KR20230017726A - System of managing chargers for electric vehicles - Google Patents

Abstract

The present invention relates to a system for managing an electric automobile charger installed in a parking lot. The electric automobile charger management system may comprise: a plurality of slow chargers constituting a medium voltage direct current (MVDC) system; a solar panel converter; an energy storage device converter; an inverters and DC grid switch; and a management server which controls the same. Provided is the electric automobile charger management system capable of efficiently managing charging and discharging of an electric automobile within a range of a power supplied to a building.

Description

Electric vehicle charger management system {System of managing chargers for electric vehicles}

The present invention relates to a system for managing an electric vehicle charger installed in a parking lot.

At the time when electric vehicles (EVs) are being activated, electric power demand for infrastructure construction and rapid charging for charging and discharging of electric vehicles is rapidly increasing. However, the number of EV chargers installed in existing apartments or buildings is very small compared to the number of parking spaces. In addition, since there are fewer rapid chargers than slow chargers, the possibility of charging problems increases as the number of electric vehicles increases.

With electric vehicles on the rise, the majority of installed EV chargers are fast chargers. It is very rare to install a large number of quick chargers in the same parking lot due to installation and maintenance costs and problems with power consumption. Even if most of the fast chargers currently in operation are used, it takes at least 30 minutes to charge, and waiting time may occur due to other vehicles being charged. In addition, in the case of fast charging, only up to 80% of the battery capacity is charged, and only in the case of slow charging, 100% charging is possible.

The lack of fast chargers in apartments or buildings is causing problems in the spread of electric vehicles. The amount of power that the power system supplies to a particular building is fixed. When the electric vehicle is charged, power usage increases rapidly and exceeds the supplied power, resulting in a power outage or reduced charging efficiency. For example, if the contracted power of the building is 2000kVA and the current power consumption of the building is 1200kVA, only one 500kW class fast charger can be used. If two 500kW class rapid chargers are used, a power outage accident may occur due to overheating of the transformer and activation of the building's circuit breaker.

It is intended to provide an electric vehicle charger management system capable of efficiently managing charging and discharging of an electric vehicle within the range of power supplied to a building.

According to one aspect of the present invention, an electric vehicle charger management system for simultaneously charging a plurality of electric vehicles while suppressing a peak of load power supplied from a power system to a building in which a parking lot is installed is provided. The electric vehicle charger management system converts a plurality of slow chargers disposed in a parking lot, a solar panel converter that converts the output power of a solar panel, and converts the output power of the solar panel converter and stores it in an energy storage device, and stores the energy. At least one of an energy storage device converter that converts and outputs power stored in a device, an electric vehicle that converts AC power supplied from a power system into direct current power, and is connected to the slow charger, the solar panel converter, and the energy storage device converter. In a medium voltage direct current (MVDC) system composed of an inverter, the solar panel converter, the energy storage device converter, the inverter, and the plurality of slow chargers that convert the output direct current power into alternating current power and supply it to the building, A DC system switch that electrically connects a power source supplying DC power and a load receiving DC power, and a DC system switch that monitors the load power and, when the load power is below the peak, one of the solar panel converter, the energy storage device converter, and the inverter Alternatively, both may include a management server that supplies DC power to the slow charger and controls AC power to be supplied to the building when the load power exceeds a peak.

In one embodiment, the management server monitors the load power, and the DC power control unit selects the power and the load in the MVDC system, the solar panel converter, the energy storage device converter, and the DC power among the inverters. It may include a power conversion device control unit that operates a power conversion device selected as a power source by the control unit, a transmission line management unit that monitors the transmission line of the MVDC system to detect an abnormal state, and a charger control unit that controls the operation of the slow charger. .

In an embodiment, the DC power control unit may select an electric vehicle to recover power by using a charging tendency of the electric vehicle connected to the slow charger.

In one embodiment, the DC system switch may include an insulation resistance measuring unit for measuring insulation resistance using a leakage current flowing from a transmission line of the MVDC system to ground in a live state.

In one embodiment, one end of the insulation resistance measurement unit is electrically connected to the first transmission line, the other end is grounded to the ground, and measures a first leakage current flowing from the first transmission line toward the ground during a first period. A first leakage current measuring unit, one end of which is electrically connected to a second transmission line, the other end of which is grounded to ground, and a second leakage current flowing from the second transmission line toward the ground during a second period that does not overlap with the first period. 2 a second leakage current measurement unit for measuring leakage current, the first leakage current passing through the first leakage current measurement unit during the first period, and the second leakage current measuring the second leakage current during the second period; An insulation resistance measurement control unit controlling the first leakage current measurement unit and the second leakage current measurement unit to pass through the measurement unit may be included.

