Power converter and photovoltaic power generation system

Abstract

The present application provides a power converter and a photovoltaic power generation system, applied to the technical field of power line communication (PLC), and aiming to improve the signal quality of PLC signals in the photovoltaic power generation system, thereby increasing the transmission distance of the PLC signals. The power converter comprises an inverter circuit and a noise cancellation circuit. A direct-current power supply is connected to a power transmission line by means of the inverter circuit. An input end of the noise cancellation circuit is connected to a target coupling point of the power transmission line, and at least one group of reference signal input ends of the noise cancellation circuit is connected to at least one corresponding group of sampling points. Each group of sampling points among the at least one group of sampling points is arranged on a coupling path between the target coupling point and a three-phase alternating-current output end. The noise cancellation circuit is configured to: receive a first communication signal from the target coupling point; and perform noise cancellation processing on the first communication signal on the basis of at least one reference signal acquired from the at least one group of sampling points, so as to obtain a noise-reduced second communication signal.

Description

A power converter and photovoltaic power generation system

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on February 19, 2024, with application number 202410188806.1 and application name “A power converter and photovoltaic power generation system”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of power line carrier communication technology, and in particular to a power converter and a photovoltaic power generation system. Background Art

[0003] Power line communication (PLC) technology uses power transmission lines as communication channels. In photovoltaic power generation systems, photovoltaic power generation and power supply are achieved based on multiple components (such as photovoltaic panels, photovoltaic optimizers, power converters, transformers, and data collectors). Communication signals (including collected device status information and issued device status control instructions) can be exchanged between multiple components of the photovoltaic power generation system (such as between the photovoltaic optimizer and the power converter, and between the power converter and the data collector) based on PLC. As the power of photovoltaic power plants increases, the scale of photovoltaic power plants is also increasing. This places higher demands on the communication distance of PLC signals. In photovoltaic power generation systems, the inverter circuit within the power converter generates significant noise, which seriously affects the reception of PLC signals within the power converter, thereby reducing the transmission distance of the PLC signals. Therefore, to increase the transmission distance of PLC signals, it is necessary to reduce the noise of the PLC signals within the inverter. However, existing noise reduction methods are poorly effective, making it difficult to transmit PLC signals over longer distances. Therefore, a solution is needed to address this problem.

[0004] Summary of the Invention

[0005] The embodiments of the present application provide a power converter and a photovoltaic power generation system to improve the signal quality of a PLC signal in the photovoltaic power generation system, thereby increasing the transmission distance of the PLC signal.

[0006] In order to solve the above problems, this application provides the following technical solutions:

[0007] In a first aspect, a power converter is provided, comprising an inverter circuit and a noise cancellation circuit. The DC input of the inverter circuit is configured to be connected to a DC power source. The three-phase AC output of the inverter circuit is configured to be connected to a power transmission line. The input of the noise cancellation circuit is connected to a target coupling point of the power transmission line, and at least one set of reference signal inputs of the noise cancellation circuit is connected to at least one corresponding set of sampling points. Each set of sampling points in the at least one set of sampling points is arranged on a coupling path between the target coupling point and the three-phase AC output. The noise cancellation circuit can receive a first communication signal from the target coupling point. The first communication signal is then subjected to noise cancellation processing based on at least one reference signal obtained from the at least one set of sampling points to obtain a second communication signal after noise reduction.

[0008] In a photovoltaic power generation system, the coupling path between the inverter circuit inside the power converter and the target coupling point of the power communication device on the power transmission line is prone to generate a lot of noise. When the power communication device communicates with the data collector or photovoltaic optimizer through the PLC signal, the noise will cause serious interference to the reception of the PLC signal, thereby affecting the transmission distance of the PLC signal. In an embodiment of the present application, at least one set of sampling points is set in the coupling path between the target coupling point of the power communication device on the power transmission line and the three-phase AC output end of the inverter circuit. At least one set of reference signal input terminals of the noise elimination circuit are connected to the corresponding at least one set of sampling points. The noise elimination circuit can receive a first communication signal from the target coupling point and obtain at least one reference signal from the above-mentioned at least one set of sampling points through at least one set of reference signal input terminals. Then, the first communication signal is subjected to noise cancellation processing based on the above-mentioned at least one reference signal to obtain a second communication signal after noise reduction. Through this approach, multiple reference signals can be obtained from the coupling path to perform noise cancellation on the first communication signal received at the target coupling point. This filtering removes the noise signal generated by the noise source along the coupling path, resulting in a second communication signal. This improves the signal-to-noise ratio of the useful signal within the second communication signal. This approach can be used to improve the signal-to-noise ratio of the useful signal within the communication signal, even when the PLC signal has a long transmission distance, thereby increasing the transmission distance of the PLC signal.

[0009] In one possible implementation, the number of the at least one set of sampling points is determined based on the number of noise sources on the coupling path. Determining the number of sampling points based on the number of noise sources on the coupling path allows for more comprehensive noise cancellation processing of the first communication signal at the target coupling point using the reference signal, thereby increasing the signal-to-noise ratio of the useful signal in the second communication signal.

[0010] In one possible implementation, the noise source includes at least one of a differential-mode inductor, a common-mode inductor, or a switching device disposed in the coupling path. Such differential-mode inductors, common-mode inductors, or switching devices disposed in the coupling path between the inverter circuit within the power converter and the target coupling point of the power communication device on the power transmission line may generate noise signals. Therefore, the noise source in the coupling path can be determined based on these devices.

