Power system
The power system efficiently utilizes renewable energy by using dual processing units to manage power control, achieving both system and operational objectives, including maximizing solar power generation and maintaining connection point power, even in abnormal conditions.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- DAIHEN CORP
- Filing Date
- 2022-09-20
- Publication Date
- 2026-05-13
AI Technical Summary
Existing power systems struggle to effectively utilize electricity generated from renewable energy sources while controlling power as a whole system, particularly in systems connected to a power grid.
A power system with a first and second processing unit that calculates and modifies control command values to achieve both system and operational objectives, allowing one power unit to control power based on unmodified values and the other based on modified values, with the second unit adjusting limits and handling abnormalities.
The system effectively utilizes renewable energy by achieving operational objectives like maximizing power generation from solar units while maintaining system objectives like connection point power control, even in abnormal conditions.
Smart Images
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Abstract
Description
Technical Field
[0001] The present disclosure relates to a power system.
Background Art
[0002] In recent years, power systems that are connected to a power grid and control power reception from the power grid have been increasingly popular. For example, Patent Documents 1 and 2 disclose an example of a power system including a plurality of power devices and a processing device (central management device). The processing device calculates an index (induction command value) for controlling a predetermined adjustment target power to a target power. Each power device dispersedly controls output power using the induction command value calculated by the processing device. At this time, each power device calculates a target value of output power based on an optimization problem using the induction command value. Then, the output power is controlled so that the output power becomes the target value. In this way, energy management of the power system is performed.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Patent Document 2
Summary of the Invention
Problems to be Solved by the Invention
[0004] The power systems described in Patent Documents 1 and 2 control power so that the power to be adjusted as a whole becomes the target power, by having each power device perform distributed output control. Furthermore, the power systems described in Patent Documents 1 and 2 include a solar power generation device. Since power generation using renewable energy such as solar power does not consume finite resources such as oil, coal, or natural gas, it is desirable to utilize it effectively without restricting it as much as possible. In other words, it is necessary to effectively utilize the power that can be generated by renewable energy while performing power control as a whole system.
[0005] This disclosure was conceived in view of the above circumstances, and its purpose is to provide a power system that can effectively utilize electricity generated from renewable energy sources while controlling the power of the entire system. [Means for solving the problem]
[0006] The power system provided by this disclosure is a power system for controlling connection point power at a connection point with a power grid, comprising: a first battery; a first power device to which the first battery is connected and which charges and discharges the first battery; at least one power generation unit, each generating electricity from renewable energy; a second battery; a second power device to which the at least one power generation unit and the second battery are connected via a common DC line and which charges and discharges the second battery; a first processing unit for calculating a control command value to achieve a system objective of making the connection point power a target power; and an operational objective different from the system objective. The system includes a second processing unit that modifies the control command value calculated by the first processing unit and generates a transmission control command value to be transmitted to the first power unit and the second power unit, respectively, using the control command value before modification and the control command value after modification. One of the first power unit and the second power unit receives the control command value before modification as the transmission control command value and controls its output power based on the control command value before modification, and the other of the first power unit and the second power unit receives the control command value after modification as the transmission control command value and controls its output power based on the control command value after modification.
[0007] In a preferred embodiment of the power system, the control command value includes an induction command value for the second power device, and if the induction command value calculated by the first processing unit exceeds an upper limit set for that induction command value, the second processing unit changes the induction command value calculated by the first processing unit to a value limited to that upper limit as the modified induction command value, and the upper limit is changed by the second processing unit according to the total value of the power generated by the at least one power generation unit.
[0008] In a preferred embodiment of the power system, when a first abnormality occurs in which the control command value cannot be received normally from the first processing unit, the second processing unit either continues to transmit the transmission control command value that was transmitted immediately before the first abnormality occurred, or transmits the set value for the first abnormality as the transmission control command value.
[0009] In a preferred embodiment of the power system, the at least one power generation unit includes a first power generation unit and one or more second power generation units, and when a second abnormality occurs in which the second processing unit cannot obtain information for generating the transmission control command value, the first power generation unit continues to generate power and the one or more second power generation units stop generating power.
[0010] In a preferred embodiment of the power system, the at least one power generation unit includes a plurality of power generation units, and when a third abnormality occurs in which the second power device is unable to perform output control, all power generation by the plurality of power generation units is stopped.
[0011] In a preferred embodiment of the power system, each of the at least one power generation unit is a solar power generation unit that generates electricity using solar energy, and the first battery is mounted on an electric vehicle. [Effects of the Invention]
[0012] In the power system of this disclosure, a first processing unit calculates a control command value to achieve a system objective, and a second processing unit modifies the control command value calculated by the first processing unit to achieve an operational objective. Then, either the first or second power unit controls the output power based on the control command value before it is modified by the second processing unit (the control command value before modification). This enables the power system to achieve the system objective. Furthermore, the other of the first or second power unit controls the output power based on the control command value after it has been modified by the second processing unit (the control command value after modification). This enables the power system to achieve the operational objective. In other words, according to the power system of this disclosure, it is possible to control power to achieve operational objectives different from the system objective while achieving the system objective set for the entire system. Therefore, the power system can control power as a whole system as its system objective, and effectively utilize electricity generated from renewable energy as its operational objective. [Brief explanation of the drawing]
[0013] [Figure 1] This is an example of the overall configuration showing a power system according to the first embodiment of this disclosure. [Figure 2] Figure 1 is a schematic diagram showing an example of the operation of a processing unit in a power system. [Figure 3] This figure shows the state in which the first abnormality occurs in the power system shown in Figure 1. [Figure 4] This figure shows the state when a second abnormality occurs in the power system shown in Figure 1. [Figure 5] This figure shows the state when a third abnormality occurs in the power system shown in Figure 1. [Figure 6] This is an example of the overall configuration showing a power system according to the second embodiment of this disclosure. [Modes for carrying out the invention]
[0014] Preferred embodiments of the power system of this disclosure are described below with reference to the drawings. Hereafter, identical or similar components are denoted by the same reference numerals, and redundant descriptions are omitted.
