Power converters, and power systems using power converters

Abstract

To provide a power system that can easily accommodate changes in the system configuration, and a power converter used in the power system.SOLUTION: A power system includes DC equipment (1), a DC power supply bus 4 that supplies power to the DC equipment, a power converter (2) capable of charging and discharging power to the DC power supply bus 4, a general control device that controls the DC equipment, and an Ethernet line 7 that connects the DC equipment, the power converter, and the general control device. The power converter receives a communication message including DC equipment-related information, which is information about the DC equipment, via the Ethernet line 7, acquires the DC equipment-related information from the communication message, and charges and discharges the DC power supply bus 4 on the basis of the acquired DC equipment-related information.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power converter and a power system using a power converter, and more particularly to a power system used for supplying DC power to an electric motor system, such as a motor. [Background technology]

[0002] Patent Document 1 describes a DC power supply system comprising a renewable energy power generation device, load equipment, and a storage battery, each connected to a DC bus via DC / DC converters, and a power management device. The storage battery charges the generated power and discharges it to the load equipment based on the relative magnitudes of the generated power and the load power. The power management device manages the operation of each DC / DC converter based on the amount of generated power, the amount of load power, etc. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2020 / 161765 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In recent years, the utilization of renewable energy has attracted attention as one measure to combat global warming. In DC power supply systems, particularly for renewable energy sources such as solar power generation or power transmission from DC devices such as batteries, the number of power conversion stages can be reduced compared to AC power supply. This results in the advantage of low losses. In realizing such DC power supply systems, power flow management of the DC power supply bus is generally a crucial technical challenge.

[0005] For example, if we consider a motor drive inverter as a DC load, in addition to managing power consumption during motor acceleration, it is also expected that the power regenerated during motor deceleration will be reused in the DC power supply bus. In this way, the voltage of the DC power supply bus must be maintained within an appropriate range without becoming overvoltage or undervoltage, given the power flowing in and out of the DC power supply bus.

[0006] In this context, for example, Patent Document 1 describes a method for operating and managing DC power supply and storage batteries in a system that includes a group of converters connected to a DC power supply bus and a power management device that manages them. This method centrally manages the power of each individual DC device in a system to which various DC devices are connected.

[0007] However, with this method, if there are changes to the system configuration, such as the introduction of new DC equipment, it becomes necessary to revise the operating policy for the power management device or perform necessary modifications for communication with the power management device. As a result, trial periods for various adjustments may be prolonged and the amount of work required may increase, making it difficult to easily adapt to changes in the system configuration.

[0008] The present invention has been made in view of the above-mentioned problems, and one of its objectives is to provide a power system that can easily accommodate changes in system configuration, and a power converter used in said power system.

[0009] The aforementioned and other objects and novel features of the present invention will become apparent from the description herein and the accompanying drawings. [Means for solving the problem]

[0010] A power system according to an embodiment includes at least one DC device, a DC power supply bus that supplies power to the DC device, a power converter that can charge and discharge power with respect to the DC power supply bus, a general control device that controls the DC device, and an Ethernet (registered trademark) line that connects the DC device, the power converter, and the general control device. The power converter receives a communication message including DC device related information, which is information regarding the DC device, via the Ethernet line, obtains the DC device related information from the communication message, and charges and discharges the DC power supply bus based on the obtained DC device related information.

Advantages of the Invention

[0011] According to the above embodiment, a power system that can easily cope with changes in system configuration can be realized.

Brief Description of the Drawings

[0012] [Figure 1] It is a schematic diagram showing a configuration example of a power system according to the first embodiment. [Figure 2] It is a block diagram showing a detailed configuration example of the inverter in FIG. 1. [Figure 3A] It is a block diagram showing a detailed configuration example of the DC / DC converter in FIG. 1. [Figure 3B] It is a block diagram showing a detailed configuration example of the communication controller in FIG. 3A. [Figure 4] It is a sequence diagram showing a schematic operation example of the power system shown in FIG. 1. [Figure 5A] It is a schematic diagram for explaining an example of the processing content using the communication message transmitted in the operation in FIG. 4. [Figure 5B] It is a schematic diagram for explaining an example of the processing content using the communication message transmitted in the operation in FIG. 4. [Figure 5C] It is a schematic diagram for explaining an example of the processing content using the communication message transmitted in the operation in FIG. 4. [Figure 6] In FIG. 3B, it is a diagram showing an example of the processing content of the user interface and an example of the display content in the parameter setting unit. [Figure 7A] Figure 3B schematically illustrates an example of operation based on a charge / discharge algorithm that assumes an inverter operating pattern in the control command value generation unit shown. [Figure 7B] Figure 7A is a flowchart showing an example of the main processing performed by the communication controller shown in Figure 3B. [Figure 8A] Figure 3B schematically illustrates another example of operation in the control command value generation unit shown, based on a charge / discharge algorithm that assumes an inverter operating pattern. [Figure 8B] Figure 8A is a flowchart showing an example of the main processing performed by the communication controller shown in Figure 3B. [Figure 9A] Figure 3B schematically illustrates another example of operation in the control command value generation unit shown, based on a charge / discharge algorithm that assumes an inverter operating pattern. [Figure 9B] Figure 9A is a flowchart showing an example of the main processing performed by the communication controller shown in Figure 3B. [Figure 10] This is a schematic diagram showing an example of the configuration of a power system according to the second embodiment. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the drawings. The embodiments are illustrative examples for explaining the present invention, and have been omitted and simplified as appropriate for clarity of explanation. The present invention can also be implemented in various other forms. Unless otherwise specified, each component may be singular or plural. The position, size, shape, and range of each component shown in the drawings may not represent the actual position, size, shape, and range in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the position, size, shape, and range disclosed in the drawings.

[0014] Examples of various types of information may be described using terms such as "table," "list," and "queue," but these types of information may also be represented by other data structures. For example, various types of information such as "XX table," "XX list," and "XX queue" may be referred to as "XX information." When describing identification information, terms such as "identification information," "identifier," "name," "ID," and "number" are used, and these terms are interchangeable.

[0015] Furthermore, if there are multiple components with the same or similar function, different subscripts may be assigned to the same code to describe them. For example, if the code for one component is "1", multiple components may be distinguished as "1A", "1B", etc. If it is not necessary to distinguish these multiple components, the subscript may be omitted in the description.

[0016] In the embodiments described, the processes performed by executing a program may be explained. As an example, a computer executes a program using a processor (e.g., CPU, GPU) and performs the processing defined in the program using memory resources (e.g., memory) and interface devices (e.g., communication ports). Therefore, the main entity performing the processing by executing the program may be the processor. Alternatively, the main entity performing the processing by executing the program may be a controller, device, system, computer, or node having a processor.

[0017] Furthermore, the main component performing the processing executed by the program can be an arithmetic unit, and may include dedicated circuits for specific processing. Here, dedicated circuits include, for example, FPGAs (Field Programmable Gate Arrays), ASICs (Application Specific Integrated Circuits), and CPLDs (Complex Programmable Logic Devices).

[0018] The program may be installed on the computer from the program source. The program source may be, for example, a program distribution server or a storage medium readable by the computer. If the program source is a program distribution server, the program distribution server includes a processor and storage resources for storing the program to be distributed, and the processor of the program distribution server may distribute the program to other computers. In addition, in the embodiment, two or more programs may be implemented as one program, or one program may be implemented as two or more programs.

[0019] (First Embodiment) <Configuration of the power system> Figure 1 is a schematic diagram showing an example of the configuration of a power system according to the first embodiment. The power system consists of the parts shown in Figure 1, excluding motors 3A, 3B, and 3C. Inverters 1A, 1B, and 1C are examples of DC equipment. The DC inputs of inverters 1A, 1B, and 1C are connected in parallel to a common DC power supply bus 4. As a result, the DC power supply bus 4 supplies DC power to inverters 1A, 1B, and 1C, respectively.

