A micro-grid channel capacity analysis and power coordination control method based on energy coherence

Abstract

The application discloses a micro-grid channel capacity analysis and power collaborative control method based on energy signal coherence; the method collects output current information of a local power converter, converts the output current information into information signals, and superimposes the information signals into a voltage reference signal or a power control reference quantity; a direct-current bus channel capacity model oriented to energy signal coherence is established, frequency configuration, bandwidth configuration, filtering parameters and the number of access nodes of the information signals are determined according to the analysis result of the channel capacity; remote current information of other converters is recovered from a direct-current bus voltage ripple at a receiving end, and a droop control loop is introduced to modify the local voltage reference quantity or the power control reference quantity, so that real-time power collaborative control and accurate current sharing are realized. The application establishes the direct-current bus channel capacity model, provides a theoretical basis for parameter configuration of energy signal coherence information transmission and reliable recovery of remote current information, improves information transmission reliability, control real-time performance and current sharing control accuracy under the premise that no additional communication hardware is needed.

Description

Technical Field

[0001] This invention relates to the fields of communication technology and power control, specifically to a method for channel capacity analysis and power coordinated control of microgrids based on energy and information synchronization, particularly a method for synchronous control and transmission of energy and information for multi-user communication in DC microgrids. Background Technology

[0002] Building a low-carbon and efficient new power system has become an important measure to achieve the "dual-carbon" strategic goal. Power electronic equipment, through controllable AC / DC conversion, serves as the energy conversion hub connecting power sources, loads, energy storage, and the power grid. It not only supports the access and grid connection of various clean energy sources but also enables rapid response to grid faults, optimizes power resource allocation, and improves energy utilization efficiency. Therefore, power electronic equipment has become the most critical basic equipment in the new power system.

[0003] In new power systems, achieving state awareness, fault monitoring, and energy management is fundamental to ensuring efficient and stable operation. Currently, information exchange in power electronic equipment mainly relies on independent communication technologies, such as fieldbus, Ethernet, and radio frequency communication. These technologies require additional communication equipment (such as signal transceivers and communication cables) and data transmission through communication interface circuits. The separation of the energy system and communication system architecture leads to problems such as high cost, large size, and asynchrony between energy flow and information flow, making it difficult to meet the inherently safe and efficient communication requirements of new power systems.

[0004] Power electronic energy-information co-modulation technology proposes a novel information interaction method. It relies on the inherent modulation characteristics of power electronic equipment to achieve synchronous information transmission while controlling and transmitting energy. This technology breaks the dependence of traditional communication architectures on external devices, thus constructing a highly efficient, low-cost, and inherently secure communication mechanism. While some research has been conducted at the equipment level, a comprehensive solution for the efficient coordinated transmission of energy and information among multiple users in a microgrid, considering the overall picture, is still lacking. Furthermore, although existing research has made progress in the field of power electronic energy-information co-modulation, a complete information theory framework has not yet been established.

[0005] A comparative analysis of patent CN117318763A reveals that it proposes a power inverter energy-information co-modulation method based on drive pulse position. This method selects different zero-vector positions according to the symbols of the information to be transmitted, and generates an embedded information PWM carrier through variable zero-vector position modulation to achieve coordinated energy and information transmission. However, this method suffers from small and uncontrollable amplitudes of the information components, making long-distance information transmission impossible and information demodulation difficult. Furthermore, relying solely on a single pulse position modulation method is not conducive to multi-user communication.

[0006] A comparison with patent CN118983881A reveals that it proposes a control method for a grid-connected inverter with synchronized signaling and communication capabilities. In this method, the inverter controller transmits information-carrying voltage harmonics via a droop control strategy, enabling another inverter to receive the corresponding data. Furthermore, different frequency components are distinguished and extracted through filter design. However, this research does not consider frequency utilization optimization, making it difficult to efficiently utilize limited frequency resources. Additionally, it lacks a method for evaluating communication quality, thus failing to comprehensively verify the long-term reliability of the communication system.

