ENERGY EFFICIENT LIGHTING CONTROLS

Occupancy Sensors

                     Occupancy-linked control can be achieved using infra-red, acoustic, ultrasonic or microwave sensors, which detect either movement or noise in room spaces. These sensors switch lighting on when occupancy is detected, and off again after a set time period, when no occupancy movement detected. They are designed to override manual switches and to prevent a situation where lighting is left on in unoccupied spaces. With this type of system it is important to incorporate a built-in time delay, since occupants often remain still or quiet for short periods and do not appreciate being plunged into darkness if not constantly moving around.

Timed Based Control

                  Timed-turnoff switches are the least expensive type of automatic lighting control. In some cases, their low cost and ease of installation makes it desirable to use them where more efficient controls would be too expensive.

Types and Features

                       The oldest and most common type of timed-turnoff switch is the “dial timer,” a spring-wound mechanical timer that is set by twisting the knob to the desired time. Typical units of this type are vulnerable to damage because the shaft is weak and the knob is not securely attached to the shaft. Some spring-wound units make an annoying ticking sound as they operate. Newer types of timed-turnoff switches are completely electronic and silent. Electronic switches can be made much more rugged than the spring-wound dial timer. These units typically have a spring-loaded toggle switch that turns on the circuit for a preset time interval. Some electronic models provide a choice of time intervals, which you select by adjusting a knob located behind the faceplate. Most models allow occupants to turn off the lights manually. Some models allow occupants to keep the lights on, overriding the timer. Timed-turnoff switches are available with a wide range of time spans. The choice of time span is a compromise. Shorter time spans waste less energy but increase the probability that the lights will turn off while someone is in the space. Dial timers allow the occupant to set the time span, but this is not likely to be done with a view toward optimising efficiency. For most applications, the best choice is an electronic unit that allows the engineering staff to set a fixed time interval behind the cover plate.

Daylight Linked Control

                              Photoelectric cells can be used either simply to switch lighting on and off, or for dimming. They may be mounted either externally or internally. It is however important to incorporate time delays into the control system to avoid repeated rapid switching caused, for example, by fast moving clouds. By using an internally mounted photoelectric dimming control system, it is possible to ensure that the sum of daylight and electric lighting always reaches the design level by sensing the total light in the controlled area and adjusting the output of the electric lighting accordingly. If daylight alone is able to meet the design requirements, then the electric lighting can be turned off. The energy saving potential of dimming control is greater than a simple photoelectric switching system. Dimming control is also more likely to be acceptable to room occupants.

Localized Switching

                           Localized switching should be used in applications which contain large spaces. Local switches give individual occupants control over their visual environment and also facilitate energy savings. By using localized switching it is possible to turn off artificial lighting in specific areas, while still operating it in other areas where it is required, a situation which is impossible if the lighting for an entire space is controlled from a single switch. 

ENERGY EFFICIENT MOTORS

Minimizing Watts Loss in Motors

Improvements in motor efficiency can be achieved without compromising motor performance - at higher cost - within the limits of existing design and manufacturing technology. From the Table 10.1, it can be seen that any improvement in motor efficiency must result from reducing the Watts losses. In terms of the existing state of electric motor technology, a reduction in watts losses can be achieved in various ways.

All of these changes to reduce motor losses are possible with existing motor design and manufacturing technology. They would, however, require additional materials and/or the use of higher quality materials and improved manufacturing processes resulting in increased motor cost.

Simply Stated: REDUCED LOSSES = IMPROVED EFFICIENCY

 

                         Thus energy-efficient electric motors reduce energy losses through improved design, better materials, and improved manufacturing techniques. Replacing a motor may be justifiable solely on the electricity cost savings derived from an energy-efficient replacement. This is true if the motor runs continuously, power rates are high, the motor is oversized for the application, or its nominal efficiency has been reduced by damage or previous rewinds. Efficiency comparison for standard and high efficiency motors is shown in Figure 10.4

Technical aspects of Energy Efficient Motors

                              Energy-efficient motors last longer, and may require less maintenance. At lower temperatures, bearing grease lasts longer; required time between re-greasing increases. Lower temperatures translate to long lasting insulation. Generally, motor life doubles for each 10°C reduction in operating temperature.

Select energy-efficient motors with a 1.15 service factor, and design for operation at 85% of the rated motor load.

                       Electrical power problems, especially poor incoming power quality can affect the operation of energy-efficient motors.

