Power conversion device

Abstract

To provide a power conversion device capable of suppressing occurrence of unintended operation due to a communication error of a plurality of converters whose output sides are connected in parallel.SOLUTION: A power conversion device includes a main circuit unit that converts DC power into AC power and supplies the AC power to a load, and a control device that controls operation of the main circuit unit. The main circuit unit includes a plurality of converters connected in parallel to the load. The control device generates transmission data at each predetermined control period, and transmits, to the plurality of converters, a data set to which error detection information for enabling detection of occurrence of a communication error is added to a predetermined number of the transmission data from the current transmission data to the transmission data a predetermined number of transmissions before. The plurality of converters include a plurality of switching elements configured to convert the DC power into the AC power, and a control unit configured to control the plurality of switching elements based on the transmission data the predetermined number of transmissions before, included in the data set without a detected communication error.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD An embodiment of the present invention relates to a power conversion device. [Background technology]

[0002] There is a power conversion device that converts DC power into AC power and supplies it to a load. In such a power conversion device, a plurality of converters are provided with their output sides (AC sides) connected in parallel. In such a power conversion device, it is possible to supply power to a large-capacity load while suppressing an increase in the capacity of the elements used in each converter.

[0003] The power conversion device includes a control device. The control device controls the operation of each converter by transmitting predetermined data required for control to each converter. In this case, in a power conversion device in which the output sides of multiple converters are connected in parallel, if the magnitude of the output voltage of each converter differs, a cross current flows between each converter, which may cause the operation of the power conversion device to stop due to an operational abnormality of each converter (e.g., the occurrence of an overcurrent) or cause each converter to break down. For this reason, the control device controls the operation of each converter by transmitting data to each converter so that each converter outputs a voltage of the same magnitude.

[0004] However, communication errors may occur in the communication between the control device and each converter. If the content of the transmitted data from any of the converters is changed due to the occurrence of a communication error, the output voltage of each converter may change due to unintended operation of each converter, and cross currents may occur between the converters.

[0005] There is also a known method of correcting a communication error by detecting the occurrence of a communication error at each converter and requesting the control device to resend the transmission data in response to the error detection. However, with this method, an operational delay occurs between the converter where the communication error occurred and the other converters due to the resending of the transmission data, and there is a concern that cross currents may occur in each converter during this operational delay.

[0006] For this reason, in a power conversion device having multiple converters whose outputs are connected in parallel, it is desirable to be able to more appropriately prevent unintended operation of each converter due to communication errors. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2016 / 035217 Summary of the Invention [Problem to be solved by the invention]

[0008] An embodiment of the present invention provides a power conversion device that can suppress the occurrence of unintended operations due to communication errors among multiple converters whose output sides are connected in parallel. [Means for solving the problem]

[0009] According to an embodiment of the present invention, a power supply system includes a main circuit unit that converts DC power into AC power corresponding to a load and supplies the converted AC power to the load, and a control device that controls an operation of converting DC power into AC power by the main circuit unit, the main circuit unit having a plurality of converters connected in parallel to the load, the control device generates transmission data necessary for controlling the plurality of converters for each predetermined control period, and generates a data set to which error detection information is added so that occurrence of a communication error can be detected in a predetermined number of pieces of the transmission data from the generated current transmission data to the transmission data a predetermined number of times before, and transmits the data set to the plurality of converters, the plurality of converters each having a plurality of switching elements for converting DC power into AC power, and a control unit that controls conversion of DC power to AC power by the plurality of switching elements, wherein the control unit detects the communication error in the data set based on the error detection information included in the data set received from the control device, and extracts the transmission data from the predetermined number of times ago included in the data set in which the communication error was not detected based on the predetermined number of data sets from the data set currently received to the data set received the predetermined number of times ago, and uses the extracted transmission data from the predetermined number of times ago as the transmission data to be used for current control, thereby controlling conversion of DC power to AC power by the plurality of switching elements based on the extracted transmission data from the predetermined number of times ago. Effect of the Invention

[0010] According to an embodiment of the present invention, a power conversion device is provided that can suppress the occurrence of unintended operations due to communication errors among multiple converters whose outputs are connected in parallel. [Brief description of the drawings]

[0011] [Figure 1] 1 is a circuit diagram illustrating a power conversion device according to an embodiment of the present invention; [Diagram 2] FIG. 1 is a circuit diagram illustrating a converter according to an embodiment. [Diagram 3] FIG. 2 is a block diagram illustrating a control device according to the embodiment. [Figure 4] FIG. 4 is a block diagram illustrating a control unit of each converter according to the embodiment. [Diagram 5] FIG. 13 is a block diagram illustrating a modified example of the control unit of each converter according to the embodiment.

[0012] Each embodiment will be described below with reference to the drawings. The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between parts, etc. are not necessarily the same as in reality. Even when the same part is shown, the dimensions and ratios of each part may be different depending on the drawing. In this specification and each drawing, elements similar to those described above with reference to the previous drawings are given the same reference numerals and detailed descriptions thereof will be omitted as appropriate.

[0013] FIG. 1 is a circuit diagram that illustrates a power conversion device according to an embodiment. 1, the power conversion device 10 includes a main circuit unit 12 and a control device 14. The main circuit unit 12 is connected to a DC power source (not shown) and also to a load 2. More specifically, the load 2 is an AC load. The main circuit unit 12 converts DC power supplied from the DC power source into AC power corresponding to the load 2, and supplies the converted AC power to the load 2.

