An adaptive aerial power grid input filter capacitance simplification compensation method

Abstract

The application discloses a self-adaptive aviation power grid input filter capacitor simplification compensation method, which simplifies input filter capacitor current to be compensated, and uses a simplified triangular wave to approximate a cosine for compensation, so that the calculation amount is greatly simplified; and the method adaptively simplifies a triangular wave approximation compensation function with the change of an input frequency and an input voltage effective value, so that the calculation amount can be further simplified. The method fully considers the problem of small storage or weak calculation capacity of the current domestic digital controller, and has strong use value for the current aviation power source domestic substitution.

Description

TECHNICAL FIELD

[0001] The present application relates to a self-adaptive aerial power grid input filter capacitor simplification compensation method. TECHNICAL BACKGROUND

[0002] With the rapid development of modern aviation technology, there are more and more airborne electronic devices, so that the harmonic reactive and unbalanced load components have a great impact on the aircraft AC power grid, seriously affecting the power supply quality of the aerial power grid, reducing the performance and service life of the power generation equipment and power consumption equipment, and even endangering the safety of the aircraft power supply system. At present, the power factor correction (PFC) device has been widely used on the aircraft to handle the harmonic, reactive and unbalanced current problems of the aircraft power grid, so that the aircraft power supply or power consumption equipment meets the requirements of the relevant standards.

[0003] The critical conduction mode (hereinafter referred to as "CRM") totem pole PFC topology has a simple main circuit, small conduction loss and easy to realize soft switching, and becomes popular in high-efficiency high-power-density aviation power supply occasions. Figure 1 The totem pole PFC topology structure is shown, in the CRM totem pole PFC converter, the input filter capacitor C in Limit the propagation of switching noise of high-frequency switching tube to AC line. The definition of power factor (PF) is the ratio of average power to apparent power, that is,

[0004]

[0005] Where THD is the total harmonic distortion of input current, and the influence of THD on PF value can be ignored on the premise of meeting the THD requirement. The phase difference between the input line voltage (i.e. input voltage) and the input current fundamental component of the PFC circuit represented by

[0006] By Figure 1 And Figure 2 It can be seen that the input current I in Is equal to

[0007] I in = I L + I C (2)

[0008] Where I L Is the inductor current, and I C Is the current flowing through the input filter capacitor.

[0009] The input voltage is

[0010]

[0011] Where Urms is the effective value of the input voltage, f line is the frequency of the AC input voltage, and t is the time.

[0012] Generally speaking, in order to achieve power factor correction, the inductor current follows the input voltage

[0013]

[0014] Among them, P o is the output power and η is the converter efficiency.

[0015] The current on the input filter capacitor is

[0016]

[0017] Combining (1), (2), (3), (4), and (5) we get

[0018]

[0019] From the above formula, we can see that the PF value is related to the effective value of the input voltage U rms , AC input voltage frequency f line , input filter capacitor C in Inversely proportional to the output power P o In the wide frequency (360-800Hz) aviation power grid system, the influence of input filter capacitor becomes serious and cannot be ignored, resulting in a decrease in PF value. At 115V AC input effective value, the input filter capacitor C in The output power is 300W, and the frequency of the AC input voltage is f line At 800Hz, the PF value is 0.91, which does not meet the specification requirement (greater than 0.968). Therefore, it is necessary to compensate it to offset the influence of the input filter capacitor to meet the specification requirement.

