CN111987926A - Control strategy optimization design method for active neutral point clamped three-level inverter - Google Patents

Control strategy optimization design method for active neutral point clamped three-level inverter Download PDF

Info

Publication number
CN111987926A
CN111987926A CN202010716414.XA CN202010716414A CN111987926A CN 111987926 A CN111987926 A CN 111987926A CN 202010716414 A CN202010716414 A CN 202010716414A CN 111987926 A CN111987926 A CN 111987926A
Authority
CN
China
Prior art keywords
loss
commutation
current
power device
junction temperature
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202010716414.XA
Other languages
Chinese (zh)
Inventor
王政
张博伦
邹志翔
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Southeast University
Original Assignee
Southeast University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Southeast University filed Critical Southeast University
Priority to CN202010716414.XA priority Critical patent/CN111987926A/en
Publication of CN111987926A publication Critical patent/CN111987926A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/483—Converters with outputs that each can have more than two voltages levels
    • H02M7/487—Neutral point clamped inverters
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/32—Means for protecting converters other than automatic disconnection
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0048—Circuits or arrangements for reducing losses
    • H02M1/0054—Transistor switching losses
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses an active neutral point clamping type three-level inverter control strategy optimization design method which includes the steps of calculating power device loss through inverter direct-current bus voltage, a current conversion mode and a power device loss model, and obtaining junction temperature of an inverter power device by combining a thermal model of the power device. On the basis, the thermal cycle of each power device is extracted according to a rain flow method, and the service life of the power device is predicted according to a service life calculation model. Through comparison of service life variances of the power devices, the current conversion mode of the active clamping three-level inverter is dynamically optimized and adjusted, so that the service life of the active clamping three-level inverter is prolonged. By adopting the method, the loss distribution and the junction temperature distribution of the active clamping three-level inverter can be optimized and the reliability of the system can be enhanced while the performance of the output waveform is maintained, so that the defects of the loss of a power device and the uneven distribution of the junction temperature are overcome, and the service life of the inverter is prolonged by optimizing the current conversion state of the inverter.

