A method and device for suppressing harmonic output of a nonlinear load of an auxiliary converter

Abstract

The embodiment of the present application relates to a kind of auxiliary converter nonlinear load output harmonic suppression method, comprising: obtaining the three-phase output current and three-phase output voltage of auxiliary converter;Three-phase output current is handled, and the phase difference of fundamental wave and harmonic is generated;According to the rule and phase difference of pre-set, harmonic phase compensation is carried out, and the harmonic phase to be compensated is generated;Three-phase output voltage is handled, and fundamental wave voltage amplitude and harmonic voltage amplitude are generated;According to the harmonic phase to be compensated, fundamental wave voltage amplitude and harmonic voltage amplitude, auxiliary converter pulse is generated, to realize the harmonic of the nonlinear load output of auxiliary converter is inhibited.

Description

Technical Field

[0001] This invention relates to the field of control technology, and in particular to a method and apparatus for suppressing harmonics in the output of an auxiliary converter nonlinear load. Background Technology

[0002] Auxiliary converters convert high-voltage direct current (HVDC) into three-phase alternating current (AC) to supply medium-voltage AC loads on trains. The quality of their output voltage waveform is a crucial indicator of converter performance. The non-sinusoidal currents generated by non-linear loads (such as variable frequency air conditioners and bridge rectifier loads) in rail transit vehicles contain numerous low-order harmonics (primarily the 5th and 7th harmonics), severely polluting the medium-voltage AC bus, causing voltage distortion, and affecting the normal operation of other electrical equipment. Current harmonics from non-linear loads can cause isolation transformers to overheat, reducing their operating efficiency. These harmonics can also cause partial discharge in the capacitor's dielectric, leading to internal heating, increased temperature rise, and potential mechanical damage to the dielectric due to mechanical resonance. Furthermore, high-order components of the current harmonics can interfere with communication and control systems, affecting system operation.

[0003] To address the voltage distortion problem of medium-voltage AC bus caused by nonlinear loads, the literature "Research on Fault Ride Control Strategy of Direct-Drive Wind Turbine Generator" employs multi-synchronous rotating coordinate transformation to decouple and filter the decomposed 5th and 7th harmonic components, eliminating the influence of harmonic harmonic components. However, the decoupling process is complex, and excessive low-pass filtering reduces the system's dynamic response speed, which is not conducive to engineering applications. The literature "Research on Harmonic Elimination of Cascaded Inverters Based on Harmonic Injection Method" proposes a method for eliminating harmonics based on the equal area method and harmonic injection. However, this method requires solving differential equations and performing multiple iterations, resulting in a large computational load and complex engineering implementation. The patent "A Control System and Control Method for a Parallel Converter System," based on "Research on Fault Ride Control Strategy of Direct-Drive Wind Turbine Generator," decouples and extracts the 5th and 7th harmonic components, using four sets of PID controllers to control the 5th and 7th harmonic voltages on the D-axis and Q-axis respectively, with the outputs of the four PID controllers being completely independent. According to mathematical knowledge, amplitude, frequency, and phase are the three essential elements constituting a sinusoidal signal. This patent uses the output values ​​of four sets of PID controllers to simultaneously constrain and compensate for the amplitude and phase of harmonics. Under specific working conditions, it can achieve harmonic compensation. However, with different load capacities, the output results of the four sets of PID controllers are heavily coupled, which can easily lead to oscillation and compensation failure. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method and apparatus for suppressing harmonics in the output of an auxiliary converter nonlinear load. This method simplifies decoupling, filtering, and control logic, reduces filtering steps, and improves the dynamic response speed of the system.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for suppressing harmonics at the output of an auxiliary converter nonlinear load, comprising:

[0006] Obtain the three-phase output current and three-phase output voltage of the auxiliary converter;

[0007] The three-phase output current is processed to generate the phase difference between the fundamental wave and the harmonics;

[0008] Harmonic phase compensation is performed according to preset rules and phase differences to generate the harmonic phase to be compensated;

[0009] The three-phase output voltage is processed to generate the fundamental voltage amplitude and harmonic voltage amplitude;

[0010] Based on the harmonic phase to be compensated, the fundamental voltage amplitude, and the harmonic voltage amplitude, an auxiliary converter pulse is generated, thereby suppressing the harmonics output by the nonlinear load of the auxiliary converter.