[0020] The current main compensation schemes are based on formula (5), which calculates the input filter capacitor current I C , vector superposition -I on the basis of inductor current C The influence of the input filter capacitor can be offset. Formula (5) has cosine calculation, which will undoubtedly increase the amount of calculation, which is undoubtedly a challenge for low-performance and low-cost digital controllers. Therefore, some related literature adopts the method of looking up tables for compensation. Based on formula (5), the value of formula (5) at each time scale is calculated in advance, and a table is made and placed in the digital controller. The digital controller looks up the table to obtain a compensation value for a time scale. However, it can be seen from formula (5) that this compensation value is also related to the effective value of the input voltage U rms , AC input voltage frequency fline For wide frequency aviation power grid system, the frequency f of AC input voltage is line From 360 to 800 Hz, the effective value of voltage U rms Fluctuations within ±10% necessitate the creation of multiple tables, which undoubtedly places higher demands on the storage space of digital controllers. According to research, aviation PFC power modules that meet the universal input voltage range of 85-264V, a wide input frequency range of 360-800Hz, high efficiency, high power density, and high power factor are currently largely monopolized by US companies such as Vicor and SynQor. This is due to the relatively late start of domestic research in this field, resulting in immature technology, and the limited storage and computing power of current domestically produced digital controllers. Summary of the Invention

[0021] Existing technologies all require high-performance digital controllers to compensate for the effects of input filter capacitors. High-performance controllers are more expensive, and currently domestic digital controllers suffer from limited storage capacity and weak computing power. Therefore, this invention proposes a simplified digital control compensation solution. This simplified adaptive aviation power grid input filter capacitor compensation method significantly reduces computational complexity and is adaptable. This method offers significant potential for domestically replacing existing aviation power sources.

[0022] The present invention is achieved by adopting the following technical solutions:

[0023] An adaptive simplified compensation method for aviation power grid input filter capacitors is proposed, which simplifies the input filter capacitor current to be compensated and uses the simplified compensation capacitor current to offset the input capacitance.

[0024] The input filter capacitor current to be compensated is simplified as follows:

[0025] The current on the input filter capacitor is

[0026]

[0027] Therefore, the capacitor current that needs to be compensated is

[0028]

[0029] The Fourier series expansion of the triangle wave is

[0030]

[0031] Among them A max Indicates the amplitude of the triangle wave, ω=2πf line .

[0032] From (8) and (9), the fundamental wave in the Fourier series of the triangular wave and the expression of the capacitive current to be compensated are consistent in form. The fundamental wave in the Fourier series of the triangular wave can be approximated as the triangular wave, i.e.

[0033]

[0034] From (8) and (10),

[0035]

[0036] Substituting (11) into the triangular wave function we obtain:

[0037]

[0038] As can be seen from formula (12), using the triangular wave function instead of the cosine function can greatly simplify the calculation amount. In actual digital control implementation, all signals and compensation are discretized.

[0039] In the digital controller, the relevant signals are updated by executing the interrupt program each time. The time of one interrupt is denoted as T S The number of interrupts in one half cycle, i.e., the number of updates of compensation in one half cycle, is

[0040] Taking the positive half cycle as an example, the half-cycle triangular wave is divided into 2N parts, and the change of the triangular wave amplitude in each update is

[0041]

[0042] Therefore, the discretized triangular wave function expression is

[0043]

[0044] As can be seen from the comparison between (14) and (8), between 90 degrees and 180 degrees (N-2N) and between 270 degrees and 360 degrees (3N-4N) in each input voltage line frequency cycle, the discretized triangular wave deviates more from the ideal compensation cosine, resulting in a larger compensation error. Therefore, it needs to be optimized. The specific optimization implementation method is to replace n with n+1 in (14) between 90 degrees and 180 degrees (N-2N) and between 270 degrees and 360 degrees (3N-4N). Compared with the traditional discretized triangular wave compensation, the compensation error is greatly reduced. At the same time, in order to be simple, n can be reset to 0 from 2N during the switching process of each input voltage positive and negative half cycle.

