Adaptive harmonic voltage precision control method with external impedance perception

Abstract

The present application relates to harmonic voltage treatment, specifically to adaptive harmonic voltage accurate control method with external impedance perception, determine the harmonic voltage that needs to be treated and the initial external impedance cosine value that needs to be treated harmonic, calculate the first and second given virtual harmonic resistance of active harmonic resistance device, and calculate the corresponding harmonic voltage suppression ratio, according to the results of two active disturbance, perceive the actual external impedance of active harmonic resistance device access point that needs to be treated harmonic, calculate the final virtual harmonic resistance according to the control target, when the harmonic voltage occurs, re-perceive the actual external impedance of active harmonic resistance device access point that needs to be treated harmonic, and adaptively solve the new final virtual harmonic resistance according to the control target, the present application can effectively overcome the defects that the prior art can only treat each harmonic voltage by multiple optimization iteration method under the condition of unknown grid parameters and time-varying operation state.

Description

Technical Field

[0001] This invention relates to harmonic voltage management, and more specifically to an adaptive harmonic voltage precision control method with external impedance sensing. Background Technology

[0002] With the continuous increase in the scale of new energy grid connection, the successive commissioning of high-voltage AC / DC flexible transmission projects, and the demand for efficient and intelligent electricity consumption from power users, the degree of power electronics in related equipment in the generation, transmission, and consumption links is constantly deepening. Consequently, harmonic problems are also evolving with new characteristics, exhibiting a high-density, decentralized, and grid-wide trend. As high-voltage background harmonics gradually penetrate to low-voltage levels, and low-voltage dispersed harmonic sources continuously converge to high-voltage levels, coupled with harmonic resonance amplification, the harmonic voltage of the power grid continues to deteriorate. The broad spectrum and independence of harmonic frequencies mean that the above-mentioned causes coexist independently at each harmonic level, giving rise to complex governance needs involving intertwined causes and concurrent frequency bands.

[0003] The traditional on-site harmonic current cancellation mechanism of active power filters (APFs) is no longer suitable for the current harmonic evolution, offering minimal improvement in harmonic voltage. Direct control of bus harmonic voltage is now necessary. Currently, active harmonic resistor technology is the most effective means to meet these requirements. The relationship between its internal virtual harmonic resistance value and external impedance is crucial to ensuring effective control. However, the complexity and difficulty in data collection in actual distribution networks pose significant challenges to its application.

[0004] Existing technologies approach the problem from the perspective of the single-peak characteristics of harmonic power, employing perturbation-observation methods or particle swarm optimization algorithms to search for the resistance value corresponding to the highest point of each harmonic power, using this as the optimal value of the virtual harmonic resistance to address the issue of unknown grid parameters. However, this approach suffers from uncertain and excessive iteration steps, easily increasing the risk of system disturbance. It can only obtain values ​​with the same external impedance, limiting the harmonic voltage improvement rate to 29.3%~50%, failing to specify control targets, and not achieving the expected mitigation effect in some scenarios.

[0005] To enable active harmonic resistors to adaptively manage harmonic voltage according to specified control objectives under conditions of unknown grid parameters and time-varying operating states, an adaptive harmonic voltage precision control method with external impedance sensing is proposed. Based on the sensing of external impedance, the active harmonic resistor device adaptively determines the virtual harmonic resistance according to the control objectives of each harmonic voltage, so as to meet the universal requirements in different application scenarios. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the aforementioned shortcomings of existing technologies, this invention provides an adaptive harmonic voltage precision control method with external impedance sensing. This method effectively overcomes the limitations of existing technologies, which can only manage each harmonic voltage through multiple optimization iterations when grid parameters are unknown and operating conditions are time-varying.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention provides the following technical solution: An adaptive harmonic voltage precision control method with external impedance sensing includes the following steps: S1. Based on the frequency domain analysis results when the active harmonic resistor device is not connected, determine the harmonic voltage that needs to be controlled and the initial external impedance angle cosine value of the harmonic that needs to be controlled. S2. Calculate the virtual harmonic resistance given for the first and second time for the active harmonic resistor device, and calculate the corresponding harmonic voltage suppression ratio. S3. Based on the results of the two active disturbances, sense the actual external impedance angle cosine value and the actual external impedance amplitude of the active harmonic resistor device connection point that needs to manage harmonics, calculate the final virtual harmonic resistor according to the control target, so that the active harmonic resistor device can adaptively complete the precise management of harmonic voltage. S4. When the harmonic voltage changes over time, the actual external impedance angle cosine value and actual external impedance amplitude of the active harmonic resistor connection point that need to manage the harmonics are re-sensed. The new final virtual harmonic resistor is adaptively solved according to the control target to maintain accurate management of the harmonic voltage.

