A power inverter ability signal transmission method based on driving pulse position

Abstract

The application discloses a power inverter energy signal and information co-transmission method based on driving pulse position, and belongs to the cross field of power electronics and communication technology. The method comprises the following steps: selecting different zero vector positions according to transmission information symbols; generating PWM carriers embedded with information according to variable zero vector position modulation; sampling load side voltage, inputting a band-pass filter to filter other frequency band harmonic interference; obtaining load side voltage spectrum through sliding window fast Fourier analysis; calculating to-be-observed demodulation harmonic components; outputting observed demodulation harmonic component amplitude through window integration; setting a demodulation threshold, comparing and judging, and outputting demodulation information. The application provides a power inverter energy signal and information co-transmission method based on driving pulse position, which embeds information symbols in zero vector positions, thereby saving communication equipment cost. Through the energy signal and information co-transmission strategy of embedding information in the zero vector position, the control loop is not dependent, and the power conversion is not affected, so that the energy signal and information co-transmission purpose of high power quality and stability is achieved.

Description

Technical Field

[0001] This invention relates to the fields of power electronics and communication technology, and in particular to a method for simultaneous power and communication transmission in a power inverter based on the position of the drive pulse. Background Technology

[0002] In modern power systems, communication systems are indispensable for improving the coordination between grid-connected equipment and promoting the intelligentization and digitalization of the power system. However, both wired and wireless communication networks increase the installation and maintenance costs of communication equipment. Early power line communication technology embedded information into the power bus through couplers, making the power bus a common channel for both energy transmission and information flow, thus achieving simultaneous transmission of energy and information, eliminating the need for independent communication lines, and reducing communication costs. However, the couplers relied upon by power line communication technology are not only bulky but also difficult to install. In addition, the information signals injected through the coupling coils can easily damage power quality and even cause malfunctions in grid protection devices. In the power grid, the insulation requirements between the coupler signal injection side and the grid side are high, posing safety hazards.

[0003] To address the shortcomings of power line communication (PLC) technology, a simultaneous energy and information transmission technology based on the switching ripple of power electronic converters has been proposed. This technology modulates information and energy simultaneously during the switching process of the power switching transistors, embedding the information into the bus voltage switching ripple, which is then extracted at the demodulation end to achieve simultaneous energy and information transmission. This technology eliminates the need for couplers, resulting in very low communication costs and minimal safety risks. Furthermore, in the switching ripple-based simultaneous energy and information transmission technology, the information modulation process and the energy modulation process are integrated, thus causing less damage to power quality compared to power line communication based on carrier coupling injection.

[0004] Appendix Figure 2 This is a schematic diagram based on PWM carrier frequency shift keying. During simultaneous power and signal transmission, different symbols "0" and "1" correspond to different frequencies of PWM triangular carriers. By shifting the PWM carrier frequency, information is embedded in the switching signal and the motor cable. At the demodulation end, a current sensor samples the cable current, which is then processed by a high-pass filter, a differential amplifier, and a Schmitt trigger comparator to output the demodulated signal. This strategy uses two different frequency triangular carriers to randomly switch, thus introducing more switching harmonic components, which significantly degrades power quality.

[0005] The energy-information co-transmission technology based on switching ripple is mainly used in DC / DC converters. Depending on the modulation method, it can be divided into two types: energy-information co-transmission based on reference signal superposition and energy-information co-transmission based on triangular carrier modulation. Based on the different degrees of freedom of the carrier, triangular carrier modulation can be further divided into amplitude modulation, frequency modulation, and phase modulation, embedding information into the amplitude, frequency, and phase degrees of freedom of the PWM carrier, respectively.

[0006] Figure 3 This is a schematic diagram of a simultaneous energy and information transmission technology based on reference signal superposition. Information symbols "0" and "1" are modulated into sinusoidal carrier signals of different frequencies using frequency shift keying (FSK), and then superimposed onto the reference voltage in the outer voltage loop. After the sinusoidal carrier participates in closed-loop control, the information is embedded in the switch drive signal and flows to another inverter or load side via an LC filter. At the receiving end, the voltage information is extracted and demodulated through modules such as a multiplex bandpass filter, envelope detector, and threshold judgment to extract the modulation-side information. However, this strategy relies on the control loop and constantly changes the reference voltage, sacrificing the stability of the simultaneous energy and information transmission system.

