Electric mobile unit connection unit, electric mobile unit charging / discharging system, and control method for power converter.

Abstract

This invention discloses a technology that enables the suppression of overcurrents that may occur when connecting circuits after insulation diagnosis is completed, using a simple circuit. [Solution] A power supply system comprising: an inverter connected to an AC electrical system; a converter connected to the DC side of the inverter via a first DC circuit; a connecting cable connectable to an electrically powered mobile body; a smoothing capacitor provided in a second DC circuit connecting the converter and the connecting cable; and a control unit that controls the inverter and the converter. When the control unit completes an insulation diagnosis of the output circuit to the electrically powered mobile body using the DC voltage output by the converter, it causes the inverter to perform voltage control so that the voltage of the first DC circuit maintains a predetermined first voltage, and then causes the converter to step down the second DC circuit so that the voltage across the smoothing capacitor is less than or equal to a predetermined second voltage.

Description

Technical Field

[0001] The present invention relates to a power supply system.

Background Art

[0002] In recent years, various electric vehicles such as electric cars, ships, and airplanes powered by an electric motor have been increasingly popular. Along with this, the development of electrical equipment that controls charging of on-vehicle batteries (hereinafter sometimes referred to as "travel batteries" or "main batteries") that supply power to the drive electric motor has also been actively carried out (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a connection cable of electrical equipment is connected to an electric vehicle, an insulation diagnosis for confirming that there is no abnormality in the connection state is sequentially performed. In the insulation diagnosis, a predetermined voltage is applied to the output circuit up to the vehicle contactor in order to check for a short circuit and a ground fault. The applied voltage in the insulation diagnosis is usually higher than the voltage of the electricity flowing through the connection cable after the insulation diagnosis is completed. Therefore, for example, when the electrical equipment has a smoothing capacitor, an overcurrent may occur due to the potential difference between the voltage of the circuit of the electric vehicle and the voltage of the smoothing capacitor of the electrical equipment when the circuit is connected after the insulation diagnosis.

[0005] One possible countermeasure against such overcurrents is to install a discharge circuit to discharge the charge stored in the smoothing capacitor after the insulation diagnosis is completed, in order to reduce the potential difference between the voltage of the circuit inside the motorized mobile unit and the voltage of the smoothing capacitor. However, installing such a discharge circuit would increase the number of components, resulting in higher costs and larger size.

[0006] Therefore, this invention discloses a technology that enables the suppression of overcurrents that may occur when connecting circuits after the completion of insulation diagnosis using a simple circuit. [Means for solving the problem]

[0007] To solve the above problems, in the present invention, once the insulation diagnosis is completed, the inverter is made to perform voltage control so that the voltage in the circuit connecting the inverter and the converter is maintained at a predetermined voltage, and the converter is stepped down so that the voltage across the smoothing capacitor provided in the circuit connecting the connecting cable to the electric mobile body and the converter is below a predetermined voltage.

[0008] More specifically, the present invention is a power supply system comprising: an inverter connected to an AC electrical system; a converter connected to the DC side of the inverter via a first DC circuit; a connecting cable connectable to an electrically powered mobile body; a smoothing capacitor provided in a second DC circuit connecting the converter and the connecting cable; and a control unit that controls the inverter and the converter. When the control unit completes an insulation diagnosis of the output circuit to the electrically powered mobile body using the DC voltage output by the converter, it causes the inverter to perform voltage control so that the voltage of the first DC circuit is maintained at a predetermined first voltage, and then causes the converter to step down the second DC circuit so that the voltage across the smoothing capacitor is less than or equal to a predetermined second voltage.

[0009] Here, an electrically powered mobile device refers to an electrically powered mobile device, such as an electric passenger car, a heavy vehicle, a motorcycle, a ship, an aircraft, and various other types of mobile devices. The first voltage is the control target value when the inverter controls the voltage of the first DC circuit. The second voltage is the voltage of the second DC circuit that should be reached by stepping down the voltage using the converter.

