Control device for a power conversion system

Abstract

Provided is a control device of a power conversion system capable of suppressing a temperature drop in the interior of a frame without additionally providing a space heater. The control device of the power conversion system has a determination section that determines whether or not a present time is nighttime in the environment of a power converter connected to a direct-current power source or an alternating-current power source or both, and a control section that, in the case where the determination section determines that the present time is nighttime, maintains a switch provided between the alternating-current power source or the direct-current power source and the power converter in a closed state, and maintains power consumption of a resistance provided in the interior of a frame of the power converter in a main circuit.

Description

Technical Field

[0001] This invention relates to a control device for a power conversion system. Background Technology

[0002] Patent document 1 discloses a power conversion system. According to this power conversion system, grid connection can be performed while suppressing inrush current.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 9-28040 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, in the power conversion system described in Patent Document 1, the power converter stops operating at night, during the period when the solar power generation equipment is not generating electricity. Therefore, the main circuit of the power converter is disconnected from both the solar power generation equipment and the AC power supply. In this state, heating is required by a space heater to suppress the temperature drop inside the power converter's housing.

[0008] This invention was proposed to solve the aforementioned problems. The object of this invention is to provide a control device for a power conversion system that can suppress temperature drop inside a housing without the need for a separate space heater.

[0009] Methods used to solve problems

[0010] The control device for the power conversion system of the present invention includes: a determination unit that determines whether it is currently nighttime in the environment of the power converter connected to a DC power supply or an AC power supply or both; and a control unit that, when the determination unit determines that it is currently nighttime, maintains a switch provided between the AC power supply or DC power supply and the power converter in a closed state, and maintains the power consumption of a resistor provided in the main circuit inside the housing of the power converter.

[0011] The control device for the power conversion system of the present invention includes: a determination unit that determines whether it is nighttime in the environment of the power converter connected between a DC power source and an AC power source; and a control unit that, when the determination unit determines that it is nighttime, maintains an AC switch provided between the AC power source or DC power source and the power converter in a closed state, thereby maintaining the power consumption of the power converter by operating the power converter.

[0012] Invention Effects

[0013] According to the present invention, when the control device determines that it is currently nighttime, it keeps the AC switch in a closed state. Therefore, power from the AC power source is consumed. As a result, the temperature drop inside the enclosure can be suppressed without the need for a separate space heater. Attached Figure Description

[0014] Figure 1 This is a structural diagram of a power system using the control device of the power conversion system of embodiment 1.

[0015] Figure 2 This is a hardware structure diagram of the control device of the power conversion system in Implementation Method 1. Detailed Implementation

[0016] Embodiments of the present invention will be described with reference to the accompanying drawings. Furthermore, in each drawing, the same or corresponding parts are assigned the same reference numerals. Repeated descriptions of these parts are appropriately simplified or omitted.

[0017] Implementation method 1.

[0018] Figure 1 This is a structural diagram of a power system using the control device of the power conversion system of embodiment 1.

[0019] exist Figure 1 In this diagram, DC power source 1 is a solar cell. AC power source 2 is three-phase and is supplied by a power company, etc.

[0020] The power conversion system comprises a frame 3, a power converter 4, a DC capacitor 5, a DC discharge resistor 6, a DC switch 7, an AC reactor 8, an AC capacitor 9, an AC discharge resistor 10, an AC switch 11, and a control device 12.

[0021] The frame 3 forms the outer contour of the power conversion system. The power converter 4 is connected between the DC power supply 1 and the AC power supply 2. The DC capacitor 5 is connected between the DC power supply 1 and the power converter 4. The DC discharge resistor 6 is connected in parallel with the DC capacitor 5. The DC switch 7 is connected between the DC power supply 1 and the DC capacitor 5. The AC reactor 8 is connected between the AC power supply 2 and the power converter 4. The AC capacitor 9 is connected between the AC power supply 2 and the AC reactor 8. The AC discharge resistor 10 is connected in parallel with the AC capacitor 9. The AC switch 11 is connected between the AC power supply 2 and the AC capacitor 9.

[0022] The control device 12 has a determination unit 13 and a control unit 14.

