Control device, power conditioner, heat pump system, and electrical equipment

Abstract

[Problem] To adjust power pulsation caused to a DC link unit due to fluctuations in power consumption of electrical equipment connected to the DC link unit. [Solution] This control device controls one or more converters for transmitting first DC power to a DC link unit. The first DC power includes a first power pulsation, which is an AC component. The DC link unit is configured to be capable of transmitting second DC power to electrical equipment connected to the DC link unit. The control device comprises a pulsation acquisition unit for acquiring a second power pulsation, which is an AC component included in the second DC power, and adjusts the first power pulsation in accordance with the second power pulsation acquired by the pulsation acquisition unit.

Description

Control Device, Power Conditioner, Heat Pump System, and Electrical Equipment

[0001] The present disclosure relates to a control device, a power conditioner, a heat pump system, and electrical equipment.

[0002] Patent Document 1 discloses a power system including a DC link section, a grid-connected inverter connected to the DC link section, one or more DC power sources, a smoothing capacitor, and one or more electrical devices. The electrical device has a pulsating power adjustment function for adjusting a pulsating power component, which is a frequency component of an integer multiple of 2 or more of the power supply frequency of the single-phase AC power supply, in the DC power consumed by the electrical device according to the operation of the grid-connected inverter and the voltage phase of the single-phase AC power supply.

[0003] Japanese Patent No. 7514001

[0004] In a power generation system that feeds generated power such as solar panels back to the grid power supply, a configuration in which electrical equipment such as an air conditioner is connected to the DC link section of the power generation system is known. When the fluctuation of the power consumption of the electrical equipment connected to the DC link section is large, the power fluctuation of the DC link section, that is, the power pulsation becomes large, and there is a risk that the distortion of the power fed back to the grid power supply becomes large. The purpose of the present disclosure is to adjust the power pulsation of the DC link section caused by the fluctuation of the power consumption of the electrical equipment connected to the DC link section.

[0005] The control device in the first aspect is a control device that controls one or more converters that transmit first DC power to a DC link section, wherein the first DC power includes a first power pulsation which is an AC component, the DC link section is configured to transmit second DC power to electrical equipment connected to the DC link section, and the control device includes a pulsation acquisition unit that acquires a second power pulsation which is an AC component included in the second DC power, and adjusts the first power pulsation according to the second power pulsation acquired by the pulsation acquisition unit. In this case, the power pulsation of the DC link section caused by fluctuations in the power consumption of the electrical equipment connected to the DC link section can be adjusted. The control device in the second aspect is the control device in the first aspect, wherein the DC link section is configured to transmit and receive third DC power to and from a capacitor connected to the DC link section, and the control device adjusts the first power pulsation so as to reduce the third power pulsation which is an AC component included in the third DC power. In this case, the reduction in the lifespan of the capacitor can be suppressed. The control device according to the third aspect is a control device according to the first or second aspect, which adjusts the amplitude difference and phase difference between the second power pulsation and the first power pulsation. In this case, the adjustment of the power pulsation becomes easier. The control device according to the fourth aspect is a control device according to any one of the first to third aspects, which adjusts the first power pulsation so that it approaches the second power pulsation. In this case, the power pulsation component can be canceled out. The control device according to the fifth aspect is a control device according to any one of the first to fourth aspects, wherein the DC link section is configured to transmit and receive fourth DC power between the DC link section and a grid-connected inverter connected to a single-phase grid power supply, and the control device adjusts the first power pulsation by a frequency component twice the frequency of the grid power supply in response to the fourth power pulsation of the fourth DC power, which is a frequency component twice the frequency of the grid power supply. In this case, the power pulsation component generated in the grid-connected inverter can be adjusted. The control device according to the sixth aspect is a control device according to any one of the first to fifth aspects, wherein at least one of the converters is connected to a power supply and converts the power of the power supply into the first DC power.In this case, the power pulsation of the DC link section caused by fluctuations in the power consumption of the electrical equipment connected to the DC link section can be adjusted. The control device according to the seventh aspect is a control device according to any one of the first to sixth aspects, wherein the pulsation acquisition unit acquires information correlated with the second power pulsation from the electrical equipment. In this case, the electrical equipment and the control device can share the computational processing. The control device according to the eighth aspect is a control device according to any one of the first to seventh aspects, wherein the pulsation acquisition unit acquires the second DC power from a DC power measuring unit that measures the second DC power. In this case, the second DC power can be easily acquired even if there are multiple electrical devices. The control device according to the ninth aspect is a control device according to any one of the first to eighth aspects, wherein the electrical equipment includes a rotating electric machine. In this case, the power pulsation caused by the rotation of the rotating electric machine can be adjusted. The control device according to the tenth aspect is the control device according to the ninth aspect, wherein the second power pulsation pulsates at integer multiples of the rotational speed of the rotating electric machine. In this case, power pulsations caused by the rotation of the rotating electric machine can be adjusted. The power conditioner according to the eleventh aspect comprises a control device according to any one of the first to tenth aspects, one or more converters controlled by the control device, a DC link section to which the converters are connected and to which electrical equipment can be connected, and a grid-connected inverter connected to the DC link section and to which grid power can be connected. In this case, power pulsations in the DC link section caused by fluctuations in the power consumption of the electrical equipment connected to the DC link section can be adjusted. The heat pump system according to the twelfth aspect comprises a refrigeration device as the electrical equipment in the power conditioner according to the eleventh aspect. In this case, power pulsations in the DC link section caused by fluctuations in the power consumption of the electrical equipment connected to the DC link section can be adjusted.The electrical equipment in the 13th aspect is an electrical device connected to a DC link section, the DC link section being controlled by a control device and connected to one or more converters that transmit first DC power to the DC link section, the first DC power including a first power pulsation which is an AC component, the DC link section being configured to transmit second DC power to the electrical equipment, the control device comprising a pulsation acquisition unit that acquires a second power pulsation which is an AC component included in the second DC power, and is configured to adjust the first power pulsation according to the second power pulsation acquired by the pulsation acquisition unit, and the electrical equipment comprising a communication unit that transmits information correlated with the second power pulsation to the pulsation acquisition unit. In this case, the power pulsation of the DC link section caused by fluctuations in the power consumption of the electrical equipment connected to the DC link section can be adjusted. The electrical equipment in the 14th aspect is a refrigeration system, the electrical equipment in the 13th aspect is a refrigeration system.