[0010] In the power supply system described above, once the insulation diagnosis is complete, the inverter is instructed to perform voltage control so that the voltage in the first DC circuit connecting the inverter and the converter is maintained at a predetermined first voltage. At the same time, the converter is instructed to step down the voltage so that the voltage across the smoothing capacitor in the second DC circuit connecting the connecting cable to the electric mobile unit and the converter is below a predetermined second voltage. Therefore, with the power supply system described above, the charge stored in the smoothing capacitor during the insulation diagnosis can be discharged by the converter without the need to provide a separate discharge circuit or element. Furthermore, since the discharge is performed while the voltage in the first DC circuit is maintained at a predetermined first voltage, the voltage in the first DC circuit will not become excessive due to the discharge. Thus, it can be said that the suppression of reverse current to the electric mobile unit that may occur when connecting the circuit inside the electric mobile unit to the power supply system after the insulation diagnosis is complete can be achieved with a simple circuit.

[0011] Furthermore, the control unit may electrically connect the circuit inside the motorized mobile body to the connecting cable after the voltage across the smoothing capacitor has been reduced to the second voltage or lower by the converter. This allows for the electrical connection between the circuit inside the motorized mobile body and the connecting cable while minimizing the influence of the residual charge of the smoothing capacitor on the circuit inside the motorized mobile body after the insulation diagnosis is completed.

[0012] Furthermore, power generation equipment or energy storage equipment may be further connected to the first DC circuit. Even in this case, the inverter controls the voltage so that the voltage of the first DC circuit maintains a predetermined first voltage, so that the smoothing capacitor can be discharged by the converter regardless of the operating status of the power generation equipment or energy storage equipment.

[0013] Furthermore, the first voltage may be the rated voltage of the electrical components connected to the first DC circuit. If the inverter controls the voltage to maintain such a first voltage, even if the smoothing capacitor is discharged by the converter, there is no possibility of an excessive voltage being applied to the electrical components connected to the first DC circuit.

[0014] Furthermore, the electrical system may include at least one of the on-site electrical system where the power supply system is installed, and the power system. This makes it possible to consume the power discharged from the smoothing capacitor by the converter in the on-site electrical system or power system. [Effects of the Invention]

[0015] According to the present invention, it is possible to suppress overcurrents that may occur when connecting circuits after the insulation diagnosis is completed using a simple circuit. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a diagram illustrating the electrical behavior realized by the EVPS disclosed in this application. [Figure 2] Figure 2 shows an example of an electrical system using an EVPS according to this embodiment. [Figure 3] Figure 3 shows the electrical internal configuration of an EV and an EVPS. [Figure 4] Figure 4 shows an example of the operation flow related to discharge control. [Modes for carrying out the invention]

[0017] <Examples of application> Figure 1 is an abbreviation for EVPS (Electric Vehicle Power System) disclosed in this application. It is a diagram showing an overview of the electrical behavior realized in an example of the "power supply system" mentioned above. The EVPS is an electrical facility that charges etc. the on-vehicle battery for driving mounted on various electric vehicles (hereinafter referred to as "EV"), such as a BEV (Battery Electric Vehicle) that runs only on battery power, a PHV (Plug-in Hybrid Vehicle) that uses both a battery and an internal combustion engine, a FCV (Fuel Cell Vehicle) that runs on fuel cell power. In the following description, the case where an EV connection unit is connected to an EV running on the power of an on-vehicle battery will be described as an example. However, when the EV connection unit is connected to an EV running on the power of an on-vehicle generator such as a fuel cell, for example, it will receive the power generated by the EV.

[0018] The EVPS includes a converter that automatically adjusts the duty ratio so that the voltage of the circuit connecting the EV and the EVPS becomes an appropriate voltage, a smoothing capacitor for smoothing the voltage of the circuit, an inverter connected to the converter, etc. Further, the EV includes an on-vehicle battery, a switch for opening and closing the circuit connecting the on-vehicle battery and the connection cable of the EVPS, etc. The EVPS performs charging and discharging of the on-vehicle battery (charging of the on-vehicle battery and power supply from the on-vehicle battery) by appropriately adjusting the switches provided in the EVPS and the EV, and the duty ratios of the converter and the inverter.

