Power conversion device, power conversion system, and control method

Abstract

A power conversion device is capable of controlling an AC output voltage of a single-phase full-bridge type unit assembly to zero voltage. The power conversion device includes a single-phase full-bridge type unit assembly and a control unit. In a case where the control unit stops switching operation of a semiconductor switching element of a positive electrode side arm or a negative electrode side arm of the unit assembly to make the AC output voltage zero voltage, the control unit controls either of the semiconductor switching elements of the positive electrode side arm and the negative electrode side arm to be in an on state and the other to be in an off state, according to a temperature of the semiconductor switching element in the unit assembly.

Description

Technical Field

[0001] Embodiments of the present invention relate to power conversion devices, power conversion systems, and control methods. Background Technology

[0002] There exist power conversion devices that connect the AC sides of multiple single-phase full-bridge unit modules in series. In such power conversion devices, to suspend the switching operation of some unit modules, sometimes the switching operation of the positive or negative arm within that unit module is suspended, making one of them conductive, thereby causing the output of the suspended unit module to become zero voltage. In such cases, the current load of the components within the unit module may sometimes become unbalanced.

[0003] If the derating is increased to protect the component from heat generated by deviations in current load, the component's performance may not be fully utilized, and its convenience may be reduced.

[0004] Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2021-069171 Summary of the Invention

[0005] The problem that the invention aims to solve The purpose of this invention is to provide a power conversion device, a power conversion system, and a control method that can improve the convenience of power conversion devices.

[0006] Methods for solving problems The power conversion device of this embodiment can control the AC output voltage of a single-phase full-bridge unit to zero voltage. The power conversion device includes a single-phase full-bridge unit and a control unit. When the AC output voltage is zero due to the suspension of the switching operation of the semiconductor switching elements on either the positive or negative arm of the unit, the control unit, based on the temperature of the semiconductor switching elements within the unit, controls either the positive or negative arm's semiconductor switching element to be in an ON state and the other to be in an OFF state. Attached Figure Description

[0007] Figure 1 This is a diagram illustrating an example of a power conversion system implemented in this way.

[0008] Figure 2A This is a diagram illustrating the configuration of the unit components in the implementation method.

[0009] Figure 2B This is a diagram illustrating the configuration of multiple cascaded unit components in an implementation method.

[0010] Figure 3AThis is a diagram illustrating an example of the configuration of the control system of the power conversion system used to explain the implementation method.

[0011] Figure 3B This is a diagram illustrating the output voltage of the unit component used to explain the implementation method.

[0012] Figure 4A This is a configuration diagram of the unit component control unit within the unit component of the implementation method.

[0013] Figure 4B This is a diagram illustrating the pause control of a unit component in an implementation method.

[0014] Figure 5 This is a diagram illustrating an example of the configuration of the control system of the power conversion system used to explain the implementation method. Detailed Implementation

[0015] Hereinafter, the power conversion device, power conversion system, and control method according to the embodiments will be described with reference to the accompanying drawings. Furthermore, in the following description, components having the same or similar functions will be labeled with the same reference numerals. Also, repeated descriptions of these components will sometimes be omitted. Additionally, for ease of explanation, illustrations of control gate wiring, etc., will sometimes be omitted from the accompanying drawings referred to below.

[0016] The power conversion system of the embodiment forms a multi-unit power conversion system. The multi-unit power conversion system has multiple unit components. Here, we first define "positive P" and "negative N" within the multiple unit components. "Positive P" refers to the part within the unit component that becomes positively potential when the power conversion system 1 is operating. "Negative N" refers to the part within the unit component that becomes negatively potential when the power conversion system 1 is operating.

[0017] Reference Figures 1 to 5 The power conversion system 1 of the implementation method will be described.

[0018] Figure 1 This is a diagram illustrating an example of a power conversion system 1 according to an implementation method. Figure 1 In this diagram, a single line is used to represent the circuit system, and diagrams of switches and other components are omitted.

[0019] The power supply side of the power conversion system 1 is connected to the AC power source 2, for example, via a circuit breaker. The power conversion system 1 converts the AC power supplied from the AC power source 2 into DC power, converts the converted DC power into AC power of the desired frequency and voltage, and supplies it to the motor 3. The motor 3 is, for example, a three-phase induction motor, but is not limited to this.

[0020] In this embodiment, an example of a power conversion system 1 having multiple unit components 6s will be described. The power conversion system 1 includes, for example, an input transformer 5, multiple unit components 6s, a control device 7, and a current sensor AM.

[0021] AC power is supplied from AC power source 2 to input transformer 5. Input transformer 5 transforms the voltage (primary voltage) of the AC power supplied from AC power source 2 to the desired secondary voltage, and supplies the secondary voltage AC power to multiple unit components 6s respectively. Input transformer 5 has a primary winding and multiple sets of mutually insulated windings (secondary windings). The primary winding and secondary windings are also insulated from each other.

