Power conversion device, power supply system, and control method

Abstract

To provide a power conversion device capable of changing a push-up effect presence mode to a push-up effect absence mode without changing a position of a current measurement device, a power supply system, and a control method.SOLUTION: A power conversion device includes an inverter converting DC power outputted from a photovoltaic power generation device and a power storage device into AC power to be outputted to a load and a system, and a control unit controlling the inverter. The control unit further specifies a power consumption state of the load based on current of the inverter and current in a linkage point connecting the inverter and the system, and controls charging / discharging of the power storage device based on the specified power consumption state of the load, a power generation state of the photovoltaic power generation device, and a power demand state of the system.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a power converter, a power supply system, and a control method. [Background Art]

[0002] A hybrid power supply system is known that includes a solar power generation system and a power storage system that stores generated power exceeding the power supplied to a load (i.e., surplus power) in a storage battery. The hybrid power supply system is capable of grid interconnection, such as supplying the generated power to the grid in accordance with the power generation status of the solar power generation system.

[0003] FIG. 1 shows a conventional hybrid power supply system. Referring to FIG. 1, a power converter 900 includes a PV converter 904 connected to a PV (Photovoltaic) panel 902, a storage battery converter 908 connected to a storage battery 906, and an inverter 910 connected to the PV converter 904 and the storage battery converter 908.

[0004] The PV converter 904 is controlled by a control unit (not shown), boosts the DC voltage output from the PV panel 902, and outputs the boosted DC voltage to the inverter 910. The storage battery converter 908 is controlled by the control unit, boosts the DC voltage output from the storage battery 906, and outputs the boosted DC voltage to the inverter 910. The storage battery converter 908 is capable of bidirectional power conversion, converts surplus power output from the PV converter 904 (i.e., surplus power), and charges the storage battery 906. The inverter 910 is controlled by the control unit, converts the input DC voltage into an AC voltage, and outputs the AC voltage to a relay 914. When the relay 914 is turned on (short-circuited), the power converter 900 supplies power to a load 922. Further, the inverter 910 is capable of bidirectional power conversion, monitors a current value with a current sensor 916, and enables grid interconnection with a grid 920.

[0005] While the power generated by the PV panel 902, i.e., the output power of the PV converter 904, can be reverse-flowed, the discharge power of the battery 906, i.e., the output power of the battery converter 908, is currently prohibited from being reverse-flowed. The power converter 900 calculates power based on the current value detected by the current sensor 916 and performs load-following control to prevent reverse power flow to the grid 920. For example, if the power generated by the PV panel 902 is 0W and the power consumed by the load 922 is 3000W, it is prohibited to discharge 4000W from the battery 906, supply 3000W to the load 922, and supply the remaining 1000W from the power converter to the grid 920 (i.e., reverse power flow). If the responsiveness of the load-following control is insufficient and reverse power flow occurs, the power converter 900 is required to stop using its reverse power prevention function. Specifically, the permissible range for reverse power flow is 5% or less of the rated power of the inverter 910 and for a period of 0.5 seconds or less. In other words, the power converter 900 must have a function to stop operating if the reverse power flow exceeds 5% of the rated power of the inverter 910 for more than 0.5 seconds.

[0006] The load-following control by the battery 906 and the battery converter 908 has an upward pushing effect. Push-up effect There are two operating modes: one without an upward effect. In the operating mode without an upward effect, the battery 906 discharges only the difference between the power consumption of the load 922 and the power generated by the PV panel 902 (i.e., power is supplied from the battery converter 908). If the power generated by the PV panel 902 is greater than the power consumption of the load 922, the battery 906 does not discharge (i.e., power is not supplied from the battery converter 908). Referring to Figure 2, an example of power supply in the operating mode without an upward effect in the configuration shown in Figure 1 is indicated by arrows with power values. For example, if the power generated by the PV panel 902 is 2000W and the power consumption of the load 922 is 3000W, the battery 906 (i.e., the battery converter 908) will discharge the difference, which is 1000W for the power converter.

[0007] Specifically, referring to Figure 2, the instantaneous value of the reverse power flow for each of the two phases of the single-phase three-wire system is calculated using Equation 1 below. These calculated values ​​are then added together and averaged over one AC cycle to calculate the total phase power. The calculated total phase power is considered to be the reverse power flow. Instantaneous value of reverse power flow = System voltage × System current ... (Equation 1) Here, the system voltage is the voltage value of the system 920, and the system current is the current value detected by the current sensor 916. Feedback control is then performed to adjust the discharge power of the battery 906 so that the reverse power flow becomes 0. If the reverse power flow exceeds the allowable range at this time, the reverse power prevention function is activated as described above.