[0020] Furthermore, the DC power supply bus 4 is connected to the power system 40 via an AC / DC converter 41. In addition, a DC capacitor 42 is connected to the DC power supply bus 4 to maintain the power of the DC power supply bus 4. The DC capacitor 42 may be mounted inside, for example, the AC / DC converter 41 or inverters 1A, 1B, and 1C.

[0021] The AC / DC converter 41 converts AC power from the power grid 40 into DC power and supplies it to the DC power supply bus 4. Furthermore, the AC / DC converter 41 may also convert DC power from the DC power supply bus 4 into AC power and supply it to the power grid 40. The AC / DC converter 41 may be composed of, for example, a rectifier using diodes or thyristors, or a bidirectional grid-connected inverter using IGBTs (Insulated Gate Bipolar Transistors) or FETs (Field Effect Transistors).

[0022] Motors 3A, 3B, and 3C are connected to the AC outputs of inverters 1A, 1B, and 1C, respectively. Inverters 1A, 1B, and 1C convert DC power from the DC power supply bus 4 into AC power to rotate motors 3A, 3B, and 3C. In this way, an electric motor system is constructed by motors 3A, 3B, and 3C and the power system that drives them. Motors 3A, 3B, and 3C can generate regenerative power, for example, during deceleration. A portion of this regenerative power is stored in the system in the form of charging the DC capacitor 42 and can be reused in subsequent powering operations.

[0023] Here, since the capacitance of the DC capacitor 42 is finite, if the capacitance is insufficient for the regenerative power, a battery 5 for absorbing the regenerative power can be separately connected to the DC power supply bus 4. In this case, in order to control the charging and discharging of the battery 5, it is desirable to provide a DC / DC converter 2 capable of bidirectional charging and discharging, as shown in Figure 1.

[0024] DC / DC converters 2A and 2B are examples of power converters capable of charging and discharging power to the DC power supply bus 4. One end of DC / DC converters 2A and 2B is connected in parallel to the DC power supply bus 4, and the other end is connected to batteries 5A and 5B, respectively. As a result, DC / DC converters 2A and 2B charge and discharge a portion of the energy from the DC power supply bus 4 to batteries 5A and 5B.

[0025] The batteries 5A and 5B and the DC / DC converters 2A and 2B should be connected not only by the positive and negative power wiring of the batteries 5A and 5B, but also by control wiring for communication and operation. For example, in lithium-ion batteries, it is common to incorporate a battery controller to manage the cell voltage and temperature inside the battery. In this case, the DC / DC converters 2A and 2B receive safety information of the lithium-ion battery detected by the battery controller via the control wiring. Then, a protection circuit provided in the DC / DC converter 2 protects the battery 5 by stopping charging and discharging when an emergency condition is detected based on the safety information.

[0026] Furthermore, batteries 5A and 5B can be used not only to assist the DC capacitor 42, but also to provide backup power. In other words, batteries 5A and 5B supply power to the DC power bus 4 so that inverters 1A, 1B, and 1C can operate normally in the event of a malfunction in the power system 40. Various types of batteries can be used for battery 5, including lithium-ion batteries, capacitors using electric double layers, nickel-metal hydride batteries, and lead-acid batteries.

[0027] Here, the electric machinery system shown in Figure 1 is assumed to be a system that uses the power of multiple motors simultaneously, such as a factory production line or machine tool. In this case, the inverters that drive the motors are generally configured to receive commands from an external central control unit via communication to perform the desired operation. Therefore, inverters 1A, 1B, and 1C each have a communication port and are connected to an external communication master 6 by wire or wireless.

[0028] For example, wired communication can be any standard specification such as RS-485, CAN, or Ethernet. In particular, in Figure 1, inverters 1A, 1B, and 1C each have two or more Ethernet ports and are connected in series via a daisy-chain type Ethernet line 7. EtherCAT (registered trademark) is a well-known standard specification for industrial communication using such a configuration.

[0029] In EtherCAT, the communication master 6 sends a series of frames containing commands for all slaves, in other words, a communication message. The communication master 6 is part of the central control unit. On the other hand, each slave (in this case, an inverter) reads only a portion of the incoming batch of commands corresponding to its own station number on the fly, and then writes the necessary information to a portion of the area corresponding to its own station number, also on the fly. This method enables EtherCAT to achieve high-speed transmission by eliminating the handshake between master and slaves, and also enables synchronous operation of multiple slaves by managing the timing of sending and receiving batch commands.

[0030] In Figure 1, the Ethernet line 7 is connected starting from the communication master 6, passing through inverters 1A, 1B, and 1C in order, and then through DC / DC converters 2A and 2B in order. After that, either a loop-type connection configuration is used in which DC / DC converter 2B is connected to the communication master 6, or a loopback-type connection configuration is used in which communication is looped back at DC / DC converter 2B.

[0031] The communication master 6 is composed of, for example, a programmable logic controller equipped with calculation functions. Furthermore, the communication master 6 may be connected to a calculation device 62, such as a server, via a wide-area communication network 61, and configured to exchange operating software for the electric machinery system with the calculation device 62.

[0032] As described above, in Figure 1, a daisy-chain type Ethernet circuit 7 is provided, and DC / DC converters 2A and 2B, which are power converters, are connected downstream of the DC devices, inverters 1A, 1B, and 1C. This allows the power converters located downstream to directly access information written by the DC devices located upstream during the frame cycle, such as DC device-related information concerning the rotation control of motor 3. In other words, the power converters can directly acquire information about the DC devices connected to the DC power supply bus 4 without going through a power management device that handles centralized management as in the past, and can charge and discharge the DC power supply bus 4 based on that information.

[0033] As a result, the power converter can detect the status of DC equipment with minimal time delay and respond quickly to the status of DC equipment, i.e., perform charging and discharging. This improves the responsiveness of the power converter in the power system. Furthermore, when adding or removing DC equipment or batteries to the DC power supply bus 4, that is, when changing the system configuration of the power system, modifications to the power management device become unnecessary. Therefore, the prolonged trial period and increased labor associated with modifications can be suppressed, and changes in system configuration can be easily accommodated.

[0034] <Details of Inverter (DC Equipment)> Figure 2 is a block diagram showing a detailed configuration example of the inverter 1 in Figure 1. The main circuit of the inverter 1 consists of an inverter conversion circuit 11, which is a power conversion circuit, a motor-side sensor 12 provided on the AC side of the inverter conversion circuit 11, and a DC bus-side sensor 16 provided on the DC side. The inverter conversion circuit 11 includes a plurality of switching elements, which are power semiconductor elements, and converts between DC power and AC power by switching by the plurality of switching elements.

[0035] The communication controller 10 receives and interprets a group of frames (communication messages) transmitted from the communication master 6 in Figure 1 via the Ethernet line 7. The communication controller 10 then selects the position command value P necessary for motor rotation control from the frame group. * Speed ​​command value S * Torque command value T * The system acquires values ​​such as these and outputs these control command values ​​to the motor rotation control unit 14.

[0036] Meanwhile, the state monitor unit 13 receives input such as the motor currents Iu, Iv, and Iw detected by the motor-side sensor 12, and the DC bus voltage Vdci and DC bus current Idci detected by the DC bus-side sensor 16. The state monitor unit 13 then acquires the input information or the calculation results based on it as sensor information. For example, the state monitor unit 13 can acquire the DC bus power obtained by calculating the DC bus voltage Vdci and the DC bus current Idci as sensor information.