[0010] Preferably, in S1, based on the frequency domain analysis results when the active harmonic resistor device is not connected, the harmonic voltage to be mitigated and the initial external impedance angle cosine value of the harmonic to be mitigated are determined, including: S11. Fourier transform is used to perform frequency domain decomposition on the voltage and current at the point of common coupling collected when the active harmonic resistor device is not connected, to obtain the fundamental voltage amplitude U. p (1) with phase θ u (1) Fundamental current amplitude I p (1) with phase θ i (1), and the amplitude of the h-th harmonic voltage U p (h) and current amplitude I p (h); S12. Take the harmonic voltage with a content rate reaching the treatment threshold as the harmonic voltage to be treated, and generate an enable signal to activate the processing channel of the harmonic voltage to be treated in the active harmonic resistor device. S13. Collect grid-side parameters at the connection point of the active harmonic resistor device, including the nominal voltage U. N System short-circuit capacity S scand resistance-to-reactance ratio R / X Calculate the initial impedance r1(h) + jx1(h) of the h-th harmonic on the grid side: ; in, r 1( h ) for the power grid side h Second harmonic resistance components x 1( h ) for the power grid side h Subharmonic reactance component; S14, Utilizing the fundamental voltage amplitude U p (1) and the amplitude of the fundamental current I p (1) ratio, and fundamental voltage phase θ u (1) and the phase θ of the fundamental current i (1) Calculate the initial impedance r2(h) + jx2(h) of the h-th harmonic on the load side: ; in, r 2( h ) is the load side h Second harmonic resistance components x 2( h ) is the load side h Subharmonic reactance component; S15. Based on the initial impedance calculation results of the h-th harmonic on the grid side and the load side, calculate the initial external impedance cosθ value of the active harmonic resistor connection point that needs to suppress harmonics. e,r (h): .

[0011] Preferably, in S2, the virtual harmonic resistance of the active harmonic resistor device is calculated for the first time, and the corresponding harmonic voltage suppression ratio is calculated, including: S21. Calculate the impedance amplitude R of the h-th harmonic to be controlled by using the ratio of the voltage amplitude to the current amplitude of the h-th harmonic to be controlled. p (h); S22. Set the target suppression ratio α for the first harmonic voltage. g1 (h), combined with the initial external impedance angle cosθ e,r (h) Calculate the ratio n1(h) of the first given virtual harmonic resistance to the external impedance amplitude: ; Wherein, k1(h) is the ratio of the first given virtual harmonic resistance to the initial virtual harmonic resistance. Since the active harmonic resistance device is initially in an unconnected state, the initial virtual harmonic resistance is assumed to be infinite, and k1(h) can be taken as 0 at this time. S23. Calculate the virtual harmonic resistance R given for the first time. a,1 (h) After completing the online update, connect and run the active harmonic resistor device: ; Where || represents the parallel operation; S24. Calculate the difference between the actual suppression ratio of the h-th harmonic voltage that needs to be suppressed at time t and the values ​​of the actual suppression ratios over adjacent time intervals. : ; in, , They are time t and t, respectively The actual suppression ratio of the h-th harmonic voltage that needs to be addressed at all times. For time intervals; When the actual suppression ratio of the h-th harmonic voltage that needs to be controlled is satisfied at time t1 and When, the actual suppression ratio of the h-th harmonic voltage that needs to be controlled at time t1 is... The harmonic voltage suppression ratio α1(h) is the result of the first given virtual harmonic resistance.

[0012] Preferably, in S2, the virtual harmonic resistance of the active harmonic resistor device is calculated a second time, and the corresponding harmonic voltage suppression ratio is calculated, including: S25. Set the target suppression ratio α for the second harmonic voltage. g2 (h), combined with the initial external impedance angle cosθ e,r (h) Calculate the ratio n2(h) of the second given virtual harmonic resistance to the external impedance amplitude: ; Wherein, k2(h) is the ratio of the second given virtual harmonic resistance to the initial virtual harmonic resistance. Since the active harmonic resistance device is initially in an unconnected state, the initial virtual harmonic resistance is assumed to be infinite, and k2(h) can be taken as 0 at this time. S26. Calculate the second given virtual harmonic resistance R. a,2 (h), and update online: ; Wherein, λ(h) is the adjustment coefficient for the actual suppression ratio of the h-th harmonic voltage that needs to be controlled. ; S27. Based on S24, calculate the difference ∆α between adjacent time intervals in the actual suppression ratio of the h-th harmonic voltage that needs to be suppressed at time t. t (h) When the actual suppression ratio of the h-th harmonic voltage that needs to be controlled is satisfied at time t2. When, the actual suppression ratio of the h-th harmonic voltage that needs to be controlled at time t2 is... The harmonic voltage suppression ratio α2(h) is caused by the second given virtual harmonic resistance.

