CN111817581B - Operation control method and system of multi-level converter - Google Patents
Operation control method and system of multi-level converter Download PDFInfo
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Abstract
The utility model provides an operation control method and a control system of a multi-level converter, which collects the temperature and the voltage of a capacitor in the operation process when the multi-level converter is in a stable working state, and the junction temperature fluctuation times, the junction temperature fluctuation average value, the maximum value and the amplitude value in unit time in the operation process of an IGBT; acquiring a capacitance fault rate and an IGBT fault rate based on the acquired capacitance and IGBT operation data; calculating the fault rate of the sub-modules of the multilevel converter according to the fault rate of the capacitor and the fault rate of the IGBT; determining an optimal maintenance period of the multi-level converter in a future period of time based on the fault rate of the sub-modules of the multi-level converter; and issuing a control command to control the working or shutdown running state of the multilevel converter based on the optimal maintenance period.
Description
Technical Field
The disclosure belongs to the field of flexible direct current transmission of a power system, and particularly relates to an operation control method and a control system of a multi-level converter.
Background
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
As a new generation of direct current transmission technology, the flexible direct current transmission technology is developed rapidly, and the multi-level converter MMC has good application prospect and development potential in the flexible direct current transmission project. However, the safe and stable operation of the multilevel converter MMC is influenced along with the failure and invalidation of key components in the operation process of the multilevel converter MMC, and the guarantee of the reliable operation of the multilevel converter MMC has important significance for guaranteeing the safe and stable of actual power transmission engineering.
MMC reliability needs to be considered in the operation control process of the multi-level converter, and related researches on the MMC reliability mainly focus on the aspects of component service life evaluation, redundancy and fault-tolerant design, structure optimization, periodic maintenance and the like. Among them, Wangbiyang et al published IEEE Transactions on Power Delivery in 2017 on a Reliability model of MMC systematic predictive mail, proposed an MMC mathematical Reliability model considering regular preventive maintenance, and analyzed the sensitivity of Reliability to redundancy and maintenance interval, but did not relate to the selection of an optimal maintenance strategy. Liu Lu Jie et al published ' China Motor engineering reports ' preventive maintenance strategy optimization based on reliability and maintenance priority ' in 2016, and the preventive maintenance strategy based on reliability and maintenance priority is proposed in consideration of the special environment of the offshore wind turbine, and the maintenance range of the turbine is calculated by taking the optimal cost per unit time of maintenance as a criterion. But the reliability model of the equipment is simpler, and the influence of redundant devices in the k/n system on the maintenance period is not considered.
The operation state based on the multilevel converter has important significance for evaluating the reliability of the MMC, and the technical problems existing in the operation control of the current multilevel converter mainly concentrate on:
1. the redundant sub-modules are configured in the multi-level converter, so that the influence of sub-module faults on a direct-current transmission system where the multi-level converter is located can be avoided, but when the redundant sub-modules have faults, the three-phase voltage of the multi-level converter is unbalanced, and the safe and stable operation of the direct-current transmission system is influenced.
2. In order to ensure the safe and stable operation of the multi-level converter, the multi-level converter is maintained within a certain time, the factors considered in the current maintenance are mainly the operation time, the maintenance cost and the like of the multi-level converter, and the historical operation state of the multi-level converter is not considered, so that the control on the operation state of the level converter is not accurate enough.
Disclosure of Invention
In order to overcome the defects of the prior art, the present disclosure provides an operation control method of a multilevel converter, which can accurately control the operation state of the multilevel converter by considering the historical operation state of the multilevel converter.
In order to achieve the above object, one or more embodiments of the present disclosure provide the following technical solutions:
in a first aspect, an operation control method for a multilevel converter is disclosed, which includes:
collecting the temperature and voltage of a capacitor in the operation process when the multi-level converter is in a stable working state, and the junction temperature fluctuation times, the junction temperature fluctuation average value, the maximum value and the amplitude value in unit time in the operation process of the IGBT;
acquiring a capacitance fault rate and an IGBT fault rate based on the acquired capacitance and IGBT operation data; calculating the fault rate of the sub-modules of the multilevel converter according to the fault rate of the capacitor and the fault rate of the IGBT;
determining an optimal maintenance period of the multi-level converter in a future period of time based on the fault rate of the sub-modules of the multi-level converter; and issuing a control command to control the working or shutdown running state of the multilevel converter based on the optimal maintenance period.
