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A.Rapoport of Powersines compares different voltage optimisation technologies and illustrates the advantages of the Comec INV (induced negative voltage) technology for achieving the best energy saving results in commercial facilities

Saving electricity by regulating and controlling voltage is not a novel idea. The basic principles stem from the fundamental laws of electricity, and the UK market has been implementing these ideas into reality for already a decade. A multitude of companies sell systems that enable voltage reduction from the relatively high voltage level on the UK grid, providing around 10% off electric costs. And, the fact that in the UK the nominal voltage level is excessive, around 240V compared with 230V harmonised voltage supply in Europe, increase further the opportunities for implementation of these technologies.

The real question that demands an answer is - how does one implement an efficient energy saving system that will be able to maximise electricity savings at different voltage levels and environments, without compromising on the performance of the electric equipment installed at the facility? 
This is the question we will address to answer in this article, by explaining the different technologies in use as well as providing a competitive analysis of energy efficiency systems available in the market today.

Fixed voltage reduction systems
Fixed voltage reduction systems are based on an autotransformer with several fixed output taps. An autotransformer is a type of transformer that has one winding, a portion of which is common to both the primary and the secondary circuits.  After analysing the voltage fluctuations at the facility, the installer wires the output tap for a fixed voltage reduction level.  The main disadvantage of these systems lies in the lack of control over the voltage output level.  For example, if the mains voltage decreases, then the output voltage will also be reduced at the same ratio and the system will supply a voltage that is too low to the facility.

A situation such as the example above may cause electric equipment performance malfunction.  In order to avoid such a situation, the installer would not be able to reduce the maximum possible voltage, but rather permit about 20%-30% of the voltage reduction level as ‘spare’.  As a result, this solution does not fully maximise the saving potential and actually could cause equipment failure. 

Tap-changing voltage controllers
The tap-changing voltage controller implements voltage control with a rather simple concept of back-to-back thyristors for tap-changing (see Diagram A). This technique has a reasonable response time (1 cycle) and is popular for small and medium power applications (> 20kVA).  The drawbacks include high control resolution, which requires a large number of thyristors (60 thyristors for +/- 3% regulation with +10/-20% input range). 
Even though autotransformers provide sinusoidal output voltage to the load, the thyristors based tap changing possess several disadvantages:  
• Complicated switching control (break before make).
• One shortened thyristor will completely block the control of the entire system.
• Multi-tap systems are not reliable and can’t provide flexible control of output voltage.

In addition, autotransformer based systems are costly to implement since their bulky size and heavy weight make it difficult to find a sufficient space for installation. Due to the typical copper losses in transformers, which range from 3%-5%, special care is also required for heat dissipation handling e.g. 50kVA autotransformer generates about 1,500W–2,500W of heat.

As related to the example above, the result is not suitable for installations in commercial indoor applications, such as retail or offices.

Electronic voltage controllers – phase controllers
Electronic voltage controllers – phase controllers – are devices that control RMS voltage by chopping part of each voltage cycle.  They are known as phase controllers and based on thyristors to control output voltage. These systems have high electric distortion, especially with non-linear loads, they require over-sized filters, and generate very poor input line harmonics, in addition they cannot handle surge currents such as motor starting. Taking into consideration power quality and reliability issues make these systems ineffective for most of commercial voltage control applications. They are mainly implemented in very small installations and sometimes for controlling the voltage on lighting circuits. However, increasing zero-crossing time intervals results in more lamp-flickering and negatively affects lighting systems.

Induced Negative Voltage (INV) Technology
PowerSines Induced Negative Voltage – INV - technology is based on the idea of controlling and transforming only a part of voltage that should be reduced from the input voltage level.

The system, based on this technology, is composed of several transformation cells. Each cell is a combination of current and voltage transformers that reduce a certain voltage level from the Mains (See Diagram B).

Unlike systems based on autotransformers, which have tap-changers that require ‘break-before-make’ changing taps processes creating momentary interruptions in power supply, the INV technology has a galvanic continuity and smooth commutation process guaranteeing power is continuously supplied to the load.  Transforming and regulating only ‘unnecessary’ voltage from the top of the line voltage results in high system efficiency and compact dimensions especially in comparison with any autotransformer-based systems. 

With the INV technology solution, voltage stabilisation is straightforward enabling the user to simply set the output voltage level required in the facility. In the case of input voltage reduction, with the INV technology the output voltage will automatically be corrected ensuring the facility will consistently receive the required voltage level without any risk of voltage levels dropping too low (See Chart 1).

The INV technology has proven itself as a very reliable and fully controllable solution for voltage stabilisation systems in commercial installations. It enables controlling the voltage supplied with steps of 1%. 

Conclusion
PowerSines invented the INV technology over a decade ago, and today it is implemented in all of PowerSines energy efficiency systems, successfully optimising the voltage in over 25,000 installations worldwide. PowerSines ComEC solution is a voltage optimisation system designed specifically for maximising savings in commercial facilities, by reducing the line voltage and stabilises it at the user defined set point, ComEC provides up to 18% energy savings on the total electric bill.

ComEC is an intelligent system that not only saves energy, but also measures and logs all electric network data parameters and saving figures. The ComEC integration with PowerSines Remote Energy Management System (Remote EMS) enables on-line access to real-time and historical data, for full monitoring and control of all ComEC systems for analysis, configuration, alarm set-up and more.