Thermal protection method and device of inverter, electronic equipment and storage medium

Abstract

The invention provides a thermal protection method and device for an inverter, electronic equipment and a storage medium, and the method comprises the steps: obtaining the current monitoring data of the inverter, and determining at least one initial switching state sequence according to the electrical monitoring data, the initial switching state sequences are used for representing a plurality of historical switching state combinations in the inverter in the last control period, and the historical switching state combinations comprise switching states of a plurality of levels, calculating the junction temperature cost of each initial switching state sequence corresponding to the superheater, the calculation of the junction temperature cost is obtained based on the total energy loss of all superheater devices and the limited junction temperature of a preset device, and a target switching state sequence of the control period is determined from at least one initial switching state sequence according to at least one junction temperature cost so as to adjust the output of pulse width modulation waves to control the inverter; by calculating the junction temperature cost of the superheater device, the thermal overload risk of the switch equipment can be reduced, and the three-phase current and the three-phase voltage are kept unchanged.

Description

Technical Field

[0001] The present application relates to the technical field of inverters, and in particular to a thermal protection method, device, electronic equipment and storage medium for an inverter. Background Art

[0002] Recently, the penetration of large-scale renewable energy systems has been increasing to reduce the cost of generating kilowatt-hours. Multilevel inverters are the most suitable solution for grid-connected large-scale renewable energy systems. Among multilevel inverters, the T-type inverter has been proven to be a highly efficient system. The main advantage of the T-type inverter is the lower rated voltage of the power switching devices (insulated gate bipolar transistors IGBTs) used, because the peak reverse voltage (PIV) of the two switches at the neutral point (NP) is only half of that required by the neutral point clamped (NPC) inverter. In addition, the structure of the T-type inverter reduces the conduction loss compared to the NPC inverter of the same rating. In the T-type inverter, the power loss of the switching device is dissipated in the form of heat, and the heat sink is used to dissipate this heat into the air. However, the T-type inverter, which is the grid-connected interface, may render the entire large-scale renewable energy system unusable in the event of a fault. Therefore, when designing and developing the T-type inverter, emphasis should be placed on reliability to avoid grid interference and power fluctuations.

[0003] In the related art, the power switching device IGBT is composed of multiple layers of different materials, which may have different thermal expansion coefficients. Continuous overload and power cycling can cause cracks, gaps and delamination in the device components, thereby increasing the thermal resistance. As a result, the device junction temperature will increase even under normal operating and cooling conditions. In high-power applications, the failure of the forced cooling system is the main cause of thermal overload. This thermal stress is the main cause of system failure, thereby shortening the service life and reducing system reliability. Summary of the invention

[0004] The present invention provides a thermal protection method, device, electronic equipment and storage medium for an inverter to solve the technical problem that the thermal overload of the inverter causes failure of a renewable energy system.

[0005] In one embodiment of the present application, the present application provides a thermal protection method for an inverter, comprising: obtaining current monitoring data of the inverter, the current monitoring data including electrical monitoring data and measured temperatures of multiple switching devices; determining at least one initial switch state sequence based on the electrical monitoring data, the initial switch state sequence being used to characterize multiple historical switch state combinations in the inverter in the previous control cycle, the historical switch state combinations including switch states of multiple levels; calculating the junction temperature cost of each initial switch state sequence corresponding to an overheating device, the junction temperature cost being calculated based on the total energy loss of all overheating devices and a preset device limit junction temperature, the overheating device being used to characterize a switching device whose measured temperature is greater than or equal to a preset temperature threshold; determining a target switch state sequence for this control cycle from at least one initial switch state sequence based on at least one junction temperature cost, so as to adjust the output of a pulse width modulation wave to control the inverter.

[0006] In one embodiment of the present application, the junction temperature cost of the initial switching state sequence corresponding to the overheating device is calculated, including: determining the predicted junction temperature of the overheating device based on the measured temperature and heat generation temperature of the overheating device; determining the initial cost of the overheating device based on the difference between the preset device limit junction temperature of the overheating device and the predicted junction temperature; and determining the sum of the initial costs of all overheating devices as the junction temperature cost of the initial switching state sequence; wherein the heat generation temperature is obtained based on the total power loss and the Thevenin equivalent thermal impedance of the overheating device, and the total power loss and the equivalent thermal impedance are obtained based on the initial switching state sequence and preset electrical parameters corresponding to the inverter.

[0007] In one embodiment of the present application, the determination of the total power loss of the overheating device includes: determining the conduction power loss based on the initial switch state sequence, the first electrical parameter of the diode and the second electrical parameter of the overheating device; determining the switching energy loss based on the number of switch transitions of the overheating device in the initial switch state sequence; determining the sum of the conduction power loss and the switching energy loss as the total power loss of the overheating device; wherein the preset electrical parameters include the first electrical parameter and the second electrical parameter, and the diode is connected in parallel with the overheating device.

[0008] In one embodiment of the present application, the switching energy loss is determined based on the number of switch transitions of the overheating device in the initial switch state sequence, including: determining the dissipated energy at each switch transition and the reverse recovery energy dissipated during diode switching based on the number of transitions of the overheating device in the initial switch state sequence; determining the switching energy loss based on the average value between the total amount of the dissipated energy and the total amount of the reverse recovery energy; wherein the switch transition includes turning on or off the overheating device.

