CN114301321B - Reconfigurable fault-tolerant control method for hysteresis SVPWM of single-phase voltage source multi-level inverter - Google Patents
Reconfigurable fault-tolerant control method for hysteresis SVPWM of single-phase voltage source multi-level inverter Download PDFInfo
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Abstract
The invention provides a reconfigurable fault-tolerant control method for hysteresis SVPWM of a single-phase voltage source multi-level inverter, and relates to the technical field of power transmission and distribution. Firstly, constructing a single-phase multi-level voltage source inverter, and controlling the tracking error of the inverter within a hysteresis range; when the voltage vector selected by the current tracking control algorithm in the non-fault state before the fault occurs is a non-fault vector, the voltage vector is the final output vector of the inverter; when the selected voltage vector is a fault vector, carrying out voltage vector substitution; according to the current tracking error, redundant voltage vectors with coincident positions are preferentially selected for equivalent substitution; if the redundant voltage vectors with the positions overlapping are not available, other non-fault vectors with the positions closest to the action effect are selected, and the rise and fall of the actual output current of the inverter are controlled, so that the reference current is tracked, and fault-tolerant control is realized. The method can ensure that the inverter continues to work stably under the condition of single-tube and most double-tube open-circuit faults of the inverter.
Description
Technical Field
The invention relates to the technical field of power transmission and distribution, in particular to a hysteresis SVPWM reconfigurable fault-tolerant control method of a single-phase voltage source multi-level inverter.
Background
The current tracking type multi-level inverter is widely applied to occasions such as active filtering and reactive compensation of a photovoltaic grid-connected system, a medium-high voltage power system and the like; along with the development of solar cells and other technologies and the reduction of cost, the multi-level inversion structure adopting a plurality of independent direct current power supplies has the characteristic of strong economy; the increase of the level number is beneficial to improving the output voltage level of the inverter, and accords with the current popular design concept of 'silicon copper advance and retreat'.
However, since the number of power switching devices in a multilevel inverter is relatively large, the probability of failure is also much greater. Once a fault occurs, if fault tolerant control is not taken, a significant impact will be placed on the grid and load.
Fault-tolerant control methods of the multilevel inverter can be classified into a hardware method and a software method 2. The hardware method generally needs to add a standby unit or other auxiliary modules in the multilevel inverter topology structure, and fault-tolerant control is realized on the basis of the standby unit or other auxiliary modules. The document Reconfigurable multilevel inverter with fault-tolerant availability adds an additional module on the load side of the cascading inverter, and the structure can flexibly carry out structural reorganization according to different fault modes to realize fault tolerance.
The software method does not need to change the topological structure of the multilevel inverter, but realizes fault-tolerant control through a control algorithm; hardware cost can be saved, and system structure is simplified. Mainly comprises the following 3 kinds:
first, the fault unit is shielded and the capacity is reduced. The method is more suitable for cascading inverters. In order to ensure the symmetry of the three-phase output voltage, besides the shorted faulty cells, non-faulty cells corresponding to the faulty cells in the other two phases are also usually shielded. Therefore, part of non-fault units cannot be fully utilized, and the waste of hardware resources exists. The document A new fault-tolerant strategy based on a modified selective harmonic technique for three-phase multilevel converters with a single faulty cell takes a seven-level cascading inverter as an example, and proves that in the fault-tolerant method, the voltage amplitude of an output line of the inverter is 5.19V before fault dc Down to 3.46V after failure dc Wherein V is dc Is the direct current side voltage of the cascade unit.
Secondly, a neutral point offset method, which is essentially to inject a basic zero sequence voltage, can obtain the maximum symmetrical line voltage under the condition of bypassing only the fault unit; but the neutral point shift method tends to cause low-order voltage harmonics to rise. The document Control Method for Cascaded H-Bridge Inverter With Faulty Cells Based on Differential PWM proposes a differential-compensation modulation mode which, while achieving fault-tolerant operation, can also reduce voltage harmonics caused by neutral point shifts. However, when the load power factor is low, the injected zero sequence voltage may cause actual power to flow back, resulting in a rise in the dc side voltage, even out of the set range.
