CN116094380A - Improved model predictive control method suitable for high-speed train traction converter - Google Patents
Improved model predictive control method suitable for high-speed train traction converter 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
- H02P21/00—Arrangements or methods for the control of electric machines by vector control, e.g. by control of field orientation
- H02P21/0003—Control strategies in general, e.g. linear type, e.g. P, PI, PID, using robust control
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M5/4585—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only having a rectifier with controlled elements
Abstract
The invention discloses an improved model predictive control method suitable for a high-speed train traction converter, which specifically comprises the following steps: sampling the secondary side voltage of the traction transformer to obtain amplitude and phase information of the secondary side voltage; sampling the actual rotating speed and the inversion side current of the traction motor, and calculating to obtain a dq axis reference voltage vector and a dq axis reference current vector; estimating bus current according to the inversion side reference voltage vector, the current vector and the bus voltage; solving a rectifying side current command value according to the DC bus current estimated value and the bus voltage error; meanwhile, the direct current bus current item is added with integral compensation, so that an integral compensation item based on direct current bus current feedforward is formed; and a dead beat prediction control method is adopted to realize accurate control of the current at the rectifying side. According to the invention, the direct current bus current is estimated under the condition that no additional sensor is added, the response speed of the direct current bus voltage of the rectifier is improved, the voltage overshoot in the response process is reduced, and the integral improvement of the output performance of the rectifier is realized.
Description
Technical Field
The invention belongs to the field of converter control systems in the fields of power electronics and electric transmission, and particularly relates to an improved model predictive control method suitable for a high-speed train traction converter.
Background
The electrified railway has the advantages of large carrying capacity, high speed, small pollution, low operation cost and the like, and the investment construction of the electrified railway is highly valued and strongly supported by the nation for a long time. The power core of the electrified railway is an electric traction transmission system, and the 'AC-DC-AC' type electric traction transmission system becomes the main flow transmission mode of the electrified railway at present, wherein a traction converter is used as a front-stage power supply device of a traction motor, and the traction and braking performance of the motor are directly influenced by the response process and the quality of electric energy output.
Train operation involves frequent switching of multiple conditions, such as traction, regenerative braking, coasting, etc. For the rectifying link, these operating mode switches often appear as a continuous change in the rectifying output from no load to full load. For inverters and traction motors, the rectifier performance is mainly represented by a continuous, stable dc bus voltage output that can quickly ramp back up/down to a given voltage when load switching occurs. When the rectifying output is switched from no-load to full-load, the voltage of the direct current bus is dropped, and the input of the voltage ring controller is increased at the moment so that the current ring command value is increased. The increase of the current loop command value causes the current loop to regulate the network side input current to increase the network side input power, and the result is necessarily that the output power is increased, the direct current bus voltage is recovered and the voltage is raised due to the conservation of the rectified input power and the output power. Similarly, the dc bus voltage will spike positively when the commutation output switches from full to no load, and will directly cause continuous positive/negative spikes in the dc bus voltage when the motor conditions are frequently switched, as shown in fig. 1. If the dc bus voltage response is slow, the output performance of the traction motor may be affected, and a longer response process may also induce LC resonance. For many years, students continuously propose a control method of the current loop, so that the response speed of the current loop is greatly improved. However, the response process of the rectified output power is a process of interaction and action of the current loop and the voltage loop, and even if the current loop speed is high, the whole response process is still greatly limited by the voltage loop.
At present, the development of a new generation high-speed motor train unit with rapid track traffic development and 400 km per hour is also scheduled, and the higher speed enables the traction motor to provide higher performance requirements for the converter, and the voltage loop control method for quickly and smoothly recovering the DC bus voltage is a necessary guarantee for the traction motor to exert excellent performance. Therefore, the research of the method for quickly recovering and controlling the voltage of the direct current bus in the rectification link of the traction transmission system of the high-speed train is significant.
