A signal-energy simultaneous transmission system based on three-phase inverter sideband harmonics

Abstract

The present invention discloses a complete implementation process of a signal-energy simultaneous transmission system based on three-phase inverter sideband harmonics: on the three-phase inverter side, signal modulation is achieved by performing phase shift control on the pulse-width modulated carrier signal; on the load side, the influence of other switching harmonics is reduced by performing abc-dq transformation on the sideband harmonics, so that the harmonics obtained by the filter are mainly the sideband harmonics carrying the target signal; finally, the sideband harmonics are demodulated by a coherent demodulator, reducing the demodulation difficulty and bit error rate of the system.

Description

Technical Field

[0001] The present invention belongs to the technical field of renewable energy power generation, and more specifically, relates to a system for simultaneously transmitting signals and energy based on sideband harmonics of a three-phase inverter. Background Art

[0002] Communication systems are an indispensable component of power systems, capable of transmitting status data, fault information, and control instructions for power equipment. This allows control centers to quickly respond to and handle various situations, ensuring a stable power supply and quality. Currently, communication in power systems is primarily achieved through wireless and wired communication technologies. Wireless communication offers excellent adaptability and speed, but suffers from signal attenuation, limited transmission distance, and potential interference from various noise and cyberattacks, resulting in low transmission reliability. Wired communication, primarily achieved by adding additional communication lines, offers strong interference resistance and minimal attenuation. However, independent communication systems for each component incur additional costs for the construction and maintenance of signal lines. Therefore, a new and reliable communication technology is urgently needed for signal transmission in power systems.

[0003] With advances in communications and power electronics technologies, a power system communication method known as power line carrier communication (PLC) has emerged and garnered widespread attention. PLC utilizes existing power systems (power lines, cables, and wireless) as a signal transmission channel for real-time signal transmission, eliminating the need for independent communication systems or lines. It boasts low investment, high flexibility, and wide coverage. Against the backdrop of China's vigorous development of the Energy Internet and smart grid, transmitting information over power lines not only comprehensively complements and improves my country's communication platforms but also enhances its global competitiveness and leading position in smart grid construction. However, traditional PLC requires additional circuitry to inject and amplify sinusoidal signals of specific frequencies, which undoubtedly increases grid system costs. Furthermore, studies have shown that PLC can interfere with the normal operation of power electronic converters, reducing the system's energy transmission efficiency. Reducing the impact of PLC on power quality and system energy density has become an urgent issue.

[0004] Power electronic converters, as common energy conversion devices connecting renewable energy sources with electrical devices, play a crucial role in renewable energy generation systems. They play a crucial role in power conversion and control, enabling efficient and reliable energy conversion. Pulse-width modulation (Pulse-width modulation) is a key method for achieving energy conversion in power electronic converters. By comparing a reference signal with a high-frequency carrier signal, gate-level drive signals are generated to control the switching devices in the converter's bridge arms, resulting in a series of pulses with equal amplitude but varying widths at the output. These pulses can replace a sine wave or desired waveform. During the Pulse-width modulation process, the amplitude, frequency, and phase of the sinusoidal reference signal and triangular carrier signal provide additional degrees of freedom for signal encoding, giving power electronics the potential to carry and transmit information. In recent years, the method of leveraging the additional degrees of freedom of pulse-width modulation in power electronic converters for signal transmission has been termed signal-energy simultaneous transmission (SEM). Currently, SEM is primarily used in DC power grids, with limited application in inverters and AC power grids. Therefore, a signal and energy simultaneous transmission system (SEM) for AC power grids and inverters is urgently needed. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing technology and provide a signal-energy simultaneous transmission system based on three-phase inverter sideband harmonics. The sideband harmonics generated by the pulse width modulation of the three-phase inverter are used for signal modulation, transmission and demodulation. There is no need for additional injection of harmonic signals and signal coupling devices, which reduces the cost and volume of the system and can improve the power quality of the system.

