Power converter

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] Embodiments of the present invention relate to power converters. [Background Art]

[0002] There are power converters that convert DC power into AC power and supply the AC power to loads. In such power converters, it is common practice to provide a plurality of converters whose output sides (AC sides) are connected in parallel. With such a power converter, power can be supplied to a large-capacity load while suppressing an increase in the capacity of elements used in each converter.

[0003] The power converter 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 regard, in a power converter in which the output sides of a plurality of converters are connected in parallel, if the output voltages of the converters have different magnitudes, a cross current, which is a current flowing between the converters, will occur. This cross current may cause factors such as shutdown of the power converter operation due to abnormal operation of any converter (e.g., occurrence of overcurrent) or failure of the converters. For this reason, the control device controls the operation of each converter by transmitting data to each converter such that converters output voltages of the same magnitude.

[0004] However, communication errors may occur in communication between the control device and each converter. If the content of transmitted data to any converter changes due to a communication error, unintended operation of the converter will cause a change in the output voltage of the converter, resulting in a possibility of cross current occurring between the converters.

[0005] There is also a known method for correcting communication errors, in which each converter detects the occurrence of a communication error and requests the control device to retransmit the data according to the error detection. However, in such a method, an operation delay caused by data retransmission occurs between the converter where the communication error occurred and other converters, and there is concern that cross current may occur in the converters during this operation delay.

[0006] Therefore, in power converters having multiple converters connected in parallel on their output sides, it is desirable to be able to more effectively suppress the occurrence of unintended operation of each converter due to communication errors. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2016 / 035217 [Overview of the project] [Problems that the invention aims to solve]

[0008] Embodiments of the present invention provide a power conversion device that can suppress the occurrence of unintended operation due to communication errors in multiple converters connected in parallel on their output sides. [Means for solving the problem]

[0009] According to embodiments of the present invention, Multiple converters are connected in parallel to a load to which the AC power is supplied, each including multiple switching elements and a control unit that controls the multiple switching elements to convert DC power to AC power. And, as stated above Multiple converters strange Motion Control operation The transmission data is generated at predetermined control cycles. A control device, and 、 The control device is The aforementioned Data to send of Generate Each time , This generated transmission data and 1 to n times before generated n pieces Data to send A dataset is generated containing n+1 transmitted data and error detection information for these n+1 transmitted data. The aforementioned generated The dataset is transmitted to the multiple converters, When each of the plurality of control units receives the dataset from the control device, it uses the error detection information contained in the received dataset to determine whether a communication error has occurred in the received dataset. If it determines that no communication error has occurred, it controls the plurality of switching elements using the transmission data generated n times ago contained in the received dataset. If it determines that a communication error has occurred, it identifies a dataset received k times ago (where k is any of 1 to n) times ago from the datasets received 1 to n times ago, which was determined not to have a communication error based on the error detection information. It then controls the plurality of switching elements using the transmission data generated nk times ago in this k-th-ago dataset (however, if k=n, the last generated transmission data included in the dataset received k times ago). A power converter is provided. [Effects 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 operation due to communication errors in multiple converters connected in parallel on their output sides. [Brief explanation of the drawing]

[0011] [Figure 1] It is a circuit diagram schematically illustrating the power conversion device according to the embodiment. [Figure 2] It is a circuit diagram schematically illustrating the converter according to the embodiment. [Figure 3] It is a block diagram schematically illustrating the control device according to the embodiment. [Figure 4] It is a block diagram schematically illustrating a control unit of each converter according to the embodiment. [Figure 5] It is a block diagram schematically 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. Note that the drawings are schematic or conceptual, and the relationship between the thickness and width of each portion, the size ratio between portions, and the like are not necessarily the same as those in reality. Further, even when the same portion is illustrated, the dimensions and ratios may be different in different drawings. In the present specification and each drawing, the same reference numerals are assigned to elements that are the same as those described above with reference to the already presented drawings, and detailed descriptions thereof are omitted as appropriate.

[0013] FIG. 1 is a circuit diagram schematically illustrating the power conversion device according to the embodiment. As illustrated in FIG. 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 supply (not illustrated) and is connected 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 supply 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 an electric power system into DC power. The DC power supply may be, for example, a distributed power supply that outputs DC power such as a solar panel. The DC power supply may be any device capable of supplying DC power to the main circuit unit 12.