[0019] In the electrical facility to which the EV is connected, there are various charging standards such as CHAdeMO (registered trademark). In such charging standards, various matters such as a method for diagnosing the connection state of the connection cable and an upper limit value of the current are defined in order to ensure the safety of the user and the maintenance of the equipment. Therefore, in the EVPS shown in FIG. 1, when the connection cable is connected to the EV, insulation diagnosis is performed by applying a prescribed voltage to the connection cable with the switch (vehicle contact) of the EV open. And when the normal condition of the equipment is confirmed in the insulation diagnosis, the switch of the EV is closed and charging or discharging of the battery is started.

[0020] When a specified voltage is applied to the connection cable in the insulation diagnosis, due to the residual charge in the smoothing capacitor, a potential difference similar to the specified voltage remains in the circuit connecting the converter and the EV even after the insulation diagnosis is completed. Therefore, in the EVPS disclosed in the present application, when the insulation diagnosis is completed, before electrically connecting the in-vehicle battery of the EV and the converter, the voltage of the circuit connecting the converter and the EV is stepped down by the converter, thereby discharging the residual charge in the smoothing capacitor to the upper electrical system side. As a result, the magnitude of the current generated in the circuit due to the potential difference between the smoothing capacitor and the in-vehicle battery is kept within the range of the charging standard specifications. The arrowed line in FIG. 1 schematically shows an example of how the charge of the smoothing capacitor is discharged by the converter to the electrical system side higher than the EVPS.

[0021] <Embodiment> Hereinafter, the embodiments will be described with reference to the drawings. The following embodiments are one aspect of the present application and do not limit the technical scope of the present application.

[0022] FIG. 2 is a diagram showing an example of an electrical facility using the EVPS according to the embodiment. As shown in FIG. 2, the electrical facility 1 is connected to the power grid P. The electrical facility 1 may be installed in the house 2 as illustrated in FIG. 2, or may be installed in an apartment building, a commercial facility, or various other facilities. The electrical facility 1 includes a distribution board 3, an EVPS 4, a converter 6 for solar power generation, and an in-house load 7. The EVPS 4 is an electrical facility that can be connected to the EV 5 by a connection cable 8.

[0023] The distribution board 3 is a main circuit breaker that controls the role of opening and closing the circuit connecting the electrical facilities in the house 2 and the power grid P, a wiring circuit breaker that opens and closes the circuit of the wiring branched from the distribution board 3 to various places in the house 2, a bus bar connecting the main circuit breaker and the wiring circuit breaker, and an electrical facility incorporating a leakage circuit breaker, etc. The EVPS 4 and the in-house load 7 in the house 2 are electrically connected through the distribution board 3. Also, the EVPS 4 and the in-house load 7 in the house 2 are electrically connected to the power grid P through the distribution board 3.

[0024] ​EVPS4 is electrical equipment that charges or discharges the onboard battery installed in EV5. EVPS4 comprises an EV connection unit 9 with a connection cable 8 that can be connected to EV5, and an inverter 10 capable of bidirectional conversion of electricity from AC to DC or DC to AC (AC / DC conversion). The EV connection unit 9 operates according to the amount of charge stored in EV5. The inverter 10 has a DC bus 11 connected to the EV connection unit 9 and the converter 6 for solar power generation, which is connected to the DC side, and a circuit connected to the distribution board 3, which is connected to the AC side. A capacitor IC for voltage control is connected to this DC bus 11. The inverter 10 then converts power from the distribution board 3 to the DC bus 11, or from the DC bus 11 to the distribution board 3, according to the charging / discharging state of the EV connection unit 9 and the power generation state of the solar power generation panel 12.

[0025] The converter 6 is an electrical device for transmitting electricity generated by solar panels 12 installed on the roof or premises of the house 2 to the DC bus 11. The converter 6 converts the voltage of the DC power generated by the solar panels 12. If the EVPS 4 does not support solar power generation, the converter 6 may be connected to the distribution board 3 via an inverter. Furthermore, the electrical equipment 1 may be configured to include equipment that generates electricity from other energy sources that replace solar power, such as a fuel cell. Also, the electrical equipment 1 may be configured to omit the power generation equipment, or to include a stationary battery storage system.

[0026] The in-house load 7 consists of various electrical appliances installed in the house 2. Examples of in-house load 7 connected to the distribution board 3 include lighting fixtures installed in the house 2, wiring connectors (outlets) installed on the walls of the house 2, ventilation equipment, and various other electrical appliances. The in-house load 7 may receive power not only from the power grid P, but also from the EVPS 4 depending on the amount of energy stored in the EV 5 and the amount of power generated by the solar power generation panels 12.