[0011] In one possible implementation, at least one set of sampling points is set at a noise source. Setting the sampling points at the noise source can make the noise signal contained in the reference signal closer to the actual noise signal. When the reference signal is used to perform noise cancellation processing on the first communication signal at the target coupling point, the noise signal in the first communication signal can be better removed, thereby improving the signal-to-noise ratio of the useful signal in the second communication signal.

[0012] In one possible implementation, the noise cancellation circuit includes an arithmetic circuit and a sampling circuit. The input of the arithmetic circuit is connected to a target coupling point and at least one set of sampling points via the sampling circuit. The sampling circuit can perform digital-to-analog conversion on the signals from the target coupling point and at least one set of sampling points before processing them via the arithmetic circuit. This can reduce interference and errors, thereby improving computation accuracy.

[0013] In one possible implementation, a sampling circuit includes a first sub-sampling circuit, a second sub-sampling circuit, and a third sub-sampling circuit; the input of the first sub-sampling circuit serves as a first reference signal input and is connected to a group of sampling points located near a three-phase AC output terminal in at least one group of sampling points; the input of the second sub-sampling circuit serves as a second reference signal input and is connected to a group of sampling points located near a target coupling point in at least one group of sampling points; the outputs of the first sub-sampling circuit and the second sub-sampling circuit are both connected to an arithmetic circuit; and the target coupling point is connected to the arithmetic circuit via the third sub-sampling circuit. In this manner, noise cancellation processing can be performed on the first communication signal using reference signals from a group of sampling points located near the three-phase AC output terminal and reference signals from a group of sampling points located near the target coupling point on the coupling path.

[0014] In one possible implementation, the first subsampling circuit, the second subsampling circuit, and the third subsampling circuit each include a cascaded low-pass filter and a digital-to-analog converter. The low-pass filters can be used to perform low-pass filtering on the signals sampled by the three sampling circuits, thereby improving signal quality and making subsequent processing results more accurate.

[0015] In one possible implementation, the low-pass filter is a low-pass filter provided with an isolation circuit. The low-pass filter provided with an isolation circuit can prevent signals on the coupling path from interfering with signals in the operational circuit, thereby improving the reliability of the noise cancellation circuit in performing noise cancellation on the first communication signal.

[0016] In one possible implementation, the noise cancellation circuit further includes a pulse suppression circuit. The input of the pulse suppression circuit is connected to the output of the computation circuit. The pulse suppression circuit can be used to eliminate pulse signals in the second communication signal whose intensity exceeds a threshold, thereby obtaining a third communication signal. This method can eliminate pulse signals in the second communication signal whose intensity exceeds the threshold, thereby removing interference from high-intensity pulse signals and improving the accuracy and reliability of subsequent processing results.

[0017] In a possible implementation, the power converter further includes a coupler, wherein the input end of the noise elimination circuit is connected to the target coupling point via the coupler; or the coupler is connected to the output end of the noise elimination circuit.

[0018] In one possible implementation, the power converter further includes a power communication device, and the noise cancellation circuit is disposed within the power communication device. The input of the noise cancellation circuit serves as the input of the power communication device and is connected to a target coupling point of the power transmission line. In this manner, the noise cancellation circuit can be implemented as an on-chip circuit, thereby increasing the integration of the power converter and reducing wiring area.

[0019] In one possible implementation, the power converter further includes a power communication device, and the output of the noise cancellation circuit is connected to the input of the power communication device. The power communication device can be used to process the second communication signal. In this manner, the noise cancellation circuit can be provided as an independent circuit at the target coupling point and the input of the power communication device, facilitating tailored design of the noise cancellation circuit based on actual needs.

[0020] In a second aspect, a photovoltaic power generation system is provided, comprising one or more power converters and a data collector as described in any possible implementation of the first aspect, wherein the one or more power converters are configured to communicate with the data collector via a power transmission line.

[0021] In a third aspect, a photovoltaic power generation system is provided, comprising a power converter according to any possible implementation of the first aspect and one or more photovoltaic optimizers. The power converter is configured to communicate with the one or more photovoltaic optimizers via a power transmission line, and each of the one or more photovoltaic optimizers is configured to be connected to a photovoltaic panel.

[0022] Regarding the technical principles and beneficial effects of the second and third aspects mentioned above, please refer to the relevant description of the first aspect mentioned above, and no further details will be given here. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a schematic structural diagram of a photovoltaic power generation system;

[0024] FIG2 is a schematic diagram of an adaptive noise cancellation algorithm;

[0025] FIG3 is a structural diagram of a power converter according to an embodiment of the present application;

[0026] FIG4 is a second structural diagram of a power converter provided in an embodiment of the present application;

[0027] FIG5 is a schematic diagram of a noise elimination circuit provided in an embodiment of the present application;

[0028] FIG6 is a schematic diagram of another noise elimination circuit provided in an embodiment of the present application;

[0029] FIG7 is a third structural diagram of a power converter provided in an embodiment of the present application;

[0030] FIG8 is a fourth structural diagram of a power converter provided in an embodiment of the present application;

[0031] FIG9 is a schematic diagram of another noise elimination circuit provided in an embodiment of the present application;

[0032] FIG10 is a fifth structural diagram of a power converter provided in an embodiment of the present application;

[0033] FIG11 is a sixth structural diagram of a power converter provided in an embodiment of the present application;

[0034] FIG12 is a diagram showing the denoising results after denoising different numbers of reference signals provided in an embodiment of the present application. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

[0036] In the present application, "at least one" refers to one or more, and "plurality" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: the existence of A alone, the existence of A and B at the same time, and the existence of B alone, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b or c can represent: a, b, c, a and b, a and c, b and c or a, b and c, where a, b and c can be single or multiple. In addition, in the embodiments of the present application, words such as "first" and "second" do not limit the quantity and order.

