# Optimal Operation and Management of Smart Grid System with LPC and BESS in Fault Conditions

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## Abstract

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## 1. Introduction

- Case 1: BESS management is provided; the simulation can be divided into two operation modes. One operation is the normal operation, which is optimized from the loss reduction aspects. The second mode provides continuous power supply in a disconnected fault situation.
- Case 2: An LPC reconfiguration system is proven to supply energy in an outage. In terms of a fault, electrical power is supplied from the installed DGs, and an optimized reconfiguration is demonstrated in some configurations.
- Case 3: The smart grid with the adopted LPC can be seen as an active smart grid system; the active smart grid is reconstituted in order to minimize distribution losses in real time.

## 2. Reliability and Stable Power Supply

## 3. Control Devices and Configuration

#### 3.1. LRT and SVRs

#### 3.2. BESS

#### 3.3. PV System

#### 3.4. LPC

#### 3.5. Home BESS

## 4. Formulation of the Modeling and Optimization Method

#### 4.1. Modeling of the Distribution System

#### 4.1.1. The Objective Function and Constraints

#### Objective Function

#### Constraints

## 5. Adaptive Inertia Weight PSO Method for the Decision Making of the Optimal Operation Schedule

#### 5.1. Particle Swarm Optimization

- Step 1:
- Generate an initial searching point for each swarm.
- Step 2:
- Evaluate the objective function using each swarm’s searching point.
- Step 3:
- Finish searching if the stopping conditions are satisfied. If not, go to Step 4.
- Step 4:
- Search the next point considering the best of the current swarm’s searching points, as well as each swarm’s best searching point. Go to Step 2.

#### 5.2. Flexible Inertia Strategy of PSO

#### 5.3. Scheduling Method for Reconfiguration

## 6. Simulation Results

#### 6.1. Simulation Model

- Case 1:
- BESS 1 is installed at the interconnection point to protect the upper high voltage system from reverse power flow. BESS 2 is installed in a branched office area as an emergency energy storage. In this case, BESS management is simulated in two modes of operation: operation Mode 1 is normal operation without a fault. On the other hand, when a disconnection fault occurs in the office area of Figure 6, islanding is applied by using BESS 2 as a power supply. As control devices for active and reactive power supply, BESS 1, BESS 2, LRT, SVR, SVC and inverters interfacing with the PVs are used. The results of each mode in Case 1 are provided in Figure 7 and Figure 8.
- Case 2:
- In this case, LPCs are installed instead of BESSs in a fault situation. Moreover, the home BESS is introduced in DG nodes to supply reactive power. A three line disconnection fault will be considered. The fault locations and some examples of active smart grid configurations are shown in Figure 9 and Figure 10, respectively. The comparison of active smart grid is presented as Figure 11, Figure 12, and Table 3. To note this case, LPCs run only in fault conditions.
- Case 3:
- The six LPCs are installed in the smart grid system as shown in Figure 13. Case 3 is different from Case 2 in that the system configuration will be changed in real time as a one-hour step. A reconfiguration operation of the active smart grid is optimized to minimize distribution losses. In order to solve the complex optimization including CP, a dual scheduling method is applied to the system.

#### 6.2. Case Studies

#### 6.2.1. Case 1: BESSs Management

#### 6.2.2. Case 2: Prevention of Local Outage by LPC Operation

#### 6.2.3. Case 3: Optimal Active Smart Grid System Design Using LPCs

## 7. Conclusions

## Author Contributions

## Conflicts of Interest

## Nomenclature

AIW | Adaptive inertia weight |

BESS | Battery energy storage system |

CP | Combinatorial problem |

DG | Distributed generator |

DisCo | Distribution company |

EV | Electric vehicle |

LRT | Load ratio transformer |

MPPT | Maximum power point tracking |

NAS | Liquid sodium (Na) and sulfur (S) |

PSO | Particle swarm optimization |

PV | Photovoltaic |

RES | Renewable energy source |

SOC | State of charge |

SVC | Static var compensator |

SVR | Step voltage regulator |

WG | Wind turbine generator |

η | Charging and discharging efficiency of large BESS. |

$\mathbb{L}$ | LPCs connection set. |

ζ | SOC of house BESSs, BESS and EVs. |

${B}_{ki}$ | Imaginary part of admittance ${Y}_{ki}$. |

${c}_{1}$ | Weight for the position of the current best particle. |

${c}_{2}$ | Weight for the best position of the particle swarm. |

${C}_{LB}$ | Capacity of large BESS. |

${G}_{ki}$ | Real part of admittance ${Y}_{ki}$. |

$gbest$ | Best position of the particle swarm. |

${m}_{i}$ | Adjustment value of the inertia weight at generation h. |

${n}_{h}$ | Particle number n at generation h. |

${N}_{node}$ | Node number of the distribution system. |

${P}_{f}$ | Active power flow at the interconnection point. |

${P}_{f}^{min},{P}_{f}^{max}$ | Lower and upper limit of the active power flow at the interconnection point. |

