Electric vehicles (EVs) have received special consideration from modern society over the past several years. Although EVs are a fine example of environmentally friendly technology and have many advantages, they relatively increase the electricity demand upon a power grid as well. Therefore, their negative impact on busvoltage and line losses should be analyzed. In this study, the effect of EV loads and their penetration on bus voltage and line losses of an IEEE-33 bussystem has been examined via two scenarios. It is important to mention that the effect of EVs on the rate of air pollution, produced by fossil fuel electricity generators, has been investigated throughout the study. Also, the key role of demand response programs in the reduction of EVs’ negative effects on the grid has also been discussed in the last scenario. Generally, the simulation of this paper provides a novel and wider perspective on EVs and their effect on grids and environmental pollution.
The continual development of technology and power grid innovations provides a great opportunity for benefit from electric transportation. EVs have a major role in such systems [
According to the above-mentioned claim, EVs as a novel concept in the world has both advantages and disadvantages. Moving toward a near-zero-emission energy policy reinforces the tendency to use EVs as a green technology [
The green tax, developed countries’ policies, like the USA and Norway, and the importance of using EVs have been comprehensively discussed in [
There are a lot of works related to considering EVs and their impact on power grids. Dharmakeerthi et al. [
The authors in [
In this research, the effect of the EV load and the various percentages of EV penetration on buses voltage and line losses of an IEEE 33 bus system has been evaluated. Furthermore, the interaction between renewable-based supply and EV’s load for declining air pollution generated by fossil fuel generation has been discussed. This feature indicates that EVs are a completely low-emission way if renewable resources are considered for their changing power, and also that we are supposed to determine the best location for erecting EV charging stations because this matter could decrease the line losses and subsequently the air pollution. As another noteworthy aspect of this research indicates, the positive effect(s) of demand response scheduling has been defined as an appropriate way to tackle the EV loads problem.
In the rest of the paper, the second section includes methodology and equations. The simulation and results have been comprehensively discussed through various scenarios in the third section. This section provides detailed comparisons to explain different situations in more detail. The last section has concluded the all section and outputs of this research.
In this research, the proposed method is applied to a 33-bus distribution grid [
In the above-mentioned IEEE 33 bus grid, the type of all the buses is PQ excluding the first bus which is a slack bus. Furthermore, all the buses were changed to the per-unit system according to the first bus.
Because of their nonlinearity, the load flow equation solving needs iterative numerical methods. One of the high usage solving methods is the Modified Gauss-Seidel method [
In the first step, the initial guess is chosen and the voltage in each iteration is calculated with the above formula until the voltage value converges to the desired value. Convergence here means the difference between consecutive voltage values should be lower than a small value. The active and reactive power is calculated by
The initial guess is usually chosen
After iterative calculation of bus voltage, the calculation of lines loss is the next step. Current
Current in the reverse direction is also calculated likewise:
Complex power between two buses is obtained according to the below equations:
Consequently, power loss in the line is calculated as below:
In this section, simulation and corresponding results are presented. A network, which has a generator and 33 buses, is considered according to [
This network is known as a fundamental example for this research and per unit bus voltage is presented in
According to expectation, the 18th bus has a minimum voltage value because of lines power losses.
The total line losses remains an important factor that should be analyzed in such research. Therefore, the total line losses are presented in
The simulation part of this research has been introduced through three various scenarios. The first scenario evaluates the impact of EVs on the grid. The number of EV loads and their effect on the grid have been discussed in the second scenario. Finally, the importance of a well-organized plan for dealing with EV load has been indicated by the third scenario.
Senario1-The effect of EV loads on line losses and air pollution
Senario2-Considering different percentages for EV penetration
Senario3-Effect of energy management on grids factors
Basic condition (without EV loads) | |
---|---|
Ploss | 281.5877 (kw) |
Qloss | 187.9595 (kw) |
The effect of EV loads on power losses has been considered through three cases in which EV loads with the same penetration have existed in different buses:
EV with 50 percent penetration rate at bus 10.
EV with 50 percent penetration rate at bus 18.
EV with 50 percent penetration rate at bus 25.
The effective total EV’s consuming power is considered 50 kW in this research. In other words, A station with a single 50 KW fast charger has been introduced for EV loads. The proposed model of EV load has been given from [
EV with 50 percent penetration rate at bus 10:
After considering EV loads for the 10^{th} bus, the voltage of buses and power losses have been depicted in
Lines total power loss is another important comparison criterion and illustrates a negative effect of extra loads on the line parameters. The below
EV in 10^{th} bus | |
---|---|
Ploss | 290.0365 |
Qloss | 193.7792 |
EV with 50 percent penetration rate at bus 18:
It is obvious that further distance between the generator and the load leads to more line power loss and lower bus voltage. Therefore, the network of this case has lower buses voltage and more line power loss than the previous case. According to
Due to further distance, this condition has the biggest total line losses among all situations, subsequently, causes the biggest cost and greater air pollution for grids.
