#active filter

　フィルタは広い周波数成分を持った信号の中から必要な成分だけを取り出し、不要な成分を減衰させる電子回路です。これまでフィルタにはコイルとコンデンサを組み合わせたLCフィルタがおもに使われてきました。LCフィルタは受動回路ですから、働かせるための電源も不要ですし、周波数特性も充分すぐれたものを作ることができます。しかし、コイルはコアに線を巻いて作るために、特に低周波用のフィルタは形も大きくコスト高になります。

　コイルなしのフィルタはできないかという問題はずい分古くから取り上げられてきました。まず、LCのかわりにRCだけでフィルタを作る研究が盛んに行われましたが、するどい弁別特性をもたせようとすると、取り出したい信号成分も減衰が大きくなり、結局増幅器が必要になります。

　そこで、始めからRCと増幅素子を組み合わせてLCと同じ特性をもたせることが研究されるようになりました。これが本書で取り上げようとするアクティブフィルタです。

『アクティブフィルタの設計』　《電子科学シリーズ》

柳沢 健／金光 磐　（共著）　1973

(株)産報

To know the purpose of harmonic filtering, It improves to understand what harmonics are.

The energy of a standard 50Hz AC (Alternating Current) power supply beats between assertive and negative 50 times a second, following a clear sine-wave. Regular (linear) AC electrical loads such as heaters or bright lights bring a current that happens to this same sine-wave.

Every day, enterprises face the challenges of energy costs and efficiency optimisation.For ecological as well as economic reasons, industries need to implement an energy management system (EMS) according to the DIN 50001 standard, because only a comprehensive energy data acquisition system will provide the transparency needed to exploit all potential for optimisation.

Robust energy management that covers the full spectrum of buildings, production facilities and machines can help. Massive cost savings are possible but on one condition: complete, transparent acquisition and processing of all energy consumption data from the whole enterprise. This enables businesses to monitor consumption and detect sources of interference and energy wasters. Only then can you make informed energy management decisions to best drive down costs.

HOW ENERGY MEASUREMENT & ANALYSIS HELPS

It's really quite simple: you can't manage what you don't measure. Janitza's power quality analysers and energy supervision software provide transparency into how your assets are performing in real time so you can prioritise and manage initiatives that reduce energy consumption & emissions, ensure maximum uptime.

Janitza's energy management products can help utility managers and engineers to:

Gain better insight - with visibility of your energy usage patterns, from building to equipment level

Minimise energy costs - with timely alerts about energy 'waste'

Manage KPIs - measure & track performance against pre-determined benchmarks

Boost resource productivity - quickly identify inefficiencies and irregularities to avoid downtime

Improve decision making - prioritise investments based on real data, make smarter decisions

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JANITZA UMG 96-PA SERIES

The UMG 96-PA series is ideally suited for collecting and monitoring electrical measured values. Collecting data in this way enables not only energy management, but also power quality and residual current monitoring in a single device. Residual currents can be detected at an early stage and equipment damage and production downtimes avoided.

With the internal measured value memory, data are retained even if communication is interrupted. The UMG 96-PA-MID version also allows companies to record energy data relevant for billing.

All UMG 96-PA versions are delivered in the practical size of 96 x 96 mm. This facilitates easy integration of the devices in switch cabinets.

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FEATURES & FUNCTIONS OF UMG 96-PA

The modularly expandable energy measurement device,UMG 96-PA combines four functions in one device and can be modularly expanded by two analogue inputs – selectively as 0-20 mA analogue inputs (e.g. DC measurement) or as measuring inputs with detection of cable breaks and additional temperature measurement.

The main features of UMG 96-PA include:

Energy management system

· Continuous energy monitoring

· Identification of potential savings

· Reduction of energy costs

· Fulfilment of control & regulatory requirements

MID-compliant measurement

· Certified and tamper-proof MID measurement

· Legally secure accounting & energy acquisition

· Fulfilment of legal requirements

Power quality

· Secure, highly available power supply

· Avoidance of production stoppages

· Maximisation of operating times/preventative maintenance

· Prevention of product quality defects

· Detection of harmonics current up to the 40th order

Residual current monitoring (RCM)

· Continuous residual current monitoring

· Support for fire protection and personnel protection

· Effort reduction with the DGUV V3 tests

· Increased system availability

User-friendly & easy integration

· Easy installation due to front panel size, 96 x 96 mm

· Colour graphic display and intuitive user guidance

· Overvoltage category 600 V CAT III

· For use in TN and TT systems

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OTHER ENERGY MEASUREMENT DEVICES FROM JANITZA

UMG 96 S2: Entry level universal energy measurement device with Modbus interface.

