The large penetration of intermittent resources, such as solar and wind generation, involves the use of storage systems in order to improve power system operation. Electric Vehicles (EVs) with gridable capability (V2G) can operate as a means for storing energy. This paper proposes an algorithm to be included in a SCADA (Supervisory Control and Data Acquisition) system, which performs an intelligent management of three types of consumers: domestic, commercial and industrial, that includes the joint management of loads and the charge / discharge of EVs batteries. The proposed methodology has been implemented in a SCADA system developed by the authors of this paper - the SCADA House Intelligent Management (SHIM). Any event in the system, such as a Demand Response (DR) event, triggers the use of an optimization algorithm that performs the optimal energy resources scheduling (including loads and EVs), taking into account the priorities of each load defined by the installation users. A case study considering a specific consumer with several loads and EVs is presented in this paper.
The main goal of power systems is to guarantee that the generation meets the
consumers demand, including the domestic, commercial, rural and industrial types of
consumers. The power system should remain in a stable state, matching generation
and demand values. The consideration of consumers’ behavior (participating in
Demand Response events) is one of the distributed energy resources, which have been of
increasing importance [
In this context, the Electric Vehicles (EVs) with gridable capability (V2G) can be
used as a storage unit, storing energy when there is an excess of generation and,
discharging energy when the load is higher than the generation [
The optimization of load consumption and V2Gs use is able to improve the energy
use efficiency, while allowing the system operator to control some loads of
installation. This makes possible the increase of energy resources management flexibility [
The paper deals with the intelligent management of a Domestic Consumer (DC) that adds two V2Gs to the system beyond the normal consumption loads. As these V2Gs are used by house users to travel to their respective workplaces, the effects of V2Gs on the intelligent management of a Commercial Consumer (CC) and an Industrial Consumer (IC) are analyzed. In this way, an optimization methodology is proposed and implemented in a SCADA system considering each type of consumer. This SCADA system considers all loads and V2Gs to perform an intelligent management.
Given the differences between the load curves for each type of consumer, it is important to analyze how the management systems will consider the V2G connection when applied to the three types of consumers at different times of the day.
After the introductory section, Section 2 presents the proposed methodology and Section 3 describes the energy resources considered by the SCADA system developed by the authors of the paper. A case study is presented in Section 4. The final section includes some conclusions. 2
The intelligent management systems used by different consumers have the same basic
structure, being some differences related to the characteristics of each consumer.
Considering the context of participating in DR programs, any of the systems used aims to
optimize the total consumption of the installation, keeping it lower than the
established limit consumption or cutting power indicated by the system operator or by the
installation user [
The SCADA House Intelligent Management (SHIM) has been described in
previous works, and it was only applied to the DC [
The base algorithm, presented in [
Each consumer installation has its load. Otherwise, V2Gs are common resources for the three considered installations of the SCADA system (see Figure 2), i.e., these resources have different connection points (installations) in different periods of the day as V2Gs travels between them. The current state/position of each V2G depends on the period of the day. For example, on Monday at 9 a.m. (peak consumption in the IC), the V2Gs are connected to the IC network and the charge / discharge periods could be managed by the SCADA system focusing on the IC installation resources use optimization. On the other hand, at 8 p.m. (peak consumption for DC and CC) V2Gs are connected to the housing network. The SCADA system is able to manage two V2Gs at the same period in a house (DC). In the case of the CC or the IC, it is prepared to receive one of the V2Gs that belongs to a DC. This is due to house users who give different functions to each V2G presented in Figure 2: 1. Move one user from the house to the industry (30 km) and return (30 km); 2. Move one user from the house to the commerce (15 km) and return (15 km).
The charge/discharge rate considered for both vehicles is 2.3 kW/h and a V2G
battery at full charge has 16 kWh. The V2G have 160 km autonomy [
All end consumers presented in this work have a database that contains a load priority, and the minimum and maximum power of each load and each V2G, depending on the context of the day. The SCADA system optimization analyzes the database and, according to the context, performs an optimal scheduling. The first development in previous work is the inclusion of two V2Gs in the optimization of the DC installation. After that, the methodology was improved in order to consider the CC and the IC, regarding the different characteristics of these consumers. The IC is the building Max Power (W) 180 400 600 700 300 300 with higher consumption. In this way, only one V2G should have low impact in the optimization process.
The present case study considers a Monday in the winter season, with an external temperature of 10ºC. At 9 a.m. and 8 p.m. the three consumers receive the simulated DR event respectively, according to the results presented in Table 2. 4.1
In order to validate the case study, the results were analyzed. At 9 a.m. and 8 p.m. all end consumers receive the information regarding the DR event to cut or reduce loads consumption or to sell the energy stored in the V2G. The optimization of each end consumer installation depends on the availability of the V2G to be considered by the SCADA system. The timeline of the V2G state is presented in Table 2 according the DR event. The blue color means that the V2G is connected to the SCADA system respective, the red color means that the V2G is travelling and the green color represents the DR event participation at 9 a.m. (100 W to DC, 1450 W to CC and 5235 W to IC) and 8 p.m. (400 W to DC, 600 W to CC and 850 W to IC).