[0006] This figure shows an example configuration of a power system to which the control device according to the first embodiment is applied. This figure shows an example hardware configuration of a computer used as a control device. This figure shows an example of the functional configuration of the control device. This figure shows an example of the waveform of power input to an air conditioner. This figure shows the power waveform in a power system when the control device does not control the power output by the DC / DC converter, where (a) is an example where the power consumption of the air conditioner is constant, and (b) is an example where the power consumption of the air conditioner pulsates. This figure shows an example of the power waveform in a power system when the control device controls the power output by the DC / DC converter. This figure shows an example configuration of a power system to which the control device according to the second embodiment is applied. This figure shows the power waveform in a power system when the control device does not control the power output by the DC / DC converter, where (a) is an example where the power consumption of the air conditioner is constant, and (b) is an example where the power consumption of the air conditioner pulsates. This figure shows an example of the power waveform in a power system when the control device controls the power output by the DC / DC converter. This figure shows an example of the power waveform in a power system when the difference between power Ppv and power Ppcs includes power pulsation of power Pload. This figure shows an example of a power decoupling circuit. This figure shows another example of a power decoupling circuit. This figure shows an example of a series voltage injector circuit.

[0007] The embodiments will be described in detail below with reference to the attached drawings. (First Embodiment) <Configuration of the Power System> Figure 1 is a diagram showing an example of the configuration of a power system 1 to which the control device 80 according to the first embodiment is applied. The power system 1 comprises a grid-connected inverter 10, a DC link section 20, a capacitor 30, a solar panel 40, a storage battery 50, an air conditioner 60, a detection circuit 70, and a control device 80. The power system 1 is connected to a three-phase AC power supply 100. The three-phase AC power supply 100 is an example of a grid power supply. In the diagram, the grid-connected inverter 10 is denoted as grid-connected INV. The DC link is sometimes denoted as DC link.

[0008] The grid-connected inverter 10 has two input / output sections to which power is input and output. One input / output section of the grid-connected inverter 10 is configured to be connectable to a three-phase AC power supply 100. The other input / output section of the grid-connected inverter 10 is connected to the DC link section 20. The capacitor 30 is connected to the DC link section 20. The solar panel 40 is connected to the DC link section 20 via a DC / DC converter 41. The battery 50 is connected to the DC link section 20 via a DC / DC converter 51. The air conditioner 60 is connected to the DC link section 20. The detection circuit 70 is provided between the DC link section 20 and the air conditioner 60. The AC current path to which the three-phase AC power supply 100 is connected is referred to as the AC line (indicated as the AC line in Figure 1), and the DC current path to which the DC link section 20, solar panel 40, battery 50, and air conditioner 60 are connected is referred to as the DC line (indicated as the DC line in Figure 1). The grid-connected inverter 10 is installed between the AC line and the DC line.

[0009] The grid-connected inverter 10 is an inverter capable of supplying power in both directions. The grid-connected inverter 10 performs forward power flow operation, converting AC power to DC power and supplying power from the three-phase AC power supply 100 to the DC link section 20. It also performs reverse power flow operation, converting DC power to AC power and supplying power from the DC link section 20 to the three-phase AC power supply 100. The grid-connected inverter 10 connects the AC power grid and the DC power grid. The grid-connected inverter 10 is composed of, for example, a voltage-type two-level inverter using six transistors.

[0010] The DC link section 20 is a DC current path, where one of the two current paths is denoted as positive (+) and the other as negative (-). The capacitor 30 is connected between the two current paths of the DC link section 20. The capacitor 30 is, for example, a ceramic capacitor, a film capacitor, an electrolytic capacitor, etc. The DC link section 20 is configured to transmit and receive power to and from the capacitor 30.

[0011] The solar panel 40 converts light energy into electrical energy through the photoelectric effect. The DC / DC converter 41 is installed between the solar panel 40 and the DC link section 20, and converts the DC voltage output by the solar panel 40 into the DC voltage of the DC link section 20 for power transmission. The battery 50 stores electrical energy. The DC / DC converter 51 is installed between the battery 50 and the DC link section 20, and converts the output voltage of the battery 50 into the DC voltage of the DC link section 20 for power transmission. Hereinafter, the DC / DC converter 41 and the DC / DC converter 51 may be simply referred to as "DC / DC converter".

