Flexible DC Converter Valve Loss Calculation Method, Device and Equipment Based on Oscillogram Data

Abstract

The present application relates to a method, device and equipment for calculating the losses of a flexible DC converter valve based on recorded wave data. The method includes obtaining the device parameters and recorded wave data of the flexible DC converter valve; determining the capacitor switching state according to the capacitor operating state of the (k + 1)-th sampling point relative to the k-th sampling point in each sub-module, and determining the operating state of the devices in the sub-module according to the capacitor switching state and the positive and negative of the arm current corresponding to the k-th sampling point; within the total recorded wave step length, calculating according to the operating state of the devices in each sub-module and the recorded wave data to obtain the total IGBT losses corresponding to each IGBT in the sub-module and the total diode losses corresponding to each diode; calculating according to the number of IGBTs, the number of diodes in each sub-module, and the corresponding total IGBT losses and total diode losses to obtain the total module losses of the sub-module; calculating according to the number of sub-modules and the total module losses to obtain the total converter valve losses of the flexible DC converter valve.

Description

Technical Field

[0001] The present application relates to the technical field of flexible DC power transmission, and particularly to a method, device, and equipment for calculating the losses of a flexible DC converter valve based on oscillographic data. Background Art

[0002] Flexible DC converter valves based on modular multilevel converters (MMCs) usually adopt nearest level control (NLC). The characteristic of nearest level control is that the switching frequencies of cascaded sub-modules are basically the same, but they do not turn on and off simultaneously. Instead, they are closely related to the voltage sorting of each sub-module in the bridge arm. This results in the fact that the working model of the converter valve obtained with the average switching frequency cannot approximate the actual working conditions, and the actual switching timings of each sub-module of the flexible DC converter valve cannot be accurately expressed with the average switching model, making it difficult to analyze the losses of the flexible DC converter valve at the engineering site and being unfavorable for the evaluation of the loss characteristics and economy of the converter valve.

[0003] In current flexible DC projects, the ability to record the operating conditions of the converter valve has been available. The recorded data includes arm voltage and current, arm fault signals, sub-module voltage and current, sub-module logic signals, sub-module fault signals, etc. The recorded data is stored and transferred in the common format for transient data exchange (COMTRADE) in the IEEE standard. Among them, the discrete sampling results such as the arm current, sub-module voltage, and sub-module device switching sequence obtained through recording provide the most reliable data basis for analyzing the losses of the converter valve. Therefore, a feasible solution for calculating the losses at the converter valve engineering site is to analyze the recorded data of the converter valve and conduct analysis based on this. However, the current analysis of recorded data is still relatively difficult and the calculation process is cumbersome, which hinders the further development of the loss calculation method. Summary of the Invention

[0004] Embodiments of the present application provide a method, device, and equipment for calculating the losses of a flexible DC converter valve based on oscillographic data, which are applied to the grid black start system of flexible DC power transmission and are used to solve the technical problem that the calculation process of the losses of existing flexible DC converter valves in flexible DC projects is cumbersome, resulting in low calculation efficiency.

[0005] To achieve the above object, the embodiments of the present application provide the following technical solutions:

[0006] A method for calculating the losses of a flexible DC converter valve based on oscillographic data includes the following steps:

[0007] Obtain the device parameters and oscillogram data of the flexible DC converter valve. The device parameters include the number of sub-modules of the converter valve, the number of IGBTs and the number of diodes in each sub-module. The oscillogram data includes the total duration of the oscillogram, the total number of steps of the oscillogram, the sampling step of the oscillogram, the number of sampling points, the opening frequency, the closing frequency, the opening current corresponding to each opening, the closing current corresponding to each closing, and the arm current, conduction voltage drop, conduction current and capacitor operating state corresponding to each sampling point;

[0008] Determine the capacitor switching state according to the capacitor operating state of the (k + 1)-th sampling point in each sub-module relative to the capacitor operating state of the k-th sampling point. Determine the operating states of the IGBT and diode in this sub-module according to the capacitor switching state and the positive and negative of the arm current corresponding to the k-th sampling point;

[0009] Within the total number of steps of the oscillogram, calculate according to the operating states of the IGBTs, the operating states of the diodes in each sub-module and the oscillogram data to obtain the total IGBT loss corresponding to each IGBT in this sub-module and the total diode loss corresponding to each diode in this sub-module;

[0010] Calculate according to the number of IGBTs, the number of diodes in each sub-module and the corresponding total IGBT loss and total diode loss to obtain the total module loss corresponding to this sub-module;

[0011] Calculate according to the number of sub-modules and the total module loss corresponding to each sub-module to obtain the total converter valve loss of the flexible DC converter valve;

[0012] Where k is a natural number greater than 2.

[0013] Preferably, within the total number of steps of the oscillogram, calculating according to the operating states of the IGBTs, the operating states of the diodes in each sub-module and the oscillogram data to obtain the total IGBT loss corresponding to each IGBT in this sub-module and the total diode loss corresponding to each diode in this sub-module includes:

[0014] Determine the conducting devices and switching devices according to the operating states of the IGBTs and the operating states of the diodes in each sub-module. The switching devices include opening devices and closing devices;

[0015] Calculate according to the number of sampling points, the sampling step of the oscillogram and the conduction voltage drop and conduction current of the corresponding conducting devices at each sampling point to obtain the total conduction loss of the conducting devices;

[0016] Calculate the total switching loss of the switching devices according to the switching devices, the opening frequency, the closing frequency, the opening current corresponding to each opening and the closing current corresponding to each closing;

[0017] Based on the total recording duration, the total conduction loss of the conducting devices, and the total switching loss of the switching devices, iterative calculations are performed based on the sub-module thermal resistance model to obtain the total device power loss;

[0018] Extract the total IGBT loss corresponding to each IGBT and the total diode loss corresponding to each diode from the total device power loss.

[0019] Preferably, according to the number of sampling points and the conduction voltage drop and conduction current of the conducting devices corresponding to each sampling point, the total conduction loss of the conducting devices is obtained, including:

[0020] Obtain the conduction voltage drop and conduction current of the conducting devices corresponding to each sampling point according to each sampling point, and calculate the sampling conduction loss corresponding to this sampling point according to the conduction voltage drop, the conduction current, and the recording sampling step;

[0021] Calculate the sampling conduction loss of each sampling point according to the number of sampling points using the conduction loss calculation formula to obtain the total conduction loss of the conducting devices;

[0022] The conduction loss calculation formula is:

[0023]

[0024] In the formula, V cond [k] is the conduction voltage drop of the conducting device corresponding to the k-th sampling point, τ is the recording sampling step, I[k] is the conduction current of the conducting device corresponding to the k-th sampling point, N is the number of sampling points within the total recording steps, and E cond_loss is the total conduction loss of the conducting device.

[0025] Preferably, according to the switching device, the turn-on frequency, the turn-off frequency, and the turn-on current corresponding to each turn-on and the turn-off current corresponding to each turn-off, the total switching loss of the switching device is obtained, including:

[0026] Obtain the turn-on current or turn-off current corresponding to the sampling point as the characteristic current according to the switching device, where the switching device is the turn-on of the IGBT, the turn-off of the IGBT, and / or the reverse recovery conduction of the diode;

[0027] Calculate using the first switching loss calculation formula according to the characteristic current to obtain the first switching loss for turn-on, the second switching loss for turn-off, and / or the third switching loss for reverse recovery conduction;

[0028] The total switching loss of the switching device is calculated by using the second switching loss calculation formula based on the turn-on frequency, turn-off frequency, first switching loss during turn-on, second switching loss during turn-off, and third switching loss during reverse recovery conduction of the switching device;

[0029] The first switching loss calculation formula is: E sw =β(1 + α)E sw_0 ,

[0030] The second switching loss calculation formula is:

[0031]

[0032] In the formula, E sw_loss is the total switching loss of the switching device, fswoff is the turn-off frequency of the IGBT; fswon is the number of turn-ons of the IGBT and reverse recovery conductions of the diode, E sw_off [j] is the second switching loss of the IGBT during the jth turn-off, E sw_on [j'] is the first switching loss of the IGBT during the j'th turn-on, E sw_rec [j′] is the third switching loss of the diode during the j'th reverse recovery conduction, E sw is the total switching loss, β is the total switching loss correction factor related to the junction temperature of the switching device, α is the total switching loss correction factor related to the voltage of the switching device, E sw_0 is the total switching loss when the junction temperature of the switching device is the low junction temperature and the sub-module voltage is the rated voltage, A s_0 , B s_0 , C s_0 are all the fitting polynomial coefficients of the on-state voltage drop curve when the junction temperature of the switching device is the low junction temperature and the sub-module voltage is the rated voltage, I j is the characteristic current.