[0015] The main circuit unit 12 includes a plurality of converters 20. The plurality of converters 20 include, for example, a pair of DC terminals 20p and 20n, and three AC terminals 20a to 20c.

[0016] The pair of DC terminals 20p and 20n of the plurality of converters 20 are each connected to a DC power supply. In other words, the pair of DC terminals 20p and 20n of the plurality of converters 20 are each connected in parallel. Accordingly, a DC voltage supplied from the DC power supply is input to each of the plurality of converters 20. Note that the pair of DC terminals 20p and 20n of the plurality of converters 20 may be connected in series. This allows the DC voltage supplied from the DC power supply to be shared among the plurality of converters 20.

[0017] The three AC terminals 20a to 20c of each of the plurality of converters 20 are each connected to a load 2. In other words, the three AC terminals 20a to 20c of each of the plurality of converters 20 are connected in parallel with respect to the load 2. The main circuit unit 12 includes the plurality of converters 20 connected in parallel with respect to the load 2. When the AC terminals 20a to 20c of each converter 20 are connected in parallel as described above, outputting in-phase AC power from each converter 20 increases the current capacity, and it is possible to increase the AC power supplied to the load 2 while suppressing an increase in the capacity of elements used in each converter 20. The number of converters 20 may be any number.

[0018] The plurality of converters 20 convert, for example, DC power supplied from a DC power supply 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 including a plurality of converters 20 with AC sides connected in parallel.

[0019] The control device 14 controls the operation of the main circuit unit 12. More specifically, the control device 14 controls the operation of the main circuit unit 12 in converting DC power to AC power. The control device 14 controls the operation of each of the multiple converters 20 in converting DC power to AC power. The control device 14 is configured to communicate with each converter 20. Communication between the control device 14 and each converter 20 is bidirectional. Each converter 20 transmits information representing its internal state to the control device 14. Based on the information received from each converter 20, the control device 14 generates predetermined transmission data necessary for controlling 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 unit 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 unit 12 to the load 2, and input a detection signal representing the detection result of the magnitude of the AC current to the control device 14. For example, the current detectors 30a to 30c detect the magnitude of the line current of the three-phase AC power supplied from the main circuit unit 12 to the load 2.

[0021] Figure 2 is a schematic circuit diagram showing the converter according to the embodiment. As shown in Figure 2, each converter 20 has a plurality of switching elements 40, a plurality of rectifier elements 41, and a charge storage element 42.

[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 antiparallel to each switching element 40. The ends of the six switching elements 40 are connected to a pair of DC terminals 20p and 20n. The connection point of two switching elements 40 connected in series is connected to AC terminal 20a. The connection point of another two switching elements 40 connected in series is connected to AC terminal 20b. And the connection point of yet another two switching elements 40 connected in series is connected to 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 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 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 rectifier element 41 is, for example, a diode.

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

[0025] Each converter 20 converts the DC power supplied from the DC power source into AC power by switching the switching of each switching element 40. In this example, each converter 20 converts the DC power supplied from the DC power source into three-phase AC power by switching the switching of each switching element 40. In other words, each switching element 40 is an element that performs the conversion from DC power to 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 48.

[0027] Inductors 43a to 43c are placed between the connection points of the two series-connected switching elements 40 and the AC terminals 20a to 20c, respectively. The inductance (parallel inductance) of inductors 43a to 43c is set to the smallest possible value. This helps to suppress, for example, the increase in manufacturing costs due to inductors 43a to 43c.

[0028] The voltage detector 44 detects the magnitude of the DC voltage between a pair of DC terminals 20p and 20n, and inputs a detection signal representing 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 supply. In further terms, the voltage detector 44 detects the magnitude of the DC voltage across the charge storage element 42.

[0029] 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 representing the detection result of the AC current magnitude to the control unit 46 and the detection circuit 48. 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. Based on the transmission data received from the control device 14, the control unit 46 controls the switching of each switching element 40. In other words, based on the transmission data received from the control device 14, the control unit 46 controls the operation of the multiple switching elements 40 (converter 20) to convert DC power to AC power. The control unit 46 also transmits, for example, the detection signals of the voltage detector 44 and current detectors 45a to 45c to the control device 14 as information necessary for generating the transmission data.

