CN110971110A - Harmonic suppression control method for BT-AC converter - Google Patents
Harmonic suppression control method for BT-AC converter Download PDFInfo
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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
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Abstract
The invention discloses a harmonic suppression control method for a BT-AC converter, which is implemented according to the following steps: step 1, sampling the input voltage of a BT-AC converter through a voltage acquisition circuit to obtain an instantaneous value V of the input voltagein(t); step 2, instantaneous value V of input voltage in step 1in(t) inputting the voltage into an FIR digital filter, filtering out each harmonic to obtain the fundamental voltage instantaneous value V in the input voltage1(t); step 3, calculating Vd1(t): step 4, calculating Vd2(t): step 5, calculating Vd3(t): and 6, calculating a time-varying duty ratio C (t), and replacing the original duty ratio P of the converter with C (t) to participate in control. The harmonic suppression control method for the BT-AC converter is simple and reliable in control system and obvious in harmonic suppression effect.
Description
Technical Field
The invention belongs to the technical field of control of alternating current converters, and particularly relates to a harmonic suppression control method for a BT-AC converter.
Background
Today, with rapid development of economy, electrical loads are becoming more complex and diversified, and harmonic content in an electrical power system is increased due to strong nonlinear devices in power electronic equipment, start/stop of large loads in industrial production and transportation, unbalanced distribution of three-phase electrical loads and the like. Furthermore, with the large amount of distributed renewable energy sources accessing the grid, there are also not small challenges to the quality of the electrical energy. In order to obtain desired ac power or improve power quality, an ac-ac conversion circuit is often used to convert the power.
The Bipolar AC-AC Converter (BT-AC) is a direct AC-AC Converter, has a simple circuit structure and a simple modulation strategy, and has a wide output voltage range and no DC link. In addition, compared with the traditional AC-AC converter topology, the method has the advantages of easy realization of safe current conversion, continuous output current, high controllable degree of freedom and the like, and is suitable for various AC-AC conversion occasions.
In the conventional modulation mode of the BT-AC converter, the input voltage of the converter is assumed to be an ideal sine wave, and the condition that harmonic waves exist on the source side is ignored. Although this modulation method has the advantage of simple control, the harmonic in the input-side voltage when the converter operates in this modulation method causes the harmonic with the corresponding frequency to be included in the output of the converter, and the power quality on the load side is seriously affected.
Disclosure of Invention
The invention aims to provide a harmonic suppression control method for a BT-AC converter, which has a simple and reliable control system and a remarkable harmonic suppression effect.
The technical scheme adopted by the invention is that a harmonic suppression control method for a BT-AC converter is implemented according to the following steps:
Step 2, instantaneous value V of input voltage in step 1in(t) inputting the voltage into an FIR digital filter, filtering out each harmonic to obtain the fundamental voltage instantaneous value V in the input voltage1(t)；
Step 3, calculating V by adopting the following formulad1(t)：
Vd1(t)＝Vin(t)-V1(t) (1)
Step 4, calculating V by adopting the following formulad2(t)：
Step 5, calculating V by adopting the following formulad3(t)：
Vd3(t)＝PVd2(t) (3)
In the formula, P is the original duty ratio P of the BT-AC converter;
step 6, calculating a time-varying duty ratio C (t), and replacing the original duty ratio P of the converter with the C (t) to participate in control; the time-varying duty cycle c (t) is calculated as follows:
C(t)＝P-Vd3(t) (4)。
the invention is also characterized in that:
the topological structure of the BT-AC converter in the steps 5 and 6 is as follows:
one end of the input filter capacitor is connected with the anode of the single-phase alternating current input, and the other end of the input filter capacitor is connected with the cathode of the single-phase alternating current input; each bridge arm of the H bridge consists of 4 full-control power switch tubes and 1 clamping capacitor; one end of the positive and negative bridge arms is connected with the positive pole of the single-phase alternating current power supply, and the other end of the positive and negative bridge arms is connected with the negative pole; the positive and negative bridge arms have an output port to ground respectively, the two output ports form two-terminal output ports, and the voltages to ground of the positive and negative bridge arms are respectively VaAnd Vb。
The fully-controlled power switch tube of the positive-polarity bridge arm is S from top to bottom in sequence2、S1、S1c、S2c；S2Is connected with the positive electrode of the single-phase alternating current power supply, and the collector is connected with S1Is connected with the collector of the collector; s1Emitter and S1cCollector electrode connection of S1cEmitter and S2cThe emitter of (3) is connected; s2cThe collector of the single-phase alternating current power supply is connected with the negative electrode of the single-phase alternating current power supply; clamping capacitor C1One end and S1Is connected with the collector of the other end of the collector and S1cThe emitting electrodes are connected; the output end A of the positive bridge arm is composed of a switch tube S1Emitter and S1cIs led out between the collectors.
