**3.1 Methods for adapting the electrical consumers to DC grid parameters**

In order to establish the proper methods regarding the consumers' adaptability to a DC grid, it is necessary to identify the ones which are to be used and to analyze the possibilities of modifying the included power supply. The classification of electrical appliances that are usually found in a household is therefore highlighted. The main categories of electric consumers can be defined as follows:


A step-down converter with 48 V input and 5–9–12–20–24 V output operates with very good conversion efficiency. Due to the fact that it does not process significant power amounts, it has an affordable price.

*Micro-Grids - Applications, Operation, Control and Protection*

**MCB's characteristics IEC 60898-1 IEC60947-2**

**Regulated for: Residential domain Industrial domain** Rated current, *In* 6–125 A 0.5–160 A Maximum current, *Icn* 25 kA 30 kA Rated voltage, *Ue* 400 V 440, 500, 690 V Impulse voltage, *Uimp* 4 kV 6 or 8 kV Degree of protection 2 3 Trigger curves B, C, D B, C, D, K, Z, MA Operation mode AC AC or DC Maximum ambient temperature 30°C 50°C

Electrical auxiliaries No Monitoring and control

*Comparison between the characteristics of miniature circuit breakers (MCBs) regulated according to IEC [12].*

current, IEC 60947-2 shows that instantaneous triggering may be adjustable in accordance to the user's necessities or predefined by the manufacturer with a precision of 20%. This is the reason why many manufacturers have added K, Z, and MA curves (**Figure 3**). In conclusion, the use of MCBs which are certified according to both standards

*Examples of Resi9 circuit breakers for residential applications and Eazy9 for industrial use manufactured by* 

This standard is applicable to fuses incorporating enclosed current-limiting fuse links with rated breaking capacities of not less than 6 kA, intended for protecting power-frequency AC circuits of nominal voltages not exceeding 1000 V or DC

The standard has been updated and released again as SR EN 60269-1:2008/

and are suitable for residential as well as industrial use is preferable.

circuits of nominal voltages not exceeding 1500 V.

A1:2010 and SR EN 60269-1:2008/A2:2015.

• *IEC/EN 60269-1 Low-voltage fuses—Part 1: General requirements*

**42**

**Figure 3.**

**Table 1.**

*Schneider [13].*

Currently, the home appliance industry is mainly focused on AC power supplied products. Still, there are an increasing number of DC power devices that use switching mode power supplies (SMPS) for AC conversion and voltage level adjustment. These devices can be modified by eliminating the rectifying and power factor correction modules.

SMPS are electronic power sources which include switching regulators for the efficient energy conversion. SMPS use a transistor (or a group of pass transistors) that continuously switch between low-dissipation, full-on, and full-off states in order to remain as little as possible in high-dissipation transitions, thus minimizing the wasted energy. Ideally, switching mode power supplies do not dissipate any power. Voltage regulation is achieved by varying the time ratio between saturation and blocking. High power conversion efficiency represents an important advantage of a switching power supply. Also, SMPS can have significantly reduced dimensions and be lighter than a linear power supply due to the size and the weight of the included transformer. Switching regulators are used as replacements for the linear regulators when higher efficiency or more reduced size and weight are required. These are, however, much more complicated; if not suppressed, current can cause electrical noise problems during switching, while the simple models may have a low power factor. Ideal switching elements (e.g., transistors operating outside their active mode) have no resistance when "open" and do not carry any electrical current when "closed." Therefore, converters are able to theoretically operate with 100% efficiency (e.g., all input current is delivered to the load, and no current is wasted as dissipated heat).

The output of the switching source is adjusted by using the fill factor control; the transistors are switched in fully closed or open stages, so that the resistance losses between input and load are limited. The only amount of generated heat results from the non-ideal characteristics of the used components and from the residual currents related to the control circuits.

The losses due to transistors' switching (especially in the short part of each cycle when the device is partially activated), the switching transistors' resistance, the series resistance of both the inductor and capacitors, and the inductor's iron losses as well as the voltage drop on the rectifier diodes lead to a specific efficiency of about 60–70%. However, the optimization of the SMPS design (choosing the optimal switching frequency, avoiding inductor saturation, and active rectifying) will provide the minimization of the energy losses. Thus, an optimal switching source configuration will be characterized by 95% efficiency.

