Power converter, method and system for wave-by-wave current limiting

Abstract

A power converter, a wave-by-wave current limiting method and system are disclosed, relating to the field of power electronics technology. The power converter includes a control circuit and a power conversion circuit. The power conversion circuit is electrically connected to the control circuit. The control circuit is used to perform wave-by-wave current limiting control on the power conversion circuit when the current at the off-grid port reaches the wave-by-wave current limiting threshold and the voltage at the off-grid port is overloaded; and to control the power conversion circuit to stop operating when the current at the off-grid port reaches the wave-by-wave current limiting threshold and the off-grid port is short-circuited. Using this scheme, the thermal stress on the power switching devices can be reduced during wave-by-wave current limiting in short-circuit scenarios, ensuring the reliable operation of the power converter.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, specifically to a power converter, a wave-by-wave current limiting method and system. Background Technology

[0002] The core of Cycle By Cycle (CBC) current limiting is to independently monitor the current in each Pulse Width Modulation (PWM) cycle. If the current exceeds the current threshold due to overload or short circuit, the PWM drive is immediately shut off and then attempted to be restored in the next cycle. This precisely limits the current and protects the power devices.

[0003] In a short-circuit triggered current-limiting scenario, the inductor current of the power converter rises rapidly when short-circuited away from the grid port, causing the inductor current to quickly rise to the current-limiting threshold and trigger current-limiting. After switching to the zero-level freewheeling state, the voltage drop across the inductor is close to zero, resulting in a very slow decrease in the inductor current and a long freewheeling time. This leads to high thermal stress on the power switching devices in the freewheeling circuit, making them prone to damage. Summary of the Invention

[0004] This application provides a power converter, a wave-by-wave current limiting method and system, which can reduce the thermal stress of power switching devices when performing wave-by-wave current limiting in short-circuit scenarios, and ensure the reliable operation of the power converter.

[0005] In a first aspect, this application provides a power converter, including: a control circuit and a power conversion circuit. The power conversion circuit is electrically connected to the control circuit, and the control circuit can control the operating state of the power conversion circuit; the control circuit is used to perform wave-by-wave current limiting control on the power conversion circuit when the current at the off-grid port of the power conversion circuit reaches the wave-by-wave current limiting threshold and the off-grid port is not short-circuited; and to control the power conversion circuit to stop working when the current at the off-grid port of the power conversion circuit reaches the wave-by-wave current limiting threshold and the off-grid port is short-circuited.

[0006] The solution provided in this application can determine the cause of the off-grid current reaching the wave-by-wave current limiting threshold based on the voltage and current states of the off-grid port of the power conversion circuit, and then adopt a more reasonable control strategy. Specifically, when the off-grid current reaches the wave-by-wave current limiting threshold and the off-grid port is not short-circuited, it is determined that an overload may have occurred, and wave-by-wave current limiting can be performed first under overload conditions; when the off-grid current reaches the wave-by-wave current limiting threshold and the off-grid port is short-circuited, the power conversion circuit can be controlled to stop working, avoiding overheating and damage to the power switching devices due to wave-by-wave current limiting under short-circuit conditions. Therefore, the solution provided in this application can reduce the thermal stress on the power switching devices and ensure the reliable operation of the power converter.

[0007] In one possible implementation, the control circuit includes: a voltage comparator circuit, a current comparator circuit, and a controller; the voltage comparator circuit is configured to output a first level to the controller when the voltage sampling value at the off-grid port of the power conversion circuit is within a preset voltage range, and to output a second level to the controller when the voltage sampling value at the off-grid port of the power conversion circuit is not within the preset voltage range; the current comparator circuit is configured to output a first level to the controller when the current sampling value at the off-grid port of the power conversion circuit is within a preset current range, and to output a second level to the controller when the current sampling value at the off-grid port of the power conversion circuit is not within the preset voltage range; the controller is configured to perform wave-by-wave current limiting control on the power conversion circuit when both the current comparator circuit and the voltage comparator circuit output a second level, and to control the power conversion circuit to stop operating when both the current comparator circuit and the voltage comparator circuit output a first level.

[0008] In one possible implementation, the upper limit of the preset voltage range is a first voltage threshold, and the lower limit of the preset voltage range is a second voltage threshold; the voltage comparison circuit includes: a first comparator and a second comparator; the input voltage of the first input terminal of the first comparator is the first voltage threshold; a voltage sample value is input to the second input terminal of the first comparator and the first input terminal of the second comparator; the input voltage of the second input terminal of the second comparator is the second voltage threshold; the output terminals of the first and second comparators are connected to the output terminal of the voltage comparison circuit; the output terminal of the voltage comparison circuit is connected to the first input terminal of the controller.