[0008] In the operation mode with the push-up effect, the same amount of power as the power consumed by the load 922 is discharged from the battery 906 (i.e., power is supplied from the battery converter 908), and all of the power generated by the PV panel 902 is supplied to the grid 920 (i.e., sold). Figure 3 shows the configuration of the power supply system when the operation mode with the push-up effect is executed. The configuration in Figure 3 is the same as the configurations in Figures 1 and 2, except that the position of the current sensor 916 has been changed. That is, in Figure 3, the current sensor 916 measures the current supplied to the load 922. Referring to Figure 3, for example, if the power generated by the PV panel 902 is 2000W and the power consumed by the load 922 is 3000W, then 3000W is discharged from the battery 906 (i.e., from the battery converter 908), and all of the power generated by the PV panel 902 (i.e., 2000W) is supplied to the grid 920.

[0009] Specifically, referring to Figure 3, for each of the two phases of the single-phase three-wire system, the instantaneous power consumption of the load 922 is calculated using Equation 2 below, and these calculated values ​​are added together and averaged over one AC cycle to obtain the power consumption of the load 922. In addition, the instantaneous discharge power of the battery 906 is calculated using Equation 3 below, and averaged over the same period as the above AC cycle to calculate the discharge power of the battery 906. Instantaneous power consumption = System voltage × Current consumption ... (Equation 2) Instantaneous discharge power = Battery voltage × Battery current ... (Equation 3) Here, the grid voltage is the voltage value of grid 920, and the current consumption is the current value detected by the current sensor 916. The battery voltage and battery current are the output voltage value and output current value of the battery converter 908, respectively. Feedback control is then performed to adjust the discharge power of battery 906 so that the discharge power of battery 906 matches the power consumption of load 922. At this time, if the reverse power flow exceeds the allowable range (i.e., if the discharge power of battery 906 exceeds the power consumption of load 922), the reverse power prevention function is activated as described above.

[0010] For example, Patent Document 1 discloses a power generation system that adds a control device for controlling an inverter and a converter to the configuration shown in Figure 3. This power generation system includes a household load power measurement unit for measuring the power supplied from the inverter to the household load, and is capable of operating in an operating mode with a push-up effect. [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2014-230455 [Overview of the project] [Problems that the invention aims to solve]

[0012] The operating modes described above, with and without the upward pressure effect, are determined by the contract between the power company and the consumer (e.g., each household). The amount of money sold for surplus electricity is calculated at the unit price (i.e., the purchase price) determined by the contract. The purchase price can change. For example, the purchase price will be lower than during the Feed-in Tariff (FIT) period after the FIT period has expired. After the FIT period has expired, the purchase price will be determined by individual free contracts. For consumers, a contract without the upward pressure effect is advantageous if the purchase price of surplus electricity is low, and a contract with the upward pressure effect is advantageous if the purchase price of surplus electricity is high. Therefore, consumers may consider switching between contracts with and without the upward pressure effect after initially operating a hybrid power supply system.

[0013] In order to measure the power of the monitored device as directly as possible, it is natural to position the current sensor 916 as shown in Figures 1 and 2 in the operating mode without the push-up effect, and as shown in Figure 3 in the operating mode with the push-up effect. In this case, however, a change in contract would necessitate work by the contractor to change the position of the current sensor 916, which is cumbersome. Furthermore, there is the problem of human error occurring during installation. For example, when using a CT (Current Transformer) as the current sensor 916, a CT is installed on each of the two wires excluding the neutral wire of the single-phase three-wire system on the primary side of the contract breaker. When installing the CT, it is necessary to install it in the correct orientation and tighten it until it is securely locked. However, in reality, human error such as improper installation of the CT and its detachment after installation can occur.

[0014] Therefore, this disclosure provides a mode with an upward effect without changing the position of the current measuring device. Push-up effect The objective is to provide a power conversion device, power supply system, and control method that can switch between a no-effect mode and a power-off mode. [Means for solving the problem]

[0015] A power conversion device according to a certain aspect of the present disclosure includes an inverter that converts DC power output from a photovoltaic power generation device and an energy storage device into AC power and outputs it to a load and a grid, and a control unit that controls the inverter, the control unit further identifies the power consumption state of the load based on the current of the inverter and the current at the interconnection point connecting the inverter and the grid, and controls the charging and discharging of the energy storage device based on the identified power consumption state of the load, the power generation state of the photovoltaic power generation device and the power supply and demand state of the grid.

[0016] A power supply system relating to another aspect of this disclosure includes a photovoltaic power generation device that outputs DC power, a rechargeable energy storage device, and the power converter that converts the DC power output from the photovoltaic power generation device and the energy storage device into AC power and outputs it to the load and the grid.