[0033] Preferably, the total device power loss is obtained by iterative calculation based on the total recording duration, the total conduction loss of the conducting device, and the total switching loss of the switching device and based on the sub-module thermal resistance model, including: calculating the total device power loss by using the device loss power calculation formula in combination with the device junction temperature calculation formula and the iterative constraint conditions of the sub-module thermal resistance model according to the total recording duration, the total conduction loss of the conducting device, and the total switching loss of the switching device;

[0034] The device loss power calculation formula is: P loss =(E cond_loss +E sw_loss ) / T k

[0035] The device junction temperature calculation formula; Tvj = P loss (R jc + R s ) + T in

[0036] The iterative constraint condition is: (T vj [n] - T vj [n - 1]) / T vj [n - 1] < ε

[0037] In the formula, P loss is the total device power loss obtained in the nth iteration; T k is the total duration of the recorded wave; R jc is the device junction-to-case thermal resistance of the sub-module thermal resistance model; R s is the water-cooled radiator thermal resistance of the sub-module thermal resistance model; T in is the inlet water temperature of the water-cooled radiator of the sub-module thermal resistance model, T vj is the actual junction temperature of the sub-module device, n is the number of iterations, ε is a constant, E sw_loss is the total switching loss of the switching device, E cond_loss is the total conduction loss of the conducting device.

[0038] This application also provides a flexible DC converter valve loss calculation device based on recorded wave data, including a data acquisition module, a device state determination module, a first calculation module, a second calculation module, and a third calculation module;

[0039] The data acquisition module is used to acquire the device parameters and recorded wave data of the flexible DC converter valve. The device parameters include the number of sub-modules of the converter valve and the number of IGBTs and diodes in each sub-module. The recorded wave data includes the total duration of the recorded wave, the total number of steps of the recorded wave, the sampling step of the recorded wave, the number of sampling points, the number of turn-on frequencies, the number of turn-off frequencies, the turn-on current corresponding to each turn-on, the turn-off current corresponding to each turn-off, and the arm current, conduction voltage drop, conduction current, and capacitor working state corresponding to each sampling point;

[0040] The device state determination module is used to determine the capacitor switching state according to the capacitor working state of the (k + 1)th sampling point in each sub-module relative to the capacitor working state of the kth sampling point, and determine the working states of the IGBT and diode in the sub-module according to the capacitor switching state and the positive and negative of the arm current corresponding to the kth sampling point;

[0041] The first calculation module is used to calculate, within the total number of steps of the recorded wave, according to the working states of the IGBTs and diodes in each sub-module and the recorded wave data, to obtain the total IGBT loss corresponding to each IGBT in the sub-module and the total diode loss corresponding to each diode in the sub-module;

[0042] The second calculation module is configured to calculate, according to the number of IGBTs, the number of diodes, and the corresponding total IGBT losses and total diode losses of each sub-module, to obtain the total module losses corresponding to the sub-module.

[0043] The third calculation module is configured to calculate, according to the number of sub-modules and the total module losses corresponding to each sub-module, to obtain the total converter valve losses of the flexible DC converter valve.

[0044] Where k is a natural number greater than 2.

[0045] Preferably, the first calculation module includes a device confirmation sub-module, a total conduction loss calculation sub-module, a total switching loss calculation sub-module, a total loss calculation sub-module, and a loss extraction sub-module.

[0046] The device confirmation sub-module is configured to determine the conducting devices and switching devices according to the operating states of the IGBTs and the operating states of the diodes in each sub-module, and the switching devices include turn-on devices and turn-off devices.

[0047] The total conduction loss calculation sub-module is configured to calculate, according to the number of sampling points, the recording sampling step size, and the conduction voltage drop and conduction current of the corresponding conducting devices at each sampling point, to obtain the total conduction losses of the conducting devices.

[0048] The total switching loss calculation sub-module is configured to calculate the total switching losses of the switching devices according to the switching devices, the turn-on frequency, the turn-off frequency, the turn-on current corresponding to each turn-on, and the turn-off current corresponding to each turn-off.

[0049] The total loss calculation sub-module is configured to perform iterative calculations based on the sub-module thermal resistance model according to the total recording duration, the total conduction losses of the conducting devices, and the total switching losses of the switching devices to obtain the total device power losses.

[0050] The loss extraction sub-module is configured to extract the total IGBT losses corresponding to each IGBT and the total diode losses corresponding to each diode from the total device power losses.

[0051] Preferably, the total conduction loss calculation sub-module is further configured to obtain the conduction voltage drop and conduction current of the corresponding conducting devices at each sampling point according to each sampling point, calculate the sampling conduction loss corresponding to the sampling point according to the conduction voltage drop, the conduction current, and the recording sampling step size; calculate the sampling conduction losses of each sampling point according to the number of sampling points using the conduction loss calculation formula, to obtain the total conduction losses of the conducting devices.

[0052] The conduction loss calculation formula is as follows:

[0053]

[0054] In the formula, V cond [k] is the conduction voltage drop of the conducting device corresponding to the kth sampling point, τ is the recording sampling step, I[k] is the conduction current of the conducting device corresponding to the kth sampling point, N is the number of sampling points within the total recording step, and E cond_loss is the total conduction loss of the conducting device.

[0055] Preferably, the total switching loss calculation sub-module is further configured to obtain the turn-on current or turn-off current corresponding to the sampling point as the characteristic current according to the switching device, and the switching device is the turn-on of the IGBT, the turn-off of the IGBT, and / or the reverse recovery conduction of the diode;

[0056] Calculate using the first switching loss calculation formula according to the characteristic current to obtain the first switching loss during turn-on, the second switching loss during turn-off, and / or the third switching loss during reverse recovery conduction;

[0057] Calculate according to the turn-on frequency, turn-off frequency, the first switching loss during turn-on, the second switching loss during turn-off, and the third switching loss during reverse recovery conduction of the switching device using the second switching loss calculation formula to obtain the total switching loss of the switching device;

[0058] The first switching loss calculation formula is: E sw =β(1 + α)E sw_0 ,

[0059] The second switching loss calculation formula is:

[0060]

[0061] In the formula, E sw_loss is the total switching loss of the switching device, fswoff is the turn-off frequency of the IGBT; fswon is the number of turn-ons of the IGBT and the reverse recovery conduction of the diode, E sw_off [j] is the second switching loss of the jth turn-off of the IGBT, E sw_on [j′] is the first switching loss of the j′th turn-on of the IGBT, E sw_rec [j′] is the third switching loss of the j′th reverse recovery conduction of the diode, E sw is the total switching loss, β is the total switching loss correction factor related to the junction temperature of the switching device, α is the total switching loss correction factor related to the voltage of the switching device, E sw_0 is the total switching loss when the junction temperature of the switching device is the low junction temperature and the sub-module voltage is the rated voltage, A s_0, B s_0 , C s_0 All are the fitting polynomial coefficients of the on-state voltage drop curve when the junction temperature of the switching device is the low junction temperature and the sub-module voltage is the rated voltage. I j is the characteristic current.

[0062] This application also provides a terminal device, including a processor and a memory;

[0063] The memory is used to store program codes and transmit the program codes to the processor;

[0064] The processor is used to execute the above-mentioned flexible DC converter valve loss calculation method based on oscillographic data according to the instructions in the program codes.