In one embodiment, the first leakage current measuring unit measures a first leakage current limiting resistor connected in series between the first transmission line and the ground and a first leakage current passing through the first leakage current limiting resistor. A first ammeter and a first switch turned on and off by the control unit to control the flow of the first leakage current, wherein the second leakage current measurement unit includes a second leakage current measuring unit connected in series between the second transmission line and the ground. A leakage current limiting resistor, a second ammeter for measuring the second leakage current passing through the second leakage current limiting resistor, and a second switch that is turned on and off by the control unit to control the flow of the second leakage current. .

In an embodiment, resistance values of the first leakage current limiting resistor and the second leakage current limiting resistor may be smaller than insulation resistances of the first transmission line and the second transmission line.

In one embodiment, the PV converter may include an insulation resistance measuring unit for measuring insulation resistance using a leakage current flowing from a transmission line connected to a solar panel to the ground in a live state of the DC system switch.

In one embodiment, the plurality of slow chargers may be installed for each parking surface of the parking lot.

According to the present invention, it is possible to efficiently manage charging and discharging of an electric vehicle within a range of power supplied to a building.

Hereinafter, the present invention will be described with reference to embodiments shown in the accompanying drawings. For ease of understanding, like reference numerals have been assigned to like elements throughout the accompanying drawings. The configurations shown in the accompanying drawings are only exemplary implementations to explain the present invention, and are not intended to limit the scope of the present invention thereto. In particular, in the accompanying drawings, in order to help understanding of the invention, some components are somewhat exaggerated.
1 is a diagram showing an electric vehicle charger management system by way of example.
2 is a diagram functionally illustrating the configuration of an electric vehicle charger management system.
3 is a diagram illustrating power control performed by a management server of an electric vehicle charger management system by way of example.
4 is a view showing an example of a slow charger installed in a parking lot.
5 is a diagram showing an equivalent circuit of a transmission line connecting a power source and a load by way of example.
6 is a diagram showing the configuration of a device for measuring insulation resistance in a live wire state by way of example.
7 is a diagram showing an operation of a device for measuring insulation resistance in a live wire state by way of example.
8 is a diagram illustrating a process of measuring an insulation resistance of one of a pair of transmission lines connecting a PV and a PV converter by way of example.
9 is a diagram illustrating a process of measuring an insulation resistance of the other of a pair of transmission lines connecting a PV and a PV converter by way of example.

Since the present invention can have various changes and various embodiments, specific embodiments are illustrated in the drawings and will be described in detail through detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In particular, the functions, features, and embodiments described below with reference to the accompanying drawings may be implemented alone or in combination with other embodiments. Therefore, it should be noted that the scope of the present invention is not limited only to the forms shown in the accompanying drawings.

It is understood that when a component is referred to as being "fixed" or "fastened" to another component, it may be directly fixed or fastened to the other component, but other components may exist in the middle. It should be. On the other hand, when a component is referred to as “directly fixed” or “directly fastened” to another component, it should be understood that no other component exists in the middle.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another.

Terms used in this specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "include" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

In addition, the components of the embodiments described with reference to each drawing are not limitedly applied only to the corresponding embodiment, and may be implemented to be included in other embodiments within the scope of maintaining the technical spirit of the present invention, and also separate Even if the description is omitted, it is natural that a plurality of embodiments may be re-implemented as an integrated embodiment.

In addition, in the description with reference to the accompanying drawings, the same or related reference numerals are given to the same components regardless of reference numerals, and overlapping descriptions thereof will be omitted. In describing the present invention, if it is determined that a detailed description of related known technologies may unnecessarily obscure the subject matter of the present invention, the detailed description will be omitted.

Throughout the appended drawings, the same or similar elements are referred to using like reference numerals.

1 is a diagram showing an electric vehicle charger management system by way of example.

From an energy management point of view, it is known that the lifestyle charging method is more efficient for electric vehicles than the conventional charging method for gasoline vehicles visiting gas stations. Therefore, rather than the current electric vehicle charging infrastructure operated with a relatively small number of fast chargers compared to the number of parking spaces, the new electric vehicle charging infrastructure that manages the same number of slow chargers as the number of parking spaces through an energy management system is suitable for residential use such as apartments. It is advantageous to supply buildings with large parking lots, such as commercial buildings such as buildings and shopping malls.

The present invention introduces a grid-connected DC method to a slow charger and greatly reduces the size of the charger by applying a next-generation power semiconductor. As a result, the stability of the slow charger is increased, and the construction cost required for installing the slow charger per parking lot is reduced, so that an electric vehicle charger management system can be built cost-effectively.

For example, if all 5 kW slow chargers are installed in a large parking lot with 200 cars, a large-capacity energy supply of up to about 1,000 kW may be required. For this, a central inverter and grid management are required, and the introduction of energy storage devices (ESS) and solar panels (PV) for power supply stability has become necessary. The electric vehicle charger management system is an energy management solution for energy-efficient management of slow chargers.

