Electric system and regeneration control device

Abstract

The present invention appropriately transmits and receives power to and from a DC system in an electric system connected to both the DC system and an AC system. To this end, an electric system (6) is provided with: a motor drive unit (12) that converts a DC voltage in a DC unit (16) to an AC voltage and drives a motor (3); a rectification unit (10) that is connected between an AC system (41) and the DC unit; and a regeneration control device (2) that is connected between a DC system (42) and the DC unit and includes a calculation unit (20). The calculation unit (20) is provided with: a state acquisition unit that acquires a voltage difference between a voltage of the DC system and a voltage of the DC unit and / or a current between the DC system and the DC unit; and a current limiting unit that limits power in a flow direction from the DC unit to the DC system on the basis of information acquired by the state acquisition unit.

Description

Electrical systems and regenerative control devices

[0001] This invention relates to an electric system and a regenerative control device.

[0002] As background technology for this technology, the abstract of Patent Document 1 below states: "[Problem] To provide an uninterruptible power supply that can protect against over-discharge of a storage battery while also providing high reliability of power supply during a power outage. [Solution] The UPS 10 comprises a rectifier 14 that converts AC power to DC power, a battery unit 36 ​​that is charged by the DC power from the rectifier 14, and an inverter unit 18 that converts the DC power from the battery unit 36 ​​to AC power during a power outage. The UPS 10 has an electromagnetic switch 40 in the charging path from the rectifier 14 to the battery unit 36, and a circuit breaker 34 in the discharge path from the battery unit 36 ​​to the inverter unit 18. A battery state detection circuit 46 opens the electromagnetic switch 40 when the cell voltage of a single cell exceeds a charging completion threshold, and outputs a trip signal to the circuit breaker 34 when an abnormality in a single cell is detected, causing the circuit breaker 34 to perform a tripping operation."

[0003] Japanese Patent Publication No. 2013-48497

[0004] Incidentally, in electric systems connected to both DC and AC power systems, there is a desire to more appropriately transfer power to and from the DC power system. This invention has been made in view of the above circumstances, and aims to provide an electric system and a regenerative control device that can appropriately transfer power to and from the DC power system.

[0005] To solve the above problems, the electric system of the present invention comprises a motor drive unit that converts a DC voltage in a DC section into an AC voltage to drive a motor, a rectifier unit connected between the AC system and the DC section, and a regenerative control device connected between the DC system and the DC section and having a calculation unit, wherein the calculation unit comprises a state acquisition unit that acquires the voltage difference between the voltage of the DC system and the voltage of the DC section, and / or the current between the DC system and the DC section, and a current limiting unit that limits the power flowing from the DC section to the DC system based on the information acquired by the state acquisition unit.

[0006] According to the present invention, power can be appropriately transferred to and from a DC system.

[0007] This is a diagram showing the configuration of the electric system according to the first embodiment. This is a detailed configuration diagram of the regenerative control device in the first embodiment. This is a diagram showing various configuration examples of the opening and closing section. This is a block diagram of the computer. This is a flowchart of the operation information calculation routine. This is a detailed configuration diagram of the regenerative control device in the second embodiment. This is a diagram showing the configuration of the electric system according to the third embodiment. This is a perspective view of the main part of the electric system according to the fourth embodiment.

[0008] [Summary of Embodiments] Applying the technology of Patent Document 1, it is considered possible to realize an uninterruptible power supply (UPS) that connects a storage battery to utilize the DC power downstream of the rectifier. On the other hand, in recent years, DC power supply systems that transmit power with low loss have become known as one of the measures to combat global warming. DC power supply systems are particularly preferable when applied to renewable energy from solar power generation or power from DC devices such as storage batteries.

[0009] DC power supply systems have the advantage of lower losses because they can reduce the number of power conversion stages compared to AC power supply systems when transmitting power to motor drive inverters and the like. Furthermore, in electric systems that drive motors, energy savings can be achieved if the regenerative power generated during motor deceleration can be effectively utilized by other equipment through the DC power supply system. For this reason, it is preferable for motor drive inverters that receive power from an AC grid to be equipped with DC terminals so that the internal DC section can be electrically connected to an external source.

[0010] Thus, when an electric system is connected to both AC and DC power sources, it is possible to expect operation such as receiving power from the other in the event of a power outage in one source. However, general inverters, whose input section consists of a diode rectifier, often lack means to limit the current flowing in from the AC terminal. Therefore, if an abnormality such as a voltage drop or short circuit occurs in the DC power system, the current flowing into the AC terminal will increase. As a result, if a switch such as a circuit breaker installed at the AC terminal trips, it becomes impossible to continue operating the electric system. Furthermore, even if the electric system continues to operate, an overload may occur in the diode rectifier section, potentially leading to problems such as overheating.

[0011] If the DC power supply system consists only of a storage battery as shown in Patent Document 1, for example, the power flowing through the diode rectifier and the heat dissipation can be predicted and therefore addressed through design. However, if the DC power supply system is a DC power supply system to which an unspecified number of DC devices are connected, it is difficult to predict the power flowing through the diode rectifier and the heat dissipation. Therefore, when an electric system is mainly connected to a DC power supply system, the power flowing through the diode rectifier and the heat dissipation tend to become problematic.

[0012] Furthermore, applying the technology described in Patent Document 1, for example, a method can be considered to limit the current in one direction using a diode to prevent current from flowing out to the DC power supply system. However, in this technology, regenerative power cannot be shared with the DC power supply system when the motor is decelerated, thus losing the advantage of connecting to the DC power supply system. Therefore, in the embodiment described later, when a voltage drop occurs in the DC power supply system, this is detected and the power supply to the DC power supply system is cut off, thereby preventing overload of the diode rectifier and other components, and quickly switching to AC power supply.