[0065] It can be seen from the above technical solutions that the embodiments of this application have the following advantages: The flexible DC converter valve loss calculation method, device and equipment based on oscillographic data. The method includes: obtaining the device parameters and oscillographic data of the flexible DC converter valve; determining the capacitor switching state according to the capacitor operating state of the (k + 1)-th sampling point in each sub-module relative to the capacitor operating state of the k-th sampling point, and determining the operating states of the IGBT and diode in this sub-module according to the capacitor switching state and the positive and negative of the arm current corresponding to the k-th sampling point; within the total oscillographic step length, calculating according to the operating states of the IGBT and diode in each sub-module and the oscillographic data to obtain the total IGBT loss corresponding to each IGBT in this sub-module and the total diode loss corresponding to each diode in this sub-module; calculating according to the number of IGBTs, the number of diodes in each sub-module, and the corresponding total IGBT loss and total diode loss to obtain the module total loss corresponding to this sub-module; calculating according to the number of sub-modules and the module total loss corresponding to each sub-module to obtain the converter valve total loss of the flexible DC converter valve. Through the flexible DC converter valve loss calculation method based on oscillographic data, the total device power loss of each device in each sub-module, the module total loss of each sub-module, and the converter valve total loss can be obtained, which is beneficial to timely discover problems in the sub-modules of the converter valve during later maintenance and help the valve control make decisions in the early stage of the fault. This calculation method is simple and has high calculation efficiency, solving the technical problem that the calculation process of the loss of the existing flexible DC converter valve in the flexible DC project is complex, resulting in low calculation efficiency. Description of the Drawings

[0066] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of this application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0067] Figure 1 The flowchart of the steps of the flexible DC converter valve loss calculation method based on oscillographic data according to the embodiment of the present application;

[0068] Figure 2 The schematic framework diagram of the flexible DC converter valve sub-module in the flexible DC converter valve loss calculation method based on oscillographic data according to the embodiment of the present application;

[0069] Figure 3 The timing diagram of the sampling points of the oscillographic data in the flexible DC converter valve loss calculation method based on oscillographic data according to the embodiment of the present application;

[0070] Figure 4 The determined loss calculation flowchart of the flexible DC converter valve loss calculation method based on oscillographic data according to the embodiment of the present application;

[0071] Figure 5 The framework diagram of the sub-module thermal resistance model in the flexible DC converter valve loss calculation method based on oscillographic data according to the embodiment of the present application;

[0072] Figure 6 The framework diagram of the flexible DC converter valve loss calculation device based on oscillographic data according to the embodiment of the present application. Specific implementation manners

[0073] To make the invention purpose, features, and advantages of the present application more obvious and understandable, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present application. Obviously, the embodiments described below are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0074] The embodiment of the present application provides a flexible DC converter valve loss calculation method, device, and equipment based on oscillographic data, which are applied to the grid black start system of flexible DC power transmission, and are used to solve the technical problem that the calculation process of the loss of the existing flexible DC converter valve in the flexible DC project is complex, resulting in low calculation efficiency.

[0075] Embodiment 1:

[0076] Figure 1 The flowchart of the steps of the flexible DC converter valve loss calculation method based on oscillographic data according to the embodiment of the present application, Figure 2 The schematic framework diagram of the flexible DC converter valve sub-module in the flexible DC converter valve loss calculation method based on oscillographic data according to the embodiment of the present application, Figure 3It is the timing diagram of sampling points of the recorded wave data in the method for calculating the loss of a flexible DC converter valve based on recorded wave data according to the embodiment of the present application. Figure 4 It is the flowchart for determining the loss calculation in the method for calculating the loss of a flexible DC converter valve based on recorded wave data according to the embodiment of the present application.

[0077] As Figures 1 to 3 shown, the embodiment of the present application provides a method for calculating the loss of a flexible DC converter valve based on recorded wave data, including the following steps:

[0078] S1. Obtain the device parameters and recorded wave data of the flexible DC converter valve. The device parameters include the number of sub - modules of the converter valve, the number of IGBTs and the number of diodes in each sub - module. The recorded wave data includes the total recording duration, the total recording steps, the recording sampling step, the number of sampling points, the opening frequency, the closing frequency, the opening current corresponding to each opening, the closing current corresponding to each closing, and the arm current, conduction voltage drop, conduction current and capacitor working state corresponding to each sampling point.

[0079] It should be noted that the number of sub - modules is denoted as Nm, the number of IGBTs in each sub - module is denoted as Ni, and the number of diodes in each sub - module is Nd.

[0080] In the embodiment of the present application, the recorded wave data includes the arm recorded wave data and the sub - module recorded wave data of the flexible DC converter valve. The total recording duration, the total recording steps, the recording sampling step, the number of sampling points, the opening frequency, the closing frequency, the opening current corresponding to each opening, the closing current corresponding to each closing, and the arm current, conduction voltage drop, conduction current and capacitor working state are extracted from the arm recorded wave data and the sub - module recorded wave data. The arm current corresponding to each extracted sampling point is the arm current of the flexible DC converter valve. The capacitor working state is extracted from the sub - module capacitor switching time series of the sub - module recorded wave data.

[0081] It should be noted that the recorded wave data can be saved in a storage medium such as a computer in the COMTRAD format. The arm current includes the arm currents of the upper and lower arms of phase A, the upper and lower arms of phase B, and the upper and lower arms of phase C. As Figure 3 shown, in this embodiment, the capacitor working state includes capacitor insertion and capacitor removal, which can be represented by logic 1 and 0 respectively for capacitor insertion and capacitor removal, and the expression in the specific recorded wave data varies depending on the sub - module topology actually adopted.

[0082] As Figure 2 shown, in the embodiment of the present application, a sub - module of the flexible DC converter valve includes a sub - module capacitor C bus , a first diode D1, a second diode D2, a first IGBT T1 and a second IGBT T2.

[0083] It should be noted that, as Figure 2 shown, when the first IGBT T1 is in the on state and the second IGBT T2 is in the off state, the operating state of the capacitor can be represented by logic 1. When the first IGBT T1 is in the off state and the second IGBT T2 is in the on state, the operating state of the capacitor can be represented by logic 0.

[0084] S2. Determine the capacitor switching state according to the operating state of the capacitor at the (k + 1)-th sampling point relative to the operating state of the capacitor at the k-th sampling point in each sub-module. Determine the operating states of the IGBT and the diode in the sub-module according to the capacitor switching state and the positive and negative of the arm current corresponding to the k-th sampling point. Where k is a natural number greater than 2.

[0085] It should be noted that in step S2, one is to determine the capacitor switching state, and the other is to determine the operating states of the IGBT and the diode in the sub-module according to the capacitor switching state and the positive and negative of the arm current. In this embodiment, the capacitor switching states include four cases: the capacitor has been switched in, the capacitor has been switched out, the capacitor switches from being switched in to being switched out, and the capacitor switches from being switched out to being switched in. Among them, taking Figure 3 the timing waveform diagram of the sub-module sampling points shown as an example, at the sampling points k + a and k + a + 1 corresponding to the (k + a)-th step, both are capacitor cut-off logics. Therefore, the capacitor switching state at this step is that the capacitor has been switched out; at the sampling points k + b and k + b + 1 corresponding to the (k + b)-th step, they are capacitor cut-off logic and capacitor switched-in logic respectively. Therefore, the capacitor switching state at this step is that the capacitor switches from being switched out to being switched in; at the sampling points k + c and k + c + 1 corresponding to the (k + c)-th step, they are capacitor switched-in logic and capacitor cut-off logic respectively. Therefore, the capacitor switching state at this step is that the capacitor switches from being switched in to being switched out; at the sampling points k + d and k + d + 1 corresponding to the (k + d)-th step, both are capacitor switched-in logics. Therefore, the capacitor switching state at this step is that the capacitor has been switched in. After step S2 is completed for all sampling points, the operating state of sub-module m at any sampling point can be obtained.

[0086] In step S2 of the embodiment of the present application, according to the positive and negative of the arm current at each sampling point and in combination with the capacitor switching state of each sampling point sub-module, the loss that each device should calculate in this step length is obtained. According to whether the capacitor switching state changes, the device loss calculation can be divided into two categories: total conduction loss and total switching loss. If the capacitor switching state does not change within a single step length, only the total conduction loss of the device is calculated. If the capacitor switching state changes within a single step length, the total switching loss of the device needs to be calculated. In addition, the positive and negative of the instantaneous current of the flexible DC converter valve arm within each step length determine the conducting devices and non-conducting devices, commutation devices and non-commutation devices within the sub-module of this step. According to the different sub-module topologies, the conducting devices, non-conducting devices, commutation devices, and non-commutation devices should include one or more devices in the topology that meet this working state. When calculating the loss, the loss of all devices should be calculated one by one according to the working state of the sub-module of this step. Taking Figure 2 the sub-module with a half-bridge topology shown in arm as an example, the arm current takes the inflow of the sub-module in the figure as the reference positive direction.