The new UMG 96-S2 is a high precision multipurpose device suitable for measuring and controlling electrical variables, energy consumption as well as monitoring the power quality parameters, such as harmonics.

It is used in energy distribution systems, for example, to record cost centres and monitor thresholds. In addition, the device can also be used as a measurement value sensor for building management systems or a PLC.

UMG 96 RM-E: Multifunctional power analyser with RCM and Ethernet interface.

This power analyser with differential current measurement is unique in its class! Energy, universal and differential current measurement in one device.

UMG 96 RM P: Multifunctional power analyser with Profibus interface.

This measurement instrument is the newest generation device suitable for measuring, recording and monitoring electrical parameters (True-RMS) in low and medium voltage networks (1 and 3-phase systems with a neutral conductor).

UMG 96 RM PN: Multifunctional power analyser with Profinet interface.

Has 2 Ethernet interfaces that conform to PROFINET and integrated switch to set up line topologies. Includes an additional RS485 interface, and RCM to safeguard system availability.

UMG 96 RM EL: Multifunctional power analyser with Ethernet interface.

In order to record work values securely and precisely for individual consumers, the UMG measuring device has an extensive selection of tariffs of up to 14 items depending on the device type.

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JANITZA UMG 96-PA SERIES DISTRIBUTED IN INDIA BY MESSUNG

Messung Electrical Engineering is the authorised distributor for Janitza electronics GmbH, world leader in development and manufacture of energy management solutions. Janitza's cutting-edge digital energy meters, universal measurement devices, power quality analysers, peak demand management systems, etc. have placed them amongst the leading suppliers in this market.

With efficient energy management systems becoming de rigueur in industries, data centres, companies and infrastructure facilities, Messung partners to deliver Janitza’sbest-in-class measurement devices as per the latest IEEE 519-2014 and IEC 61000-4-30 standards.

GAIN CONTROL OVER ENERGY CONSUMPTION WITH JANITZA'S UMG 96-PA SERIES

Every day, enterprises face the challenges of energy costs and efficiency optimisation.

For ecological as well as economic reasons, industries need to implement an energy management system (EMS) according to the ISO 50001 standard.

Only a comprehensive energy data acquisition system will provide the transparency needed.

Robust energy management that covers the full spectrum of buildings, production facilities and machines can help.

Massive cost savings are possible only with complete, transparent acquisition and processing of all energy consumption data from the whole enterprise.

Active Harmonic Filter

Read this case study of the advantages and disadvantages of the active harmonic filter and how passive filter installation removes harmonics, voltage surges and improves PF. Besides, the active harmonic filter needs the support of a stable external power source for injecting phase opposite current harmonics to downstream loads. Its efficacy depends upon the stability of the connected external power source.

AHF design needs passive components like a capacitor and a resistor, but it can either do harmonic control or power factor correction to its 100% rating. In the case of both PF improvement and harmonic reduction, its capacity needs a derating to 50%. The active harmonic filter is a load in an electrical power system that generates anti harmonics at 180degree phase opposite. AHF has energy losses. Most OEM pdf catalogues declare the kWh losses at 3% under laboratory measurement.

Active Harmonic Filter does not eliminate downstream harmonic, electronic failure, equipment and relay tripping.

By design, it doesn't remove harmonics from downstream power line but by injecting anti-harmonic cancels it to prevent it from flowing into the upstream utility supply. Its application is to limit upstream grid harmonics within IEEE-519 norm. Whereas passive harmonic filter being a harmonic absorption type sucks up harmonics by short-circuiting it from the downstream load as well as upstream power system within its range. By doing so, it cleans up the circulating-harmonic from downstream loads which otherwise get absorbed in the downstream equipment and In turn, increase voltage harmonic distortion within the supply transformer. In a chain reaction, that otherwise would magnify the current harmonics extent of which depends upon the fault level of the load bus PCC. Thus, by design passive harmonic filter relieves all downstream loads by removing the circulating-harmonics that eliminate equipment failure, break-down and nuisance tripping on voltage fluctuation. It improves Protection Relay functioning - read it in another case study at Solar Power Inverter with Harmonic Filter.    

