Clean Power for Office TowersApril 12, 2018 by Raghavan Venkatesh
This article features EPCOS AG product PQSine S series designed for 3-phase grids with or without neutral conductors and enables harmonics to be filtered.
The complex power networks of skyscrapers and other modern buildings must serve a wide range of nonlinear loads. Cutting-edge active power conditioning solutions based on the EPCOS PQSine S series of active harmonic filters help skyscrapers and large commercial buildings eliminate potential power quality issues.
The many power electronics systems in use in large commercial buildings such as skyscrapers include nonlinear loads such as variable speed drives, UPS systems, computers and servers, lighting, TV sets, and more. A major challenge facing building operators is the harmonics pollution in their power networks, leading to a marked deterioration in the quality of the supply voltage.
TDK field applications engineers are joining forces with specialized power quality distribution partners to create cutting-edge power conditioning solutions for such buildings based on the PQSine S series of active harmonic filters.
The Danger of Harmonic Pollution
The nonlinear current draw results in harmonics that cause distortion in the sinusoidal voltage, which in turn can cause interference for other loads. Harmonics are integer multiples of the basic frequency, i.e. of the line frequency of 50 Hz or 60 Hz. The harmonics have varying amplitudes and can extend into the upper kHz range. Harmonic pollution has a series of negative effects on power quality, including:
- malfunctions of other loads due to poor grid power quality;
- additional current load on the neutral conductor, as the harmonic currents of the 3rd, 9th, 15th, and 21st orders, and more. are accumulative and lead to inadmissibly high currents;
- phase asymmetry (specifically when operating single-phase switch-mode power supplies) which additionally promotes the generation of harmonics.
In addition, harmonics can severely impair the function of sensitive devices or even destroy them. IT networks with their servers and PCs are a typical example, where the malfunction of network devices can lead to corrupted data and enormous consequential damage.
Towering Power Quality Challenge
Due to the sheer size of skyscrapers and the complexity of its various electrical loads and systems, power quality, therefore, plays a central role in ensuring the lowest possible energy consumption and costs, as well as avoiding overheating, production/process downtimes, and malfunction of equipment.
The major electrical loads and their characteristics are:
The required reactive power compensation for up to more than 100 elevators is very dynamic, and changes very fast between capacitive and inductive during operation and when they feed recuperative power back into the network. The THD-I is also very high and changes rapidly. The main contributors to THD are in the 5th, 7th, 11th, and 13th orders.
- Indoor and outdoor lighting
All lights are LED and CFL (compact fluorescent lamp), which are used to save energy, generate significant harmonic distortion in the range from 150 Hz up to 2500 Hz. Large-screen LED digital billboards (with up to more than 2000m² dot-matrix lighting); the main harmonic current is of the 3rd order, but harmonic distortion is also present up to the 50th order.
The inverters employed are a source of harmonic distortion and require reactive power compensation. They produce dominant harmonics typically in the 5th, 7th, 11th, and 13th order, but also in the 17th and19th order and above.
- Fans, water pumps, cooling machines, and fire protection
The many smaller 6-pulse power converters in the system contribute current harmonics in the 5th and 7th order and above.
- IT networks, UPS, security systems, and access control systems The many SMPS in the servers, clients and other network devices generate harmonics from the 3rd to 23rd order and above. Moreover, they require a reliable and secure power supply without interruptions.
Complete Power Conditioning Solution
The extremely complex load profile of skyscrapers requires both dynamic reactive power compensation and the mitigation of harmonics over a broad frequency spectrum. An ideal solution for such large commercial towers is a complete power conditioning solution based on the PQSine S series of active harmonic filters. The first step is a detailed analysis of the building’s power network. In this case, TDK field application engineers work together with specialized power quality distribution partners. For new skyscrapers, this will take place during the building’s construction phase. Such analyses generally reveal significantly elevated THD levels and transient harmonics in all feeders of a building’s network (Figure 1). In a typical
Figure 1: Typical performance analysis of a power supply system, showing the presence of significant harmonic distortion in all harmonics, especially in the 3rd, 5th, 7th, 11th, and 13th orders.
office tower distortion is especially high in the 3rd, 5th, 7th, 11th, and 13th harmonics. Based on the analysis and the requirements for power quality, energy savings, reliability, the advanced PQSine S series of active harmonic filters and power optimizers represents an ideal solution (Figure 2). The PQSine S series extends the comprehensive portfolio of EPCOS components and systems for power quality solutions covering solutions such as active and passive harmonic filters, detuned capacitor banks, and low and medium voltage automatic power factor correction systems.