[0013] Preferably, in S3, based on the results of two active disturbances, the actual external impedance angle cosine value and the actual external impedance amplitude at the active harmonic resistor connection point that need to manage harmonics are sensed. The final virtual harmonic resistor is calculated based on the control target, enabling the active harmonic resistor to adaptively and accurately manage harmonic voltages, including: S31. Using the virtual harmonic resistance R given for the first time. a,1 (h), the harmonic voltage suppression ratio α1(h) caused by the first given virtual harmonic resistor, and the second given virtual harmonic resistor R a,2 (h) The harmonic voltage suppression ratio α2(h) caused by the second given virtual harmonic resistor is used to calculate the actual external impedance angle cosθ value that needs to be mitigated at the connection point of the active harmonic resistor device. e,a (h): ; Among them, a1(h), a2(h), b1(h), b2(h), c(h), These are all intermediate parameters, in which case k1(h) and k2(h) are both 0: ; S32, Using the cosine value of the actual external impedance angle, cosθ e,a Calculate the harmonic voltage suppression ratio α2(h) caused by the second given virtual harmonic resistor, calculate the actual ratio n2'(h) of the second given virtual harmonic resistor to the external impedance amplitude, and then calculate the actual external impedance amplitude |Z| required to suppress harmonics at the active harmonic resistor connection point. e,a (h)|: ; S33. Set the target value HRU for controlling the voltage content of the h-th harmonic. g (h), combined with the measured initial value HRU of the h-th harmonic voltage content when the active harmonic resistor device is not connected. m (h) Calculate the final harmonic voltage target suppression ratio α g,z (h): ; S34. Calculate the final virtual harmonic resistance R. a,z(h) and perform online updates to adaptively and accurately manage harmonic voltages: .

[0014] Preferably, when the harmonic voltage in S4 changes over time, the actual external impedance angle cosine value and actual external impedance amplitude at the active harmonic resistor connection point needing harmonic mitigation are re-sensed. A new final virtual harmonic resistor is adaptively calculated based on the control objective to maintain accurate harmonic voltage mitigation, including: S41. Continuously monitor each harmonic voltage. When the increase in the content rate of a certain harmonic voltage exceeds the change threshold and the content rate reaches the treatment threshold within a set time period, it is determined that the harmonic voltage has undergone a significant change that requires treatment. S42. If the harmonic voltage is not within the range of harmonic voltages that need to be controlled in S12, then for the harmonic voltage, the active harmonic resistor device is equivalent to being in an unconnected state. By executing S1~S3, adaptive control of the harmonic voltage can be achieved. S43. If the harmonic voltage is within the range of harmonic voltages that need to be controlled in S12, then the final virtual harmonic resistance R will be... a,z (h) is used as the initial virtual harmonic resistance, and k1(h) = 1.1 and k2(h) = 0.9 are set. Calculate the new virtual harmonic resistances R given for the first and second time. a,1re (h), R a,2re (h): ; By executing S24, the harmonic voltage suppression ratio α caused by the new first-given virtual harmonic resistance is calculated. 1re (h); By executing S27, calculate the harmonic voltage suppression ratio α caused by the new second given virtual harmonic resistor. 2re (h); S44. By executing S31, calculate the actual external impedance angle cosθ value of the new active harmonic resistor connection point that needs to suppress harmonics. e,are (h); By executing S32, calculate the actual external impedance amplitude |Z| required to suppress harmonics at the new active harmonic resistor connection point. e,are (h)|; S45. Calculate the new final virtual harmonic resistance R. a,zre (h) and perform online updates to achieve precise control of the harmonic voltage once again: ; Wherein, n0(h) is the initial virtual harmonic resistor and the actual external impedance amplitude |Z| required to mitigate harmonics at the connection point of the active harmonic resistor device. e,are The ratio of (h)| .

[0015] (III) Beneficial Effects

[0016] Compared with existing technologies, the adaptive harmonic voltage precision control method with external impedance sensing provided by this invention has the following advantages: 1) Active harmonic resistor devices can control harmonic voltage by changing the impedance of the power distribution network, thereby reducing the background harmonic voltage penetration, reducing the harmonic current injected into the power grid, and suppressing the degree of resonance amplification. 2) By simply providing the active harmonic resistor device with two virtual harmonic resistances and actively changing the harmonic voltage state, the device can accurately sense the cosine value of the external impedance angle and the external impedance amplitude at the point where harmonics need to be controlled when connected to the distribution network, and the disturbance to the distribution network is controllable throughout the process. 3) With accurate perception of external impedance, the method can achieve precise and independent control of each harmonic voltage according to the specified control target based on the analytical relationship between the virtual harmonic resistance and the harmonic voltage suppression ratio of the active harmonic resistor device. Compared with the existing methods, which can only achieve up to half of the control effect, this method is not limited. 4) The active harmonic resistor device using this method can achieve precise control of single or multiple harmonic voltages within the error range in complex scenarios with multiple sources and resonances without the need for source tracing and resonance identification. Compared with existing methods, it has more flexible control capabilities, a wider suppression range, and better scenario adaptability, and can easily and efficiently achieve better control results. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0018] Figure 1 This is a schematic diagram of the process of the present invention; Figure 2 This is a schematic diagram illustrating the working principle of the active harmonic resistor device of the present invention; Figure 3 The graph shows the variation of the harmonic voltage content of each harmonic during the commissioning, sensing and mitigation process of an active harmonic resistor device in a multi-source harmonic scenario. Figure 4 The voltage waveform diagram before the active harmonic resistor device is connected for treatment in a multi-source harmonic scenario; Figure 5 The voltage waveform diagram after the active harmonic resistor device is connected for treatment in a multi-source harmonic scenario; Figure 6This is a graph showing the variation of harmonic voltage content during the commissioning, sensing, and mitigation process of an active harmonic resistor device in a time-varying harmonic scenario. Figure 7 This is a bar chart comparing the harmonic voltage content before and after treatment by an active harmonic resistor device in a time-varying harmonic scenario. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0020] The following describes the specific process of the adaptive harmonic voltage precision control method with external impedance sensing provided by this invention, using a specific example (e.g.) Figure 1 (as shown) and technical effects.