[0009] In one embodiment of the present application, determining a target switch state sequence from at least one initial switch state sequence according to at least one junction temperature cost includes: determining an initial switch state sequence corresponding to a minimum junction temperature cost as a first candidate switch state sequence; calculating a DC side voltage difference corresponding to the first candidate switch state sequence according to DC side electrical data, wherein the electrical monitoring data includes the DC side electrical data;

[0010] If the DC side voltage difference is less than or equal to the preset voltage threshold, the first candidate switch state sequence is determined as the target switch state sequence; if the DC side voltage difference is greater than the preset voltage threshold, the initial switch state sequence corresponding to the next smallest junction temperature cost is determined as the first candidate switch state sequence, and the step of calculating the DC side voltage difference corresponding to the first candidate switch state sequence according to the DC side electrical data is repeated, and if the DC side voltage difference is greater than the preset voltage threshold, the initial switch state sequence corresponding to the next smallest junction temperature cost is determined as the first candidate switch state sequence, until the DC side voltage difference is less than or equal to the preset voltage threshold, and the first candidate switch state sequence is determined as the target switch state sequence.

[0011] In one embodiment of the present application, a target switch state sequence is determined from at least one initial switch state sequence based on at least one junction temperature cost, and also includes: calculating the DC side voltage difference corresponding to each of the initial switch state sequences based on the DC side electrical data, and the electrical monitoring data includes the DC side electrical data; if the DC side voltage difference corresponding to an initial switch state sequence is less than or equal to a preset voltage threshold, then determining the initial switch state sequence as a second candidate switch state sequence; and determining the second candidate switch state sequence corresponding to the minimum junction temperature cost as the target switch state sequence.

[0012] In one embodiment of the present application, determining the DC side voltage difference includes: calculating the initial DC side voltage of each historical switching state based on preset electrical parameters of the inverter, the historical switching state being obtained based on the initial switching state sequence or the first candidate switching state sequence; determining the predicted DC side voltage based on the average value of each of the initial DC side voltages; and determining the difference between the predicted DC side voltage and the measured DC side voltage in the DC side electrical data as the DC side voltage difference.

[0013] In one embodiment of the present application, the present application provides a thermal protection device for an inverter, including: a data acquisition module, used to acquire current monitoring data of the inverter, the current monitoring data including electrical monitoring data and measured temperatures of multiple switching devices; an initial sequence determination module, used to determine at least one initial switch state sequence according to the electrical monitoring data, the initial switch state sequence being used to characterize multiple historical switch state combinations in the inverter in the previous control cycle, the historical switch state combinations including switch states of multiple levels; a temperature control processing module, used to calculate the junction temperature cost of each initial switch state sequence corresponding to an overheating device, the junction temperature cost being calculated based on the total energy loss of all overheating devices and a preset device limit junction temperature, the overheating device being used to characterize a switch device whose measured temperature is greater than or equal to a preset temperature threshold; a target sequence determination module, used to determine a target switch state sequence of this control cycle from at least one initial switch state sequence according to at least one junction temperature cost, so as to adjust the output of a pulse width modulation wave to control the inverter.

[0014] In one embodiment of the present application, the present application provides an electronic device, which includes: one or more processors; a storage device for storing one or more programs, when the one or more programs are executed by the one or more processors, the electronic device implements the thermal protection method of the inverter as described in any of the above embodiments.

[0015] In one embodiment of the present application, the present application provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor of a computer, the computer executes the thermal protection method for the inverter described in any of the above embodiments.

[0016] Beneficial effects of embodiments of the present invention: The present invention provides a thermal protection method, device, electronic device and storage medium for an inverter. The embodiments of the present invention calculate the junction temperature cost of the overheating device, thereby selecting a target switching state sequence from at least one initial switching state sequence, thereby reducing the risk of thermal overload of the switching device and keeping the output three-phase current and three-phase voltage unchanged, thereby reducing the probability of failure of the renewable energy system.

[0017] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the present application, and together with the specification, are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0019] Figure 1 A schematic diagram showing an exemplary system architecture to which the technical solution of the embodiments of the present application can be applied;

[0020] Figure 2 A schematic diagram of a process flow of a thermal protection method for an inverter according to an embodiment of the present application is shown;

[0021] Figure 3 A power circuit of a T-type three-level inverter according to an embodiment of the present application is shown;

[0022] Figure 4 A voltage space vector diagram of a T-type three-level inverter according to an embodiment of the present application is shown;

[0023] Figure 5 A vector composite diagram according to an embodiment of the present application is shown;

[0024] Figure 6 A schematic diagram of an implementation process of a thermal protection method for an inverter according to an embodiment of the present application is shown;

[0025] Figure 7 A block diagram of a thermal protection device for an inverter according to an embodiment of the present application is shown;

[0026] Figure 8 A schematic diagram of the structure of a computer system suitable for implementing an electronic device of an embodiment of the present application is shown. DETAILED DESCRIPTION

[0027] The following describes the embodiments of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0028] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present application, and thus the drawings only show components related to the present application rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the form, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0029] In the following description, a large number of details are discussed to provide a more thorough explanation of the embodiments of the present application. However, it is obvious to those skilled in the art that the embodiments of the present application can be implemented without these specific details. In other embodiments, well-known structures and devices are shown in the form of block diagrams rather than in detail to avoid making the embodiments of the present application difficult to understand.

[0030] See also Figure 1 , Figure 1 A schematic diagram of an exemplary system architecture to which the technical solution of the embodiment of the present application can be applied is shown. Figure 1 As shown, the system architecture may include an AC grid 101, an inverter power circuit 102, a DC load 103, and an inverter control circuit 104. The inverter control circuit 104 performs thermal protection on the inverter power circuit 102 based on the collected current monitoring data.