[0011] Preferably, the process of processing the three-phase output current to generate the phase difference between the fundamental and harmonic frequencies specifically includes:

[0012] The three-phase output current is converted from three-phase to two-phase to generate a two-phase alternating current;

[0013] Based on the orthogonality of trigonometric functions, the fundamental cosine factor and the inner product of the two-phase alternating current are discretized to generate the fundamental phase angle, and the harmonic cosine factor and the inner product of the two-phase alternating current are discretized to generate the harmonic phase angle.

[0014] The phase difference between the fundamental wave and the harmonics is generated based on the fundamental wave phase angle and the harmonic phase angle.

[0015] Preferably, the step of performing harmonic phase compensation according to preset rules and phase differences to generate the harmonic phase to be compensated specifically includes:

[0016] Based on the output filter's attribute parameters and preset load, generate the Bode plot of the output filter;

[0017] Based on the Bode plot of the output filter, the phase delay angle corresponding to the harmonic overlay is obtained;

[0018] The phase compensation angle of the initial harmonic compensation signal is obtained based on the phase delay angle corresponding to the harmonic frequency multiplication.

[0019] Based on the phase compensation angle and phase difference of the initial harmonic compensation signal, the harmonic phase to be compensated is generated.

[0020] More preferably, before obtaining the phase compensation angle of the initial harmonic compensation signal based on the phase delay angle corresponding to the harmonic doubling frequency, the method further includes:

[0021] Based on the three-phase output voltage and three-phase output current, the auxiliary converter is generated to calculate the output power.

[0022] The output power of the auxiliary converter is obtained by filtering the calculated output power.

[0023] Preferably, the processing of the three-phase output voltage to generate the fundamental voltage amplitude and harmonic voltage amplitude specifically includes:

[0024] The three-phase output voltage is subjected to dual synchronous rotating coordinate transformation, variable decoupling and digital filtering to generate the fundamental voltage amplitude;

[0025] The three-phase output voltage is subjected to dual synchronous rotating coordinate transformation and digital filtering to generate harmonic voltage amplitude.

[0026] More preferably, the step of performing dual-synchronous rotating coordinate transformation, variable decoupling, and digital filtering on the three-phase output voltage to generate the fundamental voltage amplitude specifically includes:

[0027] The three-phase output voltage is subjected to dual synchronous rotating coordinate transformation at a preset first angle, and then subjected to variable decoupling and digital filtering to generate the fundamental D-axis DC component and the fundamental Q-axis DC component.

[0028] The fundamental voltage amplitude is generated based on the fundamental DC component along the D-axis and the fundamental DC component along the Q-axis.

[0029] More preferably, the step of performing dual-synchronous rotating coordinate transformation and digital filtering on the three-phase output voltage to generate harmonic voltage amplitude specifically includes:

[0030] The three-phase output voltage is subjected to dual synchronous rotating coordinate transformation at a preset second angle, and then subjected to variable decoupling and digital filtering to generate harmonic D-axis DC component and harmonic Q-axis DC component.

[0031] The harmonic voltage amplitude is generated based on the DC component of the harmonic D-axis and the DC component of the harmonic Q-axis.

[0032] In a second aspect, the present invention provides an auxiliary converter nonlinear load output harmonic suppression device, comprising:

[0033] The acquisition module is used to acquire the three-phase output current and three-phase output voltage of the auxiliary converter;

[0034] The phase difference generation module is used to process the three-phase output current to generate the phase difference between the fundamental wave and the harmonic wave.

[0035] The harmonic phase generation module is used to perform harmonic phase compensation according to preset rules and phase differences, and generate the harmonic phase to be compensated.

[0036] The voltage amplitude generation module is used to process the three-phase output voltage to generate the fundamental voltage amplitude and harmonic voltage amplitude.

[0037] The auxiliary converter pulse generation module is used to generate auxiliary converter pulses based on the harmonic phase to be compensated, the fundamental voltage amplitude, and the harmonic voltage amplitude, thereby suppressing the harmonics output by the nonlinear load of the auxiliary converter.

[0038] In a third aspect, the present invention provides a computer server, comprising: a memory, a processor, and a transceiver;

[0039] The processor is used to couple with the memory, read and execute instructions in the memory to implement the auxiliary converter nonlinear load output harmonic suppression method as described in any of the first aspects above;

[0040] The transceiver is coupled to the processor, and the processor controls the transceiver to send and receive messages.

[0041] In a fourth aspect, the present invention provides a storage medium including a program or instructions that, when the program or instructions are run on a computer, implement the auxiliary converter nonlinear load output harmonic suppression method described in any of the first aspects above.