[0037] The communication controller 10 receives sensor information acquired by the status monitor unit 13 and calculation information related to motor rotation control generated in the motor rotation control unit 14. The communication controller 10 then transmits the information to the outside by writing the input information into a frame group (communication message) as DC equipment-related information. As a result, the inverter 1 located upstream of the Ethernet line 7 can transmit its inverter status to equipment located downstream.

[0038] The motor rotation control unit 14 controls the rotation of the motor 3 primarily by controlling the switching in the inverter conversion circuit 11 based on the deviation between the control command value and the actual detected value. Various control methods are known for use in the motor rotation control unit 14. Figure 2 shows an example configuration of a motor rotation control unit 14 that performs a typical control method, a three-stage loop control of position, speed, and torque.

[0039] In the motor rotation control unit 14, the first-stage position control block controls the position command value P * The motor position command value Pref is converted to a motor position command value Pref through a predetermined filtering process. The position control block calculates a position deviation amount, which is the difference between the motor position command value Pref and the position information Pfb detected by the position detector 31 provided on the motor shaft. The position control block then calculates a manipulated variable corresponding to the speed command value of the next stage by proportional-integral control using position control gains Kpp and Kpi, so that the position deviation amount approaches zero.

[0040] The next speed control block uses the control command switching unit 15A to obtain the speed command value S from the position control block or the speed command value S from the communication controller 10. * One of the following is selected and converted to a motor speed command value Sref through a predetermined filtering process. The speed control block then calculates a speed deviation, which is the difference between the motor speed command value Sref and the speed detection value Sfb estimated by the derivative of the position information Pfb. The speed control block then calculates a manipulated variable corresponding to the final stage torque command value using proportional-integral control with speed control gains Ksp and Ksi, so that the speed deviation approaches zero.

[0041] The final stage torque control block uses the control command switching unit 15B to obtain the torque command value T from the speed control block or the torque command value T from the communication controller 10. * One of the following is selected and converted to motor torque command value Tref and DQ axis current command values ​​Idref,Iqref through a predetermined filtering process. The torque control block also calculates the current deviation, which is the difference between the DQ axis current command values ​​Idref,Iqref and the DQ axis current detection values ​​Id,Iq estimated from the motor currents Iu,Iv,Iw. The torque control block then determines the next stage's manipulated variable using proportional-integral control with current control gains Kip,Kii so that the current deviation approaches zero.

[0042] The manipulated variables obtained by the torque control block are converted into a three-phase modulated wave Fm based on a predetermined phase estimated from the motor currents Iu, Iv, Iw or position information Pfb. The pulse width modulator (PWM) generates pulse commands by comparing the three-phase modulated wave Fm with a carrier wave such as a triangular wave. The inverter conversion circuit 11 switches the on / off state of its internal switching elements based on the pulse commands. As a result, motor currents Iu, Iv, Iw are generated, power is supplied to the motor shaft, and the value of the position detector 31 changes, forming a series of feedback control systems.

[0043] In the inverter 1 shown in FIG. 2, the control circuit part excluding the main circuits (11, 12, 16) described above can be realized by an internal circuit mounted on, for example, a microcontroller or an FPGA. As a specific example, the communication controller 10 is realized by a communication interface circuit compliant with EtherCAT or the like. The pulse width modulator PWM is realized by a dedicated circuit or a timer circuit or the like. The state monitor unit 13 is realized by an analog-to-digital converter or the like. The motor rotation control unit 14 and the control command switching units 15A and 15B are realized by a processor executing a program in a memory or the like.

[0044] However, the implementation form of the control circuit is not limited to this, and it may be hardware, software, or a combination thereof. Also, any of the position control, speed control, and torque control blocks in the motor rotation control unit 14 is not limited to proportional integral control (PI control), and proportional integral derivative control (PID control) may be performed. In the example shown in FIG. 2, PID control is used in position control and speed control.

[0045] <Details of the DC / DC converter (power converter)> FIG. 3A is a block diagram showing a detailed configuration example of the DC / DC converter 2 in FIG. 1. FIG. 3B is a block diagram showing a detailed configuration example of the communication controller 20 in FIG. 3A. In FIG. 3A, the main circuit of the DC / DC converter 2 includes a converter conversion circuit 21 which is a power conversion circuit, a battery-side sensor 22 provided on the battery side of the converter conversion circuit 21, and a DC bus-side sensor 26 provided on the DC power supply bus 4 side.

[0046] The converter conversion circuit 21 includes an inductor for storing power and a plurality of switching elements for charge and discharge which are power semiconductor elements, and controls the charging / discharging of the DC power supply bus 4 and the discharging / charging of the storage battery 5 by switching by the plurality of switching elements. Also, in FIG. 3A, when the storage battery 5 incorporates a storage battery controller, the storage battery communication unit 27 is provided as an example. The storage battery communication unit 27 acquires the state information of the storage battery 5 from the storage battery controller.

[0047] As shown in FIG. 3B, the communication controller 20 includes an information acquisition circuit 250, a control command value generation unit 251, and a user interface 252. The information acquisition circuit 250 receives and interprets a group of frames (communication telegrams) in which DC device-related information is written by at least one or more DC devices, that is, one or more inverters 1, transmitted from the communication master 6 via the Ethernet line 7. Then, the information acquisition circuit 250 acquires DC device-related information from the communication telegrams, for example, information related to the rotation control of the motor.

[0048] The control command value generation unit 251 inputs the acquired DC device-related information and generates control command values such as the battery-side voltage command value V1 * , the DC bus-side voltage command value V2 * , the DC bus-side current command value I2 * , the battery-side current command value I1 * based on a predetermined charge / discharge algorithm. The control command value generation unit 251 outputs the generated control command values to the charge / discharge control unit 24. As a result, the charge / discharge control unit 24 controls the converter conversion circuit 21 in FIG. 3A based on the control command values, thereby performing charging / discharging of the DC power supply bus 4 and discharging / charging of the storage battery 5.

[0049] On the other hand, as shown in FIG. 3A, the state monitor unit 23 inputs the battery voltage V1 and battery current I1 detected by the battery-side sensor 22, the DC bus voltage V2 and DC bus current I2 detected by the DC bus-side sensor 26, and the like. Then, the state monitor unit 23 acquires the input information or the calculation result based on the input information as sensor information.

[0050] The information acquisition circuit 250 receives sensor information acquired by the state monitor unit 23, calculation information related to charge and discharge control generated in the charge and discharge control unit 24, and state information of the battery 5 from the battery communication unit 27. The information acquisition circuit 250 then transmits the information to the outside by writing the input information into a communication message as power conversion operation information. For example, if the charge and discharge power of the DC / DC converter and the state of charge (SOC) of the battery acquired from the battery controller are written as power conversion operation information, downstream devices, such as another DC / DC converter, can refer to this information.

[0051] The user interface 252 accepts operation input from the user and provides the user with various information. One of its functions is to communicate with the parameter setting unit 28 and obtain the parameters set by the user using the parameter setting unit 28. The control command value generation unit 251 generates control command values ​​or adjusts control command values ​​based on the parameters by performing calculations based on the charge / discharge algorithm using DC equipment-related information from the information acquisition circuit 250 as well as parameters from the user interface 252.

[0052] In Figure 3A, various circuit configurations are known for the converter conversion circuit 21 and the control methods used in the charge / discharge control unit 24. As a representative example, Figure 3A shows a converter conversion circuit 21 composed of a bidirectional chopper circuit and a charge / discharge control unit 24 that performs two-stage voltage / current loop control. In a bidirectional chopper circuit, for example, a boost operation can be performed in which power from the battery 5 is stored in an inductor and that power is supplied to the DC power supply bus 4, and a buck operation can be performed in which power from the DC power supply bus 4 is stored in an inductor, that power is commutated on the battery 5 side and the battery 5 is charged.

