Converter equipment and control method thereof

Abstract

The invention provides a converter device and a control method of the converter device. The converter device comprises a power device; the controller is connected with the power device and is configured to determine the maximum junction temperature of the power device in the current power grid period in the operation process of the converter equipment, and the maximum junction temperature is the maximum value of the junction temperature of the power device in the current power grid period; according to the difference between the maximum junction temperature and the limited junction temperature of the power device, the derating state of the converter equipment is determined, and the derating state is used for indicating whether the converter equipment is in derating operation or not and / or used for indicating the relation between actual derating and expected derating when the converter equipment is in derating operation; according to the derating state of the converter equipment, the limiting current of the converter equipment in the next power grid period is determined, and the limiting current is the limiting value of the output current of the converter equipment. On the basis of improving the safety of the power device of the converter equipment, the energy conversion effect of the converter equipment can be obviously improved.

Description

Technical Field

[0001] The present application relates to the technical field of current conversion equipment, and in particular to a current conversion equipment and a control method for the current conversion equipment. Background Art

[0002] As an energy conversion device, the inverter device generates heat during operation. As the temperature rises, the performance of the power devices in the inverter device will gradually decline. If the temperature continues to rise and exceeds the tolerance limit of the device, it may cause safety accidents such as fire. In order to cope with the impact of high temperature on power devices, the inverter device usually reduces the operating temperature of the power device by reducing the output power or operating current of the device.

[0003] The converter equipment in the prior art usually adopts a passive derating control strategy, which fits a fixed derating curve in advance based on the laboratory operating data of the R&D test, and passively derates according to the fixed derating curve in actual operation. However, the actual operating conditions are often more complicated and usually have certain differences from the laboratory conditions. Therefore, this passive derating control strategy often causes damage to the power devices of the converter equipment or poor energy conversion effect of the converter equipment. Summary of the invention

[0004] The present application provides a converter device, a control method for a converter device, a control device for a converter device, a computer-readable storage medium, and a computer program product, which can improve the energy conversion effect of the converter device on the basis of improving the safety and reliability of the power devices of the converter device.

[0005] In a first aspect, a converter device is provided, comprising: a power device; and a controller connected to the power device and configured to: determine a maximum junction temperature of the power device in a current grid cycle during operation of the converter device, wherein the maximum junction temperature is the maximum value of the junction temperature of the power device in the current grid cycle; determine a derating state of the converter device based on a difference between the maximum junction temperature and a limiting junction temperature of the power device, wherein the derating state is used to indicate whether the converter device is operating at a derating and / or to indicate a relationship between an actual derating and an expected derating when the converter device is operating at a derating; determine a limiting current of the converter device in the next grid cycle based on the derating state of the converter device, wherein the limiting current is a limiting value of the output current of the converter device.

[0006] In one embodiment, the derating state includes: a non-derating state indicating that the converter device has not yet been derated, and an over-derating state indicating that the converter device is derated and the actual derating is greater than the expected derating. The controller determines the derating state of the converter device based on the difference between the maximum junction temperature and the limiting junction temperature of the power device, and is configured to: when the maximum junction temperature of the power device is less than the limiting junction temperature of the power device, determine that the converter device is in the non-derating state or the over-derating state based on the current difference between the current limiting current and the currently received command current; the controller determines the limiting current of the converter device in the next grid cycle based on the derating state of the converter device, and is configured to: when the converter device is in the non-derating state or the over-derating state, determine that the limiting current of the converter device in the next grid cycle is greater than or equal to the current limiting current.

[0007] In one embodiment, the controller determines whether the converter device is in a non-derating state or an over-derating state based on a current difference between a current limiting current and a currently received command current, and is configured to: when the current difference is less than a current difference threshold, determine that the converter device is in an over-derating state; and / or when the current difference is greater than or equal to the current difference threshold, determine that the converter device is in a non-derating state; when the converter device is in a non-derating state or an over-derating state, the controller determines that the limiting current of the converter device in the next grid cycle is greater than or equal to the current limiting current, and is configured to: when the converter device is in an over-derating state, determine that the limiting current of the converter device in the next grid cycle is greater than the current limiting current; and / or when the converter device is in a non-derating state, determine that the limiting current of the converter device in the next grid cycle is equal to the current limiting current.

[0008] In one embodiment, the derating state includes an under-derating state indicating that the converter device is operating at a derating but the actual derating is less than the expected derating. The controller determines the derating state of the converter device based on the difference between the maximum junction temperature and the limiting junction temperature of the power device, and is configured to: determine that the converter device is in the under-derating state when the maximum junction temperature of the power device is greater than or equal to the limiting junction temperature of the power device; the controller determines the limiting current of the converter device in the next grid cycle based on the derating state of the converter device, and is configured to: determine that the limiting current of the converter device in the next grid cycle is less than the current limiting current when the converter device is in the under-derating state.

[0009] In one embodiment, the controller is further configured to: obtain actual operating parameters of the power device in the current grid cycle; determine a first historical operating condition corresponding to the current operating condition based on the actual operating parameters and the historical operating parameters of the power device under multiple historical operating conditions, wherein a parameter difference between the historical operating parameters of the first historical operating condition and the actual operating parameters is less than a parameter difference between the historical operating parameters of the second historical operating condition and the actual operating parameters, and the second historical operating condition is a historical operating condition other than the first historical operating condition among the multiple historical operating conditions; determine a limiting junction temperature of the power device in the current grid cycle based on the stored maximum junction temperature of the power device under the first historical operating condition.

[0010] In one embodiment, the controller determines a first historical operating condition corresponding to the current operating condition based on actual operating parameters and historical operating parameters of the power device under multiple historical operating conditions, and is configured as follows: when parameter differences between the actual operating parameters and the historical operating parameters under multiple historical operating conditions are greater than a parameter difference threshold, two historical operating conditions are selected from multiple historical operating conditions as two first historical operating conditions corresponding to the current operating condition; the controller determines a limiting junction temperature of the power device in the current grid cycle based on the stored maximum junction temperature of the power device under the first historical operating condition, and is configured as follows: based on the maximum junction temperatures of the two stored first historical operating conditions, interpolate and fit the limiting junction temperature of the power device in the current grid cycle.

[0011] In one embodiment, during the operation of the power conversion equipment, the controller determines the maximum junction temperature of the power device in the current grid cycle, and is configured to: obtain thermal performance parameters, loss data tables and actual operating parameters of the power device in the current grid cycle; determine the steady-state junction temperature and pulse power of the power device in the current grid cycle based on the actual operating parameters, thermal performance parameters and loss data tables; determine the maximum junction temperature of the power device in the current grid cycle based on the steady-state junction temperature, pulse power and power factor of the power device in the current grid cycle.

[0012] In one embodiment, the thermal performance parameters include a steady-state thermal impedance and a transient thermal impedance data table of the power device, and the actual operating parameters include the current, DC bus voltage, heat sink temperature, duty cycle, and power factor of the power device in each switching cycle in the current grid cycle. The controller determines the steady-state junction temperature and pulse power of the power device in the current grid cycle based on the actual operating parameters, thermal performance parameters, and loss data table, and is configured to: fit the conduction loss of the power device in each switching cycle based on the assumed values ​​of the current and steady-state junction temperature of the power device in each switching cycle, the duty cycle, and the loss data table; and fit the conduction loss of the power device in each switching cycle based on the assumed values ​​of the current, DC bus voltage, and steady-state junction temperature of the power device in each switching cycle. The switching loss of the power device in each switching cycle is fitted based on the switching loss and conduction loss of the power device in each switching cycle; the total loss of the power device in the current grid cycle is fitted based on the switching loss and conduction loss of the power device in each switching cycle; the estimated value of the steady-state junction temperature is calculated using the thermal balance equation based on the total loss, the heat sink temperature and the steady-state thermal impedance; when the difference between the estimated value and the assumed value is greater than the junction temperature difference threshold, the estimated value is used as the assumed value, and the estimated value of the steady-state junction temperature is continuously iterated until the difference between the estimated value and the assumed value is less than or equal to the junction temperature difference threshold, and the iteration ends; the steady-state junction temperature of the power device in the current grid cycle is determined based on the estimated value of the steady-state junction temperature fitted at the end of the iteration.

[0013] In one embodiment, the controller determines the steady-state junction temperature and pulse power of the power device in the current grid cycle based on actual operating parameters, thermal performance parameters and a loss data table, and is also configured to: fit the final total loss of the power device in the current grid cycle based on the steady-state junction temperature of the power device in the current grid cycle; determine the pulse power of the power device in the current grid cycle based on the final total loss, the total duration of the current grid cycle and the loss duration in the current grid cycle; the controller determines the maximum junction temperature of the power device in the current grid cycle based on the steady-state junction temperature, pulse power and power factor of the power device in the current grid cycle, and is configured to: determine the transient thermal impedance corresponding to the pulse power based on the pulse power and transient thermal impedance data table; determine the maximum junction temperature of the power device in the current grid cycle based on the steady-state junction temperature, transient thermal impedance, pulse power and power factor.

[0014] In a second aspect, a control method for a converter device is provided, the method comprising the following steps: during the operation of the converter device, determining a maximum junction temperature of a power device of the converter device in a current grid cycle, wherein the maximum junction temperature is the maximum value of the junction temperature of the power device in the current grid cycle; determining a derating state of the converter device based on a difference between the maximum junction temperature and a limiting junction temperature of the power device, wherein the derating state is used to indicate whether the converter device is operating at a derating and / or to indicate a relationship between an actual derating and an expected derating when the converter device is operating at a derating; determining a limiting current of the converter device in the next grid cycle based on the derating state of the converter device, wherein the limiting current is a limiting value of the output current of the converter device.

[0015] In a third aspect, a control device for a converter device is provided, comprising: a first determination module, for determining, during the operation of the converter device, a maximum junction temperature of a power device of the converter device in a current grid cycle, wherein the maximum junction temperature is the maximum value of the junction temperature of the power device in the current grid cycle; a second determination module, for determining a derating state of the converter device based on a difference between the maximum junction temperature and a limiting junction temperature of the power device, wherein the derating state is used to indicate whether the converter device is operating at a derating and / or to indicate a relationship between an actual derating and an expected derating when the converter device is operating at a derating; and a third determination module, for determining a limiting current of the converter device in the next grid cycle based on the derating state of the converter device, wherein the limiting current is a limiting value of the output current of the converter device.