[0009] In one possible implementation, the upper limit of the preset current range is a first current threshold, and the lower limit of the preset current range is a second current threshold. The current comparison circuit includes a third comparator and a fourth comparator. The input voltage at the first input terminal of the third comparator is used to characterize the first current threshold. The input voltage at the second input terminal of the third comparator and the input voltage at the first input terminal of the fourth comparator are used to characterize the current sample value. The input voltage at the second input terminal of the fourth comparator is used to characterize the second current threshold. The output terminals of the third and fourth comparators are connected to the output terminal of the current comparison circuit. The output terminal of the current comparison circuit is connected to the second input terminal of the controller.

[0010] In one possible implementation, the controller is specifically configured to trigger wave-by-wave current limiting when the current comparison circuit outputs a second level and the duration of the voltage comparison circuit outputting a first level is less than a first preset duration; and to control the power conversion circuit to stop working when the current comparison circuit outputs a second level and the duration of the voltage comparison circuit outputting a first level is greater than or equal to the first preset duration.

[0011] In one possible implementation, the controller is configured to perform wave-by-wave current limiting on the power conversion circuit for a second preset duration when the current comparison circuit outputs a second level and the duration of the voltage comparison circuit outputting a first level is less than a first preset duration; and to control the power conversion circuit to stop working when the number of times wave-by-wave current limiting is triggered within the second preset duration reaches a preset number.

[0012] In one possible implementation, the power conversion circuit includes multiple power conversion sub-circuits; the DC side of each power conversion sub-circuit is connected in parallel, and the AC side of each power conversion sub-circuit is connected to one phase of AC power.

[0013] Secondly, this application also provides a wave-by-wave current limiting method applied to a power converter, the power converter including a power conversion circuit, comprising: performing wave-by-wave current limiting control on the power conversion circuit when the current at the off-grid port of the power conversion circuit reaches the wave-by-wave current limiting threshold and the off-grid port is not short-circuited; and controlling the power conversion circuit to stop working when the current at the off-grid port of the power conversion circuit reaches the wave-by-wave current limiting threshold and the off-grid port is short-circuited.

[0014] Using this method, if the current at the off-grid port reaches the wave-by-wave current limiting threshold and the off-grid port is not short-circuited, an overload may have occurred, and wave-by-wave current limiting can be performed first under overload conditions. If the current at the off-grid port reaches the wave-by-wave current limiting threshold and the off-grid port is short-circuited, the power conversion circuit can be controlled to stop working, avoiding overheating and damage to the power switching devices due to wave-by-wave current limiting under short-circuit conditions. Therefore, the solution provided in this application can reduce the thermal stress on the power switching devices and ensure the reliable operation of the power converter.

[0015] Thirdly, this application also provides a controller for executing the method provided in the second aspect above.

[0016] Fourthly, this application also provides a power conversion system, including the power converter provided in the first aspect and any implementation thereof.

[0017] Fifthly, this application also provides a computer storage medium for storing a computer program, which, when executed, implements the method provided in the second aspect above. Attached Figure Description

[0018] Figure 1 A schematic diagram of the inductor current path during short-circuit wave-by-wave current limiting;

[0019] Figure 2 A schematic diagram of a zero-level freewheeling path;

[0020] Figure 3Waveforms of inductor current, carrier wave, and switching device drive signals;

[0021] Figure 4 A schematic diagram of the power converter provided in the embodiments of this application. Figure 1 ;

[0022] Figure 5 A schematic diagram of the power converter provided in the embodiments of this application. Figure 2 ;

[0023] Figure 6 Schematic diagram of the power conversion circuit provided in the embodiments of this application Figure 1 ;

[0024] Figure 7 A schematic diagram of a voltage comparison circuit provided in an embodiment of this application;

[0025] Figure 8 A schematic diagram of a current comparison circuit provided in an embodiment of this application;

[0026] Figure 9 A schematic diagram of the power converter provided in the embodiments of this application. Figure 3 ;

[0027] Figure 10 A flowchart of the wave-by-wave current limiting method provided in the embodiments of this application;

[0028] Figure 11 A schematic diagram of a power conversion system provided in an embodiment of this application;

[0029] Figure 12 This is a schematic diagram of a controller provided in an embodiment of this application. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solution of this application, the application scenarios of the technical solution of this application will be described first below.

[0031] The power converter in this application can be an inverter, specifically a single-phase inverter or a three-phase inverter. The inverter can be applied to a photovoltaic power generation system or a photovoltaic-energy storage system, and the embodiments in this application are not specifically limited. The photovoltaic-energy storage system includes a photovoltaic power generation system and an energy storage system, and can also be called a solar photovoltaic energy storage power generation system. The photovoltaic-energy storage system can use photovoltaic modules to convert solar energy into electrical energy, and then use an energy storage device (usually an energy storage battery) to store the excess electrical energy generated, which can then be released for use when needed.