[0042] This invention provides a method for suppressing harmonics in the output of a nonlinear load in an auxiliary converter. Utilizing the orthogonality of trigonometric functions, the three-phase output current is processed to obtain the potential difference between the fundamental and harmonic signals. Then, the inverse phase of the harmonics is obtained based on the phase difference. The influence of the output filter inductor and capacitor on the phase delay of the inverse signal is also considered to obtain a complete harmonic phase to be compensated. The three-phase output voltage is processed to obtain the fundamental and harmonic voltage amplitudes, and finally, auxiliary converter pulses are generated to suppress the harmonics. Attached Figure Description

[0043] Figure 1 This is one of the flowcharts for the auxiliary converter nonlinear load output harmonic suppression method provided in the embodiments of the present invention;

[0044] Figure 2 The circuit topology diagram of the auxiliary converter provided in the embodiment of the present invention;

[0045] Figure 3 This is the second flowchart of the auxiliary converter nonlinear load output harmonic suppression method provided in the embodiments of the present invention;

[0046] Figure 4 The third flowchart of the auxiliary converter nonlinear load output harmonic suppression method provided in the embodiments of the present invention;

[0047] Figure 5 Bode plots of filters under different load conditions provided in embodiments of the present invention;

[0048] Figure 6 Flowchart four of the auxiliary converter nonlinear load output harmonic suppression method provided in the embodiments of the present invention;

[0049] Figure 7 This is a schematic diagram of dual synchronous rotation coordinate transformation provided in an embodiment of the present invention;

[0050] Figure 8 A schematic diagram of the decoupling and filtering process of the 5th and 7th harmonic components based on dual synchronous rotating coordinate transformation provided in an embodiment of the present invention;

[0051] Figure 9 The control principle diagram of the auxiliary converter nonlinear load output harmonic suppression method provided in the embodiment of the present invention;

[0052] Figure 10 Comparison charts showing application effects provided in embodiments of the present invention;

[0053] Figure 11 The application effect diagram of the auxiliary converter nonlinear load output harmonic suppression method provided in the embodiment of the present invention is shown.

[0054] Figure 12 A structural diagram of the auxiliary converter nonlinear load output harmonic suppression device module provided in an embodiment of the present invention. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0056] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0057] The present invention provides a method for suppressing harmonics at the output of a nonlinear load in an auxiliary converter. This method employs a closed-loop amplitude control and an open-loop angle control, ensuring that the control methods for harmonics and the fundamental frequency remain consistent. The control approach is simple and easy to apply in engineering.

[0058] Example 1

[0059] Figure 1 The flowchart below illustrates the method for suppressing harmonics at the output of a nonlinear load in an auxiliary converter, as provided in this embodiment of the invention. Figure 1 The technical solution of the present invention will be described with reference to specific embodiments.

[0060] The present invention provides a method for suppressing harmonics at the output of a nonlinear load in an auxiliary converter, which mainly includes the following steps:

[0061] Step 110: Obtain the three-phase output current and three-phase output voltage of the auxiliary converter;

[0062] Specifically, the three-phase output current of the auxiliary converter is obtained through a three-phase current sensor, and the three-phase output voltage of the auxiliary converter is obtained through a three-phase voltage sensor. Figure 2 The circuit topology of the auxiliary converter is shown below. Figure 2 As shown, the three-phase output current (load current) can be represented by I. sa I sb I sc This means that the three-phase output voltage can be represented by U. a U b U c express.

[0063] Step 120: Process the three-phase output current to generate the phase difference between the fundamental wave and the harmonics;

[0064] Due to the influence of nonlinear loads, such as inverter air conditioners and bridge rectifier loads, the three-phase output current often contains higher harmonics, including the 5th and 7th harmonics. The three-phase output current can be expressed mathematically as follows:

[0065]

[0066]

[0067]

[0068] Where A, B, and C are the amplitudes of the fundamental wave, the 5th harmonic, and the 7th harmonic, respectively; ω is the angular frequency of the fundamental wave; and t is the current time. and These are the phase angles of the fundamental wave, the 5th harmonic, and the 7th harmonic, respectively.

[0069] This step can be specifically achieved through methods such as... Figure 3 The sub-steps shown are implemented as follows:

[0070] Step 1201: Perform a three-phase to two-phase conversion on the three-phase output current to generate a two-phase alternating current;

[0071] Specifically, the two-phase alternating current is represented by I.α I β express.