[0007] The technical advantages of this invention are mainly reflected in two dimensions: energy analysis of information transmission based on energy-information co-modulation technology and real-time control based on energy-information co-modulation transmitted information. This patent establishes a complete channel capacity model through the switching characteristics of deeply coupled converters, filter amplitude-frequency response, and information theory principles, scientifically defining the effective information transmission boundary of energy-information co-modulation at the physical layer, providing precise theoretical guidance for the optimal allocation of spectrum resources. Secondly, this invention directly introduces the demodulated real-time current information from the remote end into the improved droop control loop, achieving precise current sharing in the parallel system using the power flow channel without requiring additional physical communication links. Summary of the Invention

[0008] The purpose of this invention is to propose a microgrid channel capacity analysis and power coordination control method based on energy-communication co-modulation, so as to fill the gap in the existing energy-communication co-modulation method which lacks multi-user communication channel capacity analysis, expand the application field of energy-communication co-modulation technology, and promote the engineering application value of energy-communication co-modulation technology.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows;

[0010] Step S1: Signal modulation and coherence embedding

[0011] The baseband digital signal is modulated to generate an information carrier signal s(t). Then, the information carrier signal s(t) is modulated with the reference voltage v output by the power modulation module. ref (t) Linear superposition generates a composite signal v ps (t); Finally, the composite signal v ps (t) and triangular carrier v tri (t) compares to generate a gate drive signal g(t), which is then transmitted through the converter output ripple;

[0012] Step S2: Channel capacity modeling and communication parameter configuration based on Shannon's theorem

[0013] Based on Shannon's theorem, and combining the switching frequency of the power converter, the frequency response of the LC filter, and the inter-carrier interference (ICI) among multiple users, a DC bus channel capacity model is established. Based on the channel capacity analysis results, the frequency configuration, bandwidth configuration, filtering parameters, and number of access nodes of the information signal are determined.

[0014] First, the channel noise is analyzed. At the information receiving end of the DC microgrid parallel system, the output DC voltage is sampled and analyzed, and the system noise is equivalently modeled as Gaussian noise. The probability density function of the noise is:

[0015]

[0016] in, Let be the possible values ​​of the noise random variable. The noise mean is... This represents noise power.

[0017] The channel noise power P is:

[0018]

[0019] Wherein, E[n 2 [(t)] represents the mathematical expectation of the square of the noise signal.

[0020] Secondly, the spectrum and energy of the output signal are analyzed by combining the switching characteristics and low-pass filtering characteristics of the power converter.

[0021] In pulse width modulation (PWM) process, the power / signal composite reference signal is represented as: By using double Fourier series expansion, the output voltage u can be obtained. o The spectrum of (t):

[0022] ;

[0023]

[0024]

[0025] Where E is the DC input voltage and D0 is the steady-state duty cycle. It is the signal modulation depth, defined as ,in For information carrier amplitude, The peak value of the triangular wave carrier; yes First-order Bessel function of the first kind; It is the angular frequency of the signal carrier. It is the first The initial phase corresponding to each symbol; It is the switching angular frequency of the converter; It is the harmonic order of the switching frequency. It is the order of the sideband harmonics of the signal frequency.

[0026] A power converter can be equivalently represented as a combination of switching devices and a low-pass filter. Therefore, higher harmonics in the output voltage will be significantly attenuated. Thus, the output voltage ripple can be simplified as follows:

[0027]

[0028] in, It is a simplified output voltage ripple signal;

[0029] Frequency domain analysis using cyclic spectral density yields the following spectral density expression for the signal:

[0030]

[0031] in, It is the duration of the symbol; It is the signal carrier frequency; It is the power spectral density of the MPSK modulated signal.

[0032] Based on the frequency response of the LC filter, calculate the effective signal energy finally transmitted to the DC bus. :

[0033]

[0034] in, It is the effective signal energy after being processed by the filter; It is the amplitude-frequency response gain of the LC filter.

[0035] Filter transfer function satisfy:

[0036]

[0037] in, It is a filter inductor; It is a filter capacitor; It is the load equivalent resistance.

[0038] To quantify the mutual influence between adjacent subcarriers in multi-user concurrent scenarios, this invention introduces a frequency spacing factor. Modeling and analysis of inter-carrier interference (ICI) are performed.

[0039] The frequency interval between the center frequencies of adjacent subcarriers is set as follows: Its expression is:

[0040]

[0041] in, The normalized frequency spacing factor, The symbol duration of the data frame.

[0042] The interference power is calculated by integrating the power spectral density of the interference signal falling within the target sub-channel frequency band. for:

[0043]

[0044] in: For the first Signal power spectral density of adjacent interfering nodes; This represents the passband frequency range of the bandpass filter for the target receiving channel, corresponding to the main lobe interval of the target signal power spectrum.

[0045] The calculated interference power Substituting into the channel capacity model, we obtain the single-channel capacity considering multi-user interference. :

[0046]

[0047] in, This represents the number of other interfering users simultaneously transmitting in the system.