[0022] Multiple unit components 6s include, for example, three unit components 6A1, 6A2, and 6A3 (referred to as U1, U2, and U3 in the figure) for the first phase of load, three unit components 6B1, 6B1 (referred to as V1, V2, and V3 in the figure), and 6B3 for the second phase of load, and three unit components 6C1, 6C2, and 6C3 (referred to as W1, W2, and W3 in the figure) for the third phase of load. Unit components 6A1, 6A2, 6A3, 6B1, 6B1, 6B3, 6C1, 6C2, and 6C3 have the same circuit configuration and are referred to simply as unit component 6 without distinction. For example, multiple unit components 6s are an example of multiple substations, and unit component 6 is an example of a substation. Each unit component 6 converts the three-phase AC power supplied from the secondary winding of the input transformer 5 into DC power, converts the converted DC power into AC power of the desired frequency and voltage, and outputs it.

[0023] For example, the first group of the secondary side of input transformer 5 is connected to the input of unit component 6A1. The second group of the secondary side of input transformer 5 is connected to the input of unit component V1. The third group of the secondary side of input transformer 5 is connected to the input of unit component W1. The fourth group of the secondary side of input transformer 5 is connected to the input of unit component 6A2. The fifth group of the secondary side of input transformer 5 is connected to the input of unit component 6B2. The sixth group of the secondary side of input transformer 5 is connected to the input of unit component 6C2. The seventh group of the secondary side of input transformer 5 is connected to the input of unit component 6A3. The eighth group of the secondary side of input transformer 5 is connected to the input of unit component 6B3. The ninth group of the secondary side of input transformer 5 is connected to the input of unit component 6C3.

[0024] In this embodiment, the outputs of unit components 6A1, 6A2, and 6A3 are connected in series in the order described. The output terminal of unit component 6A3 that is not connected to unit component 6A2 is connected to the first phase (U phase) of the motor 3. The output terminal of unit component 6A1 that is not connected to unit component 6A2 is connected to the neutral point. In this embodiment, the outputs of unit components 6B1, 6B2, and 6B3 are connected in series in the order described. The output terminal of unit component 6B3 that is not connected to unit component 6B2 is connected to the second phase (V phase) of the motor 3. The output terminal of unit component 6B1 that is not connected to unit component 6B2 is connected to the neutral point. In this embodiment, the outputs of unit components 6C1, 6B2, and 6B3 are connected in series in the order described. The output terminal of unit component 6C3 that is not connected to unit component 6C2 is connected to the third phase (W phase) of the motor 3. The output terminal of unit component 6C1 that is not connected to unit component 6C2 is connected to the neutral point. Thus, the power conversion system 1 can supply a large capacity of AC power to the motor 3.

[0025] Current sensors AM1 and AM2 are examples of current sensor AM, which detect the load current (phase current) flowing between the inverter 13 (Fig. 2) and the motor 3 in the power conversion system 1. Furthermore, if the system is configured to generate an estimated value of the load current, the current sensor AM can be omitted.

[0026] Temperature sensors are installed on the heat sinks and other components of each unit 6.

[0027] The control device 7 is an example of a higher-level control device that controls or protects each unit component 6. The control device 7 includes, for example, a storage unit 71, an operation control unit 72, a control state estimation unit 73, and a braking control unit 74.

[0028] The storage unit 71 stores various data related to the control of the multiple unit components 6s. These data include, for example, the number of stages of the daisy-chained unit components 6, the received and transmitted values ​​of the control signal α, and the operating status of each unit component 6.

[0029] The operation control unit 72 generates data based on the data stored in the storage unit 71 for controlling the semiconductor switching elements 13S included in each unit component 6. Figure 3A The operation control unit 72 controls each unit component 6 by sending the generated control signal α to each unit component 6. The operation control unit 72 may also acquire a signal indicating the control state of the motor 3 (e.g., a feedback signal of the rotational speed) and control each unit component 6 based on the feedback signal. In addition, the control device 7 acquires the control command signal of the motor 3 from other devices and controls each unit component 6 based on the control command signal.

[0030] The control state estimation unit 73 estimates the operating state of the power conversion system 1 based on the received state of the control signal α and the information contained in the received control signal α. Details will be described later.

[0031] The braking control unit 74 controls each unit component 6 based on the estimated operating state of the power conversion system 1, and controls each unit in a manner that brakes the motor 3 based on the control state.

[0032] Next, unit component 6 will be described.

[0033] Figure 2A This is a structural diagram of unit component 6 in the implementation method. Figure 2B This is a diagram showing the configuration of multiple cascaded unit components 6s in the implementation method.

[0034] Unit 6 may include, for example, a single-phase unit inverter 6IV and a unit control unit 6CUC.

