CN215221731U - Fault-tolerant APF device based on model predictive control - Google Patents

Fault-tolerant APF device based on model predictive control Download PDF

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CN215221731U
CN215221731U CN202121479854.4U CN202121479854U CN215221731U CN 215221731 U CN215221731 U CN 215221731U CN 202121479854 U CN202121479854 U CN 202121479854U CN 215221731 U CN215221731 U CN 215221731U
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apf
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杨光露
宋俊奇
孙轶峰
王文辉
邱宗鹤
牛启帆
索粮
王柱
窦智峰
李琰琰
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China Tobacco Henan Industrial Co Ltd
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    • Y02E40/20—Active power filtering [APF]

Abstract

The utility model provides a fault-tolerant APF device based on model predictive control, include: the model prediction device comprises an APF main circuit, an acquisition module, a model prediction controller and a bidirectional thyristor module. The bidirectional thyristor module is connected in series between the load output end of the APF main circuit and the midpoint of the direct-current side capacitor, and the control end of the bidirectional thyristor module is connected with the output end of the model predictive controller. The output end of the acquisition module is connected with the input end of the model prediction controller, and the acquisition module is used for acquiring the voltage and the load current of the power grid. The model prediction controller determines three-phase harmonic current output by the APF according to the power grid voltage and the load current, and controls the bidirectional thyristor module to be conducted when the three-phase harmonic current is smaller than a set threshold value, so that the APF main circuit is converted into a three-phase four-switch structure through a three-phase six-switch structure to output harmonic current outwards. The utility model discloses can improve APF operating efficiency, reduce the use cost of equipment.

Description

Fault-tolerant APF device based on model predictive control
Technical Field
The utility model relates to an active filter's technical field, concretely relates to fault-tolerant APF device based on model predictive control.
Background
With the development of industrial technology, power electronic equipment represented by a frequency converter is widely used for cigarette production. However, the use of power electronic equipment increases nonlinear loads in the power grid, and generates a large amount of harmonics. A large amount of harmonic waves are injected into a power grid, so that the voltage and current waveforms of the power grid are distorted, the power quality is increasingly deteriorated, and meanwhile, the service life of equipment in a cigarette factory is shortened, and even abnormal power failure and equipment interruption accidents are caused. In order to eliminate the negative effects of harmonics, Active Power Filters (APF) are receiving great attention. The APF is a widely used device capable of effectively suppressing harmonics, and is a device for actively compensating harmonics, unlike a passive filter. During the course of APF compensating harmonics, the switching devices are susceptible to temperature, humidity, excessive voltage, current and switching frequency resulting in failure. However, the conventional APF apparatus does not have a function of fault-tolerant operation, and once a switching device fails, the harmonic compensation effect of the APF is seriously affected, and a large amount of harmonics are injected into a power distribution system, thereby deteriorating the quality of electric energy. Therefore, how to improve the fault tolerance of the APF has important significance.
SUMMERY OF THE UTILITY MODEL
The utility model provides a fault-tolerant APF device based on model predictive control, the problem that fault-tolerant ability is low when the IGBT of solving current APF takes place the switch failure can improve APF operating efficiency, reduces the use cost of equipment.
In order to achieve the above object, the utility model provides a following technical scheme:
a model predictive control-based fault-tolerant APF device, comprising: the model prediction controller comprises an APF main circuit, an acquisition module, a model prediction controller and a bidirectional thyristor module;
the bidirectional thyristor module is connected between the load output end of the APF main circuit and the midpoint of the direct-current side capacitor in series, and the control end of the bidirectional thyristor module is connected with the output end of the model prediction controller;
the output end of the acquisition module is connected with the input end of the model prediction controller, and the acquisition module is used for acquiring the voltage and the load current of a power grid;
the model prediction controller determines three-phase harmonic current output by the APF according to the power grid voltage and the load current, and controls the bidirectional thyristor module to be conducted when the three-phase harmonic current is smaller than a set threshold value, so that the APF main circuit is converted into a three-phase four-switch structure through a three-phase six-switch structure to output harmonic current outwards.
Preferably, the method further comprises the following steps: a fuse;
and one fuse is arranged among the A-phase output end, the B-phase output end and the C-phase output end of the APF main circuit and the corresponding bridge arm.
Preferably, the bidirectional thyristor module consists of three bidirectional thyristors;
and one bidirectional thyristor is arranged between each phase of bridge arm in the APF main circuit and the midpoint of the direct-current side capacitor.