[0032] The following explanation uses the Highly Efficient and Reliable Inverter Concept (HERIC) circuit with a single-phase output in the first quadrant as an example. In this case, the output current is positive and flows out of the bridge arm.

[0033] See Figure 1 The figure shows a schematic diagram of the inductor current path during short-circuit wave-by-wave current limiting.

[0034] An off-grid port refers to the output interface used to connect local loads (such as household appliances), isolated from the external mains grid to ensure independent operation of the system during power outages. When an off-grid port experiences overload and current limiting occurs, the inductor current path is as follows: Figure 1 As shown.

[0035] When a short circuit occurs at the off-grid port, after the risers Q2 and Q3 are turned on, the inductor current rises rapidly because the voltage drop across inductors L1 and L2 is close to the bus voltage Vbus. This causes the inductor current to quickly reach the wave-by-wave current limiting threshold shortly after the risers Q2 and Q3 are turned on, triggering a switch to freewheeling mode.

[0036] See Figure 2 This figure is a schematic diagram of a zero-level freewheeling path.

[0037] In freewheeling mode, when the horizontal transistors Q5 and Q6 are freewheeling at zero level, the voltage drop across inductors L1 and L2 is close to 0, the inductor current decreases slowly, and the freewheeling time of the horizontal transistors Q5 and Q6 is relatively long. They need to continue freewheeling until the inductor current drops below the wave-by-wave current limiting threshold before Q2 and Q3 are turned on.

[0038] See also Figure 3 The figure shows the waveforms of inductor current, carrier wave, and switching device drive signals.

[0039] Wave-by-wave signal clearing and reset can clear twice within each carrier cycle, that is, clear at the peak and trough of the carrier wave, which can improve the load capacity of the machine without changing the carrier frequency. However, because the vertical pipe is turned on for a very short time during short-circuit wave-by-wave, the horizontal pipe is constantly turned on for half of the power frequency cycle, and the long follow current time leads to large thermal stress in the horizontal pipe.

[0040] During short-circuit wave clearing, the vertical transistors Q2 / Q3 are turned on, and the current rises at a steep slope. When the inductor current rises to the wave clearing point set by the hardware, the hardware wave clearing signal is triggered. After a delay, the current rises to the actual peak value of the inductor current before the vertical transistors are forcibly blocked. Since the horizontal transistors Q5 / Q6 are not blocked, the inductor current freewheels at zero level. At this time, the current decreases slowly, falling below the wave clearing point after several carrier cycles. The wave clearing signal is cleared at the peak or trough of the carrier wave, releasing the forced wave clearing of the vertical transistors. Compared to overload wave clearing, the thermal stress on the horizontal transistors increases significantly during short-circuit wave clearing, which may damage the power switching devices in the freewheeling circuit and reduce the reliability of the power converter.

[0041] To address the above technical issues, this application provides a power converter, a wave-by-wave current limiting method and system. Based on the voltage and current state of the off-grid port of the power conversion circuit, the method can determine the cause of the off-grid port current reaching the wave-by-wave current limiting threshold, and then adopt reasonable control strategies for overload and short circuit. This can reduce the thermal stress of power switching devices and ensure the reliable operation of the power converter.

[0042] When wave-by-wave current limiting is performed in short-circuit scenarios, the thermal stress of power switching devices is reduced, ensuring the reliable operation of the power converter.

[0043] The terms "first" and "second" used in this application description are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated.

[0044] In this application, unless otherwise expressly specified and limited, the term "connection" shall be interpreted broadly. For example, "connection" may be a fixed connection, a detachable connection, or an integral part; it may be a direct connection or an indirect connection through an intermediate medium.

[0045] See Figure 4 This figure is a schematic diagram of the power converter provided in an embodiment of this application. Figure 1 .

[0046] The power converter 10 provided in this application embodiment includes: a control circuit 11 and a power conversion circuit 12.

[0047] The AC side of the power conversion circuit 12 is used to connect to AC power. The power conversion circuit 12 is electrically connected to the control circuit 11, which can control the operating state of the power conversion circuit 12, such as stopping the power conversion circuit 12 or performing wave-by-wave current limiting control on the power conversion circuit 12.

[0048] The off-grid port of power converter 10 is used to connect to the load.

[0049] The control circuit 11 is used to perform wave-by-wave current limiting control on the power conversion circuit 12 when the current at the off-grid port of the power conversion circuit 12 reaches the wave-by-wave current limiting threshold and the off-grid port is not short-circuited; and to control the power conversion circuit 12 to stop working when the current at the off-grid port of the power conversion circuit 12 reaches the wave-by-wave current limiting threshold and the off-grid port is short-circuited.

[0050] In this embodiment, the control circuit 11 can determine the cause of the current at the off-grid port reaching the wave-by-wave current limiting threshold based on the voltage and current state of the off-grid port of the power conversion circuit, and then adopt a reasonable control strategy.