[0048] The center frequency of the subcarrier and the frequency spacing between adjacent subcarriers are determined based on the target subchannel capacity. The center frequency and passband range of the receiver bandpass filter are determined based on the main lobe bandwidth of the target signal. The number of converters that can be accessed simultaneously is determined based on the capacity threshold and the inter-carrier interference level, so as to ensure that the modulation at the transmitter, the demodulation at the receiver, and the recovery of the remote current information meet the preset communication quality requirements.

[0049] Step S3: Information processing and energy-information synchronization transmission of local current information

[0050] Converting local output current information into an information signal for power cooperative control includes: quantizing and encoding the local output current information, and performing framing processing according to communication reliability requirements to form an information data frame for modulation; the information data frame includes a data field for characterizing the local output current information, and may further include one or more of a synchronization field, node identifier field, check field, error correction field, or frame boundary identifier field, to support the receiver in reliably recovering the output current information of the corresponding converter from the DC bus voltage ripple.

[0051] Information signals from different power converters are distinguished by a preset signal differentiation method, which includes one or more of frequency division multiplexing, time division multiplexing, code division multiplexing, or different disturbance feature configurations.

[0052] In one implementation, a frequency division multiplexing-binary phase shift keying (FDM-BPS) method can be used, where at the transmitting end, the system allocates non-overlapping subcarrier frequencies to each converter. It employs binary phase shift keying (2PSK) modulation technology to modulate local current information onto controlled subcarriers. Above, generate communication information signals. ,in Represents the initial phase determined by the data bits; modulated signal The voltage reference signal is directly superimposed on the converter as a disturbance. In this process, a controlled voltage ripple containing specific frequency information is generated through PWM control. At the receiving end, it is sampled from the DC bus voltage signal, using a center frequency of... The bandpass filter (BPF) extracts the controlled ripple component corresponding to the target subcarrier, filtering out DC bias, low-frequency power fluctuations, and interference from adjacent channels; coherent carriers with the same frequency and phase as the local carrier. Multiplication is performed, the baseband signal is extracted by low-pass filtering and then sampled and decided to achieve demodulation and restoration of multi-user information.

[0053] Step S4: Real-time control of DC microgrid based on energy and information synchronization transmission information

[0054] The improved droop control law formula used in flow sharing control is as follows:

[0055]

[0056] in, This represents the actual output voltage values ​​of the first and second parallel converters; This indicates the reference value of the rated no-load voltage of the DC bus; This represents the traditional droop control coefficient, used to initially maintain voltage stability. This represents the output current value collected in real time by the local sensors of each converter; This represents the current sharing compensation gain coefficient, which determines the strength of the system's correction to current deviation. The amount of co-modulation information refers to the current value of adjacent units recovered by demodulating the controlled ripple of the DC bus.

[0057] The remote current information It does not originate from an additional physical communication interface or a dedicated communication module, but is obtained directly by demodulating the controlled ripple signal generated by the power switching action of adjacent converters in the bus voltage; that is, it uses the inherent power conversion hardware of the converter as the signal transmission and reception carrier, and separates the information flow from the power flow through the demodulation algorithm.

[0058] This control method adjusts the compensation gain. This ensures that the current distribution ratio among the parallel units satisfies:

[0059]

[0060] in, and The equivalent line impedance of the parallel unit connected to the bus; when the gain As the ratio increases, it approaches 1, thus eliminating the current imbalance caused by line impedance mismatch without relying on external communication hardware such as CAN, RS485, or Ethernet.

[0061] Compared with the prior art, the present invention has the following beneficial effects:

[0062] 1. This invention establishes a complete channel capacity model by utilizing the switching characteristics of deeply coupled converters, the amplitude-frequency response of filters, and the principles of information theory. It scientifically defines the effective information transmission boundary of energy-information-coherence at the physical layer, providing precise theoretical guidance for the optimal allocation of spectrum resources.

[0063] 2. This invention directly introduces the demodulated remote real-time current information into the improved droop control loop, and completes accurate current sharing of the parallel system using the power flow channel without the need for an additional physical communication link; Attached Figure Description

[0064] The following accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the invention and do not constitute a limitation thereof. In the drawings, the same reference numerals generally represent the same components or steps.

[0065] Figure 1 A schematic diagram of a multi-source, multi-load power network is shown.