[0012] A DC / DC converter may be configured to perform power conversion in only one direction, converting the DC power input from the primary side into a predetermined DC power and outputting it to the secondary side. Alternatively, a DC / DC converter may be configured to perform power conversion in both directions, in addition to converting the DC power input from the primary side into a predetermined DC power and outputting it to the secondary side, and also converting the DC power input from the secondary side into a predetermined DC power and outputting it to the primary side.

[0013] The circuit configuration of the DC / DC converter is selected from a step-down circuit, a step-up circuit, or a step-up / step-down circuit depending on the voltage value of the connected power supply and DC line. It may also include a power decoupling circuit or a series voltage injector (SVI) that can input a nearly constant DC power from the primary side and output a significantly pulsating DC power from the secondary side. DC / DC converters 41 and 51 are examples of converters. Note that the converter is not limited to a DC / DC converter; it may also be an AC / DC converter connected to an AC power supply that converts AC voltage to DC voltage.

[0014] The air conditioner 60 is connected to the DC link section 20 and consumes DC power supplied from the DC link section 20. The DC link section 20 is configured to transmit power to the air conditioner 60. The air conditioner 60 has a rotating electric motor, and the rotational speed of the rotating electric motor is controlled by making it variable. If the air conditioner 60 is connected to an AC line, an AC / DC converter is required to convert AC to DC. If the air conditioner 60 is connected to the DC link section 20, an AC / DC converter is not required.

[0015] Electrical equipment that includes rotating machinery may have periodic power pulsations in its power consumption due to the rotation of the rotating machinery. If the power consumption pulsations are large, the power fluctuations in the DC link section 20, i.e., the power pulsations, will increase, and there is a risk that the distortion of the power flowing back to the three-phase AC power supply 100 will increase. The air conditioner 60 is an example of electrical equipment. Electrical equipment may also be refrigeration equipment or ventilation equipment. Refrigeration equipment includes, for example, air conditioners, water heaters, chiller units, and cooling equipment that cools the air inside a storage area. Air conditioners may be cooling-only units, heating-only units, or air conditioners that switch between cooling and heating. Cooling equipment cools the air inside refrigerators, freezers, display cases, containers, etc.

[0016] Furthermore, the grid-connected inverter 10, the DC link section 20, the capacitor 30, the control device 80, and the DC / DC converter can be considered as part of a power conditioner. Also, if a refrigeration device is connected as an electrical device to the DC link section 20 in the power conditioner, it can be considered as a heat pump system.

[0017] The air conditioner 60 comprises, for example, a one-cylinder positive displacement compressor and a rotating electric machine. The rotating electric machine drives the positive displacement compressor. The output torque of the rotating electric machine is controlled to match the load torque of the positive displacement compressor. The one-cylinder positive displacement compressor has a suction step, a compression step, and a discharge step in one rotation, and the output torque of the rotating electric machine pulsates once per rotation.

[0018] Power pulsation in rotating machinery can be caused by the structure of the rotating electric machine. For example, harmonic components of the magnetic flux density in the air gap between the rotor and stator of a rotating electric machine cause pulsation at a frequency of rotational speed × number of pole pairs × 6. Also, differences in magnetic resistance between the winding slots and the iron core cause pulsation at a frequency of rotational speed × (least common multiple of the number of slots and the number of poles).

[0019] One example of power pulsation in power consumption from rotating machinery is that caused by the power converter driving the rotating electric machine. For example, when vibration damping control is implemented to control the output torque of the rotating electric machine in accordance with the periodically pulsating load torque, the pulsation occurs at the fundamental frequency of the load torque. The power consumption of the air conditioner 60 pulsates at integer multiples of the rotational speed of the rotating electric machine.

[0020] The detection circuit 70 measures the power consumption of the air conditioner 60 and transmits information about the measured power to the control device 80. The detection circuit 70 may also measure the input power to the air conditioner 60, or it may be configured to measure the DC current supplied from the DC link unit 20. The detection circuit 70 measures the current using, for example, a current sensor, amplifies the signal, and measures the power consumption of the air conditioner 60. The detection circuit 70 transmits information about the measured power to the control device 80. The detection circuit 70 is an example of a DC power measurement unit.

[0021] The control device 80 controls the DC / DC converter that transmits power to the DC link section 20. The DC / DC converters 41 and 51 may be controlled by a single control device 80, or each DC / DC converter may have its own control device 80. The control device 80 may also be configured as an independent device, or it may be incorporated into the DC / DC converter, the grid-connected inverter 10, or the air conditioner 60.

[0022] The control device 80 acquires power pulsations (second power pulsations), which are AC components included in the power input from the DC link unit 20 to the air conditioner 60. The control device 80 adjusts the power pulsations (first power pulsations) superimposed on the DC power output by the DC / DC converter according to the acquired second power pulsations. The control device 80 adjusts the amplitude difference and phase difference between the second power pulsations and the first power pulsations by, for example, adding an AC component to the DC power output by the DC / DC converter, which matches the amplitude and phase information of the second power pulsations. The functional configuration of the control device 80 will be described in detail later.