[0006] To achieve the above-mentioned object, the present invention provides a signal and energy simultaneous transmission system based on three-phase inverter sideband harmonics, characterized by comprising:

[0007] The controller performs phase shift keying modulation on the high frequency triangle wave according to the value of the input square wave signal to generate a phase shift carrier signal;

[0008] The sinusoidal pulse width modulation module generates a pulse width modulation wave by comparing the sinusoidal signal and the phase-shifted carrier signal, which is used to control the switching action of the three-phase bridge arm active switches S1 to S6; wherein, when the sinusoidal signal value is greater than the carrier signal, the sinusoidal pulse width modulation outputs a high level to control the switch tube to be turned on; conversely, the sinusoidal pulse width modulation outputs a low level to control the switch tube to be turned off;

[0009] The three-phase bridge arm is composed of active switches S1-S6 and diodes D1-D6. The pulse width modulation wave generates a level signal with a continuously changing three-phase duty cycle by controlling the conduction sequence of the active switches S1-S6. Since the carrier signal undergoes a corresponding phase shift as the value of the input square wave signal changes, when the input square wave signal changes, the sinusoidal pulse width modulation output modulation wave will change, thereby affecting the switching action of the switch tube and generating sideband harmonics that change with the input square wave signal.

[0010] The LC filter circuit consists of L abc and C abc It is used to filter the output current of each phase of the three-phase bridge arm to obtain a sinusoidal current signal with good power quality, and then input it to the three-phase AC load;

[0011] The abc-dq coordinate transformation module is used to transform the three-phase load voltage U abc Perform abc-dq transformation to obtain the voltage signal U in the dq rotating coordinate system d with U q ;

[0012] The bandpass filter is used to filter the voltage signal U d Filter and obtain the d-axis sideband harmonic H carrying the target signal s ;

[0013] H s =A s J2(Q Km )cos(ω c t+φ c )cos[3ω0t+2φ Km ]

[0014] Among them, A s is the amplitude of the sideband harmonics, J2(Q Km ) is the second-order Bessel function, Q Km is the pulse width modulation depth, ω c is the angular frequency of the pulse width modulation carrier signal, φ c is the inverter output voltage phase, ω0 is the inverter output voltage angular frequency, φ Km is the phase of the pulse width modulated carrier signal;

[0015] The phase-locked loop phase-locks the sideband harmonics obtained by the bandpass filter to obtain the voltage phase φ of the sideband harmonics c and the pulse width modulated carrier signal phase φ Km ;

[0016] The signal generator is based on the phase φ obtained by the phase-locked loop c and φ Km Generate synchronous demodulation signal Wc and W Km ;

[0017] The coherent demodulator uses the synchronous demodulation signal W c and W Km The d-axis sideband harmonics H s Perform two coherent demodulations to obtain an output signal that is consistent with the input square wave signal.

[0018] The object of the invention of the present invention is achieved like this:

[0019] The complete implementation process of the signal-energy simultaneous transmission system based on the sideband harmonics of the three-phase inverter of the present invention is as follows: on the three-phase inverter side, signal modulation is achieved by performing phase shift control on the pulse width modulated carrier signal; on the load side, the influence of other switching harmonics is reduced by performing abc-dq transformation on the sideband harmonics, so that the harmonics obtained by the filter are mainly the sideband harmonics carrying the target signal; finally, the sideband harmonics are demodulated by a coherent demodulator, thereby reducing the demodulation difficulty and bit error rate of the system.

[0020] At the same time, the signal-energy simultaneous transmission system based on three-phase inverter sideband harmonics of the present invention also has the following beneficial effects:

[0021] (1) By performing phase shift keying on the pulse width modulated carrier signal through the controller, the modulation of the digital signal to the sideband harmonics can be realized. There is no need to inject additional harmonic signals and signal coupling devices, which reduces the cost and volume of the system and is beneficial to the power quality of the system.