[0035] The single-phase unit inverter 6IV is, for example, a single-phase AC output type inverter. The single-phase unit inverter 6IV includes, for example, a diode converter 12, an inverter 13, a smoothing capacitor 14, and resistors 15 and 16. The DC output of the diode converter 12 and the DC input of the inverter 13 are electrically connected to each other via a DC link, with their positive (P) terminals and negative (N) terminals electrically connected to each other. The smoothing capacitor 14 is disposed on the DC link, and its terminals are electrically connected to the positive and negative terminals of the DC link.

[0036] In the following description, unit component 6A1 is illustrated, and its connection to the outside is shown as an example. The other unit components 6 are described in the same way.

[0037] The diode converter 12 is a three-phase AC input type forward converter, and its input section is electrically connected to one group of the secondary side of the input transformer 5. The diode converter 12 converts the AC power input from the input transformer 5 into DC power by rectifying the AC. The smoothing capacitor 14 smooths the converted DC voltage.

[0038] Inverter 13 is an example of a single-phase AC output type power conversion device. Inverter 13 includes, for example, a semiconductor switching element 13S that converts DC power from the DC side to AC power, and a reverse-connected diode 13D connected in anti-parallel to the semiconductor switching element 13S. The semiconductor switching element 13S is an example of a semiconductor switching element. Inverter 13 is connected in series with the DC output of diode converter 12 on the DC side and with the output of motor 3 or other unit component 6 on the AC side. Inverter 13 outputs the converted AC power to the first phase of motor 3, for example.

[0039] Temperature sensors 13TSP and 13TSN are installed on the heat sink of the inverter 13. For example, temperature sensor 13TSP is positioned at a location where the temperature of the positive electrode side arm 13PA can be easily detected. Temperature sensor 13TSN is positioned at a location where the temperature of the negative electrode side arm 13NA can be easily detected.

[0040] Alternatively, a resistor (not shown) may be provided to discharge the charge accumulated in the smoothing capacitor 14.

[0041] The unit component control unit 6CUC generates signals to control the semiconductor switching elements constituting the diode converter 12 and the inverter 13 based on the control from the control device 7. The unit component control unit 6CUC uses the generated signals to control the semiconductor switching elements constituting the diode converter 12 and the inverter 13.

[0042] The unit component control unit 6CUC collects DC voltage Vdc, P-side component temperature Tp and N-side component temperature Tn detected by temperature sensors 13TSP and 13TSN, and outputs them through communication.

[0043] For example, inverter 13 omits detailed internal wiring but includes one or more semiconductor switching elements that convert power through switching operations. These semiconductor switching elements can be IGBTs (Insulated Gate Bipolar Transistors), IEGTs (Injection Enhanced Gate Transistors), MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), etc. Inverter 13 functions as an inverter that generates AC power through control, cooperating with other inverters connected to its output to allow current to flow through the windings of motor 3.

[0044] Figure 3A This is a structural diagram of unit component 6 in the implementation method.

[0045] Unit component 6 has semiconductor switching elements GAP and GBP on the positive electrode side and semiconductor switching elements GA_N and GB_N on the negative electrode side 13NA. Semiconductor switching elements GA_P and GA_N form a first branch, and semiconductor switching elements GB_P and GB_N form a second branch.

[0046] Each semiconductor switching element within unit component 6 is configured as a single-phase full-bridge type. Furthermore, the aforementioned semiconductor switching elements GAP, GBP, GA_N, and GB_N are examples of the aforementioned semiconductor switching element 13S.

[0047] The semiconductor switching elements shown in the figure are IGBTs, but are not limited to them.

[0048] Figure 3B This is a diagram illustrating the output voltage of unit component 6 in the implementation method.

[0049] By turning on each pair of semiconductor switching elements in unit component 6, the output voltage of unit component 6 can be changed. For example, by turning on semiconductor switching element GA_P in the positive arm 13PA and semiconductor switching element GB_N in the negative arm 13NA, the output voltage of unit component 6 becomes positive. By turning on semiconductor switching element GA_N in the negative arm 13NA and semiconductor switching element GB_P in the positive arm 13PA, the output voltage of unit component 6 becomes negative. Alternatively, by turning on both semiconductor switching elements GA_P and GB_P in the positive arm 13PA, or both semiconductor switching elements GA_N and GB_N in the negative arm 13NA, the output voltage of unit component 6 becomes zero.

[0050] There are two methods for controlling the semiconductor switching element when unit component 6 is in a stopped state.

[0051] As described above, by making the two semiconductor switching elements GA_P and GB_P of the positive electrode side arm 13PA, or the two semiconductor switching elements GA_N and GB_N of the negative electrode side arm 13NA, both in the ON state, the unit component 6 can be made into the OFF state.

[0052] For example, when the unit assembly control unit 6CUC recognizes that a specified condition has been met, it can control the semiconductor switching elements GA_P and GB_P on the positive electrode side arm 13PA, or the semiconductor switching elements GA_N and GB_N on the negative electrode side arm 13NA, to be simultaneously in the ON state. Thus, the unit assembly 6 can be brought to a OFF state under control from the unit assembly control unit 6CUC.