The efficiency of the DC/DC converters is comparable to that of the switching sources if considering that the operating principle is similar after the point of power factor rectifying and correction. Most currently manufactured SMPS also include power factor compensation circuits in order to reduce grid losses and disturbances and to comply with international regulations.

The unity power factor represents the objective of any power generating company, because otherwise, a higher current value has to be provided to the end users for a certain power demand. In this respect, the manufacturer sustains higher line losses. In the case of an industrial power plant, a penalty is charged if the power factor is way different from 1 (under the neutral power factor of 0.92). Mainly, motors' windings act as inductors within the public distribution grid. Opposite effect capacitors which are compensating the motors' inductive windings can be used.

SMPS do not operate as reactive loads like the electric motors but instead represent nonlinear loads for the power supply grid. Sources without power factor correction (PFC) absorb high current pulses or spikes from the AC grid (which provides sinusoidal voltage) due to the low conduction angle in the input stage that carries out the rectifying. If left uncompensated, a switching source power factor (PF) will generally be equal to 0.65 or even lower. PF can be compensated

**45**

*Assessment of the Main Requirements and Characteristics Related to the Implementation of…*

by using power factor correction circuits. These circuits smooth current pulses, improve PF, and reduce the possibility of the AC circuit breaker safety devices to act

There are two basic types of PFCs: passive and active. Passive PFC circuits are less expensive and usually can compensate the power factor at around 0.85. The PFC active circuits are the most used ones and are even included by the power supply source, thus increasing PF over 0.98. A close to 1 PF indicates good power

Due to the high increase of household appliances that include power supplies which add up to existing consumers, since 2001 the European Union (EU) has set harmonic currents' limits that can occur within the AC power grid and are caused

The most important regulation is EN61000-3-2 which relates to SMPS with input power of over 75 W while absorbing up to 16 A electric current. Severe limits regarding up to the 39th harmonic currents, measured at the power supply input, are set. For example, EU has established a 50 Hz value for the frequency of the first harmonic. The third harmonic is equal to 150 Hz, while the 39th harmonic equal to 1950 Hz. These unwanted harmonic currents have a direct connection to the SMPS power factor. PFC significantly reduces the AC harmonics, leaving mainly the "fundamental," which is in phase to the waveform. Power supplies that meet the EN61000-3-2 standard are normally characterized by a power factor higher than 0.97. PFC increases the power supply capacity, thus determining the amount of useful energy which SMPS will use from the AC grid and then deliver it to a load. The rela-

Many technologies and topologies can be and were designed for PFC. When dealing with low installed energy (even up to 200 W), various passive PFC techniques have been used in order to increase the conduction angle of the electric

It can therefore be concluded that if SMPS include the power factor correction module, the conversion efficiency will be similar to the case of DC/DC converters. In the absence of power factor correction circuits, the DC power supply will

Moreover, if the foreseen household DC grid is characterized by a nominal voltage that coincides with the rectified voltage of an equipment switching source, then the appliance is ought to be directly connected to the DC power grid without

Recent developments in the field of electric drives have allowed the large-scale use of Inverter technology for most household appliances using significant power motors. The main purpose of this technology is to increase the energy efficiency by varying the motor speed which can also operate on partial loads. The Inverter technology represents the most recent technological evolution regarding the compressors' electric motors. The inverter is used in order to continuously adjust the temperature by controlling the speed of the compressor motor. The DC inverter units dispose of a variable frequency drive, comprising an adjustable electric inverter which controls the speed of the electric motor and of the compressor, respectively. The unit converts the AC current input to DC, and then by modulating it through an inverter, it produces the foreseen current frequency. A microcontroller will acquire each value of the ambient air temperature and therefore adjust the compressor speed accordingly. The inverter air conditioning systems operate more efficiently than conventional ones, providing extended lifetime of their components

*Pout = VRMS*·*IRMS*·*PF*·*Efficiency* (1)

tion showing the abovementioned is shown in Eq. (1):

contribute to reducing losses in the power transformation chain.