[0072]

[0073]

[0074] Where A1, B1, and C1 are the amplitudes of the fundamental, 5th, and 7th harmonics after the three-phase to two-phase conversion, respectively. These are the phase angles of the fundamental, 5th, and 7th harmonics after the three-phase to two-phase conversion.

[0075] Step 1202: Based on the orthogonality of trigonometric functions, the fundamental cosine factor and the inner product of the two-phase alternating current are discretized to generate the fundamental phase angle. The harmonic cosine factor and the inner product of the two-phase alternating current are also discretized to generate the harmonic phase angle.

[0076] Specifically, firstly, the fundamental cosine factor is inner-producted with the two-phase alternating current, and the harmonic cosine factor is inner-producted with the two-phase alternating current.

[0077] The results of multiplying the fundamental cosine factor with the two-phase alternating current are as follows:

[0078]

[0079]

[0080] The results of multiplying the 5th harmonic cosine factor with the two-phase alternating current are as follows:

[0081]

[0082]

[0083] The results of multiplying the 7th harmonic cosine factor with the two-phase alternating current are as follows:

[0084]

[0085]

[0086] Where T is the period of the trigonometric function, which refers to the working period of the three-phase output voltage.

[0087] Secondly, the inner product result is discretized.

[0088] Since digital controllers can only process discrete signals, the inner product result needs to be discretized according to the discrete sampling period of the digital controller.

[0089] Specifically, the integral sequence of the left half of the result obtained in step 1202 is modified into a summation sequence. For example, the fundamental cosine factor and I... α Discretizing the inner product result yields:

[0090]

[0091] Where T is the operating period of the three-phase output voltage, and the discrete sampling period of the digital controller is assumed to be T. s N = T s / T, and take the integer part.

[0092] The calculation result of the digital controller is P. α_cosFnd .

[0093] Similarly, the fundamental cosine factor and I β The inner product result is discretized, and the result is denoted as P. β_cosFnd The 5th harmonic cosine factor is combined with I. α I β The inner product result is discretized, and the result is denoted as P. α_coshc5 P β_sinhc5 The 7th harmonic cosine factor is combined with I. α I β The inner product result is discretized, and the result is denoted as P. α_coshc7 P β_sinhc7 .

[0094] Finally, the fundamental phase angle and harmonic phase angle are calculated.

[0095] Among them, the fundamental phase angle 5th harmonic phase angle 7th harmonic phase angle

[0096] Step 1203: Generate the phase difference between the fundamental wave and the harmonics based on the fundamental wave phase angle and the harmonic phase angle.

[0097] Specifically, the phase difference between the fundamental frequency and the 5th harmonic is: The phase difference between the fundamental frequency and the 7th harmonic is The initial harmonic compensation angle (inverse phase) can be determined by the phase difference. The inverse phase is used... and It means, that is It should be noted that the current phase difference is the same as the voltage phase difference.

[0098] Step 130: Perform harmonic phase compensation according to preset rules and phase difference to generate the harmonic phase to be compensated;

[0099] Specifically, this step can be achieved through, for example... Figure 4 The sub-steps shown are implemented as follows:

[0100] Step 1301: Generate the Bode plot of the output filter based on the attribute parameters of the output filter and the preset load;

[0101] Specifically, considering the phase delay effect of the output filter inductor L1 and output filter capacitor C2 on the initial harmonic compensation angle (inverse phase), this application needs to plot the Bode plot of the output filter under different loads based on the output filter's attribute parameters, mainly hardware parameters, such as... Figure 5 As shown, Bode plots were obtained using no-load, half-load, and full-load conditions, indicating that this application employs an angle-open-loop control strategy. Combined with... Figure 2 and Figure 5 As shown, in this example, the following steps of the technical solution are explained using the output filter inductor L1 = 0.25mH, the output filter capacitor C2 = 550μF, and the auxiliary converter capacity 190kVA as an example.

[0102] Step 1302: Based on the Bode plot of the output filter, obtain the phase delay angle corresponding to the harmonic overlay.

[0103] Specifically, based on the Bode plot, the phase delay angles at the 5th harmonic (250Hz) and 7th harmonic (350Hz) frequencies can be obtained, such as... Figure 5 As shown, the 5th harmonic is located at the cutoff frequency of the output filter, with a phase change of -90°, while the phase change range of the 7th harmonic is -112° to -179°.