Preferably, the method further comprises the following steps: a filtering module;
and the output end of the APF main circuit is provided with a filtering module which is used for filtering and rectifying the harmonic current output by the APF main circuit.
Preferably, the filtering module includes: a filter inductor and a protection resistor;
and the A-phase output end, the B-phase output end and the C-phase output end in the APF main circuit are connected with the filter inductor and the protection resistor in series.
Preferably, the APF main circuit includes: a first switch tube V1, a second switch tube V2, a third switch tube V3, a fourth switch tube V4, a fifth switch tube V5, a sixth switch tube V6, a first direct current voltage dividing capacitor C1 and a second direct current voltage dividing capacitor C2;
an emitter of the first switching tube V1 is connected with a collector of the second switching tube V2 to form an A phase, an emitter of the third switching tube V3 is connected with a collector of the fourth switching tube V4 to form a B phase, and an emitter of the fifth switching tube V5 is connected with a collector of the sixth switching tube V6 to form a C phase;
the collectors of the first switching tube V1, the third switching tube V3 and the fifth switching tube V5 are connected to the first dc voltage divider capacitor C1;
the emitters of the second switching tube V2, the fourth switching tube V4 and the sixth switching tube V6 are connected to the second dc voltage-dividing capacitor C2;
the first direct-current voltage-dividing capacitor C1 and the second direct-current voltage-dividing capacitor C2 are connected in series and then connected in parallel with a direct-current power supply, and the connection midpoint of the first direct-current voltage-dividing capacitor C1 and the second direct-current voltage-dividing capacitor C2 is used as the midpoint of the direct-current side capacitors.
Preferably, the acquisition module comprises: the device comprises a voltage detection module and a current detection module;
the voltage detection module is used for detecting the power grid voltage of the power supply power grid, and the current detection module is used for detecting the three-phase current and the three-phase load current of the power supply power grid;
and the model prediction controller is used for converting the power grid voltage, the three-phase current and the three-phase load current to obtain a predicted current, and judging whether the APF main circuit has a phase current output fault or not according to the predicted current.
Preferably, the model predictive controller includes: microprocessor chip and drive module.
Preferably, the micro-processing chip is a DSP chip of TMS320F28335 type.
Preferably, the driving module adopts a driving chip of HCNW 4502.
The utility model provides a fault-tolerant APF device based on model predictive control detects grid voltage and load current by gathering the mould to be based on model predictive control ware basis grid voltage with the three-phase harmonic current of APF output is confirmed to load current, and three-phase harmonic current is less than and controls when setting for the threshold value the bidirectional thyristor module switches on, makes APF main circuit converts three-phase four switch structure to three-phase four switch structure by six switch structures and exports harmonic current outward. The problem of the fault-tolerant ability is low when the IGBT of current APF takes place the switch trouble is solved, APF operating efficiency can be improved, the use cost of equipment is reduced.
Drawings
In order to more clearly illustrate the specific embodiments of the present invention, the drawings used in the embodiments will be briefly described below.
Fig. 1 is a schematic diagram of a fault-tolerant APF device based on model predictive control.
Fig. 2 is a schematic diagram of an APF device with a three-phase six-switch structure according to the present invention.
Fig. 3 is a schematic diagram of an APF device with a three-phase four-switch structure according to the present invention.
Reference numerals
1. APF main circuit, 2 model predictive controller, 3 bidirectional controllable silicon module.
Detailed Description
In order to make those skilled in the art better understand the solution of the embodiments of the present invention, the embodiments of the present invention are further described in detail below with reference to the accompanying drawings and the implementation manner.
The problem that the fault-tolerant capability of the current active power filter is low when a switch fails is solved. The utility model provides a fault-tolerant APF device based on model predictive control detects grid voltage and load current by gathering the mould to be based on model predictive control ware basis grid voltage with the three-phase harmonic current of APF output is confirmed to load current, and three-phase harmonic current is less than and controls when setting for the threshold value the bidirectional thyristor module switches on, makes APF main circuit converts three-phase four switch structure to three-phase four switch structure by six switch structures and exports harmonic current outward. The problem of the fault-tolerant ability is low when the IGBT of current APF takes place the switch trouble is solved, APF operating efficiency can be improved, the use cost of equipment is reduced.