[0017] A control method relating to yet another aspect of the present disclosure is a control method for a power conversion device including an inverter and a control unit, comprising: a power supply step in which the control unit converts DC power output from a photovoltaic power generation device and an energy storage device into AC power using an inverter and outputs it to a load and a grid; and a step in which the control unit obtains a measured current from a current measuring device that measures the current at the interconnection point connecting the inverter and the grid, wherein the power supply step includes a step of identifying the power consumption state of the load based on the current of the inverter and the current measured by the current measuring device; and a step of controlling the charging and discharging of the energy storage device based on the identified power consumption state of the load, the power generation state of the photovoltaic power generation device and the power supply and demand state of the grid. [Effects of the Invention]

[0018] According to this disclosure, the push-up effect mode can be achieved without changing the position of the current measuring device. Push-up effect We can provide a power converter, power supply system, and control method that can switch between a no-effect mode and a power-off mode. [Brief explanation of the drawing]

[0019] [Figure 1]FIG. 1 is a block diagram showing the configuration of a hybrid power supply system including a conventional power converter. [Figure 2] FIG. 2 is a block diagram showing an operation mode without a voltage step-up effect in the hybrid power supply system shown in FIG. 1. [Figure 3] FIG. 3 is a block diagram showing the configuration of a hybrid power supply system that includes a conventional power converter and has a voltage step-up effect. [Figure 4] FIG. 4 is a block diagram showing the configuration of a hybrid power supply system including the power converter according to an embodiment of the present disclosure. [Figure 5] FIG. 5 is a flowchart showing processing performed by the control unit shown in FIG. 4. [Figure 6] FIG. 6 is a block diagram showing the configuration of a hybrid power supply system including a power converter according to a modification. [Figure 7] FIG. 7 is a block diagram showing the configuration of a hybrid power supply system in which a current sensor is housed in a casing separate from the power converter. DETAILED DESCRIPTION OF THE INVENTION

[0020] Description of Embodiments of the Present Disclosure The content of embodiments of the present disclosure will be listed and described. At least a part of the embodiments described below may be arbitrarily combined.

[0021] (1) The power converter according to the first aspect of the present disclosure includes an inverter that converts DC power output from a photovoltaic power generation device and an energy storage device into AC power and outputs it to a load and the grid, and a control unit that controls the inverter. The control unit further identifies the power consumption state of the load based on the current of the inverter and the current at the interconnection point connecting the inverter and the grid, and controls the charging and discharging of the energy storage device based on the identified power consumption state of the load, the power generation state of the photovoltaic power generation device, and the power supply and demand state of the grid. As a result, the power converter can control the charging and discharging of the energy storage device according to the power supply and demand state of the grid by changing the software alone, without changing the position of the current measuring device. Therefore, it becomes possible to switch the operating mode to one that has a push-up effect during times when the power of the grid is tight, thereby increasing the reverse power flow and contributing to the resolution of power shortages.

[0022] (2) In (1) above, the control unit may control the charging and discharging of the energy storage device based on a first mode, which is one of a plurality of operating modes based on the contract with the power company, and may, upon receiving instructions from an external source, control the charging and discharging of the energy storage device based on a second mode, which is different from the first mode, from among the plurality of operating modes. This allows the power converter to change its operating mode without changing the position of the current measuring device, even if the operating mode is changed due to a change in the contract with the power company.

[0023] (3) In (1) or (2) above, the first mode may be an operating mode with an upward pushing effect, and the second mode may be an operating mode without an upward pushing effect. This allows the power converter to operate in an operating mode with an upward pushing effect without changing the position of the current measuring device. Push-up effect The operating mode can be switched between a mode without an effect and a mode without an effect.

[0024] (4) In any one of (1) to (3) above, the power converter further includes a housing that houses an inverter and a control unit, and the current at the interconnection point may be measured by a current measuring device located outside the housing. This allows a device including a current measuring device (e.g., an automatic switch) to be configured as an option for the power converter, increasing the degree of configuration flexibility in the power supply system.

[0025] (5) In any one of (1) to (3) above, the power converter may further include a current measuring device for measuring the current at the interconnection point, and a housing for housing the inverter, control unit, and current measuring device. This allows the current measuring device (e.g., CT) to be calibrated during the shipping inspection of the power converter, enabling high-precision power detection. Furthermore, it eliminates the need to attach the current measuring device to the outside of the power converter at the installation site, thus preventing construction errors associated with the installation of the current measuring device.

[0026] (6) In any one of (1) to (5) above, the control unit may determine the power consumption state of the load by multiplying the value obtained by subtracting the current at the interconnection point from the inverter current by the voltage of the grid. This makes it possible to accurately calculate the power consumption state (i.e., power consumption) of the load without directly measuring the current supplied to the load from the power converter.

[0027] (7) The power supply system relating to the second aspect of this disclosure includes a photovoltaic power generation device that outputs DC power, a rechargeable energy storage device, and one of the power converters described in (1) to (6) above, the power converter converts the DC power output from the photovoltaic power generation device and the energy storage device into AC power and outputs it to the load and the grid. As a result, the power supply system can control the charging and discharging of the energy storage device according to the power supply and demand conditions of the grid by changing the software alone, without changing the location of the current measuring device. Therefore, during times when the power of the grid is tight, it becomes possible to switch the operating mode to one that has an upward effect to increase the reverse power flow and contribute to resolving power shortages.