The electric vehicle charger management system includes a management server 100, an inverter 200, an energy storage device converter (300; hereinafter ESS converter), a solar panel converter (400; hereinafter PV converter), a load power measuring device 500, a DC A system switch 600 and a slow charger 700 may be included. Additionally or alternatively, the electric vehicle charger management system may further include an energy storage device 350 (hereinafter referred to as ESS) and/or a solar panel 450 (hereinafter referred to as PV).

The inverter 200, the ESS converter 300, the PV converter 400, the DC system switch 600, and the plurality of slow chargers 700 of the electric vehicle charger management system constitute a medium voltage direct current (MVDC) system. Although it depends on the number of parking spaces, the area of the parking lot where the slow charger 700 is installed is mostly wide. Therefore, considering the transmission distance, efficiency, and simultaneous use of renewable energy, a DC system that transmits with a DC voltage in the range of about 1.5 kV to about 100 kV rather than an AC system that transmits with a commercial AC voltage, for example, AC 220 V. MVDC is suitable. The MVDC system not only receives power from the power system, but also can supply power to the power system or to building loads connected to the power system.

The management server 100 uses ESS power and/or solar power to simultaneously charge a plurality of electric vehicles while suppressing peak load power. Here, the load power includes AC power supplied to the load of the building in which the parking lot is installed and the MVDC system. That is, the management server 100 can supply power required for the slow charger 700 from one or more of the power system, the ESS 350, and the PV 450 without exceeding the contracted power of the building in which the electric vehicle charger management system is installed. can The management server 100 is connected to an inverter 200, an ESS converter 300, a PV converter 400, a load power measuring device 500, a DC system switch 600, and a plurality of slow chargers 700 through a communication line. can communicate The configuration and operation of the management server 100 will be described in detail with reference to FIGS. 2 and 3 below.

Under the control of the management server 100, the inverter 200 is a DC-AC power conversion device that converts AC power supplied from the power grid into first DC power. Meanwhile, the inverter 200 converts first DC power supplied from one or more of the electric vehicles connected to the ESS converter 300, the PV converter 400, and the slow charger 700 into AC power and supplies it to the load. The first DC power may be MVDC class.

The ESS converter 300 is a DC-DC power converter that operates under the control of the management server 100 . The ESS converter 300 stores DC power supplied from at least one of the inverter 200 and the PV converter 400 in the ESS 350, converts the stored power into DC power, and outputs the converted power. DC power output from the ESS converter 300 may be supplied to one or both of the building load and the slow charger 700 via the inverter 200 .

The PV converter 400 is a DC-DC power converter that operates under the control of the management server 100 . The PV converter 400 converts the output power of the PV 450 into DC power and outputs it. DC power output from the PV converter 400 may be supplied to one or more of the building load via the inverter 200, the ESS 450 via the ESS converter 300, and the slow charger 700.

The load power measurement device 500 measures load power. The load power measured in real time is provided to the management server 100 . The management server 100 operates the inverter 200, the ESS converter 300, and the PV converter 400 so that the load power does not exceed the contract power.

The DC system switch 600 operates under the control of the management server 100 to select power to supply DC power and loads to be supplied. For example, the DC system switch 600 connects the MVDC transmission line between the inverter 200, ESS converter 300, and PV converter 400 operating as power in the MVDC system and the slow charger 700 operating as a load. can be connected or disconnected. On the other hand, the DC system switch 600 connects the MVDC transmission line between the electric vehicle connected to the ESS converter 300, the PV converter 400, and the slow charger 700 operating as a power source and the inverter 200 operating as a load, or can be unlocked

The slow charger 700 operates under the control of the management server 100 to convert the first DC power supplied through the MVDC transmission line into third DC power and supply it to the electric vehicle. Meanwhile, the slow charger 700 may convert third DC power stored in the electric vehicle into first DC power and provide the converted DC power to the inverter 200 . One or a pair of slow chargers 700 are installed per parking area.

2 is a diagram functionally illustrating the configuration of an electric vehicle charger management system.

Referring to FIG. 2 , the management server 100 may include a DC power controller 110, a power converter controller 120, a transmission line manager 130, a charger controller 140, and a communication unit 150.

The DC power controller 110 basically monitors load power, and may additionally or selectively monitor power stored in the ESS 350 and output power of the PV 450 . According to the monitoring result, the DC power control unit 110 drives the DC system switch 600 to select a power source and a load to perform power control for peak suppression.

Additionally or alternatively, the DC power controller 110 may also monitor power stored in the electric vehicle connected to the slow charger 700 through the charger controller 140 . A battery charge rate of an electric vehicle may be maintained at a certain level, for example, 100%. If the charging rate becomes below a certain level due to factors such as power supply of the electric vehicle or battery condition deterioration, charging may be initiated even without a user's request.