[0031] The detection circuit 48 detects whether the magnitude of the DC voltage between the pair of DC terminals 20p and 20n detected by the voltage detector 44 is above the overvoltage detection level. The detection circuit 48 also detects whether the magnitude of the AC current output from the converter 20, detected by the current detectors 45a to 45c, is above the overcurrent detection level. If the detection circuit 48 detects that the voltage is above the overvoltage detection level or that the overcurrent is above the overcurrent detection level, it transmits a stop command to the control unit 46.

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

[0033] In the main circuit section 12, the configurations of the multiple converters 20 are substantially the same. The control device 14 transmits the same transmission data to each of the multiple converters 20, for example. At this time, a transmission delay is set between the control device 14 and each converter 20 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 by, for example, the length of the communication cable between the control device 14 and each converter 20.

[0034] As a result, the transmission data sent from the control device 14 to each converter 20 allows for the output of AC power of substantially the same magnitude, frequency, and phase from each converter 20 substantially simultaneously. This suppresses the occurrence of crosscurrent flow between the converters 20 even when the AC sides of multiple converters 20 are connected in parallel.

[0035] The difference between the longest and shortest transmission delays in each converter 20 is determined, for example, by the inductance values ​​of inductors 43a to 43c, the rated magnitude of the DC voltage between DC terminals 20p and 20n, and the extent to which lateral current flowing between each converter 20 is permissible. Specifically, it is assumed that a difference in the AC output voltage of each converter 20 occurs for the duration of the transmission delay difference, and the value obtained by multiplying the difference in transmission delay time by the difference in AC output voltage, and then dividing this value by the inductance values ​​of inductors 43a to 43c, is used as the design value for the resulting lateral current. The permissible range for the difference in transmission delay time is defined so that this design value of lateral current falls within the permissible range. If it is known in advance that the lengths of the communication cables between the control device 14 and each converter 20 are different, the total difference in delay time can be kept below the specified value by inserting a separate delay element in the transmission path with a short delay time.

[0036] Figure 3 is a schematic block diagram showing the control device according to the embodiment. As shown in Figure 3, the control device 14 includes an arithmetic unit 50, a dq conversion circuit 51, a current controller 52, an inverse dq conversion circuit 53, a phase generation circuit 54, an arithmetic unit 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 the phase reference θ of the AC current output from the main circuit unit 12 as input. Based on the input phase reference θ, the phase generation circuit 54 calculates the phase sinθ and cosθ of the AC current output from the main circuit unit 12, and inputs the calculated phase sinθ and cosθ to the dq conversion circuit 51 and the inverse dq conversion circuit 53.

[0038] The arithmetic unit 50 receives a detection signal that represents the magnitude of the AC current supplied from the main circuit unit 12 to the load 2, as detected by the current detectors 30a to 30c. The arithmetic unit 50 normalizes the magnitude of the AC current of the main circuit unit 12 by multiplying the input detection signal by a predetermined coefficient, 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) and phases sinθ and cosθ of the three-phase AC power into d-axis component current signals and q-axis component current signals in a coordinate system (dq coordinate) synchronized with the phase reference θ. The dq conversion circuit 51 converts the three-phase current signals into d-axis component current signals and q-axis component current signals, for example, by a Park transform. The dq conversion circuit 51 inputs the converted d-axis component current signals and q-axis component current signals to the current controller 52.

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

[0041] The current controller 52 calculates the voltage command value for the d-axis component of the AC voltage 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 d-axis component current signal and d-axis component current command value. The current controller 52 also calculates the voltage command value for the q-axis component of the AC voltage 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, based on the input q-axis component current signal and 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 conversion circuit 53.

