CN113507247B - A Compatibility Constraint Method for MEA Frequency Conversion AC Electrical System - Google Patents
A Compatibility Constraint Method for MEA Frequency Conversion AC Electrical System Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
- H02P9/10—Control effected upon generator excitation circuit to reduce harmful effects of overloads or transients, e.g. sudden application of load, sudden removal of load, sudden change of load
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P9/00—Arrangements for controlling electric generators for the purpose of obtaining a desired output
- H02P9/14—Arrangements for controlling electric generators for the purpose of obtaining a desired output by variation of field
- H02P9/26—Arrangements for controlling electric generators for the purpose of obtaining a desired output by variation of field using discharge tubes or semiconductor devices
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Abstract
本发明提供了一种MEA变频交流电气系统的兼容性约束方法，该方法从MEA变频交流电气系统电能质量的角度出发，首先判断整流型负载输入端口的谐波电流含量，在其满足接入标准的前提下，建立系统的等值电路，再根据等值电路推导MEA变频交流主母线各阶次谐波电压的表达式。然后依据变频交流母线电压最大畸变频谱约束MEA变频交流主母线中权重系数最大的谐波电压的幅值，而谐波电压的幅值取决于整流型负载直流侧输出电流的大小，因此可以求得整流型负载直流侧输出电流的最大值，进而得到整流型负载输出功率的最大值。该方法可以定量分析MEA变频交流电气系统在特定工况下，兼容任意整流型负载的功率边界，为MEA变频交流电气系统的兼容性评估提供参考和依据。
The invention provides a compatibility constraint method of MEA frequency conversion AC electrical system, the method starts from the perspective of power quality of MEA frequency conversion AC electrical system, first judges the harmonic current content of the input port of the rectifier load, and when it meets the access standard Under the premise of , the equivalent circuit of the system is established, and then the expression of the harmonic voltage of each order of the MEA frequency conversion AC main bus is deduced according to the equivalent circuit. Then, according to the maximum distortion spectrum of the variable frequency AC bus voltage, the amplitude of the harmonic voltage with the largest weight coefficient in the MEA variable frequency AC main bus is constrained, and the amplitude of the harmonic voltage depends on the output current of the DC side of the rectified load, so it can be obtained The maximum value of the output current of the DC side of the rectified load, and then the maximum value of the output power of the rectified load. This method can quantitatively analyze the power boundary of MEA variable frequency AC electrical system compatible with any rectifier load under specific working conditions, and provide reference and basis for the compatibility evaluation of MEA variable frequency AC electrical system.
Description
Technical Field
The invention relates to a compatibility constraint method of a variable frequency alternating current electric system of a multi-electric aircraft (More Electric Aircraft, MEA), in particular to a compatibility constraint method of an MEA variable frequency alternating current electric system which is based on electric energy quality and can quantitatively analyze a power boundary compatible with a rectification type load, and belongs to the field of airborne electric systems.
Background
The secondary energy sources in the aircraft include forms of electric energy, hydraulic energy, pneumatic energy and the like. Compared with hydraulic energy and pneumatic energy, the electric energy has the advantages of higher efficiency, easier transmission and regulation and control and the like. The MEA gradually replaces hydraulic energy and pneumatic energy with electric energy, so that the electric energy occupies a main role in secondary energy, and the purposes of reducing the volume and weight of the aircraft, improving the reliability of the aircraft, improving the fuel utilization rate and the like are achieved. Fig. 2 shows a simplified MEA variable frequency ac electrical system architecture, and it can be seen that the overall system incorporates a large number of rectifying loads. The rectification type load is a main harmonic source of the MEA variable-frequency alternating-current electric system, harmonic currents generated by the harmonic sources flow into an armature winding of a variable-frequency alternating-current three-stage generator (Variable Frequency AC Three Stage Generator, VFAC-TSG), and vibration and even torsional vibration of a transmission shaft connected with the VFAC-TSG can be caused through harmonic armature reaction, so that adverse effects are caused on an aeroengine connected coaxially, and the safe operation of an airplane is threatened. With the increasing electrification of the secondary energy systems of aircraft, the power level of the rectifying type load in the MEA variable frequency ac electrical system is gradually increasing, which causes the harmonic pollution of the system to be more serious. Therefore, it is necessary to constrain the power of MEA variable frequency ac electrical systems compatible with rectifying loads.