[0015] Figure 1 shows the overall configuration of the power system S1 according to the first embodiment. The power system S1 includes a processing unit A1, a plurality of first power devices B1, a second power device B2, an energy storage device C1, a plurality of first batteries BT1, a detection device D1, a plurality of circuit breakers CB1 to CB3, a plurality of electromagnetic contactors MC1 to MC3, a plurality of photovoltaic power generation units PVU1 to PVU3, an overcurrent detection board 54, an AC line 91, and a DC line 92. The energy storage device C1 also includes a second battery BT2. In Figure 1, thick lines indicate connections via a power network, and dashed lines indicate connections via a communication network.
[0016] The power system S1 is connected to the connection point T and interconnected with the power grid K. The power system S1 can receive power from the power grid K. In this embodiment, the power system S1 cannot transmit power to the power grid K (i.e., cannot have reverse power flow), but it may be able to transmit power to the power grid K (i.e., can have reverse power flow). In the present disclosure, when power is output from the power grid K to the power system S1, it is assumed that the connection point power becomes a negative value. The connection point power refers to the power at the connection point T between the power system S1 and the power grid K. The power system S1 supplies the power supplied from the power grid K and the power output from the plurality of first power devices B1 and second power devices B2 to the load L connected to the connection point T. Also, when the power system S1 is disconnected from the power grid K, it can operate independently. During independent operation, the power output from the plurality of first power devices B1 and second power devices B2 can be supplied to the load L.
[0017] As can be understood from the configuration described in detail later, the power system S1 performs power control so as to achieve an operation target different from the system target while achieving the system target. The system target of this embodiment is to make the connection point power the target power. The target power is the target value of the connection point power. The operation target of this embodiment is, for example, to effectively utilize the generated power by each photovoltaic power generation unit PVU1 to PVU3. Note that the system target and the operation target are not limited to the above examples.
[0018] In the power control of the power system S1, the processing device A1 (the first processing unit 11 described later) calculates a control command value for achieving the system target (i.e., for making the connection point power the target power). Also, the processing device A1 (the second processing unit 12 described later) changes the calculated control command value in order to achieve the operation target. Then, either one of the plurality of first power devices B1 and the second power devices B2 performs output control based on the control command value before the change to achieve the system target. Also, the others of the plurality of first power devices B1 and the second power devices B2 perform output control based on the control command value after the change to achieve the operation target.
[0019] The detection device D1 is connected to the connection point T between the power system S1 and the power grid K, and detects the connection point power. The detection device D1 has a communication function and can communicate with the processing device A1. The detection device D1 transmits the detected value of the connection point power to the processing device A1. The detection device D1 includes, for example, a detection sensor, an AD converter, and a communication unit. The detection device D1 detects the connection point power by a detection sensor such as a power transducer, and converts the detected value (analog value) of the connection point power into a digital value by the AD converter. Then, the communication unit transmits the detected value (digital value) of the connection point power to the processing device A1. Various protection devices (such as overcurrent relays, overvoltage relays, underpower relays, and reverse power relays, etc.) for connecting the power system S1 to the power grid K are further installed in the detection device D1 as required.
[0020] In order to achieve the operation target while achieving the system target, the processing device A1 transmits the above control command values (the control command value before change and the control command value after change) to each of the plurality of first power devices B1 and second power devices B2. The processing device A1 includes a first processing unit 11 and a second processing unit 12.
[0021] The first processing unit 11 calculates a control command value for achieving the above system target (that is, a control command value for making the connection point power the target power). The first processing unit 11 has a communication function and can communicate with the detection device D1, the second processing unit 12, the plurality of first power devices B1, and the second power device B2 respectively. The first processing unit 11 uses the connection point power and the target power in calculating the control command value. The connection point power may use the detected value detected by the detection device D1, or may be an estimated value calculated from the values of each output power obtained by communication from each of the plurality of first power devices B1 and second power devices B2. The target power may be a value set by a management computer not shown, or may be a value preset according to a predetermined control mode. The predetermined control mode is, for example, the same as that described in the above Patent Document 1.
[0022] In this embodiment, the first processing unit 11 calculates a first induction command value for controlling the power of multiple first power devices B1 and a second induction command value for controlling the power of the second power device B2 as control command values. The first induction command value and the second induction command value may be the same or different. The first induction command value is common to all of the multiple first power devices B1. The first processing unit 11 calculates the first induction command value and the second induction command value by solving a predetermined state equation (simultaneous differential equations). This predetermined state equation is the same as that described in Patent Document 2. The first processing unit 11 transmits the calculated control command values (first induction command value and second induction command value) to the second processing unit 12. In a different configuration, the power system S1 may calculate a common induction command value for all of the multiple first power devices B1 and the second power devices B2. The first processing unit 11 periodically calculates and transmits the control command values at predetermined processing cycles.