                        Speed control is crucial in some applications. In polyphase induction motors, slip is a measure of motor winding losses. The lower the slip, the higher the efficiency. Less slippage in energy efficient motors results in speeds about 1% faster than in standard counterparts.

                         Starting torque for efficient motors may be lower than for standard motors. Facility managers should be careful when applying efficient motors to high torque applications.

VARIABLE FREQUENCY DRIVE

Speed Control of Induction Motor

                     Induction motor is the workhorse of the industry. It is cheap rugged and provides high power to weight ratio. On account of high cost-implications and limitations of D.C. System, induction motors are preferred for variable speed application, the speed of which can be varied by changing the supply frequency. The speed can also be varied through a number of other means, including, varying the input voltage, varying the resistance of the rotor circuit, using multi speed windings, using Scherbius or Kramer drives, using mechanical means such as gears and pulleys and eddy-current or fluid coupling, or by using rotary or static voltage and frequency converters.

Variable Frequency Drive

                       The VFD operates on a simple principle. The rotational speed of an AC induction motor depends on the number of poles in that stator and the frequency of the applied AC power. Although the number of poles in an induction motor cannot be altered easily, variable speed can be achieved through a variation in frequency. The VFD rectifies standard 50 cycle AC line power to DC, then synthesizes the DC to a variable frequency AC output. Motors connected to VFD provide variable speed mechanical output with high efficiency.These devices are capable of up to a 9:1 speed reduction ratio (11 percent of full speed), and a 3:1 speed increase (300 percent of full speed). In recent years, the technology of AC variable frequency drives (VFD) has evolved into highly sophisticated digital microprocessor control, along with high switching frequency IGBTs (Insulated Gate Bi Polar Transistors) power devices. This has led to significantly advanced capabilities from the ease of programmability to expanded diagnostics. The two most significant benefits from the evolution in technology have been that of cost and reliability, in addition to the significant reduction in physical size.

Variable Torque Vs. Constant Torque

                             Variable speed drives, and the loads that are applied to, can generally be divided into two groups: constant torque and variable torque. The energy savings potential of variable torque applications is much greater than that of constant torque applications. Constant torque loads include vibrating conveyors, punch presses, rock crushers, machine tools, and other applications where the drive follows a constant V/Hz ratio. Variable torque loads include centrifugal pumps and fans, which make up the majority of HVAC applications.

Why Variable Torque Loads Offer Greatest Energy Savings

                                 Invariable torque applications, the torque required varies with the square of the speed, and the horsepower required varies with the cube of the speed, resulting in a large reduction of horsepower for even a small reduction in speed. The motor will consume only 12.5% as much energy at 50% speed than it will at 100% speed. This is referred to as the Affinity Laws, which define the relationships between speed, flow, torque, and horsepower. The following law illustrates these relationships:

􀂙 Flow is proportional to speed

􀂙 Head is proportional to (speed) 2

􀂙 Torque is proportional to (speed)

􀂙 Power is proportional to (speed) ³

Additional benefits which are readily seen include: the reduction and/or elimination of motor starters, less stress on the AC motor windings and bearings, and a decrease in stress and wear on the pump or fan itself. This all equates to a smoother, longer lasting and more efficient operation process.   When looking to apply VFD control to an existing pump, a basic overview of the application should be investigated. If the original design philosophy was set for the worst case maximum flow condition in a future requirement, or if the original designer used a typical 20% oversizing criteria, there is a great potential for energy savings. However, if there have been expansions, and near full flow requirements are already in use, the potential savings may be limited. Proper evaluation is critical to accessing and correctly applying VFDs.

Flow-generating equipment like fans, pumps and compressors are often used without speed control. Instead, flow is traditionally controlled by throttling with a valve or damper. When fl ow is controlled without regulating the motor speed, it runs continuously at full speed. Because HVAC systems rarely require maximum flow, a system operating without speed control wastes signifi cant energy over most of its operating time. Using VFD to control the motor speed can save up to 70% of the energy.

The mathematical relationship between motor speed, volume or flow, pressure/head and horsepower is not linear. A motor that runs at 100% of its potential speed, volume and pressure will require 100% of its rated horsepower. The same motor run at 80% speed and volume will reduce pressure to 64% and power required to 51%. Sizing a motor that is just big enough for the task will mean that it must run near its maximum load. Sizing a motor larger than the maximum will allow it to run with less power use. If electricity costs $0.08/kWh, a 100-hp motor that is run at 100% speed, 12 hr/day, 360 days a year will cost $27,139 to operate. The same motor run at 60% speed will cost $5,970 a year.