Disclosure of Invention
In order to improve the response speed of the voltage ring when the direct current bus voltage fluctuates due to abrupt change of the rotating speed or load of the traction motor, and smooth higher voltage overshoot in the response process. The invention provides an improved model predictive control method suitable for a high-speed train traction converter.
The invention discloses an improved model predictive control method suitable for a high-speed train traction converter, which comprises the following steps of:
step 1: sampling the secondary side voltage of the traction transformer to obtain the amplitude U s And phase information ωt.
Step 2: sampling the actual rotation speed n of the traction motor k And the inversion side current
Calculating to obtain dq axis reference voltage vector +.>
And current vector->
Step 3: estimating bus current from the inverter side reference voltage vector, the current vector and the bus voltage
Step 4: based on DC bus current estimation
Solving a rectifying side current command value with a bus voltage error +.>
Meanwhile, in order to eliminate steady-state errors, an integral compensation is added to the direct current bus current item, so that an integral compensation item based on direct current bus current feedforward is formed.
Step 5: and a dead beat prediction control method is adopted to realize accurate control of the current at the rectifying side.
Further, the step 3 specifically includes:
the inverter-side reference voltage vector is obtained by a motor control system, and the inverter output current vector is obtained by sampling by an intrinsic sensor and performing Park conversion, so that the direct current bus current is as follows:
wherein ,
and />
Is the d-axis component of the inversion side reference voltage, current vector,>
and />
Is the q-axis of the inversion side reference voltage and current vectorA component; />
The dc bus voltage at time k.
Further, the step 4 specifically includes:
to control period T s The bus voltage is discretized in units, and the direct current bus voltage at the time k+1 is expressed as;
wherein ,
for the current command value, C d The capacitance value is supported for the DC side.
The rectifying side voltage loop evaluation function is designed as
wherein ,udcr Is a direct current bus voltage reference value.
In order to realize accurate tracking of the voltage of the direct current bus, an error integral compensation term of the bus voltage is added to the direct current bus current, so that an integral compensation term based on direct current bus current feedforward is formed, namely, a rectifying side current instruction value is as follows:
wherein ,fs For switching frequency, i.e. switching period T s Is the reciprocal of (2); λ is a weight coefficient used to balance the importance of the two indices to the right of the equation, here taken to be 0.06.
Compared with the prior art, the invention has the beneficial technical effects that:
1) The model predictive control method is improved, and the improved model predictive control is applied to the rectifying side voltage loop in a load current feedforward mode, so that the regulating speed of the direct current bus voltage is improved, and the overshoot of the recovery voltage in the regulating process is reduced.
2) The rectifying side direct current bus current estimation method is designed, and therefore accurate extraction of direct current bus current is achieved under the condition that a sensor is not additionally arranged.
3) The error compensation is carried out on the feedforward value of the rectifying bus current by using an integrator, the open loop gain of the rectifying side voltage ring is improved, and the accurate tracking of the direct current bus voltage is realized.
Drawings
Fig. 1 shows positive and negative voltage spikes on a dc bus during load switching.
Fig. 2 is a topology diagram of a traction converter.
Fig. 3 is a flow chart of a control method implementation.
Fig. 4 is a steady-state waveform of dc bus voltage.
Fig. 5 is a graph comparing the full load and no load control effect of the converter output (wherein a uses the method of the present invention and b uses conventional PI).
Fig. 6 is a graph comparing the control effect of the converter output no-load cut-full load (wherein a uses the method of the present invention and b uses the conventional PI).
Fig. 7 is a graph comparing the control effect of the converter output half-load cut-off load (wherein a uses the method of the present invention and b uses the conventional PI).
Fig. 8 is a graph comparing the control effect of the converter output no-load half-load switching (wherein a uses the method of the present invention and b uses the conventional PI).
Detailed Description
The invention will be described in further detail with reference to the drawings and the detailed description.
The invention takes a three-phase two-level traction converter as a research object, and the topology of the three-phase two-level traction converter is shown in figure 2.