[0023] For example, the first processing unit 11 calculates the first induction command value and the second induction command value as follows. Assume a case where the connection point power is set to the target power P0 [kW] as the system target. In this assumption, in order to set the output power of a group including a plurality of first power devices B1 to the target power P1 [kW] (P1 < P0), the first processing unit 11 uses the output power of the group including the plurality of first power devices B1 and the target power P1 to solve a predetermined state equation, thereby calculating the first induction command value. Also, in order to set the output power of a group including the second power device B2 to the target power P2 [kW] (P2 = P0 - P1), the first processing unit 11 uses the output power of the group including the second power device B2 and the target power P2 to solve a predetermined state equation, thereby calculating the second induction command value. In this case, if the two target powers P1 and P2 are the same (P1 = P2 = P0 / 2), the first induction command value and the second induction command value are the same, and if the two target powers P1 and P2 are different (P1 ≠ P2), the first induction command value and the second induction command value are different. However, in this calculation method, when the second processing unit 12 changes the control command value to achieve the above operation target, there is a possibility that the target powers P1 and P2 in each group cannot be achieved. In this case, it is advisable to include other power devices in each group. This other power device performs output control based on the first induction command value before the change or the second induction command value before the change even if the first induction command value or the second induction command value is changed by the second processing unit 12. Alternatively, in the above assumption, in order to set the connection point power to the target power P0, the first processing unit 11 uses the connection point power detected by the detection device D1 and the target power P0 to solve a predetermined state equation, thereby calculating a common induction command value for the plurality of first power devices B1 and the second power device B2. Then, this common induction command value is set to each of the first induction command value and the second induction command value.
[0024] The second processing unit 12 modifies the control command value calculated by the first processing unit 11 in order to achieve the above operational objective. The second processing unit 12 has a communication function and can communicate with the first processing unit 11, multiple first power devices B1, second power devices B2, multiple photovoltaic power generation units PVU1 to PVU3, multiple electromagnetic contactors MC1 to MC3, multiple circuit breakers CB1 to CB3, and the overcurrent detection board 54.
[0025] The second processing unit 12 receives control command values from the first processing unit 11. The control command values (first induction command value and second induction command value) received by the second processing unit 12 from the first processing unit 11 are referred to as "received control command values (received first induction command value and received second induction command value)". The second processing unit 12 modifies the received received control command values (received first induction command value and received second induction command value). However, if the operational objective is achieved by the control command values calculated by the first processing unit 11, the second processing unit 12 does not need to modify the received control command values. For the sake of explanation, the received control command values received by the second processing unit 12 without modification are referred to as "pre-modification control command values", and the modified received control command values are referred to as "modified control command values". In modifying the control command values to modified values, the second processing unit 12 appropriately uses information from multiple first power devices B1, second power devices B2, and the overcurrent detection board 54, etc. The second processing unit 12 then generates a transmission control command value (transmission first guidance command value and transmission second guidance command value) using the pre-change control command value (pre-change first guidance command value and pre-change second guidance command value) and the post-change control command value (post-change first guidance command value and post-change second guidance command value). For example, the transmission control command value includes either the pre-change control command value or the post-change control command value. Whether the transmission control command value includes the pre-change control command value or the post-change control command value is changed as appropriate according to the operational objective. In contrast to this configuration, the transmission control command value may include both the pre-change control command value and the post-change control command value. The second processing unit 12 transmits the generated transmission control command value to each of the multiple first power devices B1 and second power devices B2. The process of changing the control command values (first guidance command value and second guidance command value) performed by the second processing unit 12 will be described later.
[0026] Each of the multiple first power devices B1 is connected to a first battery BT1 and controls the charging and discharging of the first battery BT1. The first battery BT1 is, for example, one installed in an electric vehicle. In this example, each of the multiple first power devices B1 is an EV charger / discharger that can connect to an electric vehicle and controls the charging and discharging of the first battery BT1 installed in the electric vehicle. Unlike this example, the first battery BT1 does not have to be installed in an electric vehicle. In the illustrated example, each first power device B1 is connected to one first battery BT1 (one electric vehicle), but unlike this example, each first power device B1 may be connected to multiple first batteries BT1 (multiple electric vehicles). Each of the multiple first power devices B1 includes a communication processing unit 21 and a charge / discharge control unit 22. The communication processing unit 21 and charge / discharge control unit 22 described below are common to each first power device B1 unless otherwise specified.
[0027] The communication processing unit 21 relays communication between the processing unit A1 (first processing unit 11 and second processing unit 12) and the charge / discharge control unit 22. The communication processing unit 21 transmits information on the charge rate of the first storage battery BT1 and the output power (charging power and discharging power) of the charge / discharge control unit 22 to the processing unit A1 (first processing unit 11). The communication processing unit 21 receives a first transmission guidance command value (first guidance command value before change or first guidance command value after change) from the processing unit A1 (second processing unit 12). Using the received first transmission guidance command value, the communication processing unit 21 calculates the output target value of the charge / discharge control unit 22 (hereinafter referred to as the "first output target value") according to a predetermined calculation formula and constraints. This calculation formula and constraints are the same as those described in, for example, Patent Document 2. In other words, the method by which the communication processing unit 21 calculates the first output target value of the charge / discharge control unit 22 is the same as the calculation method described in Patent Document 2. The first output target value is calculated using the first induction command value. If the first induction command value increases, the first output target value changes so that the charging power of the first battery BT1 decreases or the discharge power of the first battery BT1 increases. The communication processing unit 21 outputs the calculated first output target value to the charge / discharge control unit 22.
[0028] The charge / discharge control unit 22 receives a first output target value from the communication processing unit 21 and performs output control so that the output power of the first power device B1 becomes the first output target value. When the first output target value is a positive value, the first power device B1 discharges the first battery BT1 (electric vehicle). On the other hand, when the first output target value is a negative value, the first power device B1 charges the first battery BT1 (electric vehicle). The charge / discharge control unit 22 obtains the charge rate of the first battery BT1 (electric vehicle). The charge / discharge control unit 22 transmits the charge rate of the first battery BT1 and the output power of the first power device B1 to the first processing unit 11 via the communication processing unit 21. The charge / discharge control unit 22 transmits this information at predetermined intervals (first output power transmission cycles).