*DOI: http://dx.doi.org/10.5772/intechopen.84413*

prematurely.

by SMPS.

supply performance.

current waveform [15].

any further changes.

*Assessment of the Main Requirements and Characteristics Related to the Implementation of… DOI: http://dx.doi.org/10.5772/intechopen.84413*

by using power factor correction circuits. These circuits smooth current pulses, improve PF, and reduce the possibility of the AC circuit breaker safety devices to act prematurely.

There are two basic types of PFCs: passive and active. Passive PFC circuits are less expensive and usually can compensate the power factor at around 0.85. The PFC active circuits are the most used ones and are even included by the power supply source, thus increasing PF over 0.98. A close to 1 PF indicates good power supply performance.

Due to the high increase of household appliances that include power supplies which add up to existing consumers, since 2001 the European Union (EU) has set harmonic currents' limits that can occur within the AC power grid and are caused by SMPS.

The most important regulation is EN61000-3-2 which relates to SMPS with input power of over 75 W while absorbing up to 16 A electric current. Severe limits regarding up to the 39th harmonic currents, measured at the power supply input, are set. For example, EU has established a 50 Hz value for the frequency of the first harmonic. The third harmonic is equal to 150 Hz, while the 39th harmonic equal to 1950 Hz. These unwanted harmonic currents have a direct connection to the SMPS power factor. PFC significantly reduces the AC harmonics, leaving mainly the "fundamental," which is in phase to the waveform. Power supplies that meet the EN61000-3-2 standard are normally characterized by a power factor higher than 0.97.

PFC increases the power supply capacity, thus determining the amount of useful energy which SMPS will use from the AC grid and then deliver it to a load. The relation showing the abovementioned is shown in Eq. (1):

$$P\_{\text{out}} = V\_{\text{RMS}} \cdot I\_{\text{RMS}} \cdot PF \cdot E\text{ff}\text{fricence} \,\text{y} \tag{1}$$

Many technologies and topologies can be and were designed for PFC. When dealing with low installed energy (even up to 200 W), various passive PFC techniques have been used in order to increase the conduction angle of the electric current waveform [15].

It can therefore be concluded that if SMPS include the power factor correction module, the conversion efficiency will be similar to the case of DC/DC converters. In the absence of power factor correction circuits, the DC power supply will contribute to reducing losses in the power transformation chain.

Moreover, if the foreseen household DC grid is characterized by a nominal voltage that coincides with the rectified voltage of an equipment switching source, then the appliance is ought to be directly connected to the DC power grid without any further changes.

Recent developments in the field of electric drives have allowed the large-scale use of Inverter technology for most household appliances using significant power motors. The main purpose of this technology is to increase the energy efficiency by varying the motor speed which can also operate on partial loads. The Inverter technology represents the most recent technological evolution regarding the compressors' electric motors. The inverter is used in order to continuously adjust the temperature by controlling the speed of the compressor motor. The DC inverter units dispose of a variable frequency drive, comprising an adjustable electric inverter which controls the speed of the electric motor and of the compressor, respectively. The unit converts the AC current input to DC, and then by modulating it through an inverter, it produces the foreseen current frequency. A microcontroller will acquire each value of the ambient air temperature and therefore adjust the compressor speed accordingly. The inverter air conditioning systems operate more efficiently than conventional ones, providing extended lifetime of their components

*Micro-Grids - Applications, Operation, Control and Protection*

correction modules.