In a second aspect, an operation control system of a multilevel converter is disclosed, which includes: a controller configured to:
receiving the temperature and voltage of a capacitor in the operation process when the multi-level converter is in a stable working state, and the junction temperature fluctuation times, the junction temperature fluctuation average value, the maximum value and the amplitude value within unit time in the operation process of the IGBT;
acquiring a capacitance fault rate and an IGBT fault rate based on the acquired capacitance and IGBT operation data; calculating the fault rate of the sub-modules of the multilevel converter according to the fault rate of the capacitor and the fault rate of the IGBT;
determining an optimal maintenance period of the multi-level converter in a future period of time based on the fault rate of the sub-modules of the multi-level converter; and issuing a control command to control the working or shutdown running state of the multilevel converter based on the optimal maintenance period.
The above one or more technical solutions have the following beneficial effects:
according to the technical scheme, the capacitance fault rate and the IGBT fault rate are calculated by obtaining data (temperature and voltage in the capacitor operation process, junction temperature fluctuation times in unit time in the IGBT operation process, junction temperature fluctuation average value, maximum value and amplitude) of the MMC in the historical operation state; the fault rate of the sub-module of the multilevel converter is calculated according to the fault rate of the capacitor and the fault rate of the IGBT, the running state of the sub-module is accurately evaluated based on the fault rate, an optimal maintenance period is obtained after the running state of the whole MMC is evaluated, and the running state of the MMC is controlled based on the optimal maintenance period, so that the whole MMC is ensured to be in a stable state, the fault during running is avoided, and the safe and stable running of the whole direct current system is ensured.
According to the technical scheme, the fault rate parameter of the MMC element and the cost parameter of the MMC are obtained, the parameters can be obtained through a monitoring system of the MMC, a bridge arm state transition probability graph is obtained through processing after the parameters are obtained, index calculation is carried out based on the graph, repeated calculation of a large amount of data is avoided, data processing efficiency is improved, used memory of a processor is reduced, and the optimal maintenance period corresponding to the basic parameter data of the MMC can be output quickly after the basic parameter data of the MMC are obtained.
This disclosed technical scheme formulates reasonable many level transverter MMC maintenance strategy through the reliability model that combines operating condition, carries out appropriate preventive maintenance before the system breaks down, can effectively avoid partial fault shutdown accident, and then reduces long-term operation loss, effectively improves MMC long-term operation's reliability.
Drawings
The accompanying drawings, which are included to provide a further understanding of the disclosure, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure and are not to limit the disclosure.
Figure 1 is a markov chain of a single bridge arm proposed by the present invention;
FIG. 2 is a schematic diagram of an age replacement strategy;
FIG. 3 is a schematic diagram of a batch replacement strategy;
FIG. 4 is a graph of the required maintenance cost per unit time (age change);
fig. 5 is a graph of the maintenance costs (batch replacement) required per unit time.
Detailed Description
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
The embodiments and features of the embodiments in the present disclosure may be combined with each other without conflict.
The MMC is a multi-level converter and comprises three phases, wherein the three phases share one direct current bus, each phase comprises two bridge arms, and each bridge arm is formed by connecting a plurality of sub-modules in series. The controllable switching elements such as Insulated Gate Bipolar Transistors (IGBTs) are used, so that the method has the characteristics of less output harmonic waves, high modularization degree and the like, has wide application prospect in a power system, and is often applied to High Voltage Direct Current (HVDC), static synchronous compensators (STATCOM) and the like.
In the reliability analysis, the current research basically uses the MMC as an unmovable model, and for the MMC, if a shutdown fault occurs, maintenance is required and the operation is continued, so that the MMC is used as a repairable system for analysis.
The power equipment or the power electronic device is mostly regarded as a series model or a model configured with a single standby module, the maintenance strategy can be analyzed by respectively referring to a series system and a parallel system, and the whole process is simple; in comparison, the MMC is considered as a k/n model because the redundant sub-module is configured in the bridge arm, so that the analysis process of the maintenance strategy is more complicated, specifically: the existence of redundant sub-modules makes it unnecessary to perform maintenance when some sub-modules fail, and performing maintenance does not mean that all redundant sub-modules fail, so that the establishment of a maintenance strategy needs to consider more factors.