In order to restrict compatibility between a power supply and electric equipment in an MEA variable-frequency alternating-current electric system, aviation technical standards such as GJB-181B and DO-160G all provide corresponding technical indexes from the angles of power supply or electricity utilization. The technical indexes aiming at the electric equipment are provided from the angle of the input port characteristic of the single electric equipment, namely the input port characteristic of the electric equipment meets the corresponding technical indexes, and the MEA variable-frequency alternating-current electric system can be accessed. However, according to the technical indexes, the MEA variable-frequency alternating-current electric system cannot be quantitatively constrained from being compatible with the power of an electric load under a specific working condition.
At present, the compatibility of the MEA variable frequency alternating current electric system is relatively less studied, and the compatibility of the MEA variable frequency alternating current electric system can only be restrained according to related aviation technical standards. On one hand, the existing aviation technical standards are all constrained from the angle of single electric equipment, and a constraint method with explicit compatibility is not provided; on the other hand, the aviation technical standards cannot limit the power compatible with electric equipment of the MEA variable-frequency alternating-current electric system under specific working conditions.
Disclosure of Invention
The invention provides a constraint method for the power boundary of an MEA variable-frequency alternating-current electric system compatible with a rectifying type load under any working condition based on quantitative analysis of electric energy quality, aiming at solving the problems in the prior art.
In order to achieve the above purpose, the technical scheme provided by the invention is as follows: a compatibility constraint method of an MEA variable frequency alternating current electric system comprises the following steps:
judging whether the harmonic current content of an input port of a rectification type load in the MEA variable-frequency alternating-current electric system meets the regulation of a limit value, and taking the rectification type load as the load of the MEA variable-frequency alternating-current electric system if the harmonic current content meets the regulation of the limit value; if the voltage is not satisfied, the rectifying type load is used as the load of the MEA variable-frequency alternating-current electric system after being provided with the filter device;
establishing an equivalent circuit of the MEA variable-frequency alternating-current electric system;
deducing an expression of each order harmonic voltage of the MEA variable-frequency alternating-current main bus according to the equivalent circuit; and solving the harmonic voltage order with the maximum weight coefficient;
obtaining the maximum value of the output current of the rectifying load DC side according to the maximum distortion frequency spectrum of the MEA variable-frequency alternating-current bus voltage;
and determining the maximum value of the output power of the rectification type load according to the maximum value of the output current.
The technical scheme is further designed as follows: the equivalent circuit is a mathematical model of each component in the MEA variable-frequency alternating-current electrical system under the dq coordinate system.
The weight coefficient lambda of the harmonic voltage is the effective value v of the harmonic voltage of a certain order h Boundary value v of harmonic voltage corresponding to maximum distortion frequency spectrum of variable frequency alternating current bus voltage at frequency b Is expressed as:
when the harmonic voltage with the largest weight coefficient meets the requirement of the maximum distortion frequency spectrum of the variable-frequency alternating-current bus voltage, the harmonic voltages of other orders must meet the requirement of the maximum distortion frequency spectrum of the variable-frequency alternating-current bus voltage. Therefore, the harmonic voltage with the largest weight coefficient can be used to constrain the power boundary of the commutating load.
The MEA variable-frequency alternating-current electric system comprises a power supply side and a load side; the power supply side is VFAC-TSG, and the load side is a rectifying type load.
The rectifying load is a 12-pulse transformer rectifier (Transformer Rectifier Unit, TRU) or an 18-pulse autotransformer rectifier (Auto Transformer Rectifier Unit, ATRU).
The internal potential v of the VFAC-TSG sdq The expression of (2) is:
wherein ω is the electrical angular velocity of the rotor of the main generator; l (L) md D-axis mutual inductance of the main generator; i.e f Is the field winding current (converted to a stator side value) of the main generator.
The VFAC-TSG output impedance Z sdq The expression of(s) is:
wherein R is s 、R f The main generator armature resistance and the exciting resistance are respectively; l (L) sd 、L sq The self inductance of the d-axis armature winding and the q-axis armature winding of the main generator are respectively; l (L) f The exciting winding self-inductance of the main generator.