[0053] However, if current flows even when unit component 6 is set to the off state, heat will be generated due to the loss of semiconductor switching elements along the current flow path. The longer the energizing time, the higher the temperature caused by the heat will rise.

[0054] Figure 4A This is a configuration diagram of the unit component control unit 6CUC within the unit component 6 of the embodiment. Figure 4B This is a diagram illustrating the pause control of unit component 6 in the implementation method.

[0055] like Figure 4AAs shown, the unit component control unit 61CUC of the unit component 61 has a control signal α receiving port αI as a port for receiving signals from the outside, and a control signal α sending port αO and a gate pulse output port GPO as ports for outputting signals to the outside.

[0056] The unit component control unit 61CUC also includes processing modules 101, 102, 111 to 114.

[0057] The control signal α from the preceding unit component 6 or control device 7 is supplied to the control signal α receiving port αI. The control signal α receiving port αI is connected to the input of processing modules 101, 111, and 112.

[0058] Processing module 101 extracts control instructions from control signal α and calculates the control quantity that is used as the control target. The output signal of the control quantity is converted into a binary pulse through PWM control, etc. Processing module 102 (GB) limits the output of the gate pulse corresponding to the pulse output by processing module 101 through the PGON and NGON signals output by processing module 114.

[0059] For example, when the logic of the PGON signal is logic 1 and the logic of the NGON signal is logic 0, the processing module 102 fixes the output of the gate pulse for the positive arm to a logic that turns on the element of the positive arm, and restricts the output of the gate pulse for the negative arm. When the logic of the PGON signal is logic 0 and the logic of the NGON signal is logic 1, the processing module 102 fixes the output of the gate pulse for the negative arm to a logic that turns on the element of the negative arm, and restricts the output of the gate pulse for the positive arm. In other cases, the processing module 102 outputs a gate pulse corresponding to the output signal of the processing module 101.

[0060] Processing module 111 detects the supply of control signal α. When the supply of control signal α is detected, processing module 111 outputs logic 0; when the supply of control signal α is interrupted for a specified time, it outputs logic 1. The output of processing module 111 is connected to the input of processing module 114.

[0061] Processing module 112 extracts CELL_NUM and pause level instructions from control signal α. Processing module 112 generates an updated CELL_NUM by incrementing CELL_NUM by 1, and outputs the signal in control signal α that has replaced CELL_NUM to processing module 113.

[0062] The pause level instruction specifies the signal of a unit component 6 among multiple unit components 6s that is set to a pause state, in units of levels. When the pause level instruction is composed of two-valued logic, it can be predetermined that the logic value is either an odd level or an even level.

[0063] For example, processing module 112 determines the value of CELL_NUM based on the pause level instruction as described above. For example, it generates a logic 1 if the pause level instruction is even and the value of CELL_NUM is even, and generates a logic 0 otherwise. Processing module 112 supplies the result of the pause level instruction determination to processing module 114.

[0064] Processing module 113 obtains the P-side element temperature Tp and N-side element temperature Tn from temperature sensors 13TSp and 13TSN respectively, generates a PN selection command, and outputs it to processing module 114. Processing module 113 appends the P-side element temperature Tp, the N-side element temperature Tn, and the PN selection command to the control signal α and outputs it to the next stage.

[0065] Processing module 114 outputs logic 1 as the initial value. When logic 1 is supplied from both processing modules 111 and 112, processing module 114 generates and outputs signals PGON and NGON based on the PN selection instruction from processing module 113. Processing module 114 outputs signals PGON and NGON after a specified delay.

[0066] like Figure 4B As shown, processing module 113 generates a PN selection command based on the temperature difference between the P-side element temperature Tp and the N-side element temperature Tn. When the N-side element temperature Tn is lower than the P-side element temperature Tp, processing module 113 generates a PN selection command to make the negative electrode arm conductive. When the N-side element temperature Tn is higher than the P-side element temperature Tp, processing module 113 generates a PN selection command to make the positive electrode arm conductive.

[0067] The processing module 114 receives the PN selection command and ensures sufficient time during the switching of the PN selection command to prevent excessive current from flowing through the unit component 6. Furthermore, the processing module 114 sets a delay time to suppress the switching frequency, preventing frequent switching based on the determination result of the PN selection command. This suppresses fluctuations in the PN selection command when the temperature difference between the P-side component temperature Tp and the N-side component temperature Tn is small.

[0068] (Variations of processing module 113 and processing module 114) Processing module 113 can determine the logic value of the PN selection instruction based on the detected or estimated temperature value. The P-side element temperature Tp and N-side element temperature Tn are examples of detected or estimated temperature values. For instance, the P-side element temperature Tp is an estimated or detected temperature value of the semiconductor switching element in the P-side arm. The N-side element temperature Tp is an estimated or detected temperature value of the semiconductor switching element in the N-side arm.

[0069] The output PN selection instruction takes a logical value.