${P}_{k}^{G}$ | Active power from the k node generator. |

${P}_{k}^{L}$ | Load demand at the k node. |

${P}_{LBinv}^{*}$ | Order value of the active power output of BESS from DisCo. |

${P}_{LBinv}^{min},{P}_{LBinv}^{max}$ | Lower and upper limit of the active power of large BESS inverter. |

${P}_{LB}$ | Active power output of large BESS. |

${P}_{Li}$ | Distribution loss at node i. |

${P}_{Loss,i}$ | Active power loss of node i. |

${P}_{PVinv}$ | Active power output from the PV generator system. |

${P}_{PV}$ | Active power output from the PV panel. |

$pbest$ | Position of the current best particle. |

${Q}_{DRm}$ | Reactive power output of inverters interfaced with home BESS. |

${Q}_{DRm}^{min},{Q}_{DRm}^{max}$ | Lower and upper limit of the home battery inverter regarding reactive power output. |

${Q}_{f}$ | Reactive power flow at the interconnection point. |

${Q}_{f}^{min},{Q}_{f}^{max}$ | Lower and upper limit of the reactive power flow at the interconnection point. |

${Q}_{k}^{G}$ | Reactive power from the k node generator. |

${Q}_{k}^{L}$ | Load demand at the k node. |

${Q}_{LBinv}$ | Reactive power output of large BESS. |

${Q}_{LBinv}^{*}$ | Order value of the reactive power output of BESS from DisCo. |

${Q}_{LBinv}^{min},{Q}_{LBinv}^{max}$ | Lower and upper limit of the reactive power output of large BESS inverter. |

${Q}_{PVinv}$ | Reactive power output of inverters interfaced with PV. |

${Q}_{PVinv}^{*}$ | Order value of reactive power. |

${Q}_{PVinv}^{min},{Q}_{PVinv}^{max}$ | Lower and upper limit of the PV inverter regarding reactive power output. |

${R}_{ki}$ | Resistance between node k and i. |

$ran{d}_{1}$ | Uniform random numbers from 0–1. |

${S}_{h+1}$ | Search position of the i-th particle in the h-th search. |

${S}_{LBinv}$ | Inverter capacity of large BESS. |

${S}_{PVinv}$ | Inverter capacity of the PV inverter. |

t | Time step at optimization. |

${T}_{k}$ | Tap positions of LRT and SVR. |

${T}_{k}^{min},{T}_{k}^{max}$ | Lower and upper tap limit of LRT and SVRs. |

${V}_{h+1}\left(i\right)$ | i-th particle velocity in the $h+1$-th search. |

${V}_{min},{V}_{max}$ | Minimum and maximum of the voltage constraints. |

${V}_{m}$ | Node voltage at node m. |

w | Weight of inertia. |

${w}_{i}$ | Updated inertia weight value. |

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**Figure 7.**Simulation results of Case 1 without fault (operation Mode 1); all control devices’ operations are listed as: (

**a**) node voltage; (

**b**) reactive power output by inverters interfacing the PV; (

**c**) active power flow at the interconnection point; (

**d**) reactive power flow at the interconnection point; (

**e**) active power output of each large BESS; (

**f**) states of charge of each large BESS; (

**g**) reactive power output of BESS 1; (

**h**) reactive power output of BESS 2; and (

**i**) tap positions of the LRTs and SVRs.

**Figure 8.**Simulation results during fault in Case 1: (

**a**) node voltage; (

**b**) reactive power output of inverters interfacing the PVs; (

**c**) active power flow at the interconnection point; (

**d**) reactive power flow at the interconnection point; (

**e**) active power output of each large BESS; (

**f**) states of charge of each large BESS; (

**g**) reactive power output of BESS1; (

**h**) reactive power output of BESS2; and (

**i**) tap positions of LRT and SVRs.

**Figure 10.**Examples of the active smart grid system: (

**a**) end Node 16 is connected to end Node 35 in Case 2 (i); and (

**b**) end Node 16 is connected to end Node 24 of the office area in Case 2 (v).

**Figure 11.**Simulation results of Case 2 (0): (

**a**) node voltages; (

**b**) reactive power outputs from interfacing inverter of the PV; (

**c**) reactive power output by demand response; and (

**d**) tap positions of LRT and SVRs.

**Figure 12.**Simulation results considering a line fault in Case 2 (v): (

**a**) node voltages; (

**b**) reactive power output from the inverter interfacing the PV; (

**c**) reactive power output by demand response; (

**d**) tap position of LRT and SVRs; and (

**e**) comparison of distribution losses.

**Figure 14.**Examples of the distribution system configuration in Case 3 illustrated as: (

**a**) the reconstructed distribution model of Case 3 (i); and (

**b**) the reconstructed distribution model of Case 3 (vi) listed in Table 4.

**Figure 15.**Simulation results of Case 3 (vi): (

**a**) node voltages; (

**b**) reactive power output from the inverter interfacing the PV; (

**c**) reactive power output by demand response; and (

**d**) tap positions of LRT and SVRs. Note that the reconstruction distribution system of Case 3 (vi) represents the most reduced distribution losses.