[0027] Figure 3 shows the electrical internal configuration of EV5 and EVPS4. The details of EV5 and EVPS4 will be explained below with reference to Figure 3.

[0028] As shown in Figure 3, the EV5 comprises a main battery MV, an EV relay VS, an inlet IL, and a control device VC. The main battery MV is an on-board battery that supplies power to the electric motor used for driving the EV5. Examples of the main battery MV include lithium-ion batteries, solid-state batteries, and various other types of secondary batteries. The inlet IL is a terminal for attaching and detaching the connection cable 8, and is designed to mate with a plug CN provided at the end of the connection cable 8. The inlet IL is located on the exterior of the EV5 to allow the EV5 user to easily attach and detach the plug CN, and is equipped with an electromagnetic locking mechanism to prevent accidental attachment or detachment of the plug CN. The EV relay VS is an electromagnetic contactor that can open and close the circuit connecting the inlet IL and the main battery MV, and performs opening and closing operations according to the control signal of the control device VC. The control device VC controls various operations, such as opening and closing the EV relay VS, by communicating with the control device CC of the EVPS4 through the control line LC.

[0029] As shown in Figure 3, the EV connection unit 9 includes a converter DC connected to the inverter 10 via a DC bus 11, power lines LH and LL connecting the converter DC and the connection cable 8, a switch SS provided in the middle of power line LH, and a smoothing capacitor HC connected between power line LH and power line LL. The converter DC and switch SS of the EV connection unit 9 are connected to the inverter 1 It is controlled by the control unit CC of the EVPS4, which also controls the 0. In Figure 3, the EV connection unit 9 is shown as being integrated with the inverter 10 within the EVPS4, but the EV connection unit 9 may be housed in a separate enclosure from the inverter 10. Also, in Figure 3, the connection cable 8 is shown as being connected to the EVPS4 enclosure and being an inseparable part of it, but the connection cable 8 may be removable from the EVPS4 using tools or the like to allow for maintenance work such as parts replacement.

[0030] The DC converter is a converter that automatically adjusts the duty cycle so that the power lines LH and LL connected to EV5 have an appropriate voltage. In this embodiment, EVPS4 is configured to not only charge EV5 but also charge and discharge it, and as will be described later, the DC converter also controls the discharge of the smoothing capacitor HC, so the DC converter is an isolated bidirectional DC / DC converter.

[0031] The smoothing capacitor HC is a capacitor that smooths the voltage of the DC power output by the converter DC to the power lines LH and LL. The smoothing capacitor HC is selected to have an appropriate capacitance according to the power flowing through the EVPS4.

[0032] The switching unit SS is a relay that switches the power line LH connecting the converter DC and the connecting cable 8. It includes a DC relay DS and a puncture prevention relay TS for switching the power line LH connecting the converter DC and the connecting cable 8, and a resistor TR connected in series with the puncture prevention relay TS. The switching unit SS operates in response to a control signal from the control device CC. As shown in Figure 3, in the switching unit SS, the puncture prevention relay TS and resistor TR, which are connected in series, and the DC relay DS are in a parallel circuit. Therefore, the switching unit SS can switch the power line LH connecting the converter DC and the connecting cable 8 using either the DC relay DS or the puncture prevention relay TS. When the DC relay DS is closed in the switching unit SS, the connecting cable 8 becomes electrically directly connected to the DC side of the converter DC. When the puncture prevention relay TS is closed in the switching unit SS, the connecting cable 8 becomes connected to the DC side of the converter DC via the resistor TR.

[0033] The control device CC communicates with EV5 via the control line LC to control various functions such as the opening and closing of the switching unit SS and the operation of the converter DC and inverter 10. The control device CC is a device that realizes various controls by executing a computer program stored in memory, and is equipped with an input / output interface for various input operations and information display.

[0034] The following describes an example of the operation flow realized in EVPS4. When an EV5 user parks their EV5 near EVPS4 and connects the connection cable 8 to the EV5, after confirming that there are no abnormalities in the insulation diagnosis, the smoothing capacitor HC is discharged, and then the electrical connection between EVPS4 and the EV5's main battery MV is made.

