CN109921713B - Machine side converter fault-tolerant control method based on d-axis current injection - Google Patents
Machine side converter fault-tolerant control method based on d-axis current injection Download PDFInfo
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Abstract
The invention discloses a machine side converter fault-tolerant control method based on d-axis current injection, which adjusts d-axis given current by combining system running conditions; selecting a sector division mode to carry out sector division; determining the influence of a fault switch tube on each sector and the change of basic voltage vectors before and after a fault; determining the basic voltage vector of each sector and the acting time of the basic voltage vector before the fault; adjusting the action time of the basic voltage vector of the sector influenced by the fault switch tube; determining the conduction time of a three-phase switching tube; and modulating the conduction time of the switching tube with a triangular carrier, determining the PWM pulse of the switching tube, determining the on-off of the switching tube, and finishing the fault-tolerant control of d-axis current injection. According to the invention, the size and the phase of the fault phase current zero current hoop region are changed by changing the d-axis injection current of the generator, so that the influence of a fault switch tube on a system is reduced, and the performance of the machine side converter after the fault is improved.
Description
Technical Field
The invention relates to a machine side converter fault-tolerant control method based on d-axis current injection, and belongs to the field of power conversion and control.
Background
As the key and core of a wind power generation system, the failure or the loss of function of a converter system can seriously threaten the overall operation performance of important equipment, even bring fatal influence to the equipment, and cause catastrophic accidents. Therefore, the wind power generation system with high reliability and strong fault tolerance is established, secondary system faults caused by converter faults are avoided, important theoretical and practical significance is achieved, and strategic influences are achieved on national economic construction and national defense safety.
The existing machine side PWM converter fault-tolerant mode is divided into two categories of hardware fault-tolerant control and software fault-tolerant control, wherein the software fault-tolerant mode can carry out fault-tolerant processing on a fault by changing a system operation strategy and control parameters when a switching tube fails, the existing hardware layout of the system does not need to be changed, redundant parts do not need to be added, and the system is recovered to the operation state before the fault to the maximum extent by using devices without faults. Chinese patent 201510277790.2 proposes a fault-tolerant control method for a three-phase bridge PWM rectifier, which corrects a reference voltage vector by correcting a switching pattern, thereby realizing fault-tolerant operation of the rectifier. The method does not perform accurate compensation aiming at the influence of a fault switching tube on each sector, performs compensation on the sector without the fault of the switching tube, and belongs to overcompensation. The article "PWM rectifier fault-tolerant control system based on NCAV and circuit equivalent replacement" proposes a fault-tolerant control method of a PWM rectifier based on an equivalent circuit, which does not perform precise compensation for the influence of a faulty switching tube on each sector, and does not perform compensation in a sector where a plurality of fault vectors commonly influence, which belongs to under-compensation. A thesis 'rectifier fault-tolerant control method based on space vector control' provides a rectifier fault-tolerant control method based on space vector, a unified sector partition function is not established in the method, fault-tolerant control on faults of a plurality of bridge arm switch tubes cannot be achieved, although accurate compensation of a single switch tube can be achieved, negative effects of the fault switch tube on a system are not considered, and the effect of the fault-tolerant control is not optimal.
Disclosure of Invention
The invention aims to provide a machine side converter fault-tolerant control method based on d-axis current injection, which reduces the influence of a fault switch tube on a system and improves the performance of a machine side converter after a fault.
The technical solution for realizing the purpose of the invention is as follows: a machine side converter fault-tolerant control method based on d-axis current injection comprises the following steps:
and 7, modulating the conduction time of the switching tube with a triangular carrier, determining the PWM pulse of the switching tube, determining the on-off state of the switching tube, and finishing the fault-tolerant control of d-axis current injection.
Compared with the prior art, the invention has the following remarkable advantages: 1) the invention changes the stator current vector I by changing the reference valuesAnd a reference voltage vector V* refThe included angle between the two switching tubes improves the zero current pinch phenomenon caused by the fault switching tube and improves the fault-tolerant control effect of the fault switching tube; 2) the invention only needs to modify the software algorithm in the main controller, the algorithm is simple and easy to realize, and no additional hardware cost is needed.
Drawings
Fig. 1 is a d-axis current injection fault-tolerant control block diagram of the direct-drive wind turbine generator side converter system of the present invention.
Fig. 2 is a schematic topology diagram of a main circuit of a three-phase two-level PWM rectifier according to the present invention.
Fig. 3 is a flowchart of a fault-tolerant control method of a machine-side converter based on d-axis current injection.
Fig. 4 is an eight-sector basic space voltage vector diagram in the alpha, beta two-phase stationary frame of the present invention.
Fig. 5 is a twelve-sector basic space voltage vector diagram in the alpha, beta two-phase stationary coordinate system of the present invention.
Fig. 6 is a schematic diagram of the sector distribution of the fault of the machine side converter S1 under the effect of the fault switch tube in the eight-sector division mode.
Fig. 7 is a schematic view of the sector distribution of the double-tube fault of the machine-side current transformers S1 and S4 affected by the fault switch tube in the eight-sector division mode.
Fig. 8 is a schematic diagram of the distribution of sectors of the machine side converter S1 affected by the fault switch tube in the twelve-sector division mode.
Fig. 9 is a schematic diagram of the sector distribution of the double-tube fault of the machine-side current transformers S1 and S3 affected by the fault switch tube in the twelve-sector division mode.
Fig. 10 is a schematic diagram of the sector distribution of the double-tube fault of the machine-side current transformers S1 and S4 affected by the fault switch tube in the twelve-sector division mode.
Fig. 11 is a schematic diagram of the sector distribution of the double-tube fault of the machine-side current transformers S1 and S6 affected by the fault switch tube in the twelve-sector division mode.