According to the technical scheme, the MMC is used as a repairable system to establish a Markov model, so that an MMC usability evaluation parameter is deduced; and selecting the optimal maintenance period, considering an age replacement strategy and a batch replacement strategy related to economy, and further obtaining the optimal maintenance period of the MMC under different maintenance strategies. According to the method, the usability index which is more in line with the reality is deduced through the establishment of the repairable Markov model, the influence of the regular maintenance period of the MMC on the economy is quantized through the analysis of the optimal maintenance strategy, and then reference is provided for the selection of the optimal maintenance period.
The embodiment discloses an operation control method of a multilevel converter, which comprises the following specific processes:
collecting the temperature and voltage of a capacitor in the operation process when the multi-level converter is in a stable working state, and the junction temperature fluctuation times, the junction temperature fluctuation average value, the maximum value and the amplitude value in unit time in the operation process of the IGBT;
acquiring a capacitance fault rate and an IGBT fault rate based on the acquired capacitance and IGBT operation data; calculating the fault rate of the sub-modules of the multilevel converter according to the fault rate of the capacitor and the fault rate of the IGBT;
determining an optimal maintenance period of the multi-level converter in a future period of time based on the fault rate of the sub-modules of the multi-level converter; and issuing a control command to control the working or shutdown running state of the multilevel converter based on the optimal maintenance period.
In a more specific implementation example, after data of the multi-level converter in a stable working state is collected, data preprocessing is firstly performed, repeated data is deleted, and missing data is completed.
And storing the preprocessed data according to the time tag for evaluating the operation state of the multilevel converter in a time period, and acquiring the operation state data of the multilevel converter in the next operation time period again to evaluate the operation state of the multilevel converter in the time period.
For example, in 1-6 months, historical operating data of the multilevel converter in 1-3 months is collected for evaluating the operating state of the multilevel converter, determining which time point in 3-6 months can be used as an optimal maintenance period, and controlling the multilevel converter to stop in the maintenance period for preventive maintenance to avoid sudden failure and influence on the safe and stable operation of the whole direct current system.
In a more specific implementation example, the actual operation data of the multilevel converter in a stable operating state for a period of time is collected, and the data content is as follows:
the total number n of MMC sub-modules (including redundant sub-modules) and the number k of the sub-modules required by normal operation of the MMC. The temperature and voltage in the operation process of the capacitor, the junction temperature fluctuation times in unit time in the operation process of the IGBT, the junction temperature fluctuation average value, the maximum value and the amplitude.
The calculation process of the capacitance fault rate is as follows:
solving the voltage acceleration factor through the voltage of the capacitor in the engineering:
wherein U is a reference voltage; u shapenFor the actual applied voltage, a and b are constants.
Solving a temperature acceleration factor through temperature parameters of capacitors in engineering:
where ξ is a constant coefficient, TnFor reference temperature, T is the operating temperature.
Considering the acceleration effect of temperature and voltage on the corrosion rate, the failure rate of the capacitor is as follows:
λcap＝λ0×πT×πU (3)
the IGBT failure rate is calculated as follows. Solving the thermal stress factor through the junction temperature average value of the IGBT in the engineering:
wherein both alpha and beta are constants, the specific values corresponding to different elements are different, and T isjIs the junction temperature.
In a specific implementation example, the temperature cycle factor is solved through the junction temperature fluctuation times and the maximum value and amplitude of the junction temperature fluctuation in unit time of the IGBT in the engineering:
wherein: t is the accumulated running time of the element; n is a radical ofcyThe number of junction temperature cycle fluctuations of the element; n is a radical of0Is a reference cycle fluctuation number; thetacyCycling time for the junction temperature fluctuation of the element; theta0Is a reference cycle time; delta TcyIs the junction temperature fluctuation amplitude of the element; t ismax,cyThe maximum value of the fluctuation of the junction temperature of the element is obtained; gamma, rho and eta are adjustment coefficients of different elements.