The full-control power switch tube of the negative bridge arm is S from top to bottom2p、S1p、S1cp、S2cp；S2pIs connected with the positive electrode of the single-phase alternating current power supply, and the collector is connected with S1pIs connected with the collector of the collector; s1pEmitter and S1cpIs connected with the collector of the collector; s1cpEmitter and S2cpThe emitter of (3) is connected; s2cpThe collector of the single-phase alternating current power supply is connected with the negative electrode of the single-phase alternating current power supply; clamping capacitor C2Clamped in the switching tube S1pCollector electrode of (1) and S1cpBetween the emitting electrodes, the output end B of the negative bridge arm is composed of a switch tube S1pEmitter and S1cpIs led out between the collectors.
The input end of the BT-AC converter is connected with a single-phase alternating current power supply, and the converter obtains 50Hz sine alternating current electric energy V from the power supplyinAfter being converted by the BT-AC converter, the electric energy is sent to the power supply LfAnd CfThe input end of the LC low-pass filter is filtered to obtain 50Hz sinusoidal alternating current to supply power to a load R.
The invention has the beneficial effects that:
(1) the harmonic suppression control method for the BT-AC converter solves the problem that the AC converter cannot deal with input voltage distortion under the traditional control, realizes the effective suppression of each subharmonic at the output side, and obviously improves the power quality of a load end;
(2) a harmonic suppression control method for a BT-AC converter introduces a time-varying harmonic optimization function aiming at the defect of constant duty ratio control so as to form an algorithm capable of coping with input voltage distortion; compared with the existing AC converter harmonic suppression method, the method does not need Fourier decomposition or phase-locked loop, greatly reduces the complexity of a calculation and control system, and improves the response speed of dealing with sudden distortion; in addition, the control system does not contain feedback quantity, and the whole system runs under an open-loop condition, so that the stability of the system is ensured;
(3) the harmonic suppression control method for the BT-AC converter adopts the FIR digital filter which has no feedback loop, runs stably, ensures accurate linear phase and has high precision, realizes high-performance filtering of digital signals, and can effectively reduce the volume and the cost of equipment by replacing an analog filter.
Drawings
FIG. 1 is a block flow diagram of a harmonic suppression control method for a BT-AC converter in accordance with the present invention;
FIG. 2 is a main circuit topology diagram of the BT-AC converter in the harmonic suppression control method for the BT-AC converter;
FIG. 3 is a graph of the input voltage waveform of the converter in the harmonic suppression control method for the BT-AC converter of the present invention;
FIG. 4 is a graph of the input voltage spectrum of the converter in the harmonic suppression control method for the BT-AC converter of the present invention;
FIG. 5 is a graph of the output voltage waveform of the converter in the harmonic suppression control method for the BT-AC converter of the present invention;
fig. 6 is a graph of the output voltage spectrum of the converter in the harmonic suppression control method for the BT-AC converter of the present invention.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1, the method for controlling harmonic suppression for a BT-AC converter according to the present invention is implemented by the following steps:
Step 2, instantaneous value V of input voltage in step 1in(t) inputting the voltage into an FIR digital filter, filtering out each harmonic to obtain the fundamental voltage instantaneous value V in the input voltage1(t)；
Step 3, calculating V by adopting the following formulad1(t)：
Vd1(t)＝Vin(t)-V1(t) (1)
Step 4, calculating V by adopting the following formulad2(t)：
Step 5, calculating V by adopting the following formulad3(t)：
Vd3(t)＝PVd2(t) (3)
In the formula, P is the original duty ratio P of the BT-AC converter;
step 6, calculating a time-varying duty ratio C (t), and replacing the original duty ratio P of the converter with the C (t) to participate in control; the time-varying duty cycle c (t) is calculated as follows:
C(t)＝P-Vd3(t) (4)。
as shown in fig. 2, the topology of the BT-AC converter is:
one end of the input filter capacitor is connected with the anode of the single-phase alternating current input, and the other end of the input filter capacitor is connected with the cathode of the single-phase alternating current input; each bridge arm of the H bridge consists of 4 full-control power switch tubes and 1 clamping capacitor; one end of the positive and negative bridge arms is connected with the positive pole of the single-phase alternating current power supply, and the other end of the positive and negative bridge arms is connected with the negative pole; the positive and negative bridge arms have an output port to ground respectively, the two output ports form two-terminal output ports, and the voltages to ground of the positive and negative bridge arms are respectively VaAnd Vb。
The fully-controlled power switch tube of the positive-polarity bridge arm is S from top to bottom in sequence2、S1、S1c、S2c；S2Emitter of (2) and positive electrode of single-phase alternating current power supplyConnecting the collector with S1Is connected with the collector of the collector; s1Emitter and S1cCollector electrode connection of S1cEmitter and S2cThe emitter of (3) is connected; s2cThe collector of the single-phase alternating current power supply is connected with the negative electrode of the single-phase alternating current power supply; clamping capacitor C1One end and S1Is connected with the collector of the other end of the collector and S1cThe emitting electrodes are connected; the output end A of the positive bridge arm is composed of a switch tube S1Emitter and S1cIs led out between the collectors.