The 18 pulse ATRU input impedance Z Ldq The expression of(s) is:
wherein,,
K v ＝[k v cosδ N k v sinδ N ]
wherein C is dc And R is L A DC output filter capacitance value and a load resistance value of 18 pulse ATRU respectively; phi is the angle at which the input current lags the input voltage; k (k) v And k i Respectively a voltage coefficient and a current coefficient; v mdN And v mqN Respectively obtaining steady-state values of d-axis voltage and q-axis voltage of the input port of the second group of rectifier bridges; i.e d2N And i q2N Respectively obtaining steady-state values of d-axis current and q-axis current of the input ports of the second group of rectifier bridges; delta N As voltage phasors
Steady state values of the clamping angle with the d-axis; k (k) 1 And k 2 Respectively corresponding turns ratios of primary and secondary sides.
Harmonic voltage v of MEA variable-frequency alternating-current main bus bush The expression of (2) is:
v bush ＝-Z sdq (jω h )i fdq
harmonic current i fdq The expression of (2) is:
i fdq ＝(Z sdq (jω h )+Z fdq (jω h )+Z Ldq (jω h )) -1 Z Ldq (jω h )i hdq 。
compared with the prior art, the invention has the following main advantages and remarkable effects:
1) The invention provides an MEA variable-frequency alternating-current electrical system compatibility constraint method based on technical indexes related to electric energy quality by depending on aviation technical standards. The method can quantitatively analyze the power boundary of the MEA variable-frequency alternating-current electric system compatible with any rectifying type load under a certain specific working condition, and provides reference and basis for actual engineering design.
2) According to the invention, through establishing an impedance model of each component in the MEA variable-frequency alternating-current electric system and analyzing the harmonic current characteristics of the input port of the rectifying load, the expression of the harmonic voltages of each order of the MEA variable-frequency alternating-current main bus is deduced. The amplitude of the harmonic voltage depends on the magnitude of the output current of the direct current side of the rectification type load, and the maximum distortion frequency spectrum of the variable-frequency alternating-current bus voltage is used as a criterion to restrict the maximum value of the amplitude of the harmonic voltage, so that the power boundary of the rectification type load is restricted. Compared with the prior aviation technology standard, the compatibility constraint method has deeper and more thorough constraint degree.
3) The core basis of the compatibility constraint method provided by the invention is an aviation technical standard, and the technical index limit value in the aviation technical standard is relied on as a constraint condition. Therefore, the rectification type load power boundary obtained by the method has stronger scientificity and referential property.
Drawings
Fig. 1 is a flow chart of the operation of the present invention.
Fig. 2 is a schematic diagram of the MEA variable frequency ac electrical system of the present invention.
Fig. 3 is a schematic structural view of an embodiment of the present invention.
Fig. 4 is a schematic diagram of the structure of an 18 pulse ATRU according to the present invention.
Fig. 5 shows the input port harmonic current characteristics of an 18-pulse ATRU according to the present invention.
Fig. 6 is an equivalent circuit in dq coordinate system according to an embodiment of the present invention.
Fig. 7 is a fundamental equivalent circuit in the dq coordinate system according to an embodiment of the present invention.
Fig. 8 is a harmonic equivalence circuit in dq coordinate system according to an embodiment of the present invention.
Fig. 9 is a bus voltage harmonic characteristic of an embodiment of the present invention.
Fig. 10 is a graph of the maximum distortion spectrum of the variable frequency ac busbar voltage in the present invention.
Detailed Description
The invention will now be described in detail with reference to the accompanying drawings and specific examples.
Examples
According to the compatibility constraint method of the MEA variable-frequency alternating-current electrical system based on the electric energy quality, the power boundary of the MEA variable-frequency alternating-current electrical system compatible with a rectifying type load under a specific working condition is quantitatively analyzed according to the harmonic current limit value of an input port of electric equipment and the maximum distortion frequency spectrum of the variable-frequency alternating-current bus voltage specified in the aviation technical standard by means of the aviation technical standard.
The electric energy quality refers to the harmonic wave of the MEA variable-frequency alternating-current main bus voltage and the harmonic wave of the electric equipment input port current;
the aviation technical standards include: before compatibility evaluation is carried out, the GJB-181B and DO-160G are required to compare and analyze the technical index limit values in two aviation technical standards, and extract key technical indexes for restricting the compatibility of the MEA variable-frequency alternating-current electric system; key technical indexes for restraining compatibility of the MEA variable-frequency alternating-current electric system comprise: the input port harmonic current limit value of the alternating current electric equipment specified by DO-160G aviation technology standard and the maximum distortion frequency spectrum of the variable frequency alternating current bus voltage specified by GJB-181B aviation technology standard.