EV with 50 percent penetration rate at bus 25:
EV in 18^{th} bus | |
---|---|
Ploss | 292.4519 |
Qloss | 195.7629 |
The electric vehicle is connected to the network at bus 25 which is different from two previous cases. Because the load consumption is closer to the generator bus in this case, the total power loss would expect to be lower than in either two previous cases, which is given in
EV in 25^{th} bus | |
---|---|
Ploss | 285.0831 |
Qloss | 190.1345 |
Comparisons of these cases, which are shown in
Basic condition (without EV loads) | EV in 10^{th} bus | EV in 18^{th} bus | EV in 25^{th} bus | |
---|---|---|---|---|
Ploss | 281.5877 | 290.0365 | 292.4519 | 285.0831 |
Qloss | 187.9595 | 193.7792 | 195.7629 | 190.1345 |
It is obvious that an increase in loads needs more supply generation because the balance between supply and generation should be always kept around a confident boundary. According to the definition, air pollution, which is produced by the increase in the supply of fuel-based generators, has been investigated here. The following table presents the growth in the percentage of air pollution due to various EV loads location. It can conclude from
EV in 10^{th} bus | EV in 18^{th} bus | EV in 25^{th} bus | |
---|---|---|---|
Percentage of air pollution increase | 1.588% | 1.642% | 1.45% |
As mentioned previously, the local power generation, especially renewable energy-based power generation, can cause a decrease in the rate of air pollution which is caused by EV loads. The following
EV in 10^{th} bus | EV in 18^{th} bus | EV in 25^{th} bus | |
---|---|---|---|
Percentage of air pollution decrease due to use of renewable resources | 0.635% | 0.6548% | 0.5814% |
In this section, the effect of electric vehicle penetration rate on buses voltage and power losses are considered in a grid with electric vehicles at buses 8, 18, and 30.
Electric vehicles with different penetration rates have different effects on the voltage of buses. More penetration rate causes lower bus voltage and further line power losses. Therefore, the percentage of EV penetration is an important factor and should be considered in such systems and governments’ energy policies. Providing energy supply locally can be a suitable way for decreasing the percentage of penetration. According to this issue, solar-based EV stations have received special consideration recently and this concept is depicted in
Ultimately, the growth of the percentage of EV penetration causes more line losses. Also, this growth decreases the voltage of buses. So, as was mentioned, to tackle the negative impact of the extra load caused by EVs, useful ways such as optimization, restructuring, or unit commitment should be employed to coincide with adding this extra load. The total line losses are presented in
Basic condition (without EV loads) | EV with 30% penetration | EV with 50% penetration | EV with 70% penetration | |
---|---|---|---|---|
Ploss | 281.5877 | 298.0568 | 309.5568 | 321.4807 |
Qloss | 187.9595 | 199.3440 | 207.3134 | 215.5924 |
The customer trends in the rate of consumption are not monotonous for different hours of a day. Therefore, there are peak and off-peak amounts in each consumption graph. Some approaches of demand response programs called peak-shaving methods focus on peak reduction. As a well-known recourse, the shiftable method has been applied in many demand response types of research.
In this research, the effects of shifting EV loads from peak times of loads to off-peak times of loads has been analyzed. EV loads have been employed on the 8^{th}, 18^{th}, 30^{th} buses.
It is evident from
Situation | Without EV | With EV | Difference between without EV and with EV situations |
---|---|---|---|
Active losses (non-peak) | 129.6099 | 146.7944 | 17.1845 |
Reactive losses (non-peak) | 86.4199 | 98.3052 | 11.8853 |
Active losses (peak) | 281.5877 | 309.5568 | 27.9791 |
Reactive losses (peak) | 187.9595 | 207.3134 | 19.3539 |
EVs have received significant attention from people and governments during the last few years in particularly, and have been spread all over the world rather quickly as well. So, it is important to consider all of the power grid challenges caused by EVs too. This research has investigated the effect of EVs on voltage stability such as line losses and air pollution rates. As an illustration, the line losses saw about a 3% decrease by relocating the EV’s station. Furthermore, various scenarios have been presented to show the interaction between diverse situations of grid and EV load, and also a possible way to deal with extra demands through simulation. Finally, the effectiveness of the demand response method has been discussed in this study. As a result of demand response, the active and reactive power losses have decreased from 27.9 to 17.1 and from 19.3 to 11.8, respectively.
The voltage of bus
The modified coefficient
Self-admittance
The current between bus
Admittance between bus
Line current
Active power of bus
Power losses of line
Reactive power of bus