The full-control power switch tube of the negative bridge arm is S from top to bottom2p、S1p、S1cp、S2cp；S2pIs connected with the positive electrode of the single-phase alternating current power supply, and the collector is connected with S1pIs connected with the collector of the collector; s1pEmitter and S1cpIs connected with the collector of the collector; s1cpEmitter and S2cpThe emitter of (3) is connected; s2cpThe collector of the single-phase alternating current power supply is connected with the negative electrode of the single-phase alternating current power supply; clamping capacitor C2Clamped in the switching tube S1pCollector electrode of (1) and S1cpBetween the emitting electrodes, the output end B of the negative bridge arm is composed of a switch tube S1pEmitter and S1cpIs led out between the collectors.
The input end of the BT-AC converter is connected with a single-phase alternating current power supply, and the converter obtains 50Hz sine alternating current electric energy V from the power supplyinAfter being converted by the BT-AC converter, the electric energy is sent to the power supply LfAnd CfThe input end of the LC low-pass filter is filtered to obtain 50Hz sinusoidal alternating current to supply power to a load R.
Firstly, the correctness and feasibility of the invention are verified through simulation
The adopted simulation software is PSIM; as shown in fig. 2, for the topology of the BT-AC converter, the specific parameters are set as follows: filter inductance Lf is 500uH, filter capacitance Cf is 20uF, and absorption capacitance C120uF, absorption capacitance C220uF, input capacitance CinThe switching frequency of IGBT is 20KHz, VinFor input voltage, the input voltage is set to contain fundamental wave and 3, 5, 7 and 9 harmonics, and the load is a resistor with the resistance of R being 12 ohms; simulation (Emulation)The results are shown in fig. 3, 4, 5 and 6.
FIG. 3 is a graph of an input voltage waveform with harmonics; FIG. 4 is a graph of an input voltage spectrum with harmonics; in the waveform of fig. 3, the horizontal axis represents time in seconds(s) and the vertical axis represents voltage amplitude in volts (v). It can be seen from fig. 3 that the input voltage has been severely distorted. The horizontal axis of the spectrum of fig. 4 is frequency in (Hz) and the vertical axis is voltage amplitude in volts (v). It can be seen from fig. 4 that 3, 5, 7, 9 th harmonics are present in the input voltage and are of large amplitude;
FIG. 5 is a graph of output voltage waveforms of the converter under the harmonic optimization control method; FIG. 6 is a graph of the output voltage spectrum of the converter using harmonic optimization control; in the waveform of fig. 5, the horizontal axis represents time in seconds(s) and the vertical axis represents voltage amplitude in volts (v). It can be seen from fig. 5 that the output voltage waveform has been well optimized. The horizontal axis of the spectrum of fig. 6 is frequency in (Hz) and the vertical axis is voltage amplitude in volts (v). It can be seen from fig. 6 that the amplitude of each harmonic in the output voltage is almost zero. By comparing fig. 3 and 5 with fig. 4 and 6, it can be seen that the low-order harmonic at the load end is well suppressed by using the harmonic optimization method, and the power quality improvement effect is outstanding.