[0104] Step 1303: Obtain the phase compensation angle of the initial harmonic compensation signal based on the phase delay angle corresponding to the harmonic frequency multiplication.

[0105] Specifically, during phase compensation, the phase shift effect of the output filter on the phase compensation angle signal needs to be considered. Furthermore, if phase inverse compensation is performed based on the aforementioned phase difference, the phase compensation angle of the initial harmonic compensation signal needs to be determined based on the phase frequency characteristics of the auxiliary converter's output filter; this angle can be represented by δ. For example... Figure 5 As shown, under no-load conditions, the amplitude-frequency response is relatively flat in the low-frequency range, and a resonance peak appears at the filter resonant frequency. The phase-frequency response shows a 180° phase shift at the resonant frequency. Under half-load and full-load conditions, the linearity of the amplitude-frequency response and phase-frequency response curves is enhanced, and the phase-frequency response and amplitude-frequency response show linear changes at the resonant frequency.

[0106] Therefore, the phase needs to be linearized, and the phase change of the initial compensation signal for the 5th harmonic is δ. 5th_LC = -90°, the phase compensation angle can be compensated with a fixed value of -90°.

[0107] However, for the 7th harmonic, the phase compensation angle needs to be calculated according to the phase droop formula, as follows:

[0108] First, based on the three-phase output voltage and three-phase output current, the auxiliary converter is generated to calculate the output power.

[0109] The calculated output power is the actual power calculated based on the data collected by the sensor, denoted by P', where P' = U. a I sa +U b I sb +U c I sc

[0110] Secondly, the output power of the auxiliary converter is obtained by filtering the calculated output power of the auxiliary converter.

[0111] Since the calculated output power fluctuates significantly, it needs to be filtered to obtain a more accurate auxiliary converter output power, which is represented by P.

[0112] Finally, the phase compensation angle of the initial compensation signal of the 7th harmonic is calculated according to the phase droop formula.

[0113]

[0114] Step 1304: Generate the harmonic phase to be compensated based on the phase compensation angle and phase difference of the initial harmonic compensation signal.

[0115] Specifically, the 5th harmonic phase to be compensated is denoted by θ5. The 7th harmonic phase to be compensated is denoted by θ7. Only by obtaining the phase droop formula can the complete harmonic phase to be compensated be obtained.

[0116] Step 140: Process the three-phase output voltage to generate the fundamental voltage amplitude and harmonic voltage amplitude;

[0117] Specifically, this step can be done through, for example... Figure 6 The sub-steps shown are executed as follows:

[0118] Step 1401: Perform dual synchronous rotating coordinate transformation, variable decoupling and digital filtering on the three-phase output voltage to generate the fundamental voltage amplitude;

[0119] Specifically, such as Figure 7The diagram illustrates a dual-synchronous rotating coordinate transformation of the three-phase output voltage at a preset first angle. This preset first angle is denoted by ω't, where ω' is the angular velocity of the dual-synchronous rotating coordinate system. Essentially, the three-phase output voltage is transformed from the ABC three-phase coordinate system to a dq rectangular rotating two-phase coordinate system. The 5th harmonic rotation vector is in negative sequence, and the 7th harmonic is in positive sequence, yielding the rotation vectors of the fundamental U, the 5th harmonic U5, and the 7th harmonic U7, facilitating subsequent data processing.

[0120] Then, through variable decoupling and digital filtering, the fundamental d-axis DC component and the fundamental q-axis DC component are generated. The fundamental d-axis DC component is represented by U... dps The fundamental q-axis DC component is represented by U. qps The fundamental voltage amplitude is generated based on the fundamental DC components along the d-axis and q-axis. The fundamental voltage amplitude is denoted by U.

[0121] Step 1402: Perform dual synchronous rotating coordinate transformation and digital filtering on the three-phase output voltage to generate harmonic voltage amplitude.

[0122] Specifically, the three-phase output voltage undergoes a dual-synchronous rotating coordinate transformation at a preset second angle. This preset second angle includes -5ω't and 7ω't. Then, after variable decoupling and digital filtering, harmonic d-axis DC components and harmonic q-axis DC components are generated. Based on these harmonic d-axis and q-axis DC components, the harmonic voltage amplitude is generated.