[0023] Figure 1 defines the names of the powers and the direction in which the power is supplied to each device. In Figure 1, the direction in which the power is supplied is indicated by an arrow. The power when the grid-connected inverter 10 performs reverse power flow operation is denoted as power Ppcs. Power Ppcs is defined as positive (+) when supplied from the DC link section 20 to the three-phase AC power supply 100. Power Ppcs is an example of the fourth DC power.

[0024] The power supplied to the capacitor 30 is denoted as power PC. The direction in which power PC is supplied from the DC link section 20 to the capacitor 30 is considered positive (+). Power PC is an example of third DC power. The power transmitted by the DC / DC converter 41 is denoted as power Ppv. The direction in which power Ppv is supplied from the solar panel 40 to the DC link section 20 is considered positive (+). Power Ppv is an example of first DC power.

[0025] The power transmitted by the DC / DC converter 51 is denoted as Power Pbattery. The direction in which Power Pbattery is supplied from the battery 50 to the DC link section 20 is considered positive (+). If Power Pbattery is positive (+), the battery 50 is discharging; if it is negative (-), the battery 50 is charging. Power Pbattery is an example of the first DC power. The power consumed by the air conditioner 60 is denoted as Power Pload. The direction in which Power Pload is supplied from the DC link section 20 to the air conditioner 60 is considered positive (+). Power Pload is an example of the second DC power.

[0026] Figure 2 shows an example of the hardware configuration of a computer 800 used as a control device 80. The computer 800 includes a CPU (Central Processing Unit) 801, a RAM (Random Access Memory) 802, and a ROM (Read Only Memory) 803. The RAM 802 is a volatile memory used as a work area when the CPU 801 executes a program. The ROM 803 is a non-volatile memory that stores the program executed by the CPU 801 and other data. The CPU 801 uses the RAM 802 as a work area and executes the program read from the ROM 803. The computer 800 also includes an IF (interface) 804 for communication.

[0027] <Functional Configuration of the Control Device> Figure 3 shows an example of the functional configuration of the control device 80. The control device 80 includes a pulsation information acquisition unit 81, a pulsation identification unit 82, an output determination unit 83, and a signal transmission unit 84, as functions executed by the CPU 801, which is a processor.

[0028] The pulsation information acquisition unit 81 acquires information regarding the second power pulsation, which is an AC component included in the power load (hereinafter referred to as "power pulsation information"). The pulsation information acquisition unit 81 acquires power pulsation information from, for example, the detection circuit 70. The power pulsation information is, for example, the power load measured by the detection circuit 70.

[0029] Furthermore, the pulsation information acquisition unit 81 may acquire power pulsation information from the air conditioner 60. In this case, the air conditioner 60 is equipped with a communication unit that transmits power pulsation information to the control device 80. The functions of the communication unit are performed by a hardware configuration similar to that of the computer 800 shown in Figure 2. The power pulsation information is, for example, information related to the operating state of the air conditioner 60, such as the rotation angle of the rotating electric machine and the amplitude of the power pulsation, or information for identifying a second power pulsation, such as values ​​correlated therewith. Alternatively, the communication unit of the air conditioner 60 may be configured to transmit a second power pulsation estimated from the operating state of the air conditioner 60 or identified by frequency analysis of the air conditioner 60. In this case, the control device 80 does not need to have a pulsation identification unit 82, and the processing load on the control device 80 is reduced.

[0030] Furthermore, the pulsation information acquisition unit 81 may be configured to acquire power pulsation information from both the detection circuit 70 and the air conditioner 60. The pulsation information acquisition unit 81 acquires the power Pload measured from the detection circuit 70. The pulsation information acquisition unit 81 also acquires information regarding the operating status of the air conditioner 60 from the air conditioner 60.

[0031] The pulsation identification unit 82 identifies the second power pulsation based on the power pulsation information acquired by the pulsation information acquisition unit 81. For example, when the pulsation information acquisition unit 81 acquires the power Pload measured from the detection circuit 70, the pulsation identification unit 82 performs frequency analysis on the power Pload to identify the second power pulsation. The frequency analysis is, for example, a short-time Fourier transform using a window function. In the short-time Fourier transform, the power consumption over a predetermined time is extracted and the Fourier transform is performed. The predetermined time may be, for example, an integer multiple of the period of the three-phase AC power supply 100, which is the grid power supply.

[0032] When the pulsation information acquisition unit 81 acquires power pulsation information from both the detection circuit 70 and the air conditioner 60, the pulsation identification unit 82 performs frequency analysis on the power Pload based on information regarding the operating state of the air conditioner 60 to identify the second power pulsation. The pulsation identification unit 82 performs a short-time Fourier transform using a window function based on information regarding the operating state of the air conditioner 60, for example. In this case, as the window function, for example, a window function that extracts the power consumption over time corresponding to the rotational speed of a rotating electric machine is used. Alternatively, for example, a window function that extracts the power consumption at integer multiples of the reciprocal of the rotational speed corresponding to the time of one cycle is used. The pulsation information acquisition unit 81 and the pulsation identification unit 82 are examples of pulsation acquisition units.