[0087] As Figure 3 shown, in the embodiment of the present application, according to the capacitor switching state and the positive and negative of the arm current corresponding to the k-th sampling point, the working states of the IGBT and diode in this sub-module are determined as follows: If the capacitor switching state is that the capacitor has been inserted and the arm current corresponding to the k-th sampling point is positive or negative, then determine the conducting IGBT and / or diode in this sub-module.

[0088] It should be noted that when the capacitor switching state of the k-th step length does not change and the capacitor has been inserted, only the conducting devices are considered instead of the non-conducting devices when calculating the sub-module loss in the subsequent steps. As Figure 3 and Figure 4 shown, if the capacitor switching state is that the capacitor has been inserted and the arm current I arm [k] > 0 (i.e., the arm current is positive) corresponding to the sampling point k, then the conducting device in the sub-module is the first diode D1, and the non-conducting devices are the second diode D2, the first IGBT T1, and the second IGBT T2. Therefore, only the total conduction loss of the first diode D1 needs to be calculated in the subsequent steps of calculating the loss, and it is counted as the total conduction loss 1; if the capacitor switching state is that the capacitor has been inserted and the arm current I arm [k] < 0 (i.e., the arm current is negative) corresponding to the sampling point k, then the conducting device in the sub-module is the first IGBT T1, and the non-conducting devices are the first diode D1, the second diode D2, and the second IGBT T2. Therefore, only the total conduction loss of the first IGBT T1 needs to be calculated in the subsequent steps of calculating the loss, and it is counted as the total conduction loss 2.

[0089] As Figure 3As shown, in the embodiment of the present application, determining the operating states of the IGBT and diode in the sub-module according to the capacitor switching state and the positive and negative of the arm current corresponding to the k-th sampling point includes: if the capacitor switching state is that the capacitor has been removed and the arm current corresponding to the k-th sampling point is positive or negative, determine the conducting IGBT and / or diode in the sub-module.

[0090] It should be noted that when the capacitor switching state at the k-th step does not change and the capacitor has been removed, only the conducting devices are considered in the subsequent calculation of the sub-module loss, rather than the non-conducting devices. For example Figure 3 and Figure 4 As shown, if the capacitor switching state is that the capacitor has been removed and the arm current I arm [k]>0 (i.e., the arm current is positive), the conducting device in the sub-module is the second IGBT T2, and the non-conducting devices are the second diode D2, the first IGBT T1, and the first diode D1. Therefore, only the total conduction loss of the second IGBT T2 needs to be calculated in the subsequent loss calculation step, and it is counted as the total conduction loss 3; if the capacitor switching state is that the capacitor has been removed and the arm current I arm [k]<0 (i.e., the arm current is negative), the conducting device in the sub-module is the second diode D2, and the non-conducting devices are the first diode D1, the first IGBT T1, and the second IGBT T2. Therefore, only the total conduction loss of the second diode D2 needs to be calculated in the subsequent loss calculation step, and it is counted as the total conduction loss 4.

[0091] For example Figure 3 As shown, in the embodiment of the present application, determining the operating states of the IGBT and diode in the sub-module according to the capacitor switching state and the positive and negative of the arm current corresponding to the k-th sampling point includes: if the capacitor switching state is that the capacitor removal changes to insertion and the arm current corresponding to the k-th sampling point is positive or negative, determine the commuting IGBT and / or diode in the sub-module.

[0092] It should be noted that when the capacitor switching state at the k-th step does not change and the capacitor removal changes to insertion, only the commuting devices are considered in the subsequent calculation of the sub-module, rather than the non-commuting devices. For example Figure 3 and Figure 4 As shown, if the capacitor switching state is that the capacitor removal changes to insertion and the arm current I arm [k]>0 (i.e., the arm current is positive), commutation from the second IGBT T2 to the first diode D1 occurs, then the commuting devices in the sub-module are the second IGBT T2 and the first diode D1, and the non-commuting devices are the second diode D2 and the first IGBT T1. Therefore, only the turn-off loss of the second IGBT T2 needs to be calculated in the subsequent loss calculation step, and it is counted as the total switching loss 1; if the capacitor switching state is that the capacitor removal changes to insertion and the arm current Iarm [k] < 0 (i.e., the arm current is negative), and the second diode D2 commutates to the first IGBT T1. Then, the commutation devices in the sub-module are the second diode D2 and the first IGBT T1, and the non-commutation devices are the first diode D1 and the second IGBT T2. Therefore, in the subsequent steps, only the turn-on loss of the first IGBT T1 and the reverse recovery loss of the second diode D2 need to be calculated, and they are counted as the total switching loss 2.

[0093] As Figure 3 shown, in the embodiment of the present application, determining the operating states of the IGBT and the diode in the sub-module according to the capacitor switching state and the positive and negative of the arm current corresponding to the k-th sampling point includes: if the capacitor switching state is from capacitor insertion to removal and the arm current corresponding to the k-th sampling point is positive or negative, then determine the commutation IGBT and / or diode in the sub-module.

[0094] It should be noted that when the capacitor switching state of the k-th step does not change and is from capacitor insertion to removal, only the commutation devices are considered in the subsequent steps of calculating the sub-module, not the non-commutation devices. As Figure 3 and Figure 4 shown, if the capacitor switching state is from capacitor insertion to removal and the arm current I arm [k] > 0 (i.e., the arm current is positive), the first diode D1 commutates to the second IGBT T2. Then, the commutation devices in the sub-module are the second IGBT T2 and the first diode D1, and the non-commutation devices are the second diode D2 and the first IGBT T1. Therefore, in the subsequent steps, only the reverse recovery loss of the first diode D1 and the turn-on loss of the second IGBT T2 need to be calculated, and they are counted as the total switching loss 3; if the capacitor switching state is from capacitor insertion to removal and the arm current I arm [k] < 0 (i.e., the arm current is negative), the first IGBT T1 commutates to the second diode D2. Then, the commutation devices in the sub-module are the second diode D2 and the first IGBT T1, and the non-commutation devices are the first diode D1 and the second IGBT T2. Therefore, in the subsequent steps, only the turn-off loss of the first IGBT T1 needs to be calculated, and it is counted as the total switching loss 4.

[0095] S3. Within the total recording step length, calculate according to the operating state of the IGBT in each sub-module, the operating state of the diode, and the recording data to obtain the total IGBT loss corresponding to each IGBT in the sub-module and the total diode loss corresponding to each diode in the sub-module.

[0096] It should be noted that when calculating the loss of each device in the sub-module in step S3, it includes the total IGBT loss of each IGBT and the total diode loss of each diode.

[0097] Further, within the total recording step length, based on the operating states of the IGBTs and diodes in each sub-module and the recorded data, the total IGBT losses corresponding to each IGBT in the sub-module and the total diode losses corresponding to each diode in the sub-module are obtained, including:

[0098] Determine the conducting devices and switching devices according to the operating states of the IGBTs and diodes in each sub-module. The switching devices include turn-on devices and turn-off devices;

[0099] Calculate based on the number of sampling points, the recording sampling step length, and the conduction voltage drop and conduction current of the corresponding conducting device at each sampling point to obtain the total conduction loss of the conducting device;

[0100] Calculate the total switching loss of the switching device according to the switching device, the turn-on frequency, the turn-off frequency, the turn-on current corresponding to each turn-on, and the turn-off current corresponding to each turn-off;

[0101] Based on the total recording duration, the total conduction loss of the conducting device, and the total switching loss of the switching device, perform iterative calculations based on the sub-module thermal resistance model to obtain the total device power loss;

[0102] Extract the total IGBT loss corresponding to each IGBT and the total diode loss corresponding to each diode from the total device power loss.

[0103] Further, calculate based on the number of sampling points and the conduction voltage drop and conduction current of the corresponding conducting device at each sampling point to obtain the total conduction loss of the conducting device, including:

[0104] Obtain the conduction voltage drop and conduction current of the corresponding conducting device at each sampling point according to each sampling point. Calculate the sampling conduction loss corresponding to the sampling point based on the conduction voltage drop, conduction current, and recording sampling step length;

[0105] Calculate the sampling conduction loss of each sampling point according to the number of sampling points using the conduction loss calculation formula to obtain the total conduction loss of the conducting device;

[0106] The conduction loss calculation formula is:

[0107]

[0108] In the formula, V cond [k] is the conduction voltage drop of the conducting device corresponding to the kth sampling point, τ is the recording sampling step length, I[k] is the conduction current of the conducting device corresponding to the kth sampling point, N is the number of sampling points within the total recording step length, and E cond_loss is the total conduction loss of the conducting device.