Active Harmonic Filter has energy losses. Series impedance causes VFD tripping. Why a drive-wise harmonic correction is not a good idea.

It requires real-power in kW for injecting phase-opposite harmonic current coming from the downstream non-linear load. That causes a minimum of 3% real energy losses in kWh term. Though OEM catalogue mention only about 3% energy loss, that's measured under an ideal condition. Energy-intensive industries employ hundreds of VFD drives within one transformer say 2000 KVA and operate in between 70 to 90% load factor. It requires higher impedance typically over 3% in series with VFD drive which injects further kW losses. Thus the 3% energy loss data may be valid for low-intensity load, but for higher load-factor and THDv, the total losses including in the high-value series impedance may go up to beyond 3%.

Some consultants prefer to have a drive-wise harmonic filter which is not a wise thing to do though in particular when the supply transformer has too many VFD drives. Active front end harmonic filters use high impedance upfront with its connected VFD drive.  Summarily, it magnifies power system impedance which in turn increases THDv, disturbs VFD operation making it susceptible to tripping for even a minor grid voltage fluctuation.

It has a known problem connecting with backup diesel generator (DG) if plant loads are high and need variable reactive power compensation. The active harmonic filter can't deliver that as it inherits only a fixed and limited design capacitor.  An extra Power Factor control panel is required.  A STATCOM to work in conjunction with it or the SATCOM to be inbuilt within it. Some AHF manufacturers use an additional external APFC capacitor bank or a detuned harmonic filter which they refer to as a hybrid harmonic filter. A detuned filter does not control harmonics. It uses a detuned reactor in series for the protection of capacitors and not for eliminating the load harmonics.    

Active Harmonic Filter - advantages

The active harmonic filter does not require to be custom built since it is mostly impedance independence except the designed capacitors and resistors.  It does not need any load specific frequency tuning.  Active harmonic filter manufacturers claim it can handle wideband harmonic frequencies. On the other hand, the passive harmonic filter needs extensive engineering efforts and are custom built with load specific design. However, it is also true that the actual-load never generates beyond a few harmonic frequency bands.  For example, computer, server and switch mode power supply (SMPS) loads produce 3rd and 9th harmonic currents to the extent of 75% and 15% respectively.  Six pulse drive loads produce 5th (60%), 7th (20%) and balance in 11th and 13th harmonic currents. 12-Pulse inverter loads generate 11th (50%), 13th (20%), 5th (20%) and balance in other frequency harmonic currents.

Active Harmonic Filter- disadvantages

Active Harmonic Filter has a known issue in handing high-intensity loads wherein THDv is above 10% and without a linear-load mix for which many OEM recommend not to use it. It also creates energy losses which vary from 3% for low-intensity loads and goes up to 7% for high-intensity loads and voltage distortions. Whereas passive filter being harmonic absorption type saves 3 to 5% real energy in kWh for moderately polluted harmonic loads.  When it comes to massively polluted harmonic load like in rolling mill drive with a fourth quadrant regeneration operation, induction furnace etc., it delivers an even higher percentage of energy saving. The same higher percentage energy saving is possible when the transformer or DG operates at a higher load factor typically in between 80 to 90% and with a very high THDv.

Active Harmonic Filter malfunctions when THDv is high and is used without a linear-load mix

It malfunctions while handling high-intensity power and harmonic pollution wherein the total voltage harmonic distortion (THDv) is above 10%. Many OEM recommends not to use it when THDv is more than 10%. While the higher THDv problem is universal, it has another issue when the load doesn’t mix with some linear-load like full speed induction motor and the current harmonic percentage is high. We have independently verified these features in the following two case studies which are detailed below.

2017 Global Active Filter Market: RS Pro, SolaHD and Wurth Elektronik

Global Active Filter Market Report illustrates the present development status of Active Filter along with the growth of Active Filter expected during the forecast period during 2017-2022. Active Filter Market analyses the industry based on different factors like growth trends, consumer volume, Active Filter market size and demand and supply status. Active Filter Market is a beneficial research…

Online tools for active filter design: Analog Device has tipical filter such as low pass, high pass and band pass filter. Attention: some circuits generated by defaut do not work!!! You must click the optimization button at the end of the design.

WEBBENCH designer has all type filter.

FilterLab® Filter Design Software ,www.microchip.com. It doesn’t works… From the introduction, it looks great. 😦 Th…