[0037] It should be noted that, in this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described in this application as "exemplary" or "for example" should not be interpreted as being more preferred or more advantageous than other embodiments or designs. To be precise, the use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete way. The terms "connection", "coupling" and the like involved in the embodiments of this application should be understood in a broad sense. For example, they may refer to a physical direct connection, or they may refer to an indirect connection achieved through an electronic device, such as a connection achieved through a resistor, inductor, capacitor or other electronic device.

[0038] The present application is described in detail below with reference to the accompanying drawings and embodiments:

[0039] Power line carrier (PLC) communication technology uses power transmission lines as communication channels. It modulates analog or digital signals over the lines via carrier waves for transmission, enabling interactive communication between multiple nodes over these lines. Typical PLC communication is point-to-multipoint (P2MP) wired communication. Specifically, the PLC communication system consists of a central controller (CCO) and multiple communication stations (STAs). These stations can communicate with the CCO independently. Multiple stations can also communicate with each other based on the CCO. As an efficient and stable communication method, PLC not only enables long-distance signal transmission, but also offers high transmission efficiency, excellent reliability, and confidentiality, making it suitable for many practical applications. PLC full-duplex communication can significantly improve the efficiency of PLC spectrum utilization, but its implementation requires highly isolated RF devices and circuits.

[0040] A photovoltaic power generation system (PGS) is a power generation system that converts solar radiation energy directly into electrical energy by utilizing the photovoltaic effect of semiconductor materials. As shown in Figure 1, the photovoltaic power generation system 100 includes a photovoltaic array 110, a power converter 120, a transformer 140, and a data collector 150. In addition, the photovoltaic power generation system also includes a power grid 160 or a load 170. The photovoltaic array 110 includes a plurality of photovoltaic panels 111 and a plurality of photovoltaic optimizers 112. Each photovoltaic panel 111 in the plurality of photovoltaic panels 111 is connected to a corresponding photovoltaic optimizer 112 in the plurality of photovoltaic optimizers 112. The plurality of photovoltaic optimizers 112 are respectively connected to the power converter 120 through a power transmission line L. The plurality of power converters 120 are respectively connected to the data collector 150 and the AC combiner box 130 through the power transmission line L, and the AC combiner box 130 is connected to the transformer 140. The transformer 140 is connected to the power grid 160 or the load 170 through the power transmission line L. Wherein:

[0041] Photovoltaic panels 111 are used to convert solar radiation into direct current (DC). Photovoltaic optimizer 112 is used to detect operating status information such as the operating power of the corresponding PV panel 111, convert the input low-current DC power into high-current DC power, and transmit the resulting high-current DC power to power converter 120. Power converter 120 is used to boost the input DC power and invert the boosted DC power into alternating current (AC) power, which is then supplied to AC combiner box 130. Power converter 120 is also used to sample and obtain power, current, and voltage information of the input DC power and / or output AC power. Each AC combiner box 300 combines the input AC power and supplies it to transformer 140. Transformer 140 transforms the input AC power and supplies the transformed current to grid 160 or load 170. Data collector 150 is used to record operating status information of power converter 120. In one example, the power converter 120 may be an inverter.

[0042] For example, in the embodiment of the embodiment of FIG1 , each photovoltaic optimizer 112 is configured as a power converter for an STA, and the power converter 120 is configured as a power converter for a CCO. The photovoltaic optimizer 112 and the power converter 120 can communicate business information based on PLC technology. For example, the photovoltaic optimizer 112 can transmit operating information such as the voltage, current, temperature, and operating power of the photovoltaic panel 111 to the power converter 120 through PLC technology. The power converter 120 can also issue control instruction information to different photovoltaic optimizers 112 based on PLC technology, such as maximum power point tracking (MPPT) control instructions and conduction control instructions.

[0043] For example, a power converter serving as an STA can be provided in the power converter 120, and related devices can be provided in the box of the transformer 140 or in the data collector 150 to serve as a power converter serving as a CCO. Multiple power converters 120 and the data collector 150 can communicate business information via PLC technology. For example, the power converter 120 transmits sampled power information, current information, and voltage information to the data collector 150 based on PLC technology, and the data collector 150 can also send control instruction information to the corresponding power converter 120 based on PLC technology. However, in a photovoltaic power generation system, the coupling path between the inverter circuit inside the power converter 120 and the target coupling point of the power communication device on the power transmission line is prone to generating significant noise. When the power communication device communicates with the data collector or photovoltaic optimizer via PLC signals, this noise can cause severe interference to the reception of the PLC signals, thereby affecting the transmission distance of the PLC signals.