[0123] For example, the three-phase output voltage is transformed by -5ω't and then processed to generate the 5th harmonic d-axis DC component U. 5dps and q-axis DC component U 5qps The three-phase output voltage is transformed by 7ω't, and then processed to generate the 7th harmonic d-axis DC component U. 7dps and q-axis DC component U 7qps Then, the amplitude of the 5th harmonic voltage was calculated. and the amplitude of the 7th harmonic voltage like Figure 8 This illustrates the process of component decoupling and filtering of the 5th and 7th harmonics based on dual-synchronous coordinate transformation. For example... Figure 8 As shown, the three-phase output voltage U a U b U c The components are transformed from three-phase to two-phase 3 / 2 to obtain U in two-phase stationary coordinates. α and U β Components. The transformation matrix is ​​as follows:

[0124]

[0125] C dq+ It is the forward Park transformation matrix, and its matrix expression is:

[0126]

[0127] C dq- It is the inverse Park transformation matrix, and its matrix expression is:

[0128]

[0129] Fundamental voltage U α and U β After Park transformation, the DC component U of the dq axis under positive sequence coordinate transformation can be obtained. d+ and U q+ and the DC component U of the dq axis under the reverse coordinate transformation d- and U q- .

[0130] The four DC components obtained above contain a secondary AC component and a coupling component, therefore decoupling is required. The decoupling result of the positive sequence component dq axis is U. dp and U qp The decoupling result of the negative-order component dq axis is U dn and U qn .

[0131] After passing through a low-pass filter (LPF, with a cutoff frequency typically set below 50Hz), the corresponding filter value U is obtained. dps and U qps U dns and U qns .

[0132] It should be noted that this process includes a phase-locked loop (PLL) used to obtain the angular velocity ω' of the dual-synchronous rotating coordinate system. (The last part, "U," appears to be an error and is left untranslated.) qp After being compared with the zero value, the result is sent to the PLL module to obtain ω', and then passed through the integrator to obtain the rotation angle θ'.

[0133] Then, the 5th harmonic component (dq-axis component) and the 7th harmonic component (dq-axis component) are obtained through dual synchronous coordinate transformation. These components are then passed through a low-pass filter (LPF), whose cutoff frequency is typically set below 20Hz, to obtain the DC component U. 5dps and U 5qps U 7dps and U 7qps Among them, C 5dp The transformation matrix is C 7dp The transformation matrix is

[0134] As can be seen, the decoupling operation is very simple, uses fewer filtering steps, and improves the dynamic response speed of the system.

[0135] Step 150: Based on the harmonic phase to be compensated, the fundamental voltage amplitude, and the harmonic voltage amplitude, generate auxiliary converter pulses to suppress the harmonics output by the nonlinear load of the auxiliary converter.

[0136] Specifically, such as Figure 9 As shown, the harmonic phase to be compensated, the fundamental voltage amplitude, and the harmonic voltage amplitude can be input into the controller to obtain the auxiliary converter pulse according to the seven-segment SVPWM.

[0137] Among them, U ref U is the amplitude of the three-phase fundamental voltage to be output, and U5, U7 are the amplitudes of the three-phase fundamental voltage, the 5th harmonic voltage, and the 7th harmonic voltage, respectively. These three values ​​are then compared with U... ref The value is compared with zero, and the comparison result is sent to the PID controller. The parameters of the three PID controllers are the same. By adjusting the proportional coefficient, the crossover frequency of the open-loop transfer function of the system is made to be 1 / 10 of the inverter switching frequency. By adjusting the integral coefficient, the corner frequency of the system is made to be twice the fundamental frequency. The derivative coefficient can be ignored.

[0138] Combination Figure 7 and Figure 9 As shown, the outputs of the three PID modules are multiplied by their corresponding triangular matrices to obtain the α-axis and β-axis components in the two-phase stationary coordinate system, and then summed. The summation result is then subjected to a 2 / 3 transformation, and the transformation matrix is ​​as follows:

[0139]

[0140] The three-phase AC variables are obtained and then fed into a traditional seven-segment SVPWM modulation module to obtain the control pulses for the auxiliary converter.

[0141] In summary, compared to the area equivalence method, this application eliminates the need to solve transcendental equations, thus reducing the computational burden on the controller and facilitating engineering applications. This significantly reduces controller application requirements and lowers usage costs. Each harmonic elimination controller requires only one PID calculation unit, avoiding the risk of control failure. The adoption of a closed-loop amplitude and open-loop angle control strategy ensures consistency between harmonic and fundamental wave control methods, resulting in a simple and easy-to-apply control approach.