[0070] For example, when the relationship between the P-side element temperature Tp and the N-side element temperature Tn is such that, for example, the P-side element temperature Tp is higher than the N-side element temperature Tn, the processing module 113 sets the PN selection instruction to a logic value for turning on the semiconductor switching element of the N-side arm.

[0071] When the relationship between the P-side element temperature Tp and the N-side element temperature Tn is, for example, that the P-side element temperature Tp is lower than the N-side element temperature Tn, the processing module 113 sets the PN selection instruction to a logic value for turning on the semiconductor switching element of the P-side arm.

[0072] Based on the logic value of the PN selection instruction, processing module 114 generates gate control signals (P-side gate on signal) for the semiconductor switching element of the P-side arm and gate control signals (N-side gate on signal) for the semiconductor switching element of the N-side arm. Processing module 114 has a pulse delay function that extends the pulse width of the PN selection instruction, ensuring that it does not generate P-side gate on signals and N-side gate on signals shorter than the specified time defined by the pulse delay function. Furthermore, neither the P-side gate on signal nor the N-side gate on signal becomes a logic value for a specified on-state.

[0073] Furthermore, for the sake of simplicity, in the following description, the various processes performed by the control unit 6CUC of each unit component will sometimes be described as the processes of each unit component 6.

[0074] The control device 7 includes: a control signal α output port for outputting control signal α to unit component 63 (second substation) in each unit component 6 for controlling the operating state of each unit component 6; and a control signal α receiving port for receiving control signal α from unit component 61 (first substation) in each unit component 6.

[0075] Explanations regarding these will be provided later.

[0076] Example of the configuration of power conversion system 1 in the implementation method: Reference Figure 5 An example of the configuration of the control system of power conversion system 1 will be described.

[0077] Figure 5 This is a diagram illustrating an example of the configuration of the control system of the power conversion system 1 in the embodiment.

[0078] exist Figure 5 The system shown includes a control device 7 (command board for unit control), three unit components 6 (61, 62, 63), and a daisy-chain communication path 8 for transmitting signals to the control system. The control device 7 is sometimes referred to as the master station, and the unit components 6 as slave stations. The range shown here exemplifies the range corresponding to U of the motor 3, differentiated according to each phase of the motor 3.

[0079] The daisy-chain communication path 8 connects the control device 7 and multiple unit components 6s. Reference numerals 81 to 84 are examples of the connection media constituting the daisy-chain communication path 8. In this embodiment, the connection media 81 to 84 are mutually insulated. The daisy-chain communication path 8 is configured to enable communication in at least one direction.

[0080] For example, the daisy-chain communication path 8 is configured to send at least control signal α.

[0081] For example, the control signal α output port of control device 7 is connected to one end of connection medium 81, and the other end of connection medium 81 is connected to the control signal α receiving port of unit component 63. The control signal α output port of unit component 63 is connected to one end of connection medium 82, and the other end of connection medium 82 is connected to the control signal α receiving port of unit component 62. The control signal α output port of unit component 62 is connected to one end of connection medium 83, and the other end of connection medium 83 is connected to the control signal α receiving port of unit component 61. The control signal α output port of unit component 61 is connected to one end of connection medium 84, and the other end of connection medium 84 is connected to the control signal α receiving port of control device 7.

[0082] As described above, the signals used for communication via daisy-chain communication path 8 include control signal α. This control signal α contains control signals for controlling the power conversion devices of each unit component 6.

[0083] Before explaining the details of the control using daisy-chain communication path 8, let's first explain the function of unit component 6 and the control of motor 3.

[0084] As described above, the multiple unit modules 6s are configured such that a single-phase unit inverter 6IV (power conversion device) within each unit module 6 is connected to a motor 3 (load device) to supply power to the motor 3. The multiple unit modules 6s switch between "operation" for supplying power from the power conversion device and "stop" for interrupting the power supply from a specific unit module 6 by setting its output voltage to 0, thereby supplying power to the motor 3 (load device). Even when the output voltage of a specific unit module 6 is set to 0, stopping the power supply from that unit module 6, power is still supplied to the motor 3 (load device) from unit modules 6 other than the specific unit module 6.

[0085] As described above, there are two methods for controlling the semiconductor switching elements when each unit component 6 is in a stopped state. However, if the control device 7 specifies control for each unit component 6 to be in a stopped state separately, the control becomes complex. Therefore, this embodiment proposes a method to simplify the above control. Various scenarios that can be applied to this control are illustrated and described in turn.

[0086] Scene 1: Each unit component control unit 6CUC (control unit) can control the operating state of the unit component 6 based on instructions from the control device 7 of the upper device, the state of the unit component 6, or both instructions from the upper device and the state of the unit component 6, in a way that makes the temperature rise of the semiconductor switching elements in the unit component 6 uniform.

[0087] For example, the control unit 6CUC of each unit component suspends the switching operation of the semiconductor switching element of the positive side arm 13PA or the negative side arm 13NA of this unit component 6, so that the AC output voltage is zero.