[0042] The inverse DQ conversion circuit 53 converts the input voltage command values ​​of the D-axis component and the Q-axis component into three-phase voltage command values ​​(voltage reference) based on the input voltage command values ​​of the D-axis component, the voltage command values ​​of the Q-axis component, and the phases sinθ and cosθ. The inverse DQ conversion circuit 53 converts the voltage command values ​​of the D-axis component and the Q-axis component into three-phase voltage command values, for example, by inverse Park conversion. The inverse DQ conversion circuit 53 inputs the converted three-phase voltage command values ​​to the arithmetic unit 55.

[0043] The arithmetic unit 55 normalizes the magnitude of the three-phase voltage command values ​​by multiplying each of the input three-phase voltage command values ​​by a predetermined coefficient, and inputs the normalized three-phase voltage command values ​​to the limiters 56a to 56c.

[0044] Limiters 56a to 56c set upper and lower limits for the input voltage command value. Limiters 56a to 56c perform a process to limit the voltage command value to the upper limit if the input voltage command value is greater than or equal to the upper limit. Limiters 56a to 56c also perform a process to limit the voltage command value to the lower limit if the input voltage command value is less than or equal to the lower limit. Limiters 56a to 56c input the processed voltage command value to the control signal generation circuit 57.

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

[0046] The control signal generation circuit 57 generates three-phase control signals to control 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 generation circuit 57 generates a control signal that turns on the switching element 40 when the voltage command value is greater than the carrier signal, and turns off the switching element 40 when the voltage command value is less than the carrier signal. For example, the control signal generation circuit 57 generates a control signal (pulse signal) to control the switching of each switching element 40 of each converter 20 by PWM (Pulse Width Modulation) control. The control signal generation 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 a three-phase control signal generated by the control signal generation circuit 57, as well as a three-phase control signal with the logic inverted via a NOT gate. The three-phase control signal is used, for example, to switch the three upper switching elements 40. The three-phase control signal with the logic inverted is used, for example, to switch the three lower switching elements 40.

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

[0049] The memory unit 60 stores the six control signals input from the dead time setting circuits 58a to 58c as the current transmission data. The memory unit 60 is configured to store a predetermined number of transmission data (six control signals) up to n transmissions (a predetermined number of times; n is a natural number) from the past. Each time transmission data is input from the dead time setting circuits 58a to 58c, the memory unit 60 updates the stored transmission data up to n transmissions ago by replacing the oldest transmission data with the current transmission data.

[0050] The control device 14 generates a control signal at predetermined control cycles and stores the generated control signal as transmission data in the storage unit 60. In other words, the control device 14 generates the transmission data necessary for controlling each converter 20 at predetermined control cycles and stores the generated transmission data in the storage unit 60. The control device 14 then generates a dataset DS by adding error detection information to a predetermined number of transmission data from the current transmission data to the nth previous transmission data stored in the storage unit 60, and controls the operation of each converter 20 by transmitting the generated dataset DS to each converter 20.

[0051] Error detection information is information that enables each converter 20 to detect the occurrence of a communication error in the transmitted data. Error detection information is, for example, an error detection bit sequence for detecting the occurrence of a communication error by CRC (Cyclic Redundancy Check). However, 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. Error detection information may also be, for example, check bits used in parity checks.

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

[0053] Figure 4 is a schematic block diagram showing the control unit of each converter according to the embodiment. As shown in Figure 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 dataset DS received from the control device 14. The storage unit 70 is configured to store a predetermined number of dataset DS up to n times prior. Each time the storage unit 70 receives a dataset DS from the control device 14, it updates the stored dataset DS up to n times prior by replacing the oldest dataset DS with the currently received dataset DS.

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

[0056] In selecting the data to be transmitted for this control, the data selection unit 72 first detects whether or not a communication error has occurred in the data set DS received this time, based on the error detection information (error detection bit sequence) contained in the data set DS received this time and stored in the storage unit 70.

[0057] If the data selection unit 72 detects that no communication error has occurred, it selects the n-th previous transmission data included in the currently received dataset DS as the transmission data to be used for the current control.

[0058] On the other hand, if the data selection unit 72 detects that a communication error has occurred, it will use the error detection information contained in the previously received dataset DS stored in the storage unit 70 to determine whether or not a communication error has occurred in the previously received dataset DS.

[0059] The data selection unit 72 performs the same process as described below to select the transmission data from n previous transmissions that are included in the data set DS stored in the storage unit 70 and for which no communication errors occurred, as the transmission data to be used for the current control.