[0013] [First Embodiment] <Configuration of the First Embodiment> Figure 1 is a configuration diagram of the electric system 6 according to the first embodiment. The electric system 6 comprises an inverter 1, a regenerative control device 2, a motor 3, an AC switch 51, and a DC switch 52. The inverter 1 is used to convert power received from a commercial AC power grid 41 (AC system) or a DC power supply system 42 (DC system) into rotation control power for the motor 3. The inverter 1 is also referred to as a general-purpose inverter or a servo amplifier, for example.

[0014] The inverter 1 is connected to the commercial AC power grid 41 via an AC switch 51 and an AC power supply bus 53. The regenerative control device 2 is connected to the DC power supply grid 42 via a DC switch 52 and a DC power supply bus 54. The AC switch 51 and DC switch 52 are provided for safety purposes. The commercial AC power grid 41 has a typical AC voltage and frequency used in the civil and industrial sectors. The frequency is, for example, 50 Hz or 60 Hz, and the AC voltage is, for example, 100 V, 200 V, 400 V, etc. In the example in Figure 1, the commercial AC power grid 41 is, for example, a three-phase AC power grid with a voltage of 200 V.

[0015] The inverter 1 comprises a diode rectifier 10 (rectifier), a DC capacitor 11, a motor drive unit 12, a regenerative power consumption unit 13, a control unit 14, and an external signal terminal 15. The DC capacitor 11 and the regenerative power consumption unit 13 are collectively referred to as the DC unit 16. The DC unit 16 is connected to the regenerative control device 2 via a DC line 17. That is, the regenerative control device 2 is connected between the DC power supply system 42 and the DC unit 16. The diode rectifier 10 converts the AC power received voltage from the commercial AC power system 41 into a DC voltage. The DC capacitor 11 stabilizes the DC voltage.

[0016] The control unit 14 supplies a pulse command Sr to the motor drive unit 12. The motor drive unit 12 is equipped with a plurality of power semiconductor elements (unsigned) and controls these power semiconductor elements on / off based on the pulse command Sr. As a result, the motor drive unit 12 converts the DC voltage output from the DC capacitor 11 into an AC voltage for driving the motor 3.

[0017] The regenerative power consumption unit 13 consumes power through an internal resistor (unsigned) to reduce the peak in the DC voltage when the power regenerated during deceleration of the motor 3 is excessive. However, the regenerative power consumption unit 13 is not necessarily an essential component and may be omitted. The external signal terminal 15 is connected to the regenerative control device 2 and inputs and outputs various information. In particular, the control unit 14 outputs motor drive information Sm to the regenerative control device 2 via the external signal terminal 15. The motor drive information Sm includes various information about the motor 3, such as the rotational speed ω of the motor 3.

[0018] The DC power supply system 42 is generally connected to energy sources such as solar power generation and storage batteries, and is a power supply line using DC voltage that enables low-loss power transmission. A DC power supply bus 54, a DC switch 52, and a regenerative control device 2 are connected in series between the DC power supply system 42 and the inverter 1. The output terminal of the regenerative control device 2 is connected in parallel to the DC capacitor 11 inside the inverter 1.

[0019] Figure 2 is a detailed configuration diagram of the regenerative control device 2 in the first embodiment. In Figure 2, the regenerative control device 2 includes a calculation unit 20, a switching unit 21, a power supply side voltage detection unit 23, a load side voltage detection unit 24, a current detection unit 25, a power supply unit 26, an external power supply terminal 27, a power supply selection circuit 28, an external signal terminal 29, an input terminal 31, an output terminal 32, and capacitors 33 and 34.

[0020] The input terminal 31 is connected to the DC power supply system 42 via a DC switch 52 (see Figure 1). The output terminal 32 is connected to the DC section 16 of the inverter 1. A capacitor 33, a switching unit 21, a capacitor 34, and a current detection unit 25 are connected in series between the input terminal 31 and the output terminal 32.

[0021] The current detection unit 25 detects the current Id flowing from the output terminal 32. The current Id is considered positive in the power direction from the input terminal 31 to the output terminal 32, and negative in the reverse direction. However, the current detection unit 25 is not limited to the location shown in the figure, and may be connected to any location from the input terminal 31 to the output terminal 32. The power supply side voltage detection unit 23 detects the voltage VdS (DC system voltage), which is the terminal voltage of the capacitor 33, and the load side voltage detection unit 24 detects the voltage VdL (DC section voltage), which is the terminal voltage of the capacitor 34.

[0022] The calculation unit 20 includes a state acquisition unit 222 and a current limiting unit 224. The state acquisition unit 222 acquires various information from the inverter 1 and the regenerative control device 2. The current limiting unit 224 outputs operation information S1 to the switching unit 21 based on the information acquired by the state acquisition unit 222, namely the motor drive information Sm, voltage VdS, VdL, and current Id.

[0023] Here, the power in the direction from the output terminal 32 to the input terminal 31 is called the "predetermined direction power." Operation information S1 is information that specifies either the closed state of the switching unit 21, which is "ON," or the open state, which is "OFF." In other words, when the switching unit 21 is "ON," it allows the supply of the predetermined direction power, and when it is "OFF," it cuts off the supply of the predetermined direction power.