[0007] In DC / AC converters, due to their complex topology and control methods, as well as the requirements for high grid-connected power quality and electromagnetic compatibility, the development of simultaneous power transmission and signal transmission technologies is limited. Currently, they are mainly divided into reference signal superposition and PWM carrier frequency shift keying methods. However, the reference signal superposition-based simultaneous power transmission strategy constantly changes the amplitude of the reference signal, thus posing a challenge to the closed-loop stability of the system. Furthermore, the superposition of the carrier signal introduces harmonic interference at the carrier frequency, impairing power quality. Similarly, in the PWM carrier frequency shift keying-based simultaneous power transmission strategy, the triangular carrier frequency and switching frequency constantly change, generating more switching harmonics during modulation, which has a significant impact on power quality.

[0008] Considering the system stability and power quality issues caused by the simultaneous power and signal transmission technology in DC / AC converters, this invention proposes a power converter simultaneous power and signal transmission technology based on the drive pulse position. This technology embeds information into the drive pulse position to achieve high power quality and high stability in the power converter's simultaneous power and signal transmission. This technology does not rely on the control loop and does not introduce other switching frequencies; therefore, it provides good power quality without compromising system stability. Summary of the Invention

[0009] The purpose of this invention is to provide a power inverter energy and signal transmission method based on the position of the drive pulse, which solves the problems of low power quality and impaired system stability.

[0010] To achieve the above objectives, the present invention provides a method for simultaneous transmission of power inverter energy and information based on the position of the drive pulse, comprising the following steps:

[0011] S1. Select different carrier positions based on the transmitted information symbols;

[0012] S2. Generate a PWM carrier wave whose vertex position changes with information;

[0013] S3. Sample the load-side voltage and input it into the bandpass filter to filter out harmonic interference outside the switching frequency band;

[0014] S4. Using a sliding window fast Fourier analysis, the load-side voltage spectrum is obtained.

[0015] S5. Calculate the demodulated harmonic components fs±2f0 and fs±4f0 to be observed, where f s f0 is the switching frequency, and f0 is the fundamental frequency;

[0016] S6. Accumulate the amplitude of each observed harmonic component and output its integral amplitude within the window;

[0017] S7. Set the demodulation threshold, compare and judge, and output the demodulation information.

[0018] Preferably, in step S2, the generated PWM carrier is based on variable carrier position modulation, and the position of the triangular wave vertex changes continuously with the information symbols.

[0019] Preferably, in step S3, the load-side voltage is sampled and out-of-passband spectral interference is filtered out.

[0020] Preferably, in step S4, a sliding window Fourier analysis is used, with the window width equal to the symbol width, to obtain the load-side voltage spectrum.

[0021] Preferably, in step S5, the sideband frequencies of the demodulated harmonic components to be observed located in the switching frequency region are calculated, namely fs±2f0 and fs±4f0, where f s f0 is the switching frequency, and f0 is the fundamental frequency.

[0022] Preferably, in step S6, the width of the integration window is equal to the duration of the unit symbol.

[0023] Preferably, in step S7, the demodulation threshold is reasonably set according to the sampling rate and the sliding FFT result to minimize the bit error rate of the demodulated information output.

[0024] Therefore, the power inverter energy transmission method based on the position of the driving pulse, which adopts the above structure, has the following beneficial effects:

[0025] (1) The present invention is flexible in control, does not rely on the control loop, and can be implemented in both open-loop and closed-loop control modes. Furthermore, the switching frequency is fixed, there is no additional harmonic introduction, and the power quality is high during the transmission of energy and signal.

[0026] (2) The stability of the system of the present invention is not affected, and there are no additional communication hardware devices and communication signal lines, saving the cost of setting up and maintaining communication equipment.

[0027] (3) The present invention can easily be implemented by continuously switching the position of the triangular wave vertex to change the position of the driving pulse.

[0028] (4) The observation frequency interval used in this invention is twice the fundamental frequency of the resolution frequency. Therefore, the transmission bit rate of the strategy of this invention is 100 bits per second.

[0029] (5) This invention is applicable to single-phase, three-phase and four-phase DC / AC systems.

[0030] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0031] Figure 1 This is a flowchart of the variable drive pulse position modulation method for a power inverter based on the position of the drive pulse, according to the present invention.

[0032] Figure 2 This is a schematic diagram of the DC / AC simultaneous transmission technology based on PWM carrier frequency shift keying in the specification of this invention.

[0033] Figure 3 This is a schematic diagram of the DC / AC simultaneous signal transmission technology based on the reference signal superposition method described in this invention specification.

[0034] Figure 4 This is a two-level SVPWM control space vector distribution diagram for a power inverter energy and signal transmission method based on drive pulse position according to the present invention.

[0035] Figure 5 This is a diagram of the modulation strategy for transmitting "1" by the variable carrier vertex position in a power inverter power inverter power signal transmission method based on the position of the driving pulse, according to the present invention.