[0029] Multiple solar power generation units PVU1 to PVU3 each generate electricity using solar energy. Each of the multiple solar power generation units PVU1 to PVU3 includes a solar panel and a DC / DC converter. There may be multiple DC / DC converters in each of the multiple solar power generation units PVU1 to PVU3. In each of the multiple solar power generation units PVU1 to PVU3, the electricity generated by the solar panel (generated power) is converted to a predetermined voltage value by the DC / DC converter and output. In the following description, the sum of the generated power of the multiple solar power generation units PVU1 to PVU3 is referred to as the "total output of the power generation units". In the illustrated example, three solar power generation units PVU1 to PVU3 are provided, but it is sufficient to provide one or more solar power generation units. In the power system S1, instead of each of the multiple solar power generation units PVU1 to PVU3, a power generation unit that generates electricity using renewable energy other than solar energy may be provided. Examples of such power generation include hydroelectric power, wind power, geothermal power, and solar thermal power.
[0030] Furthermore, each of the solar power generation units PVU1 to PVU3 has a communication function and can communicate with the processing unit A1 (second processing unit 12). Each of the solar power generation units PVU1 to PVU3 transmits information on the generated power to the second processing unit 12. Each of the solar power generation units PVU1 to PVU3 transmits information on the generated power at predetermined intervals (power generation transmission cycles).
[0031] Multiple electromagnetic contactors MC1 to MC3 are connected to multiple solar power generation units PVU1 to PVU3, respectively. Each electromagnetic contactor MC1 to MC3 has a communication function and can communicate with processing unit A1 (second processing unit 12). Each of the multiple electromagnetic contactors MC1 to MC3 is normally closed and opens when it receives an open signal from processing unit A1 (second processing unit 12). For example, each electromagnetic contactor MC1 to MC3 is normally closed when power is supplied from processing unit A1 (second processing unit 12) to an auxiliary contact (not shown). On the other hand, each electromagnetic contactor MC1 to MC3 opens when the power supply from processing unit A1 (second processing unit 12) to the aforementioned auxiliary contact is stopped. In this case, the cessation of power supply is considered to be the reception of an open signal. If any of the electromagnetic contactors MC1 to MC3 are opened, the power generated by the solar power generation units PVU1 to PVU3 connected to the opened electromagnetic contactor MC1 to MC3 will not be output to the second power device B2 side beyond the electromagnetic contactor MC1 to MC3.
[0032] Multiple circuit breakers CB1 to CB3 are connected to multiple electromagnetic contactors MC1 to MC3, respectively. Each of the multiple circuit breakers CB1 to CB3 is normally conductive and trips when a predetermined amount of current exceeding its rated capacity flows through it. Each circuit breaker CB1 to CB3 has a communication function and can communicate with processing unit A1 (second processing unit 12). Each circuit breaker CB1 to CB3 transmits information indicating its own status (continuing or tripped) to processing unit A1 (second processing unit 12).
[0033] The energy storage device C1 comprises one or more second batteries BT2. In the example shown in Figure 1, the energy storage device C1 comprises one second battery BT2, but it may comprise multiple second batteries BT2. The second battery BT2 is a secondary battery such as a lithium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, or lead-acid battery. The second battery BT2 may also be a capacitor such as an electric double-layer capacitor instead of a secondary battery. When the total output of the power generation unit is greater than the output power of the second power device B2, the surplus power is input to the second battery BT2. This charges the second battery BT2. On the other hand, when the total output of the power generation unit is less than the output power of the second power device B2, the second battery BT2 outputs the deficit power. This discharges the second battery BT2.
[0034] The energy storage device C1 has a communication function and can communicate with the second power device B2. The energy storage device C1 transmits battery information of the second battery BT2 to the second power device B2. The battery information includes charging power, discharging power, and state of charge (SOC). Charging power is the power when the second battery BT2 is being charged. The charging power has an upper limit (allowable charging power) calculated according to the allowable range of the charging C rate. Discharging power is the power when the second battery BT2 is being discharged. The discharge power has an upper limit (allowable discharge power) calculated based on the upper limit of the discharge C rate. The charging C rate and discharge C rate are the relative ratios of the current during charging and discharging to the total capacity of the second battery BT2, with 1C being the value when the total capacity of the second battery BT2 is charged and discharged in one hour. The second battery BT2 has an upper limit for the C rate during charging (e.g., 2C) and an upper limit for the C rate during discharging (e.g., 2C). The charge rate is an indicator of the charge state of the second battery BT2, and is expressed as a percentage of the remaining charge relative to the capacity when fully charged. The energy storage device C1 transmits battery information of the second battery BT2 at predetermined intervals (battery information transmission cycle).
[0035] The overcurrent detection board 54 is positioned in the DC line 92 between the second power device B2 and the second battery BT2 (energy storage device C1), and is positioned on the BT2 side of the connection point between the second battery BT2 and each of the photovoltaic power generation units PVU1 to PVU3. The overcurrent detection board 54 detects overcurrents in the output current (charging current and discharge current) of the second battery BT2. The overcurrent detection board 54 has a communication function and can communicate with the processing unit A1 (second processing unit 12). When the overcurrent detection board 54 detects the overcurrent, it transmits information about the C-rate overcurrent contact corresponding to this detection to the second processing unit 12. As a result, the second processing unit 12 can detect the occurrence of an overcurrent to the second battery BT2.
[0036] The second power unit B2 is a power conditioner. The second power unit B2 converts the input DC power into AC power and outputs it. The second power unit B2 can also convert the input AC power into DC power and output it. The second power unit B2 is connected to the load L and the power system K by an AC line 91. The second battery BT2 (energy storage device C1) is connected to the second power unit B2 by a DC line 92, and multiple solar power generation units PVU1 to PVU3 are connected via multiple circuit breakers CB1 to CB3 and multiple electromagnetic contactors MC1 to MC3. For the sake of explanation, the side to which the AC line 91 is connected to the second power unit B2 is called the "system side," and the side to which the DC line 92 is connected to the second power unit B2 is called the "distributed power source side." The second power unit B2 includes a communication processing unit 31 and an output control unit 32.