[0033] The output determination unit 83 determines a first power pulsation superimposed on the DC power output by the DC / DC converter based on the second power pulsation. The output determination unit 83 determines the first power pulsation such that the third power pulsation, which is an AC component included in the power PC supplied to the capacitor 30, is reduced. The third power pulsation pulsates at the same frequency as the second power pulsation. As a result, the power pulsation absorbed by the capacitor 30 is reduced, and voltage fluctuations in the DC line are suppressed. In addition, the power pulsation of the power consumption of the air conditioner 60 does not need to be absorbed by the capacitor 30, the heat generated by the capacitor 30 due to power pulsation is suppressed, and the reduction in the lifespan of the capacitor 30 is suppressed.

[0034] The output determination unit 83 may determine the first power pulsation, for example, so as to approach the second power pulsation. Alternatively, the output determination unit 83 may determine the first power pulsation in accordance with the power pulsation (fourth power pulsation) of the fourth DC power (Ppcs), which is a frequency component twice the frequency of the three-phase AC power supply 100, which is the grid power supply. In this case, the control device 80 adjusts the first power pulsation to a frequency component twice the frequency of the three-phase AC power supply 100. The signal transmission unit 84 outputs a control signal to the DC / DC converter that superimposes the determined first power pulsation.

[0035] <Example> Figure 4 shows an example of the waveform of power input to the air conditioner 60. The vertical axis represents power (W), and the horizontal axis represents time (sec). The air conditioner 60 is equipped with a rotating electric machine, and the power consumption of the air conditioner 60 pulsates due to the rotating electric machine. The power Pload input to the air conditioner 60 is expressed as the sum of the steady-state component Pload_dc and the pulsating component Pload_fluctuate. In Figure 4, the power input to the air conditioner 60 is shown when the load torque fluctuates at a fundamental frequency of 20 Hz, and vibration damping control is implemented to control the output torque of the rotating electric machine in accordance with the fluctuation of the load torque.

[0036] An example of control of the DC / DC converter by the control device 80 will be explained using Figures 5 and 6. For simplicity, this explanation will describe a case where the power system 1 does not include a battery 50 and a DC / DC converter 51. In this example, the control device 80 controls the power output of the DC / DC converter 41, thereby suppressing voltage fluctuations in the DC line.

[0037] Figure 5 shows the power waveform in the power system 1 when the control device 80 does not control the power output of the DC / DC converter 41. Figure 5(a) shows an example where the power consumption of the air conditioner 60 is constant, and Figure 5(b) shows an example where the power consumption of the air conditioner 60 pulsates. The vertical axis represents power (W), and the horizontal axis represents time (sec). In Figure 5, the power Ppv output by the DC / DC converter 41 is shown by a solid line. The power Ppcs input to the grid-connected inverter 10 is shown by a dashed line. The power PC supplied to the capacitor 30 is shown by a double-dash line. The power Pload input to the air conditioner 60 is shown by a dashed line.

[0038] The power system 1 is connected to a three-phase AC power supply 100, and the input power Ppcs on the DC line side of the grid-connected inverter 10 is constant. The power Ppcs input to the grid-connected inverter 10 is controlled to be the DC component of the difference between the power Ppv output by the DC / DC converter 41 and the power Pload input to the air conditioner 60.

[0039] As shown in Figure 5(a), when the power consumption Pload of the air conditioner 60 is constant, the power PC supplied to the capacitor 30 is always 0W. In the example shown in Figure 5(a), the power Ppv is constant at 1500W, the power Pload is constant at 500W, and the power Ppcs is constant at 1000W. On the other hand, when the power consumption Pload of the air conditioner 60 pulsates, as shown in Figure 5(b), a power pulsation in the power PC supplied to the capacitor 30 occurs that is in the opposite phase to the power pulsation of the power Pload. Power pulsation of the power PC supplied to the capacitor 30 is a factor that causes pulsation of the capacitor voltage and reduces the lifespan of the capacitor 30.

[0040] Figure 6 shows an example of a power waveform in the power system 1 when the control device 80 controls the power output of the DC / DC converter 41. The vertical axis represents power (W), and the horizontal axis represents time (sec). In Figure 6, the power Ppv output by the DC / DC converter 41 is shown by a solid line. The power Ppcs input to the grid-connected inverter 10 is shown by a dashed line. The power PC supplied to the capacitor 30 is shown by a double-dash line. The power Pload input to the air conditioner 60 is shown by a dashed line.

[0041] The control device 80 controls the power output of the DC / DC converter 41 so that the power Ppv supplied by the DC converter 41 to the DC line includes the power pulsation of the power consumption Pload of the air conditioner 60. As a result, as shown in Figure 6, the input power PC to the capacitor 30 is always 0W, suppressing voltage fluctuations in the DC line and reducing the lifespan of the capacitor 30.

[0042] Furthermore, if a battery 50 and a DC / DC converter 51 are provided, the configuration may be such that it is possible to select which DC / DC converter to use to compensate for the power pulsation of the power consumption Pload of the air conditioner 60. Also, if there are multiple DC / DC converters, the configuration may be such that power pulsation is compensated by one DC / DC converter, or by multiple DC / DC converters.

