Cascade h-bridge power carrier communication method based on harmonic injection

Abstract

The application discloses a kind of cascade H bridge power carrier communication methods based on harmonic injection, belong to power carrier communication field.The method is realized signal modulation by injecting harmonic to the drive signal of switch tube, signal demodulation is realized by FFT operation to the current signal collected, specifically including the setting of baseband signal and harmonic signal, the setting of receiving end emitter, current acquisition and demodulation and demodulation and the like steps.The application first proposes the cascade H bridge power carrier communication method based on harmonic injection, without increasing additional equipment, parameter design is simple, realizes the stable signal transmission of cascade H bridge system, and signal attenuation is less, and signal transmission efficiency is higher.

Description

Technical Field

[0001] This invention relates to the field of power line carrier communication, and more particularly to a cascaded H-bridge power line carrier communication method based on harmonic injection. Background Technology

[0002] In practical applications, to achieve efficient and stable operation of cascaded H-bridge systems, these systems must transmit information simultaneously with electrical energy to perform functions such as load output feedback control, multi-controller synchronization and coordination, and system status monitoring. Therefore, how to accurately and quickly transmit information is a pressing issue in current cascaded H-bridge power line carrier communication.

[0003] In the article titled "Research on Photovoltaic Power Optimization System and Power Line Communication" (Wang Zhikun. Research on Photovoltaic Power Optimization System and Power Line Communication [D]. Zhejiang University, 2018.), the cascaded H-bridge multilevel inverter adopts a master-slave control method. Each H-bridge module is a slave controller, sending the status information of its own components; the master controller on the main filter receives the status information of each H-bridge, calculates and sends the reference control quantity to each H-bridge module. The master controller is located on the AC line, which is greatly affected by other signals and requires an external multiplier and bandpass filter for demodulation, resulting in a complex structure and high cost.

[0004] The article titled "Research on Key Technologies of Cascaded Photovoltaic Grid-Connected Inverter System" (Mao Wang. Research on Key Technologies of Cascaded Photovoltaic Grid-Connected Inverter System [D]. Hefei University of Technology, 2020) describes a current pulse-type PLC intelligent monitoring scheme for photovoltaic modules. Each photovoltaic panel is equipped with a Smart Communication Module (SCM), and the SCM circuit consists of an MCU and transistors. When the SCM is working, the MCU controls the switching of the transistors to modulate and superimpose the data signal into the photovoltaic string loop current in a binary pulse manner. The Data Collector Unit (DCU) receives the current pulse signal through a coil and converts it into a voltage signal. Then, after filtering and shaping circuitry, the original digital baseband signal is restored to complete the entire communication. This scheme uses inductive indirect coupling, which does not require direct connection to the power line and is safe and reliable. However, the transmission efficiency of inductive coupling is greatly related to the electromagnetic characteristics of the coupling circuit.

[0005] In summary, the existing technology still has the following problems:

[0006] 1. When cascaded H-bridges are used for power line carrier communication, additional communication devices need to be added to the original circuit, making the circuit more complex and increasing costs.

[0007] 2. When power line carrier communication uses inductive coupling, additional inductor components are required. Its transmission efficiency is related to the electromagnetic characteristics of the inductor, and there is a magnetic saturation phenomenon. The transmission effect is not ideal for high-frequency carrier signals, and the signal attenuation is large, resulting in low transmission efficiency. Summary of the Invention

[0008] The technical problem to be solved by this invention is to overcome the limitations of the above-mentioned technical solutions. In view of the aforementioned problems, this invention provides a cascaded H-bridge power line carrier communication method based on harmonic injection, which does not require additional equipment, has simple parameter design, and realizes stable signal transmission of the cascaded H-bridge system.

[0009] The objective of this invention is achieved as follows: This invention provides a cascaded H-bridge power line carrier communication method based on harmonic injection. The cascaded H-bridge consists of n+1 identical H-bridge units, where one is designated as the master H-bridge unit and the other n are designated as slave H-bridge units. The n+1 cascaded H-bridge units are connected to the output-side load through an LC filter. Each H-bridge unit includes an H-bridge, and each H-bridge includes four switching transistors with anti-parallel diodes, denoted as switching transistor S. ij i is the sequence number of the H-bridge unit, i = 0, 1, ..., n, where the sequence number of the main H-bridge unit is 0, j is the sequence number of the switching transistor, j = 1, 2, 3, 4; the switching transistor S i1 and switching transistor S i2 Forming a bridge arm, the switching transistor S i3 and switching transistor S i4 Form another bridge arm;

[0010] The communication method achieves signal modulation by injecting harmonics into the drive signal of the switching transistor and demodulates the signal by performing FFT operations on the acquired current signal, including the following steps:

[0011] Step 1: Setting the baseband signal and harmonic signal

[0012] The original signal that the cascaded H-bridge needs to transmit is denoted as the baseband signal, which is a square wave signal with a period of T. B The signal with frequency λf0 is denoted as the injected harmonic signal, where λ is the order of the harmonic and f0 is the frequency of the carrier signal.