Considering the influence of junction temperature cycle on the IGBT, the failure rate of the IGBT is as follows:
λ＝(λ0ThπTh+λ0TCπTC)πinπPmπPr (6)
wherein: lambda [ alpha ]0ThAnd λ0ThThe basic failure rates of the elements are respectively corresponding to the thermal stress factor and the temperature cycle factor; piThAnd piThThermal stress factor and temperature cycle factor; piinAn overstress contributor factor for the element; piPmIs the effect of the manufacturing quality of the component; piPrThe effect of the reliability quality management and control level in the life cycle of the element.
According to the fault rates of the capacitor and the IGBT, the fault rate of the MMC sub-module can be calculated:
λ＝λIGBT1+λIGBT2+λcap (7)
λ represents the failure rate of the submodule, λIGBT1、λIGBT1Respectively represents the failure rate, lambda, of the upper IGBT and the lower IGBT in the submodulecapIndicating the failure rate of the capacitor.
And establishing an MMC Markov repairable model by using the obtained sub-module fault rate, as shown in figure 1, and deducing the reliability index of the MMC under the repairable model.
The modeling process is as follows: the MMC Markov model can be repaired, because the setting of redundant submodule piece, the trouble of portion molecule module (the trouble submodule piece number is less than or equal to the redundant submodule piece number of configuration) can not cause the trouble of MMC, when having the submodule piece to break down again after redundant submodule piece is whole to drop into, the MMC breaks down and can't work, shuts down this moment and changes all trouble submodule pieces. n is the total number of the submodules configured in the system, and k is the number of the submodules required by the normal operation of the system (k is less than or equal to n). And defining the number of the fault sub-modules in the system as the state of the system, wherein the system has n-k +2 different states. All states of the bridge arm include: Ω ═ 0,1, ·, n-k +1}, and the normal state includes: w ═ 0,1, ·, n-k }, the fault status is: f ═ n-k +1 }. Each sub-module life distribution is 1-e-λtT is more than or equal to 0, and the total replacement time after the bridge arm fault is 1-e-μt，t≥0,μ>0, mu is the post-failure repair rate. After the failed SMs are replaced, the service life distribution is the same as that of the new SMs. Setting the life distribution of each submodule and the distribution of the replacement time after the fault can establish a bridge arm state transition probability chart, as shown in fig. 1. And deducing the reliability index of the MMC under the repairable model according to the state transition probability diagram, thereby providing parameters for the establishment of a maintenance strategy.
And deducing the reliability index of the MMC under the repairable model. The method specifically refers to steady-state and transient reliability indexes of the system, wherein the steady-state reliability indexes comprise steady-state availability, system reliability and average time before first failure; the transient reliability index comprises the transient fault frequency of the system and the average fault frequency within (0-t) time. The specific calculation process is as follows:
the state transition probability map shown in fig. 1 represents the probability of a system state transition within Δ t time, and a transition rate matrix can be written:
therefore, steady-state and transient reliability indexes of the system can be obtained by carrying out correlation calculation.
According to Markov model related knowledge, the steady-state availability of the bridge arm is as follows:
wherein, piiI ∈ W satisfies the system of linear equations:
the system reliability and the mean time before first failure are respectively
Wherein
B is the submatrix of the top left n-k +1 rows and n-k +1 columns related to A.
The system instantaneous reliability index is solved below. According to the transfer rate matrix, the transient fault frequency of the system is as follows:
wherein, Pi(t), i ∈ W is the solution of the following formula under the initial condition P (0):
and integrating the transient fault frequency to obtain the average fault frequency of the bridge arm in the time from (0 to t).
And determining the optimal maintenance period selection method of the MMC under the minimum cost model by using the reliability index of the MMC under the repairable model.
The MMC optimal maintenance period is determined through an MMC minimum cost model, the MMC minimum cost model is established in the process, the derived MMC reliability indexes under the repairable model are applied, and the specific establishing process is as follows:
MMC is considered as a hot standby model of a k/n redundant system, and an age replacement strategy and a batch replacement strategy are considered respectively. In the age replacement strategy, there may be two cases during a cycle: the MMC normally operates to the point of preventive maintenance and the MMC fails before the scheduled maintenance point, as shown in fig. 2. When the MMC normally operates to the moment of preventive maintenance, the MMC can still normally operate, and then the fault sub-module is replaced at the end of the maintenance period, and preventive maintenance is carried out on the normal sub-module; if a shutdown fault occurs before the expected maintenance time, namely the number of the sub-modules with faults is larger than the configured redundancy number, the sub-modules with faults are replaced at the time of the fault, and preventive maintenance is carried out on the normal sub-modules.