Description

Control strategy optimization design method for active neutral point clamped three-level inverter
Technical Field
The invention relates to an optimal design method for a control strategy of an active neutral point clamped three-level inverter, and belongs to the technical field of power electronics.
Background
The diode neutral point clamped three-level inverter has very wide application in a medium-voltage high-power electric drive system. The high-voltage and high-power output can be realized by using the low-voltage switching device, and the problem that the output voltage is limited by the withstand voltage of the power semiconductor device is solved. However, the diode midpoint clamping type three-level inverter has the defects of power device loss and uneven junction temperature distribution, so that the switching frequency and the capacity of the inverter are limited to a certain extent. The active neutral point clamped three-level inverter is proposed to solve these problems. Compared with a diode neutral point clamped three-level inverter, the active neutral point clamped three-level inverter replaces a clamping diode connected with the neutral point of a bus with a switching device, so that the number of switching states and current conversion processes is increased, and the degree of freedom is provided for balance loss and junction temperature distribution. However, if the active midpoint clamping type three-level inverter can well overcome the defects of the diode midpoint clamping type three-level inverter, the loss and the junction temperature of the system can be optimized and the reliability of the system can be improved while the quality of an output waveform is ensured by depending on a high-performance control strategy. Therefore, it is necessary to provide an optimal design method for the control strategy of the active midpoint clamping type three-level inverter.
At present, many scholars propose an optimization design method of an active neutral point clamped three-level inverter control strategy, but the existing control strategy has no proper commutation process division mode and has no established perfect reliability model. Therefore, it is necessary to provide an optimal design method for reliability and control strategy of an online monitoring system, which not only can solve the problems, but also considers the operation modes of the system under stable load and random load, and improves the applicability of the control strategy.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the control strategy optimization design method for the active neutral point clamping type three-level inverter overcomes the defects of power device loss and uneven junction temperature distribution, can acquire the accumulated loss of the device in a fixed time period in real time, and prolongs the service life of the whole system by changing the running state of the system.
The invention adopts the following technical scheme for solving the technical problems:
an active neutral point clamped three-level inverter control strategy optimization design method comprises the following steps:
step 1, dividing all commutation processes into two commutation modes according to a current path of an active neutral point clamped three-level inverter: an active commutation mode and a passive commutation mode, and analyzing loss distribution of different commutation modes;
step 2, acquiring voltages at two ends of a power device in the active neutral point clamped three-level inverter by using a voltage sensor, acquiring current passing through the power device in the active neutral point clamped three-level inverter by using a current sensor, and fitting a characteristic curve in a data manual to obtain a relation between loss and the voltage and the current;
step 3, substituting the voltage and the current obtained in the step 2 into the relation between the loss and the voltage and the current, calculating to obtain the loss, and introducing the loss into a heat network model to estimate the junction temperature of the power device;
step 4, acquiring the junction temperature of the power device in a time period, extracting thermal cycles from the junction temperature of the power device in the time period by adopting a rain flow counting method, using the thermal cycles for fatigue analysis, and introducing a life model to calculate the life loss of the power device;
step 5, aiming at the stable load, selecting a current conversion mode with the minimum loss variance as a current conversion mode for system operation according to the loss distribution conditions of different current conversion modes;
and 6, aiming at random loads, selecting the commutation mode with the minimum service life loss variance as the commutation mode of system operation according to the service life loss distribution conditions of different commutation modes.
As a preferred scheme of the present invention, step 1 divides all commutation processes into two commutation modes: the active commutation mode and the passive commutation mode specifically include:
according to 6 switch states of the active neutral point clamping type three-level inverter, 16 kinds of commutation processes with different currents are arranged and combined, wherein the current path change of 8 kinds of commutation processes is related to D5 or D6 and is unrelated to T5 or T6, the current path change of the other 8 kinds of commutation processes is related to T5 or T6 and is unrelated to D5 or D6, the former 8 kinds of commutation processes are defined as passive commutation modes, and the latter 8 kinds of commutation processes are defined as active commutation modes;
the active neutral point clamping type three-level inverter comprises a direct-current voltage source, first to second direct-current bus capacitors and an A-phase bridge arm; one end of the first direct current bus capacitor is connected with the anode of the direct current voltage source, the other end is connected with one end of the second direct current bus capacitor, the other end of the second direct current bus capacitor is connected with the cathode of the direct current voltage source, the A-phase bridge arm comprises first to sixth insulated gate bipolar transistors, which are recorded as T1-T6, each insulated gate bipolar transistor is connected with an anti-parallel diode in parallel, the source of T1 is connected with the drain of T2, the source of T2 is connected with the drain of T3, the source of T3 is connected with the drain of T4, the drain of T1 is connected with the anode of a direct-current voltage source, the source of T4 is connected with the cathode of the direct-current voltage source, the source of T5 is connected with a neutral point O, the drain of T1 is connected with the source of T6, the drain of T6 is connected with the neutral point O, the source of T4, the neutral point O is located between the first direct-current bus capacitor and the second-current bus capacitor, the anti-parallel diode connected with T5 is recorded as D5, and the anti-parallel diode connected with T.