[0014] The DC power supply is, for example, another power conversion device that converts AC power supplied from a power grid into DC power. The DC power supply may be, for example, a distributed power source that outputs DC power, such as a solar panel. The DC power supply may be any device that can supply DC power to the main circuit unit 12.

[0015] The main circuit section 12 has a plurality of converters 20. Each of the plurality of converters 20 has, for example, a pair of DC terminals 20p, 20n and three AC terminals 20a to 20c.

[0016] A pair of DC terminals 20p, 20n of the multiple converters 20 are each connected to a DC power supply. In other words, a pair of DC terminals 20p, 20n of the multiple converters 20 are each connected in parallel. This allows a DC voltage supplied from the DC power supply to be input to each of the multiple converters 20. Note that a pair of DC terminals 20p, 20n of the multiple converters 20 may be connected in series. This allows the multiple converters 20 to share the DC voltage supplied from the DC power supply.

[0017] The three AC terminals 20a to 20c of each of the converters 20 are connected to the load 2. In other words, the three AC terminals 20a to 20c of each of the converters 20 are connected in parallel to the load 2. The main circuit unit 12 has the converters 20 connected in parallel to the load 2. When the AC terminals 20a to 20c of each of the converters 20 are connected in parallel in this manner, the converters 20 output AC power of the same phase, thereby increasing the current capacity and increasing the AC power supplied to the load 2 while suppressing an increase in the capacity of the elements used in each converter 20. The number of converters 20 may be any number.

[0018] The multiple converters 20 convert, for example, DC power supplied from a DC power source into three-phase AC power. The AC power of the load 2 is, for example, three-phase AC power. However, the AC power of the load 2 may be single-phase AC power or the like. The configuration of the main circuit unit 12 is not limited to the above, and may be any configuration having multiple converters 20 with their AC sides connected in parallel.

[0019] The control device 14 controls the operation of the main circuit section 12. More specifically, the control device 14 controls the operation of converting DC power to AC power by the main circuit section 12. The control device 14 controls the operation of converting DC power to AC power of each of the multiple converters 20. The control device 14 is configured to be able to communicate with each converter 20. The communication between the control device 14 and each converter 20 is two-way communication. Each converter 20 transmits information indicating an internal state, etc. to the control device 14. The control device 14 generates predetermined transmission data required for controlling each converter 20 based on the information received from each converter 20, and controls the operation of each converter 20 by transmitting the generated transmission data to each converter 20.

[0020] The main circuit section 12 further includes current detectors 30a to 30c. The current detectors 30a to 30c detect the magnitude of the AC current of the AC power supplied from the main circuit section 12 to the load 2, and input a detection signal indicating the detection result of the magnitude of the AC current to the control device 14. The current detectors 30a to 30c detect, for example, the magnitude of the line current of the three-phase AC power supplied from the main circuit section 12 to the load 2.

[0021] FIG. 2 is a circuit diagram illustrating a converter according to an embodiment. As shown in FIG. 2, each converter 20 includes a plurality of switching elements 40, a plurality of rectifying elements 41, and a charge storage element .

[0022] Each converter 20 has, for example, six switching elements 40 connected in a three-phase full bridge configuration, and six rectifier elements 41 connected in anti-parallel to each switching element 40. Both ends of the six switching elements 40 are connected to a pair of DC terminals 20p, 20n. A connection point between two switching elements 40 connected in series is connected to an AC terminal 20a. A connection point between two other switching elements 40 connected in series is connected to an AC terminal 20b. And a connection point between two other switching elements 40 connected in series is connected to an AC terminal 20c.

[0023] Each switching element 40 has a pair of main terminals and a control terminal. The control terminal is used to switch between an ON state in which a current flows between the main terminals and an OFF state in which substantially no current flows between the main terminals. Each switching element 40 is, for example, a self-extinguishing element such as a GTO (Gate Turn Off thyristor) or an IGBT (Insulated Gate Bipolar Transistor). The control terminal is, for example, a gate terminal. Each rectifying element 41 is, for example, a diode.

[0024] The charge storage element 42 is connected between the pair of DC terminals 20p, 20n. In other words, the charge storage element 42 is connected in parallel to each switching element 40. The charge storage element 42 suppresses, for example, fluctuations in the DC voltage input to the pair of DC terminals 20p, 20n. The charge storage element 42 is, for example, a capacitor.

[0025] Each converter 20 converts DC power supplied from a DC power source into AC power by switching of each switching element 40. In this example, each converter 20 converts DC power supplied from a DC power source into three-phase AC power by switching of each switching element 40. In other words, each switching element 40 is an element for converting DC power into AC power.

[0026] Each converter 20 further includes, for example, inductors 43a to 43c, a voltage detector 44, current detectors 45a to 45c, a control unit 46, and a detection circuit .

[0027] The inductors 43a to 43c are provided between the connection points of the two switching elements 40 connected in series and the AC terminals 20a to 20c, respectively. The inductances (parallel inductances) of the inductors 43a to 43c are set to as small a value as possible. This makes it possible to suppress, for example, an increase in manufacturing costs due to the inductors 43a to 43c.