According to the existing reliability model, the cost per unit time is as follows:
the cost of each SM failover is recorded as crCost per SM preventative maintenance of cwThe system loss resulting from a planned shutdown of an MMC by preventative maintenance (including economic and other losses resulting from preventative maintenance) is cpTotal cost of preventive maintenance of inverter is Cp. If a failure of the front axle arm occurs at the end of the expected maintenance period TAnd c, the fault is replaced after the fault SMs is failed, the normally working SMs are maintained and repaired as new, and the loss (including economic loss and other loss caused by forced shutdown) caused by forced shutdown of the converter caused by replacement after the fault to the system is cfTotal cost of replacement after converter failure is Cf。
And if the converter normally operates to the expected maintenance time, the number of the failed SMs in the bridge arm does not exceed n-k, the bridge arm normally works, the SMs are maintained or replaced at the end of the expected maintenance period, and the actual maintenance period is T at the moment. The probability that the bridge arm normally works in the expected maintenance period T is as follows:
when the number of failed SMs of the bridge arm reaches n-k before time T (0< T < T), and another SM in the bridge arm fails at time T, the bridge arm fails to operate, and is maintained and replaced immediately at the moment, wherein the actual maintenance period is T. After the number of failed SMs reaches n-k, the sub-modules which normally operate form a series system, the failure rate of the series system is k lambda, and according to the definition of the failure rate, the probability of the series system failing in a time interval (t-delta t) is as follows:
Pt＝kλ·Δt (19)
by combining the probabilities of the two situations, the average period of the system is as follows:
cost for preventive maintenance CpIn other words, the number of failed SMs does not exceed n-k when the converter is serviced. When this occurs, preventive maintenance costs CpIncluding replacement costs for all possible failed SMs, maintenance costs for properly functioning SMs, and losses due to planned system shutdowns cpNamely:
when forced shutdown happens, the number of failed SMs in the bridge arm is n-k +1, and the total cost C of replacement after failurefReplacement costs (n-k +1) c comprising n-k +1 failed SMsrMaintenance cost of k-1 Normal SMs (k-1) cwAnd the loss c caused by forced shutdown of the inverterf，CfCan be expressed as:
summarizing the above discussion may lead to C1(T) is:
the batch replacement strategy mainly takes two maintenance approaches: preventive maintenance is carried out on the sub-modules at fixed time intervals; failure results in replacement of the failed sub-module at shutdown, as shown in fig. 3. In a maintenance period, when a fault occurs, stopping the machine to replace the fault submodule; at the end of the maintenance period, all the submodules are uniformly and preventively maintained.
The total maintenance cost per unit time can be expressed as:
the expected number of post-fault shutdown repairs, expressed in N (T), over time (0-T), can be obtained from the reliability model. And in a maintenance period T, when a fault occurs, stopping the machine to replace the SMs with the fault. The replacement cost during period T includes the total replacement cost for the failed SMs and the loss due to forced shutdown of the inverter.
Cf2＝N(T)·(cr·(n-k+1)+cf) (25)
The MMC is considered to be operating properly at the end of the maintenance cycle because (9) includes the total cost of the cycle due to the shutdown. The number of faulty sub-modules is less than or equal to n-k at the end of the maintenance period. By t0Representing the time interval between the last shutdown in the cycle and the end of the maintenance cycle, then t0T-n (T) MTTF. After n (T) update procedures, the number of submodules to be replaced at time T can be calculated with reference to (2). At the end of a maintenance cycle, all the smss are collectively maintained preventively, and the periodic maintenance costs at the end of the cycle include maintenance costs for normal smss, replacement costs for failed smss, and losses due to scheduled converter outages.
Summarizing the above discussion may lead to C2(T) is:
c obtained according to the above discussion1(T)、C2And (T), selecting actual parameters to draw a function curve of the converter, so that the optimal maintenance period T can be obtained, and the unit time operation cost of the converter is the lowest.