Currently, the home appliance industry is mainly focused on AC power supplied products. Still, there are an increasing number of DC power devices that use switching mode power supplies (SMPS) for AC conversion and voltage level adjustment. These devices can be modified by eliminating the rectifying and power factor

SMPS are electronic power sources which include switching regulators for the efficient energy conversion. SMPS use a transistor (or a group of pass transistors) that continuously switch between low-dissipation, full-on, and full-off states in order to remain as little as possible in high-dissipation transitions, thus minimizing the wasted energy. Ideally, switching mode power supplies do not dissipate any power. Voltage regulation is achieved by varying the time ratio between saturation and blocking. High power conversion efficiency represents an important advantage of a switching power supply. Also, SMPS can have significantly reduced dimensions and be lighter than a linear power supply due to the size and the weight of the included transformer. Switching regulators are used as replacements for the linear regulators when higher efficiency or more reduced size and weight are required. These are, however, much more complicated; if not suppressed, current can cause electrical noise problems during switching, while the simple models may have a low power factor. Ideal switching elements (e.g., transistors operating outside their active mode) have no resistance when "open" and do not carry any electrical current when "closed." Therefore, converters are able to theoretically operate with 100% efficiency (e.g., all input current is

The output of the switching source is adjusted by using the fill factor control; the transistors are switched in fully closed or open stages, so that the resistance losses between input and load are limited. The only amount of generated heat results from the non-ideal characteristics of the used components and from the

The losses due to transistors' switching (especially in the short part of each cycle when the device is partially activated), the switching transistors' resistance, the series resistance of both the inductor and capacitors, and the inductor's iron losses as well as the voltage drop on the rectifier diodes lead to a specific efficiency of about 60–70%. However, the optimization of the SMPS design (choosing the optimal switching frequency, avoiding inductor saturation, and active rectifying) will provide the minimization of the energy losses. Thus, an optimal switching

The efficiency of the DC/DC converters is comparable to that of the switching sources if considering that the operating principle is similar after the point of power factor rectifying and correction. Most currently manufactured SMPS also include power factor compensation circuits in order to reduce grid losses and disturbances

The unity power factor represents the objective of any power generating company, because otherwise, a higher current value has to be provided to the end users for a certain power demand. In this respect, the manufacturer sustains higher line losses. In the case of an industrial power plant, a penalty is charged if the power factor is way different from 1 (under the neutral power factor of 0.92). Mainly, motors' windings act as inductors within the public distribution grid. Opposite effect capacitors which are compensating the motors' inductive windings can be used. SMPS do not operate as reactive loads like the electric motors but instead represent nonlinear loads for the power supply grid. Sources without power factor correction (PFC) absorb high current pulses or spikes from the AC grid (which provides sinusoidal voltage) due to the low conduction angle in the input stage that carries out the rectifying. If left uncompensated, a switching source power factor (PF) will generally be equal to 0.65 or even lower. PF can be compensated

delivered to the load, and no current is wasted as dissipated heat).

source configuration will be characterized by 95% efficiency.

residual currents related to the control circuits.

and to comply with international regulations.

**44**

#### **Figure 4.**

*Inverter technology freezer developed by Mitsubishi [16].*

and not introducing disturbances to the main grid. An example of a freezer Inverter technology implemented by Mitsubishi is shown within **Figure 4**.

As shown in **Figure 4**, the system includes an AC/DC rectifying module, subsequently used in order to reshape the sinusoidal waveform along with the variable frequency required by the compressor and fan motors. It can thus be directly supplied with adequate DC voltage without any additional problems.

In the case of DC-powered equipment with low voltage levels, it has been shown previously that DC/DC converters can be used successfully.

DC/DC converters represent power supplies that convert electrical power with an unstable DC input voltage into a stabilized DC output voltage, to different values, lower value (step-down), higher value (step-up), and equal (stable level), or to inverse polarity comparing the input voltage (invert).

The more complex converters are based on microcontrollers in order to ensure high efficiency and as low as possible size, disturbances, and thermal dissipation losses. DC/DC converters are generally used in order to isolate electrical noise, for galvanic isolation, to voltage level conversion, and to provide a stable voltage level for voltage-sensitive equipment and various battery voltage values which supply portable equipment. Power density, efficiency, and reliability represent the basic characteristics which are considered for the price/performance ratio evaluation of a DC/DC converter. DC/DC converters are widely used either for fixed equipment power supplies (supplied from the AC grid) or for portable (battery powered) and IT equipment (where various voltage values are required for CPU, RAM, memory drives, and interfaces) [17].