[0035] <Insulation Diagnosis> The control unit CC detects that the connection cable 8 has been connected to the EV5 via communication via the control line LC, and after obtaining various information related to charging and discharging (such as the status of the main battery MV) from the control unit VC of the EV5, it closes the switch SS. Then, the control unit CC operates the inverter 10 and the converter DC, gradually increasing the potential difference between the power line LH and the power line LL. The control unit CC then monitors the insulation resistance value between the power line LH and the power line LL until the potential difference between them reaches a specified test voltage (for example, 450V). Even when the potential difference between the power line LH and the power line LL reaches the specified test voltage, if the insulation resistance value between the power line LH and the power line LL is above the specified reference value, the control unit CC diagnoses that there is no abnormality in insulation. Meanwhile, the control unit CC monitors the insulation resistance value between the power line LH and the power line L When the potential difference between L and power line LH is below the specified test voltage, if the insulation resistance value between power line LH and power line LL falls below the specified standard value, a diagnosis of an insulation abnormality is made, and the insulation abnormality is reported.

[0036] <Discharge control> After the insulation test is completed, a potential difference of approximately the same magnitude as the test voltage remains between power line LH and power line LL due to the residual charge stored in the smoothing capacitor HC during the insulation test. Therefore, after the insulation test is completed, the control device CC performs the following discharge control to discharge the residual charge in the smoothing capacitor HC. Figure 4 shows an example of the operation flow related to discharge control.

[0037] (Step S1) The control device CC causes the inverter 10 to start voltage control so that the voltage of the DC bus 11 is maintained at an appropriate specified voltage (an example of the "first voltage" as referred to in this application). This specified voltage, which is the control target value of the inverter 10, may be any voltage, or it may be the rated voltage of the voltage control capacitor IC connected to the DC bus 11 (for example, 450V).

[0038] (Step S2) Next, the control device CC uses a voltmeter to measure the potential difference between power line LH and power line LL, to which the ends of the smoothing capacitor HC are connected, to cause the converter DC to start discharge control so that the voltage on the EV5 side of the converter DC (an example of the "voltage across both ends" as referred to in this application) decreases. Specifically, the discharge control of the converter DC is the operation of the converter DC to change its duty cycle so that the voltage of the smoothing capacitor HC decreases. When the converter DC starts discharge control, the power stored in the smoothing capacitor HC flows through the converter DC to the DC bus 11. Since the voltage of the DC bus 11 is controlled to a constant level by the inverter 10, it hardly changes even when power flows from the converter DC to the DC bus 11. The power that flows from the converter DC to the DC bus 11 then flows through the inverter 10 to the distribution board 3. The power that flows through the inverter 10 to the distribution board 3 is consumed by the household load 7 through the distribution board 3.

[0039] (Step S3) After the control device CC starts discharge control on the converter DC, it determines whether the voltage on the EV5 side of the converter DC has fallen below a specified voltage (an example of the "second voltage" as referred to in this application). In this determination, the specified voltage is the voltage at which the charge remaining in the smoothing capacitor HC can be considered to have been discharged, and is, for example, 20V.

[0040] (Step S4) If the control device CC made a positive determination in step S3, it instructs the converter DC to terminate the discharge control. When the converter DC terminates the discharge control, the discharge of the smoothing capacitor HC stops, and the flow of power that was flowing from the converter DC to the DC bus 11 stops.

[0041] As a result of the series of processes in steps S1 to S4 described above, the discharge of the charge stored in the smoothing capacitor HC is completed by the insulation diagnosis. After the discharge of the charge stored in the smoothing capacitor HC is complete, for example, the control device CC causes the control device VC to switch on the EV relay VS, thereby electrically connecting the converter DC and the main battery MV, and operating the converter DC so that the main battery MV is charged or discharged. When the EV relay VS is switched on, the charge stored in the smoothing capacitor HC has been discharged, so no current that would affect the main battery MV flows from EVPS4 to EV5.