The harmonic suppression control method for the BT-AC converter has the advantages that:
(1) the harmonic suppression control method for the BT-AC converter solves the problem that the AC converter cannot deal with input voltage distortion under the traditional control, realizes the effective suppression of each subharmonic at the output side, and obviously improves the power quality of a load end;
(2) a harmonic suppression control method for a BT-AC converter introduces a time-varying harmonic optimization function aiming at the defect of constant duty ratio control so as to form an algorithm capable of coping with input voltage distortion; compared with the existing AC converter harmonic suppression method, the method does not need Fourier decomposition or phase-locked loop, greatly reduces the complexity of a calculation and control system, and improves the response speed of dealing with sudden distortion; in addition, the control system does not contain feedback quantity, and the whole system runs under an open-loop condition, so that the stability of the system is ensured;
(3) the harmonic suppression control method for the BT-AC converter adopts the FIR digital filter which has no feedback loop, runs stably, ensures accurate linear phase and has high precision, realizes high-performance filtering of digital signals, and can effectively reduce the volume and the cost of equipment by replacing an analog filter.
Claims (5)
1. A harmonic suppression control method for a BT-AC converter is characterized by comprising the following steps:
step 1, sampling the input voltage of a BT-AC converter through a voltage acquisition circuit to obtain an instantaneous value V of the input voltagein(t)；
Step 2, instantaneous value V of input voltage in step 1in(t) inputting the voltage into an FIR digital filter, filtering out each harmonic to obtain the fundamental voltage instantaneous value V in the input voltage1(t)；
Step 3, calculating V by adopting the following formulad1(t)：
Vd1(t)＝Vin(t)-V1(t) (1)
Step 4, calculating V by adopting the following formulad2(t)：
Step 5, calculating V by adopting the following formulad3(t)：
Vd3(t)＝PVd2(t) (3)
In the formula, P is the original duty ratio P of the BT-AC converter;
step 6, calculating a time-varying duty ratio C (t), and replacing the original duty ratio P of the converter with the C (t) to participate in control; the time-varying duty cycle c (t) is calculated as follows:
C(t)＝P-Vd3(t) (4)。
2. the harmonic suppression control method for the BT-AC converter according to claim 1, wherein the topology of the BT-AC converter in step 5 and step 6 is:
one end of the input filter capacitor is connected with the anode of the single-phase alternating current input, and the other end of the input filter capacitor is connected with the cathode of the single-phase alternating current input; each bridge arm of the H bridge consists of 4 full-control power switch tubes and 1 clamping capacitor; one end of the positive and negative bridge arms is connected with the positive pole of the single-phase alternating current power supply, and the other end of the positive and negative bridge arms is connected with the negative pole; the positive and negative bridge arms have an output port to ground respectively, the two output ports form two-terminal output ports, and the voltages to ground of the positive and negative bridge arms are respectively VaAnd Vb。
3. The method as claimed in claim 2, wherein the fully-controlled power switch tube of the positive-polarity bridge arm is S from top to bottom2、S1、S1c、S2c；S2Is connected with the positive electrode of the single-phase alternating current power supply, and the collector is connected with S1Is connected with the collector of the collector; s1Emitter and S1cCollector electrode connection of S1cEmitter and S2cThe emitter of (3) is connected; s2cThe collector of the single-phase alternating current power supply is connected with the negative electrode of the single-phase alternating current power supply; clamping capacitor C1One end and S1Is connected with the collector of the other end of the collector and S1cThe emitting electrodes are connected; the output end A of the positive bridge arm is composed of a switch tube S1Emitter and S1cIs led out between the collectors.
4. The harmonic suppression control method for the BT-AC converter as claimed in claim 2, wherein the fully-controlled power switch tube of the negative polarity bridge arm is S from top to bottom in sequence2p、S1p、S1cp、S2cp；S2pIs connected with the positive electrode of the single-phase alternating current power supply, and the collector is connected with S1pIs connected with the collector of the collector; s1pEmitter and S1cpIs connected with the collector of the collector; s1cpEmitter and S2cpThe emitter of (3) is connected; s2cpCollector ofThe pole is connected with the negative pole of the single-phase alternating current power supply; clamping capacitor C2Clamped in the switching tube S1pCollector electrode of (1) and S1cpBetween the emitting electrodes, the output end B of the negative bridge arm is composed of a switch tube S1pEmitter and S1cpIs led out between the collectors.
5. The harmonic suppression control method for the BT-AC converter according to any of claims 2 to 4 wherein the input of the BT-AC converter is connected to a single phase AC power source, the converter deriving a 50Hz sinusoidal AC power V from the power sourceinAfter being converted by the BT-AC converter, the electric energy is sent to the power supply LfAnd CfThe input end of the LC low-pass filter is filtered to obtain 50Hz sinusoidal alternating current to supply power to a load R.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112821406A (en) * | 2020-12-31 | 2021-05-18 | 东北电力大学 | AC-AC type active power spring for distributed voltage regulation |
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Application publication date: 20200407 |