[0031] Exemplarily, the control circuit 104 of the inverter obtains current monitoring data of the inverter, the current monitoring data including electrical monitoring data and measured temperatures of multiple switching devices; determines at least one initial switching state sequence based on the electrical monitoring data, the initial switching state sequence is used to characterize multiple historical switching state combinations in the inverter in the previous control cycle, the historical switching state combinations include switching states of multiple levels; calculates the junction temperature cost of each initial switching state sequence corresponding to the overheating device, the junction temperature cost is calculated based on the total energy loss of all overheating devices and the preset device limit junction temperature, the overheating device is used to characterize the switching device whose measured temperature is greater than or equal to the preset temperature threshold; determines the target switching state sequence of this control cycle from at least one initial switching state sequence based on at least one junction temperature cost, so as to adjust the output of the pulse width modulation wave to control the inverter.

[0032] In the related art, there is a technical problem that thermal overload of the inverter causes failure of the renewable energy system.

[0033] In order to solve the above technical problems, the present application provides a thermal protection method, device, electronic device and storage medium for an inverter. The implementation details of the technical solution of the embodiment of the present application are elaborated in detail below.

[0034] See also Figure 2 , Figure 2FIG. 1 is a flow chart of a thermal protection method for an inverter according to an embodiment of the present application. Figure 2 As shown, in an exemplary embodiment, the thermal protection method of the inverter includes at least steps S210 to S240, which are described in detail as follows:

[0035] Step S210, obtaining current monitoring data of the inverter.

[0036] Among them, the current monitoring data includes electrical monitoring data and measured temperatures of multiple switching devices.

[0037] In one embodiment of the present application, the inverter comprises a T-type three-level inverter. The switch device comprises an insulated gate bipolar transistor (IGBT).

[0038] In one embodiment of the present application, the control circuit of the inverter includes a power module, a digital signal processing (DSP) core module, a sampling module, a data storage module and an IGBT driving module.

[0039] In one embodiment of the present application, the sampling module collects electrical monitoring data and sends it to the DSP core module; the DSP core module obtains the output of the pulse width modulation wave based on the electrical monitoring data and sends it to the IGBT drive module; the IGBT drive module sends the control signal of the pulse width modulation wave to the power circuit.

[0040] In one embodiment of the present application, the electrical monitoring data includes DC side electrical data and AC side electrical data.

[0041] In one embodiment of the present application, the DC side electrical data includes the measured DC side voltage and the measured DC side current. The AC side electrical data includes the three-phase voltage and the three-phase current.

[0042] Step S220: determining at least one initial switch state sequence according to the electrical monitoring data.

[0043] The initial switch state sequence is used to represent a plurality of historical switch state combinations in the inverter in the previous control cycle, and the historical switch state combinations include switch states of multiple levels.

[0044] In one embodiment of the present application, at least one initial switch state sequence is determined based on electrical monitoring data, including: performing Clarke transform on the three-phase voltage in the AC side electrical data to obtain a transformation voltage, and determining a reference voltage vector based on the transformation voltage, the reference voltage vector being synthesized based on multiple basic voltage vectors; determining a large sector where the reference voltage vector is located based on a comparison result between each basic voltage vector and a preset reference threshold; determining a small sector where the reference voltage vector is located based on the transformation voltage, the measured DC side voltage in the DC side electrical data, and a phase angle obtained from the transformation voltage; and determining at least one initial switch state sequence based on the large sector and the small sector.

[0045] In one embodiment of the present application, see Figure 3 , Figure 3 FIG. 2 shows a power circuit of a T-type three-level inverter according to an embodiment of the present application. Figure 3 As shown, the power circuit includes multiple switching devices, such as IGBTs, and each IGBT housing is equipped with a temperature sensor; the power circuit also includes an LCL filter circuit, such as an inductor L f1 , L f2 , capacitor C f ; The T-type three-level inverter includes three phases, such as phase A, phase B and phase C; each phase includes four IGBTs, such as the four IGBTs of phase A are identified by Sa1, Sa2, Sa3, and Sa4; each phase (A, B, C) in the T-type three-level inverter has three possible states: P, O or N, and the output pin of the central processing unit (CPU) of the inverter control circuit is connected to the control end of the IGBT to control the on or off, and the inverter output level is shown in Table 1:

[0046] Table 1 Three levels of output of T-type three-level inverter

[0047]

[0048] In one embodiment of the present application, the first step of space vector modulation is to convert the three-phase voltage, such as U A , U B , U C , through Clarke transformation, it is converted from three-phase coordinates to α-β stationary coordinate system, such as U α , U β , thus judging by U α and U β The current sector where the reference voltage vector is located, U DC To measure the DC side voltage.

[0049] In one embodiment of the present application, see Figure 4 , Figure 4FIG. 4 shows a voltage space vector diagram of a T-type three-level inverter according to an embodiment of the present application. Figure 4 As shown, the entire voltage space is divided into 6 large sectors, such as large sector I to large sector IV, and each large sector is divided into 6 small sectors, such as small sector 1 to small sector 6; the reference voltage vector U ref The current sector is completely composed of U α and U β The reference vector U is determined by using the three nearest basic voltage vectors (N3V) to synthesize the reference vector. ref It is composed of U1, U2 and U3. The basic voltage vectors are as follows:

[0050]

[0051] Among them, U1 is the first basic voltage vector, U β is the β-axis component in the conversion voltage, U2 is the second basic voltage vector, U α is the α-axis component in the conversion voltage, and U3 is the second basic voltage vector.

[0052] In one embodiment of the present application, the preset reference threshold value can be set to zero. If U1>0, then A=1, otherwise A=0; if U2>0, then B=1, otherwise B=0; if U3>0, then C=1, otherwise C=0; let N=4*C+2*B+A, then the reference voltage vector U can be calculated by Table 2 ref The large sector where it is located.