[0142] Figure 10 The output voltage and current waveforms of the auxiliary converter without using the method of this patent are shown, with the load being a variable frequency air conditioner. It can be seen that the output voltage is severely distorted, with a harmonic distortion (THD) of 13.2%. Figure 11The images show the output voltage and current waveforms of the auxiliary converter using this patented method under the same operating conditions. The output voltage waveform quality is good, with a harmonic distortion (THD) of 3.7%. Therefore, it can be seen that this method can significantly improve the output voltage quality, providing high-quality electrical energy to the train.

[0143] This invention provides a method for suppressing harmonics in the output of a nonlinear load in an auxiliary converter. Utilizing the orthogonality of trigonometric functions, the three-phase output current is processed to obtain the potential difference between the fundamental and harmonic signals. Then, the inverse phase of the harmonics is obtained based on the phase difference. The influence of the output filter inductor and capacitor on the phase delay of the inverse signal is also considered to obtain a complete harmonic phase to be compensated. The three-phase output voltage is processed to obtain the fundamental and harmonic voltage amplitudes, and finally, auxiliary converter pulses are generated to suppress the harmonics.

[0144] Example 2

[0145] Embodiment 2 of the present invention provides an auxiliary converter nonlinear load output harmonic suppression device, comprising:

[0146] The acquisition module 10 is used to acquire the three-phase output current and three-phase output voltage of the auxiliary converter;

[0147] The phase difference generation module 11 is used to process the three-phase output current and generate the phase difference between the fundamental wave and the harmonic wave.

[0148] The harmonic phase generation module 12 is used to perform harmonic phase compensation according to preset rules and phase differences, and generate the harmonic phase to be compensated.

[0149] The voltage amplitude generation module 13 is used to process the three-phase output voltage and generate the fundamental voltage amplitude and harmonic voltage amplitude.

[0150] The auxiliary converter pulse generation module 14 is used to generate auxiliary converter pulses based on the harmonic phase to be compensated, the fundamental voltage amplitude, and the harmonic voltage amplitude, thereby suppressing the harmonics output by the nonlinear load of the auxiliary converter.

[0151] Example 3

[0152] Embodiment 3 of the present invention provides a computer server, including: a memory, a processor, and a transceiver;

[0153] The processor is used to couple with the memory, read and execute instructions in the memory to implement the auxiliary converter nonlinear load output harmonic suppression method described in any of the above embodiments.

[0154] The transceiver is coupled to the processor, and the processor controls the transceiver to send and receive messages.

[0155] Example 4

[0156] Embodiment 4 of the present invention provides a storage medium including a program or instructions, which, when run on a computer, implements the auxiliary converter nonlinear load output harmonic suppression method described in any of the embodiments above.

[0157] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0158] The steps of the methods or algorithms described in conjunction with the embodiments disclosed herein can be implemented in hardware, a software module executed by a processor, or a combination of both. The software module can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, removable disk, CD-ROM, or any other form of storage medium known in the art.

[0159] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for suppressing harmonics at the output of an auxiliary converter nonlinear load, characterized in that, include: Obtain the three-phase output current and three-phase output voltage of the auxiliary converter; The three-phase output current is processed to generate the phase difference between the fundamental wave and the harmonics; Harmonic phase compensation is performed according to preset rules and phase differences to generate the harmonic phase to be compensated; The three-phase output voltage is processed to generate the fundamental voltage amplitude and harmonic voltage amplitude; Based on the harmonic phase to be compensated, the fundamental voltage amplitude, and the harmonic voltage amplitude, an auxiliary converter pulse is generated, thereby suppressing the harmonics output by the nonlinear load of the auxiliary converter. The step of performing harmonic phase compensation according to preset rules and phase differences to generate the harmonic phase to be compensated specifically includes: Based on the output filter's attribute parameters and preset load, generate the Bode plot of the output filter; Based on the Bode plot of the output filter, the phase delay angle corresponding to the harmonic overlay is obtained; The phase compensation angle of the initial harmonic compensation signal is obtained based on the phase delay angle corresponding to the harmonic frequency multiplication. Based on the phase compensation angle and phase difference of the initial harmonic compensation signal, the harmonic phase to be compensated is generated.