[0021] S1. Based on the frequency domain analysis results when the active harmonic resistor device is not connected, determine the harmonic voltage that needs to be mitigated and the initial external impedance angle cosine value of the harmonics that need to be mitigated, including: S11. Fourier transform (single cycle) is used to perform frequency domain decomposition on the voltage and current at the point of common coupling collected when the active harmonic resistor device is not connected, to obtain the fundamental voltage amplitude U. p (1) with phase θ u (1) Fundamental current amplitude I p (1) with phase θ i (1), and the amplitude of the h-th harmonic voltage U p (h) and current amplitude I p (h); S12. Harmonic voltages with a content rate reaching the treatment threshold (the value can be taken with reference to the limit specified in GB / T 14549, or it can be set manually, with 0.5% recommended) are taken as harmonic voltages that need to be treated, and an enable signal is generated to activate the processing channel of the harmonic voltages that need to be treated in the active harmonic resistor device. S13. Collect grid-side parameters at the connection point of the active harmonic resistor device, including the nominal voltage U. N System short-circuit capacity S sc and resistance-to-reactance ratio R / X Calculate the initial impedance r1(h) + jx1(h) of the h-th harmonic on the grid side: ; in, r 1(h ) for the power grid side h Second harmonic resistance components x 1( h ) for the power grid side h Subharmonic reactance component; S14, Utilizing the fundamental voltage amplitude U p (1) and the amplitude of the fundamental current I p (1) ratio, and fundamental voltage phase θ u (1) and the phase θ of the fundamental current i (1) Calculate the initial impedance r2(h) + jx2(h) of the h-th harmonic on the load side: ; in, r 2( h ) is the load side h Second harmonic resistance components x 2( h ) is the load side h Subharmonic reactance component; S15. Based on the initial impedance calculation results of the h-th harmonic on the grid side and the load side, calculate the initial external impedance cosθ value of the active harmonic resistor connection point that needs to suppress harmonics. e,r (h): .

[0022] S2. Calculate the virtual harmonic resistances given for the first and second time for the active harmonic resistor device, and calculate the corresponding harmonic voltage suppression ratios, including: S21. Calculate the impedance amplitude R of the h-th harmonic to be controlled by using the ratio of the voltage amplitude to the current amplitude of the h-th harmonic to be controlled. p (h); S22. Set the target suppression ratio α for the first harmonic voltage. g1 (h) (To ensure that the single adjustment disturbance of the active harmonic resistor device is controlled within 10% during the active virtual harmonic resistance setting stage, a value of 0.9 is recommended), combined with the initial external impedance angle cosθ. e,r (h) Calculate the ratio n1(h) of the first given virtual harmonic resistance to the external impedance amplitude: ; Wherein, k1(h) is the ratio of the first given virtual harmonic resistance to the initial virtual harmonic resistance. Since the active harmonic resistance device is initially in an unconnected state, the initial virtual harmonic resistance is assumed to be infinite, and k1(h) can be taken as 0 at this time. S23. Calculate the virtual harmonic resistance R given for the first time. a,1(h) After completing the online update, connect and run the active harmonic resistor device: ; Where || represents the parallel operation; S24. Calculate the difference between the actual suppression ratio of the h-th harmonic voltage that needs to be suppressed at time t and the values ​​of the actual suppression ratios over adjacent time intervals. : ; in, , They are time t and t, respectively The actual suppression ratio of the h-th harmonic voltage that needs to be addressed at all times. The time interval (default is 20ms, but you can also perform appropriate smoothing on the single-cycle FFT results by increasing the time interval to avoid random interference affecting ∆α) t (h) Convergence judgment); When the actual suppression ratio of the h-th harmonic voltage that needs to be controlled is satisfied at time t1 and When, the actual suppression ratio of the h-th harmonic voltage that needs to be controlled at time t1 is... The harmonic voltage suppression ratio α1(h) is the result of the first given virtual harmonic resistance; S25. Set the target suppression ratio α for the second harmonic voltage. g2 (h) (when) At that time, the target suppression ratio of the second harmonic voltage α g2 (h) is set to ;when At that time, the target suppression ratio of the second harmonic voltage α g2 (h) is set to Combined with the initial external impedance angle cosθ e,r (h) Calculate the ratio n2(h) of the second given virtual harmonic resistance to the external impedance amplitude: ; Wherein, k2(h) is the ratio of the second given virtual harmonic resistance to the initial virtual harmonic resistance. Since the active harmonic resistance device is initially in an unconnected state, the initial virtual harmonic resistance is assumed to be infinite, and k2(h) can be taken as 0 at this time. S26. Calculate the second given virtual harmonic resistance R. a,2 (h), and update online: ; Wherein, λ(h) is the adjustment coefficient for the actual suppression ratio of the h-th harmonic voltage that needs to be controlled. ; S27. Based on S24, calculate the difference ∆α between adjacent time intervals in the actual suppression ratio of the h-th harmonic voltage that needs to be suppressed at time t. t (h) When the actual suppression ratio of the h-th harmonic voltage that needs to be controlled is satisfied at time t2. When, the actual suppression ratio of the h-th harmonic voltage that needs to be controlled at time t2 is... The harmonic voltage suppression ratio α2(h) is caused by the second given virtual harmonic resistance.