[0024] The calculation unit 20 inputs and outputs various information to and from the inverter 1 via the external signal terminal 29 and the external signal terminal 15 of the inverter 1 (see Figure 1). However, instead of providing the external signal terminals 15 and 29, the calculation unit 20 and the inverter 1 may communicate wirelessly. The motor drive information Sm that the inverter 1 supplies to the calculation unit 20 includes "measurement information," "command value information," and "operation information" related to the regenerative power consumption unit 13.

[0025] Here, "measurement information" includes the rotational speed ω of motor 3, the motor torque of motor 3, and the power consumption / regenerative power of motor 3. However, if motor 3 is a linear motor, the measurement information includes the motor speed instead of the rotational speed ω. Also, "command value information" includes the command values ​​for the rotational speed ω (or motor speed), motor torque, and power consumption / regenerative power.

[0026] The "operation information" related to the regenerative consumption unit 13 includes the electric power to be consumed by the regenerative consumption unit 13. However, the motor drive information Sm does not necessarily need to include all of the information described above, and only needs to include information necessary for the regenerative control device 2. For example, the motor drive information Sm may include only the rotational speed ω.

[0027] The power supply for the calculation unit 20 can be obtained from inside or outside the regenerative control device 2. That is, inside the regenerative control device 2, the power supply unit 26 converts the voltage at the output terminal 32 into a predetermined control voltage and supplies it to the power selection circuit 28. Further, the external power supply terminal 27 receives a control voltage from an external power supply device (not shown) and supplies it to the power selection circuit 28. The power selection circuit 28 includes a pair of diodes (not numbered), and causes current to be supplied to the calculation unit 20 from the side with the higher control voltage between the power supply unit 26 and the external power supply device. This can prevent interference between the power supply unit 26 and the external power supply device. Note that the power supply to the calculation unit 20 may be provided by only one of the power supply unit 26 or the external power supply device, and in that case, the power selection circuit 28 may be omitted.

[0028] In the example of Fig. 2, the voltage of the output terminal 32 is supplied to the power supply unit 26. This allows the calculation function of the calculation unit 20 to be maintained even when an abnormality occurs in the DC power supply system 42. Generally, since switches such as the DC switch 52 are installed on distribution boards on indoor wall surfaces, the regenerative control device 2 can be formed separately from the inverter 1 and disposed, for example, near the DC switch 52. Furthermore, by configuring the regenerative control device 2 as a separate body from the inverter 1, it is possible to additionally provide the power supply monitoring function of the regenerative control device 2 without modifying the existing inverter 1.

[0029] Note that when the regenerative control device 2 is integrated with the inverter 1, there is an advantage that intermediate wiring can be omitted. If the external signal terminal 29 and the external power supply terminal 27 are made conductive with the inverter 1 via a board-to-board connector, for example, to enable arrangement according to the application, it is possible to reduce noise and the like related to the transmission and reception of communication information.

[0030] FIG. 3 is a diagram showing various configuration examples of the opening / closing unit 21. That is, all of the opening / closing units 21A, 21B, 21C, 21D, and 21E shown in FIG. 3 can be employed as the opening / closing unit 21. The opening / closing unit 21A includes a DC power supply unit 60, a switch 62, an electromagnetic relay 64, a positive-side power line 61P, and a negative-side power line 61N. The contact (not denoted by a reference numeral) of the electromagnetic relay 64 is inserted into the positive-side power line 61P. The on / off state of the switch 62 is switched according to operation information S1. When the switch 62 is turned on, current is supplied from the DC power supply unit 60 to the coil (not denoted by a reference numeral) of the electromagnetic relay 64. Accordingly, the electromagnetic relay 64 switches the open / closed state of the power line 61P based on the operation information S1.

[0031] The opening / closing unit 21B includes an electromagnetic relay 66 instead of the electromagnetic relay 64 of the opening / closing unit 21B. The electromagnetic relay 66 is provided with two contacts (not denoted by reference numerals), which are inserted into the power lines 61P and 61N, respectively. Accordingly, the electromagnetic relay 66 switches the open / closed state of the power lines 61P and 61N based on the operation information S1.

[0032] In addition to the same configuration as the opening / closing unit 21A, the opening / closing unit 21C includes a diode 65. The diode 65 is connected to the contact (not denoted by a reference numeral) of the electromagnetic relay 64 with its anode on the DC power supply system 42 (see FIG. 1) side and its cathode on the regeneration control device 2 (see FIG. 1) side. Accordingly, power supply from the DC power supply system 42 to the regeneration control device 2 is executed regardless of the value of the operation information S1.

[0033] The opening / closing unit 21D includes a DC power supply unit 60, a switch 62, and a switching element 70. In the illustrated example, the switching element 70 is an FET (Field-Effect Transistor), but the switching element 70 is not limited thereto, and may be an IGBT (Insulated Gate Bipolar Transistor) or the like. A current input / output terminal (not denoted by a reference numeral) of the switching element 70 is inserted into the positive-side power line 61P.

[0034] When switch 62 is turned ON, current is supplied from the DC power supply unit 60 to the control input terminal (not indicated) of the switching element 70. As a result, the switching element 70 switches the open / closed state of the power line 61P based on the operation information S1. As shown in the figure, when an FET is used as the switching element 70, it is preferable that the orientation of its parasitic diode be the same as the orientation of the diode 65 in the switching unit 21C described above. As a result, similar to the switching unit 21C, power supply from the DC power supply system 42 (see Figure 1) to the regenerative control device 2 is performed regardless of the value of the operation information S1.