**Figure 16.**Simulation results of the proposed method of Case 3: (

**a**) node voltages; (

**b**) reactive power output from inverter interfacing the PV; (

**c**) reactive power output by demand response; (

**d**) tap positions of LRT and SVRs; and (

**e**) comparison of distribution losses.

System or Installed Devices | Capacities |
---|---|

Line impedance at each section | $0.04+j0.04$ pu |

Rated capacity of PV nodes | $0.08$ pu (400 kW) |

Rated capacity of the inverter interfacing with the PV | $0.08$ pu (400 kW) |

Capacity of BESSs 1 and 2 | $5.0$ pu (25 MWh) |

Rated capacity of the inverter interfacing BESS 1 and BESS 2 | $0.4$ pu (2 MW) |

Simulation Contents | |
---|---|

Case 1 | BESS management in normal operation mode without fault (operation Mode 1). |

BESS management of emergency operation mode with disconnection fault (operation Mode 2). | |

Case 2 | Distribution loss analysis of local outage by disconnection fault. |

(LPCs are operated when an outage happens) | |

Case 3 | Reconfiguration management of active smart grid using LPCs. |

Make the decision of optimal operation throughout whole day. |

Simulation | Disconnected | Connecting Nodes | Time of Fault | Distribution Losses |
---|---|---|---|---|

Pattern | Area | by LPC | Occurrence | (kWh) |

Case 2 (0) | - | - | - | 652.2 |

Case 2 (i) | Nodes 14–31 | Nodes 16–35 | 14 o’clock | 1040 |

Case 2 (ii) | Nodes 24–35 | 1047 | ||

Case 2 (iii) | Nodes 12–21 | Nodes 16–24 | 707.5 | |

Case 2 (iv) | Nodes 35–24 | 631.8 | ||

Case 2 (v) | Nodes 12–13 | Nodes 16–24 | 438.5 | |

Case 2 (vi) | Nodes 35–24 | 603.5 | ||

Case 2 (vii) | Nodes 14–31 | Nodes 16–35 | 11 o’clock | 961.9 |

Case 2 (viii) | Nodes 24–35 | 993.6 | ||

Case 2 (ix) | Nodes 12–21 | Nodes 16–24 | 763.4 | |

Case 2 (x) | Nodes 35–24 | 893.9 | ||

Case 2 (xi) | Nodes 12–13 | Nodes 16–24 | 450.8 | |

Case 2 (xii) | Nodes 35–24 | 624.6 |

Simulation Pattern | Connecting LPCs | Distribution Losses (kWh) |
---|---|---|

Case 3 (i) | 1, 2, 3 | 652 |

Case 3 (ii) | 1, 2, 5 | 1343 |

Case 3 (iii) | 1, 2, 6 | 1490 |

Case 3 (iv) | 2, 3, 4 | 1128 |

Case 3 (v) | 2, 3, 6 | 1617 |

Case 3 (vi) | 1, 3, 4 | 450 |

Case 3 (vii) | 1, 3, 6 | 1116 |

Optimal reconfiguration schedule of active smart grid | |||||||||
---|---|---|---|---|---|---|---|---|---|

Time | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |

Distribution construction | (vi) | (i) | (i) | (i) | (i) | (vi) | (vi) | (i) | (i) |

Time | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 |

Distribution construction | (vi) | (vi) | (iv) | (vi) | (vi) | (iv) | (vi) | (vii) | (i) |

Time | 19 | 20 | 21 | 22 | 23 | 24 | Distribution losses | ||

Distribution construction | (vii) | (vii) | (vii) | (vii) | (vii) | (vii) | 412.7 kWh |

© 2016 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Shigenobu, R.; Noorzad, A.S.; Muarapaz, C.; Yona, A.; Senjyu, T.
Optimal Operation and Management of Smart Grid System with LPC and BESS in Fault Conditions. *Sustainability* **2016**, *8*, 1282.
https://doi.org/10.3390/su8121282

**AMA Style**

Shigenobu R, Noorzad AS, Muarapaz C, Yona A, Senjyu T.
Optimal Operation and Management of Smart Grid System with LPC and BESS in Fault Conditions. *Sustainability*. 2016; 8(12):1282.
https://doi.org/10.3390/su8121282

**Chicago/Turabian Style**

Shigenobu, Ryuto, Ahmad Samim Noorzad, Cirio Muarapaz, Atsushi Yona, and Tomonobu Senjyu.
2016. "Optimal Operation and Management of Smart Grid System with LPC and BESS in Fault Conditions" *Sustainability* 8, no. 12: 1282.
https://doi.org/10.3390/su8121282