[0060] In this way, the control unit 46 detects communication errors in the dataset DS based on the error detection information contained in the dataset DS received from the control device 14, and extracts transmission data from a predetermined number of dataset DS from the currently received dataset DS to the dataset DS received a predetermined number of times ago (n times ago), based on a predetermined number of dataset DS from the currently received dataset DS to the dataset DS received a predetermined number of times ago (n times ago). In this example, the control unit 46 stores a predetermined number of dataset DS and extracts transmission data from a predetermined number of dataset DS from the stored dataset DS that did not contain any communication errors. 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 from 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] Furthermore, the detection of a dataset DS without communication errors does not necessarily have to be performed from the dataset DS received this time, as described above. The dataset DS without communication errors can be any dataset DS from the previous n datasets stored in the storage unit 70 that did not have communication errors.

[0062] The data selection unit 72 selects the transmission data to be used for the current control, and then inputs a control signal based on the selected transmission data to the AND circuit 74. For example, the data selection unit 72 inputs six control signals included in the transmission data to the AND circuit 74. For example, if the transmission data includes detection signals of AC current detected by current detectors 30a to 30c, a control signal may be generated based on the detection signal, and the generated control signal may be input to the AND circuit 74. In this case, for example, each circuit from the arithmetic unit 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 control signals to each switching element 40 when the detection circuit 48 has not detected any overvoltage or overcurrent. As a result, the control unit 46 controls the switching of each switching element 40 based on the data set DS (transmit data) received from the control device 14. The AND circuit 74 then stops inputting control signals to each switching element 40 when the detection circuit 48 has detected an overvoltage or overcurrent. This allows the converter 20 to stop converting DC power to AC power when the detection circuit 48 detects an overvoltage or overcurrent.

[0064] Furthermore, if the control unit 46 is unable to extract transmission data from a predetermined number of transmissions prior to the data set DS in which no communication errors were detected, it stops the operation of the multiple switching elements 40 to convert DC power to AC power. For example, if communication errors are detected in all of the data set DS up to n transmissions prior to the data set stored in the storage unit 70, it raises concerns that there may be a malfunction in the communication equipment. Therefore, if the data selection unit 72 is unable to detect a data set DS in which no communication errors have occurred, the control unit 46 stops the operation of the multiple switching elements 40 to convert DC power to AC power by inputting a stop command from the data selection unit 72 to the AND circuit 74.

[0065] Furthermore, if a communication error in the dataset DS is detected more than a specified number of times within a predetermined period, it is possible to be concerned that a malfunction has occurred in the communication equipment, similar to the above. Therefore, the control unit 46 performs an abnormality operation when it detects a communication error in the dataset DS more than a specified number of times within a predetermined period. The abnormality operation is, for example, an operation to stop the operation of converting DC power to AC power by the multiple switching elements 40. The abnormality operation may also be, for example, an operation to notify the user (such as the administrator of the power converter 10) of the detection of the abnormality. The abnormality operation may be any operation that can suppress equipment failure etc. due to the occurrence of a communication error. The specified number may be set to, for example, less than the number of dataset DS stored in the storage unit 70, or to be set to more than the number of dataset DS stored in the storage unit 70. The specified number may be any number.

[0066] When the control unit 46 stops the operation of the multiple switching elements 40 to convert DC power to AC power, it transmits a notification of the operation stop to the control device 14. When the control device 14 receives a notification of the operation stop from the control unit 46 of any of the multiple converters 20, it 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 operation stop of any of the multiple converters 20. However, in the main circuit unit 12 in which multiple converters 20 are connected in parallel, it is possible that the remaining converters 20 can continue to operate even if the operation of any of the multiple converters 20 stops. In such cases, the operation of the remaining converters 20 may be continued until the number of converters 20 that have stopped operating 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 by adding error detection information to a predetermined number of transmission data from the current transmission data to the transmission data from a predetermined number of times prior, and transmits the generated data set DS to each converter 20. Then, the control unit 46 of each converter 20 detects communication errors in the data set DS based on the error detection information contained in the data set DS received from the control device 14, and extracts transmission data from a predetermined number of times prior that was not detected in the data set DS from the current transmission data to the data set DS received a predetermined number of times prior, and uses the extracted transmission data from a predetermined number of times prior as the transmission data to be used for the current control, thereby controlling the conversion from DC power to AC power by the multiple switching elements 40 based on the extracted transmission data from a predetermined number of times prior.