[0109] Furthermore, the total switching loss of the switching device calculated according to the switching device, the turn-on frequency, the turn-off frequency, the turn-on current corresponding to each turn-on, and the turn-off current corresponding to each turn-off includes:

[0110] Obtain the turn-on current or turn-off current corresponding to the sampling point as the characteristic current according to the switching device, and the switching device is the turn-on of the IGBT, the turn-off of the IGBT, and / or the reverse recovery conduction of the diode;

[0111] Calculate according to the characteristic current using the first switching loss calculation formula to obtain the first switching loss of turn-on, the second switching loss of turn-off, and / or the third switching loss of reverse recovery conduction;

[0112] Calculate according to the turn-on frequency, turn-off frequency, first switching loss of turn-on, second switching loss of turn-off, and third switching loss of reverse recovery conduction of the switching device using the second switching loss calculation formula to obtain the total switching loss of the switching device;

[0113] The first switching loss calculation formula is: E sw = β(1 + α)E sw_0 ,

[0114] The second switching loss calculation formula is:

[0115]

[0116] In the formula, E sw_loss is the total switching loss of the switching device, fswoff is the turn-off frequency of the IGBT; fswon is the number of turn-ons of the IGBT and the reverse recovery conduction of the diode, E sw_off [j] is the second switching loss of the jth turn-off of the IGBT, E sw_on [j'] is the first switching loss of the j'th turn-on of the IGBT, E sw_rec [j'] is the third switching loss of the j'th reverse recovery conduction of the diode, E sw is the total switching loss, β is the total switching loss correction factor related to the junction temperature of the switching device, α is the total switching loss correction factor related to the voltage of the switching device, E sw_0 is the total switching loss when the junction temperature of the switching device is the low junction temperature and the sub-module voltage is the rated voltage, A s_0 , B s_0 , C s_0 are all the fitting polynomial coefficients of the on-state voltage drop curve when the junction temperature of the switching device is the low junction temperature and the sub-module voltage is the rated voltage, I j is the characteristic current.

[0117] It should be noted that the total conduction loss and the total switching loss are calculated by actually measuring the conduction voltage drop / current curve of the conduction device and the total switching loss / current curve of the sub-module through sub-module testing. According to the first calculation formula of the conduction voltage drop / current curve and the second calculation formula of the total switching loss / current curve, combined with the device junction temperature of the sub-module thermal resistance model, the conduction loss calculation formula and the first switching loss calculation formula are obtained to realize the loss of each device.

[0118] In the embodiment of the present application, the first calculation formula is: V cond = AI 2 + BI + C, where V cond is the conduction voltage drop of the device; A, B, and C are the fitting polynomial coefficients of the device conduction voltage drop / current curve respectively; I is the instantaneous current magnitude flowing through the device. Among them, V cond can be the IGBT IGBT saturation voltage drop V CEsat or the forward voltage drop V F of the diode. For the step size at the k-th sampling point, the conduction voltage drop of the device is taken as V cond [k], and the current is I[k] = (I arm [k] + I arm [k + 1]) / 2. Since the IGBT IGBT characteristics will also change with the change of the actual device junction temperature T vj , the conduction voltage drop is corrected according to T vj for the first calculation formula to obtain the first corrected calculation formula; the first corrected calculation formula is where is the conduction voltage drop correction factor related to the device junction temperature, and V cond_0 is the conduction voltage drop of the device at the low junction temperature T0.

[0119] It should be noted that V cond_0 = A0I 2 + B0I + C0, where A0, B0, and C0 are the fitting polynomial coefficients of the conduction voltage drop curve of the device at the low junction temperature T0 respectively. T0 can be taken as 25°C, and I is the conduction current of the device at the low junction temperature T0. The calculation formula of the correction factor is:

[0120]

[0121] where A1, B1, and C1 are the fitting polynomial coefficients of the conduction voltage drop curve of the device at the high junction temperature T1 respectively. T1 can be taken as 125°C or 150°C.

[0122] In the embodiment of the present application, the second calculation formula is: where E sw is the total switching loss, As , B s , C s are the fitting polynomial coefficients of the device total switching loss / current curve respectively; I j is the characteristic current of the device switching action. Among them, E sw can be the turn-off loss of the IGBT, the turn-on loss of the IGBT or the reverse recovery loss of the diode. For calculating E sw of the j-th switching action, take the turn-on loss of a single IGBT as E sw_on [j′], the turn-off loss of a single IGBT as E sw_off [j], and the reverse recovery loss of a single diode as E sw_rec [j′]. If the j-th switching action occurs at the step of the k-th sampling point, the characteristic current I j = (I arm [k] + I arm [k + 1]) / 2. Since the device total switching loss / current curve is closely related to the characteristic voltage point of the switching action and the device junction temperature, the first switching loss calculation formula considering the sub-module voltage and the change of the device junction temperature is E sw = β(1 + α)E sw_0 .

[0123] It should be noted that the calculation formula of the total switching loss correction factor α in the first switching loss calculation is:

[0124]

[0125] The calculation formula of the total switching loss correction factor β in the first switching loss calculation is:

[0126]

[0127] In the formula, V1 is the highest operating voltage of the sub-module, V s is the sub-module voltage at the k-th sampling point, take V s = (V BUS [k] + V BUS [k + 1]) / 2; E1 is the total switching loss when the sub-module voltage is V1 and the arm current magnitude is the device rated current I0 at the low device junction temperature T0; E0 is the total switching loss when the sub-module voltage is V0 and the arm current magnitude is I0 at the low device junction temperature T0, V BUS [k] is the arm voltage corresponding to the k-th sampling point, and E2 is the total switching loss when the sub-module voltage is V0 and the arm current magnitude is I0 at the high device junction temperature T1.

[0128] Figure 5 is the framework diagram of the sub-module thermal resistance model in the flexible DC converter valve loss calculation method based on the oscillogram data described in the embodiments of the present application.

[0129] Furthermore, based on the total recording duration, the total conduction loss of the conducting devices, and the total switching loss of the switching devices, iterative calculations are performed based on the sub-module thermal resistance model to obtain the total device power loss, including: using the device loss power calculation formula in combination with the device junction temperature calculation formula and the iterative constraint conditions of the sub-module thermal resistance model according to the total recording duration, the total conduction loss of the conducting devices, and the total switching loss of the switching devices to calculate the total device power loss;

[0130] The device loss power calculation formula is: P loss =(E cond_loss +E sw_loss ) / T k

[0131] The device junction temperature calculation formula; T vj =P loss (R jc +R s )+T in

[0132] The iterative constraint condition is: (T vj [n]-T vj [n - 1]) / T vj [n - 1]<ε

[0133] In the formula, P loss is the total device power loss obtained from the nth iteration; T k is the total recording duration; R jc is the device junction-to-case thermal resistance of the sub-module thermal resistance model; R s is the water-cooled radiator thermal resistance of the sub-module thermal resistance model; T in is the inlet water temperature of the water-cooled radiator of the sub-module thermal resistance model, T vj is the actual junction temperature of the sub-module device, n is the number of iterations, ε is a constant, E sw_loss is the total switching loss of the switching device, E cond_loss is the total conduction loss of the conducting device.

[0134] It should be noted that, as Figure 5 shown, the device loss power calculation formula is iteratively calculated in combination with the junction temperature of the device, the total conduction loss of the conducting device, and the total switching loss of the switching device to obtain the total device power loss P loss that meets the iterative constraint conditions. In this embodiment, if calculating the total device power loss of the i-th IGBT of the sub-module, it is denoted as the total IGBT loss P loss [i]; if calculating the total device power loss of the d-th diode of the sub-module, it is denoted as the total diode loss P loss [d]. Among them, the value of ε can be 5%.

[0135] S4. Calculate the total loss of the module corresponding to the sub-module based on the number of IGBTs, the number of diodes in each sub-module, and the corresponding total IGBT loss and total diode loss.

[0136] It should be noted that in step S4, the total diode loss of each diode and the total IGBT loss of each IGBT in the sub-module calculated in step S3 are summarized according to the number of devices to obtain the total loss of a sub-module.