DC/DC converters are basically SMPS with the following advantages:


**47**

*Assessment of the Main Requirements and Characteristics Related to the Implementation of…*

1000 V DC), which cannot be achieved by a linear source.

noise, with specialized controllers embedded in integrated circuits.

(within the AC grid) by IT equipment are covered by EN 55022 standard.

when using a transformer, galvanic isolation can be provided (minimum

The basic operating principle of a DC/DC converter regards the command of a high frequency switching element (at least 100 kHz) by variably controlling the on-time/off-time ratio ("duty ratio") in order to keep the output voltage at a certain value. Usually, the voltage is constantly controlled through the negative feedback of the output voltage. Some switching sources also solve the problem of electrical

It is worth mentioning that about 80% of electromagnetic compatibility (EMC) problems are due to both power and I/O cables which produce an unintended "antenna structure." This structure can emit the electromagnetic energy generated by productembedded electronic components and also receive the electromagnetic energy from the product's exterior. EMC regards electromagnetic interference (EMI) which stands as the amount of emitted energy, whether intentionally or otherwise, by electronic equipment that cause performance degradation on nearby equipment. Also, EMC addresses electromagnetic susceptibility (EMS) and the lack of immunity to internal or external interference, respectively. Emissions of radiated or conducted disturbances

EN 55024 and EN 61000-4-2, 3, 4, 5, 6, and 8 standards regulate immunity to electrostatic discharges (ESD), intentional radio emissions, switching noise or electrical transitory regimes, lightning, 50–60 Hz variable magnetic fields, and

The maximum efficiency of the operating switching sources is associated to a well-designed load when the equipment is power supplied similarly to the nominal regime parameters, yet considering a certain reserve of power. For example, a source works seamlessly with a load of only 10%, but energy conversion losses are

Therefore, manufacturers have developed switching sources suitable to a wide range of products provided with different input/output voltage values while characterized by efficiency between 70 and 96% and a few watts up to several thousand watts power. Also, there are available various sources with a wide range of input and output voltage control according to the consumer's parameters. Thus, the same source is able to supply equipment that work at 5, 9, 12, 20, 24, and 48 V. The voltage can be adjusted before coupling, whether it is the case of a single output related to an only consumer or the case of a single source ensuring different simultaneous voltage

A solution for integrating these DC/DC converters in order to supply office

From 24 V DC, the voltage can be reduced to the required voltage in order to power each device. A DC/DC converter can be mounted in a distribution panel for adapting the voltage from 380 to 24 V DC. Then, by using a low-power converter, the power can be transmitted to consumers through a device that integrates mul-

In order to power up electrical consumers with different voltage values such as laptops, monitors, and mobile phones that require voltage below 24 V AC, a buck converter can be integrated into a compact unit that incorporates multiple outlets. The coupling terminals for each voltage are integrated into the socket that can supply up to 100 W. When considering only AC operating equipment, DC/AC converters (inverters) must be used. This solution is more complicated in terms of power electronics and thus more expensive. Inverters are provided with DC voltage (or current) source as input that converts it into alternating voltage (or current) for output, which can

*DOI: http://dx.doi.org/10.5772/intechopen.84413*

power fluctuations in the AC grid [17].

higher than in the case of 80–90% load.

values through dedicated terminals.

tiple outlets. Such a device is shown in **Figure 6**.

equipment is shown in **Figure 5**.

#### *Assessment of the Main Requirements and Characteristics Related to the Implementation of… DOI: http://dx.doi.org/10.5772/intechopen.84413*

when using a transformer, galvanic isolation can be provided (minimum 1000 V DC), which cannot be achieved by a linear source.

The basic operating principle of a DC/DC converter regards the command of a high frequency switching element (at least 100 kHz) by variably controlling the on-time/off-time ratio ("duty ratio") in order to keep the output voltage at a certain value. Usually, the voltage is constantly controlled through the negative feedback of the output voltage. Some switching sources also solve the problem of electrical noise, with specialized controllers embedded in integrated circuits.