[0044] To address the above issues, as shown in Figure 2, an adaptive filter AF in noise cancellation module 200 can be used to estimate the noise generated by the noise source. The estimated noise signal y(k) is then subtracted from the desired signal d(k) containing the noise n1, thereby achieving the purpose of noise cancellation. The noise cancellation module 200 generally requires an original signal and a reference signal as input. The original signal consists of the desired signal s(k) and the noise signal n1 generated by the noise source, while the reference signal is the correlated noise signal n2 generated by the noise source. The adaptive filter AF is used to continuously approximate the estimated signal y(k) to the noise signal n1 that is doped within the desired signal. This estimated noise signal y(k) is then subtracted from the original signal via a canceller A1, thereby achieving the purpose of noise cancellation. In the above implementation, the filter coefficients of the adaptive filter AF are determined using a coefficient update algorithm. This algorithm calculates adjustments to each filter coefficient based on an error signal e(k). The error signal e(k) is typically calculated as the difference between the actual output signal y(k) of the adaptive filter AF and the desired signal d(k). The adaptive filtering algorithm will change the coefficients to minimize the mean square value of the error signal e(k). The following equation describes the implementation process of the commonly used LMS algorithm:

[0045] 1. Filtering: y(k) = X(k) * W(k);

[0046] 2. Error estimation: e(k) = d(k) – y(k);

[0047] 3. Update filter coefficients: g(k) = 2e(k)x(k); W(k+1) = W(k) + u*g(k).

[0048] Where k is the number of iterations of the algorithm, y(k) is the output of the adaptive filter (AF), X(k) is a vector of input signals, W(k) is the filter coefficient vector of the adaptive filter (AF), e(k) is the error signal, d(k) is the desired signal, u is the convergence factor (or step size), and W(k+1) is the filter tap weight for the next iteration. In this algorithm, g(k) is an important value; it is the estimated gradient or the projection of the square of the current error signal. When the algorithm converges, g(k) is expected to be a very small number with a mean of zero.

[0049] Although the purpose of eliminating noise can be achieved through the adaptive filtering algorithm in the above method, the adaptive filter AF in the photovoltaic power generation system is usually implemented by a software algorithm, and the filter coefficient is iteratively updated completely through the adaptive filtering algorithm. As the order of the adaptive filter (step parameter) increases, the stability of the system decreases, resulting in limited effect on improving the signal-to-noise ratio of useful signals in the PLC signal in actual use, and cannot meet the needs of the increasingly larger scale of photovoltaic power stations.

[0050] To better solve the above problems, as shown in FIG3 , an embodiment of the present application provides a power converter 300, which includes an inverter circuit 310 and a noise cancellation circuit 320. The DC input terminal of the inverter circuit 310 is used to connect to a DC power supply 400. The three-phase AC output terminal of the inverter circuit 310 is used to connect to a power transmission line. The input terminal of the noise cancellation circuit 320 is connected to the target coupling point Y0 of the power transmission line, and at least one set of reference signal input terminals (x1, ..., xn) of the noise cancellation circuit 320 is connected to at least one corresponding set of sampling points (a1 to an). Each set of sampling points in the at least one set of sampling points is set on a coupling path 330 between the target coupling point Y0 and the three-phase AC output terminal of the inverter circuit 310. The DC power supply can be the photovoltaic panel and photovoltaic optimizer in FIG1 , or the DC power supply can be an energy storage battery. The output terminal of the noise cancellation circuit 320 can also be connected to a power communication device 340. The noise cancellation circuit 320 may receive a first communication signal y1 from the target coupling point Y0 and then perform noise cancellation processing on the first communication signal y1 based on at least one reference signal obtained from at least one set of sampling points to obtain a noise-reduced second communication signal y2.

[0051] Through the above-described embodiment, the noise cancellation circuit 320 can directly obtain a reference signal from the coupling path 330. Based on the obtained reference signal, the first communication signal received at the target coupling point Y0 is then subjected to noise cancellation processing. This filtering eliminates the noise signal generated by the noise source on the coupling path 330, thereby obtaining a second communication signal. This improves the signal-to-noise ratio of the useful signal in the second communication signal. Therefore, even if the PLC signal has a long transmission distance, the signal-to-noise ratio of the useful signal in the PLC signal can be improved by referring to the above-described method, thereby increasing the transmission distance of the PLC signal. Furthermore, the noise cancellation circuit 320 is independently disposed between the target coupling point Y0 and the power communication device 340, allowing for a more targeted design of the noise cancellation circuit 320 based on actual needs, thereby improving the performance of the noise cancellation circuit 320.

[0052] In one embodiment, as shown in FIG4 , when power converter 300 further includes a power communication device 340, noise cancellation circuit 320 can be disposed within power communication device 340, with the input of noise cancellation circuit 320 connected to the target coupling point Y0 of the power transmission line as the input of power communication device 340. In this manner, noise cancellation circuit 320 can be integrated as an on-chip circuit within power communication device 340, thereby reducing wiring area and improving processing efficiency.