The invention discloses an improved model predictive control method suitable for a high-speed train traction converter, and the implementation flow is shown in figure 3. The method comprises the following steps:
step 1: sampling the secondary side voltage of the traction transformer to obtain the amplitude U s Phase(s)Bit information ωt;
step 2: sampling the actual rotation speed n of the traction motor k And the inversion side current
Calculating to obtain dq axis reference voltage vector +.>
And current vector->
The permanent magnet synchronous motor adopts d-axis current i od Control mode=0, so d-axis reference current +.>
Is 0, q-axis reference current +.>
Available from the speed outer loop PI controller, specifically:
the digital model of the dq axis of the permanent magnet synchronous motor is as follows:
wherein ,uod 、u oq Is the dq axis voltage reference value; l (L) d 、L q Is a stator inductance; r is stator resistance; omega e For rotor electrical angular velocity; psi phi type f Is a permanent magnet flux linkage.
With a sampling period T s Discretizing the above as a reference, the inversion side dq current at the time (k+1) can be obtained as follows:
from the dead beat control concept, it is known that in an ideal case the actual current should follow the given current in the next cycle. The inversion-side reference voltage vector can be thus found as:
so far, both the reference voltage vector and the output current vector required for dc bus current estimation are known.
Step 3: estimating a bus current i from the inverter side reference voltage vector, the current vector and the bus voltage k d c . In a traction transmission system of a rail train, the direct current bus current can be estimated through an inversion side reference voltage vector and an output current vector without additionally adding a sensor. The inverter-side reference voltage vector can be obtained by a motor control system, and the inverter output current vector can be obtained by sampling and converting an intrinsic sensor.
Therefore, the dc bus current estimate is:
step 4: based on DC bus current estimation
Solving a rectifying side current command value with a bus voltage error +.>
Meanwhile, in order to eliminate steady-state errors, an integral compensation is added to the direct current bus current item, so that an integral compensation item based on direct current bus current feedforward is formed. For ease of analysis, the traction transformer is approximately seen as a voltage source in series with an inductor, as shown in fig. 2, with negligible internal resistance. u (u) s and is Representing the secondary side grid voltage and line current of the traction transformer, respectively; l (L) s Is of traction transformer or the likeEffective inductance u ab Is the rectifying side input voltage; u (u) dc Is the DC bus voltage; s is S 1 -S 4 An Insulated Gate Bipolar Transistor (IGBT) module that is a rectifying side anti-parallel diode.
Defining a rectifying side u s ，i s and uab The following are listed below
wherein ,usd 、u sq 、i sd 、i sq 、u abd 、u abq The dq-axis components of the grid voltage, line current and rectifying side input voltage vector, respectively.
For the input current in the network side boost inductor and the direct current bus voltage at two sides of the supporting capacitor, the differential equation can be obtained by applying kirchhoff's law
wherein ,uab For rectifying side input voltage, m is rectifying side modulation function, i dc Is a direct current bus current.
The dq axis dynamic model of the rectifying side can be obtained by simultaneous up-type
In the pulse rectifier, the output voltage thereof inevitably contains ripple waves 2 times as large as the power frequency (i.e., 100 Hz) due to the power frequency characteristics of the network side voltage and the input current, as shown in fig. 4. The ripple wave is multiplied by the sine component of the network side voltage after the voltage loop is contracted/amplified and regulated and enters the current loop, so that a large number of 150Hz harmonic waves are generated, and serious interference is caused to the current loop. Thus, a simple first order low pass filter is designed to reduce the interference of 100Hz ripple on the current loop. Namely, the DC bus voltage at the moment k is
wherein ,
for sampling value of DC bus voltage at k moment omega c For cut-off frequency, ω is usually taken for better filtering effect c ＝25。
Similarly, the rectifying side voltage loop evaluation function is designed as:
in order to obtain accurate tracking of the rectifying side voltage ring, an integral compensation link can be added to the direct current bus current, namely the rectifying side current ring command value is
Step 5: and a dead beat prediction control method is adopted to realize accurate control of the current at the rectifying side. To sinusoidal the net side input current and provide fast dynamic performance, dead beat predictive control can be applied to the rectifying side current loop. To control period T s The input current is discretized in units, and then a dynamic model of discrete time is:
in order to realize accurate tracking of the input current and the command value at the rectifying side, the input current and the command value should have minimum error after one control period, namely the evaluation function is
Further, the rectifying-side optimal input voltage vector can be expressed as in dq coordinate system
The optimal modulation function at the rectifying side is
wherein ,
ωt is the angular velocity of the network side voltage and can be obtained by a phase locked loop. After the calculation of the optimal modulation function is completed, the duty ratio of each switching tube can be distributed according to the principle of space vector modulation.