[0066] Figure 2 A schematic diagram of ripple-controlled energy-information dual modulation is shown;

[0067] Figure 3 A schematic diagram of the Gaussian distribution of noise is shown;

[0068] Figure 4The diagram illustrates the channel capacity analysis of co-location in a multi-user scenario; (a) the impact of the number of users and frequency spacing factor on channel capacity; and (b) different frequency spacing factors. (c) The effect of signal bandwidth and frequency spacing factor on channel capacity; (d) Different numbers of interfering users (e) The effect of signal bandwidth and frequency spacing factor on spectral efficiency; (f) The relationship between spectral efficiency and frequency spacing factor under different signal bandwidths.

[0069] Figure 5 A diagram of the data transmission frame format is shown;

[0070] Figure 6 A schematic diagram of the coherent demodulation method is shown;

[0071] Figure 7 A model diagram of the parallel system is shown;

[0072] Figure 8 The following diagrams show the bus voltage ripple and spectrum analysis: (a) Bus voltage ripple; (b) Bus voltage spectrum analysis.

[0073] Figure 9 The following diagrams show the modulation and demodulation of information from different voltage sources: (a) modulation and demodulation of DC1; (b) modulation and demodulation of DC2.

[0074] Figure 10 The current sharing performance of two voltage sources under line impedance mismatch is shown in the diagram.

[0075] Figure 11 A flowchart of the method of the present invention is shown. Detailed Implementation

[0076] To make the objectives, technical solutions, and advantages of the present invention more apparent, exemplary embodiments according to the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely a part of the embodiments of the present invention, and not all of the embodiments of the present invention. It should be understood that the present invention is not limited to the exemplary embodiments described herein. Based on the embodiments of the present invention described herein, all other embodiments obtained by those skilled in the art without inventive effort should fall within the protection scope of the present invention.

[0077] According to an embodiment of the present invention, a method for microgrid channel capacity analysis and power coordinated control based on energy and information co-regulation is provided, the steps of which are as follows: Figure 11 As shown.

[0078] like Figure 1As shown, a DC microgrid consists of multiple power supply units, load units, and a common DC bus. Each node is connected to the bus through a power converter, and while completing energy transmission, it also has the ability to embed and interact with information.

[0079] Step S1: Signal modulation and coherence embedding

[0080] like Figure 2 As shown, the baseband digital signal is modulated to generate an information carrier signal s(t). Then, the information carrier signal s(t) is modulated with the reference voltage v output by the power modulation module. ref (t) Linear superposition generates a composite signal v ps (t). Finally, the composite signal v ps (t) and triangular carrier v tri The gate drive signal g(t) is generated by comparison (t), and the information is transmitted through the output ripple of the converter.

[0081] Step S2: Channel capacity modeling and spectrum optimization based on Shannon's theorem

[0082] Based on Shannon's theorem, and combining the switching frequency of the power converter, the frequency response of the LC filter, and the inter-carrier interference (ICI) among multiple users, a DC bus channel capacity model is established. Based on the channel capacity analysis results, the frequency configuration, bandwidth configuration, filtering parameters, and number of access nodes of the information signal are determined.

[0083] First, channel noise is analyzed. At the information receiver of the multi-source, multi-load power system, the output DC voltage is sampled and analyzed, and the system noise is equivalently modeled as Gaussian noise, such as... Figure 3 As shown. The probability density function of this noise is:

[0084]

[0085] in, Let be the possible values ​​of the noise random variable. The noise mean is... This represents noise power.

[0086] The channel noise power P is:

[0087]

[0088] Wherein, E[n 2 [(t)] represents the mathematical expectation of the square of the noise signal.

[0089] Secondly, the spectrum and energy of the output signal are analyzed by combining the switching characteristics and low-pass filtering characteristics of the power converter.

[0090] In pulse width modulation (PWM) process, the power / signal composite reference signal is represented as: By using double Fourier series expansion, the output voltage u can be obtained. o Spectrum of (t)

[0091] ;

[0092]

[0093]

[0094] Where E is the DC input voltage and D0 is the steady-state duty cycle. It is the signal modulation depth, defined as ,in For information carrier amplitude, The peak value of the triangular wave carrier; yes First-order Bessel function of the first kind; It is the angular frequency of the signal carrier. It is the first The initial phase corresponding to each symbol; It is the switching angular frequency of the converter; It is the harmonic order of the switching frequency. It is the order of the sideband harmonics of the signal frequency.

[0095] A power converter can be equivalently represented as a combination of switching devices and a low-pass filter. Therefore, higher harmonics in the output voltage will be significantly attenuated. Thus, the output voltage ripple can be simplified as follows:

[0096]

[0097] in, It is a simplified output voltage ripple signal;

[0098] Frequency domain analysis is performed using cyclic spectral density. The spectral density of this signal can be expressed in the following form:

[0099]

[0100] in, It is the duration of the symbol; It is the signal carrier frequency; It is the power spectral density of the MPSK modulated signal.