[0036] Figure 6 This is a diagram of the modulation strategy for transmitting "0" by the variable carrier vertex position in a power inverter power inverter power signal transmission method based on the position of the driving pulse, according to the present invention.

[0037] Figure 7 This is a diagram showing the variation range of the triangular carrier vertex position used in the power inverter energy and signal transmission method based on the position of the driving pulse in this invention.

[0038] Figure 8 This is a diagram of a point-to-point power communication system based on a DC / AC converter, which is a power inverter power communication method based on the position of the drive pulse according to the present invention.

[0039] Figure 9 This is a diagram of a sliding FFT-based demodulation strategy for a power inverter energy and information transmission method based on the position of a drive pulse, according to the present invention.

[0040] Figure 10 This invention relates to a power inverter energy and signal transmission method based on drive pulse position, specifically the modulation data and phase voltage v based on variable position energy and signal transmission modulation data. an Line current i a，b，c and line voltage v a，b，c Waveform diagram;

[0041] Figure 11 The diagram shows the line voltage spectrum at "0" in the power inverter energy-information co-transmission modulation transmission based on the variable zero vector position, according to the present invention, a power inverter energy-information co-transmission method based on the position of the driving pulse.

[0042] Figure 12 The line voltage spectrum diagram of the power inverter energy and signal transmission modulation transmission "1" based on the variable zero vector position in the present invention is shown.

[0043] Figure 13 This invention relates to a power inverter energy and information transmission method based on drive pulse position, specifically the demodulated data and phase voltage v based on the zero-vector position of the energy and information transmission method. an Line current i a，b，c and line voltage v a，b，c Waveform diagram. Detailed Implementation

[0044] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0045] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0046] Example

[0047] like Figure 1 As shown, this invention provides a method for simultaneous transmission of power inverter energy and information based on the position of the drive pulse, comprising the following steps:

[0048] S1. Select different carrier positions based on the transmitted information symbols;

[0049] S2. Generate a PWM carrier wave whose vertex position changes with information;

[0050] S3. Sample the load-side voltage and input it into the bandpass filter to filter out harmonic interference outside the switching frequency band;

[0051] S4. Using a sliding window fast Fourier analysis, the load-side voltage spectrum is obtained.

[0052] S5. Calculate the demodulated harmonic components fs±2f0 and fs±4f0 to be observed, where f s f0 is the switching frequency, and f0 is the fundamental frequency;

[0053] S6. Accumulate the amplitude of each observed harmonic component and output its integral amplitude within the window;

[0054] S7. Set the demodulation threshold, compare and judge, and output the demodulation information.

[0055] In step S2, the generated PWM carrier is based on variable carrier vertex position modulation, and the vertex position of the triangular wave changes continuously with the information code.

[0056] In step S3, the load-side voltage is sampled and out-of-passband spectral interference is filtered out;

[0057] In step S4, a sliding window Fourier analysis is used, with the window width equal to the symbol width, to obtain the load-side voltage spectrum;

[0058] In step S5, the sideband frequencies of the demodulated harmonic components to be observed located in the switching frequency region are calculated, namely fs±2f0 and fs±4f0, where f s f0 is the switching frequency, and f0 is the fundamental frequency.

[0059] In step S6, the width of the integration window is equal to the duration of the unit symbol.

[0060] In step S7, the demodulation threshold is reasonably set according to the sampling rate and the sliding FFT result to minimize the bit error rate of the demodulated information output.

[0061] Space Vector Pulse Width Modulation (SVPWM) selects a combination of space vectors based on the phase angle of the AC grid voltage vector and determines their duration, reconstructing a rotating output vector that matches the angular velocity of the grid voltage vector. For example, a two-level three-phase power converter can generate eight space vectors depending on different switching states. Figure 4 The space vector distribution diagram of two-level SVPWM control is shown. Among them, There are 6 non-zero vectors. and The zero vector corresponds to the working states of all switches being off and all switches being on, respectively.

[0062] Although all space vectors participate in the power conversion process, the distribution of space vectors has a high degree of freedom. Given that the action times of both non-zero and zero space vectors are fixed, the positions of each vector within a switching cycle can be flexibly adjusted. Therefore, information can be embedded into the position of the zero vector, enabling power converters to transmit power and information simultaneously based on the position of the drive pulse.

[0063] By adjusting the timing of the zero vector's action within a unit switching cycle, or the position of the triangular carrier vertex, a variable drive pulse position modulation (VDPPM) strategy for simultaneous transmission of energy and information can be developed. For example... Figure 5 and Figure 6 As shown, the zero vector When the active position is P1, it is used to transmit the symbol "1", zero vector When the active position is P2, it is used to send the symbol "0".

