is formulated as an optimal power flow embedded nonlinear optimization problem subject to the physical limitations of the SPVI. The results of the analysis performed on an IEEE 33 bus system show that the proposed SPVI control strategies can improve the voltage profile of the ADS with minimization of curtailment of wind power generation.