Author: cankat öner

How Do Power Quality Issues Affect Your Power Plant?

Power quality problems in your power plant can cause damage to physical objects and cause downtime. There are a wide range of issues which can contribute to financial losses and breakdowns.

• Sags: Transmission faults usually cause drops in voltage in the distribution network. Faulty installations or overloaded connections can also cause this problem.
• Breakdowns: Power interruptions for more than a few seconds can be a result of anything from short circuits, human error, downed power lines, and natural disasters.
• Power Surges: Voltage spikes due to heavy loads, static electricity, or even thunderstorms are very common.
• Fluctuating Voltage: Frequently starting and stopping electric motors can cause voltage fluctuations.
• Line Noise: Line noise can be a result of everything from improper grounding to radiation from electronic machines. Therefore isolating devices is extremely important.
• Harmonic Distortion: Current pulses which are non-sinusoidal can be caused by nonlinear loads

How to Manage Power Quality Issues

In order to manage the myriad power quality issues which can occur in your power plant, you should take certain basic measures.

Proactive Maintenance
Reacting to power breakdowns or equipment faults is the wrong approach. Instead, taking a proactive approach to prevent those problems is a much better alternative. Identifying problems early on like damaged equipment and faulty wiring and fixing them is a better approach. With this approach, you can count on fewer power disruptions and power quality issues.

Covering the Basics
There are 3 basic things you can do to manage power quality issues:

Energy Management
Instituting a power quality analyzer to manage energy in your power plant is energy management 101. It’ll not only help you optimize power distribution, but also reduce waste and allocate resources better.

Cataloguing Data and Extracting Insights
With the proliferation of IoT, it’s important to have devices which catalogue data from your power plant 24/7. With these, you can get data in real time that you can analyze and react to. Extracting insights from this data can allow you to reduce power quality issues.

Using Power Protection
Power protection is the third piece of the puzzle. Instituting standard power protection devices can protect your setup from power surges, line noise, etc. This can reduce downtime and save on repair bills.

Custom Solutions
Of course, it’s important to invest in custom solutions like power management algorithms and custom infrastructure. Every power plant is different.

With these steps covered, you can surely reduce power quality problems in your power plant.

Please contact us to learn more about how to tackle power quality issues in your renewable power plants!

Electric Power Quality and Dynamic Voltage Regulator

Electric power quality is a term which importance is increasing day by day. The increasing demand for electrical energy, the change in load characteristics, and the penetration of renewable energy sources such as solar and wind power generation facilities into the electricity grid have revealed the importance of the concept of electrical power quality. Electrical power quality can be defined as a set of electrical parameters and limits that enable end-user loads or equipment connected to the electrical grid to operate as desired without a significant loss of performance and operating-life. Electrical power quality problems can be defined as power problems caused by voltage, current, and frequency changes that cause failure or malfunction of end-user loads or equipment connected to the electrical grid.

The most common power quality problems encountered in electrical grids are voltage sag, voltage swell, overvoltage, under-voltage, and voltage unbalance. These power quality events cause the trip of loads, the failure of the equipment, and the interruption of the industrial process resulting in serious economic losses. Dynamic voltage regulator (DVR) provides the most effective solution for these voltage quality problems. DVR is a power electronics-based power quality compensation system that is connected in series with the grid. DVR provides effective protection by preventing the voltage quality events occurring in the grid from being seen on the load side with its high-performance voltage compensation ability.

Basic Working Principle

The main purpose of DVR is to provide voltage quality on the load side by detecting and compensating power quality events occurring in the grid voltage in less than a half-cycle period. The block diagram showing the basic working principle of DVR is given in Figure 1. DVR basically consists of a control system and a power circuit. The control system of DVR continuously monitors the grid voltage, detects the power quality events occurring in the voltage less than a half cycle period with the help of the control and detection methods, and generates the control signals required for the compensation. The power circuit of the DVR generates the compensation voltage and inject it into the grid in series to prevent voltage quality problems on the load side. Therefore, it ensures that the loads are protected from voltage quality problems occurring in the grid.

Figure 1 – DVR Working Principle

Power Stage Topology

The single line representation of the power stage of the DVR is given in Figure 2. The DVR power stage consists of active rectifier power and serial inverter power stages connected back to back over the DC capacitor bank.

Figure 2 – DVR power stage single line circuit diagram

An active rectifier is an IGBT based rectifier type controlled by PWM signals. It has much lower current harmonic distortion (THD:<3%) than conventional diode/thyristor rectifiers. The main function of the active rectifier is to provide the constant DC voltage required for the compensation according to the switching signals from the control system. The power stage of the active rectifier consists of the inverter, the DC link capacitor bank, and the output filter. According to the switching signals sent by the inverter control system, it controls the flow of the necessary active power from the grid to provide the required fixed DC link voltage. The output filter is used to filter the switching harmonics generated by the active rectifier inverter.

The series inverter power stage consists of the inverter, output filter, protection thyristor group, and injection transformer. The inverter generates the voltage required for compensation according to the switching signals generated by the control system. The output filter is used to filter the switching harmonics generated by the series inverter, as in the active rectifier filter. The protection thyristor group consists of thyristors connected anti-parallel to each other for each phase. The protection thyristor group is activated in case of an error in the grid or DVR, ensuring the disconnection of the series inverter power stage and protection of the system. The injection transformer, on the other hand, ensures that the compensation voltage produced by the inverter is injected in series to the grid and isolation between the grid and the DVR.

The DC-link capacitor bank is used to store the energy required for the DVR to meet the expected compensation requirements within the period until the active rectifier controller reacts at the moment of compensation.

In recent years, the increasing demand for electrical energy, the change in load characteristics, and the penetration of renewable energy sources such as solar and wind power generation facilities into the electricity grid have revealed the importance of the concept of power quality. 

The demand for electrical energy increases day by day, even though the rapid increase in demand for electrical energy, electricity generation, transmission, and distribution infrastructure cannot be upgraded or renewed at the same pace. This has led to an increase in the incidence of power quality problems in electrical networks. 

With the increasing use of renewable energy systems, the electricity generation infrastructure has become a distributed structure. When the variable generation characteristics of renewable energy generation systems such as solar and wind combined with the complexity of the distributed generation structure, the load flow in electricity networks become more unpredictable, this situation causes various power quality problems to occur in transmission and distribution networks. 

What are the main power quality problems encountered in electrical networks? 

Voltage trough and peak and harmonics are among the most common power quality problems encountered in electrical networks. In addition to these, low voltage, overvoltage, voltage fluctuation, which are (flicker) caused by variable reactive power flow and voltage and current unbalance events which are caused by unbalanced loading of the lines, are also frequently seen power quality problems. 

What happens when Power quality is poor? 

Electrical power quality problems lead to overheating and loss of life of cables and transformers, failure of capacitor banks, failure of protection equipment, failure of isolation equipment due to excessive stress, failure, or malfunction of devices connected to the network, and noise in communication lines. These impacts lead to severe economic losses for grid operators and all industrial, commercial, and residential customers.