[0016] In a fourth aspect, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program. When the computer program is executed by a control device of a converter device, the control device of the converter device executes the control method of the converter device in the second aspect.

[0017] In a fifth aspect, a computer program product is provided, the computer program product comprising: a computer program, when the computer program is executed by a converter device, the converter device executes the control method of the converter device in the second aspect.

[0018] The converter device provided by the first aspect of the embodiment of the present application determines the maximum junction temperature of the power device in the current grid cycle in time during the operation of the converter device, and accurately determines the derating state of the converter device according to the difference between the maximum junction temperature and the limiting junction temperature of the power device. Since the derating state can indicate whether the converter device is running at a reduced rating and / or indicate the relationship between the actual derating and the expected derating when the converter device is running at a reduced rating, the limiting current of the converter device in the next grid cycle can be quickly and accurately determined according to the derating state of the converter device. This active derating control method of dynamically adjusting the limiting current of the converter device can enable the converter device to operate stably under different load conditions or grid fluctuations, thereby improving the response speed and stability of the power system. In addition, this scheme first determines the derating state of the converter device in the current grid cycle, and then dynamically adjusts the limiting current of the converter device in the next grid cycle according to the derating state, thereby realizing a more refined derating control of the converter, which can reduce unnecessary energy waste and improve energy utilization efficiency. In addition, the derating status of the converter equipment can indicate the relationship between the actual derating and the expected derating when the converter equipment is running at a derating level, and can also make the actual derating of the converter equipment closer to the expected derating when it is running at a derating level in the next power grid cycle. Therefore, the derating control can be more accurate, and the energy conversion effect of the converter equipment can be improved on the basis of improving the safety and reliability of the power devices of the converter equipment. That is, while improving the reliability of the junction temperature of the power devices, a better grid-connected power generation effect can be achieved, the economic benefits can be improved, and the economy and reliability of the product can be better taken into account.

[0019] It can be understood that the beneficial effects of the second to fifth aspects mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic flow chart of a control method for a current converter device provided by an embodiment of the present application is shown;

[0021] Figure 2 A schematic diagram showing a curve of a junction temperature of a power device of a converter provided by an embodiment of the present application varying with time;

[0022] Figure 3 A schematic diagram showing a curve of voltage variation over time of a power device of a converter provided by another embodiment of the present application;

[0023] Figure 4a and Figure 4b Schematic diagrams of the flow charts of different parts of a control method for a current converter device provided in another embodiment of the present application are respectively shown;

[0024] Figure 5A schematic diagram showing the structure of a control device for a current converter device provided by an embodiment of the present application is shown;

[0025] Figure 6 A schematic diagram of the structure of a current conversion device provided by an embodiment of the present application is shown;

[0026] Figure 7 A schematic diagram of the structure of a current conversion device provided by another embodiment of the present application is shown; DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. In the description of the embodiments of the present application, unless otherwise specified, " / " means or, for example, A / B can mean A or B; "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships, for example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. In addition, in the description of the embodiments of the present application, "multiple" means two or more than two.

[0028] In the following, the terms "first", "second", and "third" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", and "third" may explicitly or implicitly include one or more of the features.

[0029] For the purpose of illustration rather than limitation, specific details such as specific system structures, technologies, etc. are provided to provide a thorough understanding of the embodiments of the present application. However, it should be clear to those skilled in the art that the present application may also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to prevent unnecessary details from obstructing the description of the present application.

[0030] As mentioned above, the converter equipment in the prior art usually adopts a passive derating control strategy. Taking the converter as an example, the traditional passive derating control method usually fits a fixed derating curve in advance based on the laboratory operating data of the research and development test. In actual operation, passive derating is performed according to the derating curve based on the temperature collection points on the radiator inside the converter and the operating parameters that the converter can collect under the actual operating conditions. However, the actual operating conditions are more complicated, and there are various complex conditions such as high and low penetration. There are also differences in the installation methods of end customers. For example, whether the converter is blocked by the air duct, the different installation angles of the converter, and the sealing of the installation environment will cause the actual operating conditions of the converter to be different from the laboratory conditions when the derating strategy is formulated. The method of passive derating according to the derating curve often leads to inaccurate derating triggering when the actual converter is running. In some cases, passive derating may cause the converter equipment to reduce the output power too conservatively, thereby affecting its energy conversion performance and efficiency, resulting in less power generation and poor economic benefits. In other cases, passive derating may also lead to insufficient derating of the converter, resulting in potential safety hazards of overheating or overloading of power devices, seriously reducing the reliability and safety of the product. In other words, the passive derating control strategy in the prior art may cause damage to the power devices of the converter equipment or poor energy conversion effect of the converter equipment, making it even more difficult to balance the economy and reliability of the product.

[0031] In order to at least partially solve the above-mentioned technical problems, the embodiments of the present application provide a converter device, a control method for a converter device, a control device for a converter device, a computer-readable storage medium and a computer program product, which can significantly improve the energy conversion effect of the converter device on the basis of improving the safety and reliability of the power devices of the converter device, that is, it can achieve the optimal grid-connected power generation effect while ensuring the junction temperature reliability of the power devices, improve the economic benefits, and better take into account the economy and reliability of the product.

[0032] First, an embodiment of the present application provides a control method for a current conversion device. The control method can be applicable to a variety of current conversion devices, including but not limited to various converters (such as phase-controlled converters, pulse width modulation converters, etc.), rectifiers, inverters, AC conversion devices, DC conversion devices, and other auxiliary devices and components. For simplicity, the control method for the current conversion device provided in the embodiment of the present application is described below by taking the current conversion device as a converter as an example. Specifically, the various steps of the control method for the current conversion device in the embodiment of the present application can be performed by a controller of the converter (for example, a household energy storage converter controller).

[0033] like Figure 1 As shown, the control method of the current conversion device provided in the embodiment of the present application includes the following steps:

[0034] Step S110, during the operation of the converter device, determining the maximum junction temperature of the power device of the converter device in the current grid cycle, wherein the maximum junction temperature is the maximum value of the junction temperature of the power device in the current grid cycle.

[0035] In the embodiment of the present application, the grid cycle of the converter device can be the total duration of the current or voltage starting from a certain initial state, passing through the forward maximum value, zero value, reverse maximum value, and then returning to the initial state. Figure 2 , one grid cycle of the converter can be t grid It is understood that the grid cycle of the converter in different regions may be different. For example, one grid cycle of the converter may be 20ms.

[0036] In the embodiment of the present application, the power device in the converter device may be a power semiconductor device capable of converting and controlling electric power. The power semiconductor device may be packaged as a single device in a single package (discrete device), or may be integrated with other semiconductor devices. Exemplarily, the power device in the converter device may include, but is not limited to: a diode, an insulated gate bipolar transistor (IGBT), a thyristor, a metal oxide semiconductor field-effect transistor (MOSFET), etc.

[0037] In an embodiment of the present application, the controller of the converter device can operate according to the command current or command power of the upper-level software. Specifically, the upper-level software is responsible for generating control instructions and sending them to the controller of the converter through the communication interface. The controller can adjust its parameters such as output current and output voltage according to the received control instructions to meet the needs of the system. In other words, the command current can be the current command value that the converter device needs to follow when operating, and the command power can be the power command value that the converter device needs to follow when operating. In the example where the controller of the converter operates according to the command power, the controller can calculate the command current based on the command power, and then determine the output current of the converter according to the command current.

[0038] It can be understood that the converter is a device that converts electrical energy through its internal power devices. These power devices will generate losses during the switching process, and these losses will be converted into heat, causing the junction temperature of the device to increase. Generally, when the output current of the converter increases, the conduction loss and switching loss of the power device will also increase, causing the junction temperature of the power device to increase. In some cases, the increase in junction temperature may exceed the limit junction temperature of the power device (for example, the rated operating temperature), affecting the reliability and life of the power device.

[0039] In the embodiment of the present application, considering the influence of the output current of the converter on the junction temperature of the power device, the junction temperature data of the power device can be monitored during the operation of the converter. Then, in the subsequent steps, the output current of the converter can be determined in combination with the command current and the monitored junction temperature data, so that the junction temperature data of the power device is kept within the corresponding safe junction temperature range, and the difference between the output current of the converter and the command current is reduced, so that the converter can generate electricity at the maximum capacity.

[0040] Specifically, in the embodiment of the present application, during the operation of the converter, the controller can determine in real time the maximum junction temperature of each power device of the converter in the current grid cycle. It should be understood that the maximum junction temperature of the power device in the current grid cycle is the maximum value of the junction temperature of the power device in the current grid cycle. Taking the grid cycle of 20ms as an example, the maximum value of the junction temperature of each power device in the converter within every 20ms can be determined. Figure 2 Taking the IGBT in the converter as an example, the junction temperature of the IGBT fluctuates within every 20ms. The maximum junction temperature T j.max It can be the temperature corresponding to the peak of its junction temperature waveform. It should be noted that although the waveform curve shown in the figure does not change much in different grid cycles, under actual working conditions, affected by many factors, the waveform of the junction temperature-time curve of the power device in different grid cycles may be different. Therefore, the maximum junction temperature of each power device determined by the controller of the converter may be different in different grid cycles.

[0041] In the embodiment of the present application, the controller of the converter device can adopt a variety of suitable junction temperature fitting methods to determine the maximum junction temperature of each power device in the current grid cycle. Specifically, the converter device may include a sensor for collecting the actual operating parameters of each power device (for example, the current, DC bus voltage, radiator temperature, etc. of each switching cycle of the power device in the current grid cycle). Exemplarily, the storage module (such as a memory, a register, etc.) of the converter device may store junction temperature reference data such as thermal performance parameters and loss data tables of each power device of the converter device. Exemplarily, during the operation of the converter, the controller can control the sensor to collect the actual operating parameters of each power device in each grid cycle in real time, and can accurately determine the maximum junction temperature of each power device in the current grid cycle by combining the actual operating parameters of each power device collected by the sensor and the junction temperature reference data of each power device. Exemplarily and non-restrictively, the steady-state junction temperature and pulse power of the power device in the current grid cycle can be iteratively fitted by discretizing the loss data of the power device in each switching cycle of the current grid cycle. Furthermore, the maximum junction temperature of the power device in the current grid cycle can be accurately fitted according to the steady-state junction temperature and pulse power. A specific example of this solution will be described later, and for the sake of brevity, it will not be repeated here.