[0051] For power converter 10, overload or short circuit will generally cause the current at the off-grid port to exceed the current threshold. When the off-grid port is overloaded, the voltage value at the off-grid port is greater than the voltage value when the load is normal. At this time, there is no short circuit at the off-grid port, so wave-by-wave current limiting can be performed normally under overload scenarios. In addition, during the wave-by-wave current limiting control process, the freewheeling time of the power switching devices in the freewheeling circuit of the power converter is relatively short.

[0052] When the current at the off-grid port of power converter 10 reaches the pulse-by-pulse current limiting threshold and the off-grid port is short-circuited, the current increases abnormally due to the short circuit. At this time, control circuit 11 can control power conversion circuit 12 to stop working, that is, to perform pulse blocking on each power switching device in power conversion circuit 12, causing power converter 10 to switch to standby mode, thus preventing overheating and damage to the power switching devices due to pulse-by-pulse current limiting. Pulse blocking refers to shutting down (blocking) the pulse width modulation (PWM) signal that generates the current.

[0053] In summary, the solution provided by the embodiments of this application can reduce the thermal stress of power switching devices and ensure the reliable operation of the power converter.

[0054] The following section will explain the specific implementation method.

[0055] See Figure 5 This figure is a schematic diagram of the power converter provided in an embodiment of this application. Figure 2 .

[0056] In this embodiment of the application, the control circuit 11 includes: a voltage comparison circuit 1112, a current comparison circuit 1113, and a controller 111.

[0057] The controller 111 can be an application-specific integrated circuit (ASIC), a programmable logic device (PLD), a digital signal processor (DSP), or a combination thereof. The PLD can be a complex programmable logic device (CPLD), a field-programmable gate array (FPGA), a generic array logic (GAL), or any combination thereof; this application does not specifically limit the type of PLD.

[0058] The voltage comparison circuit 1112 compares the voltage sample value of the off-grid port of the power conversion circuit 12 with a preset voltage range and outputs the comparison result to the controller 111. Specifically, the voltage comparison circuit 1112 outputs a first level to the controller 111 when the voltage sample value of the off-grid port of the power conversion circuit 12 is within the preset voltage range; and outputs a second level to the controller when the voltage sample value of the off-grid port of the power conversion circuit 12 is not within the preset voltage range.

[0059] In one example, the first level is high and the second level is low.

[0060] The current comparison circuit 1113 compares the current sampling value of the off-grid port of the power conversion circuit 12 with a preset current range and outputs the comparison result to the controller 111. Specifically, the current comparison circuit 1113 outputs a first level to the controller 111 when the current sampling value of the off-grid port of the power conversion circuit 12 is within the preset current range; and outputs a second level to the controller 111 when the current sampling value of the off-grid port of the power conversion circuit 12 is not within the preset voltage range.

[0061] The controller 111 can make logical judgments based on the comparison results output by the voltage comparison circuit 1112 and the current comparison circuit 1113. The controller 111 can separate the two wave blocking logics of short circuit and non-short circuit at the network port in the wave-by-wave time zone. If the network port is not short circuit, the controller 111 can transmit the wave according to the normally set wave-by-wave logic. If the network port is short circuit, the controller 111 can block the wave of the power conversion circuit 12.

[0062] Specifically, controller 111 is configured to perform wave-by-wave current limiting control on power conversion circuit 12 when both current comparator circuit 1113 and voltage comparator circuit 1112 output a second level. In this case, the off-grid port is not short-circuited, and the current reaching the wave-by-wave threshold may be due to off-grid port overload. When current comparator circuit 1113 outputs a second level and voltage comparator circuit 1112 outputs a first level, controller 111 controls the power conversion circuit to stop working. In this case, the current reaching the wave-by-wave threshold is due to off-grid port short circuit.

[0063] Taking the power converter 10 as an example, the inverter can be a single-phase inverter, a three-phase inverter, or a split-phase inverter; this application does not specifically limit the embodiments. Specifically, the power converter can employ a T-type three-level circuit, a neutral point clamped (NPC) three-level circuit, an active neutral point clamped (ANPC) three-level circuit, a split-phase inverter circuit, etc.

[0064] The following explanation uses an inverter with a HERIC circuit and output in the first quadrant as an example. In this case, the output current is positive and flows out of the bridge arm.

[0065] See Figure 6 This figure is a schematic diagram of the power conversion circuit provided in an embodiment of this application. Figure 1 .

[0066] At this time, the power conversion circuit 12 includes power switching devices Q1-Q6. The voltage sampling value of the off-grid port of the power conversion circuit 12 is the result of sampling Vout, and the current sampling value of the off-grid port is the current flowing through inductors L1 and L2.