Thirdly, the DC side voltage value of the inverter is adjusted. The literature "Fault-Tolerant Design and Control Strategy for Cascaded H-Bridge Multilevel Converter-Based STATCOM" makes the maximum value of the phase output voltage the same as before the Fault by raising the dc side voltage of the cascade unit in the Fault phase; the literature A new fault-tolerant strategy for a cascaded H-bridge based STATCOM increases the voltage of the DC side of the fault phase of the inverter to 2N/(2N-1) times, adopts an improved SHEPWM method, realizes fault-tolerant operation, and simultaneously can selectively eliminate low-voltage harmonic waves. However, the fault-tolerant method is only suitable for occasions with controllable direct-current voltage; but also causes an increase in power electronics voltage stress. Therefore, the documents "Fault-tolerant operation of a battery-energy-storage system based on a multilevel cascade PWM converter with star configuration" and "A Fault-tolerant strategy based on fundamental phase-shift compensation for three-phase multilevel converters with quasi-Z-source networks with discontinuous input current" propose Fault-tolerant control methods combining neutral point offset and DC side voltage regulation, which can reduce voltage stress borne by power electronic devices in Fault state. In the method, the rise of the voltage at the direct current side of the inverter can cause the change of the spatial position of the voltage vector, so that the selection algorithm of the voltage vector becomes more complex.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a hysteresis SVPWM reconfigurable fault-tolerant control method for a single-phase voltage source multi-level inverter, which realizes fault-tolerant control for the single-phase voltage source multi-level inverter.
In order to solve the technical problems, the invention adopts the following technical scheme: the reconfigurable fault-tolerant control method for the hysteresis SVPWM of the single-phase voltage source multi-level inverter comprises the following steps:
step 1, constructing a single-phase multi-level voltage source inverter;
the single-phase multi-level voltage source inverter consists of 2 independent direct current power supplies and 9 groups of power switching devices T 1 -T 9 Composition; wherein 3 groups of switching devices T 5 、T 8 And T 9 A single-phase bridge type uncontrollable rectifying module is adopted, and an IGBT is arranged on the direct current side of the rectifying bridge; the inverter switching states and voltage space vectors are shown in Table 1, where u AB The phase voltage is output by the inverter, and E is the direct-current power supply voltage; the inverter has 17 switch states and voltage space vectors, and outputs 7 levels of 3E, 2E, E, 0, -E, -2E and 3E;
table 1 inverter switching states and voltage vectors
Step 2, controlling the tracking error of the inverter in a hysteresis range;
first, determining inverter current tracking error Δi=i by hysteresis comparison * -i, wherein i * I is the actual current; then reducing tracking error to be within hysteresis range by reasonably selecting inverter voltage vector; the third-order hysteresis width is h, 2h and 3h respectively; the voltage vector selection method under the non-fault state is shown in table 2; in the fault state, the voltage vector selected by the current tracking control algorithm in the non-fault state is required to be equivalently replaced, namely fault-tolerant control is performed;
respectively selecting voltage space vectors V under non-fault state 1 、V 4 、V 5 、V 6 、V 13 、V 14 And V 15 To produce 3E, 2E,E. 0, -E, -2E, -3E 7 levels; i.e. each level only retains 1 inverter switching state; at this time, the switching device T 6 And T 7 Only participate in the work when fault-tolerant control;
TABLE 2 hysteresis control method in non-failure state
| Tracking error | Voltage vector | u AB |
| △i＞3h | V 15 ～V 17 | 3E |
| 2h＜△i≤3h | V 14 | 2E |
| h＜△i≤2h | V 13 | E |
| -h≤△i≤h | V 6 ～V 12 | 0 |
| -2h≤△i＜-h | V 5 | -E |
| -3h≤△i＜-2h | V 4 | -2E |
| △i＜-3h | V 1 ～V 3 | -3E |
When an open circuit fault occurs in one or more IGBTs in the inverter, some voltage vectors are affected by the fault and become fault vectors, as shown in table 3, wherein "v" indicates that the fault has no effect on the voltage vectors; "x" indicates that there is an effect that the voltage vector becomes a fault vector;
table 3 influence of single tube open circuit fault on inverter
| Vector quantity | T 1 | T 2 | T 3 | T 4 | T 5 | T 6 | T 7 | T 8 | T 9 | u AB |
| V 1 | √ | × | × | √ | √ | √ | √ | √ | √ | -3E |
| V 2 | √ | √ | × | √ | √ | × | √ | √ | × | -3E |
| V 3 | √ | × | √ | √ | √ | √ | × | × | √ | -3E |
| V 4 | √ | × | √ | √ | × | √ | √ | × | √ | -2E |
| V 5 | √ | √ | × | √ | × | √ | √ | √ | × | -E |
| V 6 | × | × | √ | √ | √ | √ | √ | √ | √ | 0 |
| V 7 | √ | √ | × | × | √ | √ | √ | √ | √ | 0 |
| V 8 | × | √ | √ | √ | √ | × | √ | √ | × | 0 |
| V 9 | √ | √ | × | √ | √ | √ | × | √ | × | 0 |
| V 10 | √ | × | √ | √ | √ | × | √ | × | √ | 0 |
| V 11 | √ | √ | √ | × | √ | √ | × | × | √ | 0 |
| V 12 | √ | √ | √ | √ | √ | √ | √ | × | × | 0 |