[0053] In addition to the bidirectional chopper circuit, other typical circuit configurations for the converter conversion circuit 21 include, for example, a double active bridge circuit equipped with bridge-type switching circuits at both the input and output of a high-frequency transformer. Even a converter conversion circuit 21 composed of such a double active bridge circuit can perform bidirectional charging and discharging operations.

[0054] The first stage of the charge / discharge control unit 24 is provided with a control block that controls either the battery voltage V1, the DC bus voltage V2, or the DC bus current I2. The first stage control block controls the battery-side voltage command value V1 * This is converted into a voltage command value V1ref by a predetermined filter Fil1, and the deviation between this voltage command value V1ref and the battery voltage V1 is calculated. Then, the first-stage control block calculates a manipulated variable corresponding to the current command value of the next stage by proportional-integral control using control gains Kv1p and Kv1i, so that the deviation approaches zero.

[0055] Alternatively, the first stage control block uses the DC bus voltage command value V2 * This is converted to a voltage command value V2ref by a predetermined filter Fil2, and the deviation between this voltage command value V2ref and the DC bus voltage V2 is calculated. Then, the first-stage control block calculates a manipulated variable corresponding to the current command value of the next stage by proportional-integral control using control gains Kv2p and Kv2i, so that the deviation approaches zero.

[0056] Alternatively, the first stage control block uses the DC bus side current command value I2 * This is converted to a current command value I2ref by a predetermined filter Fil3, and the deviation between the current command value I2ref and the DC bus current I2 is calculated. The first-stage control block then calculates a manipulated variable corresponding to the current command value of the next stage using proportional-integral control with control gains Ki2p and Ki2i, so that the deviation approaches zero.

[0057] The final stage of the charge / discharge control unit 24 is provided with a current control block that controls the battery current I1. The current control block in the final stage controls the three current command values ​​obtained by the three control blocks in the first stage, and the current command value I1 from the communication controller 20. * One of the options is selected using the control command switching unit 25. The final stage current control block converts the selected current command value to a current command value I1ref using a predetermined filter Fil4, and calculates the current deviation amount, which is the difference between the current command value I1ref and the battery current I1.

[0058] The final stage current control block then determines the manipulated variable for the next stage using proportional-integral control with control gains Ki1p and Ki1i so that the current deviation approaches zero. This manipulated variable is converted into a modulated wave and input to a pulse width modulator (PWM). The pulse width modulator (PWM) generates a pulse command by comparing the input modulated wave with a carrier wave such as a triangular wave. The converter circuit 21 switches the on / off state of its internal switching elements based on this pulse command. As a result, a battery current I1 is generated, and the battery voltage V1 or DC bus voltage V2 changes due to the battery current I1, forming a series of feedback control systems.

[0059] Furthermore, as in the case of Figure 2, each control block within the charge / discharge control unit 24 may be subject to proportional-integral-derivative control (PID control) as well as proportional-integral-derivative control (PI control). In addition, the filter Fil1 that outputs the battery-side voltage command value V1ref may, for example, refer to the upper / lower voltage limit VB_lim of the battery 5 obtained by the battery communication unit 27 and correct the voltage command value V1ref so that it falls within the upper and lower voltage limits. In particular, in lithium-ion batteries, electrode reactions that lead to irreversible degradation may occur when overvoltage is present, so preventing this is effective in ensuring the safety and extending the lifespan of the battery 5.

[0060] Furthermore, the filter Fil2, which outputs the DC bus voltage command value V2ref, may correct the DC bus voltage command value V2ref to lower the DC bus voltage V2, for example, when the DC bus current I2 becomes excessive. By lowering the output voltage in accordance with the output current in this way, the load can be autonomously shared, for example, when multiple DC / DC converters are operated in parallel.

[0061] Furthermore, the filter Fil3 that outputs the DC bus side current command value I2ref may, for example, refer to the DC bus voltage V2 and correct the DC bus side current command value I2ref so that the DC power supply bus 4 is discharged when the DC bus voltage V2 exceeds a predetermined value, and conversely, the DC power supply bus 4 is charged when it falls below a predetermined value. By adjusting the voltage of the DC power supply bus 4 within a predetermined range in this way, the voltage of the DC power supply bus 4 can be adjusted within a predetermined range with a short response time, even if the voltage change of the DC power supply bus 4 occurs at a speed that cannot be handled by the various command calculations of the communication controller 20.

[0062] Furthermore, the filter Fil4, which outputs the battery-side current command value I1ref, may, for example, refer to the upper / lower current limit IB_lim of the battery 5 obtained by the battery communication unit 27 and correct the battery-side current command value I1ref so that it falls within the upper and lower current limits. In particular, lithium-ion batteries often have an internal configuration in which many battery cells are connected in series. In this case, if a large current is passed when the internal resistance of some battery cells has increased, the cell voltage will rise due to the effect of voltage drop, leading to overvoltage. As mentioned above, overvoltage leads to degradation, so preventing this by limiting the current is effective in ensuring the safety and extending the lifespan of the battery 5.

[0063] In the DC / DC converter 2 shown in Figure 3A, the control circuit portion, excluding the main circuit (21, 22, 26) described above, can be implemented by internal circuits mounted on a microcontroller or FPGA, for example. Specifically, the information acquisition circuit 250 in the communication controller 20 is implemented by a communication interface circuit compliant with EtherCAT. The control command value generation unit 251 and the user interface 252 are implemented by the processor executing a program in memory. The battery communication unit 27 is implemented by a serial communication interface circuit, for example.

[0064] The pulse width modulator (PWM) is implemented by a dedicated circuit or timer circuit. The state monitor unit 23 is implemented by an analog-to-digital converter or the like. The charge / discharge control unit 24 and the control command switching unit 25 are implemented by the processor executing a program in memory. However, the implementation form of the control circuit is not limited to these; it can be hardware, software, or a combination of both.

[0065] <Overall operation of the power system> Figure 4 is a sequence diagram showing a schematic example of the operation of the power system shown in Figure 1. As shown in Figure 4, in a power system in which each device is connected in a daisy-chain configuration, a group of frames (communication messages) transmitted from the communication master 6 passes through inverters 1A, 1B, and 1C in order, and then reaches the DC / DC converter 2A. Furthermore, the communication messages pass through DC / DC converter 2A and then reach DC / DC converter 2B. After that, the communication messages are finally returned to the communication master 6 via the loop connection or return connection described in Figure 1.

[0066] Each of the DC devices, inverters 1A, 1B, and 1C, and the DC / DC converters 2A and 2B, are assigned a unique station number. Each of the inverters 1A, 1B, and 1C identifies the message frame corresponding to its station number from the communication messages and performs on-the-fly reading and writing to that message frame. The information read from the message frame at this time is, for example, control command values ​​from the communication master 6. On the other hand, the information written to the message frame is, for example, DC device-related information such as the rotational speed, torque, power, and driving status of motor 3.

[0067] Each of the DC / DC converters 2A and 2B identifies the message frame corresponding to its station number and / or the message frame corresponding to each inverter from the communication message, and performs on-the-fly reading and writing to the message frame. The information read from the message frame at this time is DC equipment-related information written by inverter 1. On the other hand, the information written to the message frame is power conversion operation information, such as the charge and discharge power when charging and discharging the DC power supply bus 4 based on the DC equipment-related information, and the charge rate of the storage battery 5.

[0068] Figures 5A, 5B, and 5C are schematic diagrams illustrating an example of processing using the communication message transmitted in the operation shown in Figure 4. In the example shown in Figure 5A, inverters 1A, 1B, and 1C each write a message, i.e., DC equipment-related information, to predetermined bit positions in the message frames D_1A, D_1B, and D_1C assigned to them, respectively.