[0028] (8) A control method relating to a third aspect of the present disclosure is a control method for a power converter including an inverter and a control unit, comprising: a power supply step in which the control unit converts DC power output from a photovoltaic power generator and a battery storage device into AC power using an inverter and outputs it to a load and the grid; and a step in which the control unit obtains a measured current from a current measuring device that measures the current at the interconnection point connecting the inverter and the grid, wherein the power supply step comprises: a step in which the control unit identifies the power consumption state of the load based on the current of the inverter and the current measured by the current measuring device; and a step in which the control unit controls the charging and discharging of the battery storage device based on the identified power consumption state of the load, the power generation state of the photovoltaic power generator, and the power supply and demand state of the grid. As a result, the power converter can control the charging and discharging of the battery storage device according to the power supply and demand state of the grid simply by changing the software, without changing the location of the current measuring device. Therefore, it becomes possible to switch the operating mode to one that has an upward effect during times when the power of the grid is tight, thereby increasing the reverse power flow and contributing to the resolution of power shortages.

[0029] [Details of the embodiments of this disclosure] In the following embodiments, identical parts are assigned the same reference numeral. Their names and functions are also identical. Therefore, detailed descriptions of them will not be repeated.

[0030] (System Configuration) Referring to Figure 4, the power converter 100 according to the embodiment of this disclosure includes a PV converter 104 connected to a PV panel 102 and a battery converter 108 connected to a battery 106. The power converter 100 further includes an inverter 110 connected to the PV converter 104 and the battery converter 108, a control unit 112 that controls the PV converter 104, the battery converter 108 and the inverter 110, and a relay 114. The power converter 100, the PV panel 102 and the battery 106 constitute a hybrid power supply system. In Figure 4, two positive and negative wires are represented by a single solid line. For example, the two terminals of the PV converter 104 are connected one-to-one to the input terminals of the inverter 110, and the two terminals of the battery converter 108 are connected one-to-one to the input terminals of the inverter 110. That is, the PV converter 104 and the battery converter 108 are connected in parallel.

[0031] The PV panel 102 consists of multiple solar cells connected in series, arranged on a plane and sealed using tempered glass or the like. The PV panel 102 functions as a DC power source. The PV converter 104, under the control of the control unit 112, boosts the DC voltage output from the PV panel 102 and outputs it to the inverter 110. The battery 106 is a rechargeable battery such as a lithium-ion secondary battery. The battery 106 functions as a DC power source. The battery converter 108, under the control of the control unit 112, boosts the DC voltage output from the battery 106 and outputs it to the inverter 110. The battery converter 108 is also capable of bidirectional power conversion, converting surplus power output from the PV converter 104 and charging the battery 106. The inverter 110, under the control of the control unit 112, converts the DC voltages from the PV converter 104 and the battery converter 108 into AC voltages and outputs them to the relay 114. When relay 114 is turned on (i.e., short-circuited) under the control of control unit 112, the power converter 100 supplies power to load 122. In addition, inverter 110 is capable of bidirectional power conversion, and control unit 112 monitors the current value using current sensor 116 to enable grid connection with power grid 120. Current sensor 116 detects the current at the connection node (specifically connection point 118) between power converter 100 (specifically relay 114) and power grid 120, and outputs the detected current value to control unit 112.

[0032] The PV converter 104 and the battery converter 108 are DC / DC converters, and are implemented, for example, by a bridge circuit using semiconductor switching elements (FETs (Field Effect Transistors) etc.). The inverter 110 is a DC / AC converter, and is implemented, for example, by a bridge circuit using semiconductor switching elements.

[0033] The control unit 112 controls the power conversion functions of each component, namely the input and output voltages and currents, by outputting control signals (e.g., gate signals) for the switching elements (e.g., FETs) that constitute each of the PV converter 104, the battery converter 108, and the inverter 110. The control unit 112 includes, for example, a CPU (Central Processing Unit) and memory. The functions of the control unit 112 are realized by the CPU executing a program stored in memory. The power converter 100 has internal sensors (not shown) for measuring the voltage and current of each part. The control unit 112 controls the PV converter 104, the battery converter 108, and the inverter 110 based on the current value detected by the current sensor 116, as well as the current and voltage detected by sensors inside the power converter 100.

