Role Of Active Harmonic Filters In Mitigating UPS System Harmonics

Introduction

The role of constant power supply across industries is undisputed. From facing downtime to critical operational errors, there are a lot of reasons behind the requirement for constant, consistent power. A great way to ensure this is through a UPS device, where UPS stands for Uninterrupted Power Supply. While it serves its purpose, it brings with its own set of issues in the form of harmonic distortion. Harmonics can ruin the quality of power and bring down operational efficiency in different ways. This is why actively identifying and filtering harmonics in these UPS systems is paramount.

1. Understanding Harmonics in UPS Systems

What are harmonics and how do they originate in UPS setups?

UPS setups exhibit non-linear loads in nature, that is, the increase or decrease of voltage and current is not proportional to each other. So, instead of drawing current in a sinusoidal waveform, it draws in current in pulses. This leads to the formation of harmonic distortions or frequencies of the current waveform, creating their own set of problems. The most common cause of UPS harmonics is the rectifier or inverter parts of the circuit.

Impact of nonlinear loads on power quality

There are many adverse effects of nonlinear loads on power quality, the biggest one being the introduction of harmonics. Harmonic distortions increase the overall THDi of the system and bring down the overall quality, sometimes below acceptable limits, requiring power quality correction.

Other consequences include the overheating of sensitive equipment, mainly due to harmonics, and voltage fluctuations. The latter can take on the form of voltage surges/swells and sags, which can also adversely affect equipment connected to the power supply. Apart from significant damage to equipment, nonlinear loads can also reduce the overall energy efficiency of the system, requiring more power to function properly and increasing overall energy consumption.

Common symptoms: overheating, reduced UPS efficiency, waveform distortion

What are some common symptoms of the presence of excessive harmonic distortion in a UPS circuit? These include:

- Overheating: The presence of harmonics in a UPS system will increase heating in equipment such as transformers or motors. Therefore, overheating is an excellent indication of harmonics.

- Reduced UPS Efficiency: Due to harmonics in the system, more current is drawn in than necessary to keep the UPS operational. This can bring down the overall efficiency of the device.
- Waveform Distortion: Lastly, if one has proper devices to measure waveform, clear waveform distortions in current or voltage can indicate the presence of harmonics in the circuit.

2. Why Passive Filters Fall Short in UPS Applications

Limited frequency bandwidth

Passive harmonic filters were considered one of the best ways to tackle harmonics in a system. However, they fall short when it comes to handling harmonics in UPS systems mainly due to their limited frequency bandwidth. Passive harmonic filters are best suited in cases where the frequency of the harmonics is known and constant. Then it can tackle this set frequency expertly. However, since the harmonic frequency keeps changing in the case of UPS systems, passive harmonic filters are a bad match.

Ineffectiveness under dynamic load conditions

UPS also creates dynamic load conditions as it is connected to equipment that start and stop, such as motors. Passive harmonic filters are better suited in cases where the load is static in nature. It is ill-equipped to handle constantly fluctuating current and voltage conditions.

Compatibility and space constraints in modern facilities

Lastly, modern facilities operate on the principle of efficiency. This goes to the overall space in the facility as well. Not only are passive harmonic filters limited in handling harmonics, but also occupies a lot of space. This makes it challenging to install this harmonic filter with UPS applications.

3. How Active Harmonic Filters Solve the Problem

Active harmonic filters surpass the problems and limitations of passive harmonic filters, making them a better fit for UPS applications. Here’s how:

Real-time dynamic compensation

Unlike passive harmonic filters that can only handle static harmonics, active harmonic filters are built for dynamic compensation. This means that as the intensity and frequency of the incoming harmonics changes, active harmonic filters respond to it in real-time. This is made possible by the overall design of the harmonic filter. An active harmonic filter reads the incoming harmonics in microseconds and sends a pulse that is exactly the same in magnitude, but opposite in phase, thereby neutralizing its effects. Therefore, these harmonic filters offer dynamic compensation in real-time.

Maintaining stable current waveform at all load conditions

As mentioned above, when the load conditions change, it leads to fluctuation of the current waveform, which can be identified with appropriate equipment. Active harmonic filters address this by ensuring that the current waveform is stable at all load conditions. This means that the waveform after the introduction of active harmonic filters is as close to the ideal sinusoidal waveform as possible, thereby counteracting the negative side effects of harmonic distortion.

How does the harmonic filter achieve this? The control system of the active harmonic filter first identifies the load current and its underlying harmonic components. Then, it generates compensating currents that are equal in magnitude to the incoming current, and opposite in phase to the harmonics.

Compatibility with variable-frequency drives, UPS systems, and generators

The above-mentioned features make active harmonic filters compatible with a wide variety of non-linear equipment such as variable frequency drives, UPS systems and generators. In the case of all these equipment, there is a tendency to draw in current in pulses, thereby distorting the current waveform and generating massive harmonics. However, with an active harmonic filter to cancel out the ill effects, they instead work in tandem with UPS systems to ensure a clean and stable power for high level commercial applications.

4. Applications of Active Harmonic Filters in UPS-Environments

As active harmonic filters are compatible with UPS devices, where are they generally applied? Their general applications include:

Data centers and server rooms

Data centers and server rooms are facilities that store a large amount of data in a concentrated space. To store and use this digital data effectively, it is important to ensure a constant supply of quality power. UPS systems are used to ensure that the devices always have power irrespective of fluctuations of the grid, and active harmonic filters ensure that any harmonics generated by the UPS devices are handled in real-time.