At 7 a.m. both V2Gs are connected to the DC SCADA system (with 16000 Wh of energy stored) but consumers do not receive any DR event. At 8 a.m., DC users begin the journey to their workplaces and at 9 a.m. a DR event is announced. At this time, V2G1 is connected to the CC and V2G2 is connected to the IC. This means that the DC will only be able to meet the DR event by cutting or reducing the loads consumption. Other end consumers can also use the discharge capacity of the V2G in the optimization process, according to the priority of the SCADA database.
At 9 a.m. all consumers receive the DR event order to reduce 100W, 1450W and 5235W corresponding to the DC, CC and IC respectively. The V2G1 have 14500 Wh of energy due to the journey of 15 km to the CC and V2G2 have 13000 Wh due to the journey of 30 km to the IC. At 10 a.m. one can verify that the V2G1 storage energy is of 13050 Wh. This means that V2G1 discharges 1450 W over one hour after the DR event announcement. The discharge value corresponds to the reduce power of the DR event and the loads that were being used by the CC were not changed, ensuring consumers’ priorities. Regarding the V2G2, the storage energy is of 10700 Wh. This means that V2G2 discharges 2300W over one hour after the DR event announcement. The discharge value corresponds to a portion of the total reduce power of the DR event (5235 W). In this case, the IC SCADA system also needed to reduce the consumption in the lower loads’ priority in order to fully meet the DR event requirements.
At 6 p.m. one can verify that any consumer of the SCADA system have V2Gs connected, because the V2G users begin the return journey, from the workplace to their houses, which will reduce 1500 Wh in V2G1, and 3000 Wh in V2G2. At 8 p.m. all consumers receive the DR event order to reduce 400W, 600W and 850W corresponding to the DC, CC and IC respectively. V2G1 has 11550 Wh of energy and V2G2 has 7700 Wh of energy.
At 9 p.m. one can verify that V2G1 energy is of 11150 Wh. Thus, V2G1 discharges 400W over one hour after the DR event announcement. The discharge value corresponds to the reduce power of DR event and the loads that were used by DC were not changed, ensuring consumers’ priorities. Regarding V2G2, the energy is 7700 Wh, maintaining therefore the initial energy. In this case, the CC and IC see the consumption reduced in the lower loads’ priorities in order to fully meet the DR event, 600W and 850W respectively. 4.2
Tables 3 and 4 present the results of the optimization process to validate the methodology proposed in Section 2. Table 3 shows the priority of each load and of each V2G to charge (Ch) or discharge (Dch), when end consumers meet the first DR event at 9 a.m.. Table 4 summarizes the optimization results at 8 p.m. (second DR event). The coloured cells represent the resources which were subjected to changes.
The SCADA management system selects the loads or V2G mode (charge or discharge) according each priority. For example in first DR event to CC, the resource with low priority is 20 (V2G1 discharge) and the resource with higher priority is 1 (Induction motor #2). The priorities are predefined by the installation users.
In the first DR event, at 9 a.m., the DC fulfilled the reduce power (100W) by turning off the incandescent lamp #2 and reducing the consumption of the induction motor #2 (loads with lower priority). The CC fulfilled the DR event requirement (1450W) through the V2G1 discharge, keeping the same load consumption. The IC beyond the V2G2 discharge, also turned off the incandescent lamp#1 and the heat accumulator #2, and reduced the consumption of the induction motor #2 to guarantee the required reduced power of DR event (5235W). In the second DR event at 8 p.m., the DC fulfilled the reduce power (400W) with V2G1 discharge, keeping the same load consumption. The CC fulfilled the DR event requirement (600W) through the loads with lower priority; the same happened in the IC (850W). 5
This paper presents a case study considering a SCADA system to manage and optimize the consumption of all energy resources of the DC, CC and IC consumers. The case study is discussed and analyzed applying the methodology to the CC and IC in a particular context, and verifying the usefulness of V2Gs in their management systems. The results of using the proposed methodology regarding working days or weekends specificities, which require some distinct characteristics, have been addressed and will be reported in near future work.
In the present work, one can verify that V2G has direct participation and impact in the consumption optimization. The SCADA system of any consumer is provided with the priorities defined by the installation users to each load and each V2G according to the operation context. The SCADA database allows to know the user’s needs in real time in order to guarantee the fulfilment of the DR event requirements.
One V2G may have more influence in the DC optimization than in the IC optimization, as the IC is a consumer with higher energy requirements. In this way, one V2G may have little impact in IC resources use optimization, but if we are dealing with a considerable number of V2Gs, this impact must be adequately analyzed. This means that the optimization decisions depend directly on the consumers’ energy needs, on the number of V2Gs considered and on the type of end consumer. The benefits of using the proposed SCADA system can be summarized as follows: Creation of a system with its own capacity for decision in real time to support the grid operator with energy management capability; The methodology development can be adapted for any type of end consumer and amount of energy resources; Each SCADA system is able to be adapted to the current system conditions over the day with or without of V2G; The inclusion of V2G in the SCADA system makes possible to ensure the end consumer comfort through the V2G batteries energy discharge.
This work is supported by FEDER Funds through COMPETE program and by National Funds through FCT under the projects FCOMP-01-0124-FEDER: PEst