[0137] In the embodiment of the present application, the total loss of the module is calculated by using the total loss calculation formula of the sub-module based on the number of IGBTs, the number of diodes in each sub-module, and the corresponding total IGBT loss and total diode loss. The total loss calculation formula of the sub-module is:

[0138]

[0139] In the formula, P loss_m is the total loss of the m-th sub-module, Ni is the number of IGBTs included in the m-th sub-module, and Nd is the number of diodes included in the m-th sub-module.

[0140] S5. Calculate the total loss of the flexible DC converter valve based on the number of sub-modules and the total loss of the module corresponding to each sub-module.

[0141] In the embodiment of the present application, the total loss of the flexible DC converter valve of this flexible DC converter valve loss calculation method based on oscillographic data also includes other losses P1 of the converter valve except for the power device losses. The total loss calculation formula of the flexible DC converter valve is:

[0142]

[0143] In the formula, P loss_total is the total loss of the flexible DC converter valve, and Nm is the number of sub-modules of the flexible DC converter valve.

[0144] A method for calculating the losses of a flexible DC converter valve based on recorded wave data provided by the present application includes obtaining the device parameters and recorded wave data of the flexible DC converter valve; determining the capacitor switching state according to the operating state of the capacitor at the (k + 1)-th sampling point in each sub-module relative to the operating state of the capacitor at the k-th sampling point, and determining the operating states of the IGBT and diode in the sub-module according to the capacitor switching state and the positive and negative of the arm current corresponding to the k-th sampling point; within the total recorded wave step length, calculating according to the operating states of the IGBT and diode in each sub-module and the recorded wave data to obtain the total IGBT losses corresponding to each IGBT in the sub-module and the total diode losses corresponding to each diode in the sub-module; calculating according to the number of IGBTs, the number of diodes in each sub-module, and the corresponding total IGBT losses and total diode losses to obtain the total module losses corresponding to the sub-module; calculating according to the number of sub-modules and the total module losses corresponding to each sub-module to obtain the total losses of the converter valve of the flexible DC converter valve. Through this method for calculating the losses of a flexible DC converter valve based on recorded wave data, the total device power losses of each device in each sub-module, the total module losses of each sub-module, and the total losses of the converter valve can be obtained, which is beneficial to timely discovering problems in the sub-modules of the converter valve during later maintenance and helping the valve control to make decisions in the early stage of the fault. This calculation method is simple and has high calculation efficiency, solving the technical problem that the calculation process of the losses of the existing flexible DC converter valve in the flexible DC project is complex, resulting in low calculation efficiency.

[0145] In an embodiment of the present application, the recorded wave data used in the method for calculating the losses of a flexible DC converter valve based on recorded wave data includes the recorded wave data of the arm currents of each bridge of the converter valve under a certain stable operating condition and the synchronous recorded wave data of the voltages of each power sub-module and the capacitor switching state of the sub-module. This method for calculating the losses of a flexible DC converter valve determines the operating states of each power device at each moment according to the relationship between the switching logic of the sub-module topology and the recorded wave form, and thus adopts the corresponding loss calculation; calculates the loss results step by step according to the recorded wave step length, which is a discrete calculation method, making this method for calculating the losses of a flexible DC converter valve based on recorded wave data suitable for being embedded in any computer program or hardware circuit based on programmable logic units such as FPGA or ASIC custom logic units for rapid execution, improving the calculation efficiency.

[0146] It should be noted that this method for calculating the losses of a flexible DC converter valve based on recorded wave data does not depend on any simulation and analytical calculation of the converter valve operating conditions. Regardless of the control strategy adopted by the converter valve, the losses of each device inside can be calculated according to this method for calculating the losses of a flexible DC converter valve based on recorded wave data, and thus the total module losses of each sub-module and the total losses of the converter valve can be deduced.

[0147] Embodiment 2:

[0148] Figure 6It is a framework diagram of the flexible DC converter valve loss calculation device based on the oscillographic data according to the embodiments of the present application.

[0149] As Figure 6 shown, the embodiments of the present application further provide a flexible DC converter valve loss calculation device based on oscillographic data, including a data acquisition module 10, a device state determination module 20, a first calculation module 30, a second calculation module 40, and a third calculation module 50;

[0150] The data acquisition module 10 is configured to acquire the device parameters and oscillographic data of the flexible DC converter valve. The device parameters include the number of sub-modules of the converter valve, the number of IGBTs and the number of diodes in each sub-module. The oscillographic data includes the total oscillographic duration, the total oscillographic steps, the oscillographic sampling step, the number of sampling points, the turn-on frequency, the turn-off frequency, the turn-on current corresponding to each turn-on, the turn-off current corresponding to each turn-off, and the arm current, conduction voltage drop, conduction current, and capacitor operating state corresponding to each sampling point;

[0151] The device state determination module 20 is configured to determine the capacitor switching state according to the capacitor operating state of the (k + 1)-th sampling point in each sub-module relative to the capacitor operating state of the k-th sampling point, and determine the operating states of the IGBT and diode in the sub-module according to the capacitor switching state and the positive and negative of the arm current corresponding to the k-th sampling point;

[0152] The first calculation module 30 is configured to calculate within the total oscillographic steps according to the operating states of the IGBTs and diodes in each sub-module and the oscillographic data, and obtain the total IGBT loss corresponding to each IGBT in the sub-module and the total diode loss corresponding to each diode in the sub-module;

[0153] The second calculation module 40 is configured to calculate according to the number of IGBTs, the number of diodes, and the corresponding total IGBT loss and total diode loss in each sub-module, and obtain the total module loss corresponding to the sub-module;

[0154] The third calculation module 50 is configured to calculate according to the number of sub-modules and the total module loss corresponding to each sub-module, and obtain the total converter valve loss of the flexible DC converter valve;

[0155] where k is a natural number greater than 2.

[0156] In the embodiments of the present application, the first calculation module 30 includes a device confirmation sub-module, a total conduction loss calculation sub-module, a total switching loss calculation sub-module, a total loss calculation sub-module, and a loss extraction sub-module;

[0157] The device confirmation sub-module is used to determine the conducting devices and switching devices according to the operating states of the IGBTs and the operating states of the diodes in each sub-module. The switching devices include turn-on devices and turn-off devices;

[0158] The total conduction loss calculation sub-module is used to calculate the total conduction loss of the conducting devices based on the number of sampling points, the recording sampling step size, and the conduction voltage drop and conduction current of the corresponding conducting devices at each sampling point;

[0159] The total switching loss calculation sub-module is used to calculate the total switching loss of the switching devices based on the switching devices, the turn-on frequency, the turn-off frequency, and the turn-on current corresponding to each turn-on and the turn-off current corresponding to each turn-off;

[0160] The total loss calculation sub-module is used to iteratively calculate the total device power loss based on the total recording duration, the total conduction loss of the conducting devices, and the total switching loss of the switching devices and based on the sub-module thermal resistance model;

[0161] The loss extraction sub-module is used to extract the total IGBT loss corresponding to each IGBT and the total diode loss corresponding to each diode from the total device power loss.

[0162] In an embodiment of the present application, the total conduction loss calculation sub-module is further used to obtain the conduction voltage drop and conduction current of the corresponding conducting device at each sampling point according to each sampling point, calculate the sampling conduction loss corresponding to the sampling point according to the conduction voltage drop, conduction current, and recording sampling step size; calculate the sampling conduction loss of each sampling point using the conduction loss calculation formula according to the number of sampling points to obtain the total conduction loss of the conducting devices;

[0163] The conduction loss calculation formula is:

[0164]

[0165] where, V cond [k] is the conduction voltage drop of the conducting device corresponding to the kth sampling point, τ is the recording sampling step size, I[k] is the conduction current of the conducting device corresponding to the kth sampling point, N is the number of sampling points within the total recording step length, E cond_loss is the total conduction loss of the conducting devices.