[0069] In this case, for example, DC / DC converter 2A can obtain the status of all inverters by identifying the message frames D_1A, D_1B, and D_1C of each inverter from the received communication message and reading the information at the predetermined bit positions of each, i.e., DC equipment-related information. Note that each of the message frames D_1A, D_1B, and D_1C is one of several slots that make up a single communication message.

[0070] In the example shown in Figure 5B, inverters 1A, 1B, and 1C write DC equipment-related information to the message frames D_1A, D_1B, and D_1C assigned to their respective devices, similar to the case in Figure 5A. In addition, if a message frame assigned to another device, i.e., the next device to pass through, is provided following the message frame assigned to their own device, each of inverters 1A, 1B, and 1C also writes a message to the message frame assigned to that other device.

[0071] In this example, inverter 1A writes message M1 to message frame D_1A and then writes message M2 to message frame D_1B. Similarly, inverter 1B writes message M3 to message frame D_1B and then writes message M4 to message frame D_1C. For example, when calculating the cumulative value of predetermined values ​​for three inverters 1A, 1B, and 1C, if the summation results are transmitted sequentially, the value written to message frame D_1C of the final inverter will be the cumulative value.

[0072] As a specific example, inverter 1A writes predetermined values ​​related to itself as messages M1 and M2 to message frames D_1A and D_1B, respectively. Inverter 1B reads the predetermined value written to message M2, adds a predetermined value related to itself to that value, and writes the result to message frame D_1C as message M4, and writes a predetermined value related to itself to message frame D_1B as message M3. Inverter 1C reads the predetermined value written to message M4, adds a predetermined value related to itself to that value, and writes the result to message frame D_1C as message M5.

[0073] This allows, for example, the DC / DC converter 2A to identify the last message frame D_1C among the multiple message frames D_1A, D_1B, and D_1C included in the communication message, and to acquire the message M5 within the identified message frame D_1C as DC equipment-related information. In other words, the subsequent DC / DC converters 2A and 2B can identify the message frames D_1A, D_1B, and D_1C of all inverters, read out the information at predetermined bit positions, and obtain the integrated value of all inverters from the message frame D_1C of the last inverter 1C to pass through.

[0074] In the example shown in Figure 5C, inverters 1A, 1B, and 1C write DC equipment-related information to the message frames D_1A, D_1B, and D_1C assigned to their respective devices, similar to the case in Figure 5A. In addition, each of inverters 1A, 1B, and 1C writes a message to the first message frame D_1A among the multiple message frames D_1A, D_1B, and D_1C.

[0075] As a specific example, inverter 1A writes a predetermined value related to itself to message frame D_1A as message M11. Inverter 1B reads the predetermined value written to message M11, adds a predetermined value related to itself to that value, writes the result to message frame D_1A as message M12, and writes a predetermined value related to itself to message frame D_1B as message M13. Inverter 1C reads the predetermined value written to message M12, adds a predetermined value related to itself to that value, writes the result to message frame D_1A as message M14, and writes a predetermined value related to itself to message frame D_1C as message M15.

[0076] This allows, for example, DC / DC converter 2A to identify the first message frame D_1A from among the multiple message frames D_1A, D_1B, and D_1C included in the communication message, and to acquire message M14 within the identified message frame D_1A as DC equipment-related information. In other words, the subsequent DC / DC converters 2A and 2B can identify the message frames D_1A, D_1B, and D_1C of all inverters, read out the information at predetermined bit positions, and obtain the integrated value of all inverters from the message frame D_1A of the inverter 1A that passes through first.

[0077] Figures 5A, 5B, and 5C show an example with three inverters. However, if the number of inverters increases further, the processing load may increase if the DC / DC converter 2 collects data from all inverters individually and calculates an integrated value, as shown in Figure 5A. On the other hand, using the method shown in Figure 5B or Figure 5C, the processing of calculating integrated values, such as total power, can be omitted from the DC / DC converter 2, thereby reducing the processing load on the DC / DC converter 2. Consequently, the response speed of the DC / DC converter 2 can be increased.

[0078] <User Interface Details> Figure 6 shows an example of the processing content of the user interface 252 and an example of the display content of the parameter setting unit 28 in Figure 3B. The parameter setting unit 28 is implemented by, for example, an information processing device such as a PC located outside the DC / DC converter 2, or a management computer located inside the DC / DC converter 2. The parameter setting unit 28 is equipped with a display. Furthermore, management software for providing the user with management functions for the DC / DC converter 2 is pre-installed on the parameter setting unit 28.

[0079] As a function of this management software, the parameter setting unit 28 displays a parameter setting screen 200 on the display, as shown in Figure 6. The user interface 252 in the DC / DC converter 2 acquires various parameters entered by the user using the parameter setting screen 200 and stores them in memory. For example, the control command value generation unit 251 can, if necessary, refer to the various parameters stored in the memory and execute processing based on the charge / discharge algorithm.

[0080] In Figure 6, the menu section 210 located at the top of the screen is used to access the initial setup section 220, the communication monitor section 230, and the DC voltage control section 240. The initial setup section 220 consists of, for example, a parameter table 221 that allows input via numerical input or pull-down menus. The user inputs the parameters to be initially registered for the settings of the DC / DC converter 2 into such a parameter table 221.

[0081] As a specific example, the user inputs wiring impedance information between the DC / DC converter 2 and inverters 1A, 1B, and 1C to be configured, i.e., wire type, cross-sectional area, length, impedance, etc., into parameter table 221. In the DC power supply bus 4, if the wiring between inverter 1 and DC / DC converter 2 is long, a deviation occurs between the voltage change at the end of inverter 1 due to load changes in inverter 1 and the voltage change at the end of DC / DC converter 2 due to voltage drops resulting from wiring current and wiring impedance.

[0082] Therefore, for example, when controlling the voltage at the terminals of inverter 1 with the terminal voltage of DC / DC converter 2, it is advisable to apply a correction to the terminal voltage of DC / DC converter 2 that takes into account the voltage drop. Parameter table 221 can be used to determine this correction amount. By pre-registering wiring impedance information in parameter table 221 as initial settings and configuring it so that it can be referenced or reflected in DC voltage control, as described later, the effort of checking and inputting the correction value each time can be reduced.

[0083] The communication monitor unit 230 has the function of visualizing the information contained in the Ethernet communication message that has passed through the DC / DC converter 2. That is, the communication monitor unit 230 visualizes the information acquired by the information acquisition circuit 250. In this example, the communication monitor unit 230 includes a communication frame display unit 231, a communication data display unit 232, a simplified calculation display unit 233, a communication data trend display unit 234, and the like. The communication frame display unit 231 displays the configuration of the message frame to be monitored. The communication data display unit 232 numerically displays the information written to a predetermined address, in other words, a predetermined bit position, such as "0x000F", within each message frame D_1A, D_1B, D_1C.

[0084] In this way, by making the communication data display unit 232 a table format and configuring it so that information written by multiple inverters 1 on the communication path can be compared side by side or vertically, the effect of easily confirming differences between inverters can be obtained. The simplified calculation display unit 233 displays the definition of a simplified calculation formula and the calculation result, which takes the value of a predetermined address as an argument. This simplified calculation formula is defined in advance by the user, and in this example it calculates an integrated value, etc. The communication data trend display unit 234 displays the value written to the specified address "0x000F" in the specified message frame D_1A as a trend over time.