[0028] The voltage detector 44 detects the magnitude of the DC voltage between the pair of DC terminals 20p, 20n, and inputs a detection signal indicating the detection result of the DC voltage magnitude to the control unit 46 and the detection circuit 48. In other words, the voltage detector 44 detects the magnitude of the DC voltage supplied from the DC power source. In other words, the voltage detector 44 detects the magnitude of the DC voltage across the charge storage element 42.

[0029] The current detectors 45a to 45c detect the magnitude of the AC current of the AC power output from the converter 20, and input a detection signal indicating the detection result of the AC current magnitude to the control unit 46 and the detection circuit 48. The current detectors 45a to 45c detect, for example, the magnitude of the line current of the three-phase AC power output from the converter 20.

[0030] The control unit 46 communicates with the control device 14. The control unit 46 controls the switching of each switching element 40 based on the transmission data received from the control device 14. In other words, the control unit 46 controls the operation of converting DC power into AC power by the multiple switching elements 40 (converter 20) based on the transmission data received from the control device 14. In addition, the control unit 46 transmits, for example, the detection signals of the voltage detector 44 and the current detectors 45a to 45c to the control device 14 as information required for generating the transmission data.

[0031] The detection circuit 48 detects whether or not the magnitude of the DC voltage between the pair of DC terminals 20p, 20n detected by the voltage detector 44 is equal to or greater than an overvoltage detection level. The detection circuit 48 also detects whether or not the magnitude of the AC current of the AC power output from the converter 20 detected by the current detectors 45a to 45c is equal to or greater than an overcurrent detection level. The detection circuit 48 transmits a stop command to the control unit 46 when it detects a voltage equal to or greater than the overvoltage detection level or when it detects a voltage equal to or greater than the overcurrent detection level.

[0032] The control unit 46 stops the switching of each switching element 40 in response to the input of the stop command from the detection circuit 48. In other words, the control unit 46 stops the operation of converting DC power to AC power by the converter 20 in response to the input of the stop command from the detection circuit 48.

[0033] In the main circuit section 12, the multiple converters 20 have substantially the same configuration. The control device 14 transmits, for example, the same transmission data to each of the multiple converters 20. In addition, at this time, a transmission delay between the control device 14 and each converter 20 is set so that the transmission data transmitted from the control device 14 is received by the control unit 46 of each converter 20 substantially simultaneously. The transmission delay is set, for example, by the length of a communication cable between the control device 14 and each converter 20.

[0034] As a result, AC power of substantially the same magnitude, frequency, and phase can be output from each converter 20 substantially simultaneously by transmission data transmitted from the control device 14 to each converter 20. As a result, even when the AC sides of multiple converters 20 are connected in parallel, the occurrence of cross currents flowing between each converter 20 can be suppressed.

[0035] The difference between the longest transmission delay and the shortest transmission delay in each converter 20 is determined by, for example, the inductance value of the inductors 43a to 43c, the rated value of the magnitude of the DC voltage between the DC terminals 20p and 20n, and the allowable cross current flowing between each converter 20. Specifically, the AC output voltage of each converter 20 is assumed to differ by the time of the difference in transmission delay, and the design value of the cross current to be generated is determined by multiplying the difference in the transmission delay time by the difference in the AC output voltage and further dividing the result by the inductance value of the inductors 43a to 43c. The allowable range of the difference in the transmission delay time is specified so that the design value of the cross current falls within the allowable range. In cases where it is known in advance that the lengths of the communication cables between the control device 14 and each converter 20 are different, the difference in the total delay time can be made equal to or less than the specified value by inserting a separate delay element in the transmission path with a short delay time.

[0036] FIG. 3 is a block diagram illustrating a control device according to the embodiment. As shown in FIG. 3, the control device 14 includes a calculator 50, a dq conversion circuit 51, a current controller 52, an inverse dq conversion circuit 53, a phase generation circuit 54, a calculator 55, limiters 56a to 56c, a control signal generation circuit 57, and dead time setting circuits 58a to 58c.

[0037] The phase generation circuit 54 receives a phase reference θ of the AC current output from the main circuit unit 12. The phase generation circuit 54 calculates the phase sin θ and cos θ of the AC current output from the main circuit unit 12 based on the input phase reference θ, and inputs the calculated phases sin θ and cos θ to the dq transformation circuit 51 and the inverse dq transformation circuit 53.

[0038] The calculator 50 receives detection signals indicating the magnitude of the AC current supplied from the main circuit unit 12 to the load 2, which are detected by the current detectors 30a to 30c. The calculator 50 multiplies the input detection signals by a predetermined coefficient to standardize (normalize) the detected magnitude of the AC current of the main circuit unit 12, and inputs the normalized magnitude of the AC current of the main circuit unit 12 to the dq conversion circuit 51.

[0039] The dq conversion circuit 51 converts the three-phase current signals (detection signals) of the three-phase AC power into d-axis component current signals and q-axis component current signals in a coordinate system (dq coordinates) synchronized with the phase reference θ, based on the three-phase current signals (detection signals) and phase sin θ and cos θ. The dq conversion circuit 51 converts the three-phase current signals into d-axis component current signals and q-axis component current signals by, for example, Park transformation. The dq conversion circuit 51 inputs the converted d-axis component current signals and q-axis component current signals to a current controller 52.