| V 13 | √ | √ | √ | × | × | √ | √ | × | √ | E |
| V 14 | × | √ | √ | √ | × | √ | √ | √ | × | 2E |
| V 15 | × | √ | √ | × | √ | √ | √ | √ | √ | 3E |
| V 16 | × | √ | √ | √ | √ | √ | × | √ | × | 3E |
| V 17 | √ | √ | √ | × | √ | × | √ | × | √ | 3E |
Step 3, when the voltage vector selected by the current tracking control algorithm in the non-fault state before the fault occurs is a non-fault vector, the voltage vector is the final output vector of the inverter; when the selected voltage vector is a fault vector, voltage vector substitution is needed;
(1) Replacing a voltage vector of the inverter under single-tube open-circuit fault;
among the voltage vectors selected by the current tracking control algorithm under the non-fault state, the voltage vector which is not affected by the fault is continuously used without replacement; if the voltage vector affected by the fault has the same voltage vector as the voltage vector with the same level value, the voltage vector with the same level value is used for equivalent substitution to substitute the output level of the front inverter and the back inverterThe same; if no voltage vector with the same level value can be selected, selecting a vector with the same level direction and the size smaller than the set threshold value for substitution; namely, when h < [ delta ] i is less than or equal to 2h and 2h < [ delta ] i is less than or equal to 3h, the vector V is selected 13 The method comprises the steps of carrying out a first treatment on the surface of the Or when 2h < [ delta ] i is less than or equal to 3h and delta ] i is more than 3h, the vector V is selected 17 ；
(2) The voltage vector of the inverter under the double-tube open circuit fault is replaced;
when the inverter has double-tube open-circuit fault, at least 1 positive level, zero level and negative level can be output, and fault-tolerant control is performed through voltage vector substitution; when the double-tube open circuit fault occurs to the inverter, if the output end lacks positive level or lacks negative level, fault-tolerant control cannot be realized through inverter topology structure reconstruction and voltage vector substitution, and then step 4 is executed;
step 4, performing hysteresis SVPWM reconfigurable fault-tolerant control; reasonably selecting an effective voltage vector according to the current tracking error, and preferentially selecting a redundant voltage vector with coincident positions for equivalent substitution; if the redundant voltage vectors with the positions overlapping are not available, other non-fault vectors with the positions closest to the action effect are selected, and the rise and fall of the actual output current of the inverter are controlled, so that the reference current is tracked, and fault-tolerant control is realized.
When the voltage vector selected by the current tracking control algorithm in the non-fault state before the fault occurs is a non-fault vector, the voltage vector is the final output vector of the inverter; when the selected voltage vector is a fault vector, voltage vector substitution is needed; the voltage vector substitution methods under single-tube open circuit and double-tube open circuit faults of the inverter are shown in tables 4-5;
table 4 inverter voltage vector substitution table under single tube open circuit fault
Table 5 inverter voltage vector substitution table under double-barrelled open circuit fault
Wherein, the single-tube open-circuit faults comprise 9 kinds, and the double-tube open-circuit faults comprise 36 kinds; "v" indicates that the fault has no effect on the voltage vector and no substitution is required; in table 5, the case of writing "none" is "when the inverter has a double-pipe open circuit fault, if the output terminal lacks a positive level or lacks a negative level, fault-tolerant control cannot be achieved through inverter topology reconstruction and voltage vector substitution.
The beneficial effects of adopting above-mentioned technical scheme to produce lie in: the invention provides a single-phase voltage source multi-level inverter hysteresis SVPWM reconfigurable fault-tolerant control method, which combines the advantages of hardware and software fault-tolerant control methods, and realizes fault-tolerant control by utilizing a topological structure reconstruction and redundant voltage vector equivalent substitution method when single-tube and double-tube power faults occur. The method preferably selects redundant voltage vectors with coincident positions for equivalent substitution, and if no coincident vector exists, selects other vectors with closest positions and action effects, thereby realizing fault-tolerant control. The method can ensure that the inverter continues to work stably under the condition of single-tube and most double-tube open-circuit faults of the inverter, and can track the reference current value more accurately. The fault tolerance method does not need the switching operation of the main and standby switching device units of the inverter, can omit the additional switching devices required in the switching process, and has the advantages of simple operation and high stability.