[0101] Based on the frequency response of the LC filter, calculate the effective signal energy finally transmitted to the DC bus. :

[0102]

[0103] in, It is the effective signal energy after being processed by the filter; It is the amplitude-frequency response gain of the LC filter.

[0104] Filter transfer function satisfy:

[0105]

[0106] in, It is a filter inductor; It is a filter capacitor; It is the load equivalent resistance.

[0107] To quantify the mutual influence between adjacent subcarriers in multi-user concurrent scenarios, this invention introduces a frequency spacing factor. Modeling and analysis of inter-carrier interference (ICI) are performed.

[0108] The frequency interval between the center frequencies of adjacent subcarriers is set as follows: Its expression is:

[0109]

[0110] in, The normalized frequency spacing factor, The symbol duration of the data frame.

[0111] The interference power is calculated by integrating the power spectral density of the interference signal falling within the target sub-channel frequency band. for:

[0112]

[0113] in: For the first Signal power spectral density of adjacent interfering nodes; This represents the passband frequency range of the bandpass filter for the target receiving channel, corresponding to the main lobe interval of the target signal power spectrum.

[0114] The calculated interference power Substituting into the channel capacity model, we obtain the single-channel capacity considering multi-user interference. :

[0115]

[0116] in, This represents the number of other interfering users simultaneously transmitting in the system.

[0117] like Figure 4 As shown, under multi-user concurrent transmission conditions, channel capacity is affected by factors such as the number of users, frequency spacing factor, and signal bandwidth. As the spacing between adjacent subcarriers increases, inter-carrier interference is significantly reduced, and channel capacity is improved. However, spectral efficiency does not increase monotonically; rather, there is a trade-off between capacity and spectral overhead.

[0118] In practical implementation, firstly, based on the switching frequency of the power converter, LC filter parameters, bus voltage ripple characteristics, and a preset information signal frequency range, several candidate signal configurations are selected. These candidate signal configurations include candidate frequency points, candidate bandwidths, candidate filter parameters, and the number of candidate access nodes. Then, the effective signal energy after attenuation by the LC filter under each candidate signal configuration is calculated. Combined with the sampled bus noise power and the interference power during multi-user concurrent transmission, the signal-to-noise ratio (SNR) and channel capacity under the corresponding configuration are obtained. Further, constrained by the minimum transmission rate, allowable bit error rate, and control update cycle required for reliable recovery of remote current information, signal configurations that meet the capacity requirements are selected. Finally, based on the selection results, the frequency configuration, bandwidth configuration, receiver filter parameters, and the number of power converters allowed to access simultaneously are determined, ensuring that the recovery of remote current information meets the communication reliability and real-time requirements of power collaborative control.

[0119] In one implementation, when the information signals of different power converters are distinguished using frequency division multiplexing, the center frequency of the subcarriers corresponding to each power converter and the frequency spacing between adjacent subcarriers can be selected based on the target subchannel capacity and spectral efficiency analysis results; the center frequency and passband range of the receiver bandpass filter can be determined based on the main lobe bandwidth of the signal; and the symbol period, modulation scheme, and the number of converters allowed to access simultaneously can be determined based on the capacity threshold and inter-carrier interference level. Therefore, the channel capacity analysis results can be used to guide the modulation of the transmitting end information signal, the extraction and demodulation of the receiving end target information, and ensure the accuracy of the recovery of the far-end current information required in subsequent droop control.

[0120] Step S3: Information processing and energy-information synchronization transmission of local current information

[0121] First, the local output current information is quantized and encoded, and then framed according to communication reliability requirements to form an information data frame for modulation. As one implementation method, such as... Figure 5 As shown, the data frame consists of a synchronization segment, a data segment, a check segment, and a frame end symbol. The data segment carries a 5-bit binary code stream linearly mapped from the measured current, enabling real-time transparent transmission of information via the DC bus. In one implementation, the check field can use even parity to check the data segment; in other implementations, cyclic redundancy check, error correction coding, or other check methods can be used to improve the reliability of remote current information recovery.