[0037] The communication processing unit 31 relays communication between the processing unit A1 (first processing unit 11 and second processing unit 12) and the energy storage device C1, and the output control unit 32. The communication processing unit 31 receives a second guidance command value from the second processing unit 12. Using the received second guidance command value, the communication processing unit 31 calculates the output target value of the output control unit 32 (hereinafter referred to as the "second output target value") according to a predetermined calculation formula and constraints. This calculation formula and constraints are the same as those described in, for example, Patent Document 2. In other words, the method by which the communication processing unit 31 calculates the second output target value of the output control unit 32 is the same as the calculation method described in Patent Document 2. As described in Patent Document 2, the calculation formulas set in the communication processing unit 21 and the communication processing unit 31 are the same as those set in each other, but the constraints set in them are different. The communication processing unit 31 outputs the calculated second output target value to the output control unit 32.
[0038] The output control unit 32 receives a second output target value from the communication processing unit 31 and performs output control so that the output power of the second power device B2 becomes the second output target value. The output power of the output control unit 32 (first power device B1) is sometimes called the "PCS output." PCS is an abbreviation for power conditioner. When the second output target value is a positive value, the second power device B2 outputs power from the distributed power source side to the grid side. On the other hand, when the second output target value is a negative value, the second power device B2 outputs power from the grid side to the distributed power source side. The output control unit 32 transmits the PCS output information to the processing unit A1 via the communication processing unit 31. The output control unit 32 transmits the PCS output information at predetermined intervals (second output power transmission cycles). The power system S1 controls the generated power of each solar power generation unit PVU1 to PVU3 and the charging and discharging power of the second storage battery BT2 through the control of the output power by the second power device B2 (output control unit 32).
[0039] Next, the changes to the received control command values (received first induction command value and received second induction command value) performed by the second processing unit 12 will be explained with reference to Figure 2. The operational objective of the power system S1 is, for example, to effectively utilize electricity generated from renewable energy, and in this embodiment, to effectively utilize the electricity generated by multiple photovoltaic power generation units PVU1 to PVU3. When the power system S1 controls the output of each first power device B1 and second power device B2 using the control command values (first induction command value and second induction command value) calculated by the first processing unit 11, it may suppress the power generation by each photovoltaic power generation unit PVU1 to PVU3. For example, in a situation where each first power device B1 discharges the first battery BT1 (electric vehicle) and supplies power to the load L, and the second power device B2 also supplies power to the load L, if the power supplied to the load L is greater than the power consumed by the load L, the power generation by each photovoltaic power generation unit PVU1 to PVU3 may be suppressed in order to reduce the power supplied from the second power device B2 to the load L. Therefore, the power system S1 increases the output power of the second power device B2 by changing the transmitted first induction command value to a value different from the received first induction command value using the second processing unit 12. Figure 2 is a schematic diagram showing the operation of the second processing unit 12 to change the control command value. In the example shown in Figure 2, the received first induction command value and the transmitted first induction command value are different, and the received second induction command value and the transmitted second induction command value are the same. In Figure 2, the first induction command value is labeled "Pr1" and the second induction command value is labeled "Pr2".
[0040] In the example shown in Figure 2(a), the second processing unit 12 modifies the received second induction command value according to a predetermined correction algorithm X to obtain the transmitted first induction command value. In other words, Figure 2(a) is an example of modification by reallocation of the received first induction command value and the received second induction command value, and correction by the correction algorithm X. In the example shown in Figure 2(b), the second processing unit 12 modifies the received first induction command value according to a predetermined correction algorithm X to obtain the transmitted first induction command value. In other words, Figure 2(b) is an example of modification by correction by the correction algorithm X. In the example shown in Figure 2(c), the second processing unit 12 uses the received second induction command value as the transmitted first induction command value without modification. In other words, Figure 2(c) is an example of modification by reallocation of the received first induction command value and the received second induction command value. Then, in Figures 2(a) to (c), the second processing unit 12 transmits the generated transmitted first induction command value to each first power device B1. On the other hand, as shown in Figures 2(a) to (c), the second processing unit 12 uses the received second induction command value as the transmitted second induction command value without changing it, and transmits the transmitted second induction command value to the second power unit B2. The second processing unit 12 performs one of the processes shown in Figures 2(a) to (c) to set the transmitted first induction command value (modified first induction command value) to a value that charges each first battery BT1, or to a value that suppresses the discharge of each first battery BT1. This causes each first power unit B1 to either charge the first battery BT1 or to suppress the discharge of the first battery BT1. As a result of this charging or discharge suppression of the first battery BT1, the connection point power changes (decreases), and in accordance with this change (decrease), the second induction command value calculated by the first processing unit 11 changes to a value that increases the output power of the second power unit B2. As a result, the output power of the second power device B2 increases, eliminating the need to suppress the power generation of each solar power generation unit PVU1 to PVU3. Therefore, the power system S1 achieves its operational objective of effectively utilizing the power generated by each solar power generation unit PVU1 to PVU3. Furthermore, as described above, the power system S1 also achieves its system objective of setting the connection point power to the target power, since the calculated value of the second induction command changes with the change in connection point power.
[0041] Furthermore, in order to achieve the above operational objectives, the power system S1 limits the upper limit of the second induction command value for the second power device B2 by the second processing unit 12. In the power system S1, the second battery BT2 is charged when its charge rate decreases. At this time, if the first power device B1 and the second power device B2 control their output using the control command values (first induction command value and second induction command value) calculated by the first processing unit 11, power may be supplied to the second battery BT2 in excess of the allowable charging power corresponding to the charge C rate set for the second battery BT2. In this case, there is a risk of overcharging the second battery BT2. Therefore, in order to keep the power supplied to the second battery BT2 below the allowable charging power corresponding to the charge C rate of the second battery BT2, the power generated by each solar power generation unit PVU1 to PVU3 may be suppressed. Therefore, in the power system S1, as described above, the upper limit of the second induction command value is limited, and the amount of power supplied from the second power device B2 to the second battery BT2 is adjusted.