[0035] The switching unit 21E comprises a DC power supply unit 60, a switch 62, and switching elements 72 and 74. In other words, the switching unit 21E has the same configuration as the switching unit 21D, but with the switching element 70 replaced by switching elements 72 and 74. The current input / output terminals (unsigned) of the switching elements 72 and 74 are connected in series with their respective output polarities facing each other and are inserted into the positive power line 61P.

[0036] As a result, the switching element 70 switches the open / closed state of the power line 61P based on the operation information S1. When it is in the open state, it can interrupt both the current flowing to the right and to the left in the diagram. Although the switching units 21A, 21C, 21D, and 21E described above open and close the positive power line 61P, they may also open and close the negative power line 61N, or they may open and close both power lines 61P and 61N.

[0037] Figure 4 is a block diagram of the computer 980. The control unit 14 and arithmetic unit 20 shown in Figures 1 and 2 each include one or more computers 980 as shown in Figure 4. In Figure 4, the computer 980 includes a CPU (Central Processing Unit) 981, a storage unit 982, a communication port 983, an input / output port 984, and a DSP (Digital Signal Processor) 985.

[0038] Here, the memory unit 982 includes RAM 982a and ROM 982b. The communication port 983 is connected to the communication circuit 986. The input / output port 984 is connected to the input / output device 987. ROM 982b stores control programs and various data executed by the CPU 981 and DSP 985. The CPU 981 and DSP 985 realize various functions by executing these control programs. In Figure 2, the inside of the arithmetic unit 20 shows the functions realized by these control programs.

[0039] <Operation of the First Embodiment> Next, the operation of this embodiment will be described. Figure 5 is a flowchart of the operation information calculation routine. This routine is executed at predetermined intervals in the calculation unit 20. When the process in Figure 5 proceeds to step S10 (first function), the current limiting unit 224 determines whether the current value of the operation information S1 is "ON". If it is determined to be "True", the process proceeds to step S12.

[0040] In step S12, the current limiting unit 224 determines whether the current Id is positive or not. If it is determined to be "True", the processing of this routine ends. In this case, power is being supplied from the DC power supply system 42 to the inverter 1 (see Figure 1). Then, since the processing of this routine ends with the operation information S1 remaining "ON", this power supply will continue.

[0041] On the other hand, if the result in step S12 is "False", the process proceeds to step S14 (second function). Here, it is determined whether the speed change amount Δω is a negative value. The speed change amount Δω is the result of subtracting the previously obtained value from the currently obtained value when the rotational speed ω of the motor 3 is obtained at predetermined sampling time intervals. Therefore, if the speed change amount Δω is a negative value, it indicates that the motor 3 is decelerating. If the result in step S14 is "True", the processing of this routine ends.

[0042] If step S12 is determined to be "False," it means that the current Id is zero or negative. If step S14 is determined to be "True," it means that the motor 3 is decelerating. If both of these conditions are met, there is a high probability that the motor 3 is in regenerative operation. If the motor 3 is in regenerative operation, the regenerative control device 2 can supply regenerative power to the DC power supply system 42. Therefore, if the processing of this routine is completed with operation information S1 remaining "ON," the supply of regenerative power to the DC power supply system 42 will continue.

[0043] On the other hand, if "False" is determined in step S14, the process proceeds to step S16, and operation information S1 is set to "OFF". If "False" is determined in step S14, it is highly likely that the motor 3 is in power operation. Nevertheless, if power is being supplied from the DC power supply system 42 to the inverter 1 (see Figure 1), it is highly likely that some abnormality has occurred in the DC power supply system 42 and the voltage in the DC power supply system 42 has dropped. Therefore, in this embodiment, in such cases, operation information S1 is set to "OFF" to stop the power supply to the DC power supply system 42.

[0044] Furthermore, if the operation information S1 is "OFF" when this routine is started, it is determined to be "False" in step S10, and the process proceeds to step S18 (third function). Here, the current limiting unit 224 determines whether the following equation (1) is true: β > VdS - VdL > α ...Equation (1)

[0045] In equation (1), both the lower limit α and the upper limit β are positive values. If equation (1) does not hold, step S18 is determined to be "False", and the processing of this routine ends with the operation information S1 remaining "OFF". On the other hand, if equation (1) holds, step S18 is determined to be "True", and the process proceeds to step S20 (third function).

[0046] The current limiting unit 224 measures the elapsed time T from the moment the determination result in step S18 last changed from "False" to "True". In step S20, the current limiting unit 224 determines whether this elapsed time T has become greater than or equal to a predetermined delay time Td. If it is determined to be "False" here, the processing of this routine ends with the operation information S1 remaining "OFF".

[0047] On the other hand, if "True" is determined in step S20, the process proceeds to step S22, where the current limiting unit 224 sets the operation information S1 to "ON", and the processing of this routine ends. According to the processing in steps S18 to S22, the current limiting unit 224 sets the operation information S1 to "ON" on the condition that the voltage VdS (see Figure 2) on the DC power supply system 42 side is higher than the voltage VdL on the inverter 1 side. This allows power to be supplied from the DC power supply system 42 to the inverter 1.

[0048] However, in this embodiment, in order to suppress the occurrence of chattering and the like, a determination is made in step S20, and if the elapsed time T becomes greater than or equal to the delay time Td, the operation information S1 is set to "ON". Also, when the switching unit 21C (see Figure 3) is applied as the switching unit 21, a forward voltage drop occurs across the diode 65 even if the operation information S1 is "OFF". As a result, the voltages VdS and VdL will not perfectly match.