[0013] The high and low levels in the baseband signal correspond to the digital signal to be transmitted. When the baseband signal is high, the digital signal transmitted by the cascaded H-bridge is "1", and when the baseband signal is low, the digital signal transmitted by the cascaded H-bridge is "0".

[0014] Step 2, Determining the signal transmitting end and the signal receiving end

[0015] When the main H-bridge unit sends a signal, the main H-bridge unit is the transmitter, and all the slave H-bridge units are the receivers; when any one of the n slave H-bridge units sends a signal, the slave H-bridge unit that sends the signal is the transmitter, and the main H-bridge unit is the receiver.

[0016] Step 3, Modulation of the driving signal

[0017] Switch S ij The driving signal is denoted as driving signal G. ij The specific modulation includes:

[0018] (1) When the baseband signal is low level

[0019] When the main H-bridge unit is used as the transmitting short end, it outputs four SPWM signals with a frequency of f0, which are used as switching transistors S... 01 Switch S 02 Switch S 03 and switching transistor S 04 The drive signal, at this time the drive signal G 01 With G 02 Complementary, driving signal G 03 With drive signal G 04 Complementary, driving signal G 01 With drive signal G 04 Same direction;

[0020] When the H-bridge unit is used as the transmitting end, each of the n H-bridge units sends out four SPWM signals with a frequency of f0, which serve as the corresponding switching transistors S. i1 Switch S i2 Switch S i3 and switching transistor S i4 The drive signal, at this time the drive signal G i1 With G i2 Complementary, driving signal G i3 With drive signal G i4 Complementary, driving signal G i1 With drive signal G i4 Same direction;

[0021] (2) When the baseband signal is high level

[0022] When the main H-bridge unit is used as the transmitting short end, a harmonic with frequency λf0 is injected into the driving signal G of the main H-bridge unit. 0j In this process, the drive signals of the switching transistors in other H-bridge units remain unchanged;

[0023] When a slave H-bridge unit acts as a transmitter, a harmonic with frequency λf0 is injected into the drive signal G of that slave H-bridge unit acting as the transmitter. ijIn this process, the drive signals of the switching transistors in other H-bridge units remain unchanged;

[0024] Step 4: Acquire current and demodulate it.

[0025] The current at the receiving end is collected, and the amplitude Sp of the signal carrier with frequency λf0 is obtained after FFT operation. The average value of the maximum frequency value F1 and the minimum frequency value F2 of the signal carrier when harmonics are injected is set as the reference value a. The signal is judged and transmitted according to the following rules:

[0026] When Sp < a, the sent signal is determined to be "0", and a low-level signal is output.

[0027] When Sp > a, the sent signal is determined to be "1", and a high-level signal is output.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] 1. The communication method of the present invention can realize power and communication transmission simultaneously through only the power transmission circuit, without the need to add additional communication equipment to the circuit, thus saving communication costs and simplifying parameter design.

[0030] 2. The communication method of the present invention can realize bidirectional communication, that is, information can be sent from the main H-bridge unit to the slave H-bridge unit, and information can be sent from the H-bridge unit to the main H-bridge unit, which is more convenient and faster.

[0031] 3. The communication method of this invention modulates the signal by injecting harmonic components into the modulating wave, which is simpler and easier to implement compared to other modulation methods. No additional components are needed for signal demodulation; demodulation can be achieved simply by acquiring the current signal.

[0032] 4. The communication method of the present invention does not require any additional equipment for signal transmission and demodulation, resulting in less signal attenuation and higher signal transmission efficiency. Attached Figure Description

[0033] Figure 1 This is a topology diagram of the cascaded H-bridge in an embodiment of the present invention;

[0034] Figure 2 This is a block diagram of power line carrier communication based on harmonic injection in an embodiment of the present invention;

[0035] Figure 3 This is a comparison diagram of the input signal waveform and the output signal waveform in an example of the present invention. Detailed Implementation

[0036] The invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0037] Figure 1This is a topology diagram of the cascaded H-bridge in an example of the present invention. For example... Figure 1 As shown, the cascaded H-bridge consists of n+1 identical H-bridge units, one of which is designated as the master H-bridge unit, and the other n are designated as slave H-bridge units. The n+1 cascaded H-bridge units are connected to the output load via an LC filter. Each H-bridge unit includes one H-bridge, and each H-bridge includes four switching transistors with anti-parallel diodes, denoted as switching transistor S. ij i is the sequence number of the H-bridge unit, i = 0, 1, ..., n, where the sequence number of the main H-bridge unit is 0, j is the sequence number of the switching transistor, j = 1, 2, 3, 4; the switching transistor S i1 and switching transistor S i2 Forming a bridge arm, the switching transistor S i3 and switching transistor S i4 This forms another bridge arm.