Fig. 12 is a schematic view of the sector distribution of the three-tube fault of the machine-side current transformers S1, S3 and S5 of the present invention under the influence of the fault switch tube in the twelve-sector division mode.
Fig. 13 is a voltage vector composite diagram of the sector VII of the machine side converter S1 in the twelve-sector division mode under the condition of the fault.
Fig. 14 is a sector single-period PWM generating diagram of the machine-side converter S1 according to the present invention when the tube is normal.
Fig. 15 is a current vector trajectory diagram of an alpha and beta two-phase stationary coordinate system in two states of fault-tolerant control and d-axis current injection fault-tolerant control in an eight-sector division mode for a fault of an S1 tube of the machine-side converter of the invention.
Fig. 16 is a current vector trajectory diagram of an alpha-phase and beta-phase stationary coordinate system in two states of fault-tolerant control and d-axis current injection fault-tolerant control in a twelve-sector division mode for a fault of an S1 tube of the machine-side converter of the invention.
FIG. 17 is a waveform diagram of the rotating speed of the generator under four states of normal operation, fault operation, twelve-sector fault-tolerant operation and d-axis current injection fault-tolerant control of the machine-side converter S1 pipe of the invention.
The reference numbers in the figures illustrate: 6 power switch tubes in S1-S6 machine side converter, 6 freewheeling diodes in D1-D6 machine side converter, 6 fast fuses in F1-F6 machine side converter, La,Lb,LcIs the equivalent inductance of the stator winding of the generator, ua,ub,ucIs the equivalent voltage source of the generator. C is a direct current side voltage stabilizing capacitor. Three-phase current ia,ib,icThree-phase current, v, generated for a permanent-magnet synchronous generatorwIs the magnitude of natural wind speed, omegamIs the angular velocity of the permanent magnet synchronous generator, theta is the three-phase current electrical angle, id,iqIs a current feedback value under a dq two-phase rotating coordinate system,
a given value of current under a dq two-phase rotating coordinate system,
is a feedback value of the torque of the motor,
is a reference voltage component in an alpha and beta two-phase static coordinate system. t is tfAt the moment of failure of the switching tube, tcomMoment of fault-tolerant control for fault, tcom1The moment of d-axis current fault-tolerant control of the fault.
Detailed Description
The invention is further illustrated by the following examples in conjunction with the accompanying drawings.
FIG. 1 is a d-axis current injection fault-tolerant control block diagram of a machine side converter system of a permanent magnet direct-drive wind driven generator, FIG. 2 is a main circuit topology schematic diagram of a three-phase two-level PWM rectifier, and a generator side is equivalent to a three-phase voltage source ua,ub,ucAnd stator inductance La,Lb,Lc. In practical application, the probability that the power switch tube and the diode connected in anti-parallel with the power switch tube simultaneously have faults is extremely low, so that the power switch tube and the diode connected in anti-parallel with the power switch tube are still normally operated by default only considering that the power switch tube has faults. When the power switch tube in fig. 2 (S)1～S6) Faults, mainly open faults and short faults, which can be produced by a series-connected fast-acting fuse (F)1～F6) And other faults can be converted into open-circuit faults by closing the fault switching tube to drive pulse signals. In summary, the present invention provides a machine side converter with d-axis current injection for open-circuit fault of the power switch tubeThe fault-tolerant control method of the controller, as shown in fig. 3, comprises the following specific steps:
from the above equation, the rotor flux linkage psifThe equivalent inductance L of the stator is only related to the material and the structure of the permanent magnet, and is also only related to the structure of the generator, and the motor is almost unchanged when running stably. When the converter system operates stably, the d-axis current given value i can be changedd *To control the stator current vector IsAnd a reference voltage vector V* refAngle therebetween
Therefore, the size and the phase of the zero current pinch region of the fault phase current are changed, and the performance of the converter system is improved. Meanwhile, the d-axis current values required to be injected by different converter systems are different, and the injected d-axis current values are adjusted according to the formula so as to meet the requirements of the converter systems.
(1) if the eight-sector partitioning method is adopted, six variables are defined:
in the formula (I), the compound is shown in the specification,
is a reference voltage component under an alpha and beta two-phase static coordinate systemQuantity, given value by regulated d-axis current
And (6) determining.
Defining a sign function:
wherein i ═ a, B, C, D, E, F;
as the faults of the three bridge arms of a, b and c correspond to different sector division coordinate systems, in order to accurately carry out fault-tolerant control on fault sectors, a function N of the three sector division coordinate systems is defineda,Nb,Nc。
Let Na＝H(A)+H(B)+4H(C)+3H(D)
Let Nb＝4G(B)+3G(C)+G(D)+H(E)
Let Nc＝3H(B)+H(C)+4H(D)+H(F)
Determination of the calculated value N from Table 1a,Nb,NcCorresponding relation with actual sector number
TABLE 1 calculation of value Na,Nb,NcCorresponding relation with sector
| Sector numbering | Ⅰ | Ⅱ | Ⅲ | Ⅳ | Ⅴ | Ⅳ | Ⅶ | Ⅷ |
| Calculating the |
6 | 2 | 4 | 3 | 7 | 5 | 1 | 8 |
| Calculating the |
2 | 4 | 3 | 7 | 5 | 6 | 1 | 8 |
| Calculating the |
4 | 3 | 7 | 5 | 6 | 2 | 1 | 8 |
According to reference voltage components in alpha and beta two-phase static coordinate systems
Determining a rotating reference vector Vref *When rotating the reference vector Vref *Rotating for one circle to obtain a calculated value NaThe sequence of change of (A) is: 6 → 2 → 1 → 4 → 3 → 7 → 8; calculating the value NbThe sequence of change of (2 → 1 → 4 → 3 → 7 → 8 → 5 → 6; calculating the value NcThe sequence of change of (a) is 4 → 3 → 7 → 8 → 5 → 6 → 2 → 1;
selecting different sector division functions according to the positions of the fault switching tubes, and selecting the sector division function N when the a-phase bridge arm switching tube has a faultaThrough NaThe change sequence of the actual sector numbers is determined, that is, the eight-sector division is as shown in fig. 4 (a); when a b-phase bridge arm switching tube fault selects a sector division function NbThrough NbThe change sequence of the actual sector numbers is determined, that is, the division of eight sectors is shown in fig. 4 (b); when a c-phase bridge arm switching tube fault selects a sector division function NcThrough NcThe change sequence of the actual sector numbers is determined, that is, the eight-sector division is as shown in fig. 4 (c);
(2) if a twelve-sector division method is adopted, a symbol function is defined:
wherein i is a, B, C, D, E, F.
