Energy management strategy for a renewable-based residential microgrid with generation and demand forecasting

Julio Pascual, Javier Barricarte, Pablo Sanchisa, Luis Marroyo.


This paper presents the management strategy for residential microgrid comprising of PV and wind turbines. By using forecasted data and correcting forecasting errors according to the SOC of the battery, the strategy manages to make a proper utilizaztion of the battery resulting in a better grid power profile.

NOTES:-

Introduction

-Microgrids include distributed generators, loads, energy storage which are controlled by one unit in order to exchange power with the grid. Addind renewable system to this can lower the cost and can provide better grid quality all around the world.

-Microgrids can be classified as either grid-connected or stand-alone. It will either have renewable generators, fossil fuel generators.

-In the field of stand-alone microgrids, when the only power sources are renewable energies, the ultimate goal is to manage the energy management system in order to keep the microgrid running and schedule different units in order to reduce the operating cost.


System description

-It consists of a grid-tied microgrid with the usual electric loads for a single-family home including a heating, ventilation and air conditioning (HVAC) system.

-PV and wind turbine are installed.

Simple moving average strategy

- Two strategies have been used: SMA(Simple moving average) and CMA(Central Moving average)

-In order to make power fluctuations smooth in power exchange with the grid low pass filter can be used.

-If the power profile changes one day to another in this case the energy balance of microgrid changes and has to be compensated by battery first. This will cause SOC of the battery to drift.

Central moving average (CMA) strategy: power forecasting

- The SMA causes lag in the grid. So, CMA is used instead of SMA. This will cause lag to disappear and there will not be any need to SOC control which will result in more better grid power profile.

Conclusion

This results in energy management strategy for a residential microgrid to obtain a smooth power profile for the energy exchange with the grid. The strategy makes use of forecasted power profiles in order to eliminate the lag in the grid power profile.


Feasibility study of renewable energy-based microgrid system in Somaliland׳s urban centers

Abdirahman Mohamed Abdilahi, Abdul Halim Mohd Yatim, Mohd Wazir Mustafa,Omar Tahseen Khalaf, Alshammari Fahad Shumran a, Faizah Mohamed Nor


This paper presents the management strategy for residential microgrid comprising of PV and wind turbines. By using forecasted data and correcting forecasting errors according to the SOC of the battery, the strategy manages to make a proper utilizaztion of the battery resulting in a better grid power profile.

NOTES:-

Introduction

-Microgrids include distributed generators, loads, energy storage which are controlled by one unit in order to exchange power with the grid. Addind renewable system to this can lower the cost and can provide better grid quality all around the world.

-Microgrids can be classified as either grid-connected or stand-alone. It will either have renewable generators, fossil fuel generators.

-In the field of stand-alone microgrids, when the only power sources are renewable energies, the ultimate goal is to manage the energy management system in order to keep the microgrid running and schedule different units in order to reduce the operating cost.


System description

-It consists of a grid-tied microgrid with the usual electric loads for a single-family home including a heating, ventilation and air conditioning (HVAC) system.

-PV and wind turbine are installed.

Simple moving average strategy

- Two strategies have been used: SMA(Simple moving average) and CMA(Central Moving average)

-In order to make power fluctuations smooth in power exchange with the grid low pass filter can be used.

-If the power profile changes one day to another in this case the energy balance of microgrid changes and has to be compensated by battery first. This will cause SOC of the battery to drift.

Central moving average (CMA) strategy: power forecasting

- The SMA causes lag in the grid. So, CMA is used instead of SMA. This will cause lag to disappear and there will not be any need to SOC control which will result in more better grid power profile.

Conclusion

This results in energy management strategy for a residential microgrid to obtain a smooth power profile for the energy exchange with the grid. The strategy makes use of forecasted power profiles in order to eliminate the lag in the grid power profile.

Hybrid PV-CHP Distributed System: design aspects and realization

M. S. Carmeli*, F. Castelli-Dezza**, G. Marchegiani***, M. Mauri**, L. Piegari*, D. Rosati*


The distributed generating system uses renewable energy, but due to the intermittency of the renewable energy they are combined with hybrid plants to combine more energy. This paper focuses on hybrid plants which uses internal combustion engine with cogeneration or tri-generation and PV technology. This paper also put light on analysing the power flow control strategies. Due to very low efficeincy of PV technology they are combined with conventional non-renewable ones to improve the performance and efficiency.

NOTES:-

There are three families for Distributed Generation System (DGS):

Standalone Systems (SAS):
  • This are used to supply to remote locations which are not connected to the main grid. in such case they usually combine one or more renewable energy sources with conventional energy sources. The hybrid system assure uninterrupted power supply even when renewable energy does not operate.


Grid connected systems (GCS):
  • They operate in only grid connected mode. They are connected with one or more renewable sources.
  • By using one or more energy sources provides higher stability of power supply.
  • In GCS very small storage is equipped, in order to contribute system transient stability.


Mixed operating mode systems (MOS).:
  • They operate in grid connection mode combined with one or more renewable sources along with storage device(Battery).
  • The battery is used to supply energy during emergency period.


Hybrid System Configuration.:
  • In this PV is combined with CHP unit. It is also equipped water heat storage.
  • CHP unit has small size battery and braking resistance which are shunt connected.
  • The shunt element have three functions.

a) They allow CHP to start even in the absence of the mains.

b) they allow to store excess energy in the standalone mode.

c)They provide transient stability to the CHP system.

If shunt unit is not connected then:

a) We obtain poor dynamic response.

b)In standalone mode, if there is demand for increase in load, it wont be able to fulfill the requirement.


Hybrid system components:

- CHP unit:

  • The natural gas, fuel for Internal Combustion Engine(ICE) to generate mechanical energy by combustion of fuel. The Induction machine connected to ICE converts mechanical energy to electrical energy.
  • Thermal recovery unit recovers thermal energy using heat exchanger. The heat generated during the process produces hot water which is stored in water heat storage. The heat storage unit has temperature sensors.


- PV unit:

  • It has different PV arrays. The output is DC which is connectedd to the common DC-bus. Chopper(DC-DC converter) is used. The DC is converted to AC(inverter).


- Battery Bank:

  • It is connected to the DC-bus. This Bi-directional Chopper. So, it can supply power in both directions, form DC bus to battery during charging of battery and from battery to DC bus during discharging.
  • There are two charging steps:

1) Constant current-Bulk condition.

2) Constant Voltage- Boost condition.


-Supervisor control unit:

It has two main tasks:

  • Controls input of PV, CHP and Battery bank.
  • Controls heat storage unit and battery power flow.

There are two operation modes:

1) Normal operation mode: In this mode the whatever power PV unit is generated is fed into the load. The CHP unit priority is to satisfy thermal demand. If CHP generates more power than required by heat demand, it stores it in battery bank.

2) Standalone operation: In this mode grid is not connected. The hybrid system gives priority to fulfill the electric demand. Advantage is this operation does not require energy storage device.

The mode changing is controlled by supervisor control unit.

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