[0067] Each power switch can be an Insulated Gate Bipolar Transistor (IGBT), an Integrated Gate-Commutated Thyristor (IGCT), a Metal Oxide Semiconductor Field-Effect Transistor (MOSFET), or a Silicon Carbide Metal Oxide Semiconductor (SiC MOSFET), etc., and the embodiments in this application are not specifically limited. For example, when the switching device is a MOSFET, each diode in the figure is a body diode; when the switching device is an IGBT or IGCT, each diode in the figure is a separately arranged anti-parallel diode, which can be a Fast Recovery Diode (FRD).

[0068] Among them, Q1-Q4 are the vertical transistors of the power conversion circuit, and Q5 and Q6 are the horizontal transistors of the power conversion circuit.

[0069] See Figure 7 The figure is a schematic diagram of the voltage comparison circuit provided in an embodiment of this application.

[0070] The upper limit of the preset voltage range is the first voltage threshold Vth1, and the lower limit is the second voltage threshold Vth2. The first voltage threshold Vth1 is greater than the second voltage threshold Vth2.

[0071] In one example, the absolute values ​​of the first voltage threshold Vth1 and the second voltage threshold Vth2 are equal. The first voltage threshold Vth1 can be obtained by dividing a 3V voltage through voltage divider resistors R13 and R16; the second voltage threshold Vth2 can be obtained by dividing a 3V voltage through voltage divider resistors R18 and R19.

[0072] The voltage comparison circuit 1112 includes: a first comparator U1 and a second comparator U2.

[0073] The input voltage at the first input terminal of the first comparator U1 is the first voltage threshold Vth1, and the voltage sample value V_EPS is input to the second input terminal of the first comparator U1.

[0074] The voltage sample value V_EPS is also input to the first input terminal of the second comparator U2, and the input voltage of the second input terminal of the second comparator U2 is the second voltage threshold Vth2.

[0075] The outputs of the first comparator U1 and the second comparator U2 are connected to the output of the voltage comparator circuit 1112. The output of the voltage comparator circuit 1112 is connected to the first input of the controller 111.

[0076] In this embodiment, when the input voltage at the first input terminal of the first comparator U1 and the second comparator U2 is higher than the input voltage at the second input terminal, a first level is output, which is a high level; when the input voltage at the first input terminal of the first comparator U1 and the second comparator U2 is lower than the input voltage at the second input terminal, a second level is output, which is a low level.

[0077] The voltage sample value V_EPS can be obtained through the voltage sampling circuit, and the level signal output by the voltage comparison circuit 1112 is represented by EPS_short.

[0078] During the operation of the power converter, when a short circuit occurs at the off-grid port, causing the off-grid port current to increase, the short circuit causes the off-grid port voltage to decrease. That is, at this time, the voltage sample value is less than the first voltage threshold Vth1 and greater than the second voltage threshold Vth2, and the voltage comparison circuit 1112 outputs the level signal EPS_short as high level.

[0079] When the off-grid current increases due to overload, the off-grid voltage will not drop sharply as in a short circuit scenario. The voltage sample value is greater than the first voltage threshold Vth1 or less than the second voltage threshold Vth2. At this time, the voltage comparison circuit 1112 outputs the level signal EPS_short as low.

[0080] See Figure 8 This figure is a schematic diagram of the current comparison circuit provided in an embodiment of this application.

[0081] The upper limit of the preset current range is the first current threshold Ith1, and the lower limit is the second current threshold Ith2. The first current threshold Ith1 is greater than the second current threshold Ith2.

[0082] In one example, the absolute values ​​of the first current threshold Ith1 and the second current threshold Ith2 are equal. The first current threshold Ith1 can be represented by the voltage obtained by dividing a 3V voltage through voltage divider resistors R1 and R3; the second current threshold Ith2 can be represented by the voltage obtained by dividing a 3V voltage through voltage divider resistors R7 and R8. It should be understood that comparators are generally used to compare input voltages. Therefore, current can be converted into voltage through resistors, and the voltage value can be used to characterize the current value. Comparing voltage values ​​is equivalent to comparing current values.

[0083] The current comparator 1113 includes: a third comparator U3 and a fourth comparator U4.

[0084] The input voltage at the first input terminal of the third comparator U3 is used to characterize the first current threshold Ith1, and the input voltage at the second input terminal of the third comparator U3 is used to characterize the current sampling value IL_INV.

[0085] The input voltage at the first input terminal of the fourth comparator U4 is used to characterize the current sampling value IL_INV, and the input voltage at the second input terminal of the fourth comparator U4 is used to characterize the second current threshold Ith2.

[0086] The outputs of the third comparator U3 and the fourth comparator U4 are connected to the output of the current comparator circuit 1113. The output of the current comparator circuit 1113 is connected to the second input of the controller 111.

[0087] In this embodiment, when the input voltage of the first input terminal of the third comparator U3 and the fourth comparator U4 is higher than the input voltage of the second input terminal, a first level is output, which is a high level; when the input voltage of the first input terminal of the third comparator U3 and the fourth comparator U4 is lower than the input voltage of the second input terminal, a second level is output, which is a low level.