[0064] like Figure 7 As shown, the triangular carrier vertex position used in the variable drive pulse position modulation is approximately T times the midpoint of the unit period. s The range varies within 2. When the vertex position equals T... s At / 2, the triangular carrier wave evolves into a sawtooth wave.

[0065] like Figure 8 As shown, a point-to-point energy and information transmission system based on a power converter is described, consisting of a DC / AC inverter (single-phase, three-phase, or four-phase), an LCL filter, cables, a constant power load, and a demodulator. Information is modulated by variable drive pulse position modulation (VDPPM) to generate a switching drive signal embedded with the information. The information flows through the LCL filter and lines, and ultimately both energy and information are delivered to the load. On the load side, a voltage sensor measures the voltage v. a，b，c The output signal waveform is obtained after demodulation.

[0066] Variable Drive Pulse Position (VDPPM) demodulation technology generates harmonic component fluctuations near the switching frequency. Based on this, the demodulator employs a sliding fast Fourier transform (SFT) demodulation strategy. The demodulation process is as follows: Figure 9 As shown. First, a bandpass filter with a center frequency equal to the switching frequency filters out the voltage v. abFor other frequency band noise, an FFT operation is then performed on the filtered load voltage signal within a sliding window with a width of one bit symbol, and the spectral components near the switching frequency are statistically analyzed. Harmonic frequency components with significant differences when transmitting symbols "0" and "1" are identified, and statistical rules for these harmonic frequency components are established. Within an integration window with a width of one bit symbol, the harmonic calculation results under these statistical rules are accumulated and output, and then reset to zero at the start of the next integration window. Finally, an appropriate threshold is selected to evaluate the integration output result, and the demodulated signal is extracted.

[0067] like Figure 10-12 The modulation waveform and spectrum of the simultaneous transmission of energy and signal based on the variable drive pulse position are shown. The average harmonic distortion (THD) is 0.445%. Similarly, based on the load voltage spectrum of the simultaneous transmission of energy and signal based on the variable drive pulse position, it can be analyzed that when the transmission symbol is "0" and "1", the frequency components of the load-side voltage differ at 19.8kHz, 19.9kHz, 20.1kHz, and 20.2kHz, which can be used as the basis frequencies in the harmonic statistics rules. Figure 13 This is the demodulated waveform based on the variable drive pulse position. It can be observed that in this example, the S... FFT The waveform integral output and the demodulated information sequence after threshold determination.

[0068] Therefore, this invention employs the aforementioned method for simultaneous power and information transmission in a three-phase power inverter based on the position of the drive pulse. This technique embeds information symbols into the position of the drive pulse to save on communication equipment costs. By embedding information into the position of the drive pulse, this simultaneous power and information transmission strategy does not rely on the control loop and does not affect power conversion, achieving high power quality and stability in simultaneous power and information transmission, with a communication rate of 100 bits per second.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for simultaneous transmission of power inverter energy and information based on the position of the driving pulse, characterized in that, Includes the following steps: S1. Select different carrier positions based on the transmitted information symbols; S2. Generate a PWM carrier wave whose vertex position changes with information; S3. Sample the load-side voltage and input it into the bandpass filter to filter out harmonic interference outside the switching frequency band; S4. Using a sliding window fast Fourier analysis, the load-side voltage spectrum is obtained. S5. Calculate the demodulated harmonic components to be observed. f s±2 f 0、 f s±4 f 0, where f s For switching frequency, f 0 represents the fundamental frequency; S6. Accumulate the amplitude of each observed harmonic component and output its integral amplitude within the window; S7. Set the demodulation threshold, compare and determine, and output the demodulation information; In step S2, the generated PWM carrier is based on variable carrier position modulation, and the position of the triangular wave vertex changes continuously with the information symbols.

2. The power inverter energy transmission method based on drive pulse position according to claim 1, characterized in that, In step S4, a sliding window Fourier analysis is used, with the window width equal to the symbol width, to obtain the load-side voltage spectrum.

3. The power inverter energy transmission method based on drive pulse position according to claim 1, characterized in that, In step S5, the sideband frequency of the demodulated wave component to be observed located in the switching frequency region is calculated, i.e. f s±2 f 0、 f s±4 f 0, where f s For switching frequency, f 0 represents the fundamental frequency.

4. The power inverter energy transmission method based on drive pulse position according to claim 1, characterized in that, In step S6, the width of the integration window is equal to the duration of the unit symbol.

5. The power inverter energy transmission method based on drive pulse position according to claim 1, characterized in that, In step S7, the demodulation threshold is reasonably set according to the sampling rate and the sliding FFT result to minimize the bit error rate of the demodulated information output.

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