[0053] In one possible implementation, as shown in FIG5 , the noise cancellation circuit 320 includes a sampling circuit 321 and an operation circuit 322. The sampling circuit 321 includes a first sub-sampling circuit 3211, a second sub-sampling circuit 3212, and a third sub-sampling circuit 3213. The input of the first sub-sampling circuit 3211, serving as a first reference signal input x1, is connected to a group of sampling points (denoted as sampling points a1) located near the three-phase AC output of the inverter circuit 310. The input of the second sub-sampling circuit 3212, serving as a second reference signal input x2, is connected to a group of sampling points (denoted as sampling points a2) located near the target coupling point Y0. The outputs of the first sub-sampling circuit 3211 and the second sub-sampling circuit 3212 are both connected to the operation circuit 322. The target coupling point Y0 is connected to the operation circuit 322 via the third sub-sampling circuit 3213. In the above manner, the first communication signal at the target coupling point Y0 can be subjected to noise cancellation processing by the above-mentioned operation circuit 322 based on the reference signals at both ends of the above-mentioned coupling path 330. In one example, the above-mentioned operation circuit 322 may include a filter coefficient solver 3221, a filter 3222, and a canceller 3223. Among them, the filter coefficient solver 3221 can calculate the filter coefficient of the filter 3222 based on the above-mentioned two reference signals and the first communication signal. Then, the filter 3222 can filter the above-mentioned two reference signals according to the filter coefficient to obtain a corresponding noise signal. Finally, the above-mentioned canceller 3223 can perform noise cancellation processing on the first communication signal based on the above-mentioned noise signal to eliminate the above-mentioned noise signal contained in the first communication signal and obtain a second communication signal after noise reduction. Among them, the above-mentioned first sub-sampling circuit 3211, the second sub-sampling circuit 3212, and the third sub-sampling circuit 3213 can all include a cascaded low-pass filter (LPF) and an analog-to-digital converter ADC. The signal of each sampling point can be first filtered by the low-pass filter LPF and then converted into a digital signal by the ADC. Then, the operation circuit 322 performs noise cancellation processing on the digital signal corresponding to the first communication signal based on the digital signal corresponding to the above-mentioned two reference signals. In this way, the reference signal can be filtered and converted into a digital signal to perform subsequent processing. The digital signal has a stronger anti-interference ability, which can make the subsequent processing results more accurate.

[0054] Furthermore, the above-mentioned low-pass filter LPF can be a low-pass filter with an isolation circuit, so as to safely isolate the noise elimination circuit 320 and the power transmission line, thereby preventing the signal transmitted on the power transmission line from interfering with the signal of the noise elimination circuit 320.

[0055] In one embodiment, as shown in FIG6 , the noise cancellation circuit 320 includes a sampling circuit 321 and an operation circuit 322. The sampling circuit 321 includes a first sub-sampling circuit 3211, a second sub-sampling circuit 3212, a third sub-sampling circuit 3213, and a fourth sub-sampling circuit 3214. The input of the first sub-sampling circuit 3211 serves as a first reference signal input x1 and is connected to a group of sampling points (denoted as sampling points a) located near the three-phase AC output terminal in at least one group of sampling points. The input of the second sub-sampling circuit 3212 serves as a second reference signal input x2 and is connected to a group of sampling points (denoted as sampling points b) located near the target coupling point Y0 in at least one group of sampling points. The outputs of the first sub-sampling circuit 3211 and the second sub-sampling circuit 3212 are both connected to the operation circuit. The target coupling point Y0 is connected to the operation circuit 322 via the third sub-sampling circuit 3213. The input end of the fourth sub-sampling circuit 3214 can be connected as the third reference signal input end x3 to a group of sampling points (denoted as sampling points c) between sampling point a and sampling point b. In one example, the operation circuit 322 may include a filter coefficient solver 3221, a filter 3222, and a canceller 3223. Among them, the filter coefficient solver 3221 can calculate the filter coefficient of the filter based on the above three reference signals and the first communication signal. Then, the filter 3222 filters the above three reference signals according to the filter coefficient to obtain a corresponding noise signal. Finally, the canceller 3223 can perform noise cancellation processing on the first communication signal based on the above noise signal to eliminate the above noise signal contained in the first communication signal and obtain a second communication signal after noise reduction. Among them, the above first sub-sampling circuit 3211, the second sub-sampling circuit 3212, the third sub-sampling circuit 3213 and the fourth sub-sampling circuit 3214 may also include a low-pass filter and an ADC, which will not be described in detail in the embodiment of the present application.

[0056] In the above implementation process, the filter coefficient solver 3221, filter 3222 and canceller 3223 can be software functional modules or circuits set on the chip, and the embodiment of the present application does not impose specific restrictions on this.

[0057] Exemplarily, the filter coefficient solver 3221 may directly calculate the corresponding Wiener solution based on the at least one reference signal using an adaptive filtering algorithm to determine the filter coefficients of the filter 3222 for each reference signal. For a single reference signal, the Wiener solution is calculated as follows. The vector X(n) of a single reference signal may be expressed as:

[0058] X(n)=[x(n)x(n-1)...x(nL)] T ;

[0059] Wherein, x(n) to x(nL) represent the sample values ​​of a single reference signal at L+1 moments.

[0060] The output signal y(n) is:

[0061] The L+1 weight coefficients w0(n)~w of the adaptive linear combiner L (n) constitutes a weight coefficient vector, called the weight vector, which is represented by W(n), that is,

[0062] W(n)=[w0(n)w1(n)…w L (n)] T ;

[0063] Therefore, y(n) can be expressed as:

[0064] y(n)=X T (n)W(n)=W T (n)X(n);

[0065] The error signal e(n) is:

[0066] e(n)=d(n)-y(n)=d(n)-X T (n)W(n)=d(n)-W T (n)X(n);

[0067] Among them, X T (n) represents the transpose of X(n), W T (n) represents the transpose of W(n), and d(n) represents the desired signal.