                                       Some system fan motors or pump motors are routinely adjusted to save electricity. Motors can be designed to be two-speed or equipped with variable-speed drives (VSDs), but the best way to control fan volume is with a variable-frequency drive (VFD). A VFD controls the rotational speed of the motor by adjusting the frequency of the power supply. It will add capital cost to the equipment. but it could very easily pay for itself in a short time.

                                 The most obvious candidate for a VFD is a spray booth. In a powder booth the VFD can be used to increase fan volume during clean-up and decrease it during spray operation. Cleaning is more effective if the fan pulls a little harder because it helps to keep powder in the booth. During operation, less air is needed so electricity is saved. The fan can be adjusted to suit a particular operation.

                           A VFD is even more valuable in liquid spray systems. Precise adjustment allows the booth to move just enough air to maintain a clean and safe environment. Air volume can be low when filters are clean, then gradually increased as filters load with paint solids. This approach uses less electricity and exhausts less air. Less exhaust air means that less make-up air is needed, so an added benefit is reduced heating or cooling costs.

                              VFDs can also be used to accelerate oven purge cycles. The fan runs at a faster speed during purge and then slows to the normal volume when purging is complete.

Several other factors can impact motor efficiency. These include supply voltage, phase imbalances, location of capacitors and correct installation and maintenance. Motor supply voltage should be maintained with a maximum deviation of 5% from the nameplate value. Minimizing phase imbalance within 1% will avoid motor de-rating, and installation of capacitors as close to the motor as possible will maintain high power factor.

Adopt a proper motor maintenance strategy for motors. Control ambient temperature to maximize insulation life and motor reliability, and locate motors in well-ventilated areas. Keep them clean and lubricate according to manufacturers' specifications using high-quality greases or oils to prevent contamination with dirt or water.

Optimize transmission efficiency by assuring proper installation and maintenance of shafts, belts, chains, and gears. When replacement becomes necessary, install energy-efficient units. Always have burnt-out motors rewound by a qualified expert.

Flow control methods in comparison to speed control

                 Other typical ways to control the flow are: Throttling control with dampers or valves. Using inlet vanes in centrifugal fans to restrict the flow of air into a fan. Using fluid or eddy current couplings to control the torque between the fan and the motor. On/Off control. Pitch adjustment with axial fans, where the angle of the fan blades is altered to change the flow. The downside of traditional flow control is that none directly affects the main power consumer. There are possibilities to decrease the power consumption of some of these components, but none are as effective in energy efficiency as using speed control with a VFD. For example On/Off control will generate much mechanical stress and pressure peaks due to both the extra starts and stops and the current peaks into the electrical supply when the motor is started without the use of VFD. Fig. 3 below compares the power consumption using throttling control with valve or damper and speed control.

How Drive Changes Motor Speed

Just how does a drive provide the frequency and voltage output necessary to change the speed of a motor? That's what we'll look at next. Fig. 6 shows a basic PWM drive. All PWM drives contain these main parts, with subtle differences in hardware and software components. 

Figure 6, Basic PWM Drive Components

                            Although some drives accept single-phase input power, we'll focus on the 3-phase drive. But to simplify illustrations, the waveforms in the following drive figures show only one phase of input and output. 

                         The input section of the drive is the converter. It contains six diodes, arranged in an electrical bridge. These diodes convert AC power to DC power. The next section-the DC bus section-sees a fixed DC voltage. 

                              The DC Bus section filters and smoothes out the waveform. The diodes actually reconstruct the negative halves of the waveform onto the positive half. In a 460V unit, you'd measure an average DC bus voltage of about 650V to 680V. You can calculate this as line voltage times 1.414. The inductor (L) and the capacitor (C) work together to filter out any AC component of the DC waveform. The smoother the DC waveform, the cleaner the output waveform from the drive. 

                          The DC bus feeds the final section of the drive: the inverter. As the name implies, this section inverts the DC voltage back to AC. But, it does so in a variable voltage and frequency output. How does it do this? That depends on what kind of power devices your drive uses. If you have many SCR (Silicon Controlled Rectifier)-based drives in your facility, see the Sidebar. Bipolar Transistor technology began superseding SCRs in drives in the mid-1970s. In the early 1990s, those gave way to using Insulated Gate Bipolar Transistor (IGBT) technology.