[0068] As a result, in the power converter 10 according to this embodiment, even if a communication error occurs in any of the predetermined number of data sets DS from the currently received data set DS to the data sets DS received a predetermined number of times earlier, the operation of the multiple switching elements 40 can be appropriately controlled by the other data sets DS that were able to communicate normally. Furthermore, there is no operational delay associated with retransmission of transmitted data, such as when requesting retransmission of transmitted data from the control device 14. Therefore, the power converter 10 according to this embodiment can more effectively suppress the occurrence of unintended operation of each converter 20 due to communication errors.

[0069] Furthermore, when communication equipment is functioning normally, the frequency of communication errors is not very high. Therefore, the predetermined number of transmission data included in the dataset DS, and the predetermined number of dataset DS from the currently received dataset DS to the dataset DS received a predetermined number of times earlier, may be one or two. By setting the predetermined number to one or two, for example, it is possible to suppress the occurrence of unintended operation of each converter 20 due to communication errors, suppress the capacity required for the storage units 60 and 70, and suppress the increase in communication capacity associated with the transmission of dataset DS. On the other hand, if 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 communication errors, and to further suppress the occurrence of abnormal shutdowns of each converter 20. The predetermined number can be arbitrarily set according to the frequency of communication errors.

[0070] Furthermore, in the power converter 10 according to this embodiment, the control unit 46 stores a predetermined number of data sets DS and extracts transmission data from a predetermined number of transmissions prior to a certain number of transmissions from among the stored predetermined number of data sets DS in which no communication errors were detected. This makes it possible to appropriately extract transmission data from a predetermined number of transmissions prior to a certain number of transmissions from among the data sets DS in which no communication errors were detected.

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

[0072] Furthermore, in the power converter 10 according to this embodiment, the control unit 46 performs an abnormal operation when it detects a communication error in the data set DS more than a specified number of times within a predetermined period. This makes it possible to more effectively suppress the occurrence of unintended operations of each converter 20 due to, for example, a malfunction of the communication equipment.

[0073] Figure 5 is a schematic block diagram showing modified examples of the control units of each converter according to the embodiment. As shown in Figure 5, the modified control unit 46a has a storage unit 70a that stores transmitted data for which no communication errors were detected.

[0074] When the control unit 46a receives the dataset DS from the control device 14, it detects any communication errors in the dataset DS. If no communication errors are detected, the control unit 46a stores the transmitted data included in the received dataset DS in the storage unit 70a. On the other hand, if a communication error is detected, the control unit 46a does not store the transmitted data in the storage unit 70a.

[0075] The storage unit 70a has, for example, n storage areas corresponding to transmission data from n transmissions ago (a predetermined number of transmissions ago) to the transmission data from the previous transmission. The storage unit 70a stores each transmission data from n transmissions ago to the previous transmission in its respective storage area. Each storage area is provided with a reflected flag to check whether or not transmission data for which no communication errors were detected has been reflected. The reflected flag is set to "0" if transmission data for which no communication errors were detected has not been reflected, and to "1" if transmission data for which no communication errors were detected has been reflected.

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

[0077] The data selection unit 72a selects the data from n transmissions ago included in the currently received dataset DS as the data to be used for the current control, provided that the reflected flag in the memory area corresponding to the n transmissions ago indicates that the transmission data for which no communication errors were detected has not yet been reflected, and that no communication errors occurred in the data set DS currently received from the control device 14.

[0078] Then, the data selection unit 72a inputs a stop command to the AND circuit 74 if the reflected flag in the storage area corresponding to the nth previous transmission data indicates that the transmission data for which no communication error was detected has not been reflected, and if a communication error has occurred in the dataset DS currently received from the control device 14. This allows the operation of the multiple switching elements 40 to convert DC power to AC power to be stopped if the transmission data from a predetermined number of previous transmissions included in the dataset DS for which no communication error was detected cannot be extracted, similar to the embodiment described above.