The harmonic current limit value of the input port of the alternating current electric equipment provides a basis for the electric equipment to be connected into the MEA variable-frequency alternating current electric system, but the technical index cannot directly limit the power of the electric equipment; the maximum distortion frequency spectrum of the variable frequency alternating current bus voltage defines the boundary of the harmonic voltage amplitude of the variable frequency alternating current main bus of the MEA, and the constraint boundary of the harmonic voltage amplitude of any frequency of the variable frequency alternating current main bus of the MEA can be obtained according to the maximum distortion frequency spectrum. In addition, GJB-181B also prescribes that the total harmonic distortion (Total Harmonic Distortion, THD) of the voltage of the MEA variable-frequency alternating-current main bus is not more than 5%, and the current THD of the input port of single electric equipment is not more than 10%.
As shown in fig. 2, the MEA variable frequency ac electrical system is an independent power supply system mainly based on power electronic devices, and is divided into a power supply side and a load side from a variable frequency ac main bus. The power supply side is a VFAC-TSG and generator control unit (Generator Control Unit, GCU) for providing electric energy for the rear-end electric equipment; the load side is a rectifying load, the rectifying load is a 12-pulse TRU or an 18-pulse ATRU, the rectifying load is a main harmonic source in the MEA variable-frequency alternating-current electric system, harmonic current generated by the rectifying load can generate harmonic voltage drop on the output impedance of the VFAC-TSG, and the harmonic voltage drop is the harmonic voltage of an MEA variable-frequency alternating-current main bus.
Taking the VFAC-TSG cascade 18 pulse ATRU as an example, the power margin of the MEA variable frequency ac electrical system compatible with the 18 pulse ATRU is analyzed in this embodiment.
The schematic structural diagram of this embodiment is shown in fig. 3, and includes: VFAC-TSG and 18 pulse ATRU. Noteworthy are: the compatibility constraint method provided by the invention is suitable for analyzing any rectifying type load in the MEA variable-frequency alternating-current electrical system, and is not limited to the embodiment.
18 pulse ATRU input port a phase current i a The expression of (2) is:
wherein I is o The average value of the output current at the DC side of the 18 pulse ATRU.
As can be seen from the formula (1), the amplitude of each order harmonic current of the 18-pulse ATRU input port is dependent on the DC side output current I o Is of a size of (a) and (b).
The compatibility constraint method of the MEA variable frequency alternating current electric system of the embodiment is shown in fig. 1, and the specific flow is as follows:
comparing the harmonic current limit of the input port of the DO-160G AC powered device with that of equation (1) shown in Table 1, it is clear that the harmonic current content of the 18 pulse ATRU input port does not meet the specification of the DO-160G standard. Thus, it is necessary to configure an appropriate filter device so that the harmonic current content of its input port meets the specifications of the DO-160G standard.
Table 1DO-160G demand for harmonic currents of three-phase balanced consumers
Wherein I is 1 Is the effective value of fundamental current, h is the harmonic order, I h Is the effective value of the h-order harmonic current.
As shown in fig. 4, the 18-pulse ATRU ac input side is connected in series with a filter inductance L; DC output side parallel filter capacitor C dc . In this embodiment, the 18 pulse ATRU back end DC load is a resistor R L 。
As shown in fig. 5, the harmonic content of the 18 pulse ATRU input port current after the filter addition meets the specification of the DO-160G standard. Therefore, it can be connected to the MEA variable frequency ac electrical system.
As shown in fig. 6, an equivalent circuit in the dq coordinate system of the present embodiment is established. Wherein, the VFAC-TSG is equivalent to a direct-current voltage source v sdq Series output impedance Z sdq (s) the DC voltage source is the internal potential of the VFAC-TSG; the 18 pulse ATRU equivalent is a controlled current source i hdq Parallel input impedance Z Ldq (s) forms; z is Z fdq (s) is a filter inductance of an 18-pulse ATRU input port, and the controlled current source represents harmonic current of each order;
DC voltage source v sdq Is the internal potential of the VFAC-TSG, and the expression is:
wherein ω is the electrical angular velocity of the rotor of the main generator; l (L) md D-axis mutual inductance of the main generator; i.e f Is the field winding current (converted to a stator side value) of the main generator.