[0053] Table 2 Reference voltage vector U ref The large sector

[0054] N 3 1 5 4 6 2 Sector I II III IV V VI

[0055] In one embodiment of the present application, the reference voltage vector U ref The small sectors are as follows:

[0056]

[0057] Where θ is the phase angle, U β is the α-axis component of the conversion voltage, U α is the β-axis component of the conversion voltage, U DC To measure the DC side voltage.

[0058] In one embodiment of the present application, the phase angle θ is based on U α and U β get.

[0059] In one embodiment of the present application, see Figure 5 , Figure 5FIG. 2 shows a vector synthesis diagram according to an embodiment of the present application. Figure 5 As shown, with reference voltage vector U ref Taking the situation where the circuit falls into large sector 1 and small sector 5 as an example, the initial switching state sequence can be ONN-PNN-PON-POO-PON-PNN-ONN, or POO-PNN-PON-ONN-PON-PNN-POO, etc. The reference voltage vector synthesized by each initial switching state sequence is the same, but the degree of IGBT heating and the harmonics generated by the circuit are different.

[0060] In one embodiment of the present application, the available number of initial switch state sequences depends on the current sector of the voltage reference vector.

[0061] In one embodiment of the present application, as shown in ONN-PNN-PON-POO-PON-PNN-ONN, ONN is a historical switch state, O is the switch state corresponding to phase A, N is the switch state corresponding to phase B, and N is the switch state corresponding to phase C.

[0062] Step S230 , calculating the junction temperature cost of each initial switch state sequence corresponding to the overheating device.

[0063] The junction temperature cost is calculated based on the total energy loss of all overheating devices and the preset device limit junction temperature. The overheating device is used to characterize the switching device whose measured temperature is greater than or equal to the preset temperature threshold.

[0064] In one embodiment of the present application, the junction temperature cost of the initial switching state sequence corresponding to the overheating device is calculated, including: determining the predicted junction temperature of the overheating device based on the measured temperature and the heat generation temperature of the overheating device; determining the initial cost of the overheating device based on the difference between the preset device limit junction temperature of the overheating device and the predicted junction temperature; and determining the sum of the initial costs of all overheating devices as the junction temperature cost of the initial switching state sequence; wherein the heat generation temperature is obtained based on the total power loss and the Thevenin equivalent thermal impedance of the overheating device, and the total power loss and the equivalent thermal impedance are obtained based on the initial switching state sequence and preset electrical parameters corresponding to the inverter.

[0065] In one embodiment of the present application, the total energy loss is measured by measuring the temperature and the heat generation temperature.

[0066] In one embodiment of the present application, the heat generation temperature is obtained according to the product of the total power loss of the overheating device and the equivalent thermal impedance.

[0067] In one embodiment of the present application, the junction temperature cost is determined as follows:

[0068]

[0069] Where F(i) is the junction temperature cost of the i-th initial switch state sequence, N is the number of overheated devices in this control cycle, is the measured temperature of the nth overheated device, is the total power loss of the nth overheated device, is the Thevenin equivalent thermal impedance of the nth overheated device, The preset device limit junction temperature for the nth overheated device.

[0070] In one embodiment of the present application, if the predicted junction temperature of an overheating device is equal to the preset device limit junction temperature, the initial cost of the overheating device is zero.

[0071] In one embodiment of the present application,

[0072] In one embodiment of the present application, the power loss of the switching device appears in the form of heat dissipation by a heat sink, and the total power loss of an overheating device is as follows:

[0073] P loss,device =P con,device +P sw,device Formula (4)

[0074] Among them, P loss,device is the total power loss, P con,device is the conduction power loss, P sw,device is the switching energy loss;

[0075] In one embodiment of the present application, determining the total power loss of an overheating device includes: determining the conduction power loss based on an initial switching state sequence, a first electrical parameter of a diode, and a second electrical parameter of the overheating device; determining the switching energy loss based on the number of switching transitions of the overheating device in the initial switching state sequence; determining the sum of the conduction power loss and the switching energy loss as the total power loss of the overheating device; wherein the preset electrical parameters include the first electrical parameter and the second electrical parameter, and the diode is connected in parallel with the overheating device.

[0076] In one embodiment of the present application, the conduction power loss of an overheating device is as follows:

[0077]

[0078] Among them, P con,device is the conduction power loss, P con,IGBT is the conduction loss of the overheated device, P con,diode is the conduction loss of the diode, T S For this control cycle, U IGBT is the on-state voltage of the overheated device, I F is the forward current of the IGBT or diode, R IGBT is the dynamic resistance of the overheated device, UD is the forward voltage of the diode, R D is the dynamic resistance of the diode.

[0079] In one embodiment of the present application, the first electrical parameter includes the on-state voltage of the diode, the forward current of the diode, and the dynamic resistance of the diode; the second electrical parameter includes the on-state voltage of the overheating device, the dynamic resistance of the overheating device, and the forward current of the diode. The first electrical parameter and the second electrical parameter can be queried through the manual information corresponding to the inverter after the model of the diode and the model of the overheating device are determined.

[0080] In one embodiment of the present application, the switching energy loss is determined based on the number of switching transitions of the overheating device in the initial switching state sequence, including: determining the dissipated energy at each switching transition and the reverse recovery energy dissipated during diode switching based on the number of transitions of the overheating device in the initial switching state sequence; determining the switching energy loss based on the average value between the total amount of dissipated energy and the total amount of reverse recovery energy; wherein the switching transition includes turning on or off the overheating device.