In a preferred embodiment of the present invention, the loss in step 2 includes power device conduction loss and power device switching loss, wherein,
the calculation formula of the conduction loss of the power device is as follows:
Pcon＝(a0+a1·Tj)·IL+(b0+b1·Tj)·IL 2
wherein, PconRepresenting the conduction loss of the power device; t isjRepresenting the junction temperature of the device; i isLRepresents the current; a is0、a1、b0、b1Are all coefficients;
the calculation formula of the switching loss of the power device is as follows:
Figure BDA0002598338570000031
wherein E isswRepresenting the switching loss of the power device;
Figure BDA0002598338570000032
representing a switching loss reference value in a data sheet; i isLRepresents the current;
Figure BDA0002598338570000033
current reference values in the data sheet are indicated; vCCRepresents the cut-off voltage;
Figure BDA0002598338570000034
represents the cut-off voltage reference in the data sheet;
Figure BDA0002598338570000035
represents a temperature coefficient; t isjRepresenting the junction temperature of the device;
Figure BDA0002598338570000036
representing device junction temperature reference values in a data manual; kiAnd KvRespectively, representing the exponential coefficients of the current and voltage.
As a preferable embodiment of the present invention, the formula for calculating the life loss in step 4 is:
Figure BDA0002598338570000037
wherein N isfA number of thermal cycles indicative of device failure; delta TjIndicative of junction temperature fluctuations; r represents a gas constant; t isjRepresenting the device junction temperature in kelvin; A. and both alpha and Q are device related parameters.
Compared with the prior art, the invention adopting the technical scheme has the following technical effects:
1. the control strategy optimization design method of the active neutral point clamping type three-level inverter realizes the balance of the loss of the power device by optimizing and adjusting the current conversion paths of the inverter in different voltage states in real time, reduces the junction temperature fluctuation of the power device of the inverter and improves the reliability of the power converter.
2. The invention provides a generalized method for improving the system reliability on line, which is not only suitable for an active neutral point clamped three-level inverter, but also can be used for prolonging the service life of the system by using a similar control strategy in any topological structure capable of changing loss distribution by adjusting a modulation strategy.
3. The reliability index aimed at when the control strategy is designed is the service life of the device, and based on a rain flow method, the optimal commutation path of the inverter can be dynamically determined under random load, and the damage condition of the service life of the device can be very intuitively reflected.
4. The control strategy optimization design method of the active neutral point clamped three-level inverter provided by the invention considers the operation modes of the system under different working conditions of constant load and random load, and the control strategy has wide applicability range and wide application prospect.
Drawings
Fig. 1 shows a topology of an active midpoint clamping type three-level inverter.
Fig. 2 shows the loss distribution of the active midpoint clamping type three-level inverter operating in the passive commutation mode.
Fig. 3 shows the loss distribution of the active midpoint clamping type three-level inverter operating in the active commutation mode.
Fig. 4 is a control strategy design flow for improving the reliable operation capability of the active midpoint clamping type three-level inverter.
Fig. 5 is a hypothetical temperature variation curve of a power device for explaining the rain flow counting method.
Fig. 6 shows a loss variance-based loss balancing strategy under a stable load according to the present invention.
Fig. 7 is a simulation result of accumulated loss of all devices in phase a after the active midpoint clamping type three-level inverter stably operates for 5 seconds in the passive commutation mode, the active commutation mode, and the control strategy for stabilizing the load proposed by the present invention, respectively.
Fig. 8 is a simulation result of device junction temperatures of all devices in phase a after the active midpoint clamping type three-level inverter stably operates for 5 seconds in the passive commutation mode, the active commutation mode, and the control strategy for stabilizing the load according to the present invention.
Fig. 9 is a simulation result of the optimal commutation mode selected by the system under the control strategy of stabilizing the load according to the present invention.
Fig. 10 shows a loss variance-based loss balancing strategy under random load according to the present invention.
Fig. 11 is a load curve of the active midpoint clamping type three-level inverter operating under random load.
Fig. 12 shows the junction temperature simulation result of a specific device after the active midpoint clamping type three-level inverter is stably operated for 20s under the control strategy of the random load proposed by the present invention.
Fig. 13 shows the life loss simulation result of a specific device after the active midpoint clamping type three-level inverter stably operates for 20s under the control strategy of the random load proposed by the present invention.
Fig. 14 is a simulation result of the optimal commutation mode selected by the system under the control strategy of the random load according to the present invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