Medical and lab equipment backup

In hospitals and medical settings, where patient safety and health is paramount, it is important to have constant power supply to operate sensitive equipment that directly or indirectly impacts a patient’s well-being. UPS and active harmonic filters work here in tandem to keep a steady stream of high-quality power. The same holds true for lab equipment as well, as any fluctuations in power can compromise the quality and result produced by said equipment.

Industrial automation with UPS fallback systems

Industrial automation also relies on UPS systems to ensure that the processes are not interrupted by power outages or voltage fluctuations. Here, active harmonic filters help maintain the longevity of sensitive equipment, while tackling any incoming harmonics in the system.

Precision manufacturing environments

Precision manufacturing refers to conditions where parts are produced with very tight tolerances. Examples include manufacturing medical equipment or the aerospace industry. Any interruption in power or drop in quality can adversely impact the precision of the end product. Therefore, UPS and active harmonic filters are required to ensure the utmost quality.

5. Key Benefits of Using AHF in UPS Systems

Reduces total harmonic distortion (THD) to acceptable levels

While not completely eliminating harmonic distortion, active harmonic filters help reduce the total harmonic distortion (THD) within the UPS system within acceptable levels. As per international compliances, the THDi levels of the system should be below 5 percent to be considered acceptable, and REVCON Active Harmonic Filter achieves this by dynamically adapting to load changes. This makes them an ideal fit for UPS power systems, where clean, interrupted power is paramount.

Enhances UPS battery life and runtime

The harmonic distortion caused by non-linear loads such as UPS can cause damage to the equipment, mainly in the form of lowering battery life and runtime. With the use of active harmonic filters, however, one can achieve quality UPS system protection. Moreover, the lifespan of the UPS system is actually enhanced, majorly in the form of increased battery life and runtime.

Minimizes voltage sags, system derating

Voltage swells and sags are one of the major non-linear load issues. Active harmonic filters help minimize these phenomena by addressing harmonics in real time. This ensures that the overall voltage or current waveform is constant and therefore, ensures a clean, stable power supply. Similarly, it also reduces instances of derating, which is a condition where an equipment is operated well below its rated capacity to prevent failure or overloading, but reducing efficiency.

Prevents overheating and damage to sensitive loads

Sensitive equipment always runs the risk of damage due to power and voltage fluctuations. While UPS systems are installed to ensure a steady stream of power, the harmonics caused by UPS can still damage these equipment due to overheating. Active harmonic filters address these harmonics in a timely manner and prevent overheating, thereby protecting sensitive equipment from damage.

Compliance with IEEE 519 and power utility norms

Lastly, facilities must adhere to power compliance standards such as IEEE 519. Otherwise, they are subjected to penalties. Therefore, active harmonic filters play a very important role of ensuring that the UPS and overall system adheres to these standards and respective power utility norms.

6. Installation Considerations and Best Practices

Placement: upstream or downstream of UPS

The first criteria to consider with respect to active harmonic filter installation is its location. Should it be placed upstream or downstream of the UPS device? This will depend on the overall setup and the application of the UPS system.

Sizing according to harmonic load profile

The next step is identifying the harmonic load profile for the system, as it will determine the size and specifications of the active harmonic filter. For this, it is vital to measure metrics such as Total Harmonic Distortion (THDi/THD), and power factor (PF). Based on the numbers, the type of AHF can be selected. Moreover, the harmonic filter should also be scalable as the scale of the operation increases or decreases. This will ensure optimal harmonic mitigation at all times.

Monitoring tools for real-time diagnostics

Lastly, the performance of the AHF in real-time will determine the success of the installation. This can be done in two ways. First, during installation, one should run comprehensive system tests under dynamic load to see if the active harmonic filter is functioning properly. Then, post-installation, the performance of the filter should be checked with diagnostic tools to see if THD and PF have a positive change. This will help make small adjustments in the AHF depending on the diagnostics.

Conclusion

In summary, active harmonic filters are highly compatible with UPS systems to ensure interrupted, clean power across various industrial sectors. The positive return on investment is undisputed as it not only prevents damage of sensitive equipment, but it also boosts energy efficiency and increases the overall power factor of the system. To learn more about REVCON AHF solutions and how it can transform the performance of your UPS system, contact us at ADM Engineering Inc. today!

FAQs

1. Why do UPS systems generate harmonics?

UPS machines provide a non-linear load to the system, leading to the formation of non-sinusoidal waveforms, which in turn generates harmonics.

2. Can active filters improve battery performance in UPS?

Yes, it can improve battery performance in UPS systems by eliminating harmonics and improving energy efficiency.

3. What’s the difference between passive and active filters in UPS?

Passive filters are capable of tackling a specific harmonic frequency, that is a static load. Active harmonic filters, on the other hand, can handle a wide range of harmonics, making them ideal for dynamic load applications such as a UPS system.

4. Is IEEE 519 compliance mandatory for UPS systems?

Yes, IEEE 519 is mandatory for any commercial electrical system and setup, including UPS systems. Failure to comply can incur penalties from relevant bodies.

5. How to monitor harmonic levels in a UPS setup?

A power quality analyzer can be used to monitor harmonic levels in a UPS setup. Use it to measure THDi and compare it with acceptable standards stated in IEEE 519 and other metrics.