FLEXIBLE POWER ELECTRONIC TRANSFORMER (FPET)

Europe is currently making a great effort in order to improve the sustainability and reduce the environmental impact of its energy and transportation systems. A key role on these initiatives is played by efficient generation systems, like cogeneration, and clean or renewable energies, like wind or solar energy, as well as, by efficient and improved transportation technologies. In the evolution of these energy and transport systems, the development of Power Electronic Converters with greater functionality, higher reliability, higher efficiency, lower cost, and more sophisticated control will be essential. The main goal of future Power Electronic Converters will be to increase power density, reduce cost and improve reliability. This way, volume, weight and material reduction as well as reliability will gain the future market. A great contribution of these goals will be made by new high-power semiconductor devices, which permit the extension of the frequency range of power converters, and consequently the reduction of magnetic components. A good example of one of these systems are medium-frequency power conversion systems, also known as Power Electronic Transformers, which are able to convert electric power as convectional transformers but with increased features: volume and weight reduction, power transfer and quality control etc. The present work introduces a complete characterization of a medium-frequency power transformer, suitable for efficient Power Electronic conversion systems. The motivation of the present work stems out from the need to evaluate the constraints of conventional transformer characterization and design methodologies. The proposed expressions are able to successfully address the problematic related to non-sinusoidal waveforms, typical of medium-frequency power transformers. Moreover, a design methodology for the optimal design of medium-frequency power transformers is introduced. The characterizations, as well as the design methodology, are verified by means of finite element simulations and measurement results.

A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF) or "voltage" in the secondary winding. This effect is called mutual induction. When the output voltage of transformer is higher than its input voltage, it is called the step up transformer and when it lowers the voltage it is called the step down transformer. Since its basic construction requires no moving parts, so it is often called the ‘static transformer, and it is very rugged machine requiring the minimum amount of repair and maintenance. Owing to the lack of rotating parts there are no friction or windage losses. Further, the other losses are relatively low, so that the efficiency of a transformer is high. As there are no teeth, slots or rotating parts, and the windings can be immersed in oil, it is not difficult to insulate transformer for very high voltages.

                     In recent years, significant advances in power semiconductor device technology, low-cost, high-speed control processors, and matured PWM algorithms have led to a number of modern power converter topologies. A new type of transformers based on Power Electronics PE) has been introduced, which realizes voltage transformation, galvanic isolation, and power quality enhancements in a single device. The PE based transformer provides a fundamentally different and more complete approach in transformer design by using power electronics on the primary and secondary sides of the transformer. Several integrated PQ features such as instantaneous voltage regulation under load dynamics and transients, voltage sag compensation, power factor correction, and harmonic suppression can be incorporated into PET, thanks to the application of power electronics technology.

The PET can compensate both the active and reactive powers, and remove the power quality disturbances such as sag, swell, under voltage, over voltage and voltage flicker. In comparison to the conventional transformers, it has low weight, compact volume, extended functionality, and eliminates the necessity for toxic dielectric coolants. The PE-based transformer is a multi-cellular step-down converter that can directly connect to medium voltage levels on the primary side and provide a low voltage, highly stable interface for consumer applications. PET replaces conventional transformers and performs better voltage regulation.

PRINCIPLE OF OPERATION

                The line side AC waveform is modulated with a static converter to a high-frequency square-wave and passed through a HF transformer and again with a synchronous converter, it is demodulated to AC form. Since the transformer size is inversely proportional to the frequency, the high frequency transformer will be much smaller than the line frequency transformer. So, the transformer size, weight and stress factor is reduced noticeably. This scheme can be utilized to mitigate power-line disturbances such as voltage sags and swells in low voltage equipments.

Mathematical relation between transformer size and frequency

The transformer equation E = 4.44(f)(B)(N)(a) where E is the voltage in the winding either primary or secondary, f is the frequency, B is the flux density in the core, N are the number of turns on the winding, and a is the cross area of the core. Power devices operated at magnetic saturation so B is constant. Then it is clear that at higher frequencies the number of winding turns N is reduced.

ADVANTAGES OVER CONVENTIONAL TRANSFORMERS

1.      Active and reactive powers compensation: The power actually consumed in an ac circuit is called active power (VI cosφ). The lagging reactive power is responsible for the low power factor (VI sinφ). Main disadvantages of reactive power are:

a) Large KVA rating of the equipment. Electrical machinery is always rated in KVA.

b) Increase in electricity bill.

c) Losses increases.

d) Decrease in power factor, there by penalty in electricity bill.