[0023] S3. Based on the results of the two active disturbances, sense the actual external impedance angle cosine value and actual external impedance amplitude at the active harmonic resistor connection point that need to manage harmonics. Calculate the final virtual harmonic resistance according to the control target, enabling the active harmonic resistor to adaptively and accurately manage harmonic voltages, including: S31. Using the virtual harmonic resistance R given for the first time. a,1 (h), the harmonic voltage suppression ratio α1(h) caused by the first given virtual harmonic resistor, and the second given virtual harmonic resistor R a,2 (h) The harmonic voltage suppression ratio α2(h) caused by the second given virtual harmonic resistor is used to calculate the actual external impedance angle cosθ value that needs to be mitigated at the connection point of the active harmonic resistor device. e,a (h): ; Among them, a1(h), a2(h), b1(h), b2(h), c(h), These are all intermediate parameters, in which case k1(h) and k2(h) are both 0: ; S32, Using the cosine value of the actual external impedance angle, cosθ e,a Calculate the harmonic voltage suppression ratio α2(h) caused by the second given virtual harmonic resistor, calculate the actual ratio n2'(h) of the second given virtual harmonic resistor to the external impedance amplitude, and then calculate the actual external impedance amplitude |Z| required to suppress harmonics at the active harmonic resistor connection point. e,a (h)|: ; S33. Set the target value HRU for controlling the voltage content of the h-th harmonic. g (h) (can be set to the same or different), combined with the measured initial value HRU of the h-th harmonic voltage content when the active harmonic resistor is not connected. m (h) Calculate the final harmonic voltage target suppression ratio α g,z (h): ; S34. Calculate the final virtual harmonic resistance R.a,z (h) and perform online updates to adaptively and accurately manage harmonic voltages: .

[0024] S4. When harmonic voltage changes over time, the actual external impedance angle cosine value and actual external impedance amplitude at the active harmonic resistor connection point needing harmonic mitigation are re-sensed. Based on the control objective, a new final virtual harmonic resistance is adaptively calculated to maintain accurate harmonic voltage mitigation, including: S41. When the operating status of the power distribution network source and load (such as load, new energy power generation, reactive power compensation commissioning, etc.) changes in external impedance and increases in harmonic current due to time-varying conditions, the active harmonic resistor device will be unable to maintain the original mitigation effect or new harmonics that need to be mitigated will appear, ultimately causing voltage changes. In order to deal with the above situation, the voltage of each harmonic is continuously monitored. When the increase in the content rate of a certain harmonic voltage exceeds the change threshold (not less than 20%) and the content rate reaches the mitigation threshold within a set time period (not less than 1 hour to avoid short-term random interference), it is determined that the harmonic voltage has undergone a significant change that needs to be mitigated. S42. If the harmonic voltage is not within the range of harmonic voltages that need to be controlled in S12, then for the harmonic voltage, the active harmonic resistor device is equivalent to being in an unconnected state. By executing S1~S3, adaptive control of the harmonic voltage can be achieved. S43. If the harmonic voltage is within the range of harmonic voltages that need to be controlled in S12, then the final virtual harmonic resistance R will be... a,z (h) is used as the initial virtual harmonic resistance, and k1(h) = 1.1 and k2(h) = 0.9 are set. Calculate the new virtual harmonic resistances R given for the first and second time. a,1re (h), R a,2re (h): ; By executing S24, the harmonic voltage suppression ratio α caused by the new first-given virtual harmonic resistance is calculated. 1re (h); By executing S27, calculate the harmonic voltage suppression ratio α caused by the new second given virtual harmonic resistor. 2re (h); S44. By executing S31, calculate the actual external impedance angle cosθ value of the new active harmonic resistor connection point that needs to suppress harmonics. e,are (h); By executing S32, calculate the actual external impedance amplitude |Z| required to suppress harmonics at the new active harmonic resistor connection point. e,are (h)|; S45. Calculate the new final virtual harmonic resistance R. a,zre (h) and perform online updates to achieve precise control of the harmonic voltage once again: ; Wherein, n0(h) is the initial virtual harmonic resistor and the actual external impedance amplitude |Z| required to mitigate harmonics at the connection point of the active harmonic resistor device. e,are The ratio of (h)| .