[0042] The second processing unit 12, when the received second induction command value from the first processing unit 11 exceeds a predetermined upper limit, limits the received second induction command value to the said upper limit and changes it to a modified second induction command value. At this time, the second processing unit 12 changes the upper limit for the second induction command value according to the total output of the power generation unit. For example, if the total output of the power generation unit is large, the upper limit is reduced to reduce the output power from the second power device B2 to the second battery BT2. On the other hand, if the total output of the power generation unit is small, the upper limit is increased to increase the output power from the second power device B2 to the second battery BT2. In this way, the second processing unit 12 adjusts the output power of the second power device B2 by changing the upper limit according to the total output of the power generation unit. The change in the upper limit of the second induction command value performed by the second processing unit 12 may be changed linearly using a predetermined calculation formula using the total output of the power generation unit, or it may be changed in steps by dividing the total output of the power generation unit into predetermined ranges. This ensures that the power supplied to the second battery BT2 does not exceed the allowable charging power corresponding to the charging C rate of the second battery BT2, without suppressing power generation by each of the solar power generation units PVU1 to PVU3. Therefore, the power system S1 can effectively utilize the power generated by each of the solar power generation units PVU1 to PVU3. In addition, the second function prevents the power supplied to the second battery BT2 from exceeding the charging power corresponding to the charging C rate of the second battery BT2, thus suppressing overcharging of the second battery BT2.
[0043] As described above, in the power system S1, the first processing unit 11 calculates control command values (first induction command value and second induction command value) to achieve the system objective, and the second processing unit 12 modifies the control command values calculated by the first processing unit 11 to achieve the operational objective. Then, one of the multiple first power devices B1 and second power devices B2 controls the output power based on the control command value calculated by the first processing unit 11 (control command value before modification), thereby achieving the system objective. In addition, the other of the multiple first power devices B1 and second power devices B2 control the output power based on the control command value modified by the second processing unit 12 (modified control command value), thereby achieving the operational objective. In other words, the power system S1 performs power control to achieve operational objectives that differ from the system objective while achieving the system objective set for the entire system. Furthermore, as described above, the power system S1 adjusts the output power of the second power device B2 according to the total output of the power generation units. This ensures that the power supplied to the second battery BT2 does not exceed the allowable charging power corresponding to the charging C rate of the second battery BT2, without suppressing power generation by each of the solar power generation units PVU1 to PVU3. As a result, the power system S1 allows each of the solar power generation units PVU1 to PVU3 to output as much power as possible, thus effectively utilizing the power generated by each of the solar power generation units PVU1 to PVU3. Therefore, the power system S1 can effectively utilize power generated from renewable energy while controlling the power of the entire system.
[0044] Next, we will explain what happens when an abnormality occurs in the power system S1. Depending on the location of the abnormality, the power system S1 selectively continues or stops power generation by the multiple solar power generation units PVU1 to PVU3. In addition, when such an abnormality occurs, the power system S1 may appropriately interrupt the achievement of the above system objectives and operational objectives. In this embodiment, we will explain in order what happens when the first to third abnormalities described below occur as abnormalities.
[0045] The first abnormality includes, for example, a failure of the first processing unit 11, a communication abnormality between the first processing unit 11 and the second processing unit 12, a communication abnormality between the first processing unit 11 and the detection device D1, and a data abnormality in the received control command value received by the second processing unit 12, as shown in Figure 3. If any of these abnormalities (first abnormality) occurs, the second processing unit 12 cannot properly receive the received control command value from the first processing unit 11. As a result, the second processing unit 12 is unable to generate an appropriate transmission control command value. On the other hand, in the case of the first abnormality, the equipment connected to the power network itself is normal. Therefore, when the first abnormality occurs, the second processing unit 12 transmits the transmission control command value that was transmitted immediately before the first abnormality occurred. This maintains the state immediately before the first abnormality occurred, allowing each solar power generation unit PVU1 to PVU3 to continue generating electricity. Alternatively, when the first abnormality occurs, the second processing unit 12 transmits a value (set value) that has been set in advance for the first abnormality as the transmission control command value. This ensures that power supply from the second power device B2 continues to be maintained to the minimum required load L's power consumption, allowing each solar power generation unit PVU1 to PVU3 to continue generating power. As described above, even if the first abnormality occurs, the power system S1 can utilize the power generated by each solar power generation unit PVU1 to PVU3. The second processing unit 12 detects the occurrence of the first abnormality based on the following criteria, for example. Specifically, if the second processing unit 12 does not receive a received control command value from the first processing unit 11 for a predetermined time (for example, the above processing cycle), it performs error detection on the received control command value. If this error detection determines that an error has occurred in the received control command value, or if it receives an abnormality signal (a signal indicating an abnormality in the detection device D1) from the processing device A1, it detects that the first abnormality has occurred. A well-known method can be used for error detection.