[0049] Therefore, by setting the lower limit value α to a voltage equivalent to the forward voltage drop of diode 65, it becomes possible to appropriately determine whether or not to turn the operation information S1 "ON". For this reason, it is preferable to apply a value of about 0.5 to 1.5V, which is equivalent to the forward voltage drop of a typical diode, as the lower limit value α. Also, if a configuration in which multiple diodes are connected in series is adopted instead of diode 65, it is preferable to apply a value obtained by multiplying the forward voltage drop by the number of diodes in series as the lower limit value α.

[0050] Furthermore, if the operation information S1 is turned "ON" when the voltage VdS is too high compared to the voltage VdL, an inrush current will be generated from the DC power supply system 42 toward the DC capacitor 11 in order to charge the DC capacitor 11. Because this inrush current may cause wear on devices along the current path, equation (1) is conditional on "VdS - VdL" being less than the upper limit value β.

[0051] Furthermore, if it is not necessary to consider the forward voltage drop of the diode, chattering, inrush current, etc., as described above, the corresponding processing in steps S18 and S20 can be simplified. For example, in step S18, the current limiting unit 224 may determine whether "VdS > VdL" is true, and if it is true, the operation information S1 may be immediately turned "ON" in step S22, or the routine may be terminated if it is not true.

[0052] According to the operation described above, the connection is interrupted when current flows out of the DC power supply system 42, and the connection is automatically restored under normal conditions. As a comparative example, we will consider the operation in which the switching unit 21 is turned "OFF" based solely on the determination of the current Id (when step S12 is "False"). According to this comparative example, the switching unit 21 may also be turned "OFF" if the change in current Id is not due to an abnormality in the DC power supply system 42, but rather when the regenerative power increases due to the deceleration of the motor 3.

[0053] As mentioned above, a feature of DC power supply is that the regenerative power of the motor 3 can be supplied to the DC power supply system 42. In this case, it is preferable to keep the switching unit 21 "ON" as much as possible. According to this embodiment, measurement information or command value information related to the rotational speed ω is supplied from the inverter 1 as motor drive information Sm. This makes it possible to determine, for example, that a change in current Id has occurred due to the deceleration of the motor 3 if the speed change amount Δω is decreasing. As a result, if the speed change amount Δω is a negative value, the switching unit 21 can be kept "ON".

[0054] [Second Embodiment] Next, an electric system according to the second embodiment will be described. In the electric system according to the second embodiment, the regenerative control device 2A shown in Figure 6 is used instead of the regenerative control device 2 (see Figure 2) in the first embodiment. The other configurations of the second embodiment are the same as those of the first embodiment. In the description of each embodiment, the same reference numerals are used for parts corresponding to parts of the other embodiments described above, and their descriptions may be omitted.

[0055] Figure 6 is a detailed configuration diagram of the regenerative control device 2A in the second embodiment. In Figure 6, the regenerative control device 2A does not have the power supply side voltage detection unit 23, load side voltage detection unit 24, current detection unit 25, and capacitors 33 and 34 as in the first embodiment (see Figure 2), and is instead equipped with a differential voltage detection unit 22.

[0056] The differential voltage detection unit 22 detects the potential difference between the input and output sides of the regenerative control device 2A, for example, the differential voltage "VdS - VdL" between the terminals of the switching unit 21, and outputs the result as a potential difference signal S2. The current limiting unit 224 of the calculation unit 20 sets the operation information S1 based on the potential difference signal S2, instead of the detection results of voltages VdS and VdL in the first embodiment.

[0057] As shown in Figure 3, the switching unit 21 is equipped with electromagnetic relays 64, 66, a diode 65, or switching elements 70, 72, 74. These elements have low resistance when ON and high resistance when OFF. If the ON resistance of these elements is Ron, then when the operation information S1 is "ON", the following equation (2) holds: S2 = Ron × Id ≈ VdS - VdL ...Equation (2)

[0058] Here, if the on-resistance Ron is known, the current Id or the value of "VdS - VdL" can be estimated based on the potential difference signal S2 and equation (2). As a result, estimated information based on the potential difference signal S2 can be applied instead of the voltage VdS, VdL and current Id that were supplied to the calculation unit 20 in the first embodiment, and cost reduction can be expected through simplification and reduction of various detection units.

[0059] [Third Embodiment] Next, an electric system according to the third embodiment will be described. Figure 7 is a configuration diagram of the electric system 6B according to the third embodiment. The electric system 6B includes a regenerative control device 2, motors 3A, 3B, 3C, energy storage devices 7A, 7B, DC / DC converters 8A, 8B, a controller 9, a diode rectifier 10, a DC capacitor 11, motor drive units 12A, 12B, 12C, a communication network 18, an AC switch 51, and a DC switch 52.

[0060] The motor drive units 12A, 12B, and 12C are each configured in the same way as the motor drive unit 12 in the first embodiment. As a result, the motor drive units 12A, 12B, and 12C independently drive the motors 3A, 3B, and 3C. The DC / DC converters 8A and 8B mutually convert the output voltage of the energy storage devices 7A and 7B with the terminal voltage of the DC capacitor 11. As a result, the energy storage devices 7A and 7B are charged and discharged via the DC / DC converters 8A and 8B.

[0061] The controller 9 is connected to the regenerative control device 2, DC / DC converters 8A and 8B, and motor drive units 12A, 12B, and 12C via a communication network 18. This allows the controller 9 to centrally manage the DC / DC converters 8A and 8B and the motor drive units 12A, 12B, and 12C. The communication network 18 should preferably employ a loop-shaped communication topology, such as the Ethernet (registered trademark) standard. This allows the regenerative control device 2 to monitor the return information from each device with low latency, resulting in faster and safer setting of operation information S1.