[0081] In one embodiment of the present application, the switching energy loss of an overheating device is as follows:

[0082]

[0083] Among them, P sw,device is the switching energy loss, P sw,IGBT is the switching power loss of the overheated device, P sw,diode is the switching power loss of the diode, T S is the control cycle, m is the switching times of the overheating device, E ON,j is the energy dissipated when the overheating device is turned on for the jth time, E OFF,j is the energy dissipated when the overheating device is turned off for the jth time, E RR,j is the reverse recovery energy dissipated by the diode during the jth switching, I F is the forward current of the overheating device or diode, and U is the voltage drop during the switch conversion.

[0084] In one embodiment of the present application, the electrical load of the switching device causes power loss, thereby causing thermal overload of the switching device and increasing the junction temperature of the switching device. The IGBT thermal model uses a reduced-order Foster thermal network model, and the Thevenin equivalent thermal impedance between the junction and the heat sink is as follows:

[0085]

[0086] Among them, Z th is the Thevenin equivalent thermal impedance, k is the model order, R nis the nth level thermal resistance, τ is the model time constant, and t is the time.

[0087] In one embodiment of the present application, the model time constant τ=R th C th Among them, R th is Thevenin equivalent thermal resistance, C th is the Thevenin equivalent capacitance.

[0088] In one embodiment of the present application, equation (7) is discretized as follows:

[0089]

[0090] Among them, Z th is the Thevenin equivalent thermal impedance, R n is the nth level thermal resistance, T S is the control period, and τ is the model time constant.

[0091] Step S240, determining a target switch state sequence of the current control cycle from at least one initial switch state sequence according to at least one junction temperature cost, so as to adjust the output of the pulse width modulation wave to control the inverter.

[0092] In one embodiment of the present application, a target switch state sequence is determined from at least one initial switch state sequence based on at least one junction temperature cost, including: determining the initial switch state sequence corresponding to the minimum junction temperature cost as the first candidate switch state sequence; calculating the DC side voltage difference corresponding to the first candidate switch state sequence based on the DC side electrical data, the electrical monitoring data including the DC side electrical data; if the DC side voltage difference is less than or equal to a preset voltage threshold, determining the first candidate switch state sequence as the target switch state sequence; if the DC side voltage difference is greater than the preset voltage threshold, determining the initial switch state sequence corresponding to the next smallest junction temperature cost as the first candidate switch state sequence, and repeatedly performing the steps of calculating the DC side voltage difference corresponding to the first candidate switch state sequence based on the DC side electrical data, and if the DC side voltage difference is greater than the preset voltage threshold, determining the initial switch state sequence corresponding to the next smallest junction temperature cost as the first candidate switch state sequence, until the DC side voltage difference is less than or equal to the preset voltage threshold, and determining the first candidate switch state sequence as the target switch state sequence.

[0093] In one embodiment of the present application, the second smallest junction temperature cost is used to represent the smallest junction temperature cost among the remaining initial switch state sequences except the switch state sequence selected as the first candidate switch state sequence.

[0094] In one embodiment of the present application, a target switch state sequence is determined from at least one initial switch state sequence based on at least one junction temperature cost, and also includes: calculating the DC side voltage difference corresponding to each initial switch state sequence based on the DC side electrical data, and the electrical monitoring data includes the DC side electrical data; if the DC side voltage difference corresponding to an initial switch state sequence is less than or equal to a preset voltage threshold, the initial switch state sequence is determined as the second candidate switch state sequence; and the second candidate switch state sequence corresponding to the minimum junction temperature cost is determined as the target switch state sequence.

[0095] In one embodiment of the present application, determining the DC side voltage difference includes: calculating the initial DC side voltage of each historical switching state based on preset electrical parameters of the inverter, the historical switching state being obtained based on an initial switching state sequence or a first candidate switching state sequence; determining a predicted DC side voltage based on an average value of each initial DC side voltage; and determining the difference between the predicted DC side voltage and the measured DC side voltage in the DC side electrical data as the DC side voltage difference.

[0096] In one embodiment of the present application, in each control cycle, the predicted junction temperature is estimated for all possible initial switch state sequences of the current sector, the minimum junction temperature cost is calculated, and the initial switch state sequence corresponding to the minimum junction temperature cost is determined as the first candidate switch state sequence. DC , that is, if the calculated predicted DC side voltage of the first candidate switch state sequence selected in this control cycle minus the measured DC side voltage corresponding to the previous control cycle exceeds the preset voltage threshold, the first candidate switch state sequence should be modified to keep the DC side voltage difference within the voltage threshold.

[0097] In one embodiment of the present application, the output of the pulse width modulation wave is adjusted to control the inverter, including: determining the device action time of each switching device according to the target switch state sequence, the conversion voltage and the measured DC side voltage; and controlling the output of the pulse width modulation wave according to each action time to control the inverter.

[0098] In one embodiment of the present application, the device action time of each switching device is determined according to the target switch state sequence, the conversion voltage and the measured DC side voltage, including: determining the vector action time corresponding to each basic voltage vector from a preset sector-action time mapping relationship according to the current sector, the current sector and each basic voltage vector are obtained based on AC side electrical data and DC side electrical data; determining the device conduction time of each switching device according to each vector action time, the target switch state sequence and the current sector, and a preset sector-conduction time mapping relationship.

[0099] In one embodiment of the present application, some preset sector-action time mapping relationships are shown in Table 3:

[0100] Table 3 Some preset sector-action time mapping relationships

[0101]

[0102] Among them, T a is the vector action time corresponding to the first basic voltage vector, T b is the vector action time corresponding to the second basic voltage vector, T c is the vector action time corresponding to the third basic voltage vector, and m is the voltage reference.

[0103] In one embodiment of the present application, the voltage reference is as follows:

[0104]

[0105] Where, m is the voltage reference, U α is the α-axis component of the conversion voltage, U β is the β-axis component of the conversion voltage, U DC To measure the DC side voltage.

