Manoj Datta

A Coordinated Control Method for Leveling PV Output Power Fluctuations of PV–Diesel Hybrid Systems Connected to Isolated Power Utility

A photovoltaic (PV) systems power output is not constant and fluctuates depending on weather conditions. Fluctuating power causes frequency deviations and reduction in reliability of the isolated power utility or microgrid when large output power from several PV systems is penetrated in the utility. In this paper, to overcome these problems, a simple coordinated control method for leveling the fluctuations of combined power output from multiple PV systems is proposed. The conflicting objective of output power leveling and acquisition power increase is achieved by means of the proposed method. Here, output power command is generated in two steps: central and local. Fuzzy reasoning is used to generate the central leveling output power command considering insolation, variance of insolation, and absolute average of frequency deviation. In local step, a simple coordination is maintained between central power command and local power commands by producing a common tuning factor. Power converters are used to achieve the same output power as local command power employing PI control law for each of the PV generation systems. The proposed method is compared with the method where a modified maximum power point tracking control is used for smoothing the short-term change in each of the PV systems output. Simulation results show that the proposed method is effective for leveling output power fluctuations and feasible to reduce the frequency deviations of the isolated power utility to maintain reliability.

Fuzzy Control of Distributed PV Inverters/Energy Storage Systems/Electric Vehicles for Frequency Regulation in a Large Power System

This paper presents a fuzzy based frequency control strategy by the Megawatt (MW) class distributed PV systems and electric vehicles (EVs). The frequency control is proposed from the view point of the frequency fluctuation problem produced by the large penetration of PV power and sudden load variation. The fuzzy based frequency control has three inputs: average insolation, change of insolation and frequency deviation. Following these three inputs, a frequency control system for the distributed PV inverters is proposed. For the case of different insolations in the different areas of the power system, a coordinated control method of the distributed PV inverters, energy storage systems (ESSs) and EVs is presented. The proposed method is simulated by considering dual power and information flows between supply and demand sides in a large power system and is found satisfactory to provide frequency control and to reduce tie-line power fluctuations.

Photovoltaic Output Power Fluctuations Smoothing by Selecting Optimal Capacity of Battery for a Photovoltaic-Diesel Hybrid System

Abstract This article explains a battery-based control method to reduce the photovoltaic output power fluctuations, which, in turn, will reduce the frequency deviations of the power system. The battery control method introduced here will maintain the state of charge near 50%. Therefore, it will increase the lifetime of the battery, as well as decreasing the maintenance cost. A local search algorithm is provided with this battery control method to search the optimal capacity of the battery required for smoothing the photovoltaic output power fluctuations. Then, a cost comparison is provided to realize the performance of the search algorithm. To verify the effectiveness of the proposed method, simulation results are presented using the actual insolation and load data.

A Control Method for Small Utility Connected Large PV System to Reduce Frequency Deviation Using a Minimal-Order Observer

In this paper, a minimal-order observer-based control method is proposed for small power utility connected photovoltaic (PV) systems. In the proposed method, the PV power is controlled according to load variation to minimize the frequency deviation. Load power and diesel power are estimated successfully by a minimal-order observer. From the estimated load power, load variation index is calculated. A second-order low-pass filter is used to produce PV base power from available maximum PV power. Then, the PV base power is added with the load variation index to generate the command PV power. The proposed method is compared with the method where maximum power point tracking control is used to produce the command PV power. From simulation results, it has been found that the proposed method is effective to reduce the frequency deviation of the utility and also delivers PV power near maximum PV power.