If it is difficult to control the peak power only with the second DC power stored in the ESS 350 and the output power of the PV 450, the power stored in the electric vehicle may also be supplied to the inverter 200. As an embodiment, the DC power control unit 110 may recover power by selecting an electric vehicle in a fully charged state from among electric vehicles connected to the slow charger 700 through the charger control unit 140 . In another embodiment, referring to the charging tendency of the electric vehicle including the connection time with the slow charger 700, the disconnection time, and the amount of power supplied, the DC power control unit 110 determines the electricity to recover power through the charger control unit 140. You can choose your car. For example, an electric vehicle having a relatively short separation time and a relatively small amount of power supplied has a high probability of mainly driving a short distance. In this case, even if the charging rate is not high, the possibility of trouble in driving is relatively low, and thus the electric vehicle to recover power may be selected. Conversely, an electric vehicle having a charging tendency with a relatively long separation time and a relatively large amount of supplied power has a high probability of mainly traveling long distances. Therefore, electric vehicles with this charging tendency may not be selected.

The power converter controller 120 operates the inverter 200, the ESS converter 300, and/or the PV converter 400 selected as power by the DC power controller 110. That is, the power converter control unit 120 generates a PWM control signal for PWM (Pulse width modulation) switching control of the inverter and converter and transmits it to the inverter 200, the ESS converter 300 and / or the PV converter 400 do.

Meanwhile, the power converter control unit 120 monitors inputs and outputs of the inverter 200, the ESS converter 300, and the PV converter 400 to detect abnormal operation. The power converter controller 120 stops the inverter 200, the ESS converter 300, or the PV converter 400 in which an abnormal operation is detected.

The transmission line management unit 130 detects an abnormal state by monitoring the transmission lines constituting the MVDC system. In particular, in a parking lot where the slow charger 700 is installed, an MVDC transmission line is buried in the parking lot floor, and a transmission line between the PV 450 and the PV converter 400 may also be buried in the ground. Therefore, when a ground fault occurs due to aging of the wire sheath, not only significant power loss but also the possibility of an accident increases. The transmission line management unit 130 detects the occurrence of a ground fault using the leakage current measured in the MVDC transmission line and the insulation resistance calculated therefrom, and stops power transmission to the slow charger 700 when a ground fault is detected.

The charger controller 140 controls the operation of the slow charger 700 . The charger control unit 140 operates the approved slow charger 700 to charge the electric vehicle. Meanwhile, the charger controller 140 may operate the slow charger 700 to recover power from the electric vehicle. Additionally or alternatively, the charger control unit 140 may generate a charging history for each electric vehicle. The charging history may include connection time, disconnection time, amount of power supplied, amount of power recovered, and charging time. The charging history is notified to the user and used to calculate the charging cost. Meanwhile, a charging tendency for each electric vehicle may be derived from the charging history. The connection time is calculated by subtracting the connection time from the separation time, and the separation time may be calculated by subtracting the previous separation time from the connection time.

The communication unit 150 is responsible for communication between the management server 100 and other components of the electric vehicle charger management system. The communication unit 150 may operate in a wired or wireless communication method.

The PV converter 400 may include a PWM driver 410, a power semiconductor switch 420, and an insulation resistance measuring unit 430. Since the functional configuration of the inverter 200 and the ESS converter 300 is similar to that of the PV converter 400, the PV converter 400 will be mainly described.

The PWM driver 410 generates a PWM signal for driving the plurality of power semiconductor switches 220 . The power semiconductor switch 420 may be an insulated-gate bipolar transistor (IGBT), a silicon carbide metal-oxide-semiconductor field effect transistor (SiC MOSFET), a GaN MOSFET, or a Ga2O3 MOSFET supporting high voltage-high current. The DC voltage on the output side may be boosted or stepped down by the power semiconductor switch 420 . Meanwhile, in the case of the inverter 200 , AC power may be converted into DC power or DC power may be converted into AC power by the power semiconductor switch 420 .

The insulation resistance measurement unit 430 measures a leakage current of a transmission line between the PV 450 and the PV converter 400 or a transmission line between the DC system switch 600 and the PV converter 400 to detect the occurrence of a ground fault. In particular, the insulation resistance measurement unit 430 may detect the occurrence of a ground fault when the transmission line is in an active state. Hereinafter, it will be described in detail with reference to FIGS. 5 to 9 .

The DC system switch 600 may include a connection controller 610, a plurality of relays 620, and an insulation resistance measurement unit 630. One end of each of the plurality of relays 620 is connected to a transmission line connected to the inverter 200, ESS converter 300, and PV converter 400, and the other end is connected to a transmission line connected to the slow charger 700. The connection control unit 610 drives a plurality of relays 620 by the DC power control unit 110 to electrically connect one or more of the inverter 200, the ESS converter 300, and the PV converter 400 and the slow charger 700 to each other. connect to

The insulation resistance measurement unit 630 measures the leakage current of the transmission line between the DC system switch 600 and the slow charger 700 to detect the occurrence of a ground fault. In particular, the insulation resistance measurement unit 630 may detect the occurrence of a ground fault when the transmission line is in an active state. Hereinafter, it will be described in detail with reference to FIGS. 5 to 9 .