VFAC-TSG output impedance Z sdq The expression of(s) is:
wherein R is s 、R f The main generator armature resistance and the exciting resistance are respectively; l (L) sd 、L sq The self inductance of the d-axis armature winding and the q-axis armature winding of the main generator are respectively; l (L) f The exciting winding self-inductance of the main generator.
18 pulse ATRU input impedance Z Ldq The expression of(s) is:
wherein,,
K v ＝[k v cosδ N k v sinδ N ](5)
wherein C is dc And R is L A DC output filter capacitance value and a load resistance value of 18 pulse ATRU respectively; phi is the angle at which the input current lags the input voltage; k (k) v And k i Respectively a voltage coefficient and a current coefficient; v mdN And v mqN Respectively obtaining steady-state values of d-axis voltage and q-axis voltage of the input port of the second group of rectifier bridges; i.e d2N And i q2N Respectively obtaining steady-state values of d-axis current and q-axis current of the input ports of the second group of rectifier bridges; delta N As voltage phasors
Steady state values of the clamping angle with the d-axis; k (k) 1 And k 2 Respectively corresponding turns ratios of primary and secondary sides.
18 pulse ATRU input port filter inductor Z fdq The expression of(s) is:
wherein L is the filter inductance value of each phase.
According to FIG. 6, the MEA variable frequency AC main bus voltage v can be obtained bus The expression of (2) is:
wherein v is busn Is the fundamental voltage, v bush Is a harmonic voltage.
As shown in fig. 7 and 8, the equivalent circuit in the dq coordinate system of the present embodiment can be divided into two parts of a fundamental wave equivalent circuit and a harmonic equivalent circuit.
According to FIG. 7, the fundamental current i can be obtained sdq The expression of (2) is:
i sdq ＝(Z sdq (0)+Z fdq (0)+Z Ldq (0)) -1 v sdq (12)
the associated formula (2), the formula (3), the formula (4), the formula (10) and the formula (12) are substituted into the related parameters of the table 2 and the table 3, and then the a-phase fundamental wave current i under the abc static coordinate system can be obtained through the dq/abc park coordinate inverse transformation sa Is the primary phase of (a)
In the present embodiment, the a-phase fundamental current i is actually obtained sa Is>
TABLE 2 parameters of VFAC-TSG
Table 318 parameters of pulsed ATRU
According to the formula (1), and according to the phase relation between abc three-phase fundamental currents, the expression of 17 th harmonic current of the 18-pulse ATRU input port under the abc static coordinate system can be obtained as follows:
wherein,,
is the primary phase of a-phase fundamental wave current, I 17 An effective value of 17 th harmonic current of an 18-pulse ATRU input port is expressed as follows:
I 17 ≈0.05I o (14)
the expression of 17 th harmonic current of the 18-pulse ATRU input port under the dq coordinate system can be obtained by the abc/dq park coordinate transformation of the expression (13):
according to the formula (1), and according to the phase relation between abc three-phase fundamental wave currents, the expression of the 19 th harmonic current of the 18-pulse ATRU input port under the abc static coordinate system can be obtained as follows:
wherein I is 19 An effective value of the 19 th harmonic current of the 18 pulse ATRU input port is expressed as follows:
I 19 ≈0.045I o (17)
the expression of the 19 th harmonic current of the 18 pulse ATRU input port under the dq coordinate system can be obtained by the abc/dq park coordinate transformation of the expression (16):
from the equations (15) and (18), it is known that the 17 th harmonic current and the 19 th harmonic current in the abc stationary coordinate system are converted to 18 th harmonic currents in the dq coordinate system.