As shown in fig. 1 to 3, a fault-tolerant APF apparatus based on model predictive control includes: the model prediction device comprises an APF main circuit 1, an acquisition module, a model prediction controller 2 and a bidirectional thyristor module 3. The bidirectional thyristor module 3 is connected in series between the load output end of the APF main circuit 1 and the midpoint of the direct-current side capacitor, and the control end of the bidirectional thyristor module 3 is connected with the output end of the model predictive controller 2. The output end of the acquisition module is connected with the input end of the model prediction controller, and the acquisition module is used for acquiring the voltage and the load current of the power grid. The model prediction controller determines three-phase harmonic current output by the APF according to the power grid voltage and the load current, and controls the bidirectional thyristor module to be conducted when the three-phase harmonic current is smaller than a set threshold value, so that the APF main circuit is converted into a three-phase four-switch structure through a three-phase six-switch structure to output harmonic current outwards.
The introduction of the nonlinear load causes a large amount of harmonics in the grid current and the load current, and it is necessary to detect a harmonic component in the load current, and to generate a wave to the power electronic device by the model predictive controller, and to control the wave to compensate the harmonic component in the load current.
The device also includes: a fuse; and one fuse is arranged among the A-phase output end, the B-phase output end and the C-phase output end of the APF main circuit and the corresponding bridge arm. And when the A-phase bridge arm, the B-phase bridge arm or the C-phase bridge arm fails, the corresponding fuse is automatically disconnected.
Further, the bidirectional thyristor module consists of three bidirectional thyristors; and one bidirectional thyristor is arranged between each phase of bridge arm in the APF main circuit and the midpoint of the direct-current side capacitor.
In practical application, as shown in fig. 1, the device is characterized in that a fuse is connected in series between a three-phase load and a bridge arm, and a bidirectional thyristor is connected in parallel between the rear end of the fuse and the midpoint of a direct-current side capacitor, through the design, the structure can be reconstructed into a new three-phase four-switch structure after a switch device fails, as shown in fig. 3, and the proposed fault-tolerant operation of the APF is realized through model predictive control.
The device also includes: a filtering module; and the output end of the APF main circuit is provided with a filtering module which is used for filtering and rectifying the harmonic current output by the APF main circuit.
Further, the filtering module includes: a filter inductor and a protection resistor; and the A-phase output end, the B-phase output end and the C-phase output end in the APF main circuit are connected with the filter inductor and the protection resistor in series.
As shown in fig. 1, the APF main circuit 1 includes: the voltage-dividing circuit comprises a first switch tube V1, a second switch tube V2, a third switch tube V3, a fourth switch tube V4, a fifth switch tube V5, a sixth switch tube V6, a first direct-current voltage-dividing capacitor C1 and a second direct-current voltage-dividing capacitor C2. An emitter of the first switching tube V1 is connected with a collector of the second switching tube V2 to form a phase a, an emitter of the third switching tube V3 is connected with a collector of the fourth switching tube V4 to form a phase B, and an emitter of the fifth switching tube V5 is connected with a collector of the sixth switching tube V6 to form a phase C. The collectors of the first switching tube V1, the third switching tube V3, and the fifth switching tube V5 are connected to the first dc voltage divider capacitor C1. The emitters of the second switching tube V2, the fourth switching tube V4 and the sixth switching tube V6 are connected to the second dc voltage-dividing capacitor C2. The first direct-current voltage-dividing capacitor C1 and the second direct-current voltage-dividing capacitor C2 are connected in series and then connected in parallel with a direct-current power supply, and the connection midpoint of the first direct-current voltage-dividing capacitor C1 and the second direct-current voltage-dividing capacitor C2 is used as the midpoint of the direct-current side capacitors.
The acquisition module comprises: the device comprises a voltage detection module and a current detection module. The voltage detection module is used for detecting the power grid voltage of the power supply power grid, and the current detection module is used for detecting the three-phase current and the three-phase load current of the power supply power grid. And the model prediction controller is used for converting the power grid voltage, the three-phase current and the three-phase load current to obtain a predicted current, and judging whether the APF main circuit has a phase current output fault or not according to the predicted current.
Further, the model predictive controller includes: microprocessor chip and drive module.
Furthermore, the micro-processing chip adopts a DSP chip of a model TMS320F 28335.
Furthermore, the driving module adopts a driving chip of HCNW 4502.
In practical application, when an a-phase bridge arm fails, the voltage vector and the switching state of the fault-tolerant APF main circuit are as follows:
fast fuse F in A phase bridge armaIs rapidly disconnected, the A phase passes through the bidirectional thyristor TRaTo the dc side capacitor midpoint N as shown in fig. 2.