[0088] In this case, each unit component control unit 6CUC (control unit) can control either the positive electrode side arm 13PA or the negative electrode side arm 13NA to be in the ON state and the other to be in the OFF state, based on the temperature of the semiconductor switching element within the unit component 6.

[0089] Therefore, each unit component control unit 6CUC (control unit) can output zero voltage from its own unit component 6.

[0090] Furthermore, the state of this unit component 6 can be determined by any part or all of the following: the temperature of the semiconductor switching element, the magnitude of the conduction current of the semiconductor switching element, the polarity of the conduction current, and the continuous time of the on-state of the semiconductor switching element.

[0091] Scene 2: Each unit component control unit 6CUC can switch one semiconductor switching element to the off state and switch the other semiconductor switching element to the on state if the continuous time of the on state of the semiconductor switching element of one of the positive electrode side arm 13PA and the negative electrode side arm 13NA exceeds a predetermined time.

[0092] Scene 3: Each unit component control unit 6CUC can switch the semiconductor switching element in the on state to the off state and switch the semiconductor switching element in the other state to the on state when the temperature of the semiconductor switching element in the positive electrode side arm 13PA and the negative electrode side arm 13NA in the on state is higher than the temperature of the semiconductor switching element in the other state.

[0093] Scene 4: Each unit component control unit 6CUC can delay the switching between the on and off states of a semiconductor switching element that is in the on state and the semiconductor switching element of the other party by a specified time.

[0094] Next, we will explain the details of controlling the daisy chain communication path 8.

[0095] Multiple unit components 6s receive control commands from the master station and the power conversion devices directly or indirectly. In this embodiment, each unit component 6 is daisy-chained together via a wired communication path (daisy-chain communication path 8). The power conversion system 1 utilizes the daisy-chain communication path 8 for communication between the master station and the unit components 6, and between the unit components 6 themselves. The power conversion system 1 uses this communication to control the power conversion devices within each unit component 6, thereby supplying power to load devices respectively connected to the power conversion devices within each unit component 6. During power supply, the power conversion system 1 switches between "operation" for supplying power from the power conversion devices and "stop" for interrupting the power supply.

[0096] (Control was achieved using control signal α) The control device 7 and each unit component 6 use the daisy-chain communication path 8 to send control signals α to each unit component 6.

[0097] For ease of explanation, the unit that directly receives the control signal α output by the control device 7 will be referred to as the top-level unit component, and the unit that sends the control signal α back to the control device 7 will be referred to as the bottom-level unit component. The bottom-level unit component is an example of the first substation, and the top-level unit component is an example of the second substation. Figure 5 The top-level unit component is unit component 63, and the bottom-level unit component is unit component 61.

[0098] (Control and status monitoring using control signal α) The self-number (hereinafter referred to as MYNUM) identified by the unit component 6 on the transmitting side of the control signal α in a pair of unit components 6 (substations) facing each other across each wiring interval is defined as the cell level count CELL_NUM (hereinafter referred to as CELL_NUM). The unit component 6 on the transmitting side of the control signal α includes this CELL_NUM in the control signal α.

[0099] The control signal α includes the aforementioned CELL_NUM value as its data. Each unit component 6 determines the value obtained by adding 1 to the CELL_NUM of the control signal α received from the superior (CELL_NUM++) as identification information for relatively identifying its own position, and sends its own MYNUM as the CELL_NUM for the subordinate. The value of CELL_NUM is equivalent to the number of times the control signal α is relayed by the unit component 6. The above relationship is shown in the following equations (1) and (2). In these equations, represents setting the result of the operation on the right as the value of the variable on the left.

[0100] MYNUM=CELL_NUM+1...(1) CELL_NUM=MYNUM...(2) According to the above-described embodiment, the power conversion device can control the AC output voltage of a single-phase full-bridge unit to zero voltage. The power conversion device includes a single-phase full-bridge unit and a control unit. When the AC output voltage is zero due to the suspension of the switching operation of the semiconductor switching element on the positive arm 13PA or the negative arm 13NA of the unit, the control unit controls either the positive arm 13PA or the negative arm 13NA to be in an ON state and the other to be in an OFF state based on the temperature of the semiconductor switching element within the unit. This improves the convenience of the power conversion device.

[0101] Furthermore, in the power conversion system of the power conversion device having the above-described embodiments, the power conversion device comprising multiple unit components 6s is configured as a multilevel inverter, which has a single-phase circuit consisting of multiple single-phase full-bridge type unit components 6s connected in series according to the number of phases.

[0102] Each unit component 6 is associated with its respective unit component control unit 6CUC. Each unit component control unit 6CUC receives instructions from the control device 7 (host device).

[0103] For example, the control signal transmission system of each unit component control unit 6CUC daisy-chains each unit component group formed by connecting multiple unit components 6s in series on the AC side. In this case, each unit component control unit 6CUC determines the unit component 6 that is to be suspended from among the multiple unit components 6s according to the position configured within the daisy chain connection and the instructions from the control device 7.