[0040] The current controller 52 receives the d-axis component current signal and the q-axis component current signal, as well as the d-axis component current command value and the q-axis component current command value of the AC current output from the main circuit unit 12. The d-axis component current command value, the q-axis component current command value, and the phase reference θ are input to the control device 14 from, for example, a higher-level controller. However, the d-axis component current command value, the q-axis component current command value, and the phase reference θ may be, for example, constant values ​​set in advance, or may be manually input to the control device 14 via an operation unit or the like.

[0041] Based on the input d-axis component current signal and d-axis component current command value, the current controller 52 calculates a d-axis component voltage command value of the AC voltage to be output from the main circuit unit 12 in order to bring the d-axis component current signal closer to the d-axis component current command value. Based on the input q-axis component current signal and q-axis component current command value, the current controller 52 calculates a q-axis component voltage command value of the AC voltage to be output from the main circuit unit 12 in order to bring the q-axis component current signal closer to the q-axis component current command value. The current controller 52 inputs the calculated d-axis component voltage command value and q-axis component voltage command value to the inverse dq transformation circuit 53.

[0042] The inverse dq transformation circuit 53 converts the d-axis component voltage command value and the q-axis component voltage command value into three-phase voltage command values ​​(voltage reference) based on the input d-axis component voltage command value, q-axis component voltage command value, and phases sinθ and cosθ. The inverse dq transformation circuit 53 converts the d-axis component voltage command value and the q-axis component voltage command value into three-phase voltage command values ​​by, for example, inverse Park transformation. The inverse dq transformation circuit 53 inputs the converted three-phase voltage command values ​​to the calculator 55.

[0043] The calculator 55 multiplies each of the input three-phase voltage command values ​​by a predetermined coefficient to standardize (normalize) the magnitude of the three-phase voltage command values, and inputs the standardized three-phase voltage command values ​​to limiters 56a to 56c.

[0044] The limiters 56a to 56c set upper and lower limit values ​​for the input voltage command value. When the input voltage command value is equal to or greater than the upper limit value, the limiters 56a to 56c limit the voltage command value to the upper limit value. When the input voltage command value is equal to or less than the lower limit value, the limiters 56a to 56c limit the voltage command value to the lower limit value. The limiters 56a to 56c input the processed voltage command value to the control signal generating circuit 57.

[0045] The control signal generating circuit 57 receives the voltage command values ​​for each phase of the three-phase AC voltage output from each converter 20, as well as a carrier signal. The carrier signal is, for example, a triangular wave signal having a higher frequency than the frequency of the AC voltage output from the main circuit unit 12 (each converter 20). In other words, the carrier signal is a carrier wave.

[0046] The control signal generating circuit 57 generates three-phase control signals for controlling the switching of each switching element 40 of each converter 20 by comparing the three-phase voltage command values ​​with the carrier signal. For example, the control signal generating circuit 57 generates a control signal for turning on the switching element 40 when the voltage command value is larger than the carrier signal, and for turning off the switching element 40 when the voltage command value is smaller than the carrier signal. For example, the control signal generating circuit 57 generates a control signal (pulse signal) for controlling the switching of each switching element 40 of each converter 20 by PWM (Pulse Width Modulation) control. The control signal generating circuit 57 inputs the generated three-phase control signals to the dead time setting circuits 58a to 58c.

[0047] The dead time setting circuits 58a to 58c receive the control signals for three phases generated by the control signal generating circuit 57, and also receive the control signals for three phases with their logic inverted via a NOT gate. The control signals for three phases are used, for example, for switching the three upper switching elements 40. The control signals for three phases with their logic inverted are used, for example, for switching the three lower switching elements 40.

[0048] The dead time setting circuits 58a to 58c set a dead time for preventing the upper switching element 40 and the lower switching element 40 from being turned on simultaneously in the control signal, thereby generating six control signals corresponding to the six switching elements 40 of each converter 20. The dead time setting circuits 58a to 58c input the six generated control signals to the storage unit 60.

[0049] The storage unit 60 stores the six control signals input from the dead time setting circuits 58a to 58c as current transmission data. The storage unit 60 is configured to be able to store a predetermined number of transmission data (six control signals) up to n times (a predetermined number of times, n being a natural number). Every time transmission data is input from the dead time setting circuits 58a to 58c, the storage unit 60 updates the stored transmission data up to n times prior so as to replace the input current transmission data with the oldest transmission data.

[0050] The control device 14 generates a control signal for each predetermined control period, and stores the generated control signal as transmission data in the storage unit 60. In other words, the control device 14 generates transmission data necessary for controlling each converter 20 for each predetermined control period, and stores the generated current transmission data in the storage unit 60. The control device 14 then generates a data set DS in which error detection information is added to a predetermined number of transmission data from the current transmission data to the transmission data n times prior stored in the storage unit 60, and transmits the generated data set DS to each converter 20, thereby controlling the operation of each converter 20.

[0051] The error detection information is information that enables each converter 20 to detect the occurrence of a communication error in the transmission data. The error detection information is, for example, an error detection bit string for detecting the occurrence of a communication error by CRC (Cyclic Redundancy Check). However, the error detection information is not limited to this, and may be any information that allows each converter 20 to appropriately detect the occurrence of a communication error. The error detection information may be, for example, a check bit used for a parity check.