[0022] (2) Three-phase AC load side voltage U abc Use abc-dq transformation to reduce the impact of other switching harmonics, so that the harmonics obtained by the bandpass filter are mainly sideband harmonics carrying the target signal, reducing the system demodulation complexity and bit error rate;

[0023] (3) The present invention provides a complete signal-energy transmission process, including modulation, transmission and demodulation. In this process, sideband harmonics are proposed for the first time as a carrier of signal-energy transmission, and it is also applicable to other methods using sideband harmonics as a carrier. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a structural diagram of the signal-energy simultaneous transmission system based on three-phase inverter sideband harmonics of the present invention;

[0025] Figure 2 It is a diagram of the process of modulating a digital signal into a phase-shifted carrier signal;

[0026] Figure 3 The sideband harmonic signal waveform filtered by the bandpass filter and the cos(ω c t+φ c )’s demodulation result;

[0027] Figure 4 is cos(ω0t+φ Km )’s demodulation process and results;

[0028] Figure 5 It is the three-phase inverter output current and corresponding total harmonic distortion ratio at different transmission rates of the signal-energy simultaneous transmission system based on the three-phase inverter sideband harmonics. DETAILED DESCRIPTION

[0029] The following describes the specific embodiments of the present invention in conjunction with the accompanying drawings so that those skilled in the art can better understand the present invention. It should be noted that in the following description, when detailed descriptions of known functions and designs may dilute the main content of the present invention, such descriptions will be omitted here.

[0030] Example

[0031] Figure 1 This is a structural diagram of the signal and energy simultaneous transmission system based on three-phase inverter sideband harmonics of the present invention.

[0032] In this embodiment, if Figure 1 As shown, the present invention provides a signal and energy simultaneous transmission system based on three-phase inverter sideband harmonics, comprising: a controller, a sinusoidal pulse width modulation module, a DC voltage source, a three-phase bridge arm, an LC filter circuit, a three-phase AC load, an abc-dq coordinate transformation module, a bandpass filter, a phase-locked loop, a signal generator, and a coherent demodulator;

[0033] The controller performs phase shift keying modulation on the high-frequency triangle wave according to the value of the input square wave signal to generate a phase-shifted carrier signal;

[0034] In this embodiment, the phase-shifted carrier signal is a high-frequency triangular wave signal with a continuously changing phase. Its phase is determined by the input square wave signal and represents different signals. When the value of the input square wave signal is 0, the phase shift of the triangular wave is 0°, and when the value of the square wave signal is 1, the phase shift of the triangular wave is 180°.

[0035] The sine pulse width modulation module generates a pulse width modulation wave by comparing the sine signal and the phase-shifted carrier signal, which is used to control the switching action of the three-phase bridge arm active switches S1 to S6. When the sine signal value is greater than the carrier signal, the sine pulse width modulation output is high, controlling the switch tube to conduct; otherwise, the sine pulse width modulation output is low, controlling the switch tube to turn off.

[0036] The three-phase bridge arm consists of active switches S1-S6 and diodes D1-D6. The pulse-width modulation wave generates a level signal with a continuously changing three-phase duty cycle by controlling the conduction sequence of active switches S1-S6. Because the carrier signal undergoes a corresponding phase shift as the value of the input square wave signal changes, the sinusoidal pulse-width modulation output modulated wave changes when the input square wave signal changes, affecting the switching action of the switch tube and generating sideband harmonics that change with the input square wave signal, realizing the transfer of information from digital signal to analog voltage.