[0045] The optimized positive half-cycle discretized triangular wave function expression is

[0046]

[0047] The optimized negative half cycle discretization triangular wave function expression is

[0048]

[0049] As can be seen from the formula (15), (16), the slope and intercept of the optimized discretization triangular wave function are related to the input voltage effective value U rms , and the frequency f line of the alternating input voltage. For the variable frequency aviation power grid system, the frequency f line of the alternating input voltage changes from 360 to 800 Hz, and the fluctuation of the voltage effective value U rms is ±10%, thus the slope and intercept of the triangular wave function need to be recalculated every time the aviation power grid frequency and the input voltage change, which increases the calculation time of the digital controller. Therefore, the present application is further optimized on this basis, and a final normalized adaptive discretization triangular wave compensation scheme is proposed, which greatly shortens the calculation time of the digital controller. The adaptive discretization triangular wave compensation scheme is described below through specific examples.

[0050] Let f line =k1f base

[0051] U rms =k2U base

[0052] Wherein, f base is the reference base of the input frequency, for the aviation power grid of 360-800 Hz, f base is set to any value in 360-800, and in the present example, f base is set to 400 Hz, k1 is the ratio of the input frequency to the reference base frequency at this time; U base is the reference base of the input voltage effective value, for the 115V aviation power grid, U base is set to 115V, and k2 is the ratio of the input voltage effective value to the reference base voltage effective value at this time; C in and T S are fixed values, which are obtained according to the circuit parameter selection and the execution time of the digital controller.

[0053] For the CRM totem column PFC topology, the designed output power is maximum 325W, and on the basis of testing related conduction radiation standards, the input filter capacitor C in is at least selected to be 2uF, and the digital controller is selected to be the ADP32F035 of the domestic Hunan Jinxin type, and the one-time interruption time is about T S =15·10-6 s

[0054] The initial conditions are brought into formula (15), (16),

[0055] The adaptive normalized positive half-cycle discretized triangular wave function expression is

[0056]

[0057] The adaptive normalized negative half-cycle discretized triangular wave function expression is

[0058]

[0059] The present application has the following advantages:

[0060] The present application uses a simplified triangular wave to approximate cosine compensation, greatly simplifying the calculation amount; the method of the present application adaptively simplifies the triangular wave approximation compensation function with the change of input frequency and input voltage, which can further simplify the calculation amount. The scheme of the present application greatly improves the PF value in the frequency conversion aviation power grid (360-800Hz) range, and the performance superiority is more obvious with the increase of input frequency. Moreover, the simplified triangular wave adaptive capacitance compensation of the present application greatly reduces the calculation time, and the compensation accuracy meets the index requirements. The method of the present application fully considers the problem of small storage or weak computing ability of the current domestic digital controller, and has strong use value for the current aviation power source localization replacement. BRIEF DESCRIPTION OF DRAWINGS

[0061] Figure 1 Totem pole PFC topology diagram;

[0062] Figure 2 Input voltage, input current, inductor current, input capacitor current phase diagram;

[0063] Figure 3 One cycle triangular wave form;

[0064] Figure 4 One cycle compensation key waveform;

[0065] Figure 5 Traditional discrete triangular wave approximation compensation schematic diagram;

[0066] Figure 6 Optimized discrete triangular wave approximation compensation schematic diagram;

[0067] Figure 7 CRM totem pole PFC adaptive wideband input simplified compensation digital control block diagram;

[0068] Figure 8 Program flowchart of one-time interruption of digital control;

[0069] Figure 9 Input 115Vac, 400Hz, filter capacitor 2uF, output 302W test waveform;

[0070] Figure 10 Input 115Vac, 800Hz, filter capacitor 2uF, output 302W test waveform;

[0071] Figure 11 The application scheme is compared with the scheme without using the application at different frequencies. DETAILED DESCRIPTION

[0072] The application discloses a self-adaptive aviation power grid input filter capacitor simplification compensation method.

[0073] The input capacitor compensation capacitor current is simplified, specifically as follows:

[0074] The current on the input filter capacitor is

[0075]

[0076] Therefore, the capacitor current that needs to be compensated is

[0077]

[0078] The Fourier series expansion of the triangular wave is

[0079]

[0080] Where A max represents the amplitude of the triangular wave, as shown in Figure 3 ω = 2πf line .