[0085] The DC voltage control unit 240 is a screen used, for example, when a user manually defines the charge / discharge algorithm in the control command value generation unit 251. The DC voltage control unit 240 includes a bus-side correlation display unit 241, a correlation node numerical display unit 242, a charging / discharging algorithm setting unit 243, and the like. For example, consider a case where the user wants the DC / DC converter 2 to operate in a way that adjusts the charge / discharge amount of the DC power supply bus 4 based on the DC bus voltage V2. In this case, the user defines correlation information that defines the relationship between the DC bus voltage V2 and the charge / discharge amount of the DC power supply bus 4, in this example, the DC bus current I2, using the bus-side correlation display unit 241 and the correlation node numerical display unit 242.

[0086] The bus-side correlation display unit 241 displays the correlation information defined by the correlation node numerical display unit 242 in two dimensions. That is, the user uses the correlation node numerical display unit 242 to define the coordinate values ​​of each node P1, P2, ... included in the two-dimensionally displayed correlation information. The control command value generation unit 251 charges and discharges the DC power supply bus 4 based on this correlation information.

[0087] For example, consider a case where the DC bus voltage V2 and DC bus current I2 at node P3 are "V2_P3" and "I2_P3", respectively. In this case, when the control command value generation unit 251 detects "V2_P3" as the DC bus voltage V2 in Figure 3A, it sets the DC bus side current command value I2 so that the DC power supply bus 4 is charged with "I2_P3". * Generates.

[0088] Furthermore, this correlation information can be modified based on DC equipment-related information from inverter 1. For example, to change the coordinate values ​​of node P7 based on DC equipment-related information, the user programs the changes using the discharge algorithm setting unit 243. In this example, the DC bus voltage V2 of node P7 is set to be changed based on the DC equipment-related information written to address "0x000F" in message frames D_1A and D_1B. In this case, the timing of switching between charging and discharging is adjusted.

[0089] In this way, by configuring the correlation information to be changed based on DC equipment-related information, the DC / DC converter 2 can autonomously optimize the charging and discharging of the DC power supply bus 4 according to the state of the inverter 1. Furthermore, when changing the DC bus voltage V2 of node P7 in this manner, the user interface 252 may calculate the value of the changed DC bus voltage V2 by reflecting the wiring impedance information set in the initial setting unit 220. This enables more precise control.

[0090] <Details of the control command value generation unit> Figure 6 illustrates an example in which the control command value generation unit 251 operates based on a charge / discharge algorithm defined by the user. Here, we will explain an example in which the unit operates based on a charge / discharge algorithm defined in advance by a program or the like. Figure 7A is a schematic diagram illustrating an example of operation based on a charge / discharge algorithm assuming an inverter operating pattern in the control command value generation unit 251 shown in Figure 3B. In Figure 7A, for the sake of simplicity, inverter 1C is omitted, and the operating patterns of inverters 1A and 1B are shown.

[0091] Inverters 1A and 1B each receive speed command values ​​from the communication master 6 to operate under speed control, and based on these speed command values, they rotate motors 3A and 3B at speeds ω_1A and ω_1B, respectively. Accordingly, the torque of motors 3A and 3B changes according to the load conditions, as shown by T_1A and T_1B, respectively. At this time, the sum of the power supply from the DC power supply bus 4 to both inverters 1, either the power supply power or the regenerative power in the reverse direction, is partially canceled out, resulting in a change shown in the total load power Psum, which is roughly proportional to the sum of the torques.

[0092] DC equipment-related information such as speed, torque, and power / regenerative power in each inverter 1 is transmitted to the DC / DC converter 2 via a communication message. The communication controller 20, specifically the control command value generation unit 251, within the DC / DC converter 2 generates a control command value based on this DC equipment-related information to either charge the DC power supply bus 4 with power from the battery 5, or charge the battery 5 with regenerative power from the DC power supply bus 4.

[0093] For example, the control command value generation unit 251 may pre-determine thresholds such as a power threshold Phi and a regenerative threshold Plo for the total load power Psum, and charge or discharge the excess power when power or regenerative power exceeds the threshold. In Figure 7A, this excess power is shown as the total charge / discharge power Pdc. The power threshold Phi and the regenerative threshold Plo are predetermined based on, for example, the capacity of the AC / DC converter 41 in Figure 1.

[0094] Furthermore, by defining a threshold Pmax for the total charge / discharge power Pdc, it is possible to operate the system such that, for example, DC / DC converter 2A handles the charge / discharge power P_5A within the threshold Pmax, and DC / DC converter 2B handles the charge / discharge power P_5B exceeding this amount. Methods for implementing such operation include setting the threshold Pmax in the parameter setting unit 28, or sharing it between both DC / DC converters 2A and 2B via communication messages.

[0095] Alternatively, the upstream DC / DC converter 2A may write its own charge / discharge power P_5A to the communication message, thereby allowing the downstream DC / DC converter 2B to understand the remaining charge / discharge power P_5B needed to obtain the total charge / discharge power Pdc. Or, the upstream DC / DC converter 2A may update the DC equipment-related information included in the communication message to reflect its own charge / discharge power P_5A.

[0096] Specifically, each inverter 1 writes the total load power Psum, which is one of the DC equipment-related pieces of information, to the communication message using a method that calculates an integrated value, for example, as shown in Figure 5B or Figure 5C. The upstream DC / DC converter 2A obtains the total load power Psum and updates the total load power Psum, i.e., the DC equipment-related information, by subtracting the charge / discharge power P_5A that it is responsible for from the total load power Psum. In other words, the DC / DC converter 2A updates message M5 in Figure 5B and message M14 in Figure 5C, for example.

[0097] Then, the downstream DC / DC converter 2B charges and discharges the DC power supply bus 4 based on the DC equipment-related information updated by the upstream DC / DC converter 2A, namely the information representing the charge / discharge power P_5B. Using this method, each of the DC / DC converters 2A and 2B can read a message from a predetermined location and use the information written in that message to charge and discharge the DC power supply bus 4. As a result, the processing of the DC / DC converters 2A and 2B can be simplified.

[0098] Furthermore, DC / DC converters 2A and 2B can obtain the state of charge (SOC) of batteries 5A and 5B using the battery communication unit 27 shown in Figure 3A, and write this information to a communication message, thereby confirming whether there is any bias in the SOC between the DC / DC converters 2. In this case, as shown in Figure 7A, for example, by temporarily changing the threshold Pmax of DC / DC converter 2A, the power sharing between the two DC / DC converters 2A and 2B can be changed to charge / discharge powers P_5Ax and P_5Bx. As a result, it becomes possible to adjust the SOC between them.

[0099] When performing such charge rate adjustment, the charge / discharge margin of the downstream DC / DC converter 2B is determined by the power sharing of the upstream DC / DC converter 2A. Therefore, it is preferable to place the DC / DC converter 2 with greater flexibility upstream. In other words, it is preferable to connect the multiple DC / DC converters 2 in series via the Ethernet line 7 in order of increasing power capacity [W] of the converter conversion circuit 21 contained in each DC / DC converter 2. This ensures sufficient margin for charge rate adjustment downstream.

[0100] Furthermore, as shown in Figure 7A, if the upstream DC / DC converter 2A determines its own charge / discharge power based on the threshold Pmax, the upstream DC / DC converter 2A tends to have more charge / discharge switching cycles than the downstream DC / DC converter 2B. On the other hand, due to its internal structure, the storage battery 5 may have a trade-off relationship between its resistance to high-speed charge / discharge switching and its high battery capacity [Ah]. For example, if the electrodes are designed to be thicker, the battery capacity increases, but disadvantages may arise such as a decrease in impedance characteristics due to stagnation of ion diffusion inside the battery, or accelerated degradation due to localized ion depletion.