Drawings
Fig. 1 is a structural topology diagram of a main circuit of a single-phase multi-level voltage source inverter according to an embodiment of the present invention;
FIG. 2 shows that the switches provided in the embodiment of the invention are all normal and T 1 Schematic of the impact on voltage vector at open circuit failure, where (a) is normal for each switch and (b) is T 1 An open circuit fault;
FIG. 3 is a block diagram of an inverter hysteresis current tracking control method according to an embodiment of the present invention;
FIG. 4 shows a T-cell according to an embodiment of the present invention 2 And T 3 Schematic of the effect of open circuit failure on voltage vector, where (a) is T 2 An open circuit failure, (b) is T 3 An open circuit fault;
FIG. 5 shows a T-cell according to an embodiment of the present invention 4 And T 5 Schematic of the effect of open circuit failure on voltage vector, where (a) is T 4 An open circuit failure, (b) is T 5 An open circuit fault;
FIG. 6 shows a T-cell according to an embodiment of the present invention 6 And T 7 Schematic of the effect of open circuit failure on voltage vector, where (a) is T 6 An open circuit failure, (b) is T 7 An open circuit fault;
FIG. 7 shows a T-cell according to an embodiment of the present invention 8 And T 9 Schematic of the effect of open circuit failure on voltage vector, where (a) is T 8 An open circuit failure, (b) is T 9 An open circuit fault;
FIG. 8 shows a T-cell according to an embodiment of the present invention 1 And T 2 、T 1 And T 7 Schematic of the impact on voltage vector at failure, where (a) is T 1 And T 2 Open circuit simultaneous failure, (b) is T 1 And T 7 Open circuit while failure;
FIG. 9 shows a T-shape according to an embodiment of the present invention 4 And T 5 、T 4 And T 8 Schematic of the impact on voltage vector at failure, where (a) is T 4 And T 5 Open circuit simultaneous failure, (b) is T 4 And T 8 Open circuit while failure;
FIG. 10 is a voltage and current waveform diagram of a switching tube according to an embodiment of the present invention when the switching tube is normal;
FIG. 11 is a plot of the current THD at normal times provided by an embodiment of the invention;
FIG. 12 shows a T-shape according to an embodiment of the present invention 1 Voltage and current waveform diagrams during faults;
FIG. 13 shows a T-shape according to an embodiment of the present invention 1 Current THD plot at fault;
FIG. 14 shows an embodiment of the present inventionT of (2) 1 Voltage and current waveform diagrams after fault tolerance;
FIG. 15 shows a T-shape according to an embodiment of the present invention 1 A fault-tolerant current THD graph;
FIG. 16 shows a T-shape according to an embodiment of the present invention 5 Voltage and current waveform diagrams after fault tolerance;
FIG. 17 shows a T-shaped structure according to an embodiment of the present invention 5 A fault-tolerant current THD graph;
FIG. 18 shows a T-shape according to an embodiment of the present invention 1 And T 2 Meanwhile, the voltage and current waveform diagrams after fault tolerance are carried out;
FIG. 19 is a diagram of a T-cell according to an embodiment of the present invention 1 And T 2 Meanwhile, the voltage and current waveform diagrams after fault tolerance are carried out;
FIG. 20 shows a T-shaped structure according to an embodiment of the present invention 1 And T 2 Meanwhile, a current THD graph after fault tolerance is carried out;
FIG. 21 shows a T-shaped structure according to an embodiment of the present invention 4 And T 5 Meanwhile, the voltage and current waveform diagrams after fault tolerance are carried out;
FIG. 22 shows a T-shape according to an embodiment of the present invention 4 And T 5 And meanwhile, a current THD graph after fault tolerance is achieved.
Detailed Description
The following describes in further detail the embodiments of the present invention with reference to the drawings and examples. The following examples are illustrative of the invention and are not intended to limit the scope of the invention.
In this embodiment, the reconfigurable fault-tolerant control method for the hysteresis SVPWM of the single-phase voltage source multi-level inverter includes the following steps:
step 1, constructing a single-phase multi-level voltage source inverter;
in this embodiment, as shown in FIG. 1, the single-phase multi-level voltage source inverter consists of 2 independent DC power sources and 9 groups of power switching devices T 1 -T 9 Composition is prepared. Wherein 3 groups of switching devices T 5 、T 8 And T 9 A common single-phase bridge type uncontrollable rectifying module is adopted, and an IGBT is arranged on the direct current side of the rectifying bridge; inverter switching stateThe voltage space vector is shown in Table 1, where u AB The phase voltage is output by the inverter, and E is the direct-current power supply voltage; the space position of the voltage vector is shown in fig. 2 (a), the inverter has 17 switch states and voltage space vectors, and outputs 7 levels of 3E, 2E, E, 0, -E, -2E and 3E; in the fault state, redundant voltage vectors can be generated through topology structure reconstruction, and a foundation is laid for a fault-tolerant control algorithm.