[0081] From (2) and (3), it is known that the fundamental wave in the Fourier series of the triangular wave is consistent with the expression form of the capacitor current to be compensated. The fundamental wave in the Fourier series of the triangular wave can be approximated as equal to the triangular wave, that is,

[0082]

[0083] By combining (2) and (4), it is obtained that

[0084]

[0085] (5) is brought into the triangular wave function , and it is obtained that

[0086]

[0087] It can be seen from formula (6) that using triangular wave function instead of cosine function can greatly simplify the calculation amount. In actual digital control implementation, all signals and compensation are discretized.

[0088] In the digital controller, the relevant signals are updated by executing the interrupt program every time, and the interrupt time is recorded as T S , the number of interrupts in a half cycle, that is, the number of updates of compensation in a half cycle is

[0089] Taking the positive half cycle as an example, the half cycle triangular wave is divided into 2N parts, and the triangular wave amplitude changes every time the update is

[0090]

[0091] Therefore, the discrete triangular wave function expression is

[0092]

[0093] Figure 5 It is shown that the traditional discrete triangular wave compensation diagram can be seen that between 90 degrees and 180 degrees of phase angle (N-2N), between 270 degrees and 360 degrees of phase angle (3N-4N), the discrete triangular wave deviates from the ideal compensation sine more, resulting in larger compensation error, so it needs to be optimized. The specific optimization implementation method is to replace the variable n of formula (8) with n+1 between 90 degrees and 180 degrees of phase angle (N-2N), between 270 degrees and 360 degrees of phase angle (3N-4N), and the compensation waveform Figure 6 It can be seen that compared with Figure 5 The traditional discrete triangular wave compensation, the compensation error is greatly reduced.

[0094] At the same time, in order to be simple, n can be reset to 0 from 2N during the positive and negative half cycle switching process of each input voltage. The optimized positive half cycle discrete triangular wave function expression is

[0095]

[0096] The optimized negative half cycle discrete triangular wave function expression is

[0097]

[0098] C in and T S are fixed values, which are obtained according to the circuit parameter selection and the execution time of the digital controller. It can be seen from formula (9), (10) that the slope and intercept of the optimized discrete triangular wave function are related to the effective value of the input voltage U rms , the frequency f lineAll are relevant, for variable frequency aviation power grid system, the frequency f of AC input voltage line From 360 to 800Hz, the fluctuation of voltage effective value U rms In ±10%, so each time the aviation power grid frequency and input voltage change need to recalculate the slope and intercept of the triangular wave function, which increases the calculation time of the digital controller, for this reason, the invention is based on the optimization, and finally puts forward the adaptive normalized discrete triangular wave compensation scheme, which greatly shortens the calculation time of the digital controller. The adaptive discrete triangular wave compensation scheme is described below through specific examples.

[0099] Let f line =k1f base_400 f base_400 =400Hz

[0100] U rms =k2U base_115 U base_115 =115V

[0101] For CRM totem column PFC topology, the designed output power is maximum 325W, in this test, on the basis of relevant conducted radiation standards, the input filter capacitor C in At least 2uF, the digital controller selects the domestic Hunan Jinxin type ADP32F035, with this digital controller, the first interrupt time is about T S =15·10 -6 s

[0102] The above initial conditions are brought into formulas (9), (10) to obtain the adaptive normalized positive half cycle discrete triangular wave function expression as

[0103]

[0104] The adaptive normalized negative half cycle discrete triangular wave function expression is

[0105]

[0106] Where k1 is the ratio of the input frequency to the reference reference frequency at this time, and k2 is the ratio of the input voltage effective value to the reference reference voltage effective value at this time.