From FIG. 8, a harmonic current i can be obtained fdq The expression of (2) is:
i fdq ＝(Z sdq (jω h )+Z fdq (jω h )+Z Ldq (jω h )) -1 Z Ldq (jω h )i hdq (19)
at a known a-phase fundamental current i sa Is the primary phase of (a)
Based on the combination formula (3), the formula (4), the formula (10), the formula (15), the formula (18) and the formula (19), the 18 th harmonic current i flowing through the output impedance of the VFAC-TSG can be obtained f18 The expression of (2) is:
according to FIG. 8, the MEA variable frequency AC main bus harmonic voltage v can be obtained bush The expression of (2) is:
v bush ＝-Z sdq (jω h )i fdq (21)
substituting the formula (3) and the formula (20) into the formula (21) to obtain the voltage drop v of 18 times harmonic current on the VFAC-TSG output impedance bus18 The expression of (2) is:
and (3) performing dq/abc park coordinate inverse transformation on the formula (22), so as to obtain expressions of 17 th harmonic voltage and 19 th harmonic voltage under an abc static coordinate system, wherein the expressions are respectively as follows:
the derivation of the 35 th and 37 th harmonic voltage expressions is the same as above and will not be described in detail here. The expressions of the 35 th harmonic voltage and the 37 th harmonic voltage of the MEA variable-frequency alternating-current main bus under the abc static coordinate system are practically deduced as follows:
on the basis of deriving the expression of each order harmonic voltage of the MEA variable-frequency alternating-current main bus, the weight coefficient lambda of each order harmonic voltage needs to be further obtained. The weight coefficient of the harmonic voltage is the effective value v of the harmonic voltage of a certain order h Boundary value v of harmonic voltage corresponding to maximum distortion frequency spectrum of variable frequency alternating current bus voltage at frequency b Is expressed as:
it should be noted that: as can be seen from fig. 10, in the frequency range corresponding to each order harmonic voltage of the MEA variable frequency ac main bus, the upper limit value of the harmonic voltage amplitude decreases with increasing frequency. Therefore, in order to ensure that the amplitude of each order harmonic voltage of the MEA variable-frequency alternating-current main bus meets the requirement of the maximum distortion frequency spectrum of the variable-frequency alternating-current bus voltage in a wide variable-frequency range of 360-800Hz, the fundamental wave frequency of the VFAC-TSG should be set to 800Hz.
As can be seen from fig. 10, in the case where the fundamental frequency is 800Hz, the harmonic voltage boundary values of 17 times, 19 times, 35 times and 37 times in the maximum distortion spectrum of the variable frequency ac busbar voltage are respectively:
the weighting coefficients of the harmonic voltages of each order of the MEA variable-frequency alternating-current main bus can be obtained by the combination formula (23), the formula (24), the formula (25), the formula (26), the formula (27) and the formula (28) respectively are as follows:
as can be seen from the equation (29), the weighting coefficients of the four order harmonic voltages in the present embodiment are very close, and the weighting coefficient of the 19 order harmonic voltage is slightly higher than the weighting coefficients of the other order harmonic voltages. Therefore, 19 harmonic voltages are selected for constraining the MEA variable frequency ac electrical system from being compatible with the power boundary of 18 pulse ATRU.
The following constraint relationship may be established according to the second sub-formulae in formulae (24) and (28):
the maximum value I of the output current of the DC side of the 18 pulse ATRU can be obtained according to the formula (30) om About:
I om ≈63(A)(31)
under the working condition, 18 pulses of ATRU direct current side output voltage V o Is about 285V. Thus, the output maximum value P of the 18-pulse ATRU max About:
P max ≈V o I om ≈18(kW)(32)
from the above analysis, the maximum power margin of the MEA variable frequency ac electrical system compatible 18 pulse ATRU is about 18kW in this embodiment.
To verify the correctness of the theoretical analysis, a MATLAB/Simulink simulation model was built according to the structural diagram shown in fig. 3, and the power of the 18 pulse ATRU was set to 18kW, and the simulation parameters are shown in tables 2 and 3. The harmonic characteristics of the MEA variable frequency ac main bus voltage were analyzed by applying the FFT function, and the simulation result is shown in fig. 9.
As can be seen from fig. 9, the ratio of the effective value of the 19 th harmonic voltage to the effective value of the fundamental wave voltage in the MEA variable frequency ac main bus is 1.08%, and the fundamental wave effective value of the MEA variable frequency ac main bus voltage is about 114.2V. Therefore, the effective value of the 19 th harmonic voltage is about 1.23V, which is close to but less than the upper limit value 1.33V specified in the maximum distortion spectrum. The harmonic voltage amplitudes of the other orders are also close to the upper limit value specified in the maximum distortion spectrum. Therefore, under the working condition, the power of the compatible 18-pulse ATRU of the MEA variable-frequency alternating-current electric system is close to the upper limit value, and the correctness and the effectiveness of the compatibility constraint method provided by the invention are verified.
The technical scheme of the invention is not limited to the embodiment, and all technical schemes obtained by adopting equivalent substitution modes fall within the scope of the invention.