Table 1 inverter switching states and voltage vectors
Step 2, controlling the tracking error of the inverter in a hysteresis range;
in this embodiment, as shown in fig. 3, the inverter hysteresis current tracking control is performed by first determining an inverter current tracking error Δi=i by using hysteresis comparison * -i, wherein i * I is the actual current; then reducing tracking error to be within hysteresis range by reasonably selecting inverter voltage vector; the third-order hysteresis width is h, 2h and 3h respectively; the voltage vector selection method under the non-fault state is shown in table 2; in the fault state, the voltage vector selected by the current tracking control algorithm in the non-fault state is required to be equivalently replaced, namely fault-tolerant control is performed;
to simplify the algorithm, the voltage space vectors V are selected under the non-fault state 1 、V 4 、V 5 、V 6 、V 13 、V 14 And V 15 To produce 3E, 2E, E, 0, -E, -2E, -3E 7 levels; i.e. each level only retains 1 inverter switching state; at this time, the switching device T 6 And T 7 Only participate in the work when fault-tolerant control;
TABLE 2 hysteresis control method in non-failure state
When one or more IGBTs in the inverter have open-circuit faults, some voltage vectors are affected by the faults and become fault vectors; as shown in table 3, where "v" indicates that the fault has no effect on the voltage vector; "x" indicates that there is an effect that the voltage vector becomes a fault vector;
as can be seen from Table 3, when T 1 ～T 9 When an open circuit fault occurs in any 1 of the inverters, the inverters can output at least 1 positive level, zero level and negative level; that is, the load current can be controlled to rise and fall in theory, but the number of alternative voltage vectors and output levels is reduced;
fig. 2 (b) and fig. 4 to 7 show the spatial distribution diagrams of the voltage vectors of the inverter under the single-tube open-circuit fault. FIGS. 8 and 9 at T 1 And T 2 、T 1 And T 7 、T 4 And T 5 、T 4 And T 8 The double-pipe open circuit fault analysis is carried out by taking faults as examples. Wherein, the broken line represents a fault vector, and voltage vector substitution is needed; the solid line represents a non-faulty vector and no voltage vector substitution is required.
Table 3 influence of single tube open circuit fault on inverter
| Vector quantity | T 1 | T 2 | T 3 | T 4 | T 5 | T 6 | T 7 | T 8 | T 9 | u AB |
| V 1 | √ | × | × | √ | √ | √ | √ | √ | √ | -3E |
| V 2 | √ | √ | × | √ | √ | × | √ | √ | × | -3E |
| V 3 | √ | × | √ | √ | √ | √ | × | × | √ | -3E |
| V 4 | √ | × | √ | √ | × | √ | √ | × | √ | -2E |
| V 5 | √ | √ | × | √ | × | √ | √ | √ | × | -E |
| V 6 | × | × | √ | √ | √ | √ | √ | √ | √ | 0 |
| V 7 | √ | √ | × | × | √ | √ | √ | √ | √ | 0 |
| V 8 | × | √ | √ | √ | √ | × | √ | √ | × | 0 |
| V 9 | √ | √ | × | √ | √ | √ | × | √ | × | 0 |
| V 10 | √ | × | √ | √ | √ | × | √ | × | √ | 0 |
| V 11 | √ | √ | √ | × | √ | √ | × | × | √ | 0 |
| V 12 | √ | √ | √ | √ | √ | √ | √ | × | × | 0 |
| V 13 | √ | √ | √ | × | × | √ | √ | × | √ | E |
| V 14 | × | √ | √ | √ | × | √ | √ | √ | × | 2E |
| V 15 | × | √ | √ | × | √ | √ | √ | √ | √ | 3E |
| V 16 | × | √ | √ | √ | √ | √ | × | √ | × | 3E |
| V 17 | √ | √ | √ | × | √ | × | √ | × | √ | 3E |
Step 3, when the voltage vector selected by the current tracking control algorithm in the non-fault state before the fault occurs is a non-fault vector, the voltage vector is the final output vector of the inverter; when the selected voltage vector is a fault vector, voltage vector substitution is needed;
(1) Replacing a voltage vector of the inverter under single-tube open-circuit fault;
among the voltage vectors selected by the current tracking control algorithm under the non-fault state, the voltage vector which is not affected by the fault is continuously used without replacement; if the voltage vector affected by the fault has the voltage vector with the same level value, the voltage vector with the same level value is used for equivalent substitution, and the output levels of the inverters are the same before and after substitution; if no voltage vector with the same level value can be selected, selecting a vector with the same level direction and the size smaller than the set threshold value for substitution; namely, when h < [ delta ] i is less than or equal to 2h and 2h < [ delta ] i is less than or equal to 3h, the vector V is selected 13 The method comprises the steps of carrying out a first treatment on the surface of the Or when 2h < [ delta ] i is less than or equal to 3h and delta ] i is more than 3h, the vector V is selected 17 。
(2) The voltage vector of the inverter under the double-tube open circuit fault is replaced;
when the inverter has double-tube open-circuit fault, at least 1 positive level, zero level and negative level can be output, and fault-tolerant control is performed through voltage vector substitution; when the double-tube open circuit fault occurs to the inverter, if the output end lacks positive level or lacks negative level, fault-tolerant control cannot be realized through inverter topology structure reconstruction and voltage vector substitution, and then step 4 is executed;
step 4, performing hysteresis SVPWM reconfigurable fault-tolerant control; reasonably selecting an effective voltage vector according to the current tracking error, and preferentially selecting a redundant voltage vector with coincident positions for equivalent substitution; if the non-fault vectors are not overlapped, other non-fault vectors with the closest positions and action effects are selected, and the rise and fall of the actual output current of the inverter are controlled, so that the reference current is tracked, and fault-tolerant control is realized.