The slow charger 700 may include a charge/discharge controller 710, a DC-DC converter 720, and a watt-hour meter 730. The charge/discharge control unit 710 detects connection and disconnection of the electric vehicle. When the electric vehicle is connected and power charging is approved, the charge/discharge control unit 710 may supply power to the electric vehicle or recover power from the electric vehicle by driving the DC-DC converter 720 . The watt-hour meter 730 measures power supplied to or recovered from the electric vehicle. The measured amount of power supplied and recovered power is transmitted to the charger controller 140 by the charge/discharge controller 710 .

3 is a diagram illustrating power control performed by a management server of an electric vehicle charger management system by way of example.

In order to simultaneously charge a plurality of electric vehicles while suppressing peak load power, the electric vehicle charger management system measures the load power.

In step 1, no electric vehicles are being charged, the PV 450 is generating power, and the load power is also maintained below peak. Thus, the power grid supplies power to building loads, but not to the MVDC grid. Since the inverter 200 does not operate and no power is supplied to the slow charger 700, the power generated by the PV 450 is used to charge the ESS 350.

In step 2, since no electric vehicle is being charged and the PV 450 is generating power, but the load power exceeds the peak, power control for peak suppression is initiated. The power produced by the PV 450 and the power stored in the ESS 350 are converted into AC power by the inverter 200 and transmitted to building loads.

In step 3, there is an electric vehicle charging, the PV 450 is generating power, and the load power is also maintained below peak. Thus, the power grid supplies power to building loads, but not to the MVDC grid. Since the inverter 200 does not operate and there is power supplied to the slow charger 700, the power generated by the PV 450 is used to charge the electric vehicle and the ESS 350.

In step 4, there is an electric vehicle being charged, and the amount of power generated by the PV 450 has decreased, but the load power remains below peak. Thus, the power grid supplies power to building loads, but not to the MVDC grid. Since the inverter 200 does not operate and the power supplied to the slow charger 700 has increased from step 3, the power generated by the PV 450 and the power stored in the ESS 350 are used to charge the electric vehicle.

In step 5, there is an electric vehicle being charged, and the amount of power generated by the PV 450 has greatly decreased, but the load power is maintained below the peak. Thus, the power grid supplies power to building loads and the MVDC grid. The inverter 200 operates to convert AC power to DC power. Since the power supplied to the slow charger 700 is higher than in step 4, the power converted by the inverter 200, the power produced by the PV 450, and the power stored in the ESS 350 are used to charge the electric vehicle. .

At step 6, the MVDC grid supplies power to the building loads, so that the power grid is in a zero energy state that does not supply power to the building loads. Although the PV 450 is stopped, power stored in the electric vehicle and the ESS 450 is recovered, converted into AC power by the inverter 200, and transmitted to a building load.

4 is a view showing an example of a slow charger installed in a parking lot.

The slow charger 700 receives DC power from a power source through transmission lines 10a and 10b buried in the parking lot floor. The slow charger 700 may be implemented as a parking stopper installed on each parking surface. Since the parking stoppers are installed in pairs on each parking surface, the charging socket is disposed on the side close to the parking surface boundary among both sides of the parking stopper so that the user can easily connect the charging cable 740.

5 is a diagram showing an equivalent circuit of a transmission line connecting a power source and a load by way of example.

An electric wire consists of a conductor through which electricity flows and an insulator surrounding it. If the wire sheath, which is an insulator, is aged or damaged, leakage current may flow through the corresponding part. Electric shock or fire may occur due to leakage current.

Leakage current of a live wire can be divided into resistive leakage current and capacitive leakage current. Leakage current can be measured using a leakage current due to an impedance component existing between a wire and the ground using a frequency higher than a commercial frequency. However, in order to use this method, a complicated measurement device is required, and manufacturing and installation costs are very high.

Referring to (a) of FIG. 5 , the transmission line 10 is composed of a conductor 11 made of a metal such as copper through which electricity flows, and an insulator 12 surrounding the conductor 12 . The insulator 12 is mostly formed of a plastic material and may function as a dielectric. For this reason, the transmission line 10 buried in the ground can be expressed as an equivalent circuit composed of the conductor 11 and the capacitor 20. Leakage current 30 flows through the insulator 12 to ground. Since the leakage current 30 increases as the voltage increases, the thickness and material of the insulator 12 must be appropriately set to minimize the leakage current 30 . When the transmission line 10 is normal, the leakage current 30 mostly flows in several uA to several mA, but when the insulation is broken or a ground fault occurs, the leakage current 30 appears high, and a human electric shock accident or leakage current 30 may cause an electrical fire due to

5(b) shows a loop of leakage current 31 generated in a pair of transmission lines 10a and 10b in a normal state. The first and second transmission lines 10a and 10b transfer power between the power source and the slow charger 700 . Here, the power source is one or more of the inverter 200, the ESS converter 300, and the PV converter 400. That is, the first transmission line 10a is a path of current flowing from the power source connected by the DC system switch 600 to the slow charger 700, and the second transmission line 10b is a current path from the slow charger 700 to the power source. is the return path. A voltage V of power is applied to left ends of the first and second transmission lines 10a and 10b. The leakage current 31 generated in the normal state flows from the first transmission line 10a to the ground through the capacitor-insulation resistor 20 closest to the power supply side, and the capacitor-insulation resistor 20' closest to the slow charger 700. ) may have a loop returning to the second transmission line 10b again. That is, in a normal state, the amount of current passing through the capacitor-insulation resistor 20 is not large, and since the section passing through the ground is long, the amount of current flowing through the capacitor-insulation resistor 20' is also very small.