[0038] Depend on Figure 1 As can be seen, the LC filter consists of the output-side inductor L s and output-side filter capacitor C s Composition. Additionally, from Figure 1 It can be seen that each H-bridge unit also includes an input-side filter capacitor C connected in parallel with the H-bridge. i One is the output-side filter capacitor C. i parallel DC power supply V i Additionally, R o For the output side load.

[0039] The electrical parameters for this invention are set as follows: f0 = 60Hz. The voltage at DC power supply V0 in the main H-bridge unit is 220V, and the input-side filter capacitor C0 is 1000uF. The DC power supply V0 in the H-bridge unit... i The value is 220V, and the input-side filter capacitor C i The value is 1000uF. Output side inductor L s The value is 1.62mH, and the output-side filter capacitor C s The value is 1uF, and the value of the output load R0 is 20Ω.

[0040] Figure 2 This is a block diagram of power line carrier communication based on harmonic injection in an embodiment of the present invention. Figure 2 As shown, the communication method achieves signal modulation by injecting harmonics into the drive signal of the switching transistor and demodulation by performing FFT operations on the acquired current signal, including the following steps:

[0041] Step 1: Setting the baseband signal and harmonic signal

[0042] The original signal that the cascaded H-bridge needs to transmit is denoted as the baseband signal, which is a square wave signal with a period of T.B The signal with frequency λf0 is denoted as the injected harmonic signal, where λ is the order of the harmonic and f0 is the frequency of the carrier signal.

[0043] The high and low levels in the baseband signal correspond to the digital signal to be transmitted. When the baseband signal is high, the digital signal transmitted by the cascaded H-bridge is "1", and when the baseband signal is low, the digital signal transmitted by the cascaded H-bridge is "0".

[0044] Step 2, Determining the signal transmitting end and the signal receiving end

[0045] When the main H-bridge unit sends a signal, the main H-bridge unit is the transmitter, and all the slave H-bridge units are the receivers; when any one of the n slave H-bridge units sends a signal, the slave H-bridge unit that sends the signal is the transmitter, and the main H-bridge unit is the receiver.

[0046] Step 3, Modulation of the driving signal

[0047] Switch S ij The driving signal is denoted as driving signal G. ij The specific modulation includes:

[0048] (1) When the baseband signal is low level

[0049] When the main H-bridge unit is used as the transmitting short end, it outputs four SPWM signals with a frequency of f0, which are used as switching transistors S... 01 Switch S 02 Switch S 03 and switching transistor S 04 The drive signal, at this time the drive signal G 01 With G 02 Complementary, driving signal G 03 With drive signal G 04 Complementary, driving signal G 01 With drive signal G 04 Same direction;

[0050] When the H-bridge unit is used as the transmitting end, each of the n H-bridge units sends out four SPWM signals with a frequency of f0, which serve as the corresponding switching transistors S. i1 Switch S i2 Switch S i3 and switching transistor S i4 The drive signal, at this time the drive signal G i1 With G i2 Complementary, driving signal G i3 With drive signal G i4 Complementary, driving signal G i1 With drive signal G i4 Same direction;

[0051] (2) When the baseband signal is high level

[0052] When the main H-bridge unit is used as the transmitting short end, a harmonic with frequency λf0 is injected into the driving signal G of the main H-bridge unit. 0j In this process, the drive signals of the switching transistors in other H-bridge units remain unchanged;

[0053] When a slave H-bridge unit acts as a transmitter, a harmonic with frequency λf0 is injected into the drive signal G of that slave H-bridge unit acting as the transmitter. ij In this process, the drive signals of the switching transistors in other H-bridge units remain unchanged;

[0054] Step 4: Acquire current and demodulate it.

[0055] The current at the receiving end is collected, and the amplitude Sp of the signal carrier with frequency λf0 is obtained after FFT operation. The average value of the maximum frequency value F1 and the minimum frequency value F2 of the signal carrier when harmonics are injected is set as the reference value a. The signal is judged and transmitted according to the following rules:

[0056] When Sp < a, the sent signal is determined to be "0", and a low-level signal is output.

[0057] When Sp > a, the sent signal is determined to be "1", and a high-level signal is output.