As shown in fig. 2 (a) and table 3, when the voltage vector selected by the current tracking control algorithm in the non-fault state before the fault occurs is a non-fault vector, the voltage vector is the final output vector of the inverter; when the selected voltage vector is a fault vector, then a voltage vector substitution is required. Tables 4-5 present voltage vector substitution methods for single-tube and double-tube open faults of the inverter; wherein, the single-tube open-circuit faults comprise 9 kinds, and the double-tube open-circuit faults comprise 36 kinds; "" indicates that the fault has no effect on the voltage vector and no substitution is required. In the table, the condition of no writing is that when the inverter has double-tube open circuit fault, if the output end lacks positive level or lacks negative level, fault-tolerant control cannot be realized through inverter topology structure reconstruction and voltage vector substitution.
Table 4 inverter voltage vector substitution table under single tube open circuit fault
Table 5 inverter voltage vector substitution table under double-barrelled open circuit fault
The embodiment uses T 1 For example, the single-tube open-circuit fault is that the inverter can only output 3E, E, 0, -E, -2E and-3E 6 levels in the fault-tolerant running state, and the output level number is changed from 7 types to 6 types in the normal state. V selected by current tracking control algorithm under non-fault state 1 、V 4 、V 5 、V 6 、V 13 、V 14 And V 15 Of the 7 voltage vectors, V 1 、V 4 、V 5 And V 13 The device is not affected by the fault, can be used continuously, and does not need to be replaced; v (V) 6 、V 14 And V 15 Can be affected by the fault and needs to be replaced; wherein V is 6 And V 15 Respectively can adopt voltage vector V 7 And V 17 Equivalent substitution is carried out, and the output levels of the inverters are the same before and after substitution; and V is 14 Then there is noThe voltage vectors with identical level values can be selected, and in order to simplify the algorithm, the vectors V with identical level directions and similar magnitudes are selected 13 Or V 17 Replacement; namely, when h < [ delta ] i is less than or equal to 2h and 2h < [ delta ] i is less than or equal to 3h, the vector V is selected 13 The method comprises the steps of carrying out a first treatment on the surface of the Or when 2h < [ delta ] i is less than or equal to 3h and delta ] i is more than 3h, the vector V is selected 17 。
When the inverter has double-tube open circuit faults, the 9 groups of IGBTs can be in a 36-type double-tube fault arrangement and combination form. According to analysis, under 30 double-tube fault conditions, the inverter can output at least 1 positive level, zero level and negative level, and fault tolerance control can be performed through voltage vector substitution. In addition, when T 1 And T 4 、T 1 And T 8 、T 4 And T 9 When faults occur at the same time, the output end of the inverter lacks positive level; when T is 2 And T 3 、T 2 And T 9 、T 3 And T 8 And when a fault occurs, the negative level is absent. The fault-tolerant control cannot be realized in all the 6 conditions through inverter topology reconstruction and voltage vector substitution.
Therefore, the effective voltage vector can be reasonably selected according to the current tracking error on the basis of the tables 4 and 5, and the rise and fall of the actual output current of the inverter are controlled, so that the reference current is tracked, and fault-tolerant control is realized.