[0104] Each unit component control unit 6CUC determines the unit component 6 that is to be suspended from multiple unit components 6s based on whether it meets the conditions specified by the instruction characters from the control device 7.

[0105] According to at least one embodiment described above, a power conversion device can control the AC output voltage of a single-phase full-bridge unit to zero voltage. The power conversion device includes a single-phase full-bridge unit and a control unit. When the AC output voltage is zero due to the suspension of the switching operation of the semiconductor switching elements on either the positive or negative arm of the unit, the control unit, based on the temperature of the semiconductor switching elements within the unit, controls either the positive or negative arm's semiconductor switching element to be in an ON state and the other to be in an OFF state. This improves the convenience of the power conversion device.

[0106] In the power conversion system 1 described above, some or all of the functional units of the control device 7 and the unit component control unit 6CUC are implemented, for example, by a computer processor (hardware processor) executing a program (computer program, software component) stored in the computer's storage unit (memory, etc.). Alternatively, some or all of the functional units of the control device 7 and the unit component control unit 6CUC can be implemented, for example, by hardware such as LSI (Large Scale Integration), ASIC (Application Specific Integrated Circuit), or FPGA (Field-Programmable Gate Array), or by a combination of software functional units and hardware.

[0107] Several embodiments have been described above, but the configuration of the embodiments is not limited to the examples described above. For example, the configurations of each embodiment can be combined with each other and can be applied to the configuration parts that have been omitted from the description. For example, the description of the first phase, i.e., the U phase, of the motor 3 described above can be applied to the V phase of the second phase and the W phase of the third phase of the motor 3.

[0108] Several embodiments of the present invention have been described, but these embodiments are merely illustrative and not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, and are included within the scope of the invention as described in the claims and its equivalents.

[0109] In addition, the daisy-chain communication path 8 can be a communication path based on electrical signals or a communication path based on optical signals.

[0110] (Postscript) This embodiment can be configured as follows.

[0111] (1) One embodiment is a power conversion device capable of controlling the AC output voltage of a single-phase full-bridge unit component to zero voltage, comprising: Single-phase full-bridge unit components; and The control unit, when suspending the switching action of the semiconductor switching element of the positive or negative arm of the unit assembly to make the AC output voltage zero, controls either the semiconductor switching element of the positive arm or the negative arm to be in an on state and controls the other to be in an off state according to the temperature of the semiconductor switching element in the unit assembly.

[0112] (2) In the power conversion device described in (1) above, it can be, The control unit is, Based on instructions from a higher-level device or the state of the unit component, or both, either of the semiconductor switching elements of the positive and negative terminals is controlled to be in the ON state in order to output zero voltage, so that the temperature rise of the semiconductor switching elements is equal.

[0113] (3) In the power conversion device described in (1) above, it can be, The state of this unit component is any one of the following: the temperature of the semiconductor switching element, the magnitude of the conduction current of the semiconductor switching element, the polarity of the conduction current, and the continuous time of the on-state of the semiconductor switching element.

[0114] (4) In the power conversion device described in (1) above, it can be, The control unit is, If the continuous time of the on state of the semiconductor switching element of one of the positive electrode side arm and the negative electrode side arm exceeds a predetermined time, the semiconductor switching element of the one side is switched to the off state, and the semiconductor switching element of the other side is switched to the on state.

[0115] (5) In the power conversion device described in (1) above, it can be, The control unit is, When the temperature of one of the semiconductor switching elements in the positive electrode arm and the negative electrode arm that is in the ON state is higher than the temperature of the other semiconductor switching element, the semiconductor switching element of the one side is switched to the OFF state, and the semiconductor switching element of the other side is switched to the ON state.

[0116] (6) In the power conversion device described in (1) above, it can be, The control unit is, The timing delay for switching the on and off states of the semiconductor switching elements of one party and the other party is specified by a predetermined time, thereby suppressing the switching frequency.

[0117] (7) One embodiment of the power conversion system may include the power conversion device described in (1) above. The power conversion device is configured as a multi-level inverter, which has a single-phase circuit consisting of multiple single-phase full-bridge unit components connected in series, depending on the number of phases. Each unit component is associated with a corresponding control section that controls that unit component. Each control unit receives instructions from the host device.

[0118] (8) In the power conversion system described in (7) above, it can be, The control units are, When the control signal transmission system of each control unit performs a daisy-chain connection on each group of unit components formed by the AC side of the plurality of unit components connected in series, the unit component that is to be suspended is determined from the plurality of unit components according to the position of the configuration within the daisy-chain connection and the instructions from the host device.

[0119] (9) In the power conversion system described in (7) above, it can be, The control units are, The unit component that becomes the object of the pause is determined from the plurality of unit components based on whether it meets the conditions specified by the instruction characters from the host device.