It is worth mentioning that about 80% of electromagnetic compatibility (EMC) problems are due to both power and I/O cables which produce an unintended "antenna structure." This structure can emit the electromagnetic energy generated by productembedded electronic components and also receive the electromagnetic energy from the product's exterior. EMC regards electromagnetic interference (EMI) which stands as the amount of emitted energy, whether intentionally or otherwise, by electronic equipment that cause performance degradation on nearby equipment. Also, EMC addresses electromagnetic susceptibility (EMS) and the lack of immunity to internal or external interference, respectively. Emissions of radiated or conducted disturbances (within the AC grid) by IT equipment are covered by EN 55022 standard.

EN 55024 and EN 61000-4-2, 3, 4, 5, 6, and 8 standards regulate immunity to electrostatic discharges (ESD), intentional radio emissions, switching noise or electrical transitory regimes, lightning, 50–60 Hz variable magnetic fields, and power fluctuations in the AC grid [17].

The maximum efficiency of the operating switching sources is associated to a well-designed load when the equipment is power supplied similarly to the nominal regime parameters, yet considering a certain reserve of power. For example, a source works seamlessly with a load of only 10%, but energy conversion losses are higher than in the case of 80–90% load.

Therefore, manufacturers have developed switching sources suitable to a wide range of products provided with different input/output voltage values while characterized by efficiency between 70 and 96% and a few watts up to several thousand watts power.

Also, there are available various sources with a wide range of input and output voltage control according to the consumer's parameters. Thus, the same source is able to supply equipment that work at 5, 9, 12, 20, 24, and 48 V. The voltage can be adjusted before coupling, whether it is the case of a single output related to an only consumer or the case of a single source ensuring different simultaneous voltage values through dedicated terminals.

A solution for integrating these DC/DC converters in order to supply office equipment is shown in **Figure 5**.

From 24 V DC, the voltage can be reduced to the required voltage in order to power each device. A DC/DC converter can be mounted in a distribution panel for adapting the voltage from 380 to 24 V DC. Then, by using a low-power converter, the power can be transmitted to consumers through a device that integrates multiple outlets. Such a device is shown in **Figure 6**.

In order to power up electrical consumers with different voltage values such as laptops, monitors, and mobile phones that require voltage below 24 V AC, a buck converter can be integrated into a compact unit that incorporates multiple outlets. The coupling terminals for each voltage are integrated into the socket that can supply up to 100 W.

When considering only AC operating equipment, DC/AC converters (inverters) must be used. This solution is more complicated in terms of power electronics and thus more expensive. Inverters are provided with DC voltage (or current) source as input that converts it into alternating voltage (or current) for output, which can

*Micro-Grids - Applications, Operation, Control and Protection*

and not introducing disturbances to the main grid. An example of a freezer Inverter

In the case of DC-powered equipment with low voltage levels, it has been shown

DC/DC converters represent power supplies that convert electrical power with

The more complex converters are based on microcontrollers in order to ensure high efficiency and as low as possible size, disturbances, and thermal dissipation losses. DC/DC converters are generally used in order to isolate electrical noise, for galvanic isolation, to voltage level conversion, and to provide a stable voltage level for voltage-sensitive equipment and various battery voltage values which supply portable equipment. Power density, efficiency, and reliability represent the basic characteristics which are considered for the price/performance ratio evaluation of a DC/DC converter. DC/DC converters are widely used either for fixed equipment power supplies (supplied from the AC grid) or for portable (battery powered) and IT equipment (where various voltage values are required for CPU, RAM, memory

an unstable DC input voltage into a stabilized DC output voltage, to different values, lower value (step-down), higher value (step-up), and equal (stable level), or

DC/DC converters are basically SMPS with the following advantages:

• Very high efficiency comparing to the case of linear sources (typically

• Reduced energy transfer loss since all the components are smaller and require

• The energy stored by a coil from a switching regulator can be supplied with higher voltage than the input voltage (boost) or even negative (inverted);

As shown in **Figure 4**, the system includes an AC/DC rectifying module, subsequently used in order to reshape the sinusoidal waveform along with the variable frequency required by the compressor and fan motors. It can thus be directly

technology implemented by Mitsubishi is shown within **Figure 4**.