[0042] Taking a grid cycle of 20ms as an example, in this step, the controller of the converter can calculate the maximum junction temperature T of the power device every 20ms. j.max , realizing dynamic monitoring of the junction temperature of the power device of the converter. And the maximum junction temperature of the power device in a power grid cycle also accurately reflects the change of the junction temperature of the power device in a short period of time (that is, the junction temperature fluctuates between the highest temperature of the corresponding peak and the lowest temperature of the corresponding trough). Therefore, it is convenient to adjust the output current in time according to the change of its junction temperature.

[0043] In the prior art, some solutions monitor the steady-state junction temperature of the power device of the converter and determine the output current of the converter according to the steady-state junction temperature. However, the steady-state junction temperature can only reflect the temperature of the power device in a stable working state, but cannot reflect the temperature of the power device in an unstable scenario (such as a scenario where the output current of the converter changes rapidly). Therefore, the steady-state junction temperature of the power device of the converter cannot accurately reflect the junction temperature of the power device, and the accuracy of the solution for determining the output current of the converter according to the steady-state junction temperature is poor. Other solutions monitor the instantaneous junction temperature of the power device of the converter and determine the output current of the converter according to the instantaneous junction temperature. Although the instantaneous junction temperature can reflect the dynamic change of the temperature of the power device, it is very difficult to monitor the instantaneous junction temperature of the power device under actual working conditions, especially in the scenario where the temperature changes rapidly, the determination of the instantaneous junction temperature usually has a large delay, and the calculation method is very complicated and the amount of calculation is also very large, resulting in poor availability of the instantaneous junction temperature actually monitored. Therefore, the feasibility and accuracy of the solution for determining the output current of the converter according to the instantaneous junction temperature of the power device are both poor. In the embodiment of the present application, the controller determines the maximum junction temperature of the power device of the converter in each grid cycle in real time. On the one hand, the maximum junction temperature of the power device in each grid cycle can accurately reflect the change of its junction temperature in a short period of time; on the other hand, compared with the instantaneous junction temperature, it is easier and more accurate to monitor the maximum junction temperature of the power device in each grid cycle. Therefore, after the controller accurately monitors the maximum junction temperature of the power device of the converter in each grid cycle, it can provide a more reliable decision-making basis for the subsequent determination of the derating state of the converter and the dynamic adjustment of the limiting current of the converter.

[0044] Step S120, determining the derating state of the converter device according to the difference between the maximum junction temperature and the limiting junction temperature of the power device, wherein the derating state is used to indicate whether the converter device is operated at a derating and / or to indicate the relationship between the actual derating and the expected derating when the converter device is operated at a derating.

[0045] In the embodiment of the present application, considering the influence of the output current of the converter on the junction temperature of the power device, during the operation of the converter, not only the junction temperature data of the power device is monitored, but also the output current of the converter is limited so that the junction temperature of the power device is kept within the corresponding safe junction temperature range. Exemplarily, the controller can set the limit value of the output current of the converter, and limit the output current of the converter according to the limit value. That is to say, in the embodiment of the present application, during the operation of the converter, the controller can determine the output current of the converter according to the command current, the junction temperature data of the power device and the limit value of the output current of the converter. In the embodiment of the present application, the limit value of the output current of the converter is referred to as the limit current of the converter. Specifically, the controller can set the initial value of the limit current of the converter in advance according to the design parameters, thermal management capabilities, external operating conditions, etc. of the converter. For example, the initial value of the limit current can be set to the rated current of the converter. Exemplarily, at the initial moment, the controller of the converter can limit the output current of the converter according to the initial value of the limiting current. During operation, the limiting current of the converter can be dynamically updated according to the junction temperature data of each power device monitored in real time, and then the output current of the converter can be limited according to the updated limiting current. It can be understood that the purpose of dynamically updating the limiting current in the embodiment of the present application is to reduce the difference between the output current of the converter and the command current on the basis of keeping the junction temperature data of the power device within the corresponding safe junction temperature range, so that the converter can generate electricity at the maximum capacity.

[0046] In an embodiment of the present application, the limiting junction temperature of the power device may be the current limiting value of the junction temperature of the power device. A variety of suitable methods may be used to determine the limiting junction temperature of the power device. In one example, the limiting junction temperature of the power device may be pre-set and stored according to the rated junction temperature or the limiting operating junction temperature of the power device. The limiting junction temperature of the power device may be less than or equal to the limiting operating junction temperature of the power device. For example, if the limiting operating junction temperature of a certain power device is equal to 175°C, the limiting junction temperature of the power device may be set to 148°C according to a derating of 0.85 times. In another example, the historical operating parameters and maximum junction temperature of the power device under multiple historical operating conditions may be stored in advance in the storage module of the converter. Then, the first historical operating condition corresponding to the current operating condition may be determined based on the actual operating parameters of the power device in the current grid cycle and the historical operating parameters of the power device under multiple historical operating conditions. That is, the historical operating condition that is the same or close to the current operating condition is selected from the previous historical operating conditions as the first historical operating condition. And the limiting junction temperature of the power device in the current grid cycle may be determined based on the maximum junction temperature of the stored power device under the first historical operating condition. That is, the limit junction temperature of the power device in the current grid cycle can be determined based on the maximum junction temperature of the historical operating conditions that are similar to or the same as the actual operating conditions of the power device. A specific example of this solution will be explained later, and for the sake of brevity, it will not be repeated here.

[0047] In the embodiment of the present application, the derated state of the converter device is used to indicate whether the converter device is running at a reduced rating and / or to indicate the relationship between the actual derated and the expected derated when the converter device is running at a reduced rating. In one example, the derated state of the converter device is used to indicate whether the converter device is running at a reduced rating. For example, the derated state of the converter device includes a non-derated state for indicating that the converter device has not yet run at a reduced rating and a derated state for indicating that the converter device is running at a reduced rating. In another example, the derated state of the converter device is used to indicate the relationship between the actual derated and the expected derated when the converter device is running at a reduced rating. For example, the derated state of the converter device includes an over-derated state for indicating that the converter device is running at a reduced rating and the actual derated is greater than the expected derated and an under-derated state for indicating that the converter device is running at a reduced rating and the actual derated is less than the expected derated. Alternatively, in some special examples, the derated state of the converter device may also include an ideal derated state for indicating that the converter device is running at a reduced rating and the actual derated is equal to the expected derated. That is, the derated state of the converter device may be subdivided into different states according to the relationship between the actual derated and the expected derated when the converter device is running at a reduced rating.

[0048] In the embodiment of the present application, a variety of suitable methods can be used to determine the derating state of the converter device according to the difference between the maximum junction temperature of the power device in the current grid cycle and the limiting junction temperature of the power device. Optionally, the derating state of the converter device can be determined only according to the difference between the maximum junction temperature in the current grid cycle and the limiting junction temperature of the power device. Alternatively, the derating state of the converter device can also be determined comprehensively according to the difference between the maximum junction temperature in the current grid cycle and the limiting junction temperature of the power device, combined with other derating reference parameters. Exemplarily, other derating reference parameters may include the command current and command power received by the converter device, the current output current of the converter device, the current limiting current, etc. For example, when the maximum junction temperature of the power device in the current grid cycle is greater than or equal to the limiting junction temperature of the power device, it can be determined that the converter device is in an under-derating state. For another example, when the maximum junction temperature of the power device in the current grid cycle is less than the limiting junction temperature of the power device, combined with other derating reference parameters, it can be determined that the converter device is in a non-derating state, an over-derating state, or an ideal derating state. In one example, it is possible to determine whether the converter device is in a non-derating state or an over-derating state based on the difference between the command current currently received by the converter and the current output current. For example, when the converter is not derated, in order to improve the power generation efficiency, the output current is usually close to the command current; when the converter is over-derating, the output current of the converter will be limited, resulting in an increase in the difference with the command current. That is, when the absolute value of the difference between the output current of the converter and the command current is small, it can be determined that the converter device is in a non-derating state; when the absolute value of the difference between the output current of the converter and the command current is large, it can be determined that the converter device is in an over-derating state. In another example, it is possible to determine whether the converter device is in a non-derating state or an over-derating state based on the difference between the command current currently received by the converter and the current limiting current. For example, when the converter is not derated, the limiting current is usually greater than or equal to the command current; when the converter is over-derating, the limiting current will be less than the command current.

[0049] Step S130, determining a limiting current of the converter device in the next power grid cycle according to the derating state of the converter device, wherein the limiting current is a limiting value of the output current of the converter device.

[0050] In an embodiment of the present application, the limiting current of the converter device in the next grid cycle is dynamically adjusted according to the derating state of the converter device at the end of the current grid cycle, so that the junction temperature of the power device in the next grid cycle is lower than the limiting junction temperature of the power device, and the difference between the output current of the converter in the next grid cycle and the received command current is reduced.

[0051] In the embodiments of the present application, different derating states of the converter device may correspond to different limiting current adjustment strategies. Exemplarily, the non-derating state of the converter device may correspond to a maintenance strategy of maintaining the limiting current unchanged, that is, it may be determined that the limiting current of the converter device in the next grid cycle is equal to the current limiting current. Exemplarily, the under-derating state of the converter device may correspond to a reduction strategy of reducing the limiting current, that is, it may be determined that the limiting current of the converter device in the next grid cycle is less than the current limiting current. Exemplarily, the over-derating state of the converter device may correspond to a release strategy of increasing the limiting current, that is, it may be determined that the limiting current of the converter device in the next grid cycle is greater than the current limiting current. Specific examples of these schemes will be elaborated in detail later, and for the sake of brevity, they will not be repeated here.