In order to verify the correctness and the effectiveness of the method, a system experiment platform is built for verification and analysis; the system parameters are as follows: the 2 power supply voltages at the DC side of the inverter are 24V and 12V respectively; the inductance of the output end is 5mH, the resistance is 5 omega, the reference current is sine wave with the amplitude of 4A, and the hysteresis width h of each step is 0.1A. The IGBT model of the inverter power switch device is BSM50GB120DN2; the power diode adopts a single-phase rectifier bridge MDQ60-1600V; the driving circuit adopts a falling wood source integrated IGBT driving module DA962D6; the system main control chip adopts a 32-bit DSP TMS320F28335; inverter dead time setting 4.27 μs; in the experiment, the model of the oscilloscope is DS1052E, and the electric energy quality analyzer is HIOKI PW3198;
fig. 10 is a waveform diagram of the inverter output voltage and current in a non-fault state, and fig. 11 is a corresponding current THD diagram. As can be seen from fig. 10 and 11, when all the switching devices are normal, the voltage waveform and the current waveform outputted by the inverter are changed according to a sine rule; the output voltage is 7 levels, the output current can accurately track the reference value, and the current harmonic distortion rate is 1.48%.
The embodiment also analyzes single-tube open-circuit faults and double-tube open-circuit faults respectively; wherein, single tube open circuit fault analysis is as follows:
respectively T in the inverter 1 ～T 9 And the IGBTs are disconnected one by one to generate a state when each IGBT has an open circuit fault. Because of more fault conditions, the embodiment uses only T 1 Single tube failure is for example as shown in fig. 12 and 13. The corresponding fault tolerance method waveforms at single tube failure are shown in fig. 14 and 15.
As can be seen in FIGS. 12-13, when T 1 When an open circuit fault occurs, the inverter output level will lack 3E, 2E and 0 levels; while the 3 levels-E, -2E, and-3E in the negative half-axis are unaffected. Thus, the output current waveform appears irregular in the positive half-shaft portion, while the negative half-shaft waveform portion is not substantially affected; at this time, the current distortion rate is as high as 52.5%.
From T in FIGS. 14-15 1 The fault-tolerant operation waveform shows that after the redundant voltage vector is replaced, the output level of the inverter is raised to six levels, the output current waveform is recovered to be normal, the sine degree is good, and the current harmonic distortion rate in the fault-tolerant operation state is 1.53% and is slightly higher than that in the non-fault state.
T is obtainable by the same way 5 In the case of fault tolerance, as shown in fig. 16 to 17, the harmonic distortion of the output current at this time is 1.72%. Other single tube open faults will not be repeated here.
According to the analysis, under the single-tube open-circuit fault state, the fault-tolerant control method based on voltage vector substitution is utilized, so that the accurate tracking of the reference current of the output current of the inverter can be ensured, and the total distortion rate of the current harmonic wave is slightly improved compared with that before the fault. This is due to the rise in current tracking error caused by inverter output level errors during the voltage vector substitution.
The double-tube open circuit fault analysis is as follows:
the double-pipe fault state of the embodiment is only T 1 And T 2 For example, when a fault occurs at the same time, the fault waveform is shown in fig. 18. When T is 1 And T 2 When faults occur simultaneously, the output level number of the inverter is reduced from 7 types before the faults to 2 types; because of the loss of most output levels, the inverter cannot track the reference current normally, and the output voltage and current also have obvious irregular changes.
The inverter output voltage, current and distortion rate after fault-tolerant control of the double-pipe fault are shown in fig. 19-20. The graph shows that after fault-tolerant control, the output current of the inverter is basically recovered to be normal, the sine degree is good, and the current harmonic distortion rate is 1.59%. T is obtainable by the same way 4 And T 5 As shown in fig. 21-22, the output current has better sine degree and the harmonic distortion rate of the current is 1.63%.
According to the analysis, in the double-tube open-circuit fault state, the fault-tolerant control method can ensure that the output current of the inverter tracks the reference current accurately, and the current harmonic distortion rate is slightly improved compared with that before the fault.
In summary, when the inverter has a single-tube open circuit or double-tube open circuit fault, the fault-tolerant control method can ensure that the inverter tracks the reference current more accurately, i.e. ensure that the system continues to operate stably.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced with equivalents; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions, which are defined by the scope of the appended claims.
Claims (4)
1. A reconfigurable fault-tolerant control method for hysteresis SVPWM of a single-phase voltage source multi-level inverter is characterized by comprising the following steps of: the method comprises the following steps:
step 1, constructing a single-phase multi-level voltage source inverter;
the single-phase multi-level voltage source inverter consists of 2 independent direct current power supplies and 9 groups of power switching devices T 1 -T 9 Composition; wherein 3 groups of switching devices T 5 、T 8 And T 9 A common single-phase bridge type uncontrollable rectifying module is adopted, and an IGBT is arranged on the direct current side of the rectifying bridge; the switching states and the voltage space vectors of the inverter are shown in table 1, the inverter has 17 switching states and voltage space vectors, and 7 levels of 3E, 2E, E, 0, -E, -2E and 3E are output;
table 1 inverter switching states and voltage vectors
Wherein u is AB The phase voltage is output by the inverter, and E is the direct-current power supply voltage;
step 2, controlling the tracking error of the inverter constructed in the step 1 in a hysteresis range;
step 3, when the voltage vector selected by the current tracking control algorithm in the non-fault state before the fault occurs is a non-fault vector, the voltage vector is the final output vector of the inverter; when the selected voltage vector is a fault vector, voltage vector substitution is needed;
step 4, performing hysteresis SVPWM reconfigurable fault-tolerant control; reasonably selecting an effective voltage vector according to the current tracking error, and preferentially selecting a redundant voltage vector with coincident positions for equivalent substitution; if the redundant voltage vectors with the positions overlapping are not available, other non-fault vectors with the positions closest to the action effect are selected, and the rise and fall of the actual output current of the inverter are controlled, so that the reference current is tracked, and fault-tolerant control is realized.