The invention relates to an optimal design method for a control strategy of an active neutral point clamped three-level inverter, wherein the topological structure of the active neutral point clamped three-level inverter is shown in figure 1. The direct current side is formed by connecting a direct current voltage source Vdc (1.1) and direct current bus capacitors C1 and C2(1.2) in parallel. Each phase bridge arm (1.3) is formed by connecting four Insulated Gate Bipolar Transistors (IGBT) with anti-parallel diodes in series and is connected to a neutral point O through two power devices IGBT. The active neutral point clamped three-level inverter is connected with a resistive inductive load (1.4). According to the switching state of each phase of bridge arm Insulated Gate Bipolar Transistor (IGBT), the corresponding relationship between the switching state and the output voltage is obtained, as shown in table 1.
TABLE 1 correspondence of switch states to output voltages
Figure BDA0002598338570000051
The commutation processes of 16 different currents are arranged and combined according to the 6 switching states of the active midpoint clamping type three-level inverter, as shown in table 2. The 8 commutation processes indicated by the grey shading in the table have current path changes related to D5 or D6 devices and not to T5 or T6 devices, which are similar to the current commutation paths of the midpoint clamping type three-level inverter. While the other 8 commutation processes, the current path change of which is related to the T5 or T6 device and not related to the D5 or D6 device, form a current path by using T5 and T6, which is completely different from the current commutation path of the midpoint clamping type three-level inverter.
Table 2 16 commutation processes of active midpoint clamping type three-level inverter
Figure BDA0002598338570000061
According to the invention, the first type of commutation process is defined as a passive commutation mode, and the second type of commutation process is defined as an active commutation mode, so that the loss distribution of the active commutation mode and the passive commutation mode is completely different due to the difference of commutation paths.
Taking the resistive load as an example, assuming the output current lags the output voltage, four quadrants will be generated according to the current and voltage. The loss distribution of the active midpoint clamping type three-level inverter operating in the passive commutation mode and the active commutation mode is shown in fig. 2 and 3. Fig. 2 shows the commutation process (2.2) and the current path (2.3) for different quadrants (2.1) in the passive commutation mode, as well as the power device (2.4) generating conduction losses and the power device (2.5) generating switching losses during different commutation processes. Fig. 3 shows the commutation process (3.2) and the current path (3.3) for different quadrants (3.1) in the active commutation mode, as well as the power device (3.4) generating conduction losses and the power device (3.5) generating switching losses during different commutation processes. Different commutation modes do not affect the quality of output voltage waveforms and current waveforms, but have different device loss distributions, so that the loss distribution of the system can be optimized according to two commutation modes of the active neutral point clamped three-level inverter by designing a control strategy.
The invention provides a control strategy design process for improving the reliable operation capability of an active neutral point clamped three-level inverter, as shown in fig. 4, the design steps are as follows:
1) according to the current path of the active neutral point clamped three-level inverter, all the commutation processes are divided into two commutation modes: an active commutation mode and a passive commutation mode, and analyzing the loss distribution of the different commutation modes.
2) According to the system (4.1) aimed by the control strategy, voltage and current sensors are used for acquiring voltage at two ends of the power device and current passing through the device, and a characteristic curve in a data manual is fitted to obtain the relation between loss and voltage and current (4.2).
The calculation formula of the conduction loss of the power device is as follows:
Pcon＝(a0+a1·Tj)·IL+(b0+b1·Tj)·IL 2 (1)
in the formula, conduction loss PconAnd current ILApproximation by second order polynomial curve fitting, TjRepresenting the junction temperature of the device, coefficient a0、a1And b0、b1Obtained by curve fitting.
The calculation formula of the switching loss of the power device is as follows:
Figure BDA0002598338570000071
switching loss E in the formulaswAffected by a number of parameters, including: cut-off voltage VCCLoad current ILAnd the junction temperature T of the devicej. The superscript "ref" denotes the reference value in the data sheet. KiAnd KvThe exponential coefficients representing the current and the voltage,
Figure BDA0002598338570000072
indicating the temperature coefficient.
3) And (4) introducing the calculated loss into a Cauer thermal network model of the active midpoint clamping type three-level inverter to estimate the junction temperature of the device (4.3). The parameters of the Cauer thermal network are obtained by the Foster thermal network parameter equivalent transformation provided in the data manual.
4) And (4) using the obtained junction temperature and junction temperature fluctuation for fatigue analysis, and introducing a service life model to calculate the service life loss (4.4) of the device.
The formula for calculating the life loss is as follows:
Figure BDA0002598338570000073
in the formula, NfNumber of thermal cycles, Δ T, indicative of device failurejRepresenting the junction temperature fluctuation, R represents the gas constant (8.314J/mol. K), TjRepresenting the device junction temperature (in kelvin), the device-related parameter a 640, α -5, Q7.8 × 104J/mol。
When junction temperature fluctuates by delta TjAnd junction temperature TmWhen the value is a constant value, the thermal cycle of the device is easy to extract, and the service life damage is easy to calculate. However, the load curve under random load is uncertain, and the thermal cycle of the device is difficult to directly extract, so a cycle counting method is needed to identify the equivalent thermal cycle. The rain flow counting method is a cycle counting method which can extract thermal cycles from random temperature curves, and is widely applied to fatigue analysis.