[0046] The second abnormality includes, for example, a communication error between the second processing unit 12 and one of the multiple photovoltaic units PVU1 to PVU3, a failure of the overcurrent detection board 54, or a communication error between the overcurrent detection board 54 and the second processing unit 12, as shown in Figure 4. If any of these abnormalities (second abnormality) occurs, the second processing unit 12 cannot properly acquire the information necessary to generate the transmission control command value (information necessary to change the reception control command value). Therefore, the second processing unit 12 cannot receive, for example, the status of each photovoltaic unit PVU1 to PVU3 and information on C-rate over-contacts from the overcurrent detection board 54, and thus cannot generate an appropriate transmission control command value. On the other hand, in the case of the second abnormality, each of the first power devices B1 and the second power devices B2 is normal. Therefore, when the second abnormality occurs, the second processing unit 12 continues power generation by one photovoltaic unit PVU1 and stops power generation by the other photovoltaic units PVU2 and PVU3, as shown in Figure 4. At this time, the electromagnetic contactors MC2 and MC3, to which the solar power generation units PVU2 and PVU3 are connected, are opened. As a result, even if the second abnormality occurs, the power system S1 can utilize the power generated by solar power generation unit PVU1 because power generation by solar power generation unit PVU1 continues. In the state where the second abnormality occurs, the second power device B2 is operating normally, just as in the case of the first abnormality, so the power system S1 can output the power generated by each solar power generation unit PVU1 to PVU3. However, if the power generated by multiple solar power generation units PVU1 to PVU3 is all output, there is a risk of overcharging the second battery BT2 and causing it to malfunction. However, if only one solar power generation unit PVU1 is generating power, the possibility of overcharging the second battery BT2 is low, so it is possible to continue generating power only from one solar power generation unit PVU1 when the second abnormality occurs. In Figure 4, an example is shown in which power generation by the PVU1 solar power generation unit is continued, but power generation may be continued by any of the other PVU2 or PVU3 solar power generation units instead of PVU1. The second processing unit 12 detects the occurrence of the second abnormality, for example, based on the following criteria.This is because if signals from each of the photovoltaic power generation units PVU1 to PVU3 are not received for a predetermined time (for example, the above-mentioned power generation transmission cycle), or if the charging current of the second battery BT2 exceeds the current based on the charging C rate, but the C rate overload contact information signal from the overcurrent detection board 54 is not received, the second abnormality is detected. The second processing unit 12 can determine whether the charging current of the second battery BT2 exceeds the current based on the charging C rate from the above-mentioned PCS output and the power generated by each of the multiple photovoltaic power generation units PVU1 to PVU3.
[0047] The third abnormality includes, for example, a communication abnormality between the second processing unit 12 and the second power unit B2, a communication abnormality between the second power unit B2 and the energy storage unit C1, a failure of the second battery BT2, and a tripping abnormality of each circuit breaker CB1 to CB3, as shown in Figure 5. A tripping abnormality refers to an abnormality where each circuit breaker CB1 to CB3 fails to trip when it should. If any of these abnormalities (third abnormality) occurs, the second power unit B2 will stop or will not be able to receive the transmission control command value from the second processing unit 12, and will therefore be unable to properly control the output power. In this state, if power generation by each solar power generation unit PVU1 to PVU3 continues, there is a risk of further failures occurring. Therefore, when the third abnormality occurs, the second processing unit 12 stops all power generation by the multiple solar power generation units PVU1 to PVU3, as shown in Figure 5. At this time, all of the multiple electromagnetic contactors MC1 to MC3 are opened. This allows the power system S1 to suppress the occurrence of further failures, and thus reduces damage to the power system S1. The second processing unit 12 detects the occurrence of a third abnormality based on the following criteria, for example: The second processing unit 12 detects that a third abnormality has occurred if it does not receive a signal from the second power device B2 for a predetermined time (for example, the second output power transmission cycle described above), if it receives an abnormal signal from the second power device B2 (a signal indicating a communication abnormality with the energy storage device C1 or an abnormality in the second battery BT2), or if it receives an abnormal signal from any of the multiple circuit breakers CB1 to CB3 (a signal indicating an abnormality in each of the circuit breakers CB1 to CB3).
[0048] As described above, when an abnormality occurs in the power system S1, it selectively continues or stops power generation by multiple photovoltaic units PVU1 to PVU3 depending on the location of the abnormality. The abnormality in this embodiment includes the first abnormality and the second abnormality, and the following processing is performed in each of the first and second abnormalities. When the first abnormality occurs, the power system S1 continues to transmit the transmission control command value that was transmitted immediately before the first abnormality occurred, or transmits the set value for the first abnormality as the transmission control command value. As a result, power generation by each photovoltaic unit PVU1 to PVU3 continues by maintaining the state at the time of the first abnormality or by supplying power from the second power device B2 only to the minimum required amount of power consumption of load L. Therefore, even if the first abnormality occurs, the power system S1 can utilize the power generated by each photovoltaic unit PVU1 to PVU3. Furthermore, when the second abnormality occurs, the power system S1 continues power generation by one of the multiple photovoltaic units PVU1 to PVU3 and stops power generation by the others. As a result, even if a second abnormality occurs in the power system S1, it can still utilize the power generated by one of the multiple solar power generation units PVU1 to PVU3. Therefore, even if an abnormality occurs in the power system S1, it is possible to utilize the power generated by each of the solar power generation units PVU1 to PVU3 as much as possible.
[0049] Furthermore, the abnormality in this embodiment further includes the third abnormality described above, in which the power system S1 stops all power generation by the multiple photovoltaic units PVU1 to PVU3. This allows the power system S1 to suppress the occurrence of failures that could occur if power generation by each photovoltaic unit PVU1 to PVU3 were to continue when the third abnormality occurs. Therefore, the power system S1 can suppress further damage to the power system S1 that may occur when the third abnormality occurs. In other words, the power system S1 can suppress further damage while making the most of the power generated by each photovoltaic unit PVU1 to PVU3.
[0050] In the above embodiment, an example was shown in which the processing unit A1 is equipped with a first processing unit 11 and a second processing unit 12. However, the first processing unit 11 and the second processing unit 12 may be provided in different devices, respectively. In this configuration, for example, a device equipped with the first processing unit 11 and a device equipped with the second processing unit 12 may be provided separately.
[0051] In the above embodiment, the power system S1 was equipped with one second power device B2, but it may be equipped with multiple second power devices B2 connected in parallel to each other to the AC line 91. Each of the multiple second power devices B2 performs power control based on a common first induction command value. In this case, each of the multiple second power devices B2 is provided with one or more photovoltaic power generation units, one or more electromagnetic contactors, one or more circuit breakers, and one or more energy storage devices. Each second power device B2 receives a control command value (second induction command value) from the processing unit A1 and performs power control based on the second induction command value.