[0034] The control unit 112 receives measured values ​​from the PV converter 104, including the output voltage (i.e., DC voltage) of the PV converter 104 and the current flowing through the DC reactor inside the PV converter 104. The control unit 112 uses the measured values ​​received from the PV converter 104 to calculate the power generated by the PV panel 102, as described later. The control unit 112 receives measured values ​​from the battery converter 108, including the output voltage (i.e., DC voltage) of the battery converter 108 and the current flowing through the DC reactor inside the battery converter 108. The control unit 112 uses the measured values ​​received from the battery converter 108 to calculate the discharge power of the battery 106, as described later. The control unit 112 receives measured values ​​from the inverter 110, including the output voltage (i.e., AC voltage) of the inverter 110 and the current flowing through the AC reactor inside the inverter 110. The control unit 112 uses the current value received from the inverter 110 to calculate the power consumption of the load 122, as described later.

[0035] The power converter 100 may also include a voltage sensor that detects the voltage at the interconnection point 118 and outputs the detected voltage to the control unit 112. The control unit 112 may calculate the power to the grid 120 based on the voltage value detected by the voltage sensor and the current value detected by the current sensor 116.

[0036] (operation) The operation of the power converter 100 will be explained with reference to Figure 5. The process shown in Figure 5 is realized when the power converter 100 receives instructions from an external device (for example, operation of a remote control), and the CPU inside the control unit 112 reads and executes a program stored in the memory inside the control unit 112. Here, it is assumed that the operating modes of the hybrid system shown in Figure 4 are pre-set and stored in the internal memory of the control unit 112. There are two operating modes: a self-consumption priority mode in which no electricity is sold, and a sales priority mode in which electricity is sold. As mentioned above, the sales priority mode has two operating modes: one without a push-up effect and one with a push-up effect. In the self-consumption priority mode, the power generated by the PV panel 102 is supplied as the power consumed by the load 122, and if the power generated by the PV panel 102 is less than the power consumed by the load 122, the difference is supplied by discharging the battery 106. If the power generated by the PV panel 102 is greater than the power consumed by the load 122, the surplus power is used to charge the battery 106.

[0037] The operating mode can be set, for example, by an external remote control (not shown) of the power converter 100. The control unit 112 executes a program in parallel with the program shown in Figure 5 to wait for the setting of the operating mode from an external source. When the control unit 112 receives data representing the operating mode, it stores the received data in the internal memory of the control unit 112.

[0038] In step 300, the control unit 112 refers to the internal memory to determine whether the set operating mode is the power sales priority mode. If it is determined to be the power sales priority mode, the control proceeds to step 302. Otherwise, the control proceeds to step 326.

[0039] In step 302, the control unit 112 refers to the internal memory to determine whether the set operating mode is an operating mode with an upward effect. If it is an operating mode with an upward effect, the control proceeds to step 304. Otherwise, the control proceeds to step 316.

[0040] In step 304, the control unit 112 starts operating in a power sales priority mode with an upward boost effect. Specifically, the control unit 112 controls the PV converter 104, the battery converter 108, and the inverter 110 using the default parameters of the power sales priority mode with an upward boost effect. After that, the control proceeds to step 306.

[0041] In step 306, the control unit 112 calculates the power consumption of the load 122 and the discharge power of the PV converter 104. Then, the control proceeds to step 308. Specifically, the control unit 112 calculates the instantaneous power consumption for each of the two phases of the single-phase three-wire system using equation 4 below, adds these instantaneous values ​​together, and calculates the power consumption by averaging them over one AC cycle. The control unit 112 also calculates the instantaneous discharge power using equation 5 below, averages these instantaneous values ​​over the same period as the above AC cycle, and calculates the discharge power of the battery 106. Instantaneous power consumption = {system voltage × (inverter current - system current)} ... (Equation 4) Instantaneous discharge power = Battery voltage × Battery current ... (Equation 5) Here, the grid voltage is the voltage value of grid 120, the inverter current is the current value of the AC reactor inside the inverter 110 as described above, and the grid current is the current value detected by the current sensor 116. The battery voltage is the output voltage value of the battery converter 108, and the battery current is the current value of the DC reactor inside the battery converter 108 as described above.

[0042] In step 308, the control unit 112 controls the output power of the PV panel 102 and the battery 106 (i.e., the PV converter 104 and the battery converter 108). The control then proceeds to step 310. Specifically, the control unit 112 uses the power consumption of the load 122 and the discharge power of the battery 106 calculated in step 306 to perform feedback control, adjusting the output power of the battery converter 108 so that the discharge power of the battery 106 matches the power consumption of the load 122. The control unit 112 also controls the inverter 110 so that the power generated by the PV panel 102 is supplied to the grid 120 and the output power of the battery converter 108 is supplied to the load 122.

[0043] In step 310, the control unit 112 determines whether or not an instruction to terminate has been given. If it is determined that an instruction to terminate has been given, the control proceeds to step 314. Otherwise, the control proceeds to step 312. The instruction to terminate may be given, for example, by operating a remote control.