[0068] The adaptive linear combiner follows the criterion of minimizing the mean square value ξ(n) of the error signal, namely:

[0069] ξ(n)=E[e 2 (n)]=E[d 2 (n)]+W T (n)E[X(n)X T (n)]W(n)-2E[d(n)X T (n)]W(n);

[0070] The autocorrelation matrix of the input signal x(n) is:

[0071] Where E[.] represents the mean vector.

[0072] The cross-correlation matrix between the desired signal d(n) and the reference signal is:

[0073] P=E[d(n)X(n)]=E[d(n)x(n)]d(n)x(n-1)…d(n)x(nL)];

[0074] Then the simple expression of mean square error ξ(n) is:

[0075] ξ(n)=E[d 2 (n)]+W T RW-2P T W;

[0076] Among them, P T represents the transpose of P, W T For the above W T (n), where W is W(n) as described above. This formula shows that, assuming both the input and reference signals are stationary random signals, the mean square error (MSE) is a quadratic function of the components of the weight vector. The graph of this function is a concave hyperparaboloid in L+2-dimensional space with a single minimum point. This surface is called the mean square error performance surface, or simply the performance surface.

[0077] Gradient of the mean squared error performance surface:

[0078] Let the gradient Equal to zero, the optimal weight vector or Wiener solution W corresponding to the minimum mean square error can be obtained * , and solve for W * =R -1 P.

[0079] Furthermore, when the input is multiple reference signals, the vector X(n) of the multiple reference signals can be expressed as: X(n) = [x0(n)x1(n)...x L (n)] T . Among them, x0(n)~x L (n) represents the sampled values ​​of L+1 reference signals at the same time. At this time, the optimal weight vector or Wiener solution W corresponding to the minimum mean square error is * The calculation method of can also refer to the above process, and the embodiment of this application will not be described in detail in this step.

[0080] In one embodiment, when the input of the filter coefficient solver 3221 is a plurality of reference signals, the Wiener solution (i.e., filter coefficient) of each reference signal can be solved separately according to the above method, and then each reference signal is filtered according to the Wiener solution of each reference signal to obtain a noise signal. Finally, the first communication signal is subjected to noise cancellation processing according to each noise signal through a canceller. Of course, when the input of the filter coefficient solver 3221 is a plurality of reference signals, an adaptive filtering algorithm can also be used to calculate the Wiener solution of the plurality of reference signals, and then the plurality of input signals are filtered according to the Wiener solution to obtain a noise signal. Finally, the first communication signal is subjected to noise cancellation processing according to the noise signal.

[0081] In one embodiment, the filter coefficients of filter 3222 can first be trained using a portion of training data to obtain initial filter coefficients. Then, noise cancellation processing is performed on subsequent communication signals based on the filter coefficients. The controller can also monitor the signal quality of the noise-reduced signal output from the output end of the noise filtering circuit 320. For example, the signal-to-noise ratio of the noise-reduced signal can be monitored. Then, when the signal quality falls below a quality threshold, the updated filter coefficients are retrained based on a portion of the data. In this way, intermittent training can be used based on the slowly changing noise characteristics of the inverter circuit to reduce processing complexity and improve real-time performance.

[0082] In a photovoltaic power generation system, noise sources on the coupling path 330 between the target coupling point Y0 and the three-phase AC output of the inverter circuit 310 generally include differential-mode inductors, common-mode inductors, and switching devices. The number of noise sources can be determined based on the number of these devices actually used in the coupling path 330. Furthermore, the number of the at least one set of sampling points can also be determined based on the number of noise sources on the coupling path 330. In one embodiment, as shown in FIG7 , if a cascaded differential-mode inductor 360 and a switching device 350 are provided on the coupling path 330 between the target coupling point Y0 and the three-phase AC output, two sets of sampling points can be provided on the coupling path 330, including sampling point a1 and sampling point a2. Sampling point a1 can be provided at the output of the switching device 350, and sampling point a2 can be provided at the output of the differential-mode inductor 360. The first reference signal input of the noise cancellation circuit 320 can be connected to sampling point a1, and the second reference signal input of the noise cancellation circuit 320 can be connected to sampling point a2. The noise cancellation circuit 320 may perform noise cancellation processing on the first communication signal received at the target coupling point Y0 according to the two reference signals obtained from the two groups of sampling points, so as to obtain a second communication signal after noise reduction.

[0083] In the above implementation process, sampling points a1 and a2 can be set according to the setting method of the target coupling point Y0. For example, when the coupling path 330 between the target coupling point Y0 and the three-phase AC output terminal of the inverter circuit 310 uses a three-phase power transmission line, the target coupling point Y0 can be connected to any two phases of the three-phase power transmission line. In this case, sampling points a1 and a2 can also be set on any two phases of the three-phase power transmission line. For example, as shown in Figure 7, when the target coupling point Y0 is set on phases A and B of the three-phase power transmission line, sampling points a1 and a2 can also be set on phases A and B of the three-phase power transmission line. Of course, when the target coupling point is set on a phase of the three-phase power transmission line, sampling points a1 and a2 are also set on the corresponding power transmission line, but this embodiment of the present application does not impose specific limitations on this.