Specifically, for an MMC, a fault rate parameter of an element (including fault rate parameters of an IGBT module, a capacitor, a control system, and a power driving system), a cost parameter of the MMC (including sub-module maintenance cost, sub-module replacement cost, system loss due to planned shutdown, and system loss due to planned shutdown) need to be obtained, and the cost parameter is substituted into a minimum cost model, so that a maintenance period-unit time maintenance cost curve can be drawn, the influence of different maintenance periods on the unit time maintenance cost is shown, a minimum value point of the unit time maintenance cost is obtained according to the curve, and a maintenance period corresponding to the minimum value point is an optimal maintenance period. The optimal maintenance period can balance preventive maintenance cost and fault shutdown cost in engineering, reduces the operation maintenance cost to the minimum, and ensures that the MMC obtains optimal economy in long-term operation, thereby providing certain reference for actual engineering operation.
The component failure rates are shown in table 1 and the MMC cost parameters are shown in table 2. The results of the example analyses according to tables 1 and 2 are shown in fig. 4 and 5.
TABLE 1 component failure Rate
| Device | Failure rate/(times/year) |
| IGBT module | 0.000876 |
| Capacitor with a capacitor element | 0.001752 |
| Control system | 0.001402 |
| Power supply drive | 0.035040 |
TABLE 2 MMC cost parameters
| Parameter(s) | Cost of |
| cw/k$ | 0.5 |
| cr/k$ | 27 |
| cp/k$ | 150 |
| cf/k$ | 8000 |
FIG. 4 shows the maintenance cost per unit time in an age replacement strategy as a function of maintenance period. It can be seen that when T is small, the required maintenance cost per unit time is extremely high, which is an unnecessary cost loss caused by frequent maintenance of the MMC. The maintenance cost per unit time gradually decreases along with the increase of the maintenance period T, the descending speed gradually slows down, the time maintenance cost is the lowest when the descending speed decreases to the minimum value 479.8k $ and the optimal period T which enables the average maintenance cost to be the lowest is 0.947 years. After the extreme point, the cost per unit time rapidly rises in a short time because the rate of the downtime at this stage rapidly rises with the increase of the maintenance period T, and the loss due to the downtime rapidly takes a dominant position. In view of the fact that the failure rate will rise during long-term operation, and to avoid a rapid rise in operating costs beyond the lowest cost point, the maintenance period chosen may be suitably less than optimal to preserve a certain margin.
The maintenance cost per unit time under the batch replacement strategy is as shown in fig. 5, and the maintenance cost per unit time is similar to the age replacement strategy in view of the curve trend. Before and after the optimal maintenance period, because the occurrence of shutdown faults is greatly avoided by timely regular preventive maintenance, the two maintenance strategies are not greatly different, and the maintenance cost is similar. When the maintenance period T is large, the batch replacement strategy reduces the probability of subsequent shutdown failures because of the preventive maintenance that must be performed at the kT time, so the average cost is lower for an older replacement strategy when T is large.
In this embodiment, when the MMC reliability model is established, a markov model of a repairable system is adopted. In the model, only when the redundant sub-modules are all put into operation and the sub-modules break down, the MMC fails and cannot work, the system is shut down to replace all the failed sub-modules, and the maintenance process starts. And after the maintenance process is finished, the MMC regards the new system as a new system to continue to operate.
In this example, the maintenance strategy was studied by adding the concept of regular preventive maintenance to the reliability model described above. And proper preventive maintenance is carried out before the system fails, so that partial fault shutdown accidents can be effectively avoided, and further, the long-term running loss is reduced. In the minimum cost model, the economic loss of the regular preventive shutdown maintenance and the economic loss caused by the fault shutdown are quantified, and the two kinds of shutdown losses can be balanced by selecting a proper regular maintenance period, so that the whole operation cost in unit time is reduced to the minimum.
Based on above-mentioned scheme, it brings two aspects beneficial effect:
(1) the reliability index of the MMC is more in line with the actual engineering.
(2) The problems of quantification of MMC maintenance cost and selection of maintenance period under a k/n redundant system are solved, and reference is provided for selection of the optimal maintenance period of the MMC, so that reliability of the MMC in a long-term operation process is improved.