[0023] The determination unit 13 determines whether the current time is nighttime. For example, the determination unit 13 determines whether the current time is nighttime based on at least one of the power, voltage, and current values ​​of the output side of the DC power supply 1, which is the solar cell. For example, the determination unit 13 determines whether the current time is nighttime using a timer. For example, the determination unit 13 determines whether the current time is nighttime based on information from an external source.

[0024] The control unit 14 controls the power converter 4, the DC switch 7, and the AC switch 11 based on the determination result of the determination unit 13. For example, if the determination unit 13 determines that it is nighttime, the control unit 14 stops the operation of the power converter 4, keeps the DC switch 7 in the open state, and keeps the AC switch 11 in the closed state.

[0025] At this time, the DC discharge resistor 6 and the AC discharge resistor 10 consume power from the AC power source 2. As a result, the DC discharge resistor 6 and the AC discharge resistor 10 generate heat.

[0026] According to Embodiment 1 described above, when the control device 12 determines that it is nighttime, it keeps the AC switch 11 closed, thus preventing the power consumption of the DC discharge resistor 6 and AC discharge resistor 10 installed inside the housing 3 of the power converter 4. Therefore, it is possible to suppress the temperature drop inside the housing 3 without the need for a separate space heater. As a result, condensation can be suppressed, and the temperature inside the housing 3 can be prevented from falling below the operating temperature of the components of the power conversion system.

[0027] Furthermore, since a space heater is not required, the structure of the power conversion system can be simplified. As a result, the cost of the power conversion system can be reduced.

[0028] Furthermore, in the control device 12, if it is determined that it is nighttime, the AC switch 11 can be kept closed to operate the power converter 4 and offset the reactive power flowing from the AC capacitor 9 to the AC power source 2. In this case, heat is generated due to the power conversion losses of the power converter. Therefore, by keeping the AC switch 11 closed, the reactive power flowing from the AC capacitor to the AC power source 2 can be suppressed. In this case, the temperature drop inside the frame 3 can be suppressed without the need for a separate space heater.

[0029] Alternatively, the power converter 4 can be operated while the current remains at zero. In this case, heat is generated due to the power conversion losses of the power converter. In this case, the temperature drop inside the frame 3 can be suppressed without the need for a separate space heater.

[0030] Furthermore, the control device 15 of Embodiment 1 can also be applied to the power system that uses an energy storage device as the DC power source 1. In this case, the DC switch 7 is kept closed instead of the AC switch 11, allowing the power converter to operate under no-load conditions. In this case, heat is generated due to the power conversion losses of the power converter. In this case, the temperature drop inside the housing 3 can be suppressed without the need for a separate space heater.

[0031] In addition, the control device can also identify the temperature inside the frame and close the AC switch 11 or DC switch 7 at night only when the temperature is below a threshold.

[0032] Next, use Figure 2 An example illustrating control device 12.

[0033] Figure 2 This is a hardware structure diagram of the control device of the power conversion system in Implementation Method 1.

[0034] The functions of the control device 12 can be implemented by a processing circuit. For example, the processing circuit has at least one processor 100a and at least one memory 100b. For example, the processing circuit has at least one dedicated hardware 200.

[0035] When the processing circuit has at least one processor 100a and at least one memory 100b, the functions of the control device 12 are implemented by software, firmware, or a combination of software and firmware. At least one of the software and firmware is recorded as a program. At least one of the software and firmware is stored in at least one memory 100b. The at least one processor 100a implements the functions of the control device 12 by reading and executing the program stored in the at least one memory 100b. The at least one processor 100a may also be referred to as a central processing unit, processing device, arithmetic unit, microprocessor, microcomputer, or DSP. For example, the at least one memory 100b is a non-volatile or volatile semiconductor memory such as RAM, ROM, flash memory, EPROM, EEPROM, disk, floppy disk, optical disk, CD, MD, DVD, etc.

[0036] When the processing circuit has at least one dedicated hardware 200, the processing circuit is implemented, for example, by a single circuit, a composite circuit, a programmable processor, a parallel programmable processor, an ASIC, an FPGA, or a combination thereof. For example, each function of the control device 12 is implemented by the processing circuit individually. For example, each function of the control device 12 is implemented together by the processing circuit.

