GRIDCONTM Series of Active Filters
The GRIDCONTM series of active filters is the number one choice for challenging harmonic and PQ compensation tasks where performance, reliability and safety are critical, even beyond normal operating voltage levels and under challenging environmental ambient conditions:
- Operation up to 690 V and higher voltage levels at full power without derating
- Rated current can be extended in a modular manner from 125A to 2500A
- Harmonic compensation to 9kHz with optional module (up 51st as standard)
- Isolates susceptible and sensitive downstream equipment from MV and LV background voltage
- Advanced 3-level architecture, high power density and compact design
- Low operating losses
- Extremely durable, long life film DC bus capacitors
- Overvoltage category III up to 1000 V
- Degree of protection up to IP20, IP21 and IP54 possible with optional external water cooling for complete encapsulation
- Dynamic compensation of reactive power, harmonics, and flicker, as well as load balancing in one unit
- GridconTM can provide harmonic compensation for both MV and LV applications
Internal view of 375A GRIDCON™ active filter, special colour
Simplified block diagram of active harmonic filter in operation
Intuitive touchscreen display of GRIDCON™ active filter
The central control and display element of the GRIDCONTM series is via the door mounted touch panel and/or a LAN. It has a clear menu structure and can display data in both tables and diagrams. The benefits of the touch panel include:
- Simple parameterization of the filter function without additional measuring devices. Though a more complex power quality analyser can be provided based on client requirement.
- Explanations and status messages in plain text in a number of languages
- Intuitive operation and password protection
GRIDCONTM can also be operated via the internet. Once incorporated into a company network or connected via a mobile phone network, it can be monitored or parameterized remotely using a browser.
Advanced 3-Level technology
The 3-level design of GRIDCONTM is based on twelve IGBTs. Conventional two-level active filters only comprise of six IGBTs. The three-level configuration reduces the voltage stressing on the power semiconductors by 50%, resulting in lower losses and permits the GRIDCONTM to be utilised in systems with a higher rated voltage. The DC link voltage is also higher which permits higher peak currents to be generated, lowering losses, essential for filtering harmonics with a high bandwidth.
Schematic showing the advanced 3-level architecture of GRIDCON™ filters
Another benefit of the 3-level technology is the lower ripple of the output current compared with the 2-level architecture. The split DC link and the larger number of IGBTs results in an additional third inverter state at the output. This is to reduce the size of the carrier frequency and EMC filters. The difference between 2-level and advanced 3 level-architecture is shown below:
A comparison of 2-level IGBT based active filter with advanced 3-level IGBT based GRIDCON™
In all industries worldwide, many types of variable speed drives, rectifiers and other non-linear loads are utilised. The benefits of variable speed drives are widely acknowledged. However, all types of variable speed drives, for example, require some form of harmonic mitigation. The application of GridconTM active filters reduce voltage distortion significantly over a wide range of harmonic frequencies.
Harmonic mitigation performance
GRIDCON™ mitigation of a 6 pulse PWM VFD using one phase waveform illustration
GRIDCON™ mitigates harmonics up to 51st order (and to 9kHz (180th order) with optional module)
GRIDCONTM can be connected to either LV or MV supplies to provide harmonic mitigation and other PQ compensation, as shown below (10kV system). However, GRIDCONTM can also, via its voltage control feature, attenuate pre-existing or ‘background voltage distortion’ and effectively isolate and protect LV loads from THDu emanating from MV supplies.
GRIDCON™ providing mitigation at MV
Example of MV grid current with/without GRIDCOM™
GRIDCONTM has three modes of control :
- Open loop (load sensing with the CTs on the side)
- Closed loop (source sensing with the CTs upstream of the filter connection)
- Voltage control (where CTs are not required since special control is activated)
Active filters, capable of voltage control, directly target the voltage instead of injecting a compensation current based in the CT signals. Hence voltage control enables “sensorless control” without CTs, often with better results.
For background voltage distortion mitigation, (i.e. the localised reduction of harmonic levels fed by medium voltage (MV) networks or transformers with high levels of THDu), GRIDCONTM voltage control is a mandatory requirement. In addition, the voltage limiter function inbuilt within GRIDCONTM enables autonomous output adaption for automatic harmonic standard compliance. Note, with GRIDCONTM, the voltage control modes are selectable per frequency for optimised performance.
The THDu trend illustrates above the superior performance of GRIDCON™ voltage control and its ability to attenuate background THDu (aka pre-existing voltage distortion).
Mitigation of Supraharmonics to 9kHz
Almost all active filters compensate for harmonics to the 50th order only. GRIDCONTM, in conjunction with a specifically designed internal, high-pass, SHU module, can treat supraharmonics up to 9kHz (150th order at 60Hz fundamental or 180th order at 50Hz) as illustrated below.
Standard GRIDCON™ (to 50th order). GRIDCON™ plus SHU (to 9kHz – 150th order)
This combination of GRIDCONTM and SHU passive can compensate for AC, DC drive and active filter switching high frequency voltage harmonics, SCR line notching and LED lighting, for example up to 9kHz as illustrated below (DC drive).
DC SCR 6 pulse drive in a copper factory. THDu averaged 13.58% and included high frequency harmonics to the 97th order.
Reduction in low and high frequency harmonic voltages on a 6 pulse SCR DC drilling package due to a combination of GRIDCONTM and SHU. THDu of 13.58% to 97th order (5.82kHz on 60Hz) due to line notching. THDu reduced to 4.23%.
Example of 375A GRIDCON™ with optional high-pass SHU module compensates harmonics up to 9kHz (150th order for 50Hz and 180th for 60Hz)
MOSAF general specification
Enclosure dimensions
Sentinel Power Quality Group has the knowledge and experience
GRIDCONTM is available in compensation ratings from 125A to 2500A per connection in enclosures to IP20, IP21 and IP54. Water cooling is also an option. GRIDCONTM applications covers all aspects of offshore PQ including supraharmonics to 9kHz and the treatment of background harmonic voltage distortion including MV and LV applications.
When applied correctly, active filters are an important tool in the harmonic mitigation toolbox. However, no form of harmonic mitigation is perfect. The secret of success is recognising the pros and cons of all types of active and passive mitigation and being able to apply the most appropriate form of mitigation for any given application. The staff at Sentinel Power Quality Group and its divisions have been involved in applying active and passive filters since 2003 to a large number of demanding applications and industries.
If a visit to your site is required to carry out detailed measurements or PQ troubleshooting, we have fully trained PQ engineers available. To view our section on PQ Services please click here.
Contact us with your application details and let us assist you.