[0058] exist Figure 2 In this circuit, the main H-bridge unit acts as the transmitter, and all the slave H-bridge units act as receivers. The input current of the slave H-bridge units is sampled. The driving circuit refers to the hardware circuit that drives the switching transistor.

[0059] Figure 3 This is a comparison diagram of the input and output signal waveforms in an embodiment of the present invention. For example... Figure 3 As shown, the output signal waveform is a square wave with a fixed period, indicating that the transmitted digital signal was successfully demodulated. The output signal waveform has a delay time t compared to the input signal waveform. This delay time is mainly affected by the sampling time, FFT operation time, and comparison / demodulation time. Furthermore, the delay time is a fixed constant when the system reaches steady state, and its influence can be eliminated through delay compensation.

Claims

1. A cascaded H-bridge power line carrier communication method based on harmonic injection, wherein the cascaded H-bridge consists of n+1 identical H-bridge units, wherein, One H-bridge unit is designated as the master H-bridge unit, and the other n are designated as slave H-bridge units. The n+1 H-bridge units are cascaded and connected to the output load through an LC filter. Each H-bridge unit includes one H-bridge, and each H-bridge includes four switching transistors with anti-parallel diodes, denoted as switching transistor S. ij i is the sequence number of the H-bridge unit, i = 0, 1, ..., n, where the sequence number of the main H-bridge unit is 0, j is the sequence number of the switching transistor, j = 1, 2, 3, 4; the switching transistor S i1 and switching transistor S i2 Forming a bridge arm, the switching transistor S i3 and switching transistor S i4 Forming another bridge arm; The communication method is characterized in that signal modulation is achieved by injecting harmonics into the drive signal of the switching tube, and signal demodulation is achieved by performing FFT operation on the collected current signal, comprising the following steps: Step 1: Setting of baseband signal and harmonic signal The original signal that the cascaded H-bridge needs to transmit is denoted as the baseband signal, which is a square wave signal with a period of T. B The signal with frequency λf0 is denoted as the injected harmonic signal, where λ is the order of the harmonic and f0 is the frequency of the carrier signal. The high and low levels in the baseband signal correspond to the digital signal to be transmitted; when the baseband signal is at a high level, the digital signal transmitted by the cascaded H-bridge is "1", and when the baseband signal is at a low level, the digital signal transmitted by the cascaded H-bridge is "0"; Step 2: Determination of the signal transmitting end and the signal receiving end When the master H-bridge unit transmits a signal, the master H-bridge unit is the transmitting end, and all the slave H-bridge units are the receiving ends; when any one of the n slave H-bridge units transmits a signal, the slave H-bridge unit that transmits the signal is the transmitting end, and the master H-bridge unit is the receiving end; Step 3: Modulation of the drive signal Switch S ij The driving signal is denoted as driving signal G. ij The specific modulation includes: (1) When the baseband signal is at a low level When the main H-bridge unit is used as the transmitting short end, it outputs four SPWM signals with a frequency of f0, which are used as switching transistors S... 01 Switch S 02 Switch S 03 and switching transistor S 04 The drive signal, at this time the drive signal G 01 With G 02 Complementary, driving signal G 03 With drive signal G 04 Complementary, driving signal G 01 With drive signal G 04 Same direction; When the H-bridge unit is used as the transmitting end, each of the n H-bridge units sends out four SPWM signals with a frequency of f0, which serve as the corresponding switching transistors S. i1 Switch S i2 Switch S i3 and switching transistor S i4 The drive signal, at this time the drive signal G i1 With G i2 Complementary, driving signal G i3 With drive signal G i4 Complementary, driving signal G i1 With drive signal G i4 Same direction; (2) When the baseband signal is at a high level When the main H-bridge unit is used as the transmitting short end, a harmonic with frequency λf0 is injected into the driving signal G of the main H-bridge unit. 0j In this process, the drive signals of the switching transistors in other H-bridge units remain unchanged; When a slave H-bridge unit acts as a transmitter, a harmonic with frequency λf0 is injected into the drive signal G of that slave H-bridge unit acting as the transmitter. ij In this process, the drive signals of the switching transistors in other H-bridge units remain unchanged; Step 4: Collecting current and performing demodulation Collect the current at the receiving end, obtain the time-domain amplitude Sp of the signal carrier with the frequency of λf0 after FFT operation, set the average value of the maximum frequency domain value F1 of the signal carrier and the minimum frequency domain value F2 of the signal carrier when the harmonic is injected as the reference value a, and judge and transmit the signal according to the following rules: When Sp < a, the transmitted signal is judged to be "0", and a low level signal is output; When Sp > a, the transmitted signal is judged to be "1", and a high level signal is output.

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