*Inverter technology freezer developed by Mitsubishi [16].*

supplied with adequate DC voltage without any additional problems.

previously that DC/DC converters can be used successfully.

to inverse polarity comparing the input voltage (invert).

**46**

drives, and interfaces) [17].

simple thermal management.

75–90%).

**Figure 4.**

**Figure 5.** *Power supply infrastructure for office equipment [18].*

**Figure 6.** *Power supply device for low-power equipment [19].*

have adjustable frequency and/or voltage. Usually, inverters are used to drive AC motors with adjustable rotational speed but are also applicable to other domains, for example, the case of uninterruptible power supplies (UPS). It is therefore necessary to convert the voltage value of about 300 V DC to 220–240 V AC. The on the market wide available solutions usually convert low voltages (12/24/48 V DC) due to the fact that they are required in backup systems which use battery storage for the electric power generated by photovoltaic panels or wind/water turbines. The fact that there is no market for 300 V DC/240 V AC poses a challenge and is due to this system's high price which needs to be produced on special orders. Standard inverters that accept low voltage inputs may be used, but the considered electric grid must

**49**

**Figure 7.**

*Assessment of the Main Requirements and Characteristics Related to the Implementation of…*

support higher current values for the same transferred power. It can also be used along with step-down converters, but the solution is costly and inefficient increas-

ing power supplies or *Inverter* technology to drive washing machine motors or

**3.2 Considerations regarding the assessment of a typical household required** 

According to Siemens, buildings account on about 40% of global energy consumption and 21% of greenhouse gas emissions, respectively. Consequently, buildings represent the key to reduce energy consumption and support sustainable urban development. The use of modern technology in intelligent buildings can reduce

Thus, the intelligent house concept is evolving in response to technological progress regarding distributed energy sources as well as information and telecommunication technology, so that through management systems, consumers can contribute to more efficient use of electric power. The use of smart home energy management systems will

According to the 2016–2030 Romania's Energy Strategy, [21], with 2050 perspectives, the electricity consumption for 2016 by its destination is shown in **Figure 7**. The used electric power in MW by activity sectors is also indicated by **Figure 8**.

According to the 2016–2030 Romania's Energy Strategy, [21], with 2050 perspec-

tives, the share of household consumption will not change significantly. Due to technological progress, it is still possible that the energy share is related to a house-

All of the aforementioned aspects show that switching home appliances to DC power configurations can be achieved without any significant problems or at significant costs. The transition is easier when using new equipment that mainly embeds switch-

Older generation equipment that still uses transformers or AC motors requires more significant changes of the power sources or the use of DC/AC converters. These aspects do not stand as obstacles to the development of DC grid when considering that the aging of old appliances will gradually eliminate them and lead to their replacement with newer technology that is easily adaptable to the DC grid.

*DOI: http://dx.doi.org/10.5772/intechopen.84413*

**power**

ing the losses on the power transformation chain.

compressors for refrigerators and air conditioning systems.

emissions to 40% without affecting the comfort of residents.

allow the end users to efficiently use low-cost electric or thermal power [20].

hold to vary between certain limits depending on the appliances within.

*Diagram regarding the final electric power consumption [MW] [21].*

#### *Assessment of the Main Requirements and Characteristics Related to the Implementation of… DOI: http://dx.doi.org/10.5772/intechopen.84413*

support higher current values for the same transferred power. It can also be used along with step-down converters, but the solution is costly and inefficient increasing the losses on the power transformation chain.

All of the aforementioned aspects show that switching home appliances to DC power configurations can be achieved without any significant problems or at significant costs.

The transition is easier when using new equipment that mainly embeds switching power supplies or *Inverter* technology to drive washing machine motors or compressors for refrigerators and air conditioning systems.

Older generation equipment that still uses transformers or AC motors requires more significant changes of the power sources or the use of DC/AC converters.

These aspects do not stand as obstacles to the development of DC grid when considering that the aging of old appliances will gradually eliminate them and lead to their replacement with newer technology that is easily adaptable to the DC grid.