[0084] It is understandable that the above embodiment is only an exemplary implementation scheme given in the embodiment of the present application. In specific implementation, the setting method of the sampling points can be adaptively adjusted according to the coupling method of the target coupling point Y0, and the embodiment of the present application does not impose specific restrictions on this.

[0085] In one embodiment, as also shown in FIG. 7 , sampling point a3 may be further provided on phases B and C of the three-phase power transmission line at the output end of each noise source. This sampling point a3 may be connected to the operation circuit 322 in the noise cancellation circuit 320 via a sampling circuit. Through sampling point a3, the signal between the power transmission line serving as the PLC signal transmission line and other power transmission lines in the coupling path 330 can be transmitted as a reference signal to the noise cancellation circuit 320 for processing, thereby eliminating interference noise between the power transmission lines that may interfere with the communication signal.

[0086] It is understandable that the above-mentioned setting method of the sampling points is only an example given in the embodiment of the present application. During specific implementation, the operator can make targeted settings based on the noise sources that may be contained in the actual circuit structure between the three-phase AC output terminal of the inverter circuit 310 and the target coupling point Y0. The embodiment of the present application will not be described in detail here.

[0087] In one embodiment, as shown in FIG8 , if a cascaded differential-mode inductor 360, a common-mode inductor 370, and a switch device 350 are provided on the coupling path 330 between the target coupling point Y0 and the three-phase AC output of the inverter circuit 310, three groups of sampling points can be set on the coupling path 330, including sampling point a1, sampling point a2, and sampling point a3. Sampling point a1 can be set at the output of the switch device 350, sampling point a2 can be set at the output of the differential-mode inductor 360, and sampling point a3 can be set at the output of the common-mode inductor 370. The first reference signal input of the noise cancellation circuit 320 can be connected to sampling point a1, the second reference signal input of the noise cancellation circuit 320 can be connected to sampling point a2, and the third reference signal input of the noise cancellation circuit 320 can be connected to sampling point a3. Sampling points a1, a2, and a3 can be set on the coupling path 330 in the same manner as the target coupling point Y0, and this embodiment of the present application will not be further described here.

[0088] It is understandable that when there are other devices that may generate noise between the above-mentioned target coupling point Y0 and the three-phase AC output end of the inverter circuit 310, a sampling point and a corresponding sampling circuit can also be set at the corresponding noise source, so that the operation circuit can be fully utilized to perform noise cancellation processing on the first communication signal received at the target coupling point Y0 based on the reference signal at the noise source, thereby further improving the signal-to-noise ratio of the useful signal in the PLC signal.

[0089] In one embodiment, based on FIG. 3 , as shown in FIG. 9 , the noise elimination circuit 320 may further include a pulse suppression circuit 3224. This pulse suppression circuit 3224 may eliminate pulse signals in the second communication signal whose pulse strength exceeds a strength threshold, thereby obtaining a third communication signal having a pulse strength that more closely meets the requirements. The strength threshold of the pulse suppression circuit 3224 may be set based on actual needs and is not specifically limited in this embodiment of the present application.

[0090] It is understandable that although the pulse suppression circuit 3224 in the above embodiment is based on FIG. 3 , in actual implementation, the power converter 300 may be the power converter 300 in any possible implementation scheme in FIG. 3 to FIG. 9 .

[0091] In one embodiment, based on FIG3 , as shown in FIG10 , the power converter 300 may further include a coupler 380 . The input end of the noise cancellation circuit 320 is connected to the target coupling point Y0 via the coupler 380 . The coupler can be used to isolate the power transmission line from the noise cancellation circuit 320 , thereby preventing the signal of the power transmission line from interfering with the signal of the noise cancellation circuit 320 . In one example, the coupler may be a transformer, which can be used to transform the transmitted signal while isolating the power transmission line from the noise cancellation circuit 320 , thereby preventing the signal voltage from being too high from affecting the noise cancellation circuit 320 and the power communication device 340 .

[0092] It is understandable that although the coupler in the above embodiment is based on FIG. 3 , in actual implementation, the power converter 300 may be the power converter 300 in any possible implementation scheme in FIG. 3 to FIG. 9 .

[0093] In one embodiment, based on Figure 3 , as shown in Figure 11 , the power converter 300 may further include a coupler 380 . The output of the noise cancellation circuit 320 is connected to the input of the power communication device 340 via the coupler 380 ; the power communication device 340 is configured to process the power communication signal after noise cancellation. In this manner, the first communication signal at the target coupling point Y0 can be subjected to noise cancellation processing by the noise cancellation circuit 320 before being transformed and isolated by the coupler, preventing mutual interference between the signals from the noise cancellation circuit 320 and the power communication device 340.

[0094] It is understandable that although the coupler in the above embodiment is based on FIG. 3 , in actual implementation, the power converter 300 may be the power converter 300 in any possible implementation scheme in FIG. 3 to FIG. 9 .

[0095] In one embodiment, in order to verify the noise reduction effect of the power converter 300 provided in the embodiment of the present application, the embodiment of the present application also tested the noise reduction amount of the power converter by a single reference signal and two reference signals. The test results are shown in Figure 12. It can be seen from Figure 12 that when a single reference signal is used to perform noise cancellation processing on the communication signal of the above-mentioned target coupling node, the noise reduction amount in the 0.5-3.7MHz frequency band is about 10.4dB. When two reference signals are used to perform noise cancellation processing on the communication signal of the above-mentioned target coupling node, the noise reduction amount in the 0.5-3.7MHz frequency band is about 11dB. It can be seen that the power converter 300 provided by the present application can improve the noise reduction effect of the PLC signal, thereby increasing the transmission distance of the PLC signal.