[0052] In the above embodiment, the processing unit A1 calculates control command values (first induction command value and second induction command value) by solving a state equation, similar to the power system described in Patent Document 2, and the first power device B1 and second power device B2 perform output control in a distributed manner. In contrast to this configuration, the first processing unit 11 may calculate each first output target value and second output target value to achieve the system objective, and the second processing unit 12 may change the first output target value and second output target value to achieve the operational objective. In other words, the control command values calculated by the first processing unit 11 may not be indicators for the multiple first power devices B1 and second power devices B2 to calculate output targets in a distributed manner, but may be the first output target value of each of the multiple first power devices B1 and the second output target value of the second power device B2. Such a configuration will be described below as a second embodiment with reference to Figure 6.
[0053] Figure 6 shows a power system S2 according to the second embodiment. As shown in Figure 6, power system S2 has the same components as power system S1, but the communication network connection is different.
[0054] In the power system S2, the first processing unit 11 receives output power, rated output, and battery information of the first battery BT1 (charge rate, rated capacity, charge C rate, and discharge C rate) from each first power device B1. The first processing unit 11 receives output power, rated output, and battery information of the second battery BT2 (charge rate, rated capacity, charge C rate, and discharge C rate) from the second power device B2. The first processing unit 11 receives connection point power from the detection device D1. The first processing unit 11 acquires information such as generated power and rated output from each photovoltaic power generation unit PVU1 to PVU3. The first processing unit 11 receives information such as the status of each circuit breaker CB1 to CB3. The first processing unit 11 receives information such as C rate over-contact from the overcurrent detection board 54. The first processing unit 11 then calculates the first output target value for each of the multiple first power devices B1 and the second output target value for the second power device B2 based on the received information and the target power. Thus, the first processing unit 11 calculates the first output target value for each of the multiple first power devices B1 and the second output target value for the second power device B2 in order to achieve the system objective. The first processing unit 11 then transmits the calculated multiple first and second output target values to the second processing unit 12.
[0055] The second processing unit 12 modifies the received first output target values and second output target values in order to achieve the above operational objective. Then, the second processing unit 12 transmits the modified values of the modified first output target values and second output target values, and the original values of the values that remain unchanged, to the multiple first power units B1 and second power units B2, respectively.
[0056] Each of the multiple first power devices B1 performs output control based on the pre- or post-change first output target value received from the second processing unit 12, and the second power device B2 performs output control based on the pre- or post-change second output target value received from the second processing unit 12. Therefore, in the power system S2, the multiple first power devices B1 and the second power devices B2 do not calculate multiple first and second output target values, respectively.
[0057] In the power system S2 configured as described above, similar to power system S1, the first processing unit 11 calculates control command values (first output target value and second output target value) to achieve the system objective, and the second processing unit 12 modifies the control command values calculated by the first processing unit 11 to achieve the operational objective. Therefore, power system S2, like power system S1, can achieve both the system objective and the operational objective, making it possible to effectively utilize electricity generated from renewable energy while controlling the power of the entire system.
[0058] The power system relating to this disclosure is not limited to the embodiments described above. The specific configuration of each part of the power system relating to this disclosure can be modified in various ways. [Explanation of Symbols]
[0059] S1, S2: Power system, A1: Processing unit, 11: First processing unit, 12: Second processing unit, B1: First power unit, B2: Second power unit, 91: AC line, 92: DC line, BT1: First battery, BT2: Second battery, PVU1~PVU3: Photovoltaic power generation unit
Claims
1. A power system that controls the connection point power at the connection point with the power grid, The first battery, A first power device to which the first storage battery is connected and which performs charging and discharging of the first storage battery, Each of the following is a power generation unit that generates electricity using renewable energy, The second battery, The at least one power generation unit and the second battery are connected via a common DC line, and a second power device is used to charge and discharge the second battery. A first processing unit calculates a control command value to achieve a system objective that sets the connection point power to a target power, A second processing unit modifies the control command value calculated by the first processing unit to achieve an operational objective different from the system objective, and generates a transmission control command value to be transmitted to the first power unit and the second power unit, respectively, using the control command value before modification and the control command value after modification. Equipped with, One of the first power device and the second power device receives the control command value before the change as the transmission control command value, and controls the output power of its own device based on the control command value before the change. A power system in which the other of the first and second power devices receives the modified control command value as the transmission control command value and controls the output power of its own device based on the modified control command value.
2. The control command value includes the induction command value for the second power device, If the guidance command value calculated by the first processing unit exceeds the upper limit set for that guidance command value, the second processing unit changes the guidance command value calculated by the first processing unit to a value limited to that upper limit as the modified guidance command value. The power system according to claim 1, wherein the upper limit is changed by the second processing unit according to the total value of the power generated by the at least one power generation unit.
3. The power system according to claim 1, wherein when a first abnormality occurs in which the second processing unit is unable to properly receive the control command value from the first processing unit, the second processing unit continues to transmit the transmission control command value transmitted immediately before the occurrence of the first abnormality, or transmits a set value for the first abnormality as the transmission control command value.
4. The at least one power generation unit includes a first power generation unit and one or more second power generation units. The power system according to claim 1 or 2, wherein when a second abnormality occurs in which the second processing unit is unable to obtain information for generating the transmission control command value, the first power generation unit continues to generate power and the one or more second power generation units stop generating power.
5. The aforementioned at least one power generation unit includes a plurality of power generation units, The power system according to any one of claims 1 to 3, wherein when a third abnormality occurs in which the second power device is unable to perform output control, all power generation by the plurality of power generation units is stopped.
6. Each of the aforementioned at least one power generation unit is a solar power generation unit that generates electricity using solar energy. The first storage battery is installed in an electric vehicle, as described in any one of claims 1 to 3.