[0052] As mentioned above, the passive derating control strategy in the prior art may cause damage to the power devices of the converter equipment or poor energy conversion effect of the converter equipment, and it is even more difficult to take into account the economy and reliability of the product. According to the control method of the converter equipment in the embodiment of the present application, the maximum junction temperature of the power device in the current grid cycle is timely determined during the operation of the converter equipment, and the derating state of the converter equipment is accurately determined according to the difference between the maximum junction temperature and the limit junction temperature of the power device. Since the derating state can indicate whether the converter equipment is running at a derating and / or indicate the relationship between the actual derating and the expected derating when the converter equipment is running at a derating, the limiting current of the converter equipment in the next grid cycle can be quickly and accurately determined according to the derating state of the converter equipment. This active derating control method of dynamically adjusting the limiting current of the converter equipment can enable the converter equipment to operate stably under different load conditions or grid fluctuations, thereby improving the response speed and stability of the power system. In addition, this scheme first determines the derating state of the converter device in the current grid cycle, and then dynamically adjusts the limiting current of the converter device in the next grid cycle according to the derating state, thereby realizing more refined derating control of the converter, which can reduce unnecessary energy waste and improve energy utilization efficiency. Moreover, the derating state of the converter device can indicate the relationship between the actual derating and the expected derating when the converter device is running at a derating state, and can also make the actual derating of the converter device closer to the expected derating when the converter device is running at a derating state in the next grid cycle. Therefore, the derating control can be made more accurate, and the energy conversion effect of the converter device can be improved on the basis of improving the safety and reliability of the power devices of the converter device. That is, while improving the junction temperature reliability of the power device, a better grid-connected power generation effect can be achieved, the economic benefits can be improved, and the economy and reliability of the product can be better taken into account.

[0053] In one implementation, the derating state includes: a non-derating state indicating that the converter device has not been operated at a derating, and an over-derating state indicating that the converter device is operated at a derating and the actual derating is greater than the expected derating.

[0054] Step S120 determines the derating state of the converter device according to the difference between the maximum junction temperature and the limiting junction temperature of the power device, including: Step S121, when the maximum junction temperature of the power device is less than the limiting junction temperature of the power device, determines whether the converter device is in a non-derating state or an over-derating state according to the current difference between the current limiting current and the currently received command current.

[0055] It can be understood that if the maximum junction temperature of the power device in the current grid cycle is less than the limit junction temperature of the power device, it can be said that the junction temperature of the power device in the current grid cycle is always less than the limit junction temperature of the power device. This situation may correspond to a variety of scenarios: First, it may be that the converter has not yet entered the derated operation state (for example, the power demand in the grid is small, and the command current received by the converter is small); second, it may be that the converter has entered the derated operation state, but the derated range is too large, and the actual derated exceeds the expected derated, which is intuitively manifested as the output current of the converter cannot meet the actual power demand; third, in some special cases, it may also be that the converter has entered the derated operation state, but the derated range just meets expectations, that is, the actual derated of the converter is equal to the expected derated. In the embodiment of the present application, the special scenario where the actual derated of the converter is equal to the expected derated is not considered for the time being, and the analysis focuses on the first two scenarios, among which the first scenario is the scenario where the converter is in a non-derated state, and the second scenario is the scenario where the converter is in an over-derated state.

[0056] In an embodiment of the present application, in order to accurately distinguish whether the converter is in a non-derating state or an over-derating state, when it is determined that the maximum junction temperature of the power device of the converter in the current grid cycle is less than the limiting junction temperature of the power device, the current difference between the current limiting current of the converter and the currently received command current is further determined.

[0057] It can be understood that the command current currently received by the converter represents the actual power generation demand, and therefore, the current difference between the current limiting current of the converter and the command current currently received can more accurately reflect whether the converter is operating at a reduced rating. Therefore, in the embodiment of the present application, according to the current difference between the current limiting current and the command current of the converter, it is possible to accurately distinguish whether the converter is in a non-derating state or an over-derating state.

[0058] Step S130 determines the limiting current of the converter device in the next grid cycle according to the derating state of the converter device, including: Step S131, when the converter device is in a non-derating state or an over-derating state, determines that the limiting current of the converter device in the next grid cycle is greater than or equal to the current limiting current.

[0059] Exemplarily, the current limiting current of the converter device may be the current limiting current of the converter device at the current moment (i.e., the end moment of each grid cycle), or may be the average current limiting current of the converter device in the current grid cycle. Optionally, the current limiting current of the converter device in each grid cycle may be the same. Alternatively, the current limiting current of the converter device in each grid cycle may also change regularly.

[0060] In one example, when it is determined that the converter device is in a non-derating state, it can be determined that the limiting current of the converter device in the next grid cycle is equal to the current limiting current; when it is determined that the converter device is in an over-derating state, it can be determined that the limiting current of the converter device in the next grid cycle is greater than the current limiting current. In some special examples, when it is determined that the converter device is in a non-derating state or an over-derating state, it can be determined that the limiting current of the converter device in the next grid cycle is greater than the current limiting current, but the adjustment range of the limiting current corresponding to these two derating states can be different. For example, when it is determined that the converter device is in a non-derating state, it can be determined that the limiting current of the converter device in the next grid cycle is slightly equal to m1 times the current limiting current, and when it is determined that the converter device is in an over-derating state, it can be determined that the limiting current of the converter device in the next grid cycle is equal to m2 times the current limiting current, where 1<m1<m2.

[0061] In the above scheme, by comparing the difference between the current limiting current of the converter and the received command current, it is possible to quickly and accurately distinguish whether the converter is in an un-derating state or an over-derating state. Furthermore, when it is determined that the converter is in an un-derating state or an over-derating state, it is determined that the limiting current of the next grid cycle can be maintained at the current level or appropriately increased. Thus, the stability and efficiency of the power supply can be improved. Thus, by accurately measuring and analyzing the current difference between the current limiting current and the command current of the converter, an accurate judgment of the derating state of the converter is achieved, and the limiting current of the next grid cycle is dynamically adjusted accordingly, thereby improving the flexibility, efficiency and stability of the power supply.

[0062] In one embodiment, step S121 determines whether the converter device is in a non-derating state or an over-derating state based on the current difference between the current limiting current and the currently received command current, including: step S121a, when the current difference is less than the current difference threshold, determining that the converter device is in an over-derating state; step S131 determines that the limiting current of the converter device in the next grid cycle is greater than or equal to the current limiting current when the converter device is in a non-derating state or an over-derating state, including: step S131a, when the converter device is in an over-derating state, determining that the limiting current of the converter device in the next grid cycle is greater than the current limiting current.

[0063] In an embodiment of the present application, the current difference threshold can be set according to actual needs. For example, the current difference threshold is equal to 0. The current difference between the current limiting current and the currently received command current can be the current difference obtained by subtracting the command current from the limiting current. That is, when the current limiting current of the converter is less than the current command current, it can be determined that the converter device is in an over-derating state. And when it is determined that the converter device is in an over-derating state, it can be determined that the limiting current of the converter device in the next grid cycle is greater than the current limiting current. Exemplarily, the limiting current of the converter device in the next grid cycle can be equal to m times the current limiting current, and m can fall within the interval (1,1.5].

[0064] It is understandable that in the over-derating state, the converter fails to fully utilize its output capacity, resulting in insufficient power supply. When it is determined that the converter equipment is in the over-derating state, by increasing the limiting current of the next grid cycle, the output capacity of the converter can be more effectively utilized to meet more power demand, thereby improving the supply efficiency of the entire power system.

[0065] In one embodiment, step S121 determines whether the converter device is in a non-derating state or an over-derating state based on the current difference between the current limiting current and the currently received command current, including: step S121b, when the current difference is greater than or equal to the current difference threshold, determining that the converter device is in a non-derating state; step S131 determines that the limiting current of the converter device in the next grid cycle is greater than or equal to the current limiting current when the converter device is in a non-derating state or an over-derating state, including: step S131b, when the converter device is in a non-derating state, determining that the limiting current of the converter device in the next grid cycle is equal to the current limiting current.

[0066] Similarly, taking the current difference threshold value equal to 0 as an example, when the current limiting current of the converter is greater than or equal to the current command current, it can be determined that the converter device is in a non-derating state. And when it is determined that the converter device is in a non-derating state, it can be determined that the limiting current of the converter device in the next grid cycle is equal to the current limiting current.

[0067] It can be understood that in the non-derating state, the converter itself can output power according to the command current requirements. By keeping the limit current unchanged, the current power demand can continue to be met. It can also reduce the potential risks and uncertainties caused by adjustments and maintain the stable operation of the system. In addition, keeping the current limit current unchanged can reduce unnecessary energy waste and equipment loss.

[0068] In one embodiment, the derating state includes an under-derating state indicating that the converter device is running at a derating level but the actual derating level is less than the expected derating level. Step S120 determines the derating state of the converter device according to the difference between the maximum junction temperature and the limiting junction temperature of the power device, including: Step S122, when the maximum junction temperature of the power device is greater than or equal to the limiting junction temperature of the power device, determines that the converter device is in an under-derating state; Step S130 determines the limiting current of the converter device in the next power grid cycle according to the derating state of the converter device, including: Step S132, when the converter device is in an under-derating state, determines that the limiting current of the converter device in the next power grid cycle is less than the current limiting current.

[0069] For example, when the maximum junction temperature of the diode in the converter is greater than or equal to the limiting junction temperature of the diode during a certain power grid cycle, it is determined that the converter is in an under-derating state, and further it can be determined that the limiting current of the converter in the next power grid cycle is less than the current limiting current. For example, it can be determined that the limiting current of the converter in the next power grid cycle is equal to k times the current limiting current, 0<k<1. Specifically, 0.5<k<1.

[0070] In the above scheme, when the maximum junction temperature of the power device of the converter equipment is greater than or equal to its limit junction temperature, the converter is determined to be in an under-derating state. When the converter is in an under-derating state, the limit current of the converter in the next grid cycle is reduced, which can reduce the risk of damage to the power device due to overheating, which not only helps to extend the service life of the equipment and reduce the cost of maintenance and replacement. It can also improve the reliability of the power device and help reduce energy waste and equipment loss.