Wherein u isaNAssuming three-phase load balancing is available at 0V:
Figure BDA0003142481160000061
n represents the neutral point of the power grid, the phase voltage u of the converter output is obtainedan、ubnAnd ucnExpressed as:
Figure BDA0003142481160000062
Udc1and Udc2Are respectively a capacitor C1、C2The voltage value of (2) can be obtained as an expression of the voltage of the output line of the converter:
Figure BDA0003142481160000063
the output voltage expression of the fault-tolerant converter can be derived by substituting equation (4) for equation (3):
Figure BDA0003142481160000064
Figure BDA0003142481160000065
obtaining a voltage component u of a two-phase static coordinate system according to Clark transformation of formula (6)αAnd uβThe relationship with the switch state is shown in table 1.
TABLE 1 vector correspondence table of switching state and output voltage
Figure BDA0003142481160000066
Figure BDA0003142481160000071
The state equation of the fault-tolerant converter with the A-phase fault under an abc three-phase coordinate system can be obtained through kirchhoff's law:
Figure BDA0003142481160000072
in the formula uan、ubn、ucnRepresenting the three-phase voltages of the converter, ia、ib、icRespectively representing output three-phase currents, ea、eb、ecRespectively representing three-phase grid voltage values.
Clark conversion is carried out on the formula (7), and a state equation under an alpha beta two-phase stationary coordinate is derived:
Figure BDA0003142481160000073
in the formula:iα、iβ、uα、uβ、eα、eβrepresented as alpha and beta components of the converter output current, voltage and alternating voltage.
Discretizing equation (8) using the euler forward equation:
Figure BDA0003142481160000074
the predicted current output by the inverter from equation (9) can be:
Figure BDA0003142481160000075
t in formula (10)sIs the sampling period, tkThe output current, voltage and power grid voltage of the fault-tolerant converter are i respectively at the moment under an alpha beta two-phase static coordinate systemα(k)、iβ(k)、uα(k)、uβ(k)、eα(k)、eβ(k)，tk+1The predicted currents at the moment under an alpha beta axis coordinate system are i respectivelyα(k+1)、iβ(k+1)。
The fault-tolerant converter is a fault-tolerant structure after a two-level three-phase six-switch converter has a bridge arm fault, a fault bridge arm is replaced by a direct-current side electrolytic capacitor, a fault phase is directly connected to the midpoint of a direct-current side separation capacitor, and the fault-tolerant converter has the advantages of being simple in structure, low in cost, easy to achieve and the like. A three-phase four-switch structure is commonly used in the field of active filtering, and capacitance current on a direct current side of the three-phase four-switch structure flows into a fault phase through a capacitance neutral point, so that neutral point voltage on the direct current side is unbalanced, grid-connected current is distorted, and grid-connected electric energy quality is influenced. On the other hand, the capacitor voltage is higher than the rated value due to the unbalanced capacitor voltage, the service life of the electrolytic capacitor is shortened, and the secondary failure of the converter is further caused. In order to solve the problem, when the fault-tolerant converter is controlled, the capacitor voltage difference value is extracted and added into model prediction control, and the capacitor voltage deviation on the direct current side is eliminated.
The harmonic component of the load current calculated by the control module is used as a reference current, 4 whole voltage vectors of the fault-tolerant inverter can be traversed through the prediction process of the model prediction control method, the vector which enables the cost function g to be minimum is selected as the optimal switching state to be output, and the power electronic device can generate output current which is equal to the reference current as far as possible.
Equation (11) can be derived from current prediction equation (10) as follows:
Figure BDA0003142481160000081
the cost function g for predictive control of the design model is as follows:
g＝|irefa-iCa|+|irefb-iCb|+|irefc-iCc|+|ΔUdc| (12)
wherein iαβ，uαβ，eαβFor the grid current, the inverter output voltage and the alpha beta component, i, of the grid voltagerefFor three-phase reference currents, i.e. three-phase harmonic components, U, calculated by the control moduledc，TsAnd C, R and L are respectively direct current side voltage, a sampling period, a capacitor, a resistor and an inductance value.
Since the model predictive control does not use the cost function under the α β coordinate but uses the abc coordinate system, the fault-tolerant control of the fault-tolerant APF device can be realized by the cost function of the formula (12) despite the a-phase fault because the three-phase three-wire system APF has the relationship that the sum of the three-phase currents is 0.
It is visible, the utility model provides a fault-tolerant APF device based on model predictive control detects grid voltage and load current by gathering the mould to by model predictive control ware basis grid voltage with the three-phase harmonic current of APF output is confirmed to load current, and three-phase harmonic current is less than and controls when setting for the threshold value the bidirectional thyristor module switches on, makes APF main circuit converts the three-phase four switch structure to three-phase four switch structure by the six switch structures and exports harmonic current outward. The problem of the fault-tolerant ability is low when the IGBT of current APF takes place the switch trouble is solved, APF operating efficiency can be improved, the use cost of equipment is reduced.