2. The reconfigurable fault-tolerant control method of the hysteresis SVPWM of the single-phase voltage source multi-level inverter according to claim 1, wherein the method comprises the following steps: the specific method for selecting the inverter voltage vector to reduce the tracking error to be within the hysteresis range in the step 2 is as follows:
first, determining inverter current tracking error Δi=i by hysteresis comparison * -i, wherein i * I is the actual current; then reducing tracking error to be within hysteresis range by selecting inverter voltage vector;
setting the width of the third-order hysteresis loop to be h, 2h and 3h respectively; the voltage vector selection method under the non-fault state is shown in table 2; under the fault state, the voltage vector selected by the current tracking control algorithm under the non-fault state is equivalently replaced, namely fault-tolerant control is carried out;
respectively selecting voltage space vectors V under non-fault state 1 、V 4 、V 5 、V 6 、V 13 、V 14 And V 15 To produce 3E, 2E, E, 0, -E, -2E, -3E 7 levels; i.e. each level only retains 1 inverter switching state; at this time, the switching device T 6 And T 7 Only participate in the work when fault-tolerant control;
TABLE 2 hysteresis control method in non-failure state
When one or more IGBTs in the inverter have an open circuit fault, some voltage vectors are affected by the fault and become fault vectors, as shown in table 3;
table 3 influence of single tube open circuit fault on inverter
Wherein "∈" indicates that the fault has no effect on the voltage vector; "x" indicates that there is an effect that the voltage vector becomes a fault vector.
3. The reconfigurable fault-tolerant control method of the hysteresis SVPWM of the single-phase voltage source multi-level inverter according to claim 2, wherein the method comprises the following steps: in step 3, when the selected voltage vector is a fault vector, the specific method for replacing the voltage vector is as follows:
(1) Replacing a voltage vector of the inverter under single-tube open-circuit fault;
among the voltage vectors selected by the current tracking control algorithm under the non-fault state, the voltage vector which is not affected by the fault is continuously used without replacement; if the voltage vector affected by the fault has the voltage vector with the same level value, the voltage vector with the same level value is used for equivalent substitution, and the output levels of the inverters are the same before and after substitution; if no voltage vector with the same level value can be selected, selecting a vector with the same level direction and the size smaller than the set threshold value for substitution;
(2) The voltage vector of the inverter under the double-tube open circuit fault is replaced;
when the inverter has double-tube open-circuit fault, at least 1 positive level, zero level and negative level can be output, and fault-tolerant control is performed through voltage vector substitution; when the double-tube open circuit fault occurs to the inverter, if the output end lacks a positive level or lacks a negative level, fault-tolerant control cannot be realized through inverter topology reconstruction and voltage vector substitution, and then step 4 is executed.
4. The reconfigurable fault-tolerant control method of the hysteresis SVPWM of the single-phase voltage source multi-level inverter according to claim 3, wherein: the specific method of the step 4 is as follows:
when the voltage vector selected by the current tracking control algorithm in the non-fault state before the fault occurs is a non-fault vector, the voltage vector is the final output vector of the inverter; when the selected voltage vector is a fault vector, voltage vector substitution is needed; the voltage vector substitution methods under single-tube open circuit and double-tube open circuit faults of the inverter are shown in tables 4-5;
table 4 inverter voltage vector substitution table under single tube open circuit fault
Table 5 inverter voltage vector substitution table under double-barrelled open circuit fault
Wherein, the single-tube open-circuit faults comprise 9 kinds, and the double-tube open-circuit faults comprise 36 kinds; "v" indicates that the fault has no effect on the voltage vector and no substitution is required; in table 5, the case of writing "none" is "when the inverter has a double-pipe open circuit fault, if the output terminal lacks a positive level or lacks a negative level, fault-tolerant control cannot be achieved through inverter topology reconstruction and voltage vector substitution.
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