[0101] Another specific example is the finding that capacitors are suitable for high-frequency charging and discharging because their charge transfer is smoother than that of batteries 5. Therefore, in a system that uses multiple different types of batteries 5, it is preferable that the multiple DC / DC converters 2 be connected in series via an Ethernet line 7 in order of the charge / discharge performance index of the energy storage devices connected to each DC / DC converter 2. In other words, it is preferable that batteries 5 that can withstand high-frequency charging and discharging be placed further upstream. This can, for example, extend the lifespan of the entire energy storage device.

[0102] Figure 7B is a flowchart showing an example of the main processing performed by the communication controller 20 shown in Figure 3B in Figure 7A. In Figure 7B, the information acquisition circuit 250 receives the communication message transmitted via the inverter 1 and acquires DC equipment-related information from the communication message (step S101). Subsequently, the control command value generation unit 251 acquires the total load power Psum from the inverter 1 from the DC equipment-related information (step S102). In this case, the inverter 1 may directly write the total load power Psum, or the control command value generation unit 251 may calculate the total load power Psum based on the speed and torque written by the inverter 1.

[0103] Next, the control command value generation unit 251 determines the charge and discharge power it is responsible for from the total load power Psum, as shown in Figure 7A (step S103). Then, based on the determined charge and discharge power, the control command value generation unit 251 generates the battery-side control command value (V1 * ,I1 * ), or the control command value on the DC power supply bus 4 side (V2 * ,I2 * ) is generated (step S104).

[0104] As a specific example, when charging the DC power supply bus 4, the control command value generation unit 251 generates a control command value (V2) for the DC power supply bus 4 side corresponding to the required power output. * ,I2 *) is generated and the converter circuit 21 is made to perform a boost operation. At this time, the control command value generation unit 251 may correct the control command value based on the parameter table 221 which defines the wiring impedance information shown in Figure 6, for example. On the other hand, when the DC power supply bus 4 is discharged and, consequently, the storage battery 5 is charged, the control command value generation unit 251 generates a control command value on the battery side (V1) corresponding to the regenerative power. * ,I1 * This generates a voltage and causes the converter circuit 21 to perform a step-down operation.

[0105] Here, the DC power supply bus 4 is discharged when, based on DC equipment-related information, power regeneration is detected in at least one of the inverters 1. More specifically, for example, since the power output and regenerated power can cancel each other out in multiple motors 3, the DC power supply bus 4 is discharged when, as shown in the total load power Psum in Figure 7A, power regeneration is detected in the entire network of inverters 1. By detecting power regeneration in this way and charging the battery 5 with the regenerated power, power can be reused, contributing to energy conservation.

[0106] Subsequently, the control command value generation unit 251 updates the DC equipment-related information, in this example the total load power Psum information, to be written to the communication message, reflecting the charge / discharge power determined in step S103 (step S105). As a result, the control command value generation unit 251 in the DC / DC converter 2 located in the next stage can charge and discharge the DC power supply bus 4 based on the updated DC equipment-related information.

[0107] The processing of the control command value generation unit 251 in Figure 7B is realized, for example, by the processor executing a program that defines the charge / discharge algorithm, which is stored in memory. However, the implementation is not limited to this form; for example, the control command value generation circuit that performs this processing may be mounted on an FPGA or ASIC.

[0108] Figure 8A schematically illustrates another example of operation based on a charge / discharge algorithm that assumes an inverter operating pattern in the control command value generation unit 251 shown in Figure 3B. In this example, inverters 1A and 1B are simultaneously stopped at time Tstop for safety reasons of the electric motor system. At this time, the regenerative power due to the deceleration of motors 3A and 3B becomes steep, and as shown by voltage Vdc_b, the voltage of the DC power supply bus 4 may reach an overvoltage Vdc_lim.

[0109] Such overvoltages are usually protected against by dissipating regenerative power as heat through a separate resistor. However, from an energy-saving perspective, it is desirable to store the regenerative power in a state that can be reused as much as possible. Therefore, the DC / DC converter 2 monitors the operating status of inverters 1A and 1B based on DC equipment-related information in the communication message. When both inverters 1A and 1B simultaneously switch from ON to OFF, the DC / DC converter 2 switches to a pre-set faster discharge operation, inducing a rapid decrease in the voltage of the DC power supply bus 4.

[0110] As a result, the occurrence of overvoltage is suppressed, as shown in voltage Vdc_a, and the storage of regenerative power can be promoted. Here, a faster discharge operation means, for example, in the charge / discharge control unit 24 shown in Figure 3A, switching the control command switching unit 25 to control the battery current I1, and the command value I1 * The operation may be such that it sets the voltage command value Vdc to the maximum current applicable to charging the battery 5. * As shown in _a, the DC bus-side voltage command value V2 for the DC power supply bus 4 * It should be an action that rapidly reduces the value.

[0111] Figure 8B is a flowchart showing an example of the main processing performed by the communication controller 20 shown in Figure 3B in Figure 8A. In Figure 8B, the information acquisition circuit 250 receives a communication message transmitted via the inverter 1 and acquires DC equipment-related information from the communication message (step S201). Subsequently, the control command value generation unit 251 acquires the operating status of the inverter 1 from the DC equipment-related information (step S202). For example, if the emergency stop button is pressed by the user or if an emergency stop signal is asserted by an internal protection function, the inverter 1 writes this information to the communication message as DC equipment-related information.

[0112] Based on the acquired operating status, the control command value generation unit 251 detects the simultaneous shutdown of multiple inverters 1 (step S203: Yes) and discharges the DC power supply bus 4 (step S204). More specifically, the control command value generation unit 251 rapidly discharges the DC power supply bus 4 and rapidly charges the storage battery 5. This protects the DC power supply bus 4 from overvoltage while contributing to energy saving through power reuse. The implementation configuration of the control command value generation unit 251 is the same as in Figure 7B.

[0113] Figure 9A schematically illustrates yet another example of operation based on a charge / discharge algorithm that assumes an inverter operating pattern, in the control command value generation unit 251 shown in Figure 3B. For example, in a permanent magnet motor, a back electromotive force is induced in the field circuit during operation, and it is known that the induced voltage increases especially as the rotational speed increases. As the induced voltage rises, the voltage difference with the AC voltage that the inverter 1 can output decreases, so at high rotational speeds, the current that can flow through the field winding decreases, and the torque is limited.

[0114] In such cases, as shown in Figure 9A, the DC bus voltage V2 to the inverter 1 is temporarily increased, thereby raising the AC voltage output by the inverter 1, which ensures a voltage difference and maintains torque. More specifically, the DC / DC converter 2, based on DC equipment-related information from the inverter 1, can increase the DC bus voltage V2 by charging the DC power supply bus 4 when it detects that the rotational speed of some motors 3 has reached a high-speed threshold and that the power torque is in a limited state.

[0115] As a specific control method in this case, for example, in the charge / discharge control unit 24 shown in Figure 3A, the control command switching unit 25 is switched to control the DC bus voltage V2, and the command value V2 * By temporarily increasing the voltage, the DC bus voltage V2 can be raised as shown in Figure 9A. This offers advantages such as avoiding structural modifications to the motor 3, such as increasing the diameter of the wires.

[0116] Figure 9B is a flowchart showing an example of the main processing performed by the communication controller 20 shown in Figure 3B in Figure 9A. In Figure 9B, the information acquisition circuit 250 receives the communication message transmitted via the inverter 1 and acquires DC equipment-related information from the communication message (step S301). Subsequently, the control command value generation unit 251 acquires the rotational speed and torque of the motor 3 from the DC equipment-related information (step S302).