[0062] The electric system 6B supplies power to multiple motor drive units 12A, 12B, and 12C from a small number of diode rectifier units 10 (one in the illustrated example). Such a system is also called a common converter. In the electric system 6B, multiple motors 3A, 3B, and 3C that generate regenerative power are provided, so the rotational speed to be managed by the regenerative control device 2 is also managed for each of the motors 3A, 3B, and 3C. For this reason, the controller 9 manages the rotational speed ω of each of the motors 3A, 3B, and 3C. A ,ω B ,ωC Information such as the above is supplied to the regeneration control device 2.

[0063] For example, the rotational energy of a motor is proportional to the square of the rotational speed ω and the inertia. Let the inertia of motors 3A, 3B, 3C be J A , J B , J C , then the total energy E, which is the sum of the rotational energy of each motor, M is represented by the following formula (3). E M = J A × ω A 2 + J B × ω B 2 + J C × ω C 2 ...Formula (3)

[0064] The controller 9 replaces supplying the rotational speeds ω A , ω B , ω C to the regeneration control device 2, and may instead supply the change amount ΔE of the total energy E M to the regeneration control device 2. Here, the change amount ΔE M refers to the result obtained by subtracting the previously acquired value from the currently acquired value when the total energy E M is acquired at every predetermined sampling time. M is acquired at every predetermined sampling time, it is the result of subtracting the previously acquired value from the currently acquired value.

[0065] Further, in FIG. 7, power storage devices 7A, 7B are connected to a DC capacitor 11 via DC / DC converters 8A, 8B that are connected in parallel. The sum of the charge-discharge power of DC / DC converters 8A, 8B (with the charging direction taken as a positive value) is referred to as charge-discharge power E DCDC Further, when the charge-discharge power E DCDC is acquired at every predetermined sampling time, the result obtained by subtracting the previously acquired value from the currently acquired value is referred to as charge-discharge power change amount ΔE DCDC Further, the change amount ΔE of the total energy E M in motor drive units 12A, 12B, 12C M and the charge-discharge power change ΔE DCDC The sum of these values is referred to as total change amount ΔE (state information).

[0066] In the electric system 6B, for example, the regenerative power of motors 3A, 3B, and 3C may be absorbed by energy storage devices 7A and 7B located inside the electric system 6B. In such cases, the change in current Id (see Figure 2) corresponds to the rotational speed ω A ,ω B ,ω C This may no longer be the case. In this case, the controller 9 should supply the total change amount ΔE mentioned above to the regenerative control device 2.

[0067] In step S14 of the first embodiment described above (see Figure 5), it was determined whether or not "Δω < 0" holds true. In this embodiment, instead, it is preferable to determine whether or not "ΔE < 0" holds true. In other words, the current limiting unit 224 of the regenerative control device 2 (see Figure 2) determines whether or not regenerative power is being generated in the electric system 6B as a whole. Then, if the determination result is positive, the calculation unit 20 controls the switching unit 21 to supply regenerative power to the DC power supply system 42.

[0068] [Fourth Embodiment] Next, an electric system according to the fourth embodiment will be described. Figure 8 is a perspective view of the main part of the electric system 6C according to the fourth embodiment. In Figure 8, the electric system 6C comprises an inverter 1 and a regenerative control device 2. The electrical configuration of the electric system 6C is the same as that of the electric system 6 in the first embodiment (see Figure 1). Each element of the inverter 1 is housed in a housing 150 (first housing), and each element of the regenerative control device 2 is housed in a housing 250 (second housing). The electric system 6C further comprises a motor 3 shown in Figure 1, an AC switch 51, and a DC switch 52, but these are not shown in Figure 8.

[0069] In Figure 8, the casing 150 of the inverter 1 is formed in a substantially rectangular parallelepiped shape, and a connection portion 101 (first terminal) is provided on its upper surface. A substantially rectangular recess 105 is also formed on the upper surface of the casing 150, and a connector 102 (first connector) is provided on the bottom surface of the recess 105. The casing 250 of the regenerative control device 2 is formed in a substantially rectangular plate shape that fits into the recess 105. This allows the casing 250 to be integrally formed with the casing 150. A connection portion 201 (second terminal) is provided on the upper surface of the casing 250 at a position opposite to the connection portion 101. A connector 202 (second connector) that fits with the connector 102 is also provided on the lower surface of the casing 250.

[0070] When the housing 250 of the regenerative control device 2 is fitted into the recess 105, the connectors 102 and 202 are fitted. The connectors 102 and 202 include external signal terminals 15 and 29 (see Figures 1 and 2). Therefore, when the two are fitted together, when connector 102 transmits motor drive information Sm, connector 202 receives this motor drive information Sm. In addition, screw fastening holes 203 are formed in the housing 250 of the regenerative control device 2, and when screws (not indicated) are inserted through these holes and tightened, the inverter 1 and the regenerative control device 2 can be integrated.

[0071] Furthermore, each of the connecting parts 101 and 201 has a pair of positive and negative screw holes (not indicated) formed on its upper surface. Also, each of the two rectangular copper bars 204 (connecting members) has a pair of through holes (not indicated). When connecting the connecting parts 101 and 201, the pair of copper bars 204 are placed on the upper surfaces of the connecting parts 101 and 201 so as to be approximately parallel. Then, screws (not indicated) are inserted through the through holes in the copper bars 204 and tightened into the screw holes of the connecting parts 101 and 201, thereby connecting the connecting parts 101 and 201 by the copper bars 204. In this state, the pair of positive and negative copper bars 204 are approximately parallel.