[0122] In one implementation, frequency division multiplexing-binary phase shift keying (FDM) can be used, such as... Figure 6 As shown, at the transmitting end, the system allocates non-overlapping subcarrier frequencies to each converter. It employs binary phase shift keying (2PSK) modulation technology to modulate local current information onto controlled subcarriers. Above, generate communication information signals. ,in Represents the initial phase determined by the data bits; modulated signal The voltage reference signal is directly superimposed on the converter as a disturbance. In this process, a controlled voltage ripple containing specific frequency information is generated through PWM control. At the receiving end, it is sampled from the DC bus voltage signal, using a center frequency of... The bandpass filter (BPF) extracts the controlled ripple component corresponding to the target subcarrier, filtering out DC bias, low-frequency power fluctuations, and interference from adjacent channels; coherent carriers with the same frequency and phase as the local carrier. Multiplication is performed, the baseband signal is extracted by low-pass filtering and then sampled and decided to achieve demodulation and restoration of multi-user information.

[0123] It should be noted that the above frequency division multiplexing-binary phase shift keying method is only one specific embodiment and does not constitute a limitation on the information signal differentiation method and modulation method; those skilled in the art can also use time division multiplexing, code division multiplexing, different perturbation frequencies, different perturbation phases or different perturbation codes, etc., to achieve multi-converter information differentiation according to the number of access nodes, channel capacity analysis results and control real-time requirements.

[0124] Step S4: Real-time control of DC microgrid based on energy and information synchronization transmission information

[0125] like Figure 7 As shown, a parallel system consists of multiple converters connected to a common bus and load via their respective line impedances. Inconsistent line impedances can lead to current distribution imbalance under traditional droop control. The following example, using two parallel converters, illustrates the current sharing control process based on remote current information. Those skilled in the art can extend the control method to scenarios with multiple parallel converters.

[0126] The improved droop control law formula used in flow sharing control is as follows:

[0127]

[0128] in, This represents the actual output voltage values ​​of the first and second parallel converters; This indicates the reference value of the rated no-load voltage of the DC bus; This represents the traditional droop control coefficient, used to initially maintain voltage stability. This represents the output current value collected in real time by the local sensors of each converter; This represents the current sharing compensation gain coefficient, which determines the strength of the system's correction to current deviation. The amount of co-modulation information refers to the current value of adjacent units recovered by demodulating the controlled ripple of the DC bus.

[0129] The remote current information It does not originate from an additional physical communication interface or a dedicated communication module, but is obtained directly by demodulating the controlled ripple signal generated by the power switching action of adjacent converters in the bus voltage; that is, it uses the inherent power conversion hardware of the converter as the signal transmission and reception carrier, and separates the information flow from the power flow through the demodulation algorithm.

[0130] This control method adjusts the compensation gain. This ensures that the current distribution ratio among the parallel units satisfies:

[0131]

[0132] in, and The equivalent line impedance of the parallel unit connected to the bus; when the gain As the ratio increases, it approaches 1, thus eliminating the current imbalance caused by line impedance mismatch without relying on external communication hardware such as CAN, RS485, or Ethernet.

[0133] To verify the effectiveness of the proposed energy-information-coordinated current sharing control method, the experimental results are analyzed from three aspects: the controlled ripple characteristics of the bus, the information transmission capability of multiple power sources, and the current sharing control performance.

[0134] like Figure 8 As shown in (a), the bus voltage ripple clearly contains a controlled communication component; as Figure 8 As shown in (b), the main peak of its spectrum is concentrated near the preset subcarrier, indicating that the information signal has been successfully embedded into the converter output ripple.

[0135] like Figure 9 As shown, the information corresponding to different voltage sources is modulated and demodulated on their respective independent subcarriers, and the waveforms at the transmitting and receiving ends correspond well, indicating that the information of each node in a multi-user scenario can be transmitted in parallel on a shared DC bus without significant aliasing.

[0136] like Figure 10As shown, under the condition of line impedance mismatch, the improved droop control after introducing remote current information compensation can significantly improve the consistency of current distribution among parallel units, so that the current in each branch gradually converges to a similar level. Experimental results show that the proposed energy-information coherence current sharing control method can achieve high-precision current sharing in parallel systems without the need for additional physical communication links.

[0137] Although exemplary embodiments have been described herein with reference to the accompanying drawings, it should be understood that the above exemplary embodiments are merely illustrative and are not intended to limit the scope of the invention. Various changes and modifications can be made therein by those skilled in the art without departing from the scope and spirit of the invention. All such changes and modifications are intended to be included within the scope of the invention as claimed in the appended claims.

[0138] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed. For example, the bidirectional power electronic converter is merely a functional illustration, and in actual implementation, multiple power electronic converters may be combined to achieve a certain function.