[0106] In one embodiment of the present application, some preset sector-on time mapping relationships are shown in Table 4:

[0107] Table 4 Some preset sector-on time mapping relationships

[0108]

[0109] Among them, the small sector is located in the large sector I, T a is the vector action time corresponding to the first basic voltage vector, T b is the vector action time corresponding to the first basic voltage vector, T c is the vector action time corresponding to the first basic voltage vector, T Sa1 、T Sa2 、T Sb1 、T Sb2 、T Sc1 、T Sc2 They are the numbers of the switching devices of different phases respectively.

[0110] In one embodiment of the present application, the device conduction time of the odd-numbered switch devices in each phase is complementary, and the device conduction time of the even-numbered switch devices is complementary. Sa1 =T S -T Sa3 ,T Sa2 =T S -T Sa5 , T S This is the control cycle.

[0111] In one embodiment of the present application, after obtaining at least one initial switching state sequence, traditional space vector pulse width modulation (SVPWM) selects any initial switching state sequence as a target switching state sequence, and determines the device on-time of each switching device according to a preset sector-action time mapping relationship and a preset sector-on-time mapping relationship in turn, so as to adjust the output of the pulse width modulation wave to realize the control of the inverter, but does not perform temperature control protection on the switching device.

[0112] In one embodiment of the present application, Figure 6 FIG. 1 is a schematic diagram showing an implementation flow of a thermal protection method for an inverter according to an embodiment of the present application. Figure 6 As shown, determine the initial switch state sequence: the AC side electrical data and the DC side electrical data determine the initial switch state sequence corresponding to the previous control cycle; the temperature sensor detects overheating: if the measured temperature of a switch device collected by the temperature sensor is greater than or equal to the preset temperature threshold, the switch device is determined as an overheated device; calculate the initial switch state sequence with the minimum junction temperature cost: calculate the junction temperature cost of each initial switch state sequence corresponding to the overheated device, and determine the initial switch state sequence corresponding to the minimum junction temperature cost as the first candidate switch state sequence; calculate the DC side voltage difference Udc output by the current sector: determine the predicted DC side voltage based on the first candidate switch state sequence and the preset electrical parameters of the inverter, and determine the difference between the predicted DC side voltage and the measured DC side voltage as the DC side voltage difference; whether the DC side voltage difference Overlimit: If the DC side voltage difference is greater than the preset voltage threshold, then enter the step of determining the initial switch state sequence of the sub-junction temperature cost; if the DC side voltage difference is less than or equal to the preset voltage threshold, then enter the step of calculating Ta, Tb, Tc according to Table 3; Determine the initial switch state sequence of the sub-junction temperature cost: Determine the initial switch state sequence corresponding to the sub-junction temperature cost as the first candidate switch state sequence; Calculate Ta, Tb, Tc according to Table 3: Determine the vector action time corresponding to each basic voltage vector based on the preset sector-action time mapping relationship; Update the value of the CPU comparison register according to Table 4: Determine the device conduction time of each switching device based on the preset sector-conduction time mapping relationship; PWM wave output: According to the device conduction time of each switching device, adjust the output of the pulse width modulation wave to control the inverter. This application can reduce the risk of thermal overload of the switching device and keep the output three-phase current and three-phase voltage unchanged; In addition, different system models and simplified calculations are considered, such as through the Thevenin equivalent thermal impedance and the reduced-order Foster thermal network model to save the calculation time of the controller and the hardware cost of the circuit.

[0113] In one embodiment of the present application, for example, in the last control cycle, the reference voltage vector Uref It falls in large sector I and small sector 5, and 5 initial switching state sequences have been preset, then i=1, 2, 3, 4, 5; at the beginning of this control cycle, if only the measured temperature of the temperature sensor on the switching device Sa1 reaches the preset temperature threshold, for each initial switching state sequence, the predicted junction temperature of the switching device Sa1 is calculated, and the initial switching state sequence corresponding to the minimum junction temperature cost is selected as the target switching state sequence of this control cycle, so as to control the inverter within this control cycle.

[0114] In one embodiment of the present application, the device conduction time of each switch device is controlled by modifying the value of a timer register. The timer register is located in the CPU of the control circuit of the inverter.

[0115] See also Figure 7 , Figure 7 A block diagram of a thermal protection device for an inverter according to an embodiment of the present application is shown. The device can be applied to Figure 1 The implementation environment shown in the figure is specifically configured in the control circuit 104 of the inverter. The device can also be applied to other exemplary implementation environments and specifically configured in other devices. This embodiment does not limit the implementation environment to which the device is applied.

[0116] like Figure 7 As shown, a thermal protection device 700 for an inverter according to an embodiment of the present application includes: a data acquisition module 701 , an initial sequence determination module 702 , a temperature control processing module 703 and a target sequence determination module 704 .

[0117] The data acquisition module 701 is used to acquire current monitoring data of the inverter, and the current monitoring data includes electrical monitoring data and measured temperatures of multiple switching devices;

[0118] An initial sequence determination module 702 is used to determine at least one initial switch state sequence according to the electrical monitoring data, where the initial switch state sequence is used to characterize a plurality of historical switch state combinations in the inverter in the previous control cycle, where the historical switch state combinations include switch states of multiple levels;

[0119] The temperature control processing module 703 is used to calculate the junction temperature cost of each initial switch state sequence corresponding to the overheating device, and the junction temperature cost is calculated based on the total energy loss of all overheating devices and the preset device limit junction temperature. The overheating device is used to characterize the switch device whose measured temperature is greater than or equal to the preset temperature threshold;

[0120] The target sequence determination module 704 is used to determine the target switch state sequence of the current control cycle from at least one initial switch state sequence according to at least one junction temperature cost, so as to adjust the output of the pulse width modulation wave to control the inverter.