[0042] In the EVPS4 according to the above embodiment, the charge remaining in the smoothing capacitor HC due to the insulation diagnosis is discharged by the converter DC without the need to provide a separate discharge circuit or element. This makes it possible. Furthermore, since the smoothing capacitor HC is discharged by the converter DC while the inverter 10 is controlling the voltage, the voltage of the DC bus 11 will not become excessive. Therefore, there is no need to select a large-capacity capacitor IC or other electrical component connected to the DC bus 11 that takes into account the discharge of the smoothing capacitor HC by the converter DC. Thus, it can be said that the suppression of overcurrent that may occur when connecting the main battery MV and EVPS4 after the insulation diagnosis is completed can be achieved with a simple circuit.

[0043] <Variation> In the above embodiment, step S3 was performed based on voltage, but this may be replaced with a determination based on whether a specified waiting time has elapsed, for example. Also, the voltage control of the inverter 10, which was started in step S1, may be terminated after step S4, or it may be continued when the EVPS4 charges or discharges the main battery MV.

[0044] Furthermore, EVPS4 may perform charging and discharging of EV5 in response to commands from a higher-level device that monitors and controls the entire electrical equipment installed in the house 2. Also, although the above embodiment exemplifies an electrical equipment 1 that receives power from a power grid P constructed by a power company, etc., electrical equipment 1 may be disconnected from the power grid P and become an electrical equipment independent of the power grid P through a private power generation facility installed in the house 2. In addition, EVPS4 may be used for charging and discharging various electric mobile devices other than vehicles, or for supplying power from various electric mobile devices. Furthermore, the above embodiment may be modified as appropriate.

[0045] Furthermore, this application includes the following supplementary matters. <Note 1> An inverter (10) connected to an AC electrical system, A converter (DC) connected to the DC side of the inverter via the first DC circuit (11), A connection cable (8) that can be connected to an electrically powered mobile unit (5) that moves using electricity, A smoothing capacitor (HC) is provided in the second DC circuit (LH,LL) that connects the converter and the connecting cable, The system comprises a control unit (CC) that controls the inverter and the converter, The control unit, When the insulation diagnosis of the output circuit to the motorized mobile body using the DC voltage output by the converter is completed, the inverter is instructed to perform voltage control so that the voltage of the first DC circuit maintains a predetermined first voltage, and the converter is instructed to step down the second DC circuit so that the voltage across the smoothing capacitor becomes less than or equal to a predetermined second voltage. Power supply system. [Explanation of symbols]

[0046] P··Power system 1. Electrical equipment 2. Housing 3. Distribution board 4. EVPS 5. EV 6-converter 7. In-house load 8. Connection Cable 9. EV Connection Unit 10. Inverter 11. DC Bus 12. Solar power panels LC control line LH··Power line LL··Power line CC··Control device SS...Opening / Closing Section DS DC relay TS--Pierce Prevention Relay TR··Resistor HC smoothing capacitor DC converter CN plug MV Main Battery VS EV Relay VC Control Unit IL··Inlet ICs and Capacitors

Claims

1. An inverter connected to an AC electrical system, A converter connected to the DC side of the inverter via the first DC circuit, A connection cable that can be connected to an electrically powered mobile vehicle, A smoothing capacitor is provided in the second DC circuit connecting the converter and the connecting cable, The system comprises a control unit that controls the inverter and the converter, The control unit, When an insulation diagnosis is completed, which monitors the insulation resistance value between the power lines connecting the converter and the connecting cable using the DC voltage output by the converter, and when no abnormality is diagnosed in the insulation diagnosis, the inverter is instructed to perform voltage control so that the voltage of the first DC circuit maintains a predetermined first voltage, and the converter is instructed to step down the second DC circuit so that the voltage across the smoothing capacitor becomes less than or equal to a predetermined second voltage. Power supply system.

2. The control unit electrically connects the circuit inside the motorized mobile body to the connecting cable after the voltage across the smoothing capacitor has been reduced to the second voltage or less by the voltage reduction by the converter. The power supply system according to claim 1.

3. The first DC circuit is further connected to a power generation facility or an energy storage facility. The power supply system according to claim 1 or 2.

4. The first voltage is the rated voltage of the electrical component connected to the first DC circuit. A power supply system according to any one of claims 1 to 3.

5. The aforementioned electrical system includes at least one of the on-site electrical system and the power system in which the power supply system is installed. A power supply system according to any one of claims 1 to 4.

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