[0117] Then, if the control command value generation unit 251 detects that the acquired motor rotation speed has reached a predetermined high-speed threshold and that the torque is in a limited state (step S303: Yes), it charges the DC power supply bus 4 (step S304). More specifically, the control command value generation unit 251 charges the DC power supply bus 4 in such a way that it increases the DC bus voltage V2. Whether or not the torque is in a limited state can be determined, for example, by whether or not the maximum torque determined based on the motor rotation speed threshold has been reached. The implementation configuration of the control command value generation unit 251 is the same as in the case of Figure 7B.

[0118] <Main effects of the first embodiment> As described above, using the power system according to the first embodiment, the power converter can receive a communication message containing DC equipment-related information via an Ethernet line and charge / discharge the DC power supply bus based on the DC equipment-related information obtained from the communication message. Therefore, typically, when changing the system configuration of the power system, modifications to the power management device, such as those required when using a centralized management system, become unnecessary, and changes to the system configuration can be easily accommodated.

[0119] (Second Embodiment) <Configuration of the power system> Figure 10 is a schematic diagram showing an example of the configuration of a power system according to the second embodiment. The power system shown in Figure 10 is further equipped with a DC / DC converter 2C and a solar power generation panel 43 compared to the power system shown in Figure 1. One end of the DC / DC converter 2C is connected to the solar power generation panel 43 instead of a battery, and the other end is connected to the DC power supply bus 4.

[0120] DC / DC converter 2C is connected in series between inverter group 1 and DC / DC converter 2A in the Ethernet line 7. Unlike DC / DC converters 2A and 2B in Figure 1, DC / DC converter 2C performs only unidirectional power generation operation, not bidirectional charging and discharging. However, since this power generation operation can be considered as charging operation of the DC power supply bus 4, the same operation as in the case of the storage battery 5 described in the first embodiment can be applied to DC / DC converter 2C.

[0121] <Main effects of the second embodiment> As described above, by using the power system according to the second embodiment, the same effects as those described in the first embodiment can be obtained. Furthermore, renewable energy from solar power generation can be effectively utilized to drive the motor 3 and other components, contributing to energy conservation and measures against global warming.

[0122] The present invention has been described in detail above based on embodiments, but the present invention is not limited to the embodiments described above and can be modified in various ways without departing from its essence. For example, the embodiments described above are described in detail in order to explain the present invention in an easy-to-understand manner and are not necessarily limited to those having all the described configurations. Furthermore, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add a configuration from another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with a configuration from another embodiment. [Explanation of Symbols]

[0123] 1: Inverter (DC equipment), 2: DC / DC converter (power converter), 3: Motor, 4: DC power supply bus, 5: Storage battery, 6: Communication master (overall control device), 7: Ethernet line, 20: Communication controller, 21: Converter conversion circuit, 28: Parameter setting unit, 220: Initial setting unit, 240: DC voltage control unit, 241: Bus-side correlation display unit, 243: Discharge / receive algorithm setting unit, 250: Information acquisition circuit, 251: Control command value generation unit, 252: User interface, D_1A, D_1B, D_1C: Message frame

Claims

1. Multiple DC devices, A DC power supply bus that supplies power to each of the aforementioned multiple DC devices, A power converter capable of charging and discharging power to the aforementioned DC power supply bus, A control unit that controls the aforementioned multiple DC devices, An Ethernet line connecting the aforementioned multiple DC devices, the power converter, and the central control unit, Equipped with, The power converter has an information acquisition circuit that receives a communication message containing DC equipment-related information, which is information relating to at least one of the plurality of DC devices, via the Ethernet line, and acquires the DC equipment-related information, and charges and discharges the DC power supply bus based on the acquired DC equipment-related information. The Ethernet line is connected in series such that the communication message passes through the plurality of DC devices in sequence before being transmitted to the power converter. The DC equipment-related information is written to the communication message by at least one of the plurality of DC equipment. Power system.

2. In the power system according to claim 1, Each of the aforementioned DC devices is assigned a unique station number. Each of the aforementioned DC devices identifies multiple message frames from the communication message corresponding to each of the aforementioned station numbers, and if a message frame corresponding to the station number of another device is provided following the message frame corresponding to the station number of the device itself, the device writes a message to the message frame corresponding to the station number of the other device. The information acquisition circuit within the power converter identifies the last message frame among the multiple message frames included in the communication message, and acquires the message within the identified message frame as DC equipment-related information. Power system.

3. In the power system according to claim 1, Each of the aforementioned DC devices is assigned a unique station number. Each of the aforementioned DC devices identifies a plurality of message frames corresponding to a plurality of station numbers from the communication message, and regardless of the station number, writes the message to the first message frame provided among the plurality of message frames. The information acquisition circuit within the power converter identifies the first message frame among the multiple message frames included in the communication message, and acquires the message within the identified message frame as DC equipment-related information. Power system.

4. In the power system according to claim 1, The system comprises multiple power converters, The aforementioned multiple power converters are connected by the aforementioned Ethernet line, One of the aforementioned power converters updates the DC equipment-related information included in the communication message to reflect the charge / discharge power it is responsible for when charging or discharging the DC power supply bus. One of the aforementioned power converters charges and discharges the DC power supply bus based on the updated DC equipment-related information. Power system.

5. In the power system according to claim 1, The system comprises multiple power converters, Each of the aforementioned plurality of power converters is equipped with a power conversion circuit that includes a switching element for charging and discharging, The plurality of power converters are connected in series via the Ethernet line in order of increasing power capacity of the power conversion circuit contained in each power converter. Power system.

6. In the power system according to claim 1, The system comprises multiple power converters, Each of the aforementioned power converters is equipped with a DC / DC converter that charges and discharges power from the DC power supply bus to an energy storage device. The plurality of power converters are connected in series via the Ethernet network in order of the order in which the charge / discharge performance indicator of the energy storage device connected to each power converter is superior. Power system.

7. In the power system according to claim 1, The power converter, based on the DC equipment-related information, discharges the DC power supply bus when it detects that power regeneration has occurred in at least one of the plurality of DC equipment. Power system.

8. In the power system according to claim 1, The power converter, based on the DC equipment-related information, detects that power regeneration has occurred across the multiple DC equipment, and then discharges the DC power supply bus. Power system.

9. In the power system according to claim 1, The power converter, based on the DC equipment-related information, discharges the DC power supply bus when it detects the simultaneous shutdown of the multiple DC devices. Power system.

10. In the power system according to claim 1, At least one of the aforementioned plurality of DC devices is an inverter that drives a motor, The power converter, based on the DC equipment-related information, charges the DC power supply bus when it detects that the motor's rotational speed has reached a threshold and the torque is in a limited state. Power system.

11. Multiple DC devices are electrically connected in parallel via a DC power bus, The system has an information acquisition circuit that receives a communication message transmitted via an Ethernet line and acquires DC device-related information written by at least one of the plurality of DC devices from the communication message. Based on the DC equipment-related information acquired by the information acquisition circuit, the DC power supply bus is charged and discharged. When charging or discharging the DC power supply bus, the DC equipment-related information included in the communication message is updated to reflect the charging and discharging power it provides. Power converter.

12. Multiple DC devices are electrically connected in parallel via a DC power bus, The system has an information acquisition circuit that receives a communication message transmitted via an Ethernet line and acquires DC device-related information written by at least one of the plurality of DC devices from the communication message. Based on the DC equipment-related information acquired by the information acquisition circuit, the DC power supply bus is charged and discharged. The system maintains correlation information that defines the relationship between the voltage of the DC power supply bus and the charge / discharge amount of the DC power supply bus. Based on the correlation information, the DC power supply bus is charged and discharged. Based on the DC equipment-related information, the correlation information is modified. Power converter.

13. In the power converter according to claim 12, It retains user-configurable parameters, The parameters include wiring impedance information between the power converter and each of the plurality of DC devices. The correlation information is further modified based on the aforementioned wiring impedance information. Power converter.

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