5(c) shows paths of leakage current generated from a pair of transmission lines in a ground fault state. Similarly to (b), the first and second transmission lines 10a and 10b transfer power between the power source and the slow charger 700, and power is provided at left ends of the first and second transmission lines 10a and 10b. A voltage V is applied by Assuming that a ground fault occurs in the second transmission line 10b, the leakage current 32 flows from the first transmission line 10a to the ground through the capacitor-insulation resistor 20 closest to the power supply side, and the ground fault point ( 21) may have a loop returning to the second transmission line 10b. That is, in the ground fault state, since leakage current returns from the ground fault point 21 to the second transmission line 10b, the amount of current introduced through the ground fault point 21 may be very large.

6 is a diagram showing the configuration of an insulation resistance measurement unit for measuring insulation resistance in a live wire state by way of example.

Referring to FIG. 6, the insulation resistance measurement unit 800 for measuring insulation resistance in a live wire state includes a first leakage current measurement unit 810 electrically connected to the first transmission line 10a and a second transmission line 10b. a second leakage current measurement unit 820 electrically connected to , and an insulation resistance measurement control unit 830 that controls operations of the first leakage current measurement unit 810 and the second leakage current measurement unit 820 to measure leakage current. ) may be included.

One end of the first leakage current measuring unit 810 is electrically connected to the conductor 11 of the first transmission line 10a, and the other end is grounded to ground. The first leakage current measurement unit 810 includes a first leakage current limiting resistor 811, a first ammeter 812 for measuring a first leakage current that has passed through the first leakage current limiting resistor 811, and a control unit 830. It may include a first switch 813 that is turned on and off by , and controls the flow of the first leakage current. The first leakage current limiting resistor 811, the first ammeter 812, and the first switch 813 may be connected in series between the first transmission line 10a and the ground.

One end of the second leakage current measuring unit 820 is electrically connected to the conductor 11 of the second transmission line 10b, and the other end is grounded to ground. The second leakage current measuring unit 820 includes a second leakage current limiting resistor 821, a second ammeter 822 for measuring a second leakage current passing through the second leakage current limiting resistor 821, and a control unit 830. It may include a second switch 823 that is turned on and off by , and controls the flow of the second leakage current. The second leakage current limiting resistor 821, the second ammeter 822, and the second switch 823 may be connected in series between the second transmission line 10b and the ground.

The first leakage current limiting resistor 811 and the second leakage current limiting resistor 821 measure the first leakage current after a ground fault occurs in the first transmission line 10a and/or the second transmission line 10b. and serves to limit the second leakage current from increasing. Here, the first leakage current limiting resistor 811 and the second leakage current limiting resistor 821 may be smaller than the insulation resistance measured in the normal state of the first transmission line 10a and the second transmission line 10b.

The insulation resistance measurement controller 830 may functionally include a switching controller 831, a leakage current measurement unit 832, and an insulation resistance calculator 833. The switching control unit 831 may turn on the first switch 813 and the second switch 823 alternately. The leakage current measuring unit 832 may read measured values from the first ammeter 812 and the second ammeter 822 . The insulation resistance calculator 833 may calculate the insulation resistance using the measured leakage current and the normal current flowing between the power source to which the first voltage V1 is applied and the load to which the second voltage V2 is applied. Operations of the first leakage current measurement unit 810 and the second leakage current measurement unit 820 by the insulation resistance measurement control unit 830 will be described in detail with reference to FIG. 7 .

7 is a diagram showing the operation of an insulation resistance measuring unit for measuring insulation resistance in a live wire state by way of example.

(a) and (b) of FIG. 7 show a loop of the first leakage current 40 and a loop of the second leakage current 41 when the insulation resistance measuring unit 800 operates normally, and (c) shows When the insulation resistance measuring units 430 and 630 operate abnormally, a leakage current loop is shown.

The switching controller 831 alternately turns on the first switch 813 and the second switch 823 so that the first leakage current and the second leakage current flow without overlapping.