[0037] In this embodiment, the active switches S1 to S6 are all insulated bipolar transistors with diodes, with terminal c being the collector, terminal g being the drain, and terminal e being the emitter;

[0038] Below we introduce the structure of the three-phase bridge arm in detail:

[0039] The collector c of each active switch is connected to the cathode of the corresponding diode, the emitter e of each active switch is connected to the anode of the corresponding diode, and the drain g of each active switch is connected to the gate-level drive signal input by the controller; a diode is connected in parallel between the emitter e and the collector c of each active switch, with the anode of the diode connected to the emitter and the cathode connected to the collector; the collectors of the active switches S1, S3, and S5 are connected to the positive electrode of the DC voltage source, and the emitters of the active switches S2, S4, and S6 are connected to the negative electrode of the DC voltage source; the emitter of the active switch S1 is connected to the collector of the active switch S4, the emitter of the active switch S3 is connected to the collector of the active switch S6, and the emitter of the active switch S5 is connected to the collector of the active switch S2, thereby forming a three-phase bridge arm of the inverter, and an LC filter circuit is connected at the midpoint of each phase of the three-phase bridge arm;

[0040] The LC filter circuit consists of L abc and C abc The filter is used to filter the output current of each phase of the three-phase bridge arm to obtain a sinusoidal current signal with good power quality, which is then input to the three-phase AC load. In this way, the sideband harmonics are transmitted along the power line and can still maintain their frequency domain characteristics after passing through the LC filter circuit and the three-phase AC load.

[0041] The abc-dq coordinate transformation module is used to transform the three-phase load voltage U abc Perform abc-dq transformation to obtain the voltage signal U in the dq rotating coordinate system d with U q ;

[0042] Bandpass filter for voltage signal U d Filter and obtain the d-axis sideband harmonic H carrying the target signal s ;

[0043] Hs =A s J2(Q Km )cos(ω c t+φ c )cos[3ω0t+2φ Km ]

[0044] Among them, A s is the amplitude of the sideband harmonics, J2(Q Km ) is the second-order Bessel function, Q Km is the pulse width modulation depth, ω c is the angular frequency of the pulse width modulation carrier signal, φ c is the inverter output voltage phase, ω0 is the inverter output voltage angular frequency, φ Km is the pulse width modulation carrier signal phase inverter output voltage phase; in this embodiment, Q Km =0.4π,ω c =20000πrad / s, ω0=100πrad / s.

[0045] The signal generator obtains the phase φ according to the phase-locked loop c and φ Km Generate synchronous demodulation signal W c and W Km , where the synchronous demodulation signal W c The frequency is ω c , the phase is φ c Sinusoidal signal; synchronous demodulation signal W Km The frequency is 3ω0 and the phase is φ c The sine signal.

[0046] The coherent demodulator uses the synchronous demodulation signal W c and W Km The d-axis sideband harmonics H s Perform two coherent demodulations to obtain an output signal that is consistent with the input square wave signal.

[0047] In this embodiment, the coherent demodulator is composed of a multiplier and a low-pass filter. According to the frequency domain characteristics of the sideband harmonics, this embodiment uses two groups of coherent demodulators in series to demodulate the sideband harmonic signals, wherein the first group of coherent demodulators uses the sideband harmonics H s and synchronous demodulation signal W c As input, sideband harmonics H s The second group of coherent demodulators output signals and synchronous demodulation signals W of the first group of coherent demodulators Km As input, complete the sideband harmonic H s The second demodulation.

[0048] In this embodiment, Figure 2 The present invention demonstrates the process of modulating a digital signal into a phase-shifted carrier signal. Phase-shift keying is performed on a high-frequency triangular wave signal according to the value of an input square wave signal to generate a sinusoidal pulse-width modulated phase-shifted carrier signal having the same variation pattern as the input square wave signal. When the value of the input square wave signal is 0, the phase shift of the triangular wave is 0°, and when the value of the square wave signal is 1, the phase shift of the triangular wave is 180°. The generated phase-shifted carrier signal is compared with a sinusoidal reference signal output by a three-phase inverter control loop to generate a pulse-width modulated wave carrying the same signal and control the three-phase inverter switch tube to generate sideband harmonics carrying the input signal. The digital signal is modulated into the sinusoidal pulse-width modulated carrier signal through phase-shift keying and transmitted and demodulated on the power line using the sideband harmonics fixedly generated by the three-phase inverter. No additional signal coupling devices or signal injection are required, which not only reduces the cost and volume of the system but also improves the power quality of the output voltage of the three-phase inverter.