Let N ═ sign (A) + sign (B) +2sign (C) +2sign (D) +4sign (E) +3sign (F)
Determining the corresponding relation between the calculated value N and the actual sector number through the table 2;
TABLE 2 calculated value N and sector corresponding relation
| Calculating the |
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| Sector numbering | Ⅷ | Ⅱ | Ⅲ | Ⅶ | Ⅳ | Ⅸ | Ⅻ | Ⅰ | Ⅹ | Ⅵ | Ⅴ | Ⅺ |
According to reference voltage components in alpha and beta two-phase static coordinate systems
Determining a rotating reference vector Vref *When rotating the reference vector Vref *After one rotation, the change sequence of the calculated values N is as follows: 8 → 4 → 2 → 1 → 3 → 6 → 5 → 9 → 11 → 12 → 10 → 7 → 8, i.e. the order of change of the actual sector numbers, i.e. the division of the twelve sectors is shown in FIG. 5.
the method for determining the influence of a fault switching tube on each sector and dividing the fault sector and the normal sector comprises the following steps:
if an eight-sector division mode is adopted, determining the sectors affected by the fault switching tube in the eight sectors, namely fault sectors, according to the tables 3-5; if a twelve-sector division mode is adopted, determining the sector influenced by the fault switch tube in the twelve sectors according to the table 6;
TABLE 3 affected sectors corresponding to eight-sector a-phase bridge arm switching tube fault
| Sequence number of fault switch tube | Ⅰ | Ⅱ | Ⅲ | Ⅳ | Ⅴ | Ⅵ | Ⅶ | Ⅷ |
| S1(a phase upper arm) | ||||||||
| S4(a phase lower arm) |
Table 4 affected sectors corresponding to eight-sector b-phase bridge arm switching tube fault
| Sequence number of fault switch tube | Ⅰ | Ⅱ | Ⅲ | Ⅳ | Ⅴ | Ⅵ | Ⅶ | Ⅷ |
| S3(B phase upper arm) | ||||||||
| S6(B phase lower arm) |
TABLE 5 affected sectors corresponding to eight-sector c-phase bridge arm switching tube faults
| Sequence number of fault switch tube | Ⅰ | Ⅱ | Ⅲ | Ⅳ | Ⅴ | Ⅵ | Ⅶ | Ⅷ |
| S5(C phase upper arm) | ||||||||
| S2(C phase lower arm) |
TABLE 6 affected sectors corresponding to twelve-sector single switch tube failure
| Number of switch tube | Ⅰ | Ⅱ | Ⅲ | Ⅳ | Ⅴ | Ⅵ | Ⅶ | Ⅷ | Ⅸ | Ⅹ | Ⅺ | Ⅻ |
| S1(a phase upper arm) | ||||||||||||
| S4(a phase lower arm) | ||||||||||||
| S3(B phase upper arm) | ||||||||||||
| S6(B phase lower arm) | ||||||||||||
| S5(C phase upper arm) | ||||||||||||
| S2(C phase lower arm) |
In the table, the gray part indicates that the sector is affected by the faulty switching tube, i.e. the faulty sector, and the white part indicates that the sector is not affected by the faulty switching tube, i.e. the normal sector.
The method for determining the basic voltage vectors before and after the fault of the switching tube comprises the following steps: determining the change conditions of basic voltage vectors, namely a fault zero vector and an effective vector before and after the fault of the switching tube according to the table 7, and determining a fault voltage vector;
TABLE 7 Voltage vector variation before and after single switch tube failure
In the table, the upper and lower switching states of the same bridge arm are set to be complementary, that is, the upper bridge arm of the same bridge arm is turned on, the lower bridge arm must be turned off, the state is recorded as 1, similarly, the upper bridge arm of the same bridge arm is turned off, the lower bridge arm is turned on, the state is recorded as 0, and under the premise that the three bridge arms are complementary to the same bridge arm, 8 switching state combinations are provided, wherein "000", "100", "110", "010", "011", "001", "101" and "111" correspond to eight basic voltage vectors, and the eight basic voltage vectors include six effective vectors and two zero vectors.