Claims (9)
1. A compatibility constraint method of an MEA variable frequency alternating current electric system is characterized by comprising the following steps of: the method comprises the following steps:
judging whether the harmonic current content of an input port of a rectification type load in the MEA variable-frequency alternating-current electric system meets the regulation of a limit value, and taking the rectification type load as the load of the MEA variable-frequency alternating-current electric system if the harmonic current content meets the regulation of the limit value; if the voltage is not satisfied, the rectifying type load is used as the load of the MEA variable-frequency alternating-current electric system after being provided with the filter device;
establishing an equivalent circuit of the MEA variable-frequency alternating-current electric system;
deducing an expression of each order harmonic voltage of the MEA variable-frequency alternating-current main bus according to the equivalent circuit; and solving the harmonic voltage order with the maximum weight coefficient;
obtaining the maximum value of the output current of the rectifying load DC side according to the maximum distortion frequency spectrum of the MEA variable-frequency alternating-current bus voltage;
and determining the maximum value of the output power of the rectification type load according to the maximum value of the output current.
2. The method of compatibility constraint of a MEA variable frequency ac electrical system of claim 1, wherein: the equivalent circuit is a mathematical model of each component in the MEA variable-frequency alternating-current electrical system under the dq coordinate system.
3. The method of compatibility constraint of a MEA variable frequency ac electrical system of claim 2, wherein: the weight coefficient lambda of the harmonic voltage is the ratio of the effective value vh of the harmonic voltage of a certain order to the corresponding harmonic voltage boundary value vb in the maximum distortion frequency spectrum of the variable-frequency alternating-current bus voltage at the frequency of the harmonic voltage of the order.
4. The method of compatibility constraint of a MEA variable frequency ac electrical system of claim 1, wherein: the MEA variable-frequency alternating-current electric system comprises a power supply side and a load side; the power supply side is a variable-frequency alternating-current three-stage generator, and the load side is a rectifying load.
5. The method of compatibility constraint of a MEA variable frequency ac electrical system of claim 4 wherein: the rectified load is a 12 pulse TRU or an 18 pulse ATRU.
6. The method of compatibility constraint of a MEA variable frequency ac electrical system of claim 5 wherein:
internal potential v of variable-frequency alternating-current three-stage generator sdq The expression of (2) is:
wherein ω is the electrical angular velocity of the rotor of the main generator; l (L) md D-axis mutual inductance of the main generator; i.e f Is the field winding current (converted to a stator side value) of the main generator.
7. The method of compatibility constraint of a MEA variable frequency ac electrical system of claim 6 wherein:
output impedance Z of variable-frequency alternating-current three-stage generator sdq The expression of(s) is:
wherein R is s 、R f The main generator armature resistance and the exciting resistance are respectively; l (L) sd 、L sq The self inductance of the d-axis armature winding and the q-axis armature winding of the main generator are respectively; l (L) f The exciting winding self-inductance of the main generator.
8. The method of compatibility constraint of a MEA variable frequency ac electrical system of claim 7 wherein:
the 18 pulse ATRU input impedance Z Ldq The expression of(s) is:
wherein,,
K v ＝[k v cosδ N k v sinδ N ]
wherein C is dc And R is L A DC output filter capacitance value and a load resistance value of 18 pulse ATRU respectively; phi is the angle at which the input current lags the input voltage; k (k) v And k i Respectively a voltage coefficient and a current coefficient; v mdN And v mqN Respectively obtaining steady-state values of d-axis voltage and q-axis voltage of the input port of the second group of rectifier bridges; i.e d2N And i q2N Respectively obtaining steady-state values of d-axis current and q-axis current of the input ports of the second group of rectifier bridges; delta N As voltage phasors
Steady state values of the clamping angle with the d-axis; k (k) 1 And k 2 Respectively corresponding turns ratios of primary and secondary sides.
9. The method of compatibility constraint of a MEA variable frequency ac electrical system of claim 8 wherein: harmonic voltage v of MEA variable-frequency alternating-current main bus bush The expression of (2) is:
v bush ＝-Z sdq (jω h )i fdq
harmonic current i fdq The expression of (2) is:
i fdq ＝(Z sdq (jω h )+Z fdq (jω h )+Z Ldq (jω h )) -1 Z Ldq (jω h )i hdq ；
wherein: z is Z fdq Filter inductance for 18 pulse ATRU input port, i hdq Is a controlled current source.
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