Based on the same inventive concept, the present embodiment is directed to a computing device, which includes a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor executes the computer program to implement the steps of the method according to the above embodiment.
Based on the same inventive concept, the present embodiment aims to provide an operation control system of a multilevel converter, which is characterized by comprising: a controller configured to:
receiving the temperature and voltage of a capacitor in the operation process when the multi-level converter is in a stable working state, and the junction temperature fluctuation times, the junction temperature fluctuation average value, the maximum value and the amplitude value within unit time in the operation process of the IGBT;
acquiring a capacitance fault rate and an IGBT fault rate based on the acquired capacitance and IGBT operation data; calculating the fault rate of the sub-modules of the multilevel converter according to the fault rate of the capacitor and the fault rate of the IGBT;
determining an optimal maintenance period of the multi-level converter in a future period of time based on the fault rate of the sub-modules of the multi-level converter; and issuing a control command to control the working or shutdown running state of the multilevel converter based on the optimal maintenance period.
The control system can be used as a local processing terminal and comprises a processor or a controller or a server or an industrial control computer, the operation state data of the multi-level converter is obtained through communication between a communication line and a direct current system comprising the multi-level converter, the operation state data comprises the temperature and the voltage of the multi-level converter in the capacitor operation process when the multi-level converter is in a stable working state, the junction temperature fluctuation times, the junction temperature fluctuation average value, the maximum value and the amplitude value in unit time in the IGBT operation process, data processing is carried out after the data are obtained, an optimal maintenance period is obtained through calculation by combining a model of the multi-level converter, an operation or shutdown instruction is sent to the direct current system based on the optimal maintenance period, the operation state of the multi-level converter is controlled by the direct current system, or the calculation device is directly connected with the multi-level converter through a driving circuit, and the multi-level converter is controlled to start or stop operating according to the direct data output result and the optimal maintenance period .
The controller is connected with the display device, displays an optimal maintenance period with set time and carries out reminding notification, or is communicated with the mobile terminals, relevant information is sent to the mobile terminals of the users, and relevant personnel can make maintenance plans in time.
The acquired data can be directly acquired from the direct current system, or corresponding detection equipment and a detection processor are installed, the detection data acquired by the detection equipment are stored in the detection processor, and the detection processor outputs the data to the computing terminal.
The failure rate parameters of the components (including the failure rate parameters of the IGBT module, the capacitor, the control system, and the power driving system), the cost parameters of the MMC (including the sub-module maintenance cost, the sub-module replacement cost, the system loss due to the planned shutdown, and the system loss due to the planned shutdown), and the minimum cost model calculation formula need to be obtained.
The data processing process comprises the following steps: and (3) bringing the fault rate and the cost parameters into a minimum cost model, obtaining a maintenance period-unit time maintenance cost relation through a unit time operating cost calculation formula, determining a maintenance period corresponding to the minimum maintenance cost, and outputting the maintenance period as an optimal maintenance period. In the modeling process of the minimum cost model, the probability of the actual equipment fault in each time period is predicted by combining a probability theory method. In the definition of the minimum cost model, once equipment failure occurs, the operation is stopped immediately and maintenance is carried out, and on the basis, the optimal maintenance period discussed in the invention refers to planned shutdown when the equipment normally operates, so that the equipment is subjected to preventive maintenance to reduce the probability of subsequent equipment failure.
Based on the same inventive concept, it is an object of the present embodiments to provide a computer-readable storage medium.
A computer-readable storage medium, on which a computer program is stored which, when executed by a processor, performs the steps of the method of the above-described embodiment example.
The steps involved in the apparatus of the above embodiment correspond to the first embodiment of the method, and the detailed implementation manner can be referred to the relevant description part of the first embodiment. The term "computer-readable storage medium" should be taken to include a single medium or multiple media containing one or more sets of instructions; it should also be understood to include any medium that is capable of storing, encoding or carrying a set of instructions for execution by a processor and that cause the processor to perform any of the methods of the present disclosure.
Those skilled in the art will appreciate that the modules or steps of the present disclosure described above can be implemented using general purpose computing devices, or alternatively, they can be implemented using program code executable by computing devices, such that they are stored in a storage device and executed by the computing devices, or they are separately fabricated into individual integrated circuit modules, or multiple modules or steps of them are fabricated into a single integrated circuit module. The present disclosure is not limited to any specific combination of hardware and software.