[0071] In one implementation, the control method of the converter device in the embodiment of the present application further includes the following steps:

[0072] Step S101, obtaining actual operating parameters of the power device in the current power grid cycle;

[0073] Step S102, determining a first historical operating condition corresponding to the current operating condition according to the actual operating parameters and the historical operating parameters of the power device under multiple historical operating conditions, wherein a parameter difference between the historical operating parameters of the first historical operating condition and the actual operating parameters is less than a parameter difference between the historical operating parameters of the second historical operating condition and the actual operating parameters, and the second historical operating condition is a historical operating condition other than the first historical operating condition among the multiple historical operating conditions;

[0074] Step S103 : determining a limit junction temperature of the power device in the current grid cycle according to the stored maximum junction temperature of the power device under the first historical operating condition.

[0075] Exemplarily, the historical operating parameters of the power devices of the converter under multiple historical operating conditions and the maximum junction temperature of the power devices under each historical operating condition can be stored in advance in the storage module of the converter. The operating parameters of the power device may include voltage, current, etc. The historical operating parameters of the power devices of the converter under multiple historical operating conditions can be obtained through a large number of tests, or can be continuously stored and updated during the actual operation process. For example, the number of historical operating conditions is n, and n≥3. For example, the voltage V1, current I1, and maximum junction temperature T1 of the diode of the converter under the historical operating condition H1 can be stored, and the voltage V2, current I2, and maximum junction temperature T2 of the diode under the historical operating condition H2 can be stored... The voltage Vn, current In, and maximum junction temperature Tn of the diode under the historical operating condition Hn can be stored. During the actual operation of the converter, the voltage V0 and current I0 of the diode of the converter in the current grid cycle can be monitored. And the voltage V0 and current I0 can be compared with the voltage and current under n historical operating conditions stored in the storage module. Specifically, the difference between the voltage V0 and the current I0 and the voltage and current under each historical operating condition can be calculated to obtain the absolute value of the voltage difference and the absolute value of the current difference. For example, when the absolute value of the voltage difference determined by comparing a certain historical operating condition is less than the voltage threshold (for example, 0.1V) and the absolute value of the current difference is less than the current threshold (for example, 0.1A), the historical operating condition can be determined to be the first historical operating condition corresponding to the current operating condition. And the limiting junction temperature of the diode in the current power grid cycle can be determined based on the maximum junction temperature of the diode stored in the first historical operating condition. For example, the maximum junction temperature can be directly used as the limiting junction temperature of the diode in the current power grid cycle.

[0076] In this solution, the actual operating parameters of the power devices of the converter under the current working conditions are obtained in real time, and the historical operating parameters under the historical working conditions are compared to find the historical working conditions close to the current working conditions, and the limit junction temperature of the power device in the current power grid cycle is accurately determined based on the maximum junction temperature of the power device under the close historical working conditions. The determined limit junction temperature is more accurate and more in line with the requirements of the actual working conditions, which can improve the accuracy of the determination of the derating state of the converter equipment, and thus improve the stability and safety of the power system.

[0077] In one embodiment, step S102 determines a first historical operating condition corresponding to the current operating condition based on actual operating parameters and historical operating parameters of the power device under multiple historical operating conditions, including: step S102.1, when the parameter differences between the actual operating parameters and the historical operating parameters under multiple historical operating conditions are greater than the parameter difference threshold, two historical operating conditions are selected from multiple historical operating conditions as two first historical operating conditions corresponding to the current operating condition; step S103 determines the limiting junction temperature of the power device in the current grid cycle based on the stored maximum junction temperature of the power device under the first historical operating condition, including: step S103.1, based on the maximum junction temperatures of the two stored first historical operating conditions, interpolate and fit the limiting junction temperature of the power device in the current grid cycle.

[0078] In the above example of comparing the voltage V0 and the current I0 with the voltage and current under n historical operating conditions stored in the storage module, if the absolute value of the voltage difference between the current operating condition and each historical operating condition does not satisfy the condition that the absolute value of the voltage difference is less than the voltage threshold and the absolute value of the current difference is less than the current threshold. Two historical operating conditions whose historical operating parameters are closest to the actual operating parameters under the current operating condition can be determined from the n historical operating conditions as the first historical operating conditions corresponding to the current operating condition. For example, the voltage V0 of the diode in the current power grid cycle is greater than the voltage V1 under the historical operating condition H1 and less than the voltage V2 under the historical operating condition H2, the current I0 is greater than the current I1 under the historical operating condition H1 and less than the current I2 under the historical operating condition H2, and V0 is closest to V1 and V2, and I0 is closest to I1 and I2. In this example, the historical operating conditions H1 and the historical operating conditions H2 can be used as the two first historical operating conditions corresponding to the current operating condition. And according to the maximum junction temperature T1 under the historical working condition H1 and the maximum junction temperature T2 under the historical working condition H2, the limiting junction temperature of the diode in the current power grid cycle can be determined by using a linear interpolation method.

[0079] In the above scheme, even if there is a difference between the current operating condition of the converter equipment and the historical condition, the two closest historical conditions can be selected for interpolation fitting, so as to obtain a limit junction temperature closer to the actual condition. Moreover, as the actual operating parameters of the converter change, the scheme can dynamically adjust the selected historical conditions and obtain a new limit junction temperature through interpolation fitting, so that the power device can obtain reasonable junction temperature limit data under different conditions. Therefore, the accuracy and dynamic adaptability of the converter derating control are further improved.

[0080] In one embodiment, step S110 determines the maximum junction temperature of the power device in the current grid cycle during the operation of the power conversion equipment, including the following steps: step S111, obtaining the thermal performance parameters, loss data table and actual operating parameters of the power device in the current grid cycle; step S112, determining the steady-state junction temperature and pulse power of the power device in the current grid cycle based on the actual operating parameters, thermal performance parameters and loss data table; step S113, determining the maximum junction temperature of the power device in the current grid cycle based on the steady-state junction temperature, pulse power and power factor of the power device in the current grid cycle.

[0081] Exemplarily, the thermal performance parameters of the power device may include a steady-state thermal impedance and a transient thermal impedance data table of the power device. The actual operating parameters of the power device may include the current, DC bus voltage, heat sink temperature, duty cycle, and power factor of each switching cycle of the power device in the current grid cycle. The actual operating parameters of the power device may be acquired in real time by the sensor of the converter. The thermal performance parameters and loss data table of the power device may be pre-stored in the storage module of the converter. In the embodiment of the present application, a variety of suitable methods may be used to determine the steady-state junction temperature and pulse power of the power device in the current grid cycle according to the actual operating parameters, thermal performance parameters, and loss data table. Exemplarily, the steady-state junction temperature of the power device in the current grid cycle may be fitted by an iterative method or an approximate method. Then, the pulse power of the power device in the current grid cycle may be determined according to the steady-state junction temperature. Thereafter, the maximum junction temperature of the power device in the current grid cycle may be determined according to the steady-state junction temperature, pulse power, and power factor of the power device in the current grid cycle.

[0082] The above method for determining the maximum junction temperature of the power device in the current grid cycle not only considers the thermal performance parameters and loss data of the power device, but also combines the actual operating parameters of the power device in the current grid cycle. This comprehensive consideration method can more accurately reflect the thermal state of the power device in actual operation, improve the accuracy of the maximum junction temperature, and thus further improve the accuracy of the converter derating control.

[0083] In one embodiment, the thermal performance parameters include a steady-state thermal impedance and a transient thermal impedance data table of the power device, and the actual operating parameters include the current, DC bus voltage, heat sink temperature, duty cycle, and power factor of each switching cycle of the power device in the current grid cycle. In an embodiment of the present application, the loss data table may include a conduction loss data table and a switching loss data table.

[0084] Step S112 determines the steady-state junction temperature and pulse power of the power device in the current grid cycle according to the actual operating parameters, thermal performance parameters and loss data table, including the following steps S112.1 to S112.6.

[0085] Step S112.1, fitting the conduction loss of the power device in each switching cycle according to the current of the power device in each switching cycle, the assumed value of the steady-state junction temperature, the duty cycle and the loss data table.

[0086] In the embodiment of the present application, the switching cycle indicates the duration of each switching operation of the power device, that is, the time required for a complete switching process of the power device (from turning on to turning off, or from turning off to turning on). Since the switching frequency of the power device is much higher than the grid frequency, the switching device of the electronic device may undergo multiple openings and closings within a grid cycle. For example, if the switching frequency is 20kHz (switching cycle 50us), the switching device will be turned on and off 400 times each within a 50Hz grid cycle (20ms). The duty cycle indicates the ratio of the time that the signal is in a specific state (such as a high level) within a switching cycle to the entire switching cycle time. Combined with Figure 3 , the switching period of the power device can be expressed as t c The duty cycle of a power device can be expressed as Duty.

[0087] In an embodiment of the present application, when the steady-state junction temperature is unknown, a suitable hypothetical value (for example, the heat sink temperature of the power device) can be set for the steady-state junction temperature first, and an iterative method can be used to solve the steady-state junction temperature. The conduction loss data of the power device can be obtained through actual testing or through a specification sheet. Exemplarily, the conduction loss data of the power device can be stored in a storage module by table lookup, and the conduction loss of the IGBT and diode in the converter can be calculated in each switching cycle of the current grid cycle. Taking IGBT as an example, the conduction loss E of each switching cycle can be solved using the following formula (1): con :

[0088] E con =I c ×V CE ×t c ×Duty=I c ×f(I c ,T j.av )×t c ×Duty...(1)

[0089] Among them, I c It represents the current of the power device (IGBT) in each switching cycle of the current grid cycle, T j.av represents the steady-state junction temperature (specifically, it can be an assumed value of the steady-state junction temperature), V CE It represents the voltage between the C pole (collector) and the E pole (emitter) of the power device (IGBT), t cSpecifically, after the power device (IGBT) is turned on, the C pole and the E pole are connected, which can be measured by the voltage V between CE in the specification. CE The curve query obtains the V CE The value of .

