The mission of this group is to bring together utility professionals in the power industry who are in the thick of the digital utility transformation. 

Post

SMART GRID: EEFECTIVE REACTIVE POWER CONTROLLER

image credit: Dreamstime.com
Shehu Ibrahim Khaleel's picture
Electricity Policy and Regulatory Expert African Union Commission Department of Infrastructure and Energy

I am Renewable energy and power systems consultant, with 19-years professional experience. My special focus is on Renewable energy project development, Renewable Energy Project financing and...

  • Member since 2008
  • 5 items added with 3,452 views
  • Jul 9, 2021
  • 620 views

Utilities today devote considerable attention to managing voltage levels and reactive power

(VAR) throughout the power transmission and distribution systems. Loads that contain

capacitors and inductors such as electric motors, pool pumps, and the power supplies in

modern electronics put additional strain on the grid, as the reactive portion of these loads

causes them to draw more current than an otherwise comparable resistive load (such as a

light bulb) would draw for the same amount of kilowatts transferred. This extra current

causes the transformer to heat up, which wastes energy and reduces service lifetime.

Uncorrected reactive power makes it harder to stabilize grid voltage. It also drives additional

cost throughout the entire grid since everything wires, transformers, and generators must

be sized to carry the total current.

The more reactive power flowing on a line, the less “room” there is for real power and the

less efficient the transmission and/or distribution system will be.

Improving the efficiency of power transmission and distribution comes down to two

choices: you can reduce the resistance of the wires by making them larger or using better

materials (not a practical solution), or you can improve the effectiveness of the flow of

electricity. To address the latter, it’s important to understand one technical concept and

that is the difference between active and reactive power.

In the last 20 years, this problem has attracted interest from both academia and

industry and this has produced many special devices and algorithms. This article first

introduces reactive power sources and secondly the role of the smart grid to control and

improve the efficiency of power flows.

REACTIVE POWER SOURCES

The controllable reactive power sources include generators, shunt reactors, shunt

capacitors and On Load Tap Changers of transformers (OLTC).

Volt/VAr control

To optimize the movement of electric energy along the power lines, we would ideally like to

eliminate reactive power flows, or at least minimize them. Utilities do this on their local

distribution systems using devices such as capacitor banks or special transformers, typically

located at substations or on feeders. These devices work to keep reactive power flows

down, making the full capacity of the conductor available for real power. Generators: can generate or absorb reactive power depending on the excitation. When

over-excited they supply the reactive power, and when under-excited they absorb reactive

power. The automatic voltage regulators of generators can continually adjust the excitation.

Reactors, shunt capacitors, and OLTC: are traditionally switched on/off through circuit

breakers on command from the operator. Since the early eighties, advances in Flexible AC

Transmission Systems (FACTS) controllers in power systems have led to their application to

improve voltage profiles of power networks. The most frequently used devices are: Reactive

Power Controller (RPC) and Static Var Compensator (SVC).

The RPC connects or disconnects capacitor stages automatically by detecting the phase

divergence between the fundamentals of current and voltage. The measured divergence is

compared with several segmental set phase divergence regions, capacitor contractors will be

switched on or off according to it.

Compared with RPC, the SVC is more advanced electronics equipment. It can provide

continuous capacitive and inductive reactive supply to the power system. The SVC typically

consists of a Thyristor Controlled Reactor (TCR), a Thyristor Switched Capacitor (TSC), and AC

Filters (ACF). From the viewpoint of power system operation, an SVC is equivalent to a

controllable reactor and a fixed capacitor. Its output can vary depending on the level of

generation and absorption of reactive power so as to maintain its terminal voltage at a

certain level.

In both the techniques described above, the volt/VAr control devices have operated

autonomously, independent of one another, and without centralized coordination. This

approach worked, but it left a good deal of efficiency on the table since actions were taken by one

device might have less-than-optimal results for another location on the grid or for the

system as a whole. Hence the modern and intelligent approach to Volt/Var control is needed to

optimize the grid performance, reduce losses and enhance consumer satisfaction. This can

be achieved through Volt/Var automation.