Figure 2: EPCOS PQSine S series of active harmonic filters can be installed in-floor cabinets (left) or wall-mounted cabinets (right)
PQSine S Series for High Performance and Reliability
The PQSine S series is designed for 3-phase grids with or without neutral conductors and enables harmonics of up to the 50th order (2500Hz/3000Hz) to be detected and filtered. In addition to outstanding filtering capabilities, PQSine active harmonic filters also ensure balancing of the loads to all three phases. Moreover, neutral conductor currents are also compensated when using 4-wire devices. These features avoid line resonance and ensure high performance and reliability.
Figure 3: Functional principle of EPCOS PQSine. PQSine ensures a sinusoidal current draw. Harmonics and phase shifts are effectively reduced.
The optimized active harmonic filtering solution with PQSine has the following key features:
- Harmonic and reactive power compensation dual function. The PQSine S series of active filters effectively compensate system harmonics, while at the same time providing fast reactive power compensation for both capacitive and inductive loads, which can keep the system power factor at very nearly 1.0.
- Intelligent switching design special bus system, to ensure that any two of the three ACB cabinets (two incoming and one bus coupler) are always switched in for performance and redundancy purposes.
- Ultrafast reaction speedThe PQSine S series of active filters feature a reaction time of under 50 μs and can thus respond quickly to the high and rapidly changing loads;
- Modularity and scalability In order to allow for future system expansion to meet changing power conditioning requirements, each installed PQSine cabinet has two or three empty slots.
Optimum reliability is ensured by means of a series of self-monitoring systems. The most important of these are overload protection, shutdown on overtemperature, protection against overvoltage or undervoltage and fan monitoring. The PQSine S series includes a 7-inch TFT color touch-screen for user-friendly input and reading of the data. PQSine offers a number of Modbus (RTU) and TCP/IP (Ethernet) interfaces for control, programming, and diagnostics purposes.
The PQSine S series of active harmonic filters are based on the latest state of the art in power electronics technology. They are installed in parallel to the polluting loads. The active filter analyzes the line current and its associated harmonics and generates a compensation current which neutralizes the harmonic currents and creates an almost sinusoidal waveform (Figure 3). With its fast reaction time, PQSine offers excellent performance for fast-changing loads, such as those generated by elevators. Using the data determined in real-time, PQSine feeds a compensation current into the grid, which cancels the nonlinearity of the load current.
Optimized design for demanding harmonics order to optimally compensate harmonic currents from the electrical loads in a recent installation, a total of 76 PQSine S series units were installed for the various feeders on eleven levels of the skyscraper. Figure 4 shows a typical single line diagram of an electrical distribution board.
Figure 4: Typical single line diagram of an electrical distribution board.
Reliable Harmonic Current Compensation for a Wide Range of Applications
After the installation of the complete power conditioning solution, the TDK field application engineers and their partners typically perform a comprehensive power quality analysis with a specific focus on harmonics as proof of the installation’s effectiveness. According to the power quality data gathered on-site at a recent installation, the PQSine S series limits the system THD-I to below 3 percent. The system current was about 160 ARMS during the specific measurement. Overall, the PQSine solution successfully delivered the highest level of power quality. The current phases were sinusoidal with a very low level of THD-I (Figure 5), and the power factor was nearly 1.0.
Figure 5: With the PQSine active harmonic filter and power optimizer, the current phases were sinusoidal with a very low level of THD-I and the power factor was nearly 1.0.
PQSine has proven very effective in mitigating harmonics and also providing dynamic reactive power compensation to ensure the optimal power quality for all loads and users of large commercial buildings. PQSine active harmonic filters and power optimizers are especially suitable for fast current harmonics, reactive power compensation or neutral current compensation in a wide range of power networks in
- Data centers and IT-enabled service facilities,
- Renewable energy power generation,
- Process industries,
- Sensitive manufacturing facilities, and
- Office buildings, shopping centers, hospitals.
About the Author
Venkatesh Raghavan holds a Ph.D. and a Master's Degree in High Voltage Engineering at the Indian Institute of Science and at the Anna University respectively. He also holds a Bachelor's Degree in Electrical and Electronics Engineering. He is currently the President of EPCOS since February 2008.
This article originally appeared in the Bodo’s Power Systems magazine.