[0043] (Second Embodiment) FIG. 7 is a diagram showing a configuration example of the power system 2 to which the control device 80 according to the second embodiment is applied. Hereinafter, the same components as those in the first embodiment will be described using the same reference numerals. The power system 2 includes a grid-connected inverter 10, a DC link section 20, a capacitor 30, a solar panel 40, a storage battery 50, an air conditioner 60, a detection circuit 70, and a control device 80. The power system 2 is different from the power system 1 in that it is connected to a single-phase AC power source 200 via the grid-connected inverter 10. The single-phase AC power source 200 is an example of a grid power source. The grid-connected inverter 10 is composed of, for example, a full-bridge circuit in which four transistors are arranged in a bridge shape.

[0044] An example of the control of the DC / DC converter by the control device 80 will be described using FIGS. 8 and 9. Here, for the sake of simplicity, a case where the power system 2 does not include the storage battery 50 and the DC / DC converter 51 will be described. In this example, the control device 80 controls the power output by the DC / DC converter 41, and the voltage fluctuation of the DC line is suppressed.

[0045] FIG. 8 is a diagram showing the power waveforms in the power system 2 when the control device 80 does not control the power output by the DC / DC converter 41. (a) shows an example when the power consumption of the air conditioner 60 is constant, and (b) shows an example when the power consumption of the air conditioner 60 pulsates. The vertical axis represents power (W), and the horizontal axis represents time (sec). In FIG. 8, the power Pp v output by the DC / DC converter 41 is shown by a solid line. The power Pp cs input to the grid-connected inverter 10 is shown by a one-dot chain line. The power PC supplied to the capacitor 30 is shown by a two-dot chain line. The power P load input to the air conditioner 60 is shown by a broken line.

[0046] The DC component of the power Ppcs input to the system connection inverter 10 is controlled to be the DC component of the difference between the power Ppv output by the DC / DC converter 41 and the power Pload input to the air conditioner 60. The power system 2 is connected to a single-phase AC power supply 200, and the input power Ppcs on the DC line side of the system connection inverter 10 pulsates at a frequency twice that of the power supply frequency of the single-phase AC power supply 200. Here, the power supply frequency of the single-phase AC power supply 200 is set to 50 Hz. In this case, the input power Ppcs pulsates at a frequency of 100 Hz.

[0047] As shown in Fig. 8(a), when the power consumption Pload of the air conditioner 60 is constant, a power pulsation opposite in phase to the power pulsation of the power Ppcs occurs in the power PC supplied to the capacitor 30. On the other hand, when the power consumption Pload of the air conditioner 60 pulsates, as shown in Fig. 8(b), a power pulsation is generated in the power PC supplied to the capacitor 30, which is the sum of the power pulsation opposite in phase to the power pulsation of the power Pload and the power pulsation opposite in phase to the power pulsation of the power Ppcs.

[0048] Fig. 9 is a diagram showing an example of the power waveform in the power system 2 when the control device 80 controls the power output by the DC / DC converter 41. The vertical axis represents power (W), and the horizontal axis represents time (sec). The control device 80 controls the power output by the DC / DC converter 41 so that the power pulsation of the power consumption Pload of the air conditioner 60 is included in the power Ppv supplied by the DC / DC converter 41 to the DC line. As a result, as shown in Fig. 9, the pulsation component caused by the power pulsation of the power consumption Pload of the air conditioner 60 is removed from the input power PC to the capacitor 30, and the voltage fluctuation of the DC line and the reduction in the life of the capacitor 30 are suppressed.

[0049] (Modification of the Second Embodiment) In the power system 2, the control device 80 may be configured to control the power output by the DC / DC converter 41 so that the power pulsation of the power Pload is included in the difference between the power Ppv and the power Ppcs. In other words, the control device 80 may control the power output by the DC / DC converter 41 so that both the power pulsation of the power Pload and the power pulsation of the power Ppcs are included in the power Ppv.

[0050] Figure 10 shows an example of a power waveform in power system 2 when the difference between power Ppv and power Ppcs includes the power pulsation of power Pload. The vertical axis represents power (W), and the horizontal axis represents time (sec). As shown in Figure 10, when the power Ppv supplied by the DC / DC converter 41 to the DC line includes both the power pulsation of power Pload and the power pulsation of power Ppcs, the power pulsation of power PC input to capacitor 30 becomes zero. This suppresses voltage fluctuations in the DC line and reduces the lifespan of capacitor 30.

[0051] The power pulsation component of the power Ppcs input to the grid-connected inverter 10 can be estimated, for example, from the AC voltage, AC current, and phase output by the grid-connected inverter 10 to the AC line. Alternatively, the system may be equipped with a mechanism to measure the output power of the grid-connected inverter 10, and the power pulsation component may be identified by frequency analysis of the measured output power.

[0052] (Variations of DC / DC converters) As mentioned above, DC / DC converters may also include power decoupling circuits, series voltage injector circuits, and the like.

[0053] Figure 11 shows an example of a power decoupling circuit. The power decoupling circuit shown in Figure 11 is a boost-type active buffer circuit 101. The active buffer circuit 101 is connected in parallel to the DC power supply 110. The DC power supply 110 may be, for example, a solar panel or a storage battery. The active buffer circuit 101 includes a boost chopper 1011, a buffer capacitor 1012, and a filter capacitor 1013. The active buffer circuit 101 adjusts the pulsation of DC power by adjusting the voltage of the buffer capacitor 1012. The voltage of the buffer capacitor 1012 is adjusted by the boost chopper 1011. The filter capacitor 1013 filters ripple current and the like generated by the grid-connected inverter 10 (see Figure 1). Note that the active buffer circuit 101 may also be configured without the filter capacitor 1013.