[0025] To better illustrate the technical solution of this application, the above process will be explained in detail below with specific examples.

[0026] Figure 2 This is a schematic diagram illustrating the working principle of the active harmonic resistor device of the present invention. The device consists of a signal acquisition and conversion module, a harmonic mitigation judgment module, a harmonic voltage separation module, an active virtual harmonic resistor adaptive calculation module, a DC voltage control module, and an AC current control module. Among these, the active virtual harmonic resistor adaptive calculation module is the core functional module, mainly composed of the following three parts: 1) The initial value calculation module calculates the initial external impedance angle cosine value in S1; 2) The external impedance active sensing module realizes the measurement and analysis of the virtual harmonic resistance and corresponding harmonic voltage disturbance given twice in S2. On this basis, it realizes the sensing of the actual external impedance angle cosine value and the actual external impedance amplitude in S3. 3) The virtual harmonic resistance calculation module realizes the solution of the corresponding final virtual harmonic resistance in S3 based on the actual external impedance angle cosine value, the actual external impedance amplitude and the control target.

[0027] The simulation parameters of the active harmonic resistor device connected to a 0.4kV distribution network containing background harmonics, nonlinear loads, linear loads, and unloaded cables (constructed resonance) are shown in Table 1. Table 1 Simulation Parameter Table

[0028] During simulation, the linear load is assumed to be in operation. The harmonic scenarios requiring mitigation can be set according to Table 2. In complex scenarios involving background harmonics, nonlinear loads, and resonant amplification, the voltage waveform at the common connection point of the simulation model is measured and FFT analysis is performed to obtain the harmonic voltage changes and mitigation effects during the control process of the active harmonic resistor device. During simulation, the target value for mitigating the h-th harmonic voltage content is set to HRU. g (h) = 0.5%.

[0029] Table 2 Harmonic Mitigation Scenarios

[0030] For Scenario 1: When background harmonics from the upstream power grid coexist with harmonics generated by nonlinear loads, the adaptive control process and effect of the active harmonic resistor device are as follows: Figures 3 to 5 As shown, the device can simultaneously and precisely manage 5th, 7th, 11th, and 13th harmonic voltages from different sources and with the same control objective. The voltage waveform distortion is significantly improved, and the maximum control error does not exceed 10%. This proves that the device can effectively manage each harmonic voltage by quantitatively changing the impedance of the distribution network through active harmonic resistors.

[0031] For scenario 2: when multiple harmonics coexist and new harmonic voltages requiring mitigation arise at a certain moment due to resonant amplification, the adaptive control process and effect of the active harmonic resistor device are as follows: Figure 6 and Figure 7 As shown, the device can independently and synchronously perform precise control of the 11th and 13th harmonic voltages caused by nonlinear loads that exceed the control threshold, with a maximum control error not exceeding 10%. When an unloaded cable is put into operation, changes in external impedance cause the 23rd and 25th harmonics to be amplified by resonance, resulting in abrupt changes exceeding the change threshold and reaching the control threshold. The device can enable the corresponding processing channel, and the harmonic voltage suppression ratio caused by the first given virtual harmonic resistor is less than 0.8. It can set the second given virtual harmonic resistor according to the requirement of increasing the suppression ratio and achieve the expected effect, avoiding the risk of excessive disturbance caused by an excessively low suppression ratio. Finally, it realizes the perception of the external impedance after resonance, and then completes the precise control of the new 23rd and 25th harmonic voltages caused by resonance amplification according to the control target, with a maximum control error not exceeding 10%, and without interfering with the control of the 11th and 13th harmonic voltages, verifying the device's strong adaptability in complex harmonic dynamic change scenarios.