LFC by coordinated virtual inertia mimicking and PEVs in power utility with MW-class distributed PV generation

This paper presents a load frequency control (LFC) by using distributed energy storage systems (ESSs) and plug-in electric vehicles (PEVs) in a large power system with MW-level distributed PV generation. The ESSs are controlled to mimic virtual inertia. Controls are done in two levels: central and local. An optimal virtual inertia is calculated considering the total PV power variation in a control area. Based on this, central ESS power command is decided and by coordination, this central ESS power command is distributed to the local ESSs to emulate the optimal virtual inertia. PEVs are used for the LFC considering user convenience, availability and state of charge (SOC) of the batteries. Effectiveness of the proposed method to provide LFC is verified by numerical simulation results.

Control of MW-class PV generation to reduce frequency and tie-line power fluctuations in three control area power system

This paper presents a frequency control strategy by grid-connected MW class PV generation. The frequency control is proposed based on a load power estimator from the view point of the frequency fluctuation problem. The proposed method is simulated in three control area power systems by considering large penetration of PV generation and is compared with the conventional battery based PV power fluctuations smoothing method. From numerical simulation results, it is found that the proposed method is satisfactory to provide frequency control and to reduce tie-line power fluctuations.

Output Power Coordination Control for Wind Farm in Small Power System

Nowadays, wind turbine generator (WTG) is increasingly required to provide control capabilities regarding output power. Under this scenario, this paper proposes an output power control of wind farm (WF) using pitch angle control connected to small power systems. In this control approach, WF output power control is achieved by two control levels: central and local. In central control, WF output power command is determined by fuzzy reasoning which has three inputs for average wind speed, variance of wind speed, and absolute average of frequency deviation. Then, local output power commands of each WTG are given by WF output power command and coordination control, and each WTG ensures WF output power command. The simulation results by using an actual detailed model for wind power system show the effectiveness of the proposed method.

A frequency control method for isolated photovoltaic-diesel hybrid power system with use of full renewable energy

In this paper, a frequency control method is introduced for photovoltaic-diesel hybrid system by using a load estimator and an energy storage system. The proposed method is compared with a fuzzy based frequency control method. Simulation results show that the proposed method is feasible to reduce the frequency deviations of the isolated power utility and delivers maximum power compared to the fuzzy based method.

A fuzzy based control method for isolated power utility connected PV-diesel hybrid system to reduce frequency deviation

A Photovoltaic (PV) systempsilas power output is not constant and fluctuates depending on weather conditions. Fluctuating power causes frequency deviations in the power utilities when PV power penetration is large. Using a battery is the common practice to smooth PV output power fluctuations. In this paper, we propose a new and simple fuzzy based control method for PV-diesel hybrid system to reduce frequency deviations without smoothing PV output power fluctuations. By means of the proposed method, output power control of PV system considering the conditions of power utilities and maximizing energy capture are achieved. Here, fuzzy reasoning is used to generate the PV output power command. This fuzzy reasoning has three inputs of average insolation, change of insolation, and frequency deviation. The proposed method is compared with the method where extracted maximum power is given to the utility. The simulation results show that proposed method is effective to reduce the frequency deviation of isolated power utility and delivers power near maximum PV power.

A new method for smoothing output power fluctuations of PV system connected to small power utility

A photovoltaic (PV) systempsilas power output is not constant and fluctuates depending on weather conditions. Fluctuating power causes frequency deviations in the power utilities when PV power penetration is large. Using a battery is one feasible measure to stabilize a PV systempsilas power output, but it requires additional costs and results in additional waste of used batteries. In this paper, to overcome these problems, we propose a new method for leveling the fluctuations in a PV systempsilas power output. By means of the proposed method, output power control of PV system considering the conditions of power utilities becomes possible and the conflicting objective of output power leveling and maximizing energy capture are achieved. Here, fuzzy reasoning is used to generate the output leveling power command. This fuzzy reasoning has three inputs of average insolation, variance of insolation, and absolute average of frequency deviation. Power converter is used to achieve output power same as command power employing PI control law. The proposed method is compared with the method where extracted maximum power is given to the utility without leveling. The simulation results show that proposed method is effective for leveling output fluctuations and feasible to reduce the frequency deviation of the small power utility.