[0052] In this example, the control signals generated by the dead time setting circuits 58a to 58c are transmitted as transmission data to each converter 20, but the transmission data transmitted from the control device 14 to each converter 20 is not limited to this. For example, detection signals of AC currents detected by the current detectors 30a to 30c may be transmitted as transmission data to each converter 20, and the subsequent processing may be performed on the control unit 46 side of each converter 20. In this way, the content of the transmission data transmitted from the control device 14 to each converter 20 may be any signal between the calculator 50 and the dead time setting circuits 58a to 58c. The transmission data transmitted from the control device 14 to each converter 20 may be any data capable of appropriately controlling the operation of each converter 20.

[0053] FIG. 4 is a block diagram illustrating a control unit of each converter according to the embodiment. As shown in FIG. 4, the control unit 46 of each converter 20 includes a storage unit 70, a data selection unit 72, and an AND circuit 74.

[0054] The storage unit 70 stores the data set DS received from the control device 14. The storage unit 70 is configured to be able to store a predetermined number of data sets DS up to n times prior. Every time the storage unit 70 receives a data set DS from the control device 14, the storage unit 70 updates the stored data set DS up to n times prior so as to replace the oldest data set DS with the currently received data set DS.

[0055] The data selection unit 72 selects transmission data to be used for the current control based on the data sets DS up to the nth previous time stored in the storage unit 70. The data selection unit 72 selects transmission data to be used for the current control, for example, every time a data set DS received from the control device 14 is stored in the storage unit 70.

[0056] When selecting the transmission data to be used for the current control, the data selection unit 72 first detects whether or not a communication error has occurred in the currently received data set DS, based on the error detection information (error detection bit string) contained in the currently received data set DS stored in the memory unit 70.

[0057] When the data selection unit 72 detects that no communication error has occurred, it selects the transmission data from n times ago, which is included in the currently received data set DS, as the transmission data to be used for the current control.

[0058] On the other hand, when the data selection unit 72 detects that a communication error has occurred, it detects whether or not a communication error has occurred in the previously received data set DS, based on the error detection information contained in the previously received data set DS stored in the memory unit 70.

[0059] The data selection unit 72 performs similar processing thereafter to select the transmission data from the nth time ago included in the data set DS in which no communication error occurred, from the data sets DS up to the nth time ago stored in the memory unit 70, as the transmission data to be used for the current control.

[0060] In this way, the control unit 46 detects a communication error in the data set DS based on the error detection information included in the data set DS received from the control device 14, and extracts transmission data from a predetermined number of times ago included in the data set DS in which no communication error was detected, based on a predetermined number of data sets DS from the currently received data set DS to the data set DS received a predetermined number of times ago (n times ago). In this example, the control unit 46 stores a predetermined number of data sets DS, and extracts transmission data from a predetermined number of times ago included in the data set DS in which no communication error was detected, from the stored predetermined number of data sets DS. Then, the control unit 46 uses the extracted transmission data from a predetermined number of times ago as the transmission data to be used for the current control, and controls the conversion of DC power to AC power by the multiple switching elements 40, based on the extracted transmission data from a predetermined number of times ago.

[0061] The detection of the data set DS in which no communication error has occurred does not necessarily have to be performed from the currently received data set DS as described above. The data set DS in which no communication error has occurred may be any data set DS in which no communication error has occurred among the data sets DS up to the nth data set before stored in the storage unit 70.

[0062] After selecting the transmission data to be used for the current control, the data selection unit 72 inputs a control signal based on the selected transmission data to the AND circuit 74. The data selection unit 72 inputs, for example, six control signals included in the transmission data to the AND circuit 74. For example, when detection signals of AC currents detected by the current detectors 30a to 30c are included in the transmission data, a control signal may be generated based on the detection signals and the generated control signal may be input to the AND circuit 74. In this case, for example, each circuit from the calculator 50 to the dead time setting circuits 58a to 58c may be provided in the data selection unit 72 (control unit 46).

[0063] The AND circuit 74 receives a control signal from the data selection unit 72 and a stop command from the detection circuit 48. The AND circuit 74 inputs a control signal to each switching element 40 when an overvoltage or overcurrent is not detected by the detection circuit 48. This causes the control unit 46 to control the switching of each switching element 40 based on the data set DS (transmission data) received from the control device 14. Then, the AND circuit 74 stops inputting the control signal to each switching element 40 when an overvoltage or overcurrent is detected by the detection circuit 48. This makes it possible to stop the operation of the converter 20 to convert DC power to AC power when an overvoltage or overcurrent is detected by the detection circuit 48.

[0064] Furthermore, when the control unit 46 is unable to extract transmission data from a predetermined number of times back included in a data set DS in which no communication error was detected, the control unit 46 stops the operation of converting DC power to AC power by the multiple switching elements 40. For example, when a communication error is detected in all of the data sets DS up to n times back stored in the storage unit 70, there is a concern that an abnormality has occurred in the communication device. Therefore, when the control unit 46 is unable to detect a data set DS in which no communication error has occurred in the data selection unit 72, for example, the control unit 46 stops the operation of converting DC power to AC power by the multiple switching elements 40 by inputting a stop command from the data selection unit 72 to the AND circuit 74.