[0166] In an embodiment of the present application, the total switching loss calculation sub-module is further used to obtain the turn-on current or turn-off current corresponding to the sampling point as the characteristic current according to the switching devices. The switching devices are the turn-on of the IGBT, the turn-off of the IGBT, and / or the reverse recovery conduction of the diode;

[0167] Calculate using the first switching loss calculation formula based on the characteristic current to obtain the first switching loss during turn-on, the second switching loss during turn-off, and / or the third switching loss during reverse recovery conduction;

[0168] Calculate according to the turn-on frequency, turn-off frequency, the first switching loss during turn-on, the second switching loss during turn-off, and the third switching loss during reverse recovery conduction of the switching device using the second switching loss calculation formula to obtain the total switching loss of the switching device;

[0169] The first switching loss calculation formula is: E sw = β(1 + α)E sw_0 ,

[0170] The second switching loss calculation formula is:

[0171]

[0172] In the formula, E sw_loss is the total switching loss of the switching device, fswoff is the turn-off frequency of the IGBT; fswon is the number of turn-ons of the IGBT and reverse recovery conductions of the diode, E sw_off [j] is the second switching loss of the IGBT during the j-th turn-off, E sw_on [j'] is the first switching loss of the IGBT during the j'-th turn-on, E sw_rec [j'] is the third switching loss of the diode during the j'-th reverse recovery conduction, E sw is the total switching loss, β is the total switching loss correction factor related to the junction temperature of the switching device, α is the total switching loss correction factor related to the voltage of the switching device, E sw_0 is the total switching loss when the junction temperature of the switching device is the low junction temperature and the sub-module voltage is the rated voltage, A s_0 , B s_0 , C s_0 are all the fitting polynomial coefficients of the on-state voltage drop curve when the junction temperature of the switching device is the low junction temperature and the sub-module voltage is the rated voltage, I j is the characteristic current.

[0173] It should be noted that the modules in the device of the second embodiment correspond to the steps in the method of the first embodiment. The content of the flexible DC converter valve loss calculation method based on the oscillogram data has been elaborated in detail in the first embodiment, and the content of the modules in the device will not be elaborated in detail in the second embodiment here.

[0174] Embodiment Three:

[0175] The embodiment of the present application provides a terminal device, including a processor and a memory;

[0176] A memory for storing program code and transmitting the program code to a processor;

[0177] A processor for executing the above method for calculating the loss of a flexible DC converter valve based on oscillographic data according to the instructions in the program code.

[0178] It should be noted that the processor is used to execute the steps in the above embodiment of a method for calculating the loss of a flexible DC converter valve based on oscillographic data according to the instructions in the program code. Alternatively, when the processor executes the computer program, it implements the functions of each module / unit in the above system / device embodiments.

[0179] Exemplarily, the computer program can be divided into one or more modules / units. One or more modules / units are stored in the memory and executed by the processor to complete this application. One or more modules / units can be a series of computer program instruction segments capable of performing specific functions, and these instruction segments are used to describe the execution process of the computer program in the terminal device.

[0180] The terminal device can be a computing device such as a desktop computer, a notebook, a palm computer, and a cloud server. The terminal device may include, but is not limited to, a processor and a memory. Those skilled in the art can understand that this does not limit the terminal device, and it may include more or fewer components than shown in the figure, or combine some components, or different components. For example, the terminal device may also include input / output devices, network access devices, a bus, etc.

[0181] The so-called processor may be a central processing unit (CPU), or may also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0182] The memory can be an internal storage unit of the terminal device, such as the hard disk or memory of the terminal device. The memory can also be an external storage device of the terminal device, such as a plug-in hard disk equipped on the terminal device, a SmartMedia Card (SMC), a Secure Digital (SD) card, a Flash Card, etc. Further, the memory can also include both the internal storage unit of the terminal device and the external storage device. The memory is used to store computer programs and other programs and data required by the terminal device. The memory can also be used to temporarily store the data that has been output or will be output.

[0183] Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working processes of the above-described systems, devices, and units can refer to the corresponding processes in the foregoing method embodiments, and will not be elaborated herein.

[0184] In several embodiments provided in the present application, it should be understood that the disclosed systems, devices, and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is only a logical function division, and there can 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 displayed or discussed couplings or direct couplings or communication connections to each other can be through some interfaces, and the indirect couplings or communication connections of the devices or units can be in electrical, mechanical, or other forms.

[0185] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they can be located in one place, or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0186] In addition, each functional unit in the various embodiments of the present application can be integrated into one processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated units can be implemented in the form of hardware or in the form of software functional units.

[0187] When the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or all or part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in various embodiments of this application. The foregoing storage medium includes: various media that can store program codes, such as USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs.

[0188] As described above, the above embodiments are only used to illustrate the technical solutions of this application, rather than to limit them; although this application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of various embodiments of this application.

Claims

1. A method for calculating the losses of a flexible DC converter valve based on oscillographic data, characterized in that Including the following steps: Obtain the device parameters and oscillogram data of the flexible DC converter valve. The device parameters include the number of sub-modules of the converter valve, the number of IGBTs and the number of diodes in each sub-module. The oscillogram data includes the total duration of the oscillogram, the total number of steps of the oscillogram, the sampling step of the oscillogram, the number of sampling points, the on-frequency, the off-frequency, the on-current corresponding to each on-state, the off-current corresponding to each off-state, and the arm current, conduction voltage drop, conduction current and capacitor operating state corresponding to each sampling point; Determine the capacitor switching state according to the capacitor operating state of the (k + 1)-th sampling point relative to the capacitor operating state of the k-th sampling point in each sub-module. Determine the operating states of the IGBTs and diodes in this sub-module according to the capacitor switching state and the positive and negative of the arm current corresponding to the k-th sampling point; Within the total number of steps of the oscillogram, calculate according to the operating states of the IGBTs, the operating states of the diodes in each sub-module and the oscillogram data to obtain the total IGBT loss corresponding to each IGBT in this sub-module and the total diode loss corresponding to each diode in this sub-module; Calculate according to the number of IGBTs, the number of diodes in each sub-module and the corresponding total IGBT loss and total diode loss to obtain the total module loss corresponding to this sub-module; Calculate according to the number of sub-modules and the total module loss corresponding to each sub-module to obtain the total converter valve loss of the flexible DC converter valve; where k is a natural number greater than 2; Within the total number of steps of the oscillogram, calculating according to the operating states of the IGBTs, the operating states of the diodes in each sub-module and the oscillogram data to obtain the total IGBT loss corresponding to each IGBT in this sub-module and the total diode loss corresponding to each diode in this sub-module includes: Determine the conducting devices and switching devices according to the operating states of the IGBTs and the operating states of the diodes in each sub-module. The switching devices include turn-on devices and turn-off devices; Calculate according to the number of sampling points, the sampling step of the oscillogram and the conduction voltage drop and conduction current of the corresponding conducting devices at each sampling point to obtain the total conduction loss of the conducting devices; Calculate the total switching loss of the switching devices according to the switching devices, the on-frequency, the off-frequency, the on-current corresponding to each on-state and the off-current corresponding to each off-state; Perform iterative calculation based on the sub-module thermal resistance model according to the total duration of the oscillogram, the total conduction loss of the conducting devices and the total switching loss of the switching devices to obtain the total device power loss; Extract the total IGBT loss corresponding to each IGBT and the total diode loss corresponding to each diode from the total device power loss.

2. The method for calculating the loss of a flexible DC converter valve based on oscillographic data according to claim 1, wherein Calculating according to the number of sampling points and the conduction voltage drop and conduction current of the corresponding conducting devices at each sampling point to obtain the total conduction loss of the conducting devices includes: The conduction voltage drop and conduction current of the conduction device corresponding to each sampling point are obtained, and the sampling conduction loss corresponding to the sampling point is calculated according to the conduction voltage drop, the conduction current, and the oscillogram sampling step size; According to the number of sampling points, the sampling conduction losses of each sampling point are calculated using the conduction loss calculation formula to obtain the total conduction loss of the conduction device; The conduction loss calculation formula is: ； wherein, is the on-voltage drop of the on-state device corresponding to the k-th sampling point, is the recording sampling step size, is the on-state current of the on-state device corresponding to the k-th sampling point, and N is the number of sampling points within the total recording step length, is the total on-state loss of the on-state device.