Referring to (a) of FIG. 7 , during the first period in which the first switch 813 is turned on, the second switch 823 is turned off and the first leakage current 40 escaped from the first transmission line 10a can be measured. A portion of the normal current flowing into the first transmission line 10a from the power supply side to which the first voltage V1 is applied between the first transmission line 10a and the second transmission line 10b is measured by the first leakage current measuring unit 810 can flow to the ground through The first leakage current 40 flowing into the ground is measured at a point other than the second leakage current measurement unit 820, for example, between the first transmission line 10a and the second transmission line 10b at the second voltage V2. It can return to the second transmission line 10b at a point close to the applied slow charger 700 . That is, the first leakage current measurement unit 810 may operate as a controlled ground point during the first period and measure the amount of current of the first leakage current 40 varied by the second transmission line 10b.

Insulation resistance Rx can be calculated as follows.

Rx = V1/I1 - R1

Here, V1 is the potential difference across the power supply and the potential difference is 500 V, I1 is the first leakage current and its measured value is 100 uA, and R1 is the first leakage current limiting resistor and its resistance value is 100 kΩ. The first leakage current 40 is determined by the insulation resistance of the second transmission line 10b, and the calculated insulation resistance of the second transmission line 10b is 4,900 kΩ.

Similarly, referring to (b) of FIG. 7 , during the second period in which the second switch 823 is turned on, the first switch 813 is turned off and the second leakage current flows into the second transmission line 10b. can be measured. A portion of the normal current flowing into the first transmission line 10a from the power supply side to which the first voltage V1 is applied between the first transmission line 10a and the second transmission line 10b is measured by the first leakage current measuring unit 810 It may flow to ground at a point other than , for example, a point close to the slow charger 700 to which the second voltage V2 is applied between the first transmission line 10a and the second transmission line 10b. The second leakage current 41 flowing into the ground may return to the second transmission line 10b through the second leakage current measuring unit 820 . That is, the second leakage current measurement unit 820 may operate as a controlled ground fault point during the second period and measure the amount of current of the second leakage current 41 varied by the first transmission line 10a.

Meanwhile, referring to (c) of FIG. 7 , a leakage current loop when the first switch 813 and the second switch 823 are simultaneously turned on is shown. When both the first switch 813 and the second switch 823 are turned on, a ground fault has occurred in both the first transmission line 10a and the second transmission line 10b. Therefore, a very large leakage current flows into the ground through the first leakage current measurement unit 810 and returns to the second transmission line 10b through the second leakage current measurement unit 820. Therefore, the control unit 830 must turn on the first switch 813 and the second switch 823 alternately.

8 is a diagram illustrating a process of measuring an insulation resistance of one of a pair of transmission lines connecting a PV and a PV converter by way of example.

Referring to (a) of FIG. 8 , first and second transmission lines 10a and 10b transfer power between the grounded PV 450 and the PV converter 450 . A leakage current loop when the PV 450 is not grounded may be substantially the same as that of FIG. 7(a). When the first leakage current measurement unit 810 is turned on and the second leakage current measurement unit 820 is turned off in a normal state in which no ground fault occurs, the first leakage current 50 is measured by the first leakage current measurement unit 810 You can have a loop from , through ground, and back through the ground of power supply 200.

A portion of the normal current flowing into the first transmission line 10a from the PV 450 to which the first voltage V1 is applied between the first transmission line 10a and the second transmission line 10b is measured by the first leakage current measuring unit. It can flow to the ground through (810). The first leakage current 50 flowing into the ground is a point other than the second leakage current measuring unit 820, for example, between the first transmission line 10a and the second transmission line 10b, the second voltage V2 At a point close to the applied PV converter 400, it may return to the second transmission line 10b. That is, the first leakage current measurement unit 810 may operate as a controlled ground point during the first period and measure the amount of current of the first leakage current 50 varied by the second transmission line 10b.

Referring to (b) of FIG. 8 , when a ground fault occurs in the second transmission line 10b, the first leakage current 51 flowing through the first leakage current measuring unit 810 flows from the ground fault point 21 to the second It returns to the transmission line 10b. The current amount of the first leakage current 51 may be several to hundreds of times greater than the current amount of the first leakage current 50 .

Referring to (c) of FIG. 8 , when a ground fault occurs in the first transmission line 10c, a leakage current 52 is generated at the ground fault point 21. Since most of the current leaks through the point 21, the current amount of the first leakage current that can be measured by the first leakage current measuring unit 810 may be very small or non-existent. That is, the first leakage current measuring unit 810 cannot detect a ground fault occurring in the first transmission line 10a.

9 is a diagram illustrating a process of measuring an insulation resistance of the other of a pair of transmission lines connecting a PV and a PV converter by way of example.

Referring to (a) of FIG. 9 , first and second transmission lines 10a and 10b transfer power between the PV 450 and the PV converter 400 . When the first leakage current measurement unit 810 is turned off and the second leakage current measurement unit 820 is turned on in a normal state in which no ground fault occurs, the second leakage current 60 flowing from the first transmission line 10a to the ground ) may have a loop returning to the second transmission line 10b through the second leakage current measuring unit 810 .