[0139] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0140] Similarly, it should be understood that, in order to streamline the invention and aid in understanding one or more of the various aspects of the invention, features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof in the description of exemplary embodiments of the invention. However, this approach should not be construed as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the corresponding claims, its inventive point lies in solving the corresponding technical problem with fewer features than all of those in a single disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0141] Those skilled in the art will understand that, apart from the mutual exclusion of features, all features disclosed in this specification (including the accompanying claims, abstract, and drawings) and all processes or elements of any method or apparatus so disclosed may be combined in any combination. Unless otherwise expressly stated, each feature disclosed in this specification (including the accompanying claims, abstract, and drawings) may be replaced by an alternative feature that serves the same, equivalent, or similar purpose.

[0142] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features but not others included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments. For example, in the claims, any of the claimed embodiments can be used in any combination.

[0143] The above description is merely a specific embodiment of the present invention or an explanation of that embodiment. The scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A microgrid channel capacity analysis and power coordinated control method based on energy and information co-regulation, characterized in that, Includes the following steps: S1: Using power / signal dual modulation technology, the information to be transmitted is modulated to form an information signal, and the information signal is superimposed on the voltage reference signal or power control reference quantity of the power converter. After the modulation carrier is compared, a switching drive signal is generated, thereby embedding the information into the output voltage ripple of the converter. S2: Based on Shannon's theorem, combined with the switching frequency of the power converter, the frequency response of the LC filter, and the inter-carrier interference among multiple users, a DC bus channel capacity model is established. Based on the channel capacity analysis results, the frequency configuration, bandwidth configuration, filtering parameters, and number of access nodes of the information signal are determined to guide the information embedding at the transmitting end, the extraction of target information at the receiving end, and the recovery of remote current information, so that the recovered remote current information meets the communication reliability and real-time requirements of power cooperative control. S3: Collect the output current information of the local power converter and convert it into an information signal for power cooperative control; based on the power / signal dual modulation method, the local output current information is coupled to the DC bus voltage ripple during the power conversion process, realizing real-time information transmission without additional communication hardware; S4: The receiving end recovers the remote current information of other converters from the DC bus voltage ripple and introduces the remote current information into the droop control loop to correct the local voltage reference or power control reference, so as to realize real-time power coordinated control and accurate current sharing of multiple converters in the parallel microgrid, without the need to set up additional communication hardware.

2. The microgrid channel capacity analysis and power coordinated control method based on energy and information co-modulation as described in claim 1, characterized in that, Step S1 specifically involves: The baseband digital signal is modulated to generate an information carrier signal s(t); The information carrier signal s(t) is compared with the reference voltage v output by the power modulation module. ref (t) Linear superposition generates a composite signal v ps (t); The composite signal v ps (t) and triangular carrier v tri The gate drive signal g(t) is generated by comparison (t), and the information is transmitted through the output ripple of the converter.

3. The microgrid channel capacity analysis and power coordinated control method based on energy and information co-modulation as described in claim 1, characterized in that, Before establishing the DC bus channel capacity model in step S2, channel noise analysis of the DC microgrid parallel system needs to be performed, including: The noise in a multi-source, multi-load power system mainly originates from the ripple of high-frequency switching of power electronic switches, dynamic interference from MPPT and energy management, inherent device noise, environmental white noise, and cross-interference generated by the interaction of multiple units. At the information receiving end of the multi-source, multi-load power system, the output DC voltage is sampled and analyzed, and the system noise is equivalently modeled as Gaussian noise. The probability density function of the noise is: in, Let be the possible values ​​of the noise random variable. The noise mean. Noise power; The channel noise power P is: Wherein, E[n 2 [(t)] represents the mathematical expectation of the square of the noise signal.

4. The microgrid channel capacity analysis and power coordinated control method based on energy and information co-modulation as described in claim 1, characterized in that, The method for characterizing the transmitted signal power in the DC bus channel capacity analysis in step S2 is as follows: During pulse width modulation, the power / signal composite reference signal is represented as: By using double Fourier series expansion, the output voltage u can be obtained. o The spectrum of (t): Where E is the DC input voltage and D0 is the steady-state duty cycle. It is the signal modulation depth, defined as ,in For information carrier amplitude, The peak value of the triangular wave carrier; yes First-order Bessel function of the first kind; It is the angular frequency of the signal carrier. It is the first The initial phase corresponding to each symbol; It is the switching angular frequency of the converter; It is the harmonic order of the switching frequency. It is the order of the sideband harmonics of the signal frequency; The power converter can be equivalently represented as a combination of switching devices and a low-pass filter, and the output voltage ripple can be simplified as follows: in, It is a simplified output voltage ripple signal; Using cyclic spectral density, the spectral density of this signal can be expressed in the following form. in, It is the duration of the symbol; It is the signal carrier frequency; It is the power spectral density of the MPSK modulated signal; Based on the frequency response of the LC filter, calculate the effective signal energy finally transmitted to the DC bus. : in, It is the effective signal energy after being processed by the filter; It is the amplitude-frequency response gain of the LC filter; Filter transfer function satisfy: in, It is a filter inductor; It is a filter capacitor; It is the load equivalent resistance.