[0044] In step 312, the control unit 112 determines whether or not it has received an instruction to change the operating mode. Specifically, the control unit 112 refers to the internal memory and determines whether or not data representing an operating mode different from the currently running operating mode is stored. If it is determined that data representing a different operating mode is stored (i.e., an instruction to change the operating mode has been received), control returns to step 300, and operation in the new operating mode is performed. Otherwise, control returns to step 308, and the process from step 308 to step 310 described above is repeated. The operating mode is changed, for example, by operating the remote control, and as described above, data representing the new operating mode is stored in the internal memory of the control unit 112.

[0045] In step 314, the control unit 112 shuts down the hybrid power supply system and terminates the program. At this time, the data representing the operating mode stored in the internal memory of the control unit 112 is retained and not erased.

[0046] If the result of step 302 is NO, in step 316, the control unit 112 starts operating in a power sales priority mode without the push-up effect. Specifically, the control unit 112 controls each of the PV converter 104, the battery converter 108, and the inverter 110 using the default parameters of the power sales priority mode without the push-up effect. After that, the control proceeds to step 318.

[0047] In step 318, the control unit 112 calculates the reverse power flow. Then, the control proceeds to step 320. Specifically, the control unit 112 calculates the reverse power flow by adding the instantaneous values ​​of the reverse power flow calculated by equation 6 below for each of the two phases of the single-phase three-wire system and averaging them over one AC cycle. Instantaneous value of reverse power flow = Grid power × Grid current ... (Equation 6) Here, the system voltage is the voltage value of system 120, and the system current is the value detected by the current sensor 116 (current value).

[0048] In step 320, the control unit 112 controls the output power of the PV panel 102 and the battery 106 (i.e., the PV converter 104 and the battery converter 108). The control then proceeds to step 322. Specifically, the control unit 112 controls the battery converter 108 so that the reverse power flow calculated in step 318 becomes 0, that is, so that power equivalent to the difference between the power consumption of the load 122 and the output power of the PV converter 104 is discharged from the battery 106. When the output power of the battery converter 108 is 0, i.e., the battery 106 is not discharging, if the output power of the PV converter 104 is greater than the power consumption of the load 122, the control unit 112 controls the inverter 110 so that the surplus power is supplied to the grid 120.

[0049] The output power of the battery converter 108 (i.e., the discharge power of the battery 106) is calculated by averaging the instantaneous values ​​calculated by Equation 5 over the same period as one AC cycle, as described above. The power generated by the PV panel 102 is calculated by averaging the instantaneous values ​​of the power generated by Equation 7 below over the same period as one AC cycle. Instantaneous power generation = generated voltage × generated current ... (Equation 7) Here, the generated voltage is the output voltage value of the PV converter 104, and the generated current is the current value of the DC reactor inside the PV converter 104 as described above.

[0050] In step 322, the control unit 112 determines whether or not termination has been instructed, similar to step 310. If it is determined that termination has been instructed, control proceeds to step 314. Otherwise, control proceeds to step 324.

[0051] In step 324, the control unit 112 determines whether or not it has received an instruction to change the operating mode, similar to step 312. If it determines that it has received an instruction to change the operating mode, control returns to step 300, and operation in the new operating mode is performed. Otherwise, control returns to step 318, and the processes from step 318 to step 322 described above are repeated.

[0052] If the result of step 300 is NO, in step 326, the control unit 112 starts operating in self-consumption priority mode. Specifically, the control unit 112 controls each of the PV converter 104, the battery converter 108, and the inverter 110 using the default parameters of self-consumption priority mode. After that, the control proceeds to step 328.

[0053] In step 328, the control unit 112 calculates the reverse power flow, similar to step 318. The control then proceeds to step 330.

[0054] In step 330, the control unit 112 controls the output power of the PV panel 102 and the battery 106 (i.e., the PV converter 104 and the battery converter 108). The control then proceeds to step 332. Specifically, the control unit 112 controls the battery converter 108 so that the reverse power flow calculated in step 328 becomes 0, that is, so that power equivalent to the difference between the power consumption of the load 122 and the output power of the PV converter 104 is discharged from the battery 106. When the output power of the battery converter 108 is 0, i.e., the battery 106 is not discharging, if the output power of the PV converter 104 is greater than the power consumption of the load 122, the control unit 112 controls the battery converter 108 so that the surplus power is used as charging power for the battery 106. The output power of the battery converter 108 (i.e., the discharge power of the battery 106) is calculated by averaging the instantaneous values ​​calculated by Equation 5 over the same period as one AC cycle, as described above. The output power of the PV converter 104 (i.e., the generated power) is calculated by averaging the instantaneous values ​​calculated by Equation 7 over the same period as one AC cycle, as described above.

[0055] In step 332, the control unit 112 determines whether or not termination has been instructed, similar to step 310. If it is determined that termination has been instructed, control proceeds to step 314. Otherwise, control proceeds to step 334.