[0090] Step S112.2, fitting the switching loss of the power device in each switching cycle according to the assumed values ​​of the current, DC bus voltage, steady-state junction temperature of the power device in each switching cycle and the loss data table.

[0091] It can be understood that the switching losses of the power devices stored in the specification are all ideal conditions. In the embodiment of the present application, the switching loss data table of the power device can be obtained in advance based on the actual double pulse data test, and stored in the storage module of the converter, and the switching loss of the power device in each switching cycle can be calculated by looking up the table. Exemplarily, the switching loss E of the power device in each switching cycle can be solved using the following formula (2): on , use the following formula (3) to solve the turn-off loss E of the power device in each switching cycle off :

[0092] E on =f on (I c ,V bus ,T j.av )...(2)

[0093] E off =f off (I c ,V bus ,T j.av )…(3)

[0094] Among them, I c Represents the current of the power device (IGBT) in each switching cycle of the current grid cycle, V bus represents the DC bus voltage per switching cycle, T j.av Represents the steady-state junction temperature (specifically, it may be an assumed value of the steady-state junction temperature).

[0095] Step S112.3, fitting the total loss of the power device in the current grid cycle according to the switching loss and conduction loss of the power device in each switching cycle.

[0096] For example, the total power loss of the power device in the current grid cycle is P total The discretization solution can be obtained by the following formula (4):

[0097]

[0098] Among them, tgrid Represents the power grid cycle.

[0099] Step S112.4, according to the total loss, the heat sink temperature and the steady-state thermal impedance, the estimated value of the steady-state junction temperature is calculated using the thermal balance equation.

[0100] For example, the estimated value T of the steady-state junction temperature of the power device can be calculated using the following formula (5): j.av :

[0101] T j.av =T heat sin k +R th.jh ×P total …(5)

[0102] Among them, T heat sin k Indicates the heat sink temperature of the power device in the current grid cycle, R th.jh Represents the steady-state thermal impedance of the stored power device.

[0103] Step S112.5, when the difference between the estimated value and the assumed value is greater than the junction temperature difference threshold, the estimated value is used as the assumed value, and the estimated value of the steady-state junction temperature is continuously iterated and fitted until the difference between the estimated value and the assumed value is less than or equal to the junction temperature difference threshold, and the iteration ends.

[0104] Step S112.6, determining the steady-state junction temperature of the power device in the current grid cycle according to the estimated value of the fitted steady-state junction temperature at the end of the iteration.

[0105] In the embodiment of the present application, the junction temperature difference threshold can be set according to actual needs. For example, the junction temperature difference threshold is 1° C. Through iterative fitting, the steady-state junction temperature of the power device in the current power grid cycle can be quickly and accurately determined.

[0106] The above-mentioned method for solving the steady-state junction temperature is more accurate and has less calculation amount. Therefore, the steady-state junction temperature of each power device can be determined in real time and accurately at the end of each power grid cycle, further improving the accuracy and real-time performance of the converter derating control.

[0107] In one embodiment, step S112 determines the steady-state junction temperature and pulse power of the power device in the current grid cycle based on actual operating parameters, thermal performance parameters and loss data tables, and also includes the following steps S112.7 and S112.8.

[0108] Step S112.7, fitting the final total loss of the power device in the current grid cycle according to the steady-state junction temperature of the power device in the current grid cycle. Exemplarily, the final total loss of the power device in the current grid cycle may be the total loss fitted at the end of the iteration, or the steady-state junction temperature may be substituted into the above formula (1) to formula (4) to obtain the final total loss of the power device in the current grid cycle.

[0109] Step S112.8, determining the pulse power of the power device in the current grid cycle according to the final total loss, the total duration of the current grid cycle, and the loss duration in the current grid cycle.

[0110] refer to Figure 2 , the pulse power P of the power device in the current grid cycle total The loss duration t in the current grid cycle loss The average power consumption during the period of temperature rise of the power device can correspond to each grid cycle t grid The height of the shaded area in the figure. The pulse power can be understood as a grid cycle t grid The average power consumption in the power grid. During the power grid cycle, the loss mainly occurs in the temperature rise period of the power device. Therefore, P pulse *t loss =P total *t grid Therefore, the pulse power P of the power device in the current grid cycle can be solved using the following formula (6): total :

[0111]

[0112] Step S113 determines the maximum junction temperature of the power device in the current grid cycle according to the steady-state junction temperature, pulse power and power factor of the power device in the current grid cycle, including the following steps S113.1 and S113.2.

[0113] Step S113.1, determining the transient thermal impedance corresponding to the pulse power according to the pulse power and transient thermal impedance data table.

[0114] Exemplarily, the pulse width may be obtained according to the pulse power, and the transient thermal impedance corresponding to the pulse power may be searched from a transient thermal impedance data table according to the pulse width.

[0115] Step S113.2, determining the maximum junction temperature of the power device in the current grid cycle according to the steady-state junction temperature, transient thermal impedance, pulse power and power factor.

[0116] It can be understood that the maximum junction temperature of the power device is fluctuating and greater than the steady-state junction temperature of the power device. Considering the circulating current of the power device, the loss of the power device is mainly related to the power factor in a power grid cycle. Therefore, the maximum junction temperature T of the power device in the current power grid cycle can be solved using the following formula (7): j.max :

[0117] T j.max =T j.av +R th.jh_duty ×P pulse ×cosφ…(7)

[0118] Among them, R th.jh_duty It represents the steady-state thermal impedance of the power device, and cosφ represents the power factor, for example, 1 / 2.

[0119] The above-mentioned discretization method for solving the maximum junction temperature of the power device in each power grid cycle has higher accuracy and less calculation amount, thus further improving the accuracy and real-time performance of the converter derating control.

[0120] Combine the following Figure 4a and Figure 4b A control method for a current converter device according to another embodiment of the present application is described as follows:

[0121] like Figure 4a As shown, the converter device (converter) can implement adaptive dynamic derating control by executing the following steps:

[0122] S401, the converter operates according to the current command current and the current limit current;

[0123] S402, calculating the maximum junction temperature of each power device in the converter in the current grid cycle in real time according to the calculation method of the discretized maximum junction temperature.

[0124] S403, determine whether the current maximum junction temperature calculated in real time exceeds the junction temperature required for derating (limited junction temperature). If so, go to S404; if not, go to S405;

[0125] S404, determining that the converter is in an under-derating state (at this time, the junction temperature is in a risky state), determining that the limiting current of the next grid cycle is equal to k times the current limiting current, where k<1; turning to S401, entering the next grid cycle;

[0126] S405, judging whether the current limiting current is less than the command current; if so, it is determined that the converter is in an over-derating state, and the derating needs to be released, and power generation is performed according to the maximum output capacity of the converter, and the process goes to S406; if not, it means that the converter is in a non-derating state at this time, and the process goes to S407;

[0127] S406, determining that the converter is in an over-derating state, determining that the limiting current of the next grid cycle is equal to m times the current limiting current, where m>1; turning to S401, entering the next grid cycle;

[0128] S407, determine that the converter is in a non-derating state, continue to determine the output current according to the current limiting current, and operate stably; go to S401 to enter the next grid cycle.

[0129] like Figure 4b As shown, the calculation method of the discretized maximum junction temperature in S402 includes the following steps:

[0130] S402.1, obtaining thermal performance parameters of the power device, a loss data table, and the current, DC bus voltage, heat sink temperature, duty cycle, and power factor of the power device in the current grid cycle;

[0131] Specifically, the loss data and transient thermal resistance data of the device can be updated and entered into the memory in advance according to the data in the specification of the power device or the data actually measured in the test;

[0132] S402.2, fitting the conduction loss of the power device in each switching cycle according to the current of the power device in each switching cycle, the assumed value of the steady-state junction temperature, the duty cycle, and the loss data table;

[0133] S402.3, fitting the switching loss of the power device in each switching cycle according to the assumed values ​​of the current, DC bus voltage, steady-state junction temperature of the power device in each switching cycle and the loss data table;

[0134] That is, in each control cycle, the conduction loss and switching loss of the power device in this control cycle are calculated in real time by table lookup based on the voltage and current information fed back by sampling;

[0135] S402.4, fitting the total loss of the power device in the current power grid cycle according to the switching loss and conduction loss of the power device in each switching cycle;

[0136] That is, in each control cycle, according to the current power factor, the loss data in the power frequency cycle is discretized and accumulated, and the corresponding total loss is calculated;

[0137] S402.5, calculate an estimate of the steady-state junction temperature using the heat balance equation based on the total losses, heat sink temperature, and steady-state thermal impedance;

[0138] S402.6, determine whether the difference between the fitted estimated value and the assumed value is greater than the junction temperature difference threshold; if so, go to S402.7; if not, go to S402.8;

[0139] S402.7, taking the estimated value as the assumed value, go to S402.2 to continue iteratively fitting the estimated value of the steady-state junction temperature;

[0140] S402.8, the iteration ends, and the estimated value of the fitted steady-state junction temperature is used as the steady-state junction temperature of the power device in the current grid cycle;

[0141] S402.9, fitting the final total loss of the power device in the current grid cycle according to the steady-state junction temperature of the power device in the current grid cycle;

[0142] Specifically, the total loss fitted at the end of the iteration can be used as the final total loss, or the total loss of the power device in the current power grid cycle can be refitted according to the method of S402.2 to S402.4 as the final total loss;

[0143] S402.10, determining the pulse power of the power device in the current grid cycle according to the final total loss, the total duration of the current grid cycle, and the loss duration in the current grid cycle;

[0144] S402.11, determine the transient thermal impedance corresponding to the pulse power based on the pulse power and transient thermal impedance data table;

[0145] S402.12, determine the maximum junction temperature of the power device in the current grid cycle based on the steady-state junction temperature, transient thermal impedance, pulse power and power factor.

[0146] It should be understood that the above examples are intended to help those skilled in the art understand the embodiments of the present application, rather than to limit the embodiments of the present application to the specific numerical values ​​or specific scenarios illustrated. Those skilled in the art can obviously make various equivalent modifications or changes based on the above examples, and such modifications or changes also fall within the scope of the embodiments of the present application.