[0054] Figure 12 shows another example of a power decoupling circuit. The power decoupling circuit shown in Figure 12 is a step-down active buffer circuit 102. The active buffer circuit 102 is connected in parallel to the DC power supply 120. The DC power supply 120 may be, for example, a solar panel or a storage battery. The active buffer circuit 102 includes a step-down chopper 1021, a buffer capacitor 1022, and a filter capacitor 1023. The active buffer circuit 102 adjusts the pulsation of the DC power by adjusting the voltage of the buffer capacitor 1022. The voltage of the buffer capacitor 1022 is adjusted by the step-down chopper 1021. The filter capacitor 1023 filters ripple currents and the like that generated in the grid-connected inverter 10 (see Figure 1). Note that the active buffer circuit 102 may also be configured without the filter capacitor 1023.

[0055] Figure 13 shows an example of a series voltage injector circuit. The series voltage injector circuit 103 is connected in series with a DC power supply 130. The DC power supply 130 may be, for example, a solar panel or a storage battery. The series voltage injector circuit 103 includes a capacitor 1031, an inductor 1032, a switch circuit 1033, and a buffer capacitor 1034. The series voltage injector circuit 103 adjusts the pulsation of DC power by adjusting the voltage of the capacitor 1031 connected in series with the DC power supply 130. The voltage of the capacitor 1031 is adjusted by the switch circuit 1033. In Figure 13, the inductor 1032 is provided to be connected to one end of the capacitor 1031, but it may also be provided to be connected to the other end of the capacitor 1031. Alternatively, an inductor 1032 connected to one end of the capacitor 1031 and an inductor 1032 connected to the other end of the capacitor 1031 may be provided separately. Note that the circuits shown in Figures 11 to 13 are examples only and are not limited to these.

[0056] Furthermore, the circuit configuration of the DC / DC converter may include a step-down circuit, a boost circuit, or a step-up / step-down circuit, along with a power decoupling circuit or a series voltage injector circuit. For example, the circuit configuration of the DC / DC converter may include a boost circuit and a power decoupling circuit. For example, the circuit configuration of the DC / DC converter may include a step-up / step-down circuit and a series voltage injector circuit.

[0057] <Effects> The control device 80 of the present disclosure is a control device 80 that controls one or more converters that transmit a first DC power Ppv to a DC link unit 20, wherein the first DC power Ppv includes a first power pulsation which is an AC component, the DC link unit 20 is configured to transmit a second DC power Pload to an air conditioner 60 connected to the DC link unit 20, and the control device 80 includes a pulsation information acquisition unit 81 that acquires a second power pulsation which is an AC component included in the second DC power Pload, and adjusts the first power pulsation according to the second power pulsation acquired by the pulsation information acquisition unit 81. In this case, the power pulsation of the DC link unit 20 caused by fluctuations in the power consumption of the air conditioner 60 connected to the DC link unit 20 can be adjusted. Here, the DC link section 20 is configured to transmit and receive a third DC power PC with a capacitor 30 connected to the DC link section 20, and the control device 80 adjusts the first power pulsation so that the third power pulsation, which is an AC component included in the third DC power PC, is reduced. In this case, the reduction in the lifespan of the capacitor 30 can be suppressed. Furthermore, the control device 80 of this disclosure adjusts the amplitude difference and phase difference between the second power pulsation and the first power pulsation. In this case, the adjustment of the power pulsation becomes easier. Furthermore, the control device 80 of this disclosure adjusts the first power pulsation so that it approaches the second power pulsation. In this case, the power pulsation component can be canceled out. Furthermore, the DC link section 20 is configured to transmit and receive a fourth DC power Ppcs between itself and a grid-connected inverter 10 connected to the DC link section 20 and a single-phase AC power supply 200. The control device 80 adjusts the first power pulsation by a frequency component twice the frequency of the single-phase AC power supply 200 in response to the fourth power pulsation of the fourth DC power Ppcs, which is a frequency component twice the frequency of the grid power supply. In this case, the power pulsation component generated in the grid-connected inverter 10 can be adjusted. In addition, at least one of the converters is connected to a power supply and converts the power of the power supply into the first DC power Ppv. In this case, the power pulsation of the DC link section 20 caused by fluctuations in the power consumption of the air conditioner 60 connected to the DC link section 20 can be adjusted.Furthermore, the pulsation information acquisition unit 81 acquires information correlated with the second power pulsation from the air conditioner 60. In this case, the calculation processing can be shared between the air conditioner 60 and the control device 80. Also, the pulsation information acquisition unit 81 acquires the second DC power Pload from the detection circuit 70 that measures the second DC power Pload. In this case, the second DC power Pload can be easily acquired even if there are multiple air conditioners 60. Furthermore, the air conditioner 60 includes a rotating electric machine. In this case, the power pulsation caused by the rotation of the rotating electric machine can be adjusted. Furthermore, the second power pulsation pulsates at integer multiples of the rotational speed of the rotating electric machine. In this case, the power pulsation caused by the rotation of the rotating electric machine can be adjusted. Furthermore, the power conditioner of this disclosure comprises a control device 80 as described in claims 1 to 10, one or more converters controlled by the control device 80, a DC link section 20 to which the converters are connected and to which an air conditioner 60 can be connected, and a grid-connected inverter 10 connected to the DC link section 20 and configured to be connected to a grid power supply. In this case, the power pulsation of the DC link section 20 caused by fluctuations in the power consumption of the air conditioner 60 connected to the DC link section 20 can be adjusted. Furthermore, the heat pump system of this disclosure, in the power conditioner as described in claim 11, includes a refrigeration device as the electrical equipment. In this case, the power pulsation of the DC link section 20 caused by fluctuations in the power consumption of the electrical equipment connected to the DC link section 20 can be adjusted. Furthermore, the air conditioner 60 of this disclosure is an air conditioner 60 connected to a DC link section 20, the DC link section 20 is controlled by a control device 80 and connected to one or more converters that transmit a first DC power Ppv to the DC link section 20, the first DC power Ppv includes a first power pulsation which is an AC component, the DC link section 20 is configured to transmit a second DC power Pload to the air conditioner 60, the control device 80 includes a pulsation information acquisition unit 81 that acquires a second power pulsation which is an AC component included in the second DC power Pload, and is configured to adjust the first power pulsation according to the second power pulsation acquired by the pulsation information acquisition unit 81, and the air conditioner 60 includes a communication unit that transmits information correlated with the second power pulsation to the pulsation information acquisition unit 81.In this case, the power pulsation of the DC link section 20 caused by fluctuations in the power consumption of the air conditioner 60 connected to the DC link section 20 can be adjusted. Furthermore, the air conditioner 60 in this disclosure is a refrigeration device.