[0032] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An adaptive harmonic voltage precision control method with external impedance sensing, characterized in that: Includes the following steps: S1. Based on the frequency domain analysis results when the active harmonic resistor device is not connected, determine the harmonic voltage that needs to be controlled and the initial external impedance angle cosine value of the harmonic that needs to be controlled. S2. Calculate the virtual harmonic resistance given for the first and second time for the active harmonic resistor device, and calculate the corresponding harmonic voltage suppression ratio. S3. Based on the results of the two active disturbances, sense the actual external impedance angle cosine value and the actual external impedance amplitude of the active harmonic resistor device connection point that needs to manage harmonics, calculate the final virtual harmonic resistor according to the control target, so that the active harmonic resistor device can adaptively complete the precise management of harmonic voltage. S4. When the harmonic voltage changes over time, the actual external impedance angle cosine value and actual external impedance amplitude of the active harmonic resistor connection point that need to manage the harmonics are re-sensed. The new final virtual harmonic resistor is adaptively solved according to the control target to maintain accurate management of the harmonic voltage.

2. The adaptive harmonic voltage precision control method with external impedance sensing according to claim 1, characterized in that: Based on the frequency domain analysis results when the active harmonic resistor device is not connected, S1 determines the harmonic voltage to be mitigated and the initial external impedance angle cosine value of the harmonics to be mitigated, including: S11. Fourier transform is used to perform frequency domain decomposition on the voltage and current at the point of common coupling collected when the active harmonic resistor device is not connected, to obtain the fundamental voltage amplitude U. p (1) with phase θ u (1) Fundamental current amplitude I p (1) with phase θ i (1), and the amplitude of the h-th harmonic voltage U p (h) and current amplitude I p (h); S12. Take the harmonic voltage with a content rate reaching the treatment threshold as the harmonic voltage to be treated, and generate an enable signal to activate the processing channel of the harmonic voltage to be treated in the active harmonic resistor device. S13. Collect grid-side parameters at the connection point of the active harmonic resistor device, including the nominal voltage U. N System short-circuit capacity S sc and resistance-to-reactance ratio R / X Calculate the initial impedance r1(h) + jx1(h) of the h-th harmonic on the grid side: ； in, r 1( h ) for the power grid side h Second harmonic resistance components x 1( h ) for the power grid side h Subharmonic reactance component; S14, Utilizing the fundamental voltage amplitude U p (1) and the amplitude of the fundamental current I p (1) ratio, and fundamental voltage phase θ u (1) and the phase θ of the fundamental current i (1) Calculate the initial impedance r2(h) + jx2(h) of the h-th harmonic on the load side: ； in, r 2( h ) is the load side h Second harmonic resistance components x 2( h ) is the load side h Subharmonic reactance component; S15. Based on the initial impedance calculation results of the h-th harmonic on the grid side and the load side, calculate the initial external impedance cosθ value of the active harmonic resistor connection point that needs to suppress harmonics. e,r (h): 。 3. The adaptive harmonic voltage precision control method with external impedance sensing according to claim 2, characterized in that: S2 calculates the virtual harmonic resistance of the active harmonic resistor device given for the first time, and calculates the corresponding harmonic voltage suppression ratio, including: S21. Calculate the impedance amplitude R of the h-th harmonic to be controlled by using the ratio of the voltage amplitude to the current amplitude of the h-th harmonic to be controlled. p (h); S22. Set the target suppression ratio α for the first harmonic voltage. g1 (h), combined with the initial external impedance angle cosθ e,r (h) Calculate the ratio n1(h) of the first given virtual harmonic resistance to the external impedance amplitude: ； Wherein, k1(h) is the ratio of the first given virtual harmonic resistance to the initial virtual harmonic resistance. Since the active harmonic resistance device is initially in an unconnected state, the initial virtual harmonic resistance is assumed to be infinite, and k1(h) can be taken as 0 at this time. S23. Calculate the virtual harmonic resistance R given for the first time. a,1 (h) After completing the online update, connect and run the active harmonic resistor device: ； Where || represents the parallel operation; S24. Calculate the difference between the actual suppression ratio of the h-th harmonic voltage that needs to be suppressed at time t and the values ​​of the actual suppression ratios over adjacent time intervals. : ； in, , They are time t and t, respectively The actual suppression ratio of the h-th harmonic voltage that needs to be addressed at all times. For time intervals; When the actual suppression ratio of the h-th harmonic voltage that needs to be controlled is satisfied at time t1 and When, the actual suppression ratio of the h-th harmonic voltage that needs to be controlled at time t1 is... The harmonic voltage suppression ratio α1(h) is the result of the first given virtual harmonic resistance.