[0121] It should be noted that the thermal protection device for the inverter provided in the above embodiment and the thermal protection method for the inverter provided in the above embodiment belong to the same concept, wherein the specific manner in which each module and unit performs the operation has been described in detail in the method embodiment and will not be repeated here. In practical applications, the thermal protection device for the inverter provided in the above embodiment can allocate the above functions to different functional modules as needed, that is, divide the internal structure of the device into different functional modules to complete all or part of the functions described above, and this is not limited here.

[0122] An embodiment of the present application also provides an electronic device, comprising: one or more processors; a storage device for storing one or more programs, when the one or more programs are executed by one or more processors, the electronic device implements the thermal protection method of the inverter provided in the above-mentioned embodiments.

[0123] See also Figure 8 , Figure 8 The structure diagram of the computer system suitable for implementing the electronic device of the embodiment of the present application is shown. It should be noted that: Figure 8 The computer system 800 of the electronic device shown is only an example and should not bring any limitation to the functions and scope of use of the embodiments of the present application.

[0124] like Figure 8 As shown, the computer system 800 includes a central processing unit (CPU) 801, which can perform various appropriate actions and processes according to the program stored in the read-only memory (ROM) 802 or the program loaded from the storage part 808 to the random access memory (RAM) 803, such as executing the method in the above embodiment. In the RAM 803, various programs and data required for system operation are also stored. The CPU 801, ROM 802 and RAM 803 are connected to each other through a bus 804. The input / output (I / O) interface 805 is also connected to the bus 804.

[0125] The following components are connected to the I / O interface 805: an input section 806 including a keyboard, a mouse, etc.; an output section 807 including a cathode ray tube (CRT), a liquid crystal display (LCD), etc., and a speaker; a storage section 808 including a hard disk, etc.; and a communication section 809 including a network interface card such as a LAN (Local Area Network) card, a modem, etc. The communication section 809 performs communication processing via a network such as the Internet. A drive 810 is also connected to the I / O interface 805 as needed. A removable medium 811, such as a magnetic disk, an optical disk, a magneto-optical disk, a semiconductor memory, etc., is installed on the drive 810 as needed so that a computer program read therefrom is installed into the storage section 808 as needed.

[0126] In particular, according to an embodiment of the present application, the process described above with reference to the flowchart can be implemented as a computer software program. For example, an embodiment of the present application includes a computer program product, which includes a computer program carried on a computer-readable medium, and the computer program includes a computer program for executing the method shown in the flowchart. In such an embodiment, the computer program can be downloaded and installed from a network through a communication section 809, and / or installed from a removable medium 811. When the computer program is executed by a central processing unit (CPU) 801, various functions defined in the system of the present application are executed.

[0127] It should be noted that the computer-readable medium shown in the embodiment of the present application can be a computer-readable signal medium or a computer-readable storage medium or any combination of the above two. The computer-readable storage medium can be, for example, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or device, or any combination of the above. More specific examples of computer-readable storage media may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a flash memory, an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present application, a computer-readable signal medium may include a data signal propagated in a baseband or as part of a carrier wave, wherein a computer-readable computer program is carried. This propagated data signal can take a variety of forms, including but not limited to an electromagnetic signal, an optical signal, or any suitable combination of the above. A computer-readable signal medium may also be any computer-readable medium other than a computer-readable storage medium, which may send, propagate or transmit a program for use by or in conjunction with an instruction execution system, apparatus or device. A computer program contained on a computer-readable medium may be transmitted using any appropriate medium, including but not limited to: wireless, wired, etc., or any suitable combination of the above.

[0128] The flowchart and block diagram in the accompanying drawings illustrate the possible architecture, functions and operations of the system, method and computer program product according to various embodiments of the present application. Wherein, each box in the flowchart or block diagram can represent a module, a program segment, or a part of the code, and the above-mentioned module, program segment, or a part of the code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flowchart, and the combination of boxes in the block diagram or flowchart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0129] The units involved in the embodiments described in the present application can be implemented by software or by hardware, and the units described can also be set in a processor. Among them, the names of these units do not constitute a limitation on the units themselves under certain circumstances. Therefore, the technical solution according to the implementation mode of the present application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, a USB flash drive, a mobile hard disk, etc.) or on a network, including a number of instructions to enable a computing device (which can be a personal computer, a server, a touch terminal, or a network device, etc.) to execute the method according to the implementation mode of the present application.

[0130] Another aspect of the present application further provides a computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor of a computer, the computer executes the thermal protection method for the inverter provided in the above embodiments. The computer-readable storage medium may be included in the electronic device described in the above embodiments, or may exist independently without being assembled into the electronic device.

[0131] In the above embodiments, unless otherwise specified, by using serial numbers such as "first" and "second" to describe common objects, it only means that they refer to different instances of the same object, rather than indicating that the objects being described must adopt a given order, whether in time, space, sorting or any other way.

[0132] The above embodiments are merely illustrative of the principles and effects of the present application, and are not intended to limit the present application. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present application shall still be covered by the claims of the present application.

Claims

1. A thermal protection method for an inverter, characterized in that: The method comprises: Acquiring current monitoring data of the inverter, the current monitoring data including electrical monitoring data and measured temperatures of a plurality of switching devices; Determine at least one initial switch state sequence according to the electrical monitoring data, wherein the initial switch state sequence is used to characterize a plurality of historical switch state combinations in the inverter in a previous control cycle, wherein the historical switch state combinations include switch states of a plurality of levels; Calculating the junction temperature cost of each initial switch state sequence corresponding to the overheated device, wherein the junction temperature cost is calculated based on the total energy loss of all overheated devices and a preset device limit junction temperature, and the overheated device is used to characterize the switch device whose measured temperature is greater than or equal to the preset temperature threshold; A target switch state sequence of the current control cycle is determined from at least one initial switch state sequence according to at least one junction temperature cost, so as to adjust the output of the pulse width modulation wave to control the inverter.