[0037] Regarding the various functions of the control device 12, some can be implemented by dedicated hardware 200, while others can be implemented by software or firmware. For example, the functions of the determination unit 13 can be implemented by a processing circuit that is a dedicated hardware 200, while functions other than those of the determination unit 13 can be implemented by at least one processor 100a reading and executing a program stored in at least one memory 100b.

[0038] In this way, the processing circuit implements the various functions of the control device 12 through hardware 200, software, firmware, or a combination thereof.

[0039] Industrial availability

[0040] As described above, the control device for the power conversion system of the present invention can be used in a system that suppresses the temperature drop inside the housing of the power conversion system.

[0041] Label Explanation

[0042] 1 DC power supply; 2 AC power supply; 3 frame; 4 power converter; 5 DC capacitor; 6 DC discharge resistor; 7 DC switch; 8 AC reactor; 9 AC capacitor; 10 AC discharge resistor; 11 AC switch; 12 control device; 13 decision unit; 14 control unit; 100a processor; 100b memory; 200 hardware.

Claims

1. A control device for a power conversion system, characterized in that, have: The determination unit determines whether it is currently nighttime in the environment of the power converter connected between the solar cells and the AC power source; and If the determination unit determines that it is nighttime, the control unit will keep the switch between the AC power source or the solar cell and the power converter closed, thereby maintaining the power consumption of the power converter by operating the power converter. The power converter has a DC capacitor connected between the solar cell and the power converter on the DC side, and a DC discharge resistor connected in parallel with the DC capacitor. The power converter has an AC capacitor connected between the solar cell and the power converter on the AC side, and an AC discharge resistor connected in parallel with the AC capacitor. The control device is configured to output reactive power at night, when the AC capacitor is heated due to power consumption from the AC power source and the DC discharge resistor and the AC discharge resistor, in order to offset the reactive power flowing from the AC capacitor to the system side and the heat generated by power conversion losses. The control unit has a temperature recognition unit and is configured to close the switch located between the power converter and the solar cell or the AC power source only when the temperature is low at night.

2. A control device for a power conversion system, characterized in that, have: The determination unit determines whether it is currently nighttime in the environment of the power converter connected between the solar cells and the AC power source; and If the determination unit determines that it is nighttime, the control unit will keep the switch between the AC power source or the solar cell and the power converter closed, thereby maintaining the power consumption of the power converter by operating the power converter. The power converter has a DC capacitor connected between the solar cell and the power converter on the DC side, and a DC discharge resistor connected in parallel with the DC capacitor. The power converter has an AC capacitor connected between the solar cell and the power converter on the AC side, and an AC discharge resistor connected in parallel with the AC capacitor. The power converter is connected to the system via a transformer. The control device is configured to output reactive power at night, when the transformer is generating heat due to power consumption from the AC power source, the DC discharge resistor, and the AC discharge resistor, in order to offset the reactive power flowing from the transformer to the system side and the heat generated by power conversion losses. The control unit has a temperature recognition unit and is configured to close the switch located between the power converter and the solar cell or the AC power source only when the temperature is low at night.

3. A control device for a power conversion system, characterized in that, have: The determination unit determines whether it is currently nighttime in the environment of the power converter connected between the solar cells and the AC power source; and If the determination unit determines that it is nighttime, the control unit will keep the switch between the AC power source or the solar cell and the power converter closed, thereby maintaining the power consumption of the power converter by operating the power converter. The power converter has a DC capacitor connected between the solar cell and the power converter on the DC side, and a DC discharge resistor connected in parallel with the DC capacitor. The power converter has an AC capacitor connected between the solar cell and the power converter on the AC side, and an AC discharge resistor connected in parallel with the AC capacitor. The control device is configured such that, as current flows through the AC discharge resistor and the DC discharge resistor, heat is generated due to the conversion losses of the power converter. The control unit has a temperature recognition unit and is configured to close the switch located between the power converter and the solar cell or the AC power source only when the temperature is low at night.

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