[0049] In this embodiment, Figure 3 The waveform of the sideband harmonic signal filtered by the bandpass filter and the cos(ω c t+φ c ) is the demodulation result; wherein, Figure 3 (a) shows the filtering result of the bandpass filter, which is the same as the sideband harmonic H after abc-dq transformation. s The ABC-DQ transform has the same frequency domain characteristics and shape and does not contain other inverter switching harmonics. This shows that the ABC-DQ transform reduces the influence of other switching harmonics, so that the harmonics obtained by the bandpass filter are mainly sideband harmonics carrying the target signal, which can reduce the system demodulation complexity and bit error rate. Figure 3 (b) shows the synchronous demodulation signal W generated by the phase-locked loop and the sideband harmonics obtained by the bandpass filter. c The relationship between them is that they have the same center frequency and phase, so the synchronous demodulation signal can be used for coherent demodulation; Figure 3 (c) shows the signal waveform obtained by the first coherent demodulation using the synchronous demodulation signal. The signal frequency after filtering is 150 Hz, indicating that the angular frequency of the signal obtained by the first demodulation and filtering is 3 times that of ω0, which is consistent with H s formula.

[0050] In this embodiment, Figure 4 Shows the effect of cos(ω0t+φ Km ) demodulation process and results; wherein, Figure 4 (a) shows the synchronous demodulation signal W generated by the phase-locked loop at a frequency of 150 Hz. Km The output square wave can be obtained by judging the positive or negative of the demodulated signal after low-pass filtering and the result of coherent demodulation. Figure 4(b) shows the comparison between the output signal and input signal obtained based on the second demodulation result; among them, when the value of the second demodulated signal is less than 0, the output value is "1", and when the value of the second demodulated signal is greater than 0, the output value is "0". Through comparison, it can be found that the square wave signal obtained by coherent demodulation and synchronization signal demodulation is consistent with the input signal waveform, and the delay is within 3ms.

[0051] Figure 5 The three-phase inverter output current and the corresponding total harmonic distortion ratio of the signal-energy simultaneous transmission system based on the three-phase inverter sideband harmonics at different transmission rates are shown, where: Figure 5 (a) Figure 5 (b) and Figure 5 (c) The three-phase current and the total harmonic distortion ratio of the current are respectively no transmission signal, a signal transmission rate of 40 bps, and a signal transmission rate of 400 bps. By comparing the total harmonic distortion ratio of the current under no signal transmission and different transmission rates, it can be found that the present invention has little impact on the output power quality of the system.

[0052] Although the above describes the illustrative specific embodiments of the present invention to facilitate understanding of the present invention by those skilled in the art, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations using the concepts of the present invention are protected.