[0079] In this way, the control unit 46a extracts a predetermined number of transmission data from the storage unit 70a or the currently received dataset DS that was included in the dataset DS for which no communication errors were detected.

[0080] If no communication errors are detected in the currently received dataset DS, the control unit 46a performs a process to store the transmitted data in the storage unit 70a, for example, after extracting transmitted data from a predetermined number of previous transmissions. In the process of storing the transmitted data in the storage unit 70a, the control unit 46a erases the transmitted data from n transmissions ago stored in the storage area, and shifts the data by one, so that the transmitted data from the 1st transmission to the (n-1)th transmission and the transmitted data from the 2nd transmission to the nth transmission. At this time, the control unit 46a also shifts the contents of the reflected flag by one, corresponding to each transmitted data.

[0081] The control unit 46a shifts the contents of each transmitted data and the reflected flag, and then stores the currently received transmitted data included in the dataset DS as the previous transmitted data in the corresponding memory area of ​​the memory unit 70a. In other words, the control unit 46a reflects the currently received transmitted data included in the dataset DS into the memory area of ​​the previous transmitted data. Then, the control unit 46a changes the reflected flag corresponding to the memory area of ​​the previous transmitted data from the unreflected state to the reflected state.

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

[0083] As a result, the process of storing the transmitted data in the storage unit 70a is performed, and when the next dataset DS is received, as described above, the transmitted data from a predetermined number of times prior included in the dataset DS in which no communication errors were detected can be extracted from the storage unit 70a or the dataset DS that was just received.

[0084] Thus, the control unit 46a has a storage unit 70a that stores transmitted data for which no communication errors were detected. When it receives a dataset DS from the control device 14, it detects communication errors in the dataset DS. If no communication errors are detected, it stores the transmitted data included in the currently received dataset DS in the storage unit 70a. If a communication error is detected, it does not store the transmitted data in the storage unit 70a. In this way, it extracts transmitted data from a predetermined number of previous transmissions included in the dataset DS for which no communication errors were detected from the storage unit 70a or the currently received dataset DS.

[0085] In this case as well, similar to the above embodiment, it is possible to appropriately extract transmission data from a predetermined number of transmissions prior to the data set DS in which no communication errors were detected. Furthermore, in a configuration in which n storage areas corresponding to the transmission data from n transmissions ago to the transmission data from one transmission ago are provided in the storage unit 70a, as shown in Figure 4, the storage capacity required in the storage unit 70a can be suppressed and the configuration of the storage unit 70a can be simplified compared to a configuration in which a predetermined number of data set DS are stored in the storage unit 70. In a configuration in which n storage areas are provided in the storage unit 70a, for example, the required storage capacity can be suppressed to that of one data set DS. Therefore, it is possible to appropriately extract transmission data from a predetermined number of transmissions prior to the data set with a simpler configuration.

[0086] This embodiment includes the following aspects. (Note 1) A main circuit unit that converts DC power into AC power corresponding to the load and supplies the converted AC power to the load, A control device that controls the operation of the main circuit section to convert DC power to AC power, Equipped with, The main circuit section 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 predetermined control cycles, and generates a dataset by adding error detection information to a predetermined number of transmission data from the currently generated transmission data to the transmission data from a predetermined number of previous transmission data, so as to enable the detection of communication errors, and transmits the dataset to the plurality of converters. The plurality of converters comprises a plurality of switching elements for converting DC power to AC power, and a control unit for controlling the conversion from DC power to AC power by the plurality of switching elements. The control unit detects communication errors in the dataset based on the error detection information contained in the dataset received from the control device, and extracts the transmission data from a predetermined number of datasets from the dataset for which no communication errors were detected, based on a predetermined number of datasets from the dataset received this time up to the dataset received a predetermined number of times previously, and uses the extracted transmission data from a predetermined number of times previously as the transmission data to be used for the current control, thereby controlling the conversion from DC power to AC power by the plurality of switching elements based on the extracted transmission data from a predetermined number of times previously.