[0072] These connecting parts 101, 201 and copper bars 204 constitute the DC transmission line 17 shown in Figure 1. By arranging the connecting parts 101, 201 so that they can be connected by a pair of roughly rectangular copper bars 204, the shape of the copper bars 204 and other components can be simplified, contributing to cost reduction. In the example shown in Figure 8, the inverter 1 and the regenerative control device 2 are fixed by screws inserted through screw fastening holes 203, but they may also be fixed by a structure such as claws (not shown).

[0073] [Variations] The present invention is not limited to the embodiments described above, and various modifications are possible. The embodiments described above are illustrative examples provided to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. Furthermore, it is possible to delete parts of the configuration of each embodiment, add other configurations, or replace them with other configurations. In addition, the control lines and information lines shown in the figures are those that are considered necessary for explanation, and do not necessarily represent all control lines and information lines required in the product. In practice, it can be assumed that almost all configurations are interconnected. Possible modifications to the above embodiments are as follows, for example.

[0074] (1) Since the hardware of the regenerative control devices 2 and 2A in each of the above embodiments can be implemented by a general-purpose computer, the programs that execute the processes corresponding to each of the block diagrams and flowcharts described above, and other various processes described above, may be stored in a storage medium (a computer-readable recording medium on which the program is recorded) or distributed via a transmission line.

[0075] (2) Although the processes corresponding to each block diagram and flowchart described above, and other various processes described above, were explained as software processes using a program in the above embodiment, some or all of them may be replaced with hardware processes using an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array), etc.

[0076] [Effects of the Embodiments] As described above, according to each embodiment, the calculation unit 20 includes a state acquisition unit 222 that acquires the voltage difference between the voltage of the DC system (42) and the voltage of the DC unit 16, and / or the current between the DC system (42) and the DC unit 16, and a current limiting unit 224 that limits the power flowing from the DC unit 16 to the DC system (42) based on the information acquired by the state acquisition unit 222. This allows for appropriate power transfer to and from the DC system. That is, the power flowing from the DC unit 16 to the DC system (42) can be limited based on the voltage difference between the voltage of the DC system (42) and the voltage of the DC unit 16, and / or the current between the DC system (42) and the DC unit 16.

[0077] Furthermore, it is even more preferable that the current limiting unit 224 includes a first function (S10) for determining whether or not it is limiting the power flowing from the DC unit 16 to the DC system (42), a second function (S14) for determining whether to limit the power when current is flowing from the DC unit 16 to the DC system (42), and a third function (S18, S20) for determining whether or not to release the power limit while the power is being limited. This allows for more appropriate power transfer to and from the DC system based on whether or not it is limiting the power flowing from the DC unit 16 to the DC system (42).

[0078] Furthermore, it is even more preferable that the state acquisition unit 222 has a function to acquire motor drive information Sm representing the operating state of the motor 3 or motor drive unit 12, and that the second function (S14) is a function to determine whether or not to limit the power based on the motor drive information Sm. This makes it possible to determine more appropriately whether or not to limit the power based on the motor drive information Sm.

[0079] Furthermore, the electric system 6 further includes a regenerative power consumption unit 13 that consumes regenerative power from the motor 3, and it is even more preferable that the motor drive information Sm includes any of the following: measured or commanded values ​​relating to the speed of the motor 3, the torque of the motor 3, or the power of the motor 3, or the state of the regenerative power consumption unit 13. This makes it possible to more appropriately determine whether or not to limit the power based on various information.

[0080] Furthermore, as in the third embodiment, if multiple motor drive units 12A, 12B, and 12C are provided to drive multiple motors 3A, 3B, and 3C, it is even more preferable to further provide a controller 9 that manages the multiple motor drive units 12A, 12B, and 12C, and the controller 9 notifies the regenerative control device 2 of state information (ΔE) indicating whether the multiple motors 3A, 3B, and 3C as a whole are in a regenerative state or a powered state. This makes it possible to more appropriately determine whether or not to limit the power based on the state information (ΔE).

[0081] Furthermore, as in the third embodiment, if the electric system 6 includes energy storage devices 7A, 7B and DC / DC converters 8A, 8B, it is even more preferable for the controller 9 to notify the regenerative control device 2 of state information (ΔE) indicating whether the multiple motors 3A, 3B, 3C and the energy storage devices 7A, 7B as a whole are in a regenerative state or a powered state. This makes it possible to more appropriately determine whether or not to limit the power based on the state information (ΔE) that takes into account the state of the energy storage devices 7A, 7B, etc.

[0082] Furthermore, it is even more preferable that the third function (S18, S20) is a function that releases the power limit, provided that the differential voltage VdS-VdL, which is the result of subtracting the DC section voltage (VdL), which is the voltage of the DC section 16, from the DC system voltage (VdS), which is the voltage of the DC system (42), is lower than a predetermined upper limit β and higher than a predetermined lower limit α. This makes it possible to more appropriately determine whether or not to limit the power based on the DC system voltage (VdS) and the DC section voltage (VdL).

[0083] Furthermore, the regenerative control device 2 comprises a calculation unit 20 and a power supply unit 26, with the state acquisition unit 222 and the current limiting unit 224 being included in the calculation unit 20. It is even more preferable that the power supply unit 26 generates the voltage supplied to the calculation unit 20 from the voltage of the DC unit 16. This simplifies the configuration of the power supply unit 26 and allows the calculation function of the calculation unit 20 to be maintained even if an abnormality occurs in the DC power supply system 42.