[0107] Figure 7The figure shows a simplified compensation digital control block diagram for a specific CRM totem-pole PFC with adaptive wideband input. The inductor current zero-crossing signal obtained by the auxiliary winding ZCD circuit is compared with the internal comparator of the digital controller. The falling edge of the comparator output signal is captured as the signal to clear the ePWM module counter, i.e., the signal to turn on the switch. The eCAP module captures the rising edge of the power-frequency tube drive signal SR2 to obtain the input frequency value. The input voltage and bus voltage samples are sent to the ADC sampling module of the digital controller. The bus voltage sampled value is used to perform a closed-loop PI operation to obtain the on-time Ton_error required for power transmission. The input voltage RMS value obtained by input voltage sampling and the input frequency value obtained by the eCAP module are used to approximate the input filter capacitor compensation according to the adaptive triangular wave function to calculate the on-time T required for input filter capacitor current compensation. C _com.Ton_error and T C The final on-time Ton is obtained by adding _com, and Ton is assigned to the ePWM module of the digital controller to control the on-time of the main switch tube.

[0108] Figure 8 The figure is a flow chart of a one-time interrupt program of the adaptive wideband input simplified compensation digital control of the CRM totem pole PFC.

[0109] Figure 9 The waveform shown is a test waveform of the present invention with an input of 115Vac, a frequency of 400Hz, an input filter capacitor of 2uF, and an output of 302W. It can be seen that the input current can follow the input voltage very well, and the PF value is 0.992 at this time. Figure 10 The waveforms of the test are shown below: 115Vac input, 800Hz frequency, 2uF input filter capacitor, 302W output. It can be seen that the input current can follow the input voltage well. The PF value is 0.981. Figure 11 As can be seen, the proposed solution significantly improves PF within the variable-frequency aviation power grid (360-800Hz) range, with performance becoming even more pronounced as input frequency increases. Furthermore, the proposed solution's simplified triangular-wave adaptive input filter capacitor compensation significantly reduces calculation time, while ensuring accurate compensation that meets regulatory requirements. This makes it highly valuable for domestically replacing existing aviation power sources.

Claims

1. A method for adaptive aerial power grid input filter capacitance simplification compensation, characterized in that, The input filter capacitor current to be compensated is simplified, and the simplified compensation capacitor current is used to offset the input capacitor current; The simplification of the input filter capacitor current to be compensated is specifically: The input filter capacitor current to be compensated is （1）； wherein, is the current flowing through the input filter capacitor; is the input filter capacitor, is the frequency of the alternating input voltage, is the input voltage effective value, is time; The Fourier series expansion of the triangular wave is （2）； wherein denotes the triangle wave amplitude, ; The fundamental wave in the Fourier series expansion of the triangular wave is approximated to the triangular wave, i.e. （3）； By combining (1) and (3), we have （4）； Substitute (4) into the triangular wave function We get: （5）； In the digital controller, the time of each interruption is recorded by executing the interruption program to update the relevant signals The number of interruptions in a half cycle, i.e. the number of updates compensated in a half cycle, is ; Therefore, the discrete triangular wave function expression is （6）。 2. The method of claim 1, wherein, The discrete triangular wave function expression is optimized, and the optimization is specifically: In each input voltage positive and negative half cycle switching process, n is reset from 2N to 0, and the discrete triangular wave function in one half cycle is divided into two parts, the optimized positive half cycle discrete triangular wave function expression is （7）； The optimized negative half cycle discrete triangular wave function expression is （8）。 3. The method of claim 2, wherein, The optimized discrete triangular wave function expression is normalized, and the normalization is specifically: Let ; wherein, is a reference for the input frequency, for an aeronautical electrical network of 360-800 Hz, is set to 360-800, is the ratio between the input frequency and the reference frequency at that time; is a reference for the input voltage effective value, for an aeronautical electrical network of 115 V, is set to 115 V, is the ratio between the input voltage effective value and the reference voltage effective value at that time; The reference values of the discrete triangular wave slope and intercept are respectively represented as （9）； （10）； The normalized positive half cycle discrete triangular wave function expression is （11）； The normalized negative half cycle discrete triangular wave function expression is （12）； wherein, and are fixed values, obtained according to the circuit parameters selection and the digital controller execution time.

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