The invention takes the junction temperature change curve (5.3) of the power device shown in fig. 5 as an example, and a simple introduction is made to the rain flow counting method. First, find the point where the first derivative is 0 in the curve, and if the trend of the first derivative changes from positive to negative, define the point as the peak (5.1). If the first derivative of the point changes from negative to positive, the point is defined as a trough (5.2). These points are numbered in turn. X and Y are generated from the first three points, representing the algebraic difference between successive peak-to-valley points, where Y is the algebraic difference between the first and second points and X is the algebraic difference between the second and third points. Let the starting point be S and start with step 2.
Step 1: and reading the next peak or trough as a new point, and jumping to the step 6 if the next peak or trough does not exist.
Step 2: if now less than 3 points, jump back to step 1. X and Y are regenerated with 3 points that are up-to-date and have not been deleted.
And step 3: comparing the absolute values of X and Y, and if X is less than Y, jumping back to the step 1; and if X is larger than or equal to Y, jumping to the step 4.
And 4, step 4: if Y contains the starting point S, go to step 5. Otherwise, recording Y as a full cycle, then deleting two points of the wave crest and the wave trough contained in Y, and jumping back to the step 2.
And 5: let Y be a half-cycle, then delete the first point (peak or trough) in Y and move the starting point S to the second point in Y. Jump back to step 2.
Step 6: the consecutive peak-to-valley points that have not yet been counted are all defined as half cycles.
The results of the equivalent thermal cycle extracted according to the rain flow method are shown in table 3.
TABLE 3 thermal cycling according to temperature profile using rain flow method
Figure BDA0002598338570000081
The invention adopts a rain flow counting method to extract thermal cycle from the historical junction temperature data of the device, and applies Miner criterion to linearly accumulate the service life damage of the device, and the formula is as follows:
Figure BDA0002598338570000082
wherein D represents the cumulative damage, NiRepresenting the actual number of thermal cycles, N, of a particular operating pointfiIndicating the number of thermal cycles of device failure at a particular operating point. When the value of D reaches 1, device failure is indicated.
4) And analyzing the loss, the junction temperature and the device service life under different modulation strategies, and designing a modulation strategy with optimal reliability and performance as a modulation strategy for system operation. And changing the operation mode of the system in real time according to the designed control strategy, and optimizing the reliability performance of the system (4.5).
According to different current conversion modes and the proposed control strategy design process, two optimized control strategies are respectively designed aiming at different loads.
For stable load, the invention proposes a loss balancing strategy based on loss variance, and the control block diagram is shown in fig. 6. The control strategy estimates the conduction loss and the switching loss of each device by collecting current and voltage signals on line and combining characteristic curves in a data manual of the semiconductor device (6.4). On one hand, the obtained loss is introduced into a Cauer thermal model and used for calculating the junction temperature (6.5) of the device, and the calculated temperature is used for updating the loss (6.4) of the power device in real time; on the other hand, the loss is used for comparing the loss variance of the active neutral point clamped three-level inverter in two commutation modes, and the commutation mode with the minimum loss variance is selected as the optimal commutation mode (6.6). Finally, according to the optimal commutation mode (6.6) and the given voltage (6.1), the control signal generates gate pulse signals (6.2) of 18 IGBTs, and the switching state (6.3) of an Insulated Gate Bipolar Transistor (IGBT) device in the active neutral point clamping type three-level inverter is determined.
The designed control strategy is simulated, and when the system stably works for 5s in the passive commutation mode (7.1), the active commutation mode (7.2) and the control strategy (7.3) provided by the invention, the accumulated loss of all devices in the phase A is shown in figure 7. After the system is stably operated for 5s in the passive commutation mode (8.1), the active commutation mode (8.2) and the control strategy (8.3) proposed by the present invention, the device junction temperatures of all devices in phase a are shown in fig. 8. Fig. 9 shows the optimal commutation mode (9.1) selected by the system, wherein 0 represents the passive commutation mode and 1 represents the active commutation mode. As can be seen from fig. 7, the cumulative loss of the power device in the commutation mode proposed by the present invention is between the cumulative losses of the device in both commutation modes, because the commutation mode proposed by the present invention always switches back and forth between the passive commutation mode and the active commutation mode. As can be seen from fig. 7 and 8, the junction temperature profiles of the different commutation modes are consistent with the loss profiles. Table 4 lists the accumulated losses, the variance of the losses, the highest device junction temperature and the variance of the junction temperature for the different commutation modes.
Table 4 comparison between different commutation modes
Figure BDA0002598338570000091
As can be seen from table 4, although the accumulated loss is the same in different commutation modes, in the commutation mode proposed by the present invention, the loss variance and the junction temperature variance of the device are lower than those of the other two commutation modes. This shows that the present invention proposes that the loss and junction temperature profiles of the commutation mode are more uniform. In addition, in the current conversion mode provided by the invention, the highest device junction temperature is smaller than that in other two current conversion modes, and because the junction temperature is related to the service life of the device and the device with the most serious service life loss determines the reliability of the whole system, the current conversion mode provided by the invention can avoid the situation that part of the devices are damaged in advance due to the over-high junction temperature, so that the service life of the system is prolonged and the reliability of the system is improved.