[0120] Explanation of reference numerals in the attached figures 1……Power conversion system, 3……Motor, 6……Unit component (power conversion device), 6s……Multiple unit components, IV……Single-phase unit inverter (power conversion device), 6CUC……Unit component control unit (control unit), 7……Control device (supervisor device), 8……Daiwild communication path.

Claims

1. A power conversion device capable of controlling the AC output voltage of a single-phase full-bridge unit component to zero voltage, comprising: Single-phase full-bridge unit components; and The control unit, when suspending the switching action of the semiconductor switching element of the positive or negative arm of the unit assembly to make the AC output voltage zero, controls either the semiconductor switching element of the positive arm or the negative arm to be in an on state and controls the other to be in an off state according to the temperature of the semiconductor switching element in the unit assembly.

2. The power conversion device according to claim 1, wherein, The control unit is, Based on instructions from a higher-level device or the state of the unit component, or both, either of the semiconductor switching elements of the positive and negative terminals is controlled to be in the ON state in order to output zero voltage, so that the temperature rise of the semiconductor switching elements is equal.

3. The power conversion device according to claim 1, wherein, The state of this unit component is any one of the following: the temperature of the semiconductor switching element, the magnitude of the conduction current of the semiconductor switching element, the polarity of the conduction current, and the continuous time of the on-state of the semiconductor switching element.

4. The power conversion device according to claim 1, wherein, The control unit is, If the continuous time of the on state of the semiconductor switching element of one of the positive electrode side arm and the negative electrode side arm exceeds a predetermined time, the semiconductor switching element of the one side is switched to the off state, and the semiconductor switching element of the other side is switched to the on state.

5. The power conversion device according to claim 1, wherein, The control unit is, When the temperature of one of the semiconductor switching elements in the positive electrode arm and the negative electrode arm that is in the ON state is higher than the temperature of the other semiconductor switching element, the semiconductor switching element of the one side is switched to the OFF state, and the semiconductor switching element of the other side is switched to the ON state.

6. The power conversion device according to claim 5, wherein, The control unit is, The timing delay for switching the on and off states of the semiconductor switching elements of one party and the other party is specified by a predetermined time, thereby suppressing the switching frequency.

7. A power conversion system, Including the power conversion device as described in claim 1, The power conversion device is configured as a multi-level inverter, which has a single-phase circuit consisting of multiple single-phase full-bridge unit components connected in series, depending on the number of phases. Each unit component is associated with a corresponding control section that controls that unit component. Each control unit receives instructions from the host device.

8. The power conversion system according to claim 7, wherein, The control units are, When the control signal transmission system of each control unit performs a daisy-chain connection on each group of unit components formed by the AC side of the plurality of unit components connected in series, the unit component that is to be suspended is determined from the plurality of unit components according to the position of the configuration within the daisy-chain connection and the instructions from the host device.

9. The power conversion system according to claim 7, wherein, The control units are, The unit component that becomes the object of the pause is determined from the plurality of unit components based on whether it meets the conditions specified by the instruction characters from the host device.

10. A control method for a power conversion device capable of controlling the AC output voltage of a single-phase full-bridge unit component to zero voltage, comprising: When the switching action of the semiconductor switching element of the positive or negative arm of the single-phase full-bridge unit is suspended and the AC output voltage is zero, the semiconductor switching element of the positive arm and the negative arm is controlled to be in the ON state and the other is controlled to be in the OFF state according to the temperature of the semiconductor switching element in the unit.

11. The control method according to claim 10, wherein, include: Based on instructions from a higher-level device or the state of the unit component, or both, either of the semiconductor switching elements of the positive and negative terminals is controlled to be in the ON state in order to output zero voltage, so that the temperature rise of the semiconductor switching elements is equal.

12. The control method according to claim 10, wherein, The state of this unit component is any one of the following: the temperature of the semiconductor switching element, the magnitude of the conduction current of the semiconductor switching element, the polarity of the conduction current, and the continuous time of the on-state of the semiconductor switching element.

13. The control method according to claim 10, wherein, include: If the continuous time of the on state of the semiconductor switching element of one of the positive electrode side arm and the negative electrode side arm exceeds a predetermined time, the semiconductor switching element of the one side is switched to the off state, and the semiconductor switching element of the other side is switched to the on state.

14. The control method according to claim 10, wherein, include: When the temperature of one of the semiconductor switching elements in the positive electrode arm and the negative electrode arm that is in the ON state is higher than the temperature of the other semiconductor switching element, the semiconductor switching element of the one side is switched to the OFF state, and the semiconductor switching element of the other side is switched to the ON state.

15. The control method according to claim 14, wherein, include: A predetermined time delay is used to switch the on and off states of the semiconductor switching elements of the other party.

16. The control method according to claim 10, wherein, include: The power conversion device is configured as a multilevel inverter, which has a single-phase circuit consisting of multiple single-phase full-bridge unit components connected in series, depending on the number of phases. Each unit component is associated with a corresponding control section that controls that unit component. Each control unit receives instructions from the host device.

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