The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure, and various modifications and changes may be made to the present disclosure by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present disclosure should be included in the protection scope of the present disclosure.
Although the present disclosure has been described with reference to specific embodiments, it should be understood that the scope of the present disclosure is not limited thereto, and those skilled in the art will appreciate that various modifications and changes can be made without departing from the spirit and scope of the present disclosure.
Claims (9)
1. An operation control method of a multilevel converter is characterized by comprising the following steps:
collecting the temperature and voltage of a capacitor in the operation process when the multi-level converter is in a stable working state, and the junction temperature fluctuation times, the junction temperature fluctuation average value, the maximum value and the amplitude value in unit time in the operation process of the IGBT;
acquiring a capacitance fault rate and an IGBT fault rate based on the acquired capacitance and IGBT operation data; calculating the fault rate of the sub-modules of the multilevel converter according to the fault rate of the capacitor and the fault rate of the IGBT;
determining an optimal maintenance period of the multi-level converter in a future period of time based on the fault rate of the sub-modules of the multi-level converter; the method comprises the following specific steps:
establishing a multi-level converter bridge arm state transition probability diagram aiming at the possibility of multi-level converter state transition; expressing a multi-level converter transfer rate matrix by utilizing the fault rate of the sub-module of the multi-level converter based on a state transfer probability diagram; obtaining steady-state and transient reliability indexes of the direct-current system based on the transfer rate matrix of the multilevel converter; obtaining an optimal maintenance period meeting the stable operation of the direct current system based on the steady-state and transient reliability indexes of the direct current system;
and issuing a control command to control the working or shutdown running state of the multilevel converter based on the optimal maintenance period.
2. The method as claimed in claim 1, wherein the failure rate of the sub-module of the multilevel converter is the sum of the failure rates of the upper and lower IGBTs and the failure rate of the capacitor in the sub-module.
3. The method according to claim 1, wherein the data is collected when the multilevel converter is in a stable operating state, and then data preprocessing is performed first, so that repeated data is deleted, and missing data is supplemented.
4. The method as claimed in claim 3, wherein the preprocessed data are stored according to the time tag for evaluating the operation state of the multilevel converter in a time period, and the operation state data of the multilevel converter in the time period are collected again in the next operation time period to evaluate the operation state of the multilevel converter in the time period.
5. An operation control system of a multilevel converter, comprising: a controller configured to:
receiving the temperature and voltage of a capacitor in the operation process when the multi-level converter is in a stable working state, and the junction temperature fluctuation times, the junction temperature fluctuation average value, the maximum value and the amplitude value within unit time in the operation process of the IGBT;
acquiring a capacitance fault rate and an IGBT fault rate based on the acquired capacitance and IGBT operation data; calculating the fault rate of the sub-modules of the multilevel converter according to the fault rate of the capacitor and the fault rate of the IGBT;
determining an optimal maintenance period of the multi-level converter in a future period of time based on the fault rate of the sub-modules of the multi-level converter; the method comprises the following specific steps:
establishing a multi-level converter bridge arm state transition probability diagram aiming at the possibility of multi-level converter state transition; expressing a multi-level converter transfer rate matrix by utilizing the fault rate of the sub-module of the multi-level converter based on a state transfer probability diagram; obtaining steady-state and transient reliability indexes of the direct-current system based on the transfer rate matrix of the multilevel converter; obtaining an optimal maintenance period meeting the stable operation of the direct current system based on the steady-state and transient reliability indexes of the direct current system;
and issuing a control command to control the working or shutdown running state of the multilevel converter based on the optimal maintenance period.
6. The operation control system of a multilevel converter according to claim 5, wherein the controller obtains the operation state data of the multilevel converter through communication with a direct current system including the multilevel converter through a communication line.
7. The operation control system of a multilevel converter according to claim 5, wherein the controller is directly connected to the multilevel converter through the driving circuit and configured to control an operation state of the multilevel converter.
8. A computing device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements the steps of the method of any of claims 1 to 4 when executing the program.
9. A computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, is adapted to carry out the steps of the method according to any one of the preceding claims 1-4.
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