The structure, features and effects of the present invention have been described in detail above according to the embodiment shown in the drawings, and the above description is only the preferred embodiment of the present invention, but the present invention is not limited to the implementation scope shown in the drawings, and all changes made according to the idea of the present invention or equivalent embodiments modified to the same changes should be considered within the protection scope of the present invention when not exceeding the spirit covered by the description and drawings.

Claims (10)

1. A fault-tolerant APF apparatus based on model predictive control, comprising: the model prediction controller comprises an APF main circuit, an acquisition module, a model prediction controller and a bidirectional thyristor module;
the bidirectional thyristor module is connected between the load output end of the APF main circuit and the midpoint of the direct-current side capacitor in series, and the control end of the bidirectional thyristor module is connected with the output end of the model prediction controller;
the output end of the acquisition module is connected with the input end of the model prediction controller, and the acquisition module is used for acquiring the voltage and the load current of a power grid;
the model prediction controller determines three-phase harmonic current output by the APF according to the power grid voltage and the load current, and controls the bidirectional thyristor module to be conducted when the three-phase harmonic current is smaller than a set threshold value, so that the APF main circuit is converted into a three-phase four-switch structure through a three-phase six-switch structure to output harmonic current outwards.
2. The model predictive control-based fault-tolerant APF device of claim 1, further comprising: a fuse;
and one fuse is arranged among the A-phase output end, the B-phase output end and the C-phase output end of the APF main circuit and the corresponding bridge arm.
3. The model predictive control-based fault-tolerant APF device of claim 2, wherein the triac module is comprised of three triacs;
and one bidirectional thyristor is arranged between each phase of bridge arm in the APF main circuit and the midpoint of the direct-current side capacitor.
4. The model-predictive-control-based fault-tolerant APF apparatus of claim 3, further comprising: a filtering module;
and the output end of the APF main circuit is provided with a filtering module which is used for filtering and rectifying the harmonic current output by the APF main circuit.
5. The model predictive control-based fault-tolerant APF apparatus of claim 4, wherein the filtering module comprises: a filter inductor and a protection resistor;
and the A-phase output end, the B-phase output end and the C-phase output end in the APF main circuit are connected with the filter inductor and the protection resistor in series.
6. The model predictive control-based fault-tolerant APF device of claim 5, wherein the APF master circuit comprises: a first switch tube V1, a second switch tube V2, a third switch tube V3, a fourth switch tube V4, a fifth switch tube V5, a sixth switch tube V6, a first direct current voltage dividing capacitor C1 and a second direct current voltage dividing capacitor C2;
an emitter of the first switching tube V1 is connected with a collector of the second switching tube V2 to form an A phase, an emitter of the third switching tube V3 is connected with a collector of the fourth switching tube V4 to form a B phase, and an emitter of the fifth switching tube V5 is connected with a collector of the sixth switching tube V6 to form a C phase;
the collectors of the first switching tube V1, the third switching tube V3 and the fifth switching tube V5 are connected to the first dc voltage divider capacitor C1;
the emitters of the second switching tube V2, the fourth switching tube V4 and the sixth switching tube V6 are connected to the second dc voltage-dividing capacitor C2;
the first direct-current voltage-dividing capacitor C1 and the second direct-current voltage-dividing capacitor C2 are connected in series and then connected in parallel with a direct-current power supply, and the connection midpoint of the first direct-current voltage-dividing capacitor C1 and the second direct-current voltage-dividing capacitor C2 is used as the midpoint of the direct-current side capacitors.
7. The model predictive control-based fault-tolerant APF apparatus of claim 6, wherein the acquisition module comprises: the device comprises a voltage detection module and a current detection module;
the voltage detection module is used for detecting the power grid voltage of the power supply power grid, and the current detection module is used for detecting the three-phase current and the three-phase load current of the power supply power grid;
and the model prediction controller is used for converting the power grid voltage, the three-phase current and the three-phase load current to obtain a predicted current, and judging whether the APF main circuit has a phase current output fault or not according to the predicted current.
8. The model-predictive-control-based fault-tolerant APF apparatus of any one of claims 1 to 7, wherein the model predictive controller comprises: microprocessor chip and drive module.
9. The model predictive control-based fault-tolerant APF device of claim 8, wherein the micro-processing chip is a DSP chip of model TMS320F 28335.
10. The model predictive control-based fault-tolerant APF device of claim 8, wherein the driver module employs a driver chip of HCNW 4502.
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