5. The microgrid channel capacity analysis and power coordinated control method based on energy and information co-regulation as described in claim 1, characterized in that, The channel capacity analysis in step S2 includes the following steps: When using frequency division multiplexing, information transmission is also subject to inter-carrier interference; the frequency interval between the center frequencies of adjacent subcarriers is set to... Its expression is: ； in, The normalized frequency spacing factor, The duration of the symbol in the data frame; The interference power is calculated by integrating the power spectral density of the interference signal falling within the target sub-channel frequency band. for: in: For the first Signal power spectral density of adjacent interfering nodes; The passband frequency range of the target receiving channel bandpass filter corresponds to the main lobe interval of the target signal power spectrum; The calculated interference power Substituting into the channel capacity model, we obtain the single-channel capacity considering multi-user interference. : in, This represents the number of other interfering users simultaneously transmitting in the system.

6. The microgrid channel capacity analysis and power coordinated control method based on energy and information co-modulation as described in claim 1, characterized in that, The channel capacity analysis results in step S2 are used to generate communication parameter configuration results. The communication parameter configuration results include: determining the subcarrier center frequency and the frequency interval between adjacent subcarriers based on the target subchannel capacity; determining the center frequency and passband range of the receiver bandpass filter based on the target signal main lobe bandwidth; and determining the number of converters that can be accessed simultaneously based on the capacity threshold and inter-carrier interference level, so as to ensure that the transmitter modulation, receiver demodulation, and remote current information recovery meet the preset communication quality requirements.

7. The microgrid channel capacity analysis and power coordinated control method based on energy and information co-modulation as described in claim 1, characterized in that, In step S3, converting the local output current information into an information signal for power cooperative control includes: quantizing and encoding the local output current information, and performing frame processing according to communication reliability requirements to form an information data frame for modulation; the information data frame includes a data field for characterizing the local output current information, and may further include one or more of a synchronization field, a node identifier field, a check field, an error correction field, or a frame boundary identifier field.

8. The microgrid channel capacity analysis and power coordinated control method based on energy and information co-regulation as described in claim 1, characterized in that, Information signals from different power converters are distinguished by a preset signal differentiation method, which includes one or more of frequency division multiplexing, time division multiplexing, code division multiplexing, or different disturbance feature configurations. When frequency division multiplexing is used, different subcarrier center frequencies are allocated to different power converters, and the remote current information sent by the target converter is recovered through corresponding filtering and demodulation processing.

9. The microgrid channel capacity analysis and power coordinated control method based on energy and information co-modulation as described in claim 1, characterized in that, The real-time power coordination control and precise current sharing in step S4 specifically include: The improved droop control law formula used in flow sharing control is as follows: in, This represents the actual output voltage values ​​of the first and second parallel converters; This indicates the reference value of the rated no-load voltage of the DC bus; This represents the traditional droop control coefficient, used to initially maintain voltage stability. This represents the output current value collected in real time by the local sensors of each converter; This represents the current sharing compensation gain coefficient, which determines the strength of the system's correction to current deviation. The amount of coherent information indicates the current value of adjacent units recovered by demodulating the controlled ripple of the DC bus; The remote current information It does not originate from an additional physical communication interface or a dedicated communication module, but is obtained directly by demodulating the controlled ripple signal generated by the power switching action of adjacent converters in the bus voltage; that is, it uses the inherent power conversion hardware of the converter as the signal transmission and reception carrier, and separates the information flow from the power flow through the demodulation algorithm. This control method adjusts the compensation gain. This ensures that the current distribution ratio among the parallel units satisfies: in, and The equivalent line impedance of the parallel unit connected to the bus; when the gain As the ratio increases, it approaches 1, thus eliminating the current imbalance caused by line impedance mismatch without relying on external communication hardware such as CAN, RS485, or Ethernet.

Images