Claims

1. A signal and energy simultaneous transmission system based on three-phase inverter sideband harmonics, characterized in that: include: The controller performs phase shift keying modulation on the high-frequency triangle wave according to the value of the input square wave signal to generate a phase shift carrier signal; The sine pulse width modulation module generates a pulse width modulation wave by comparing the sine signal and the phase-shifted carrier signal, which is used to control the switching action of the three-phase bridge arm active switches S1 to S6. When the value of the sine signal is greater than the phase-shifted carrier signal, the sine pulse width modulation module outputs a high level to control the switch tube to turn on; otherwise, the sine pulse width modulation module outputs a low level to control the switch tube to turn off. The three-phase bridge arm consists of active switches S1-S6 and diodes D1-D6. The pulse-width modulation wave generates a level signal with a continuously changing three-phase duty cycle by controlling the conduction sequence of the active switches S1-S6. Because the carrier signal undergoes a corresponding phase shift as the value of the input square wave signal changes, the pulse-width modulation wave output by the sinusoidal pulse-width modulation module changes when the input square wave signal changes, thereby affecting the switching action of the switch tube and generating sideband harmonics that change with the input square wave signal. The LC filter circuit consists of L abc and C abc It is used to filter the output current of each phase of the three-phase bridge arm to obtain a sinusoidal current signal with good power quality, and then input it to the three-phase AC load; The abc-dq coordinate transformation module is used to transform the three-phase load voltage U abc Perform abc-dq transformation to obtain the voltage signal U in the dq rotating coordinate system d with U q ; Bandpass filter for voltage signal U d Filter and obtain the d-axis sideband harmonic H carrying the target signal s ; H s =A s J2(Q Km )cos(ω c t+φ c )cos[3ω0t+2φ Km ] Among them, A s is the amplitude of the sideband harmonics, J2(Q Km ) is the second-order Bessel function, Q Km is the pulse width modulation depth, ω c is the angular frequency of the pulse width modulation carrier signal, φ c is the inverter output voltage phase, ω0 is the inverter output voltage angular frequency, φ Km is the phase of the pulse width modulated carrier signal; The phase-locked loop phase-locks the sideband harmonics obtained by the bandpass filter to obtain the voltage phase φ of the sideband harmonics. c and the pulse width modulated carrier signal phase φ Km ; The signal generator obtains the phase φ according to the phase-locked loop c and φ Km Generate synchronous demodulation signal W c and W Km ; The coherent demodulator uses the synchronous demodulation signal W c and W Km The d-axis sideband harmonics H s Perform two coherent demodulations to obtain an output signal that is consistent with the input square wave signal.

2. The signal and energy simultaneous transmission system based on three-phase inverter sideband harmonics according to claim 1, characterized in that: The structure of the three-phase bridge arm is: The collector c of each active switch is connected to the cathode of the corresponding diode, the emitter e of each active switch is connected to the anode of the corresponding diode, and the drain g of each active switch is connected to the gate-level drive signal input by the controller; a diode is connected in parallel between the emitter e and the collector c of each active switch, with the anode of the diode connected to the emitter and the cathode connected to the collector; the collectors of the active switches S1, S3, and S5 are connected to the positive electrode of the DC voltage source, and the emitters of the active switches S2, S4, and S6 are connected to the negative electrode of the DC voltage source; the emitter of the active switch S1 is connected to the collector of the active switch S4, the emitter of the active switch S3 is connected to the collector of the active switch S6, and the emitter of the active switch S5 is connected to the collector of the active switch S2, thereby forming a three-phase bridge arm of the inverter, and an LC filter circuit is connected at the midpoint of each phase of the three-phase bridge arm.

3. The signal and energy simultaneous transmission system based on three-phase inverter sideband harmonics according to claim 1, characterized in that: The phase-shifted carrier signal is a high-frequency triangular wave signal with continuously changing phase, and its phase is determined by the input square wave signal. When the value of the input square wave signal is 0, the phase shift of the triangular wave is 0°, and when the value of the square wave signal is 1, the phase shift of the triangular wave is 180°.

4. The signal and energy simultaneous transmission system based on three-phase inverter sideband harmonics according to claim 1, characterized in that: The synchronous demodulation signal W c The frequency is ω c , the phase is φ c The synchronous demodulated signal W Km The frequency is 3ω0 and the phase is φ c The sine signal.

5. The signal and energy simultaneous transmission system based on three-phase inverter sideband harmonics according to claim 1, characterized in that: The coherent demodulator includes two groups. The first group of coherent demodulators uses the sideband harmonics H s and synchronous demodulation signal W c As input, sideband harmonics H s The second group of coherent demodulators output signals and synchronous demodulation signals W of the first group of coherent demodulators Km As input, complete the sideband harmonic H s The second demodulation.

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