[0088] The current sample value IL_INV can be obtained through the current sampling circuit, and the level signal output by the current comparison circuit 1113 is represented by POE_CBC.

[0089] During the operation of the power converter, when a short circuit or overload occurs at the off-grid port, causing the off-grid port current to increase, that is, when the current sampling value IL_INV is greater than the first current threshold Ith1 or less than the second current threshold Ith2, the level signal POE_CBC output by the current comparison circuit 1113 is low.

[0090] When there is no overload or short circuit at the off-grid port and the current at the off-grid port is normal, the current sampling value IL_INV is less than the first current threshold Ith1 and greater than the second current threshold Ith2. That is, the current sampling value IL_INV is within the preset current range. At this time, the level signal POE_CBC output by the current comparison circuit 1113 is high.

[0091] The controller 111 is configured to determine that the network port is in an overload state when the current comparison circuit 1113 outputs a second level (low level) and the voltage comparison circuit 1112 outputs a first level (high level) for a duration less than a first preset duration t1, and can normally trigger wave-by-wave current limiting.

[0092] In this application embodiment, the size of the first preset duration t1 is not specifically limited. For example, the first preset duration t1 can be set to be greater than 0.25 power frequency cycles.

[0093] When the controller 111 outputs the second level in the current comparison circuit 1113 and the voltage comparison circuit 1112 outputs the first level for a duration greater than or equal to the first preset duration t1, the controller 111 controls the power conversion circuit 12 to stop working.

[0094] Specifically, when an overload or short circuit causes POE_CBC to transition from a high level to a low level, controller 111 can trigger wave-by-wave current limiting via its internal TZ (Trip-Zone) module, performing a process of blocking only the vertical tube and not the horizontal tube, until the current drops below the wave-by-wave current limiting threshold and POE_CBC returns to a high level. Simultaneously, after POE_CBC transitions from a high level to a low level, controller 111 continuously monitors the level state of EPS_short and its duration. If the duration of the first level output by voltage comparator circuit 1112 is less than a first preset duration t1 (e.g., EPS_short remains at the second level (i.e., the duration of the first level output by voltage comparator circuit 1112 is 0), controller 111 will proceed with subsequent wave-by-wave current limiting control normally. During the wave-by-wave current limiting control process, if the duration of the first level output by the voltage comparison circuit 1112 is greater than or equal to the first preset duration t1, it indicates that a short circuit continuously occurs at the network port. The controller 111 immediately performs wave blocking processing on all switching transistors to stop the power conversion circuit from working and prevent the horizontal tube from being damaged due to excessive thermal stress.

[0095] In one possible implementation, when the duration of the first level output by the voltage comparator circuit 1112 is less than a first preset duration t1, the controller 111 performs wave-by-wave current limiting control under overload conditions. To protect the power switching devices in the power conversion circuit 12, the controller 111 performs wave-by-wave current limiting on the power conversion circuit 12 for a second preset duration t2. If the number of times wave-by-wave current limiting is triggered within the second preset duration t2 reaches a preset number N, it indicates a severe overload. It is difficult to reduce the current below the wave-by-wave current limiting threshold through wave-by-wave current limiting. Continuing wave-by-wave current limiting control may damage the power switching devices. Therefore, the controller 111 controls the power conversion circuit 12 to stop operating to protect the circuit.

[0096] Among them, the number of times the current is limited by wave is the number of times the current exceeds the current limiting threshold by wave.

[0097] In this embodiment of the application, the second preset duration t2 is not specifically limited, and the second preset duration t2 is greater than the first preset duration t1.

[0098] In summary, the solution provided in this application can determine the cause of the off-grid current reaching the wave-by-wave current limiting threshold based on the voltage and current state of the off-grid port of the power conversion circuit, and then adopt a reasonable control strategy. Normal wave-by-wave current limiting control is performed under overload scenarios; under short-circuit scenarios, the power conversion circuit can be directly controlled to stop working.

[0099] In some existing solutions, wave-by-wave current limiting is also performed in short-circuit scenarios. The power converter is only stopped after a predetermined number of wave-by-wave current limiting operations have been performed. In this implementation, if the short-circuit fault disappears before the predetermined number of wave-by-wave current limiting operations is reached, power converter shutdown can be avoided. The solution provided in this application, compared to existing solutions, avoids overheating and damage to power switching devices caused by wave-by-wave current limiting in short-circuit scenarios. Therefore, the solution provided in this application can reduce the thermal stress on power switching devices and ensure reliable operation of the power converter.

[0100] The above embodiments are illustrated using the example of a power converter outputting single-phase AC power. In another possible implementation, the power converter can output multi-phase AC power, such as three-phase AC power, which will be described in detail below with reference to the accompanying drawings.