[0056] In step 334, the control unit 112 determines whether or not it has received an instruction to change the operating mode, similar to step 312. If it is determined that it has received an instruction to change the operating mode, control returns to step 300, and operation in the new operating mode is performed. Otherwise, control returns to step 328, and the process from step 328 to step 332 described above is repeated.

[0057] As a result, the control unit 112 can operate the power converter 100 in the set operating mode. Even when the operating mode is changed due to a contract change, this can be handled without changing the installation position of the current sensor 116. While consumers can switch between the self-consumption priority mode and the power sales priority mode without the boosting effect using a remote control, changing to any other operating mode requires a change in the contract with the power company. That is, when changing the operating mode to the power sales priority mode with the boosting effect, and when changing the operating mode from the power sales priority mode with the boosting effect, a contract change is necessary. For example, conventionally, when the contract changes from no boosting effect to a mode with a boosting effect, the installation position of the current sensor 116 in the configuration of Figure 4 needs to be changed to a position where the current supplied to the load 122 can be directly measured, as shown in Figure 3. In contrast, the program shown in Figure 5 can handle changes in the operating mode due to a contract change without changing the installation position of the current sensor 116.

[0058] As described above, the control unit 112 calculates the power consumption of the load 122 by multiplying the value obtained by subtracting the current value detected by the current sensor 116 at the interconnection point 118 from the current value of the inverter 110 by the voltage value of the grid 120. This makes it possible to accurately calculate the power consumption of the load 122 without directly measuring the current supplied to the load 122 from the power converter.

[0059] In the above, we have described a case in which the process of changing the operating mode in response to an instruction is implemented by a single program as shown in Figure 5, but this is not limited to this. For example, the control unit 112 may store a program for each operating mode in its internal memory. When the control unit 112 is instructed to change the operating mode, it simply needs to read the program for the instructed operating mode from its internal memory and execute it.

[0060] As mentioned above, currently, reverse power flow of discharged power from a battery is prohibited. However, if reverse power flow is permitted in the future, the power converter 100 can operate in a new operating mode that allows reverse power flow of discharged power from the battery 106 by changing the software without changing the position of the current sensor 116.

[0061] The above describes a case where a customer instructs a change in the operating mode by operating an external device such as a remote control, but is not limited to this. If the power converter or its operating unit (e.g., remote control) has a communication function with a network such as the Internet, the control unit of the power converter can change the operating mode of the power converter in response to instructions from a computer connected to the network. This allows the customer's power supply system to receive remote control at the request of the transmission and distribution company or the electricity retailer, enabling power supply to the grid and control of power supply and demand in the local grid. For example, during times when grid power is tight, the power converter can receive instructions from the power company's server computer to change the operating mode it is currently running to an operating mode with an upward effect, thereby increasing reverse power flow and contributing to resolving power shortages.

[0062] Furthermore, instructions from the server computer to the power converter are not limited to instructions for the operating mode, but may also directly specify the discharge power from the battery. Also, since the current sensor is located at the connection point with the grid, the control command from the server computer may be a control command for the connection point, such as "discharge 1000W from the power converter at the connection point."

[0063] (modified version) The above describes a case where the current sensor 116 is located outside the power converter 100, but the device is not limited to this. The modified power converter is configured to include a current sensor.

[0064] Referring to Figure 6, the power converter 150 according to the first modified example includes a housing 152. The housing 152 houses a PV converter 104, a battery converter 108, an inverter 110, a control unit 112, a relay 114, and a current sensor 116. The power converter 150, together with the external PV panel 102 and battery 106, constitutes a hybrid power supply system. The PV converter 104, battery 106, inverter 110, control unit 112, relay 114, and current sensor 116 are the same as in Figure 4, and their interconnections, as well as their connections to the external PV panel 102, battery 106, grid 120, and load 122, are also the same. Therefore, redundant explanations will not be repeated. The power converter 150 can change its operating mode, similar to the power converter 100 described above.

[0065] As shown in Figure 6, by housing the current sensor 116 in the housing 152 to constitute the power converter 150, the current sensor 116 (e.g., CT) can be calibrated during the shipping inspection of the power converter 150, enabling high-precision power detection. Furthermore, at the installation site of the power converter 150, it is unnecessary to attach the current sensor to the outside of the power converter 150, thus preventing installation errors associated with the installation of the current sensor.

[0066] Note that the current sensor may be housed in a separate housing from the housing that houses the power converter. For example, referring to Figure 7, the current sensor 116 may be housed in a separate housing 176 from the housing 172 that constitutes the power converter 170. Housing 172 houses the PV converter 104, the battery converter 108, the inverter 110, the control unit 112, and the relay 114. Housing 176 houses the current sensor 116 and the MC (electroMagnetic Contactor) 178, and constitutes the automatic switching device 174. The MC 178 is an electromagnetic contactor whose circuit is opened and closed by an electromagnet. When the MC 178 is closed (i.e., short-circuited) under the control of the control unit 112, the power converter supplies power to the grid 120. In this way, by housing the current sensor 116 in housing 176, human error that may occur when the current sensor 116 is installed as a standalone unit can be avoided. Furthermore, housing 176 including the current sensor 116 can be configured as an option for the power converter 170. Therefore, the degree of flexibility in configuration increases in power supply systems.