[0065] Furthermore, when a communication error of the data set DS is detected a specified number of times or more within a predetermined period, there is a concern that an abnormality has occurred in the communication device, as in the above. Therefore, when a communication error of the data set DS is detected a specified number of times or more within a predetermined period, the control unit 46 performs an operation at the time of abnormality. The operation at the time of abnormality is, for example, an operation of stopping the operation of converting DC power to AC power by the multiple switching elements 40. The operation at the time of abnormality may be, for example, an operation of notifying a user (such as an administrator of the power conversion device 10) of the detection of an abnormality. The operation at the time of abnormality may be any operation that can suppress a breakdown of the device due to the occurrence of a communication error. Note that the specified number of times may be set to, for example, less than the number of the specified number of data sets DS stored in the storage unit 70, or more than the number of the specified number of data sets DS stored in the storage unit 70. The specified number of times may be any number of times.

[0066] When the control unit 46 stops the operation of the multiple switching elements 40 converting DC power to AC power, for example, the control unit 46 transmits a stop of the operation to the control device 14. When the control device 14 receives a stop of the operation from the control unit 46 of any of the multiple converters 20, the control device 14 also stops the operation of the other converters 20. In other words, the control device 14 stops the operation of the main circuit unit 12 in response to the stop of the operation of any of the multiple converters 20. However, in the main circuit unit 12 in which multiple converters 20 are connected in parallel, even when the operation of any of the multiple converters 20 stops, there is a possibility that the remaining converters 20 can continue operation. In such a case, the remaining converters 20 may continue operation until the number of converters 20 that have stopped operation reaches a predetermined number.

[0067] As described above, in the power conversion device 10 according to this embodiment, the control device 14 generates a data set DS in which error detection information is added to a predetermined number of pieces of transmission data from the current transmission data to the transmission data a predetermined number of times ago, and transmits the generated data set DS to each converter 20. Then, the control unit 46 of each converter 20 detects a communication error in the data set DS based on the error detection information included in the data set DS received from the control device 14, and extracts transmission data a predetermined number of times ago included in the data set DS in which no communication error was detected based on a predetermined number of data sets DS from the data set DS received currently to the data set DS received a predetermined number of times ago, and sets the extracted transmission data a predetermined number of times ago as the transmission data to be used for the current control, thereby controlling conversion from DC power to AC power by the multiple switching elements 40 based on the extracted transmission data a predetermined number of times ago.

[0068] As a result, in the power conversion device 10 according to this embodiment, even if a communication error occurs in any of a predetermined number of data sets DS from the currently received data set DS to the data set DS received a predetermined number of times before, the operation of the multiple switching elements 40 can be appropriately controlled by the other data sets DS with which communication was performed normally. Furthermore, unlike the case where the control device 14 is requested to resend the transmission data, no operation delay occurs due to the resending of the transmission data. Therefore, in the power conversion device 10 according to this embodiment, it is possible to more appropriately suppress the occurrence of unintended operation of each converter 20 due to a communication error.

[0069] In addition, when the communication device or the like is operating normally, the frequency of occurrence of communication errors is not very high. Therefore, the predetermined number of transmission data included in the data set DS and the predetermined number of data sets DS from the data set DS received this time to the data set DS received a predetermined number of times before may be one or two. In this way, by setting the predetermined number to about one or two, for example, it is possible to suppress the occurrence of unintended operation of each converter 20 due to a communication error while suppressing the capacity required for the storage units 60 and 70, and to suppress an increase in communication capacity due to the transmission of the data set DS. On the other hand, when the predetermined number is set to three or more, for example, it is possible to more appropriately suppress the occurrence of unintended operation of each converter 20 due to a communication error, and to further suppress the occurrence of abnormal stop of each converter 20. The predetermined number may be set arbitrarily according to the frequency of occurrence of communication errors, etc.

[0070] Furthermore, in the power conversion device 10 according to this embodiment, the control unit 46 stores a predetermined number of data sets DS, and extracts, from the stored predetermined number of data sets DS, transmission data that occurred a predetermined number of times ago and is included in the data set DS in which no communication error was detected. This allows appropriate extraction of transmission data that occurred a predetermined number of times ago and is included in the data set DS in which no communication error was detected.

[0071] Furthermore, in the power conversion device 10 according to this embodiment, when the control unit 46 is unable to extract transmission data from a predetermined number of times ago included in the data set DS in which no communication error was detected, the control unit 46 stops the operation of converting DC power to AC power by the multiple switching elements 40. This makes it possible to more appropriately suppress the occurrence of unintended operation of each converter 20 due to, for example, an abnormality in a communication device.

[0072] Furthermore, in the power conversion device 10 according to this embodiment, when the control unit 46 detects a communication error in the data set DS a prescribed number of times or more within a predetermined period, it performs an abnormality operation. This makes it possible to more appropriately suppress the occurrence of unintended operation of each converter 20 due to, for example, an abnormality in a communication device.

[0073] FIG. 5 is a block diagram showing a schematic diagram of a modified example of the control unit of each converter according to the embodiment. As shown in FIG. 5, a control unit 46a of the modified example includes a storage unit 70a that stores transmission data in which no communication error has been detected.

[0074] The control unit 46a detects a communication error in the data set DS when receiving the data set DS from the control device 14. If no communication error is detected, the control unit 46a performs a process of storing the transmission data included in the currently received data set DS in the storage unit 70a. On the other hand, if a communication error is detected, the control unit 46a does not perform a process of storing the transmission data in the storage unit 70a.