[0087] (Note 2) The power converter according to Appendix 1, wherein the control unit stores a predetermined number of the datasets, and extracts the transmission data from a predetermined number of times prior that was included in the datasets in which no communication error was detected from among the stored predetermined number of datasets.

[0088] (Note 3) The power converter according to Appendix 1, wherein the control unit has a storage unit for storing the transmitted data in which no communication errors were detected, and when it receives the dataset from the control device, it detects the communication errors in the dataset, and if no communication errors are detected, it stores the transmitted data included in the dataset received in the storage unit, and if a communication error is detected, it does not store the transmitted data in the storage unit, thereby extracting the transmitted data from a predetermined number of previous times included in the dataset in which no communication errors were detected from the storage unit or the dataset received in the current date.

[0089] (Note 4) The power conversion device according to any one of the appendices 1 to 3, wherein the control unit stops the operation of the conversion from DC power to AC power by the plurality of switching elements when it is unable to extract the transmission data from a predetermined number of times prior to the data set in which no communication error was detected.

[0090] (Note 5) The power converter according to any one of the appendices 1 to 4, wherein the control unit performs an abnormal operation when it detects the communication error in the dataset more than a specified number of times within a predetermined period.

[0091] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0092] 2…Load, 10…Power converter, 12…Main circuit section, 14…Control device, 20…Converter, 30a~30c…Current detector, 40…Switching element, 41…Rectifier element, 42…Charge storage element, 43a~43c…Inductor, 44…Voltage detector, 45a~45c…Current detector, 46, 46a…Control unit, 48…Detection circuit, 50…Arithmetic unit, 51…DQ conversion circuit, 52…Current controller, 53…Inverse DQ conversion circuit, 54…Phase generation circuit, 55…Arithmetic unit, 56a~56c…Limiter, 57…Control signal generation circuit, 58a~58c…Dead time setting circuit, 60…Storage unit, 70, 70a…Storage unit, 72, 72a…Data selection unit, 74…AND circuit, DS…Data set

Claims

1. A plurality of switching elements and a control unit that controls the plurality of switching elements to convert DC power to AC power, wherein a plurality of converters are connected in parallel to a load to which the AC power is supplied, A control device that generates transmission data for controlling the conversion operation of the plurality of converters at predetermined control cycles, Equipped with, The control device is Each time the aforementioned transmission data is generated, a dataset is generated that includes the generated transmission data, n+1 transmission data from n transmission data generated 1 to n times prior, and error detection information for these n+1 transmission data. The generated dataset is transmitted to the multiple converters, Each of the aforementioned plurality of control units is: When the control device receives the dataset, it uses the error detection information contained in the received dataset to determine whether a communication error has occurred in the received dataset. If it is determined that no communication error has occurred, the plurality of switching elements are controlled using the transmission data generated n times earlier, which is included in the received dataset. If a communication error is detected, the system identifies a dataset received k times prior (where k is any of 1 to n) that was determined not to have a communication error based on error detection information from the dataset received 1 to n times prior. The system then uses the transmission data generated n-k times prior in this k-times-priority dataset (however, if k=n, the last generated transmission data included in the dataset received k times prior) to control the multiple switching elements. Power converter.

2. The power conversion device according to claim 1, wherein the control unit stores the dataset and identifies from the stored dataset a dataset that was received k times prior to the date in which it was determined that no communication error occurred.

3. The power converter according to claim 1, wherein the control unit has a storage unit that stores the transmitted data for which no communication errors were detected, and when it receives the dataset from the control device, it detects the communication errors in the dataset, and if no communication errors are detected, it stores the transmitted data included in the dataset received this time in the storage unit, and if a communication error is detected, it does not store the transmitted data in the storage unit, thereby extracting from the storage unit the transmitted data generated n-k times ago that was included in the dataset received k times ago when it was determined that no communication errors occurred (however, when k=n, the last transmitted data included in the dataset received k times ago).

4. The power conversion device according to claim 1, wherein the control unit stops the conversion from DC power to AC power by the plurality of switching elements when it is determined that no communication error has occurred and there is no data set received k times prior.

5. The power conversion device according to claim 1, wherein the control unit performs an abnormal operation when it detects the communication error in the dataset more than a specified number of times within a predetermined period.

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