[0096] The controller and computing circuit involved in the embodiments of the present application can be a single chip. For example, it can be a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a system on chip (SoC), a central processing unit (CPU), a network processor (NP), a digital signal processing circuit (DSP), a microcontroller unit (MCU), a programmable logic device (PLD), or other integrated chips.

[0097] The memory involved in the embodiments of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate synchronous DRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), and direct RAM bus RAM (DR RAM). It should be noted that the memory of the systems and methods described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0098] In the several embodiments provided in this application, it should be understood that the disclosed systems, circuits, and devices can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of the circuits and modules is only a logical function division. In actual implementation, there may be other division methods, such as multiple circuits or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be an indirect coupling or communication connection through some interface, device or circuit, which can be electrical, mechanical or other forms.

[0099] The circuits described as separate components may or may not be physically separate, and the components shown as circuits may or may not be physical circuits, that is, they may be located on a single device or distributed across multiple devices. Some or all of these circuits may be selected to achieve the objectives of this embodiment based on actual needs.

[0100] In addition, the functional circuits in the various embodiments of the present application may be integrated into one device, or each circuit may exist physically separately, or two or more circuits may be integrated into one device.

[0101] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A power converter, characterized in that: include: An inverter circuit and a noise elimination circuit; the DC input terminal of the inverter circuit is used to connect to a DC power supply; the three-phase AC output terminal of the inverter circuit is used to connect to a power transmission line; the input terminal of the noise elimination circuit is connected to a target coupling point of the power transmission line, and at least one group of reference signal input terminals of the noise elimination circuit is connected to at least one corresponding group of sampling points; each group of sampling points in the at least one group of sampling points is arranged on a coupling path between the target coupling point and the three-phase AC output terminal; wherein the noise elimination circuit is used to: receiving a first communication signal from the target coupling point; The first communication signal is subjected to noise cancellation processing according to at least one reference signal obtained from the at least one group of sampling points to obtain a second communication signal after noise reduction.

2. The power converter according to claim 1, wherein: The number of the at least one group of sampling points is determined according to the number of noise sources on the coupling path.

3. The power converter according to claim 2, wherein: The noise source includes at least one of a differential mode inductor, a common mode inductor or a switching device arranged on the coupling path.

4. The power converter according to claim 2 or 3, characterized in that: The at least one group of sampling points is arranged at the noise source.

5. The power converter according to any one of claims 1 to 4, characterized in that: The noise elimination circuit includes an operation circuit and a sampling circuit; the input end of the operation circuit is connected to the target coupling point and the at least one group of sampling points through the sampling circuit.

6. The power converter according to any one of claims 2 to 5, characterized in that: The sampling circuit includes a first sub-sampling circuit, a second sub-sampling circuit, and a third sub-sampling circuit; an input end of the first sub-sampling circuit is connected to a group of sampling points located near the three-phase AC output end among the at least one group of sampling points as a first reference signal input end; an input end of the second sub-sampling circuit is connected to a group of sampling points located near the target coupling point among the at least one group of sampling points as a second reference signal input end; an output end of the first sub-sampling circuit and an output end of the second sub-sampling circuit are both connected to the operation circuit; and the target coupling point is connected to the operation circuit via the third sub-sampling circuit.

7. The power converter according to claim 6, characterized in that The first sub-sampling circuit, the second sub-sampling circuit, and the third sub-sampling circuit each include a cascaded low-pass filter and a digital-to-analog converter.

8. The power converter according to claim 7, wherein: The low-pass filter is a low-pass filter provided with an isolation circuit.

9. The power converter according to any one of claims 5 to 8, characterized in that: The noise elimination circuit also includes: a pulse suppression circuit; the input end of the pulse suppression circuit is connected to the output end of the operation circuit; the pulse suppression circuit is used to: eliminate the pulse signal whose intensity exceeds the intensity threshold in the second communication signal to obtain a third communication signal.

10. The power converter according to any one of claims 1 to 9, characterized in that: Also includes: coupler; The input end of the noise elimination circuit is connected to the target coupling point through the coupler; or the coupler is connected to the output end of the noise elimination circuit.

11. The power converter according to any one of claims 1 to 10, characterized in that: The power converter further includes a power communication device, the noise elimination circuit is provided in the power communication device, and an input end of the noise elimination circuit is connected to the target coupling point of the power transmission line as an input end of the power communication device.

12. The power converter according to any one of claims 1 to 10, characterized in that: The power converter further includes a power communication device; the output end of the noise elimination circuit is connected to the input end of the power communication device.

13. A photovoltaic power generation system, characterized in that: The device comprises one or more power converters and a data collector according to any one of claims 1 to 12, wherein the one or more power converters are configured to communicate with the data collector via the power transmission line.

14. A photovoltaic power generation system, characterized in that: The method comprises a power converter according to any one of claims 1 to 12 and one or more photovoltaic optimizers, wherein the power converter is used to communicate with the one or more photovoltaic optimizers through the power transmission line, and each of the one or more photovoltaic optimizers is used to connect to a photovoltaic power generation panel.

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