[0075] The storage unit 70a has n storage areas corresponding to, for example, the transmission data from n times ago (a predetermined number of times ago) to the transmission data one time ago. The storage unit 70a stores each of the transmission data from the n times ago to the transmission data one time ago in each storage area. Each storage area is provided with a reflection flag for checking whether or not the transmission data in which no communication error was detected has been reflected. The reflection flag is set to "0", for example, when the transmission data in which no communication error was detected has not been reflected, and is set to "1" when the transmission data in which no communication error was detected has been reflected.

[0076] In this example, the data selection unit 72a refers to the reflection flag of the storage area corresponding to the transmission data n times ago stored in the storage unit 70a when receiving the data set DS from the control device 14. If the reflection flag of the storage area corresponding to the transmission data n times ago is in a state indicating that the transmission data in which no communication error was detected has been reflected, the data selection unit 72a selects the transmission data n times ago stored in the storage area as the transmission data to be used for the current control.

[0077] If the reflected flag in the memory area corresponding to the transmission data n times ago is in a state indicating that the transmission data in which no communication error was detected has not been reflected, and no communication error has occurred in the data set DS currently received from the control device 14, the data selection unit 72a selects the transmission data from n times ago included in the data set DS currently received as the transmission data to be used for the current control.

[0078] Then, when the reflection flag in the storage area corresponding to the transmission data n times ago is in a state indicating that the transmission data in which no communication error was detected has not been reflected and a communication error has occurred in the data set DS currently received from the control device 14, the data selection unit 72a inputs a stop command to the AND circuit 74. Thereby, similarly to the above embodiment, when the transmission data in the predetermined number of times ago included in the data set DS in which no communication error was detected cannot be extracted, the operation of converting DC power to AC power by the multiple switching elements 40 can be stopped.

[0079] In this manner, the control unit 46a extracts the transmission data from the storage unit 70a or the currently received data set DS, which is included in the data set DS in which no communication error was detected, the transmission data being transmitted a predetermined number of times before.

[0080] If no communication error is detected in the data set DS received this time, the control unit 46a performs a process of extracting transmission data from a predetermined number of times ago and then storing the transmission data in the storage unit 70a. In the process of storing the transmission data in the storage unit 70a, the control unit 46a erases the transmission data from n times ago stored in the storage area, and shifts the transmission data from the previous time to the (n-1) times ago by one, so that the transmission data from the second time ago to the n times ago transmission data is shifted by one. At this time, the control unit 46a also shifts the content of the reflection completion flag by one in correspondence with each transmission data.

[0081] After shifting the contents of each transmission data and the reflection completion flag, the control unit 46a stores the current transmission data included in the currently received data set DS as the previous transmission data in the corresponding storage area of ​​the storage unit 70a. In other words, the control unit 46a reflects the current transmission data included in the currently received data set DS in the storage area of ​​the previous transmission data. Then, the control unit 46a changes the reflection completion flag corresponding to the storage area of ​​the previous transmission data from the unreflected state to the reflected state.

[0082] Furthermore, if there is a reflection flag in an unreflected state between the transmission data two times ago and the transmission data n times ago, the control unit 46a stores the corresponding transmission data included in the currently received data set DS in a corresponding storage area of ​​the storage unit 70a, and changes the corresponding reflection flag from an unreflected state to a reflected state. For example, if there is a communication error in the data set DS received one time ago, and the reflection flag corresponding to the storage area of ​​the transmission data two times ago in the storage unit 70a is also in an unreflected state, the control unit 46a stores the transmission data one time ago included in the currently received data set DS in the corresponding storage area of ​​the storage unit 70a as the transmission data two times ago, and changes the corresponding reflection flag from an unreflected state to a reflected state.

[0083] This causes the transmission data to be stored in the memory unit 70a, and the next time the data set DS is received, as described above, the transmission data from a predetermined number of times ago that is included in the data set DS in which no communication error was detected can be extracted from the memory unit 70a or the currently received data set DS.

[0084] In this way, the control unit 46a has a memory unit 70a that stores transmission data in which no communication error was detected, and when it receives a data set DS from the control device 14, it detects a communication error in the data set DS, and if no communication error is detected, it performs a process of storing the transmission data included in the currently received data set DS in the memory unit 70a, and if a communication error is detected, it does not perform a process of storing the transmission data in the memory unit 70a, thereby extracting the transmission data from a predetermined number of times ago included in the data set DS in which no communication error was detected from the memory unit 70a or the currently received data set DS.

[0085] In this case, similarly to the above embodiment, the transmission data a predetermined number of times back included in the data set DS in which no communication error was detected can be appropriately extracted. In addition, in a configuration in which n memory areas corresponding to the transmission data n times back to the transmission data one time back are provided in the storage unit 70a, the storage capacity required in the storage unit 70a can be reduced and the configuration of the storage unit 70a can be simplified compared to a configuration in which a predetermined number of data sets DS are stored in the storage unit 70 as shown in FIG. 4. In a configuration in which n memory areas are provided in the storage unit 70a, the required storage capacity can be reduced to, for example, the amount of storage capacity required for one data set DS. Therefore, the transmission data a predetermined number of times back can be appropriately extracted with a simpler configuration.

