Optimal Voltage Control in Distribution Network.

Jose Raul Castro Mendieta Director: Prof. Maarouf Saad

Codirector: Dr. Serge Lefebvre INER. November 2013

1

Outline

2

• Introduction

• Coordinated Voltage Control in Distribution Network

- Coordinated Voltage and Reactive Power Control in Distribution Networks

- Coordinated Voltage Control with Dynamic Weights

• Case Study

• Discussions

• Conclusions

Introduction

• The electric system has been planned and operated under fundamental assumption that the supply system must perfectly meet every customer’s energy use, and that the load is relatively uncontrolled.

• The voltage and reactive power equipment in distribution system are mostly operated based on an assumption that the voltage decrease along the feeder.

Introduction

• The equipment connected to the distribution network is becoming more diversified as Distributed Generation (DG), small energy storage, smart meters and control algorithms for voltage and VAR control.

Introduction • This could cause

operational problems to the distribution network, including: – Over-voltage on

distribution feeder (loss of voltage regulation).

– Increased short-circuit currents

– Incorrect operation of control equipment.

Energy flow of a distribution network in presence of DGs. (Ahmidi et al., 2012)

Coordinated Voltage Control in Distribution Network

• Three levels has been developed by some electric utilities to prevent voltage deterioration and to allow a better use of existing reactive power resources.

– Secondary voltage regulation (SVR) is an important level for improving power-system voltage dynamic performance, where voltage deviation at pilot buses is minimized.

A. Coordinated Voltage and Reactive Power Control in Distribution Network

• Multi-Objective function has three objectives: – Minimization of voltage at pilot bus – Minimization of reactive power production ratio deviation – Minimization of generators voltage deviation. (OLTC + DGs)

𝐹𝑜𝑏𝑗 𝑉𝑖𝑟𝑒𝑓

= 𝜆𝑖𝑖∈∝𝑃

𝑉𝑖𝑟𝑒𝑓

− 𝑉𝑖 − 𝐶𝑖 ,𝑘𝑉 · ∆𝑉𝑘

𝑘∈𝛼𝐺

2

+ 𝜆𝑖𝑞 𝑘 𝑞𝑟𝑒𝑓 −

𝑄𝑖

𝑄𝑖𝑀𝐴𝑋 − 𝐶𝑖 ,𝑘

𝑄 · ∆𝑉𝑘

𝑘∈𝛼𝐺

2

(1)

𝑖𝜖𝛼𝐺

+ 𝜆𝑖𝑣 𝑘 𝑉𝑖

𝑟𝑒𝑓− 𝑉𝑖 − Δ𝑉𝑖

2

𝑖∈∝𝐺

Subject to:

𝑄𝑖 ≤ 𝑄𝑖𝑚𝑎𝑥 ;

𝑉𝑖 ∈ 𝑉𝑖𝑚𝑖𝑛 ;𝑉𝑖

𝑀𝐴𝑋 𝑓𝑜𝑟 𝑖 ∈∝ 𝑃 ∪∝ 𝐺;

∆𝑉𝑖 ≤ ∆𝑉𝑖𝑀𝐴𝑋 𝑓𝑜𝑟 𝑖 ∈∝ 𝐺.

𝜆𝑖 + 𝜆𝑖 𝑞 + 𝜆𝑖

𝑣 = 1

(1) Richardot et al., 2006

B. Coordinated Voltage Control with Dynamic Weights

• CVC-DW uses the future values of load to find the value of voltage in the network.

• Optimizing the multi-objective function we will find the weights.

Figure 1. Calculation of dynamics weight.

B. Coordinated Voltage Control with Dynamic Weights

• If the forecasted voltage is within the limits, the priority will be to calculate the optimal reactive power and minimize losses.

• If the forecasted voltage is close to the limits, dynamics weight optimize the reactive power and regulate the voltage in OLTCs, so that the voltage is within the limits established.

• If the forecasted voltage have been exceeded , then the priority is to keep the voltage within limits.

Figure 2. Principle of dynamics weight (CVC-DW). IEEE 13 nodes system.

Case Study

• Step a): CVC-DW calculates the voltage according to the Load Forecasting Data. • Step b): CVC-DW calculates dynamics weight; the ideal voltage in the OLTC and

reactive power optimal. Pareto Optimal is used to optimize the function. • Step c): OLTC and reactive power cause changes in the voltage buses of the

network. With these new values, CVC-DW will perform a new iteration by calculating new dynamics weight, a new voltage for OLTC and a new optimal reactive power.

Figure 3. CVC-DW structure.

Case Study

Figure 4. Voltage 632 bus.

Table1. Comparison between Fixed weight and Dynamics weight.

Discussions

• The DGs are a source of active and reactive power that has to be embedded. CVC-DW allows adding new equipment and integrates to the control and optimization.

• This system may also adapt operating points, objectives and constraints to particular strategies.

Conclusions

• The introduction of new equipment connected to the distribution network creates voltage quality problems.

• The purpose of the CVC-DW is to minimize network losses while keeping the voltage within mandatory limits.

• With this new concept, OLTC works efficiently and the required reactive power is optimized throughout the network.

• CVC-DW will enable dynamic energy management that will yield energy savings.

• The result indicates that CVC-DW reduces the number of OLTC operations and of the voltage fluctuation in distribution network.

Conclusions

• Future work

– To simulate the presence of DGs and use the active and reactive power to maintain stable voltage and reduce network losses. The optimization will be for more period of time (e.g. an entire day).

– To test CVC-DW in IEEE 123 Node Test Feeder

– To simulate faults in the distribution network and analyse the results with other techniques.

Thanks

Gracias

OLTC

16

The load in the bus 671 increases. Tap= Change taps (OLTC) V1= Voltages in all buses. (Phase a) Q1=Reactive power in all buses. Q5=Total losses. OLTC= Make tap calculation Opendss2OLTC= Parameters Calculated for IEEE13 bus.

Load Shape

• Calculate the values of active and reactive power for 1 day.

Load Shape

Kw=Loadshape of Active power

Kvar=Loadshape of reactive power.