[0101] See Figure 9 This figure is a schematic diagram of the power converter provided in an embodiment of this application. Figure 3 .

[0102] The power conversion circuit 12 provided in this application embodiment includes multiple power conversion sub-circuits, specifically including three power conversion sub-circuits as an example.

[0103] The DC sides of each power conversion sub-circuit are connected in parallel, and the AC side of each power conversion sub-circuit is used to output one phase of AC power. That is, power conversion sub-circuit 121 outputs phase A AC power, power conversion sub-circuit 122 outputs phase B AC power, and power conversion sub-circuit 123 outputs phase C AC power. In this scenario, the power converter can be a three-phase inverter.

[0104] Based on the power converter provided in the above embodiments, this application also provides a wave-by-wave current limiting method, which will be described in detail below with reference to the accompanying drawings.

[0105] See Figure 10 The figure is a flowchart of the wave-by-wave current limiting method provided in the embodiment of this application.

[0106] This method is applied to the power converter provided in any of the above embodiments, and will not be described in detail here. It includes the following steps:

[0107] S11: When the current at the off-grid port of the power conversion circuit reaches the wave-by-wave current limiting threshold and the off-grid port is not short-circuited, wave-by-wave current limiting control is performed on the power conversion circuit.

[0108] S12: When the current at the off-grid port of the power conversion circuit reaches the wave-by-wave current limiting threshold and the off-grid port is short-circuited, the power conversion circuit is controlled to stop working.

[0109] In this embodiment, the cause of the off-grid current reaching the wave-by-wave current limiting threshold can be determined based on the voltage and current state of the off-grid port of the power conversion circuit, and a reasonable control strategy can be adopted. When the power converter is overloaded or short-circuited, the off-grid current will exceed the current threshold. When the off-grid port is overloaded, the voltage value of the off-grid port is greater than the voltage value when the load is normal. At this time, the off-grid port is not short-circuited, so wave-by-wave current limiting can be performed normally under overload scenarios. Furthermore, during the wave-by-wave current limiting control process, the freewheeling time of the power switching devices in the power converter's freewheeling circuit is short. When the off-grid current reaches the wave-by-wave current limiting threshold and the off-grid port is short-circuited, the current increases abnormally due to the short circuit. In this embodiment, the power conversion circuit is controlled to stop working, that is, the power switching devices in the power conversion circuit are blocked, causing the power converter to switch to standby mode. This avoids overheating and damage to the power switching devices due to wave-by-wave current limiting, ensuring the reliable operation of the power converter.

[0110] In one possible implementation, during wave-by-wave current limiting in an overload scenario, the power conversion circuit is subjected to wave-by-wave current limiting for a second preset duration. If the number of times wave-by-wave current limiting is triggered within the second preset duration reaches a preset number, the power conversion circuit is controlled to stop operating. In this implementation, if the short-circuit fault disappears before the predetermined upper limit of wave-by-wave current limiting is reached, the shutdown of the power converter can be avoided.

[0111] Based on the power converters provided in the above embodiments, this application also provides a power conversion system, which will be described in detail below with reference to the accompanying drawings.

[0112] See Figure 11 The figure is a schematic diagram of a power conversion system provided in an embodiment of this application.

[0113] The power conversion system 200 may include one or more power converters 10. For the specific implementation of the power converter 10, please refer to the corresponding description in the above embodiments. The embodiments of this application will not be repeated here.

[0114] The power conversion system 200 may further include a power generation terminal 201. In one possible implementation, the power generation terminal 201 may be a photovoltaic power generation terminal, which may include one or more photovoltaic modules to generate direct current using solar energy. Alternatively, the power conversion system 200 may also include a power generation terminal 201 and an energy storage system 202. The energy storage system 202 may use photovoltaic modules to convert solar energy into electrical energy, and then use an energy storage device (usually an energy storage battery) to store the excess electrical energy generated, and release it for use when needed.

[0115] In addition, the power generation end 201 can also be other new energy power generation ends, such as wind power generation ends.

[0116] This application also provides a controller, which will be described in detail below with reference to the accompanying drawings.

[0117] See Figure 12 The figure is a schematic diagram of a controller provided in an embodiment of this application.

[0118] The controller 111 may include a memory 101 and a processor 102. The processor 102 may be connected to each power conversion circuit within the power converter 10 and may drive each switching device in the power conversion circuit.

[0119] like Figure 12 As shown, the memory 101 can be random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (Electronic Programmable ROM), register, hard disk, removable disk, etc.

[0120] The memory 101 can store computer instructions. When the computer instructions stored in the memory 101 are executed by the processor 102, the processor 102 can be used to execute the control method of the power converter. The memory 101 can also store data.

[0121] In the above embodiments, implementation can be achieved, in whole or in part, through software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented, in whole or in part, as a computer program product. A computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the flow or function according to the embodiments of this application is generated. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape) or a semiconductor medium (e.g., solid-state disk (SSD)).