Fig. 5-8 are graphs comparing control effects when the converter load suddenly changes, and fig. 5 (b) uses conventional PI control, where the dc bus voltage overshoots about 13V and the settling time is about 290ms when the converter load switches from full to no load. While fig. 5 (a) uses the improved model predictive control method, the dc bus voltage overshoots about 8V when switching from full to no load, with a dynamic response time of about 40ms. In fig. 6 (b), the entire response process using the dc bus voltage of the conventional PI control requires about 190ms when switching from no load to full load. The dc bus voltage under the improved model predictive control, as shown in fig. 6 (a), has a relatively fast response speed, about 80ms. Also, fig. 7 (a), (b) and fig. 8 (a), (b) show that the control effect of the improved model predictive control method is superior to that of the conventional PI control method when the load is switched between no load and half load.
Claims (3)
1. An improved model predictive control method suitable for a high-speed train traction converter is characterized by comprising the following steps:
step 1: sampling the secondary side voltage of the traction transformer to obtain the amplitude U s Phase information ωt;
step 2: sampling the actual rotation speed n of the traction motor k And the inversion side current
Calculating to obtain dq axis reference voltage vector +.>
And current vector->
Step 3: estimating bus current from the inverter side reference voltage vector, the current vector and the bus voltage
Step 4: based on DC bus current estimation
Solving a rectifying side current command value with a bus voltage error +.>
Meanwhile, in order to eliminate steady-state errors, an integral compensation is added to a direct current bus current item, so that an integral compensation item based on direct current bus current feedforward is formed;
step 5: and a dead beat prediction control method is adopted to realize accurate control of the current at the rectifying side.
2. The improved model predictive control method for a high speed train traction converter according to claim 1, wherein the step 3 is specifically:
the inverter-side reference voltage vector is obtained by a motor control system, and the inverter output current vector is obtained by sampling by an intrinsic sensor and performing Park conversion, so that the direct current bus current is as follows:
wherein ,
and />
Is the d-axis component of the inversion side reference voltage, current vector,>
and />
Is the q-axis component of the inverter side reference voltage, current vector; />
The dc bus voltage at time k.
3. The improved model predictive control method for a high speed train traction converter according to claim 2, wherein said step 4 is specifically:
to control period T s The bus voltage is discretized in units, and the direct current bus voltage at the time k+1 is expressed as;
wherein ,
for the current command value, C d The capacitor value is supported for the direct current side;
the rectifying side voltage loop evaluation function is designed as follows:
wherein ,udcr Is a direct current bus voltage reference value;
in order to realize accurate tracking of the voltage of the direct current bus, an error integral compensation term of the bus voltage is added to the direct current bus current, so that an integral compensation term based on direct current bus current feedforward is formed, namely, a rectifying side current instruction value is as follows:
wherein ,fs For switching frequency, i.e. switching period T s Is the reciprocal of (2); λ is a weight coefficient used to balance the importance of the two indices to the right of the equation, here taken to be 0.06.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116633221A (en) * | 2023-07-24 | 2023-08-22 | 南京理工大学 | Minimum voltage vector error control method based on control quantity compensation |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116633221A (en) * | 2023-07-24 | 2023-08-22 | 南京理工大学 | Minimum voltage vector error control method based on control quantity compensation |
| CN116633221B (en) * | 2023-07-24 | 2023-10-31 | 南京理工大学 | Minimum voltage vector error control method based on control quantity compensation |
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