4. The adaptive harmonic voltage precision control method with external impedance sensing according to claim 3, characterized in that: S2 calculates the virtual harmonic resistance of the active harmonic resistor device given for the second time, and calculates the corresponding harmonic voltage suppression ratio, including: S25. Set the target suppression ratio α for the second harmonic voltage. g2 (h), combined with the initial external impedance angle cosθ e,r (h) Calculate the ratio n2(h) of the second given virtual harmonic resistance to the external impedance amplitude: ； Wherein, k2(h) is the ratio of the second given virtual harmonic resistance to the initial virtual harmonic resistance. Since the active harmonic resistance device is initially in an unconnected state, the initial virtual harmonic resistance is assumed to be infinite, and k2(h) can be taken as 0 at this time. S26. Calculate the second given virtual harmonic resistance R. a,2 (h), and update online: ； Wherein, λ(h) is the adjustment coefficient for the actual suppression ratio of the h-th harmonic voltage that needs to be controlled. ; S27. Based on S24, calculate the difference ∆α between adjacent time intervals in the actual suppression ratio of the h-th harmonic voltage that needs to be suppressed at time t. t (h) When the actual suppression ratio of the h-th harmonic voltage that needs to be controlled is satisfied at time t2. When, the actual suppression ratio of the h-th harmonic voltage that needs to be controlled at time t2 is... The harmonic voltage suppression ratio α2(h) is caused by the second given virtual harmonic resistance.

5. The adaptive harmonic voltage precision control method with external impedance sensing according to claim 4, characterized in that: Based on the results of two active disturbances, S3 senses the actual external impedance angle cosine value and actual external impedance amplitude at the active harmonic resistor connection point that need to manage harmonics. It then calculates the final virtual harmonic resistance based on the control objective, enabling the active harmonic resistor to adaptively and accurately manage harmonic voltages, including: S31. Using the virtual harmonic resistance R given for the first time. a,1 (h), the harmonic voltage suppression ratio α1(h) caused by the first given virtual harmonic resistor, and the second given virtual harmonic resistor R a,2 (h) The harmonic voltage suppression ratio α2(h) caused by the second given virtual harmonic resistor is used to calculate the actual external impedance angle cosθ value that needs to be mitigated at the connection point of the active harmonic resistor device. e,a (h): ； Among them, a1(h), a2(h), b1(h), b2(h), c(h), These are all intermediate parameters, in which case k1(h) and k2(h) are both 0: ； S32, Using the cosine value of the actual external impedance angle, cosθ e,a Calculate the harmonic voltage suppression ratio α2(h) caused by the second given virtual harmonic resistor, calculate the actual ratio n2'(h) of the second given virtual harmonic resistor to the external impedance amplitude, and then calculate the actual external impedance amplitude |Z| required to suppress harmonics at the active harmonic resistor connection point. e,a (h)|: ； S33. Set the target value HRU for controlling the voltage content of the h-th harmonic. g (h), combined with the measured initial value HRU of the h-th harmonic voltage content when the active harmonic resistor device is not connected. m (h) Calculate the final harmonic voltage target suppression ratio α g,z (h): ； S34. Calculate the final virtual harmonic resistance R. a,z (h) and perform online updates to adaptively and accurately manage harmonic voltages: 。 6. The adaptive harmonic voltage precision control method with external impedance sensing according to claim 5, characterized in that: When the harmonic voltage in S4 changes over time, the actual external impedance angle cosine value and actual external impedance amplitude at the active harmonic resistor connection point need to be sensed again. Based on the control objective, a new final virtual harmonic resistance is adaptively calculated to maintain accurate harmonic voltage control, including: S41. Continuously monitor each harmonic voltage. When the increase in the content rate of a certain harmonic voltage exceeds the change threshold and the content rate reaches the treatment threshold within a set time period, it is determined that the harmonic voltage has undergone a significant change that requires treatment. S42. If the harmonic voltage is not within the range of harmonic voltages that need to be controlled in S12, then for the harmonic voltage, the active harmonic resistor device is equivalent to being in an unconnected state. By executing S1~S3, adaptive control of the harmonic voltage can be achieved. S43. If the harmonic voltage is within the range of harmonic voltages that need to be controlled in S12, then the final virtual harmonic resistance R will be... a,z (h) is used as the initial virtual harmonic resistance, and k1(h) = 1.1 and k2(h) = 0.9 are set. Calculate the new virtual harmonic resistances R given for the first and second time. a,1re (h), R a,2re (h): ； By executing S24, the harmonic voltage suppression ratio α caused by the new first-given virtual harmonic resistance is calculated. 1re (h); By executing S27, calculate the harmonic voltage suppression ratio α caused by the new second given virtual harmonic resistor. 2re (h); S44. By executing S31, calculate the actual external impedance angle cosθ value of the new active harmonic resistor connection point that needs to suppress harmonics. e,are (h); By executing S32, calculate the actual external impedance amplitude |Z| required to suppress harmonics at the new active harmonic resistor connection point. e,are (h)|; S45. Calculate the new final virtual harmonic resistance R. a,zre (h) and perform online updates to achieve precise control of the harmonic voltage once again: ； Wherein, n0(h) is the initial virtual harmonic resistor and the actual external impedance amplitude |Z| required to mitigate harmonics at the connection point of the active harmonic resistor device. e,are The ratio of (h)| .

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