[0147] Combination of the above Figures 1 to 4b , describes in detail the control method of the converter device in the embodiment of the present application, and will now be combined with Figure 5 It should be understood that the control device of the converter device in the embodiment of the present application can execute the control method of various converter devices in the aforementioned embodiment of the present application, that is, the specific working process of the following various products can refer to the corresponding process in the aforementioned method embodiment.

[0148] Figure 5 The schematic diagram of the structure of the control device of the converter device in some embodiments of the present application is shown. Figure 5 As shown, the control device 500 of the converter device in the embodiment of the present application includes:

[0149] A first determination module 510 is used to determine the maximum junction temperature of the power device of the converter device in the current grid cycle during the operation of the converter device, wherein the maximum junction temperature is the maximum value of the junction temperature of the power device in the current grid cycle;

[0150] A second determination module 520 is used to determine a derating state of the converter device according to a difference between a maximum junction temperature and a limit junction temperature of the power device, wherein the derating state is used to indicate whether the converter device is operated at a derating and / or to indicate a relationship between an actual derating and an expected derating when the converter device is operated at a derating;

[0151] The third determination module 530 is used to determine the limiting current of the converter device in the next power grid cycle according to the derating state of the converter device, wherein the limiting current is the limiting value of the output current of the converter device.

[0152] Each unit module of the control device 500 of the above-mentioned converter device can respectively execute the corresponding steps in the above-mentioned method embodiment, so each unit module will not be described in detail here. Please refer to the description of the above-mentioned corresponding steps for details.

[0153] It should be noted that the control device 500 of the above-mentioned converter device is embodied in the form of a functional unit. The term "unit" here can be implemented in the form of software and / or hardware, and is not specifically limited to this.

[0154] For example, a "unit" may be a software program, a hardware circuit, or a combination of the two that implements the above functions. The hardware circuit may include an application specific integrated circuit (ASIC), an electronic circuit, a processor (such as a shared processor, a dedicated processor, or a group processor, etc.) and a memory for executing one or more software or firmware programs, a combined logic circuit, and / or other suitable components that support the described functions.

[0155] Therefore, the units of each example described in the embodiments of the present application can be implemented by electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the embodiments of the present application.

[0156] The present application also provides a current conversion device. Figure 6 As shown, the converter device 600 provided in the embodiment of the present application includes: at least one power device 610 ( Figure 6Only one power device is shown in the figure); a controller 620 is connected to the power device 610 and is configured to: during the operation of the converter device 600, determine the maximum junction temperature of the power device 610 in the current grid cycle, wherein the maximum junction temperature is the maximum value of the junction temperature of the power device 610 in the current grid cycle; determine the derating state of the converter device 600 according to the difference between the maximum junction temperature and the limiting junction temperature of the power device 610, wherein the derating state is used to indicate whether the converter device 600 is operated at a derating and / or to indicate the relationship between the actual derating and the expected derating when the converter device 600 is operated at a derating; determine the limiting current of the converter device 600 in the next grid cycle according to the derating state of the power device 610, wherein the limiting current is the limiting value of the output current of the converter device 600.

[0157] In one embodiment, the derating state includes: a non-derating state indicating that the converter device 600 has not yet been derated, and an over-derating state indicating that the converter device 600 is derated and the actual derating is greater than the expected derating. The controller 620 determines the derating state of the converter device 600 according to the difference between the maximum junction temperature and the limiting junction temperature of the power device 610, and is configured to: when the maximum junction temperature of the power device 610 is less than or equal to the limiting junction temperature of the power device 610, determine that the converter device 600 is in the non-derating state or the over-derating state according to the current difference between the current limiting current and the currently received command current; the controller 620 determines the limiting current of the converter device 600 in the next grid cycle according to the derating state of the power device 610, and is configured to: when the converter device 600 is in the non-derating state or the over-derating state, determine that the limiting current of the converter device 600 in the next grid cycle is greater than or equal to the current limiting current.

[0158] In one embodiment, the controller 620 determines whether the converter device 600 is in a non-derating state or an over-derating state based on a current difference between a current limiting current and a currently received command current, and is configured to: when the current difference is less than a current difference threshold, determine that the converter device 600 is in an over-derating state; and / or when the current difference is greater than or equal to the current difference threshold, determine that the converter device 600 is in a non-derating state; when the converter device 600 is in a non-derating state or an over-derating state, the controller 620 determines that the limiting current of the converter device 600 in the next grid cycle is greater than or equal to the current limiting current, and is configured to: when the converter device 600 is in an over-derating state, determine that the limiting current of the converter device 600 in the next grid cycle is greater than the current limiting current; and / or when the converter device 600 is in a non-derating state, determine that the limiting current of the converter device 600 in the next grid cycle is equal to the current limiting current.

[0159] In one embodiment, the derating state includes an under-derating state indicating that the converter device 600 is operating at a reduced rating but the actual derating is less than the expected derating. The controller 620 determines the derating state of the converter device 600 based on the difference between the maximum junction temperature and the limiting junction temperature of the power device 610, and is configured to: when the maximum junction temperature of the power device 610 is greater than the limiting junction temperature of the power device 610, determine that the converter device 600 is in the under-derating state; the controller 620 determines the limiting current of the converter device 600 in the next grid cycle based on the derating state of the power device 610, and is configured to: when the converter device 600 is in the under-derating state, determine that the limiting current of the converter device 600 in the next grid cycle is less than the current limiting current.

[0160] In one embodiment, the controller 620 is further configured to: obtain actual operating parameters of the power device 610 in the current grid cycle; determine a first historical operating condition corresponding to the current operating condition based on the actual operating parameters and the historical operating parameters of the power device 610 under multiple historical operating conditions, wherein the parameter difference between the historical operating parameters of the first historical operating condition and the actual operating parameters is less than the parameter difference between the historical operating parameters of the second historical operating condition and the actual operating parameters, and the second historical operating condition is other historical operating conditions among the multiple historical operating conditions except the first historical operating condition; determine the limiting junction temperature of the power device 610 in the current grid cycle based on the stored maximum junction temperature of the power device 610 under the first historical operating condition.

[0161] In one embodiment, the controller 620 determines a first historical operating condition corresponding to the current operating condition based on actual operating parameters and historical operating parameters of the power device 610 under multiple historical operating conditions, and is configured as follows: when parameter differences between the actual operating parameters and the historical operating parameters under multiple historical operating conditions are greater than a parameter difference threshold, two historical operating conditions are selected from multiple historical operating conditions as two first historical operating conditions corresponding to the current operating condition; the controller 620 determines a limiting junction temperature of the power device 610 in the current grid cycle based on the stored maximum junction temperature of the power device 610 under the first historical operating condition, and is configured as follows: based on the maximum junction temperatures of the two stored first historical operating conditions, interpolate and fit the limiting junction temperature of the power device 610 in the current grid cycle.

[0162] In one embodiment, the controller 620 determines the maximum junction temperature of the power device 610 in the current grid cycle during the operation of the power conversion device 600, and is configured to: obtain the thermal performance parameters, loss data table and actual operating parameters of the power device 610 in the current grid cycle; determine the steady-state junction temperature and pulse power of the power device 610 in the current grid cycle based on the actual operating parameters, thermal performance parameters and loss data table; determine the maximum junction temperature of the power device 610 in the current grid cycle based on the steady-state junction temperature, pulse power and power factor of the power device 610 in the current grid cycle.

[0163] In one embodiment, the thermal performance parameters include a steady-state thermal impedance and a transient thermal impedance data table of the power device 610, and the actual operating parameters include a current, a DC bus voltage, a heat sink temperature, a duty cycle, and a power factor of the power device 610 in each switching cycle in the current grid cycle. The controller 620 determines the steady-state junction temperature and the pulse power of the power device 610 in the current grid cycle according to the actual operating parameters, the thermal performance parameters, and the loss data table, and is configured to: fit the conduction loss of the power device 610 in each switching cycle according to the assumed values ​​of the current and steady-state junction temperature, the duty cycle, and the loss data table of the power device 610 in each switching cycle; and fit the conduction loss of the power device 610 in each switching cycle according to the assumed values ​​of the current, the DC bus voltage, and the steady-state junction temperature of the power device 610 in each switching cycle. The switching loss of the power device 610 in each switching cycle is fitted according to the set values ​​and the loss data table; the total loss of the power device 610 in the current grid cycle is fitted according to the switching loss, conduction loss and power factor of the power device 610 in each switching cycle; the estimated value of the steady-state junction temperature is calculated using the thermal balance equation according to the total loss, the heat sink temperature and the steady-state thermal impedance; when the difference between the estimated value and the assumed value is greater than the junction temperature difference threshold, the estimated value is used as the assumed value, and the estimated value of the steady-state junction temperature is continuously iterated until the difference between the estimated value and the assumed value is less than or equal to the junction temperature difference threshold, and the iteration ends; the steady-state junction temperature of the power device 610 in the current grid cycle is determined according to the estimated value of the steady-state junction temperature fitted at the end of the iteration.

[0164] In one embodiment, the controller 620 determines the steady-state junction temperature and pulse power of the power device 610 in the current grid cycle based on the actual operating parameters, thermal performance parameters and loss data table, and is also configured to: fit the final total loss of the power device 610 in the current grid cycle based on the steady-state junction temperature of the power device 610 in the current grid cycle; determine the pulse power of the power device 610 in the current grid cycle based on the final total loss, the total duration of the current grid cycle and the loss duration in the current grid cycle; the controller 620 determines the maximum junction temperature of the power device 610 in the current grid cycle based on the steady-state junction temperature, pulse power and power factor of the power device 610 in the current grid cycle, and is configured to: determine the transient thermal impedance corresponding to the pulse power based on the pulse power and transient thermal impedance data table; determine the maximum junction temperature of the power device 610 in the current grid cycle based on the steady-state junction temperature, transient thermal impedance, pulse power and power factor.

[0165] Figure 6 This is merely an example of a converter device and does not constitute a limitation on the converter device. The converter device may include more or fewer components than shown in the figure, or a combination of certain components, or different components.