                    Devices such as shunt, series, synchronous condenser, DVR, UPQC are widely employed for reactive power compensation. In a weak network is very sensitive to load changes. A sudden change in active load will cause both a phase jump and a magnitude fluctuation in the bus voltage, whereas reactive load changes mainly affect the voltage magnitude. With the addition of energy storage to a static synchronous compensator (StatCom), it is possible to compensate for the active power change as well as providing reactive power support. The PET can compensate both the active and reactive powers.

2.      Flexible regulation of the voltage and power: Regulation means the change in secondary terminal voltage from no load to full load at any particular load (about 4%). On the consumer point it should be as minimum as possible.

3.      Remove the power quality disturbances such as sag, under voltage, over voltage and voltage flicker

4.      Compact: low weight, compact volume.

5.      Eliminates the necessity for toxic dielectric coolants: Mineral oil, beta oil, silicone, envirotemp are widely used coolant materials, cost of coolant higher and its replacement also difficult.

CONSTRUCTION OF PET

Figure 1

n  THREE STAGES

                                                          

n  Cascaded H-bridge (CHB) rectifier (Input stage)

n  Isolation stage

n  Output stage

INPUT STAGE

                  Figure shows the basic block diagram of a power electronic based transformer (PET) which includes three parts. First part or the input stage is an AC/DC converter which is utilized to shape the input current, to correct the input power factor, and to regulate the voltage of primary DC bus. Input stage is an active rectifier to ensure that the input current is sinusoidal.

CASCADED H-BRIDGE CONVERTER

Figure 2

                The CHB converter is the best choice for working in high-voltage and high-power applications due to the extreme modularity, simple physical layout, and low losses. CHB converter has N H-bridge cells connected in series. Each H-bridge consists of four power switches (with anti-parallel diodes) and a DC bus capacitor. Each capacitor feeds a high-frequency DC/DC converter. It is worth noting that the unidirectional rectifier can be realized from the bidirectional rectifier by turning off the upper switches of the H-bridge cells (or by replacing the upper switches with relatively fast diodes). The utilized rectifier contains two parts. At the input side, there is a cascaded H-bridge rectifier which connects directly to the medium voltage levels and corrects the input power factor. The second stage is a modular parallel-output converter which provides a low-voltage and highly-stable DC interface with the consumer applications.

            The modular converter in Figure composed of N individual converter cells, connected in series on the primary side and in parallel on the secondary side. Each converter cell consists of an H-bridge AC-to-DC chopper on the line side to rectify the AC voltage and to stabilize the DC link voltage on the primary side of the individual converter sections. The second part of the converter cells is formed by a DC-to-DC converter. This part of the converter cell contains the HF transformer with the high insulation capability. On the secondary side conventional voltage source inverters or motor drives (which can be part of the respective load) are connected. This stage generates the symmetric three-phase voltages with the desired amplitude and frequency.

SECOND STAGE (ISOLATED DC/DC CONVERTER)

                      Second stage which prepare galvanic isolation between the primary and secondary system. In this part, the DC voltage is converted to a high-frequency square-wave signal, coupled to the secondary of the HF transformer and is rectified to form the DC link voltage.

                      The isolated DC-DC converter constitutes the front-end of two-stage distributed power architectures (DPA) with an intermediate bus voltage feeding non-isolated point-of-load (POL) converters. Usually two-stage DPA schemes do not require a tightly regulated intermediate bus voltage, since the POL will typically accept a relatively wide input voltage, and the POL provides the needed regulation to the load. In general, the topologies not based on bridge configurations are used in single-stage DPA for driving loads directly.

 THIRD STAGE (THREE PHASE INVERTER)

 Figure 7

3-phase inverter with wye connected load

               Three-phase inverters are used for variable-frequency drive applications and for high power applications such as HVDC power transmission. A basic three-phase inverter consists of three single-phase inverter switches each connected to one of the three load terminals. For the most basic control scheme, the operation of the three switches is coordinated so that one switch operates at each 60 degree point of the fundamental output waveform. This creates a line-to-line output waveform that has six steps. The six-step waveform has a zero-voltage step between the positive and negative sections of the square-wave such that the harmonics that are multiples of three are eliminated as described above. When carrier-based PWM techniques are applied to six-step waveforms, the basic overall shape, or envelope, of the waveform is retained so that the 3rd harmonic and its multiples are cancelled.