first, the intermediate variables are defined as:
in the formula (I), the compound is shown in the specification,
is a reference voltage component in an alpha and beta two-phase stationary coordinate system, UdcFor the output voltage of the DC side, TsIs a sampling period;
then, determining the action time T of the effective vector in the basic voltage vector of each sector1And T2；
If the voltage vector is eight sectors, determining the action time T of the effective vector in the basic voltage vector of each sector according to tables 8-101And T2；
TABLE 8 a relationship between the action time of the sector and the basic voltage vector during the phase bridge arm failure
TABLE 9 b relationship between the action time of the sector and the basic voltage vector during the phase bridge arm failure
TABLE 10 c relationship between the action time of the sector and the basic voltage vector during the phase bridge arm failure
If the voltage vector is twelve sectors, determining the action time T of the effective vector in the basic voltage vector of each sector according to the table 111And T2；
TABLE 11 sector vs. base Voltage vector action time relationship
Then, the effective vector is applied for a time T1And T2Calculating the action time T of the zero vector in the basic voltage vector0＝Ts-T1-T2；
Finally, overmodulation judgment is carried out, namely whether the sum of two times is greater than a sampling period is judged after the action time of two non-zero basic voltage vectors is calculated, if the sum of the two times is greater than the sampling period, the output voltage is seriously distorted, the two times need to be redistributed, and the distribution principle is as follows:
the resultant reference voltage rotation vector Vref *The proportionality coefficients are:
namely:
the specific method for adjusting the action time of the basic voltage vector of the sector influenced by the fault switch tube comprises the following steps:
(1) adopts an eight-sector division mode
For the sector only affected by the zero vector and without simultaneous fault of the zero vector, the normal zero vector is used to replace the fault zero vector, i.e. the action time of the normal zero vector is set as T0Realizing the fault-tolerant control of the sector;
for the sector which is affected by a plurality of fault voltage vectors and has no simultaneous fault of zero vectors, the normal zero vector is used for replacing the fault zero vector to complete the compensation of the zero vector, the effective vector without fault is used, the effective vector action time is calculated based on the compensation principle to synthesize the reference voltage rotation vector V againref *Realizing the fault-tolerant control of the sector, wherein the compensation principle comprises a mapping method, an equiaxial component method and an equiaxial method;
(2) adopts a twelve-sector division mode
For the sector only affected by the zero vector and without simultaneous fault of the zero vector, the normal zero vector is used to replace the fault zero vector, i.e. the action time of the normal zero vector is set as T0Implementing fault-tolerant control of the sector, T0Acting time of zero vector before fault;
for the sectors which are affected by a plurality of fault voltage vectors and have no simultaneous fault in the zero vector, the normal zero vector is used for replacing the fault zero vector, the effective vector without the fault is used, the effective vector action time is calculated based on the compensation principle to synthesize the reference voltage rotation vector V againref *Realizing the fault-tolerant control of the sector, wherein the compensation principle comprises a mapping method, an equiaxial component method and an equiaxial method;
for the sector with simultaneous fault of zero vectors, because no normal zero vector exists in the sector, the output vector can not be adjusted, and the reference voltage rotates the vector Vref *The output module value reaches the maximum, and the sector can not carry out fault-tolerant control;
common effects for multiple fault vectorsAnd the sector with the fault zero vector can not adjust the output vector because the normal zero vector does not exist in the sector, and the reference voltage rotates the vector Vref *The output modulus reaches the maximum, and the sector can not carry out fault-tolerant control.
Each compensation time determination method is described in detail below.
The mapping method is a method commonly used in the prior art, and is not described herein again.
The normal mode method is to make vector V before faultref *The compensation time of the effective vector is calculated in conformity with the modulo length of the effective vector. Namely, the normal zero vector is used to replace the fault zero vector to complete the compensation of the zero vector, and the effective vector without fault is used to rotate the reference voltage by a vector Vref *Orthogonally mapped to the effective vector, rotating the vector V based on the reference voltageref *Calculating action time of normal effective vector by using equal modulus principle
Implementing fault tolerant control of the sector.
The equiaxed component method is the vector V to be before failureref *And projecting the effective vector on a beta axis, and calculating effective vector compensation time based on the same components. I.e. replacing the fault zero vector by a normal zero vector and rotating the reference voltage by a vector Vref *Projected on a beta axis, calculating the compensation ratio of the normal effective voltage vector based on the principle of equal beta axis components, namely setting the action time T of the normal effective vector1+T2Implementing fault-tolerant control of the sector, T1And T2The action time of two effective vectors before the fault.
And 6, determining the conduction time of the three-phase switch tube according to the action time and the sector type of the basic voltage vector, wherein the specific method comprises the following steps:
(1) adopts an eight-sector division mode
Preferably, for a sector which is not affected by a fault vector, the conduction time of a three-phase switch tube is defined as:
in the formula, TsFor a sampling period, T1And T2The action time of the effective vector;
at this time, the reference voltage rotates the vector
Taking the vector synthesis of the voltage of the sector VII under the twelve-sector division function of the S1 pipe fault as an example, as shown in FIG. 12, the implementation of the continuous pulse width modulation on the reference voltage V is realizedref *And (4) synthesizing.
Defective sector by redefining defective sector Ta,Tb,TcTime variable, compensation of fault vector in each fault sector, i.e. replacement of fault vector based on specific equivalence principle by using effective vector, rotating reference voltage by vector Vref *The method can be used for re-synthesizing or approximately recovering in a fault sector, and comprises the following specific steps:
for the sector which is only affected by the zero vector and has no simultaneous fault of the zero vector, the conduction time of the three-phase switch tube is changed only in the sector affected by the zero vector, and the T is redefineda,Tb,Tc；
When the position of the fault switch tube is the upper bridge arm, redefining as:
when the position of the fault switch tube is the lower bridge arm, redefining as:
for the sector affected by the effective vector and without simultaneous fault of the zero vector, the conducting time of the three-phase switch tube is changed only in the sector affected by the zero vector according to theRedefining T of action time calculated by compensation principlea,Tb,TcThe compensation principle is different from the definition formula.