2. The method for suppressing harmonics at the output of an auxiliary converter nonlinear load according to claim 1, characterized in that, The process of processing the three-phase output current to generate the phase difference between the fundamental and harmonic frequencies specifically includes: The three-phase output current is converted from three-phase to two-phase to generate a two-phase alternating current; Based on the orthogonality of trigonometric functions, the fundamental cosine factor and the inner product of the two-phase alternating current are discretized to generate the fundamental phase angle, and the harmonic cosine factor and the inner product of the two-phase alternating current are discretized to generate the harmonic phase angle. The phase difference between the fundamental wave and the harmonics is generated based on the fundamental wave phase angle and the harmonic phase angle.

3. The method for suppressing harmonics at the output of an auxiliary converter nonlinear load according to claim 1, characterized in that, Before obtaining the phase compensation angle of the initial harmonic compensation signal based on the phase delay angle corresponding to the harmonic frequency doubling, the method further includes: Based on the three-phase output voltage and three-phase output current, the auxiliary converter is generated to calculate the output power. The output power of the auxiliary converter is obtained by filtering the calculated output power.

4. The method for suppressing harmonics at the output of an auxiliary converter nonlinear load according to claim 1, characterized in that, The process of processing the three-phase output voltage to generate the fundamental voltage amplitude and harmonic voltage amplitude specifically includes: The three-phase output voltage is subjected to dual synchronous rotating coordinate transformation, variable decoupling and digital filtering to generate the fundamental voltage amplitude; The three-phase output voltage is subjected to dual synchronous rotating coordinate transformation and digital filtering to generate harmonic voltage amplitude.

5. The method for suppressing harmonics at the output of a nonlinear load in an auxiliary converter according to claim 4, characterized in that, The process of performing dual-synchronous rotating coordinate transformation, variable decoupling, and digital filtering on the three-phase output voltage to generate the fundamental voltage amplitude specifically includes: The three-phase output voltage is subjected to dual synchronous rotating coordinate transformation at a preset first angle, and then subjected to variable decoupling and digital filtering to generate the fundamental D-axis DC component and the fundamental Q-axis DC component. The fundamental voltage amplitude is generated based on the fundamental DC component along the D-axis and the fundamental DC component along the Q-axis.

6. The method for suppressing harmonics at the output of an auxiliary converter nonlinear load according to claim 4, characterized in that, The process of performing dual synchronous rotating coordinate transformation and digital filtering on the three-phase output voltage to generate harmonic voltage amplitude specifically includes: The three-phase output voltage is subjected to dual synchronous rotating coordinate transformation at a preset second angle, and then subjected to variable decoupling and digital filtering to generate harmonic D-axis DC component and harmonic Q-axis DC component. The harmonic voltage amplitude is generated based on the DC component of the harmonic D-axis and the DC component of the harmonic Q-axis.

7. A harmonic suppression device for the output of a nonlinear load in an auxiliary converter, characterized in that, include: The acquisition module is used to acquire the three-phase output current and three-phase output voltage of the auxiliary converter; The phase difference generation module is used to process the three-phase output current to generate the phase difference between the fundamental wave and the harmonic wave. The harmonic phase generation module is used to perform harmonic phase compensation according to preset rules and phase differences, and generate the harmonic phase to be compensated. The voltage amplitude generation module is used to process the three-phase output voltage to generate the fundamental voltage amplitude and harmonic voltage amplitude. The auxiliary converter pulse generation module is used to generate auxiliary converter pulses based on the harmonic phase to be compensated, the fundamental voltage amplitude, and the harmonic voltage amplitude, thereby suppressing the harmonics output by the nonlinear load of the auxiliary converter. Specifically, the harmonic phase generation module to be compensated is used for: Harmonic phase compensation is performed according to preset rules and phase differences to generate the harmonic phase to be compensated, specifically including: Based on the output filter's attribute parameters and preset load, generate the Bode plot of the output filter; Based on the Bode plot of the output filter, the phase delay angle corresponding to the harmonic overlay is obtained; The phase compensation angle of the initial harmonic compensation signal is obtained based on the phase delay angle corresponding to the harmonic frequency multiplication. Based on the phase compensation angle and phase difference of the initial harmonic compensation signal, the harmonic phase to be compensated is generated.

8. A computer server, characterized in that, include: Memory, processor, and transceiver; The processor is used to couple with the memory, read and execute instructions in the memory to implement the auxiliary converter nonlinear load output harmonic suppression method according to any one of claims 1 to 6; The transceiver is coupled to the processor, and the processor controls the transceiver to send and receive messages.

9. A storage medium, characterized in that, Includes a program or instructions that, when run on a computer, implement the auxiliary converter nonlinear load output harmonic suppression method as described in any one of claims 1 to 6.

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