2. The thermal protection method for an inverter according to claim 1, characterized in that: Calculate the junction temperature cost of the initial sequence of switching states corresponding to the overheated device, including: determining a predicted junction temperature of the overheated device according to a measured temperature and a heat generation temperature of the overheated device; The initial cost of the overheating device is determined based on the difference between the preset device limit junction temperature and the predicted junction temperature of the overheating device; determining the sum of the initial costs of all overheated devices as the junction temperature cost of the initial switching state sequence; The heat generation temperature is obtained according to the total power loss and the Thevenin equivalent thermal impedance of the overheating device, and the total power loss and the equivalent thermal impedance are obtained based on the initial switching state sequence and preset electrical parameters corresponding to the inverter.

3. The thermal protection method for an inverter according to claim 2, characterized in that: The total power loss of the overheated device is determined by: determining a conduction power loss based on the initial sequence of switching states, a first electrical parameter of a diode, and a second electrical parameter of the overheat device; determining a switching energy loss based on the number of switching transitions of the overheating device in the initial switching state sequence; determining the sum of the conduction power loss and the switching energy loss as the total power loss of the overheating device; The preset electrical parameters include the first electrical parameters and the second electrical parameters, and the diode is connected in parallel with the overheating device.

4. The thermal protection method for an inverter according to claim 2, characterized in that: Determining the switching energy loss based on the number of switching transitions of the overheating device in the initial switching state sequence includes: Determine the dissipated energy during each switch transition and the reverse recovery energy dissipated during diode switching based on the number of transitions of the overheating device in the initial switch state sequence; Determine the switching energy loss according to an average value between the total amount of the dissipated energy and the total amount of the reverse recovery energy; The switch conversion includes turning on or off the overheating device.

5. The thermal protection method for an inverter according to claim 1, characterized in that: Determining a target switching state sequence from at least one initial switching state sequence according to at least one junction temperature cost includes: determining an initial switch state sequence corresponding to a minimum junction temperature cost as a first candidate switch state sequence; Calculating a DC side voltage difference corresponding to the first candidate switch state sequence according to DC side electrical data, wherein the electrical monitoring data includes the DC side electrical data; If the DC side voltage difference is less than or equal to a preset voltage threshold, determining the first candidate switch state sequence as a target switch state sequence; If the DC side voltage difference is greater than the preset voltage threshold, the initial switch state sequence corresponding to the next smallest junction temperature cost is determined as the first candidate switch state sequence, and the step of calculating the DC side voltage difference corresponding to the first candidate switch state sequence according to the DC side electrical data is repeated. If the DC side voltage difference is greater than the preset voltage threshold, the initial switch state sequence corresponding to the next smallest junction temperature cost is determined as the first candidate switch state sequence, until the DC side voltage difference is less than or equal to the preset voltage threshold, and the first candidate switch state sequence is determined as the target switch state sequence.

6. The thermal protection method for an inverter according to claim 1, characterized in that: Determining a target switching state sequence from at least one initial switching state sequence according to at least one junction temperature cost, further comprising: Calculating the DC side voltage difference corresponding to each of the initial switch state sequences according to the DC side electrical data, wherein the electrical monitoring data includes the DC side electrical data; If the DC side voltage difference corresponding to an initial switch state sequence is less than or equal to a preset voltage threshold, the initial switch state sequence is determined as a second candidate switch state sequence; The second candidate switch state sequence corresponding to the minimum junction temperature cost is determined as the target switch state sequence.

7. The thermal protection method for an inverter according to claim 5 or 6, characterized in that: The determination of the DC side voltage difference includes: Calculating an initial DC side voltage of each historical switch state according to preset electrical parameters of the inverter, wherein the historical switch state is obtained based on the initial switch state sequence or the first candidate switch state sequence; Determining a predicted DC link voltage based on an average value of each of the initial DC link voltages; A difference between the predicted DC link voltage and the measured DC link voltage in the DC link electrical data is determined as a DC link voltage difference.

8. A thermal protection device for an inverter, characterized in that: The device comprises: A data acquisition module, used to acquire current monitoring data of the inverter, wherein the current monitoring data includes electrical monitoring data and measured temperatures of multiple switching devices; An initial sequence determination module, used to determine at least one initial switch state sequence according to the electrical monitoring data, wherein the initial switch state sequence is used to characterize a plurality of historical switch state combinations in the inverter in a previous control cycle, wherein the historical switch state combinations include switch states of a plurality of levels; A temperature control processing module, used to calculate the junction temperature cost of each initial switch state sequence corresponding to the overheating device, wherein the junction temperature cost is calculated based on the total energy loss of all overheating devices and a preset device limit junction temperature, and the overheating device is used to characterize the switching device whose measured temperature is greater than or equal to the preset temperature threshold; The target sequence determination module is used to determine the target switch state sequence of the current control cycle from at least one initial switch state sequence according to at least one junction temperature cost, so as to adjust the output of the pulse width modulation wave to control the inverter.

9. An electronic device, characterized in that: The electronic device comprises: one or more processors; A storage device for storing one or more programs, which, when executed by the one or more processors, enables the electronic device to implement the thermal protection method for the inverter as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed by a processor of a computer, the computer is caused to execute the thermal protection method for an inverter according to any one of claims 1 to 7.

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