[0086] The present embodiment includes the following aspects. (Appendix 1) a main circuit unit that converts DC power into AC power corresponding to a load and supplies the converted AC power to the load; a control device for controlling an operation of converting DC power to AC power by the main circuit unit; Equipped with the main circuit unit has a plurality of converters connected in parallel to the load, the control device generates transmission data necessary for controlling the plurality of converters at each predetermined control period, generates a data set to which error detection information is added for enabling detection of occurrence of a communication error in a predetermined number of pieces of the transmission data from the currently generated transmission data to the transmission data a predetermined number of times before, and transmits the data set to the plurality of converters; the plurality of converters each include a plurality of switching elements for converting DC power to AC power, and a control unit that controls the conversion of DC power to AC power by the plurality of switching elements; the control unit detects the communication error in the data set based on the error detection information included in the data set received from the control device, and extracts the transmission data from the predetermined number of times ago included in the data set in which the communication error was not detected based on the predetermined number of data sets from the data set currently received to the data set received the predetermined number of times ago, and uses the extracted transmission data from the predetermined number of times ago as the transmission data to be used for current control, thereby controlling conversion of DC power to AC power by the multiple switching elements based on the extracted transmission data from the predetermined number of times ago.

[0087] (Appendix 2) The control unit stores the predetermined number of data sets and extracts the transmission data from the predetermined number of data sets that is included in a data set in which no communication error was detected from the stored predetermined number of data sets.

[0088] (Appendix 3) The control unit has a memory unit that stores the transmission data in which the communication error was not detected, and when receiving the data set from the control device, detects the communication error in the data set, and if the communication error is not detected, performs a process of storing the transmission data included in the currently received data set in the memory unit, and if the communication error is detected, does not perform a process of storing the transmission data in the memory unit, thereby extracting the transmission data from the predetermined number of times ago included in the data set in which the communication error was not detected from the memory unit or the currently received data set.

[0089] (Appendix 4) The power conversion device according to any one of appendices 1 to 3, wherein the control unit stops the operation of converting DC power to AC power by the multiple switching elements when it is unable to extract the transmission data from the predetermined number of times ago that is included in the data set in which the communication error was not detected.

[0090] (Appendix 5) 5. The power conversion device according to claim 1, wherein the control unit performs an abnormality operation when the communication error of the data set is detected a prescribed number of times or more within a predetermined period.

[0091] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0092] 2...load, 10...power conversion device, 12...main circuit section, 14...control device, 20...converter, 30a to 30c...current detector, 40...switching element, 41...rectifier element, 42...charge storage element, 43a to 43c...inductor, 44...voltage detector, 45a to 45c...current detector, 46, 46a...control section, 48...detection circuit, 50...operator, 51...dq conversion circuit, 52...current controller, 53...inverse dq conversion circuit, 54...phase generation circuit, 55...operator, 56a to 56c...limiter, 57...control signal generation circuit, 58a to 58c...dead time setting circuit, 60...storage section, 70, 70a...storage section, 72, 72a...data selection section, 74...AND circuit, DS...data set

Claims

1. a main circuit unit that converts DC power into AC power corresponding to a load and supplies the converted AC power to the load; a control device for controlling an operation of converting DC power to AC power by the main circuit unit; Equipped with the main circuit unit has a plurality of converters connected in parallel to the load, the control device generates transmission data necessary for controlling the plurality of converters at each predetermined control period, generates a data set to which error detection information is added for enabling detection of occurrence of a communication error in a predetermined number of pieces of the transmission data from the currently generated transmission data to the transmission data a predetermined number of times before, and transmits the data set to the plurality of converters; the plurality of converters each include a plurality of switching elements for converting DC power to AC power, and a control unit that controls the conversion of DC power to AC power by the plurality of switching elements; the control unit detects the communication error in the data set based on the error detection information included in the data set received from the control device, and extracts the transmission data from the predetermined number of times ago included in the data set in which the communication error was not detected based on the predetermined number of data sets from the data set currently received to the data set received the predetermined number of times ago, and uses the extracted transmission data from the predetermined number of times ago as the transmission data to be used for current control, thereby controlling conversion of DC power to AC power by the multiple switching elements based on the extracted transmission data from the predetermined number of times ago.

2. 2. The power conversion device according to claim 1, wherein the control unit stores the predetermined number of data sets and extracts the transmission data from the predetermined number of times ago that is included in a data set in which the communication error was not detected from the stored predetermined number of data sets.

3. The control unit has a memory unit that stores the transmission data in which the communication error was not detected, and when receiving the data set from the control device, detects the communication error in the data set, and if the communication error is not detected, performs a process of storing the transmission data included in the currently received data set in the memory unit, and if the communication error is detected, does not perform a process of storing the transmission data in the memory unit, thereby extracting the transmission data from the predetermined number of times ago included in the data set in which the communication error was not detected from the memory unit or the currently received data set.

4. 2. The power conversion device according to claim 1, wherein the control unit stops an operation of converting DC power to AC power by the multiple switching elements when it is unable to extract the transmission data from the predetermined number of times before that which is included in the data set in which the communication error was not detected.

5. The power conversion device according to claim 1 , wherein the control unit performs an abnormality operation when the communication error of the data set is detected a prescribed number of times or more within a predetermined period.

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