The loss balancing strategy can be suitable for both steady-state loads and random loads. But for already used devices it is necessary to know the initial cumulative loss of the device in order to use the strategy. The model cannot predict the service life of the device, and cannot adjust the commutation mode in real time according to the service life of the device, so that the invention provides another control strategy for improving the reliability of the system under random load, and a control block diagram of the control strategy is shown in fig. 10.
Under the random load control strategy provided by the invention, the calculation modes of the loss (10.4) and the junction temperature (10.5) of the power device are consistent with the control strategy based on the loss variance, but the difference is that the continuously changing load can generate larger junction temperature fluctuation, so that the service life calculation of each device is realized. After a load period, according to the calculated junction temperature data of the device, a rain flow meter algorithm is adopted to extract the thermal cycle (10.6) of the device from the historical temperature data of the device, and then the residual life of each Insulated Gate Bipolar Transistor (IGBT) module can be accurately calculated and stored (10.7). And then comparing the residual life variances of all Insulated Gate Bipolar Transistor (IGBT) modules in different commutation modes, and selecting the commutation mode with the minimum life variance as the optimal commutation mode as the commutation mode running in the next load cycle (10.8). Finally, according to the optimal commutation mode (10.8) and the given voltage (10.1), the control signal generates gate pulse signals (10.2) of 18 insulated gate bipolar transistors, and the final switch state (10.3) of the active neutral point clamping type three-level inverter is determined.
And simulating the designed control strategy, and assuming that the initial damage of the device is 0, and the system initially operates in a passive commutation mode. After the system is operated for 20s under the control strategy, the simulation results are shown in fig. 11, 12, 13 and 14.
And (11.1) is a load curve set under random load. Fig. 12 shows the junction temperature of the IGBT1 module (12.1), the junction temperature of the IGBT2 module (12.2), and the junction temperature of the IGBT5 module (12.3). As can be seen from fig. 11 and 12, at the set random load, the load curve varies irregularly with time (11.1) and results in irregular variation of device junction temperature with output power. Fig. 13 shows the cumulative lifetime loss of all igbt modules for phase a under random load, including: lifetime of IGBT1 module (13.1), lifetime of IGBT2 module (13.2), lifetime of IGBT3 module (13.3), lifetime of IGBT4 module (13.4), lifetime of IGBT5 module (13.5) and lifetime of IGBT6 module (13.6). It can be seen that the service life loss of the insulated gate bipolar transistor module is increased every time a calculation cycle of a rain flow method is passed. However, the increment of the service life loss of the insulated gate bipolar transistor module in each calculation period is different because the load is random. Fig. 14 shows the commutation mode with the smallest residual life variance (14.1), where 0 represents the passive commutation mode and 1 represents the active commutation mode, and it is found that the best commutation mode selected is always the active commutation mode except when the system is initially operating in the passive commutation mode.
The two control strategies conclude differently because: 1. under a stable load, the reliability index aimed at when the control strategy is designed is the device loss, and the reliability index aimed at by the random load is the device life. 2. In a control strategy under random load, a device aiming at life loss is an Insulated Gate Bipolar Transistor (IGBT) module, and the junction temperature of the insulated gate bipolar transistor is selected to represent the junction temperature of the whole Insulated Gate Bipolar Transistor (IGBT) module. In the control strategy under the stable load, the junction temperature calculation includes the junction temperature of an Insulated Gate Bipolar Transistor (IGBT) and the junction temperature of an anti-parallel diode of the IGBT.
Although the commutation mode with the smallest device lifetime variance in the control strategy designed under random load is always the active commutation mode, this does not represent that the design of the control strategy is meaningless. The invention aims to provide a generalized control strategy design method for improving the reliable operation capability of a system on line, which designs a control strategy by acquiring the accumulated loss of a device in a fixed time period in real time, adjusts the operation mode of the system and improves the reliability of the system. Therefore, the control strategy provided by the invention is not only suitable for the active clamping type three-level inverter, but also any topological structure (such as a multilevel active clamping type converter) which can change loss distribution by adjusting a modulation strategy can use a similar control strategy to prolong the service life of the system, and the applicability range of the control strategy is very wide.
The control strategy provided by the invention can maintain the output waveform performance of the active clamping type three-level inverter, optimize the loss distribution of the system, optimize the junction temperature distribution of the system and enhance the reliability of the system. Meanwhile, corresponding control strategies are designed aiming at different types of loads, the operation modes of the system under different working conditions are considered, and the method has good applicability.
The above embodiments are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modifications made on the basis of the technical scheme according to the technical idea of the present invention fall within the protection scope of the present invention.