(a) The mapping method is a method commonly used in the prior art, and how to redefine T is not described herein againa,Tb,Tc。
(b) For the isocode method: when the position of the fault switch tube is the upper bridge arm, redefining as:
when the position of the fault switch tube is the lower bridge arm, redefining as:
(c) for the equiaxed component method: when the position of the fault switch tube is the upper bridge arm, redefining as:
when the position of the fault switch tube is the lower bridge arm, redefining as:
then, determining the switching time of each sector according to tables 12-14;
TABLE 12 relationship between the action time of the sector and the basic voltage vector when the eight-sector a-phase bridge arm fails
TABLE 13 relationship between the action time of the sector and the basic voltage vector when the eight-sector b-phase bridge arm fails
TABLE 14 relationship between the action time of the sectors and the basic voltage vector during eight-sector c-phase bridge arm failure
(2) Adopts a twelve-sector division mode
Preferably, for a sector which is not affected by a fault vector, the conduction time of a three-phase switch tube is defined as:
in the formula, TsFor a sampling period, T1And T2The action time of the effective vector;
for the sector which is only affected by the zero vector and has no simultaneous fault of the zero vector, the conduction time of the three-phase switch tube is changed only in the sector affected by the zero vector, and the T is redefineda,Tb,Tc；
When the position of the fault switch tube is the upper bridge arm, redefining as:
when the position of the fault switch tube is the lower bridge arm, redefining as:
for the sectors which are commonly influenced by a plurality of fault voltage vectors and have no simultaneous fault in the zero vector, the conduction time of the three-phase switch tube is only required to be changed in the sectors influenced by the zero vector, and the calculation is carried out according to the compensation principleRedefining T of the duration of actiona,Tb,TcDifferent definition formulas of the compensation principle are different, and the compensation principle is specifically the same as the calculation formula of the eight-sector type sector;
then, determining the switching time of each sector according to the table 15;
TABLE 15 on-off time distribution relationship of different sectors of twelve sectors
| Sector numbering | Ⅰ | Ⅱ | Ⅲ | Ⅳ | Ⅴ | Ⅵ | Ⅶ | Ⅷ | Ⅸ | Ⅹ | Ⅺ | Ⅻ |
| Conduction time of A-phase switch tubeTa | Ta | Tb | Tc | Tc | Tb | Ta | Ta | Tb | Tc | Tc | Tb | Ta |
| Conduction time T of B-phase switch tubeb | Tb | Ta | Ta | Tb | Tc | Tc | Tb | Ta | Ta | Tb | Tc | Tc |
| Conduction time T of C-phase switch tubec | Tc | Tc | Tb | Ta | Ta | Tb | Tc | Tc | Tb | Ta | Ta | Tb |
And 7, modulating the conduction time of the switching tube with a triangular carrier, determining PWM (pulse-width modulation) pulse of the switching tube, determining the on-off state of the switching tube, and finishing d-axis current injection fault-tolerant control, wherein the specific method comprises the following steps of: the method comprises the steps of modulating isosceles triangle waves with the conduction time and the period of a switching tube as sampling periods, determining the action sequence of vectors by adopting a DWPM technology based on a symmetry principle and a THD minimum principle to obtain 6 paths of PWM pulses, acting the output 6 paths of PWM pulses on a power switching tube driving circuit, and controlling the corresponding power switching tube to be switched on and switched off by the driving circuit to finish d-axis current injection fault-tolerant control.
By adopting the technical scheme, the invention changes the d-axis current given value id *To control the stator current vector IsAnd a reference voltage vector V* refThe included angle between the two adjacent switching tubes is changed, so that the size and the phase of a fault phase current zero-current hoop region are changed, the fault-tolerant control effect of the fault of the switching tube of the machine side converter can be improved, and the influence of the fault switching tube on a system is further reduced on the basis of software fault-tolerant control. The scheme is simple and easy to realize by modifying the control algorithm of the controller software without increasing extra hardware cost.
To verify the effectiveness of the present invention, the following simulations were performed.
Example 1
The embodiment is described by a single-tube fault S1 of a machine-side converter of a direct-drive wind power generation system in an eight-sectorization mode, when a short-circuit fault occurs in a tube S1, the tube S is converted into an open-circuit fault by a fast fuse, and when an open-circuit fault occurs in a tube S1, a d-axis current injection method is described according to state analysis of the machine-side converter in the eight-sectorization mode under the fault of a switch tube S1 in a table 16.
The sector distribution schematic diagram of the fault of the machine-side converter S1 under the effect of the fault switch tube in the eight-sector division mode is shown in FIG. 6, and when the S1 tube has a fault, the d-axis current set value is adjusted according to the system running state. Then, for the sector which is not affected by the faulty switch tube in the table 16, the normal reference voltage rotation vector is controlled, and the continuous pulse width modulation is realized through the seven-segment switch sequence to the reference voltage Vref *And (4) synthesizing. For the sectors affected by the faulty switch tube in the table 16, software fault-tolerant control is performed by redefining the faulty sector Ta，Tb，TcTime variable, compensation of fault vector in each fault sector, i.e. replacement of fault vector based on specific equivalence principle by using effective vector, rotating reference voltage by vector Vref *It can be resynthesized or approximately recovered in the failed sector. Setting the frequency, amplitude and phase of triangular carrier wave in main controller to change the time variation T of all sectorsa，Tb，TcAnd respectively modulating with a triangular carrier to obtain 6 paths of PWM pulse signals. 6 paths of pulse signals are input into a power switch tube driving circuit, so that d-axis current injection fault-tolerant control of single-tube faults of a machine side converter S1 in an eight-sector division mode is realized, a current vector locus diagram of an alpha and beta two-phase static coordinate system in two states of fault-tolerant control and d-axis current fault-tolerant control of the machine side converter S1 tube fault in an eight-sector division mode is shown in figure 15, and the situation that the fault-tolerant control and the d-axis current fault-tolerant control are realizedThe implementation of the fault-tolerant control method based on d-axis current injection not only inhibits the zero-current pinch phenomenon, but also enables the corresponding track circle to more approach to a perfect circle. When other switching tubes have faults under other conditions, the fault-tolerant control method for d-axis current injection is adopted for fault tolerance.