[0058] Although embodiments have been described above, the technical scope of this disclosure is not limited to the embodiments described above. It is clear from the claims that combinations of two or more of the above embodiments, as well as various modifications or improvements to the above embodiments, are also included in the technical scope of this disclosure.

[0059] 10...Grid-connected inverter, 20...DC link section, 30...Capacitor, 40...Solar panel, 50...Battery, 60...Air conditioner, 70...Detection circuit, 80...Control device, 100...Three-phase AC power supply, 200...Single-phase AC power supply

Claims

1. A control device for controlling one or more converters that transmit first DC power to a DC link section, wherein the first DC power includes a first power pulsation which is an AC component, the DC link section is configured to transmit second DC power to electrical equipment connected to the DC link section, and the control device includes a pulsation acquisition unit that acquires a second power pulsation which is an AC component included in the second DC power, and the control device adjusts the first power pulsation according to the second power pulsation acquired by the pulsation acquisition unit.

2. The control device according to claim 1, wherein the DC link section is configured to transmit and receive third DC power with a capacitor connected to the DC link section, and the control device adjusts the first power pulsation so that the third power pulsation, which is an AC component included in the third DC power, is reduced.

3. The control device according to claim 1 or 2, wherein the control device adjusts the amplitude difference and phase difference between the second power pulsation and the first power pulsation.

4. The control device according to any one of claims 1 to 3, wherein the control device adjusts the first power pulsation so that it approaches the second power pulsation.

5. The control device according to any one of claims 1 to 4, wherein the DC link section is configured to transmit and receive a fourth DC power between the DC link section and a grid-connected inverter connected to a single-phase grid power supply, and the control device adjusts the frequency component of the first power pulsation to twice the frequency of the grid power supply in response to the fourth power pulsation of the fourth DC power, which is twice the frequency component of the grid power supply.

6. The control device according to any one of claims 1 to 5, wherein at least one of the converters is connected to a power supply and converts the power of the power supply into the first DC power.

7. The control device according to any one of claims 1 to 6, wherein the pulsation acquisition unit acquires information correlated with the second power pulsation from the electrical equipment.

8. The control device according to any one of claims 1 to 7, wherein the pulsation acquisition unit acquires the second DC power from the DC power measuring unit that measures the second DC power.

9. The control device according to any one of claims 1 to 8, wherein the electrical equipment includes a rotating electric machine.

10. The control device according to claim 9, wherein the second power pulsation pulsates at an integer multiple of the rotational speed of the rotating electric machine.

11. A power conditioner comprising: a control device according to any one of claims 1 to 10; one or more converters controlled by the control device; a DC link section to which the converters are connected and to which electrical equipment can be connected; and a grid-connected inverter connected to the DC link section and to which grid power can be connected.

12. A heat pump system comprising a refrigeration device as the electrical equipment in the power conditioner according to claim 11.

13. An electrical device connected to a DC link section, wherein the DC link section is controlled by a control device and connected to one or more converters that transmit first DC power to the DC link section, the first DC power includes a first power pulsation which is an AC component, the DC link section is configured to transmit second DC power to the electrical device, the control device includes a pulsation acquisition unit that acquires a second power pulsation which is an AC component included in the second DC power, the control device is configured to adjust the first power pulsation according to the second power pulsation acquired by the pulsation acquisition unit, and the electrical device includes a communication unit that transmits information correlated with the second power pulsation to the pulsation acquisition unit.

14. The electrical equipment according to claim 13, wherein the electrical equipment is a refrigeration device.

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