[0122] This application also provides a readable storage medium for storing the methods provided in the above embodiments. Examples include random access memory (RAM), flash memory, read-only memory (ROM), EPROM, non-volatile read-only memory (EPROM), registers, hard disks, removable disks, or any other form of storage medium in the art.

[0123] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the methods disclosed in the embodiments, since they correspond to the product embodiments disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the description of the product embodiments.

[0124] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power converter, characterized in that, include: Control circuits, power conversion circuits; The power conversion circuit is electrically connected to the control circuit; The control circuit is used to perform wave-by-wave current limiting control on the power conversion circuit when the current at the off-grid port of the power conversion circuit reaches the wave-by-wave current limiting threshold and the off-grid port is not short-circuited. When the current at the off-grid port of the power conversion circuit reaches the wave-by-wave current limiting threshold and the off-grid port is short-circuited, the power conversion circuit is controlled to stop working.

2. The power converter according to claim 1, characterized in that, The control circuit includes: a voltage comparison circuit, a current comparison circuit, and a controller; The voltage comparison circuit is configured to output a first level to the controller when the voltage sampling value of the off-grid port of the power conversion circuit is within a preset voltage range, and to output a second level to the controller when the voltage sampling value of the off-grid port of the power conversion circuit is not within the preset voltage range. The current comparison circuit is used to output a first level to the controller when the current sampling value of the off-grid port of the power conversion circuit is within a preset current range; and to output a second level to the controller when the current sampling value of the off-grid port of the power conversion circuit is not within the preset voltage range. The controller is configured to perform wave-by-wave current limiting control on the power conversion circuit when the current comparison circuit outputs the second level and the voltage comparison circuit outputs the second level; and to control the power conversion circuit to stop working when the current comparison circuit outputs the second level and the voltage comparison circuit outputs the first level.

3. The power converter according to claim 2, characterized in that, The upper limit of the preset voltage range is a first voltage threshold, and the lower limit of the preset voltage range is a second voltage threshold. The voltage comparison circuit includes: a first comparator and a second comparator; The input voltage at the first input terminal of the first comparator is the first voltage threshold. The voltage sample value is input to the second input terminal of the first comparator and the first input terminal of the second comparator; The input voltage at the second input terminal of the second comparator is the second voltage threshold value; The output terminals of the first comparator and the second comparator are connected to the output terminal of the voltage comparison circuit. The output of the voltage comparison circuit is connected to the first input of the controller.

4. The power converter according to claim 3, characterized in that, The upper limit of the preset current range is a first current threshold, and the lower limit of the preset current range is a second current threshold. The current comparison circuit includes: a third comparator and a fourth comparator; The input voltage at the first input terminal of the third comparator is used to characterize the first current threshold. The input voltage at the second input terminal of the third comparator and the input voltage at the first input terminal of the fourth comparator are used to characterize the current sample value; The input voltage at the second input terminal of the fourth comparator is used to characterize the second current threshold. The output terminals of the third comparator and the fourth comparator are connected to the output terminal of the current comparison circuit. The output of the current comparison circuit is connected to the second input of the controller.

5. The power converter according to claim 4, characterized in that, The controller is specifically configured to trigger wave-by-wave current limiting when the current comparison circuit outputs a second level and the duration of the voltage comparison circuit outputting a first level is less than a first preset duration. When the current comparison circuit outputs a second level and the voltage comparison circuit outputs a first level for a duration greater than or equal to the first preset duration, the power conversion circuit is controlled to stop working.

6. The power converter according to claim 5, characterized in that, The controller is configured to perform wave-by-wave current limiting on the power conversion circuit for a second preset duration when the current comparison circuit outputs a second level and the duration of the voltage comparison circuit outputting a first level is less than a first preset duration; and to control the power conversion circuit to stop working when the number of times wave-by-wave current limiting is triggered within the second preset duration reaches a preset number.

7. The power converter according to any one of claims 1-6, characterized in that, The power conversion circuit includes multiple power conversion sub-circuits; The DC side of each power conversion sub-circuit is connected in parallel, and the AC side of each power conversion sub-circuit is connected to one phase of AC power.

8. A wave-by-wave current limiting method, characterized in that, Applied to a power converter, the power converter including a power conversion circuit, comprising: When the current at the off-grid port of the power conversion circuit reaches the wave-by-wave current limiting threshold and the off-grid port is not short-circuited, wave-by-wave current limiting control is performed on the power conversion circuit. When the current at the off-grid port of the power conversion circuit reaches the wave-by-wave current limiting threshold and the off-grid port is short-circuited, the power conversion circuit is controlled to stop working.

9. A controller, characterized in that, The controller is used to perform the method of claim 8.

10. A power conversion system, characterized in that, The power converter includes any one of claims 1-7.

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