Example 2
In the embodiment, a single-tube fault S1 of a machine-side converter of a direct-drive wind power generation system in a twelve-sector division mode is used for explaining, when a short-circuit fault occurs in a tube S1, the tube S is converted into an open-circuit fault by a fast fuse, and when an open-circuit fault occurs in a tube S1, a fault-tolerant control method for injecting d-axis current is explained according to state analysis of the machine-side converter in the twelve-sector division mode under the fault of a switch tube S1 in table 17.
Twelve-sector single-cycle state analysis of PWM rectifier under 17S 1 switching tube fault
A sector distribution schematic diagram of the fault of the machine-side converter S1 under the influence of the fault switch tube in the twelve-sector division mode is shown in fig. 8, and when the fault occurs in the S1 tube, the d-axis current set value is adjusted according to the system running state. Then, for the sector which is not affected by the fault switch tube in the table 17, the normal reference voltage rotation vector is controlled, and the continuous pulse width modulation is realized through the seven-segment switch sequence to the reference voltage Vref *And (4) synthesizing. For the sector affected by the fault switch tube in the table 17, the software fault-tolerant control is carried out, and the fault sector T is redefineda，Tb，TcTime variable, compensation of fault vector in each fault sector, i.e. replacement of fault vector based on specific equivalence principle by using effective vector, rotating reference voltage by vector Vref *It can be resynthesized or approximately recovered in the failed sector. At the main controllerSetting the frequency, amplitude and phase of triangular carrier wave, and converting the time variation T of all sectorsa，Tb，TcAnd respectively modulating with a triangular carrier to obtain 6 paths of PWM pulse signals. And 6 paths of pulse signals are input into a power switch tube driving circuit, so that d-axis current injection fault-tolerant control of single tube faults of the machine side converter S1 in a twelve-sector division mode is realized, and when other switch tubes are in faults, the fault tolerance is carried out by adopting the d-axis current injection fault-tolerant control method.
Fig. 16 is a current vector trajectory diagram of an alpha-phase and beta-phase stationary coordinate system in two states of fault-tolerant control and d-axis current injection fault-tolerant control in a twelve-sector division mode for a fault of an S1 tube of the machine-side converter of the invention. FIG. 17 is a waveform diagram of the rotating speed of the generator under four states of normal operation, fault operation, twelve-sector fault-tolerant operation and d-axis current injection fault-tolerant control of the machine-side converter S1 pipe of the invention. It can be seen that the zero-current pinch phenomenon is suppressed by implementing the d-axis current injection fault-tolerant control method, and the corresponding current track circular track is more close to a normal state. The simulation result proves the effectiveness of the method because the rotating speed of the generator slightly rises due to the change of the d-axis current, but the fluctuation amplitude of the generator is reduced.
In addition to the single switching tube failure case described above, the inventive solution is equally applicable to multiple switching tube failure cases, as shown in fig. 7, and in fig. 9-14.
Claims (8)
1. The machine side converter fault-tolerant control method based on d-axis current injection is characterized by comprising the following steps of:
step 1, adjusting a d-axis current given value according to a system running state;
step 2, selecting a sector division mode and carrying out sector division;
step 3, determining the influence of the fault switch tube on each sector and the change of the basic voltage vector before and after the fault according to the position of the fault switch tube;
step 4, determining the basic voltage vector of each sector and the acting time of the basic voltage vector before the fault;
step 5, adjusting the action time of the basic voltage vector of the sector influenced by the fault switching tube according to the sector influenced by the fault switching tube, the change of the basic voltage vector after the fault and the action time of the basic voltage vector before the fault;
step 6, determining the conduction time of the three-phase switch tube according to the action time of the basic voltage vector and the condition that the sector is influenced by the fault switch tube;
step 7, modulating the conduction time of the switching tube with a triangular carrier, determining PWM (pulse-width modulation) pulse of the switching tube, determining the on-off state of the switching tube, and finishing d-axis current injection fault-tolerant control;
in step 1, adjusting the d-axis current set value
The specific method comprises the following steps:
in the formula, #fIs a rotor flux linkage, and is only related to permanent magnet materials and structures; l is the equivalent inductance value of the stator and is only related to the structure of the generator; i.e. iqIs the current feedback value of the q-axis,
as stator current vector IsAnd a rotating reference voltage vector V* refThe included angle therebetween.