[0067] The above description illustrates a hybrid power supply system that includes one PV panel and one battery, but it is not limited to this. A hybrid power supply system may include multiple PV panels or multiple batteries.

[0068] The above describes a hybrid power supply system that includes PV panels and a battery, but it is not limited to this. A hybrid power supply system may also include power generation equipment other than PV panels and a battery.

[0069] The present disclosure has been described above by describing embodiments, but the embodiments described above are illustrative and the present disclosure is not limited to the embodiments described above. The scope of the present disclosure is as indicated by the claims, with reference to the detailed description of the invention, and includes all modifications within the meaning and scope equivalent to the wording contained herein. [Explanation of Symbols]

[0070] 100, 150, 170, 900 Power Converters 102, 902 PV panels Converter for 104 and 904 PV 106, 906 storage batteries 108, 908 Battery Converter 110, 910 inverter 112 Control Unit 114, 914 relay 116, 916 Current Sensor 118 interconnection points 120, 920 lines 122,922 load 152, 172, 176 cabinets 174 Automatic switching device 178 MC

Claims

1. A power converter that operates in a predetermined operating mode among multiple operating modes, An inverter that converts DC power output from a solar power generation system and energy storage system into AC power and outputs it to the load and grid, A control unit that controls the inverter, The inverter and a current measuring device for measuring the current at the interconnection point connecting the system are included. The aforementioned multiple operating modes include an operating mode without a push-up effect and an operating mode with a push-up effect. The control unit further, When the predetermined operating mode is the operating mode without the push-up effect, the power supply and demand state of the grid, which indicates the power supplied from the grid or the power flowing back into the grid, is identified based on the current at the interconnection point measured by the current measuring device, and the charging and discharging of the energy storage device is controlled based on the identified power supply and demand state of the grid and the power generation state of the solar power generation device. A power converter that, when the predetermined operating mode is the operating mode with the upward pushing effect, identifies the power consumption state of the load based on the current of the inverter and the current at the interconnection point measured by the current measuring device, and controls the charging and discharging of the energy storage device based on the identified power consumption state of the load and the power generation state of the solar power generation device.

2. The aforementioned predetermined operating mode is determined by contract with the power company. The power conversion device according to claim 1, wherein the control unit receives an instruction from an external source and controls the charging and discharging of the energy storage device according to the operating mode specified by the instruction.

3. In the operating mode with the push-up effect, the control unit discharges the energy storage device so that the discharge power of the energy storage device matches the power consumption of the load, as described in claim 1.

4. The enclosure further includes the inverter and the control unit, The current measuring device is located outside the housing, and the power conversion device is as described in any one of claims 1 to 3.

5. The power conversion device according to any one of claims 1 to 3, further comprising a housing for housing the inverter, the control unit, and the current measuring device.

6. The power conversion device according to any one of claims 1 to 3, wherein the control unit determines the power consumption state of the load by multiplying a value obtained by subtracting the current at the interconnection point from the current of the inverter by the voltage of the grid.

7. A solar power generation device that outputs DC power, A rechargeable and dischargeable energy storage device, Includes a power conversion device according to any one of claims 1 to 3, The power conversion device is a power supply system that converts the DC power output from the solar power generation device and the energy storage device into AC power and outputs it to the load and the grid.

8. A control method for a power converter that includes an inverter and a control unit, and a current measuring device for measuring the current at the interconnection point connecting the inverter and the grid, and which operates in a predetermined operating mode among a plurality of operating modes, The aforementioned multiple operating modes include an operating mode without a push-up effect and an operating mode with a push-up effect. The control method described above is The control unit performs a power supply step in which it converts the DC power output from the solar power generation device and the energy storage device into AC power using the inverter and outputs it to the load and the grid, The control unit includes the step of acquiring the measured current from the current measuring device, The aforementioned power supply step is: When the predetermined operating mode is the operating mode without the push-up effect, the control unit identifies the power supply and demand state of the grid, which indicates the power supplied from the grid or the power flowing back into the grid, based on the current measured by the current measuring device, and controls the charging and discharging of the energy storage device based on the identified power supply and demand state of the grid and the power generation state of the solar power generation device. A control method comprising the steps of: identifying the power consumption state of the load based on the current of the inverter and the current at the interconnection point measured by the current measuring device when the predetermined operating mode is the operating mode with the pushing effect; and controlling the charging and discharging of the energy storage device based on the identified power consumption state of the load and the power generation state of the solar power generation device.

Images