[0084] Furthermore, the motor drive unit 12 is housed in a first housing (150) which has a first connector (102) that outputs motor drive information Sm representing the operating state of the motor 3 or the motor drive unit 12, and a pair of positive and negative first terminals (101) that transmit DC current. The regenerative control device 2 is more preferably further comprising a second housing (250) which is shaped to be integrally formed with the first housing (150) by physical fitting, a second connector (202) provided in the second housing (250) which receives motor drive information Sm by fitting with the first connector (102) when the second housing (250) is fitted into the first housing (150), a pair of positive and negative second terminals (201) that transmit DC current, and a pair of positive and negative connecting members (204) that connect the first terminals (101) and the second terminals (201) and are substantially parallel when connected. This allows the inverter 1 and the regenerative control device 2 to be integrated, and simplifies the wiring between them.

[0085] 2 Regenerative control device 3, 3A, 3B, 3C Motor 6, 6B Electric system 7A, 7B Energy storage device 8A, 8B DC / DC converter 9 Controller 10 Diode rectifier section (rectifier section) 12, 12A, 12B, 12C Motor drive section 13 Regenerative consumption section 16 DC section 20 Calculation section 26 Power supply section 41 Commercial AC system (AC system) 42 DC power supply system (DC system) 101 Connection section (first terminal) 102 Connector (first connector) 150 Housing (first housing) 201 Connection section (second terminal) 202 Connector (second connector) 204 Copper bar (connecting member) 222 State acquisition section 224 Current limiting section 250 Housing (second housing) α Lower limit β Upper limit Sm Motor drive information ΔE Total change amount (state information) S10 Step (first function) S14 Step (second function) S18, S20 Step (third function) VdL Voltage (DC section voltage) VdS Voltage (DC system voltage) VdS - VdL Difference voltage

Claims

1. An electric motor system comprising: a motor drive unit that converts a DC voltage in a DC section into an AC voltage to drive a motor; a rectifier unit connected between an AC system and the DC section; and a regenerative control device connected between a DC system and the DC section and having a calculation unit, wherein the calculation unit comprises: a state acquisition unit that acquires the voltage difference between the voltage of the DC system and the voltage of the DC section, and / or the current between the DC system and the DC section; and a current limiting unit that limits the power flowing from the DC section to the DC system based on the information acquired by the state acquisition unit.

2. The electric system according to claim 1, characterized in that the current limiting unit comprises: a first function for determining whether or not it is limiting the power in a predetermined direction, which is power flowing from the DC unit to the DC system; a second function for determining whether or not to limit the power in the predetermined direction when current is flowing from the DC unit to the DC system; and a third function for determining whether or not to release the limit on the power in the predetermined direction while it is being limited.

3. The electric system according to claim 2, characterized in that the state acquisition unit has a function to acquire motor drive information representing the operating state of the motor or the motor drive unit, and the second function is a function to determine whether or not to limit the power in a predetermined direction based on the motor drive information.

4. The electric system according to claim 3, further comprising a regenerative power consumption unit that consumes regenerative power from the motor, wherein the motor drive information includes any of the following: a measured value or command value relating to the speed of the motor, the torque of the motor, or the power of the motor, or the state of the regenerative power consumption unit.

5. The motor drive unit is provided in multiple quantities for driving multiple motors, and further comprises a controller for managing the multiple motor drive units, wherein the controller notifies the regenerative control device of status information indicating whether the multiple motors as a whole are in a regenerative state or a powered state, as described in claim 3.

6. The electric system according to claim 5, further comprising: an energy storage device; and a DC / DC converter connected between the DC unit and the energy storage device for charging and discharging the energy storage device, wherein the controller notifies the regenerative control device of state information indicating whether the plurality of motors and the energy storage device as a whole are in a regenerative state or a powered state.

7. The electric system according to any one of claims 2 to 6, characterized in that the third function is a function that releases the restriction on the power in a predetermined direction, provided that the differential voltage, which is the result of subtracting the voltage of the DC section, from the DC system voltage, which is the voltage of the DC system, is lower than a predetermined upper limit and higher than a predetermined lower limit.

8. A regenerative control device applied to an electric motor system comprising: a motor drive unit that converts a DC voltage in a DC section into an AC voltage to drive a motor; and a rectifier unit connected between an AC system and the DC section, the device comprising: a state acquisition unit that acquires the voltage difference between the voltage of the DC system and the voltage of the DC section, and / or the current between the DC system and the DC section; and a current limiting unit that limits a predetermined directional power, which is power flowing in the direction from the DC section to the DC system, based on the information acquired by the state acquisition unit.

9. The regenerative control device according to claim 8, comprising a calculation unit and a power supply unit, wherein the state acquisition unit and the current limiting unit are included in the calculation unit, and the power supply unit generates a voltage supplied to the calculation unit from the voltage of the DC unit.

10. The regenerative control device according to claim 8 or 9, wherein the motor drive unit is housed in a first housing that has a first connector for outputting motor drive information representing the operating state of the motor or the motor drive unit, and a pair of positive and negative first terminals for transmitting DC current, and further comprises a second housing having a shape that can be integrally formed with the first housing by physical mating, a second connector provided on the second housing for receiving the motor drive information by mating with the first connector when the second housing is mated with the first housing, a pair of positive and negative second terminals for transmitting DC current, and a pair of positive and negative connecting members that connect the first terminal and the second terminal and are substantially parallel when connected.

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