2. The fault-tolerant control method for the machine-side converter for d-axis current injection according to claim 1, wherein in the step 2, the sector division mode includes eight sectors and twelve sectors, and the specific process of the two sectors division is as follows:
(1) adopts an eight-sector division mode
Six variables are defined:
in the formula of Uα、UβThe reference voltage component is a reference voltage component under an alpha and beta two-phase static coordinate system;
defining a sign function:
wherein i ═ a, B, C, D, E, F;
as the faults of the three bridge arms of a, b and c correspond to different sector division coordinate systems, in order to accurately carry out fault-tolerant control on fault sectors, a function N of the three sector division coordinate systems is defineda,Nb,Nc；
Let Na＝H(A)+H(B)+4H(C)+3H(D)
Let Nb＝4G(B)+3G(C)+G(D)+H(E)
Let Nc＝3H(B)+H(C)+4H(D)+H(F)
Determination of the calculated value N from Table 1a,Nb,NcCorresponding relation with actual sector number
TABLE 1 calculation of value Na,Nb,NcCorresponding relation with sector
According to a reference voltage component U in an alpha and beta two-phase static coordinate systemα、UβDetermining a rotating reference vector Vref *When rotating the reference vector Vref *Rotating for one circle to obtain a calculated value NaThe sequence of change of (A) is: 6 → 2 → 1 → 4 → 3 → 7 → 8 → 5; calculating the value NbThe sequence of change of (2 → 1 → 4 → 3 → 7 → 8 → 5 → 6; calculating the value NcThe sequence of change of (a) is 4 → 3 → 7 → 8 → 5 → 6 → 2 → 1;
selecting different sector division coordinate system functions according to the positions of the fault switching tubes, and when the fault of the a-phase bridge arm switching tube selects the sector division coordinate system function NaThrough NaDetermining the change sequence of the actual sector numbers according to the change sequence to obtain the division of eight sectors; when a b-phase bridge arm switching tube fault selection sector divides a coordinate system function NbThrough NbDetermining the change sequence of the actual sector numbers according to the change sequence to obtain the division of eight sectors; dividing coordinate system function N when fault selection sector of c-phase bridge arm switching tubecThrough NcDetermining the change sequence of the actual sector numbers according to the change sequence to obtain the division of eight sectors;
(2) adopts a twelve-sector division mode
Six variables are defined:
in the formula of Uα、UβThe reference voltage component is a reference voltage component under an alpha and beta two-phase static coordinate system;
defining a sign function:
wherein i ═ a, B, C, D, E, F;
let N ═ sign (A) + sign (B) +2sign (C) +2sign (D) +4sign (E) +3sign (F)
Determining the corresponding relation between the calculated value N and the actual sector number through the table 2;
TABLE 2 calculated value N and sector corresponding relation
According to a reference voltage component U in an alpha and beta two-phase static coordinate systemα、UβDetermining a rotating reference vector Vref *When rotating the reference vector Vref *After one rotation, the change sequence of the calculated values N is as follows: 8 → 4 → 2 → 1 → 3 → 6 → 5 → 9 → 11 → 12 → 10 → 7 → 8, i.e. the order of change of the actual sector numbers, i.e. the division of the twelve sectors.
3. The fault-tolerant control method for the machine-side converter for d-axis current injection according to claim 1, wherein in the step 3, if an eight-sector division mode is adopted, a sector affected by a fault switch tube, namely a fault sector, in eight sectors is determined according to tables 3-5; if a twelve-sector division mode is adopted, determining the sector influenced by the fault switch tube in the twelve sectors according to the table 6;
TABLE 3 affected sectors corresponding to eight-sector a-phase bridge arm switching tube fault
Table 4 affected sectors corresponding to eight-sector b-phase bridge arm switching tube fault
TABLE 5 affected sectors corresponding to eight-sector c-phase bridge arm switching tube faults
TABLE 6 affected sectors corresponding to twelve-sector single switch tube failure
In the table, the gray part indicates that the sector is affected by the faulty switching tube, i.e. the faulty sector, and the white part indicates that the sector is not affected by the faulty switching tube, i.e. the normal sector.
4. The fault-tolerant control method of the machine-side converter for d-axis current injection according to claim 1, wherein in the step 3, the change conditions of basic voltage vectors, namely a fault zero vector and an effective vector, before and after the fault of the switching tube are determined according to a table 7;
TABLE 7 Voltage vector variation before and after single switch tube failure
In the table, the upper and lower switching states of the same bridge arm are set to be complementary, that is, the upper bridge arm of the same bridge arm is turned on, the lower bridge arm must be turned off, the state is recorded as 1, similarly, the upper bridge arm of the same bridge arm is turned off, the lower bridge arm is turned on, the state is recorded as 0, and under the premise that the three bridge arms are complementary to the same bridge arm, 8 switching state combinations are provided, wherein "000", "100", "110", "010", "011", "001", "101" and "111" correspond to eight basic voltage vectors, and the eight basic voltage vectors include six effective vectors and two zero vectors.