3-phase inverter switching circuit showing 6-step switching sequence and waveform of voltage between terminals A and C

           To construct inverters with higher power ratings, two six-step three-phase inverters can be connected in parallel for a higher current rating or in series for a higher voltage rating. In either case, the output waveforms are phase shifted to obtain a 12-step waveform. If additional inverters are combined, an 18-step inverter is obtained with three inverters etc. Although inverters are usually combined for the purpose of achieving increased voltage or current ratings, the quality of the waveform is improved as well.

FPET

                The proposed FPET is flexible enough to meet future needs of power electronic centralized systems. The main feature of the FPET is the independent operation of modules each contains one port. Each port can be considered as input or output, because bidirectional power flow is provided. The modules are connected to a common dc link that facilitates energy transfer among modules as well as ports. So a multi-port system is developed that the ports can operate independently. This merit is important for applications, where input and output voltages are different in many parameters. Also the measurement results of a laboratory prototype are presented to verify the capabilities of FPET in providing different output waveforms and controlling load side reactive power. Power Electronic Transformers (PETs) are proposed to replace conventional transformers and perform voltage regulation and power exchange between generation and consumption ports by electronically conversion]. The previous researches show that PETs have a great capacity to receive much more attention due to their merits such as high frequency link transformation and flexible regulation of the voltage and power. Although many studies have been conducted on application and control of PET in power systems, less attention is paid to the areas of the circuit topologies. The topology of PET can be developed in such a way to achieve multi-port electrical system that converts variable input waveform to the desired output waveform. In addition, for higher voltage applications or three phase systems the topology is expandable as it is modular. It is constructed based on modules and a common dc link, which is used to transfer energy between ports and isolate all ports from each other. In this bidirectional topology, each port can be considered as an input or output. Each module consists of three main parts, including modulator, demodulator and High Frequency Isolation Transformer (HFIT). The modulator is a dc-ac converter and the demodulator is an ac-ac converter both with bidirectional power flow capability. Each module operates independently and can transfer power between ports. These ports can have many different characteristics, such as voltage level, frequency, phase angle and waveform. As a result, FPET can satisfy almost any kind of application, which are desired in power electronic conversion systems and meet future needs of electricity networks.

               Each port of FPET is composed of a Full-Bridge DC link Inverter (FBDCI), HFIT and a cycloconverter. This topology consists of independent and similar modules and each port can work independently. Thus analysis of one port is sufficient to introduce whole topology. The FBDCI (modulator) can operate as an inverter when it converts the dc link voltage to an ac waveform at the HFIT side. It can operate as an active rectifier when it converts the ac waveform of the HFIT to the dc link voltage.

The modulator description is expressed as follows:

a. Bidirectional power flow capability

b. Adjustable switching frequency which feet voltage pulses frequency it into the pass-band of HFIT, and

c. Stored energy in the dc link (if the modulator is in active rectifier mode).

For cycloconverters, several circuit topologies can be proposed using unidirectional or bidirectional switches. In this paper, a typical cycloconverter with two bidirectional switches operates as the demodulator. The demodulator converts high frequency voltage (i.e. Vs) to low frequency voltage (i.e. Vpr1) and vice versa. The specifications of the demodulator are listed as follows:

 a. Bidirectional power flow capability

b. Providing zero voltage switching by turning the switches of cycloconverter on/off, while voltage of HFIT riches to zero.

APPLICATIONS

1.      Dynamic Voltage Restorer (DVR) and Active Filter (AF):  Dynamic Voltage Restorer (DVR) and Active Filter (AF) [16] applications can be satisfied by the FPET, because it can connect to the grid in series or/and in parallel. Desired voltage and current can provide by the flexibility of FPET in providing various waveforms. Voltage sag is one of the power quality issue and DVR is using for mitigation of voltage sag.

2.      Universal Power Quality Conditioner (UPQC): FPET can provide desired waveform in each phase (or port) independently, so this can be used in Universal Power Quality Conditioner (UPQC).

3.      Interline Power Flow Controller (IPFC): FPET can transfer active and reactive power from one port or phase to another port or one phase. This in power distribution system is very useful for Interline Power Flow Controller (IPFC).

4.      Uninterruptible Power Supply application (UPS): FPET can provide symmetrical three phase voltage from an asymmetrical ac source in the form of an Uninterruptible Power Supply application (UPS).

5.      Renewable energy applications: FPET can play a role in providing useful power from variable Low voltage dc sources. That is suitable for renewable energy applications such as photovoltaic and fuel cell.

6.      Aircraft and shipboard: PET will have a major impact on the utility industry and the places such as aircraft and shipboard where the high quality power conversion is very desirable.