[0166] like Figure 7 As shown, the controller 620 may include at least one processor 621 ( Figure 7 Only one processor is shown in the figure), the converter device 600 may also include a memory 630 and a computer program 640 stored in the memory 630 and executable on at least one processor 621, and when the processor 621 executes the computer program 640, the steps of the control method of the converter device are implemented.

[0167] The processor 621 may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

[0168] In some embodiments, the memory 630 may be an internal storage unit of the converter device 600, such as a hard disk or memory of the converter device 600. In other embodiments, the memory 630 may also be an external storage device of the converter device 600, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the converter device 600. Further, the memory 630 may also include both an internal storage unit of the converter device 600 and an external storage device. The memory 630 may be used to store thermal performance parameters, loss data tables, etc. of power devices for processor call; the memory 630 is also used to store operating systems, application programs, boot loaders, data, and other programs, such as program codes of computer programs. The memory 630 may also be used to temporarily store data that has been output or is to be output.

[0169] The present application also provides a computer program product, which, when executed by the processor 621, implements the control method of the converter device of any method embodiment in the present application.

[0170] The computer program product may be stored in a memory, for example, a program, which is finally converted into an executable target file that can be executed by the processor 621 after preprocessing, compiling, assembling and linking.

[0171] The present application also provides a computer-readable storage medium on which a computer program is stored, and when the computer program is executed by a computer, the control method of the converter device of any method embodiment of the present application is implemented. The computer program can be a high-level language program or an executable target program.

[0172] The computer-readable storage medium is, for example, a memory. The memory may be a volatile memory or a nonvolatile memory, or the memory may include both a volatile memory and a nonvolatile memory. Among them, the nonvolatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link DRAM (SLDRAM), and direct memory bus random access memory (DRRAM).

[0173] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can be represented by: a, b, c, ab, ac, bc, or abc, where a, b, c can be single or multiple.

[0174] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0175] Those of ordinary skill in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0176] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0177] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic; for example, the division of units is only a logical function division, and there may be other division methods in actual implementation; for example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0178] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0179] In addition, each functional unit in each embodiment of the present application may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0180] The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A current conversion device, characterized in that: include: Power devices; A controller is connected to the power device and is configured to: During the operation of the power conversion device, determining the maximum junction temperature of the power device in the current power grid cycle, wherein the maximum junction temperature is the maximum value of the junction temperature of the power device in the current power grid cycle; Determining a derating state of the converter device according to a difference between the maximum junction temperature and the limit junction temperature of the power device, wherein the derating state is used to indicate whether the converter device is operated at a derating and / or to indicate a relationship between an actual derating and an expected derating when the converter device is operated at a derating; According to the derating state of the converter device, a limiting current of the converter device in the next power grid cycle is determined, wherein the limiting current is a limiting value of the output current of the converter device.

2. The current conversion device according to claim 1, characterized in that: The derating state includes: a non-derating state indicating that the converter device has not been operated at a derating state, and an over-derating state indicating that the converter device is operated at a derating state and the actual derating is greater than the expected derating. The controller determines the derating state of the converter device according to the difference between the maximum junction temperature and the limit junction temperature of the power device, and is configured as follows: When the maximum junction temperature of the power device is less than the limit junction temperature of the power device, determining that the converter device is in a non-derating state or an over-derating state according to a current difference between a current limit current and a currently received command current; The controller determines the limiting current of the converter device in the next power grid cycle according to the derating state of the converter device, and is configured as follows: When the converter device is in a non-derating state or an over-derating state, it is determined that the limiting current of the converter device in the next power grid cycle is greater than or equal to the current limiting current.

3. The current conversion device according to claim 2, characterized in that: The controller determines whether the current conversion device is in a non-derating state or an over-derating state according to a current difference between a current limiting current and a currently received command current, and is configured as follows: When the current difference is less than the current difference threshold, determining that the current conversion device is in an over-derating state; and / or When the current difference is greater than or equal to the current difference threshold, determining that the current conversion device is in a non-derating state; The controller determines, when the converter device is in a non-derating state or an over-derating state, that a limiting current of the converter device in a next power grid cycle is greater than or equal to a current limiting current, and is configured as follows: When the converter device is in an over-derating state, determining that a limiting current of the converter device in a next power grid cycle is greater than a current limiting current; and / or When the converter device is in a non-derating state, it is determined that the limiting current of the converter device in the next power grid cycle is equal to the current limiting current.

4. The current conversion device according to claim 1, characterized in that: The derating state includes an under-derating state indicating that the converter device is running at a derating value but the actual derating value is less than the expected derating value. The controller determines the derating state of the converter device according to the difference between the maximum junction temperature and the limiting junction temperature of the power device, and is configured as follows: When the maximum junction temperature of the power device is greater than or equal to the limit junction temperature of the power device, determining that the converter device is in an under-derating state; The controller determines the limiting current of the converter device in the next power grid cycle according to the derating state of the converter device, and is configured as follows: When the converter device is in an under-derating state, it is determined that the limiting current of the converter device in the next power grid cycle is less than the current limiting current.

5. The current conversion device according to any one of claims 1 to 4, characterized in that: The controller is further configured to: Obtaining actual operating parameters of the power device in the current power grid cycle; Determine a first historical operating condition corresponding to the current operating condition according to the actual operating parameter and the historical operating parameters of the power device under multiple historical operating conditions, wherein a parameter difference between the historical operating parameters of the first historical operating condition and the actual operating parameters is less than a parameter difference between the historical operating parameters of a second historical operating condition and the actual operating parameters, and the second historical operating condition is a historical operating condition other than the first historical operating condition among the multiple historical operating conditions; A limit junction temperature of the power device in a current grid cycle is determined according to the stored maximum junction temperature of the power device under the first historical operating condition.

6. The current conversion device according to claim 5, characterized in that: The controller determines a first historical operating condition corresponding to the current operating condition according to the actual operating parameter and the historical operating parameters of the power device under a plurality of historical operating conditions, and is configured as follows: When the parameter differences between the actual operating parameters and the historical operating parameters under the multiple historical operating conditions are greater than the parameter difference threshold, two historical operating conditions are selected from the multiple historical operating conditions as two first historical operating conditions corresponding to the current operating condition; The controller determines the limit junction temperature of the power device in the current grid cycle according to the stored maximum junction temperature of the power device under the first historical operating condition, and is configured as follows: According to the stored maximum junction temperatures of the two first historical operating conditions, a limit junction temperature of the power device in the current grid cycle is interpolated and fitted.

7. The current conversion device according to any one of claims 1 to 4, characterized in that: During the operation of the converter device, the controller determines the maximum junction temperature of the power device in the current grid cycle, and is configured as follows: Obtaining thermal performance parameters, loss data table and actual operating parameters of the power device in the current power grid cycle; Determining the steady-state junction temperature and pulse power of the power device in the current grid cycle according to the actual operating parameters, the thermal performance parameters and the loss data table; The maximum junction temperature of the power device in the current grid cycle is determined according to the steady-state junction temperature of the power device in the current grid cycle, the pulse power and the power factor.

8. The current conversion device according to claim 7, characterized in that: The thermal performance parameters include a steady-state thermal impedance and a transient thermal impedance data table of the power device, the actual operating parameters include a current, a DC bus voltage, a heat sink temperature, a duty cycle, and a power factor of each switching cycle of the power device in a current grid cycle, and the controller determines a steady-state junction temperature and a pulse power of the power device in a current grid cycle according to the actual operating parameters, the thermal performance parameters, and the loss data table, and is configured as follows: Fitting the conduction loss of the power device in each switching cycle according to the current of the power device in each switching cycle, the assumed value of the steady-state junction temperature, the duty cycle, and the loss data table; Fitting the switching loss of the power device in each switching cycle according to the current of the power device in each switching cycle, the DC bus voltage, the assumed value of the steady-state junction temperature and the loss data table; Fitting the total loss of the power device in the current power grid cycle according to the switching loss and the conduction loss of the power device in each switching cycle; According to the total loss, the heat sink temperature and the steady-state thermal impedance, a thermal balance equation is used to calculate an estimated value of the steady-state junction temperature; In the case where the difference between the estimated value and the assumed value is greater than the junction temperature difference threshold, the estimated value is used as the assumed value, and the estimated value of the steady-state junction temperature is continuously iterated to fit until the difference between the estimated value and the assumed value is less than or equal to the junction temperature difference threshold, and the iteration ends; The steady-state junction temperature of the power device in the current power grid cycle is determined according to the estimated value of the fitted steady-state junction temperature at the end of the iteration.

9. The current conversion device according to claim 8, characterized in that: The controller determines the steady-state junction temperature and pulse power of the power device in the current grid cycle according to the actual operating parameters, the thermal performance parameters and the loss data table, and is further configured as: Fitting the final total loss of the power device in the current grid cycle according to the steady-state junction temperature of the power device in the current grid cycle; Determining the pulse power of the power device in the current grid cycle according to the final total loss, the total duration of the current grid cycle, and the loss duration in the current grid cycle; The controller determines the maximum junction temperature of the power device in the current grid cycle according to the steady-state junction temperature of the power device in the current grid cycle, the pulse power and the power factor, and is configured as follows: Determining the transient thermal impedance corresponding to the pulse power according to the pulse power and the transient thermal impedance data table; The maximum junction temperature of the power device in a current grid cycle is determined according to the steady-state junction temperature, the transient thermal impedance, the pulse power and the power factor.

10. A control method for a current conversion device, characterized in that: include: During the operation of the converter device, determining a maximum junction temperature of a power device of the converter device in a current grid cycle, wherein the maximum junction temperature is a maximum value of the junction temperature of the power device in the current grid cycle; Determining a derating state of the converter device according to a difference between the maximum junction temperature and the limit junction temperature of the power device, wherein the derating state is used to indicate whether the converter device is operated at a derating and / or to indicate a relationship between an actual derating and an expected derating when the converter device is operated at a derating; According to the derating state of the converter device, a limiting current of the converter device in the next power grid cycle is determined, wherein the limiting current is a limiting value of the output current of the converter device.

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