3. The method for calculating the loss of a flexible DC converter valve based on oscillographic data according to claim 1, wherein The total switching loss of the switching device calculated according to the switching device, the turn-on frequency, the turn-off frequency, the turn-on current corresponding to each turn-on, and the turn-off current corresponding to each turn-off includes: The characteristic current corresponding to the sampling point, i.e., the turn-on current or turn-off current, is obtained according to the switching device. The switching device is the turn-on of an IGBT, the turn-off of an IGBT, and / or the reverse recovery conduction of a diode; The first switching loss of turn-on, the second switching loss of turn-off, and / or the third switching loss of reverse recovery conduction are obtained by calculating according to the characteristic current using the first switching loss calculation formula; The total switching loss of the switching device is calculated according to the turn-on frequency, the turn-off frequency, the first switching loss of turn-on, the second switching loss of turn-off, and the third switching loss of reverse recovery conduction of the switching device using the second switching loss calculation formula; The calculation formula for the first switching loss is as follows: , ; The second switching loss calculation formula is: ； Wherein, is the total switching loss of the switching device, fswoff is the turn-off frequency of the IGBT; fswon is the number of turn-on of the IGBT and reverse recovery turn-on of the diode, E sw_off [j] is the second switching loss of the j-th turn-off of the IGBT, E sw_on [j'] is the first switching loss of the j'-th turn-on of the IGBT, E sw_rec [j'] is the third switching loss of the j'-th reverse recovery turn-on of the diode, E sw is the total switching loss, is the total switching loss correction factor related to the junction temperature of the switching device, is the total switching loss correction factor related to the voltage of the switching device, E sw_0 is the total switching loss when the junction temperature of the switching device is the low junction temperature and the sub-module voltage is the rated voltage, A s_0 , B s_0 , C s_0 are all the fitting polynomial coefficients of the on-state voltage drop curve when the junction temperature of the switching device is the low junction temperature and the sub-module voltage is the rated voltage, I j is the characteristic current.

4. The loss calculation method of the flexible DC converter valve based on the oscillographic data according to claim 1, wherein The total device power loss is obtained by iterative calculation based on the sub-module thermal resistance model according to the total oscillogram duration, the total conduction loss of the conduction device, and the total switching loss of the switching device, including: calculating the total device power loss according to the total oscillogram duration, the total conduction loss of the conduction device, and the total switching loss of the switching device using the device loss power calculation formula in combination with the device junction temperature calculation formula and the iterative constraint conditions of the sub-module thermal resistance model; The calculation formula for the device loss power is as follows: ; The formula for calculating the device junction temperature; ; The iterative constraint condition is as follows: ; Wherein, is the total device power loss obtained in the nth iteration; is the total recording duration; is the device junction-to-case thermal resistance of the sub-module thermal resistance model; is the water-cooled radiator thermal resistance of the sub-module thermal resistance model; is the inlet water temperature of the water-cooled radiator of the sub-module thermal resistance model, T vj is the actual junction temperature of the sub-module device, n is the number of iterations, is a constant, is the total switching loss of the switching device, is the total conduction loss of the conducting device.

5. A flexible DC converter valve loss calculation device based on oscillographic data, characterized in that It includes a data acquisition module, a device state determination module, a first calculation module, a second calculation module, and a third calculation module; The data acquisition module is used to acquire the device parameters and oscillogram data of the flexible DC converter valve. The device parameters include the number of sub-modules of the converter valve and the number of IGBTs and diodes in each sub-module. The oscillogram data includes the total oscillogram duration, the total oscillogram step size, the oscillogram sampling step size, the number of sampling points, the turn-on frequency, the turn-off frequency, the turn-on current corresponding to each turn-on, the turn-off current corresponding to each turn-off, and the arm current, conduction voltage drop, conduction current, and capacitor working state corresponding to each sampling point; The device state determination module is used to determine the capacitor switching state according to the capacitor working state of the (k + 1)-th sampling point in each sub-module relative to the capacitor working state of the k-th sampling point, and determine the working states of the IGBT and diode in the sub-module according to the capacitor switching state and the positive and negative of the arm current corresponding to the k-th sampling point; The first calculation module is configured to calculate, within the total recording step length, based on the operating states of the IGBTs and diodes in each sub-module and the recording data, to obtain the total IGBT losses corresponding to each IGBT in the sub-module and the total diode losses corresponding to each diode in the sub-module; The second calculation module is configured to calculate, based on the number of IGBTs and diodes in each sub-module and the corresponding total IGBT losses and total diode losses, to obtain the total module losses corresponding to the sub-module; The third calculation module is configured to calculate, based on the number of sub-modules and the total module losses corresponding to each sub-module, to obtain the total converter valve losses of the flexible DC converter valve; where k is a natural number greater than 2; The first calculation module includes a device confirmation sub-module, a total conduction loss calculation sub-module, a total switching loss calculation sub-module, a total loss calculation sub-module, and a loss extraction sub-module; The device confirmation sub-module is configured to determine the conducting devices and switching devices according to the operating states of the IGBTs and diodes in each sub-module, and the switching devices include turn-on devices and turn-off devices; The total conduction loss calculation sub-module is configured to calculate, based on the number of sampling points, the recording sampling step length, and the conduction voltage drop and conduction current of the corresponding conducting devices at each sampling point, to obtain the total conduction losses of the conducting devices; The total switching loss calculation sub-module is configured to calculate, based on the switching devices, the turn-on frequency, the turn-off frequency, and the turn-on current corresponding to each turn-on and the turn-off current corresponding to each turn-off, to obtain the total switching losses of the switching devices; The total loss calculation sub-module is configured to perform iterative calculations based on the total recording duration, the total conduction losses of the conducting devices, and the total switching losses of the switching devices and based on the sub-module thermal resistance model to obtain the total device power losses; The loss extraction sub-module is configured to extract the total IGBT losses corresponding to each IGBT and the total diode losses corresponding to each diode from the total device power losses.

6. The loss calculation device for a flexible DC converter valve based on oscillographic data according to claim 5, wherein, The total conduction loss calculation sub-module is further configured to obtain the conduction voltage drop and conduction current of the corresponding conducting devices at each sampling point according to each sampling point, and calculate the sampling conduction loss corresponding to the sampling point according to the conduction voltage drop, the conduction current, and the recording sampling step length; Calculate the total conduction losses of the conducting devices by using the conduction loss calculation formula for the sampling conduction losses of each sampling point according to the number of sampling points; The conduction loss calculation formula is: ； Wherein, is the on-voltage drop of the on-state device corresponding to the k-th sampling point, is the recording sampling step size, is the on-state current of the on-state device corresponding to the k-th sampling point, and N is the number of sampling points within the total recording step length, is the total on-state loss of the on-state device.

7. The loss calculation device for a flexible DC converter valve based on oscillographic data according to claim 5, wherein The total switching loss calculation sub-module is further configured to obtain the turn-on current or turn-off current corresponding to the sampling point as the characteristic current according to the switching devices, and the switching devices are the turn-on of the IGBT, the turn-off of the IGBT, and / or the reverse recovery conduction of the diode; Calculate according to the characteristic current by using the first switching loss calculation formula to obtain the first switching loss for turn-on, the second switching loss for turn-off, and / or the third switching loss for reverse recovery conduction; Calculated according to the turn-on frequency, turn-off frequency, first switching loss during turn-on, second switching loss during turn-off, and third switching loss during reverse recovery conduction of the switching device using the second switching loss calculation formula to obtain the total switching loss of the switching device; The formula for calculating the first switching loss is as follows: , ; The second switching loss calculation formula is: ； Wherein, is the total switching loss of the switching device, fswoff is the turn-off frequency of the IGBT; fswon is the number of turn-on of the IGBT and reverse recovery turn-on of the diode, E sw_off [j] is the second switching loss of the j-th turn-off of the IGBT, E sw_on [j'] is the first switching loss of the j'-th turn-on of the IGBT, E sw_rec [j'] is the third switching loss of the j'-th reverse recovery turn-on of the diode, E sw is the total switching loss, is the total switching loss correction factor related to the junction temperature of the switching device, is the total switching loss correction factor related to the voltage of the switching device, E sw_0 is the total switching loss when the junction temperature of the switching device is the low junction temperature and the sub-module voltage is the rated voltage, A s_0 , B s_0 , C s_0 are all polynomial coefficients of the on-state voltage drop curve fitting when the junction temperature of the switching device is the low junction temperature and the sub-module voltage is the rated voltage, I j is the characteristic current.

8. A terminal device, characterized in that, It includes a processor and a memory; The memory is used to store program code and transmit the program code to the processor; The processor is used to execute the method for calculating the loss of the flexible DC converter valve based on the recorded wave data as described in any one of claims 1-4 according to the instructions in the program code.

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