Claims (4)

1. An active neutral point clamped three-level inverter control strategy optimization design method is characterized by comprising the following steps:
step 1, dividing all commutation processes into two commutation modes according to a current path of an active neutral point clamped three-level inverter: an active commutation mode and a passive commutation mode, and analyzing loss distribution of different commutation modes;
step 2, acquiring voltages at two ends of a power device in the active neutral point clamped three-level inverter by using a voltage sensor, acquiring current passing through the power device in the active neutral point clamped three-level inverter by using a current sensor, and fitting a characteristic curve in a data manual to obtain a relation between loss and the voltage and the current;
step 3, substituting the voltage and the current obtained in the step 2 into the relation between the loss and the voltage and the current, calculating to obtain the loss, and introducing the loss into a heat network model to estimate the junction temperature of the power device;
step 4, acquiring the junction temperature of the power device in a time period, extracting thermal cycles from the junction temperature of the power device in the time period by adopting a rain flow counting method, using the thermal cycles for fatigue analysis, and introducing a life model to calculate the life loss of the power device;
step 5, aiming at the stable load, selecting a current conversion mode with the minimum loss variance as a current conversion mode for system operation according to the loss distribution conditions of different current conversion modes;
and 6, aiming at random loads, selecting the commutation mode with the minimum service life loss variance as the commutation mode of system operation according to the service life loss distribution conditions of different commutation modes.
2. The method according to claim 1, wherein step 1 is performed by dividing all commutation processes into two commutation modes: the active commutation mode and the passive commutation mode specifically include:
according to 6 switch states of the active neutral point clamping type three-level inverter, 16 kinds of commutation processes with different currents are arranged and combined, wherein the current path change of 8 kinds of commutation processes is related to D5 or D6 and is unrelated to T5 or T6, the current path change of the other 8 kinds of commutation processes is related to T5 or T6 and is unrelated to D5 or D6, the former 8 kinds of commutation processes are defined as passive commutation modes, and the latter 8 kinds of commutation processes are defined as active commutation modes;
the active neutral point clamping type three-level inverter comprises a direct-current voltage source, first to second direct-current bus capacitors and an A-phase bridge arm; one end of the first direct current bus capacitor is connected with the anode of the direct current voltage source, the other end is connected with one end of the second direct current bus capacitor, the other end of the second direct current bus capacitor is connected with the cathode of the direct current voltage source, the A-phase bridge arm comprises first to sixth insulated gate bipolar transistors, which are recorded as T1-T6, each insulated gate bipolar transistor is connected with an anti-parallel diode in parallel, the source of T1 is connected with the drain of T2, the source of T2 is connected with the drain of T3, the source of T3 is connected with the drain of T4, the drain of T1 is connected with the anode of a direct-current voltage source, the source of T4 is connected with the cathode of the direct-current voltage source, the source of T5 is connected with a neutral point O, the drain of T1 is connected with the source of T6, the drain of T6 is connected with the neutral point O, the source of T4, the neutral point O is located between the first direct-current bus capacitor and the second-current bus capacitor, the anti-parallel diode connected with T5 is recorded as D5, and the anti-parallel diode connected with T.
3. The method of claim 1, wherein the losses in step 2 include power device conduction losses and power device switching losses, and wherein,
the calculation formula of the conduction loss of the power device is as follows:
Pcon＝(a0+a1·Tj)·IL+(b0+b1·Tj)·IL 2
wherein, PconRepresenting the conduction loss of the power device; t isjRepresenting the junction temperature of the device; i isLRepresents the current; a is0、a1、b0、b1Are all coefficients;
the calculation formula of the switching loss of the power device is as follows:
Figure FDA0002598338560000021
wherein E isswRepresenting the switching loss of the power device;
Figure FDA0002598338560000022
representing a switching loss reference value in a data sheet; i isLRepresents the current;
Figure FDA0002598338560000023
current reference values in the data sheet are indicated; vCCRepresents the cut-off voltage;
Figure FDA0002598338560000024
represents the cut-off voltage reference in the data sheet;
Figure FDA0002598338560000027
represents a temperature coefficient; t isjRepresenting the junction temperature of the device;
Figure FDA0002598338560000025
representing device junction temperature reference values in a data manual; kiAnd KvRespectively, representing the exponential coefficients of the current and voltage.
4. The method of claim 1, wherein the lifetime loss in step 4 is calculated by the following formula:
Figure FDA0002598338560000026
wherein N isfA number of thermal cycles indicative of device failure; delta TjIndicative of junction temperature fluctuations; r represents a gas constant; t isjRepresenting the device junction temperature in kelvin; A. and both alpha and Q are device related parameters.
CN202010716414.XA 2020-07-23 2020-07-23 Control strategy optimization design method for active neutral point clamped three-level inverter Pending CN111987926A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202010716414.XA CN111987926A (en) 2020-07-23 2020-07-23 Control strategy optimization design method for active neutral point clamped three-level inverter