Volt/VAr Automation

Advances in automation and communications have laid the foundation to make centralized,

coordinated volt/VAr control possible and the emergence of Volt/VAr automation using

today’s faster computers leads to volt/VAr optimization. This is one of the functions of intelligent/smart grid.

volt/VAr Optimization

As it is known, is an advanced application that runs periodically or in response to operator

demand at the utility control center or in substation automation systems. Combined with

two-way communication infrastructure and remote control capability for capacitor banks

and voltage regulating transformers. The capacitor banks are equipped with sensors that

automatically trigger the need for reactive power compensation in case of any loss, by

sending signals to the grid or substation automation system. The real-time information

makes it possible to optimize the energy delivery efficiency on distribution systems.

The Role of Smart Grid

The “smart grid” is based on the usage of smart energy technologies—the application of

power control by means of digital information systems (smart meters and smart appliances)

that communicate through the advanced communication technology (i.e. internet) with the

electricity utility—to optimize electrical power system generation, delivery, and end-use

energy demands.

Smart Grid will integrate all the components of the power system to enhance the performance

of the grid. Much of the integration of components relates to communication systems, IT

systems, and business processes. And to achieve this, a Smart grid, real-time data, and active

grid management require fast and two-way digital communication.

Electric utilities use a wide variety of telecommunications including:

• Wired and wireless telephone

• Voice and data dispatch radio

• Fiber optics

• Power line carrier

• Satellite

• The internet

_ Fiber

_ Hybrid fiber cable (HFC)

_ Digital subscriber line (DSL)

_ Broadband over power lines (BPL)

_ Wireless (wi-fi and wi-max), and

_ SatelliteThe real breakthrough here is in the communication speed and quality of the computation

since the smart grid network uses advanced algorithms to identify the optimal operation

strategy from millions, or even billions of possibilities, arriving at a result fast enough to

apply it in real-time utility networks.

Smart grid plays a vital role in the utilities quest to deal with reactive power control in a

smarter, faster, and efficient manner. This result improved grid efficiency reduces the

amount of power that must be generated, hence dealt with the reactive power effect on

the grid, it also improves power factor and can result in substantial savings in the cost of energy

and infrastructure utilization and with it the emissions of CO2 and other pollutants

associated with power generation can be minimized significantly.

Discussions
Matt Chester's picture
Matt Chester on Jul 9, 2021

Smart grid plays a vital role in the utilities quest to deal with reactive power control in a

smarter, faster, and efficient manner.

For areas with established grids, is this better accomplished by upgrading/modernizing existing infrastructure, or is building from scratch in a way more effective? 

Shehu Ibrahim Khaleel's picture
Shehu Ibrahim Khaleel on Jul 10, 2021

Existing Grid infrastructure modernization and automation works. In most cases there no need to start from scratch,

JESSE NYOKABI's picture
JESSE NYOKABI on Aug 23, 2021

Improved grid efficiency indeed reduces the amount of power that must be generated, hence considering the reactive power effect on the grid, it also improves power factor and can result in substantial savings in the cost of energy and infrastructure utilization.

Smart grid has an important role to play with increase in renewable energy percentage on the grid. 

The Future is Now!

Shehu Ibrahim Khaleel's picture
Thank Shehu Ibrahim for the Post!
Energy Central contributors share their experience and insights for the benefit of other Members (like you). Please show them your appreciation by leaving a comment, 'liking' this post, or following this Member.
More posts from this member

Get Published - Build a Following

The Energy Central Power Industry Network is based on one core idea - power industry professionals helping each other and advancing the industry by sharing and learning from each other.

If you have an experience or insight to share or have learned something from a conference or seminar, your peers and colleagues on Energy Central want to hear about it. It's also easy to share a link to an article you've liked or an industry resource that you think would be helpful.

                 Learn more about posting on Energy Central »