5. The fault-tolerant control method for the machine-side converter with d-axis current injection as claimed in claim 1, wherein in step 4, the specific method for determining the action time of the basic voltage vector of each sector before the fault comprises the following steps:
first, the intermediate variables are defined as:
in the formula of Uα、UβIs a reference voltage component in an alpha and beta two-phase stationary coordinate system, UdcFor the output voltage of the DC side, TsIs a sampling period;
then, determining the action time T of the effective vector in the basic voltage vector of each sector1And T2；
If the voltage vector is eight sectors, determining the action time T of the effective vector in the basic voltage vector of each sector according to tables 8-101And T2；
TABLE 8 a relationship between the action time of the sector and the basic voltage vector during the phase bridge arm failure
TABLE 9 b relationship between the action time of the sector and the basic voltage vector during the phase bridge arm failure
TABLE 10 c relationship between the action time of the sector and the basic voltage vector during the phase bridge arm failure
If the voltage vector is twelve sectors, determining the action time T of the effective vector in the basic voltage vector of each sector according to the table 111And T2；
TABLE 11 sector vs. base Voltage vector action time relationship
Then, the effective vector is applied for a time T1And T2Calculating the action time T of the zero vector in the basic voltage vector0＝Ts-T1-T2；
Finally, overmodulation judgment is carried out, namely whether the sum of two times is greater than a sampling period is judged after the action time of two non-zero basic voltage vectors is calculated, if the sum of the two times is greater than the sampling period, the output voltage is seriously distorted, the two times need to be redistributed, and the distribution principle is as follows:
6. the fault-tolerant control method for the machine-side converter with d-axis current injection as claimed in claim 1, wherein in step 5, the specific method for adjusting the action time of the basic voltage vector of the sector affected by the fault switch tube is as follows:
(1) adopts an eight-sector division mode
For the sector only affected by the zero vector and without simultaneous fault of the zero vector, the normal zero vector is used to replace the fault zero vector, i.e. the action time of the normal zero vector is set as T0Realizing the fault-tolerant control of the sector;
for the sector which is affected by a plurality of fault voltage vectors and has no simultaneous fault of zero vectors, the normal zero vector is used for replacing the fault zero vector to complete the compensation of the zero vector, the effective vector without fault is used, the effective vector action time is calculated based on the compensation principle to synthesize the reference voltage rotation reference vector V againref *Realizing the fault-tolerant control of the sector, wherein the compensation principle comprises a mapping method, an equiaxial component method and an equiaxial method;
(2) adopts a twelve-sector division mode
For the sector only affected by the zero vector and without simultaneous fault of the zero vector, the normal zero vector is used to replace the fault zero vector, i.e. the action time of the normal zero vector is set as T0Implementing fault-tolerant control of the sector, T0Acting time of zero vector before fault;
for the sectors which are affected by a plurality of fault voltage vectors and have no simultaneous fault in the zero vector, the normal zero vector is used for replacing the fault zero vector, the effective vector without the fault is used, the effective vector action time is calculated based on the compensation principle to synthesize the reference voltage rotation reference vector V againref *Realizing the fault-tolerant control of the sector, wherein the compensation principle comprises a mapping method, an equiaxial component method and an equiaxial method;
for zero vector simultaneous eventThe sector of the barrier, in which no normal zero vector exists, cannot regulate the output vector, the reference voltage rotates the reference vector Vref *The output module value reaches the maximum, and the sector can not carry out fault-tolerant control;
for a sector which is affected by a plurality of fault vectors and has a fault at the same time, because the sector has no normal zero vector, the output vector can not be adjusted, and the reference voltage rotates the reference vector Vref *The output modulus reaches the maximum, and the sector can not carry out fault-tolerant control.
7. The fault-tolerant control method for the machine-side converter for d-axis current injection according to claim 1, wherein in the step 6, the method for determining the on-time of the switching tube of each sector comprises the following steps:
(1) adopts an eight-sector division mode
Preferably, for a sector which is not affected by a fault vector, the conduction time of a three-phase switch tube is defined as:
in the formula, TsFor a sampling period, T1And T2The action time of the effective vector;
for the sector which is only affected by the zero vector and has no simultaneous fault of the zero vector, the conduction time of the three-phase switch tube is changed only in the sector affected by the zero vector, and the T is redefineda,Tb,Tc；
When the position of the fault switch tube is the upper bridge arm, redefining as:
when the position of the fault switch tube is the lower bridge arm, redefining as:
for the sector affected by the effective vector and without simultaneous fault of the zero vector, the conduction time of the three-phase switch tube is changed only in the sector affected by the zero vector, and the T is redefineda,Tb,TcThe compensation principles are different, and the definition formulas are also different;
the compensation principle comprises a mapping method, an equal-mode method and an equiaxed component method, and when the position of a fault switching tube is an upper bridge arm in the equal-mode method, the position is redefined as:
when the position of the fault switch tube is the lower bridge arm, redefining as:
for the equiaxial component method, when the position of the fault switching tube is the upper bridge arm, the redefinition is that:
when the position of the fault switch tube is the lower bridge arm, redefining as:
then, determining the switching time of each sector according to tables 12-14;
TABLE 12 relationship between the action time of the sector and the basic voltage vector when the eight-sector a-phase bridge arm fails
TABLE 13 relationship between the action time of the sector and the basic voltage vector when the eight-sector b-phase bridge arm fails
TABLE 14 relationship between the action time of the sectors and the basic voltage vector during eight-sector c-phase bridge arm failure
(2) Adopts a twelve-sector division mode
Preferably, for a sector which is not affected by a fault vector, the conduction time of a three-phase switch tube is defined as:
in the formula, TsFor a sampling period, T1And T2The action time of the effective vector;
for the sector which is only affected by the zero vector and has no simultaneous fault of the zero vector, the conduction time of the three-phase switch tube is changed only in the sector affected by the zero vector, and the T is redefineda,Tb,Tc；
When the position of the fault switch tube is the upper bridge arm, redefining as:
when the position of the fault switch tube is the lower bridge arm, redefining as:
for the sector which is commonly influenced by a plurality of fault voltage vectors and has no simultaneous fault of the zero vector, the conduction time of the three-phase switch tube is changed only in the sector influenced by the zero vector, and the T is redefineda,Tb,TcThe compensation principle has different definition formulas, and is specifically the same as the calculation formula of the compensation principle of eight sectors;
then, determining the switching time of each sector according to the table 15;
TABLE 15 on-off time distribution relationship of different twelve sectors
。
8. The fault-tolerant control method for the machine-side converter with d-axis current injection as claimed in claim 1, wherein in step 7, the specific method for completing the fault-tolerant control of d-axis current injection comprises: the method comprises the steps of modulating isosceles triangle waves with the conduction time and the period of a switching tube as sampling periods, determining the action sequence of vectors by adopting a DPWM technology based on a symmetry principle and a THD minimum principle to obtain 6 paths of PWM pulses, acting the output 6 paths of PWM pulses on a power switching tube driving circuit, and controlling the corresponding power switching tube to be switched on and switched off by the driving circuit to finish d-axis current injection fault-tolerant control.
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