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202010716414.XA CN111987926A (en) 2020-07-23 2020-07-23 Control strategy optimization design method for active neutral point clamped three-level inverter

Publications (1)

Publication Number Publication Date
CN111987926A true CN111987926A (en) 2020-11-24

Family

ID=73438103

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202010716414.XA Pending CN111987926A (en) 2020-07-23 2020-07-23 Control strategy optimization design method for active neutral point clamped three-level inverter

Country Status (1)

Country Link
CN (1) CN111987926A (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112803804A (en) * 2021-02-01 2021-05-14 中南大学 Single-phase three-level rectifier parameter compensation temperature balance control method and system
CN112896200A (en) * 2021-01-27 2021-06-04 株洲中车时代电气股份有限公司 Locomotive traction force distribution method and device for reducing service life loss of IGBT module
CN115065223A (en) * 2022-08-18 2022-09-16 杭州飞仕得科技有限公司 Optimization control method and device for active clamp three-level circuit

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102013825A (en) * 2010-11-30 2011-04-13 中国南方电网有限责任公司电网技术研究中心 Loss analysis method for diode clamping type three-level voltage source converter (VSC)
CN106712553A (en) * 2016-12-30 2017-05-24 江苏中科君芯科技有限公司 IGBT junction temperature fluctuation calculation method for sine inverter

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102013825A (en) * 2010-11-30 2011-04-13 中国南方电网有限责任公司电网技术研究中心 Loss analysis method for diode clamping type three-level voltage source converter (VSC)
CN106712553A (en) * 2016-12-30 2017-05-24 江苏中科君芯科技有限公司 IGBT junction temperature fluctuation calculation method for sine inverter

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
张兵: "有源箝位型三相三电平逆变器控制策略研究", 《中国优秀博硕士学位论文全文数据库》 *
王亚洲: "MMC的结温波动优化控制策略及其可靠性分析", 《中国优秀博硕士学位论文全文数据库》 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112896200A (en) * 2021-01-27 2021-06-04 株洲中车时代电气股份有限公司 Locomotive traction force distribution method and device for reducing service life loss of IGBT module
CN112803804A (en) * 2021-02-01 2021-05-14 中南大学 Single-phase three-level rectifier parameter compensation temperature balance control method and system
CN115065223A (en) * 2022-08-18 2022-09-16 杭州飞仕得科技有限公司 Optimization control method and device for active clamp three-level circuit
CN115065223B (en) * 2022-08-18 2022-11-29 杭州飞仕得科技有限公司 Optimization control method and device for active clamp three-level circuit

Similar Documents

Publication Publication Date Title
CN107341326B (en) Service life evaluation method for modular multilevel converter
CN111987926A (en) Control strategy optimization design method for active neutral point clamped three-level inverter
CN112464443B (en) Calculation method for IGBT junction temperature fluctuation of power electronic converter
CN107508281B (en) Dynamic reliability assessment method for power flow controller of in-phase power supply system
Zhang et al. Optimized switching finite control set model predictive control of NPC single-phase three-level rectifiers
CN105811771B (en) A kind of determination method based on the loss of MMC isolated form DC/DC converter switches
CN103324843A (en) Modular multilevel converter (MMC) valve loss calculation method applicable to different sub-module types
CN108631632B (en) MMC instantaneous power loss calculation method based on virtual bridge arm mathematical model
CN104811069A (en) Prediction control method for modularized multi-level inverter
Sangwongwanich et al. Two-dimension sorting and selection algorithm featuring thermal balancing control for modular multilevel converters
Monteiro et al. Novel single-phase five-level VIENNA-type rectifier with model predictive current control
US20230387785A1 (en) Method and Apparatus for Efficient Switching
CN111585298A (en) Power electronic transformer reliability analysis method and system for battery energy storage
de Andrade et al. Power losses in photovoltaic inverter components due to reactive power injection
CN112733071B (en) Dynamic loss and total loss calculation method of MMC converter valve under NLC modulation
CN115168786A (en) Converter valve loss determination method of optical storage direct-flexible MMC converter
CN107786110B (en) MMC submodule topological structure modulation method based on H bridge
Yeganeh et al. Dynamic Performance Optimization of Single-Phase Inverter based on Model Predictive Control
Mohan et al. Design approach for high power, medium voltage power conversion systems for wind turbines
CN113381627A (en) High-power NPC three-level PWM rectifier prediction control method and device
CN115812274A (en) Inverter common mode voltage injection control method and device
Xia et al. Investigation of Hybrid Three-Level Hybrid Device (Hybrid 2) Active Neutral-Point-Clamped Converter
JP7492926B2 (en) Inverter devices, motor drive devices, and refrigeration equipment
Cui et al. Frequency reduction-based model predictive direct power control with multi-cost function
Haering et al. Switching Behaviour of a SiC-MOSFET 3-Level ANPC Inverter with Different Modulation Schemes

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
RJ01 Rejection of invention patent application after publication

Application publication date: 20201124

RJ01 Rejection of invention patent application after publication