A portion of the normal current flowing into the first transmission line 10a from the PV 450 to which the first voltage V1 is applied between the first transmission line 10a and the second transmission line 10b is a capacitor-insulation resistor 20 ) through which it can flow to the ground. The second leakage current 60 flowing into the ground may return to the second transmission line 10b through the second leakage current measuring unit 820 . That is, the second leakage current measuring unit 820 may operate as a controlled ground fault point during the second period and measure the amount of current of the second leakage current 60 varied by the first transmission line 10a.

Referring to (b) of FIG. 9 , when a ground fault occurs in the first transmission line 10b, the second leakage current 61 flowing through the second leakage current measurement unit 820 flows from the ground fault point 21 to the ground. flows in The current amount of the second leakage current 61 may be several to hundreds of times greater than the current amount of the second leakage current 60 .

The above description of the present invention is for illustrative purposes, and those skilled in the art can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, the embodiments described above should be understood as illustrative in all respects and not limiting. In particular, the features of the present invention described with reference to the drawings are not limited to the structures shown in the specific drawings, and may be implemented independently or in combination with other features.

The scope of the present invention is indicated by the following claims rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts thereof should be construed as being included in the scope of the present invention. .

Claims (8)

In the electric vehicle charger management system for simultaneously charging a plurality of electric vehicles while suppressing the peak of the load power supplied from the power system to the building in which the parking lot is installed,
A plurality of slow chargers placed in the parking lot;
A solar panel converter that converts the output power of the solar panel;
an energy storage device converter that converts the output power of the solar panel converter, stores it in an energy storage device, and converts and outputs the power stored in the energy storage device;
AC power supplied from the power system is converted into DC power, and DC power output from at least one of the electric vehicle, the solar panel converter, and the energy storage device converter connected to the slow charger is converted into AC power to be supplied to the building. Inverter to supply;
In the MVDC (Medium Voltage Direct Current) system composed of the solar panel converter, the energy storage device converter, the inverter, and the plurality of slow chargers, electrically connecting a power source supplying DC power and a load receiving DC power DC grid switch; and
The load power is monitored, and when the load power is below the peak, one or both of the solar panel converter, the energy storage device converter, and the inverter supplies DC power to the slow charger, and when the load power exceeds the peak, the load power exceeds the peak. An electric vehicle charger management system including a management server that controls AC power to be supplied to a building. The method according to claim 1, wherein the management server
a DC power controller that monitors the load power and selects the power source and the load in the MVDC system;
a power converter controller for operating a power converter selected as a power source by the DC power controller among the solar panel converter, the energy storage device converter, and the inverter;
a transmission line management unit that monitors the transmission line of the MVDC system and detects an abnormal state; and
An electric vehicle charger management system including a charger controller for controlling the operation of the slow charger. The electric vehicle charger management system of claim 2 , wherein the DC power control unit selects an electric vehicle to recover power by using a charging tendency of the electric vehicle connected to the slow charger. The method according to claim 2, wherein the DC system switch includes an insulation resistance measurement unit for measuring insulation resistance using a leakage current flowing from a transmission line of the MVDC system to ground in a live state,
The insulation resistance measuring unit,
a first leakage current measurement unit having one end electrically connected to a first transmission line and the other end connected to ground, and measuring a first leakage current flowing from the first transmission line toward the ground during a first period;
One end electrically connected to a second transmission line, the other end grounded to ground, and measuring a second leakage current flowing from the second transmission line toward the ground during a second period that does not overlap with the first period. 2 leakage current measuring unit;
The first leakage current measuring unit and the second leakage current measuring unit pass through the first leakage current measuring unit during the first period and the second leakage current passes through the second leakage current measuring unit during the second period. An electric vehicle charger management system including an insulation resistance measurement control unit controlling the second leakage current measurement unit. The method of claim 4,
The first leakage current measuring unit,
A first leakage current limiting resistor connected in series between the first transmission line and the ground, a first ammeter for measuring a first leakage current passing through the first leakage current limiting resistor, and a first ammeter that is turned on and off by the control unit to generate a first leakage current limiting resistor. A first switch for controlling the flow of leakage current;
The second leakage current measuring unit,
A second leakage current limiting resistor connected in series between the second transmission line and the ground, a second ammeter for measuring a second leakage current passing through the second leakage current limiting resistor, and a second ammeter that is turned on and off by the control unit to generate a second leakage current limiting resistor. An electric vehicle charger management system comprising a second switch for controlling the flow of leakage current. The method of claim 4,
Resistance values of the first leakage current limiting resistor and the second leakage current limiting resistor are smaller than insulation resistances of the first transmission line and the second transmission line. The electric vehicle charger management system of claim 2, wherein the PV converter includes an insulation resistance measurement unit for measuring insulation resistance using a leakage current flowing from a transmission line connected to a solar panel to ground in a live state of the DC system switch. The method of claim 1,
The plurality of slow chargers are installed on each parking surface of the parking lot.

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