A Calculation Method for Energy Storage Capacitors in a High-Voltage DC Power Supply Architecture

Abstract

The present invention relates to a method for calculating energy storage capacitors in a high-voltage direct current (HVDC) power supply architecture. The method is based on a high-voltage DC bus power supply system architecture. The system includes a platform DC device, a power distribution device, a primary power supply, an energy storage capacitor, an array DC / DC power supply, and a pulse load. The primary power supply can suppress power fluctuations. The primary power supply boosts the high-voltage DC power provided by the power supply platform to DC power, the transmission cable transmits the DC power to the array, and the array DC / DC power supply converts the DC power into low-voltage DC power to power the array pulse load. The energy storage capacitor calculation method includes: determining basic parameters of the power supply system, calculating the energy storage capacitor capacity based on the change in the high-voltage DC bus voltage; calculating the energy storage capacitor capacity based on power fluctuation index requirements; calculating the energy storage capacitor capacity based on the dynamic characteristics of the primary power supply; and taking the maximum value of the three as the final result of the energy storage capacitor. The present invention can ensure that the power supply system has good dynamic performance and the power changes are more stable.

Description

Technical Field

[0001] The present invention relates to the field of electrical engineering, and in particular to a method for calculating energy storage capacitance of a high-voltage direct current power supply architecture. Background Art

[0002] Modern phased array radars are becoming increasingly versatile, capable of simultaneously performing multiple functions within a single radar, including detection, reconnaissance, jamming, communication, and tracking. This has led to a gradual increase in system radiated power and operating pulse widths, with peak and average system power reaching megawatts. The power supply capacity of some platforms is now comparable to the radar system's power requirements. Phased array radars are characterized by their array operating in pulsed mode. The radar's pulse load transmits pulse power to the power supply side through the power supply system, leading to increasingly prominent stability issues for both the radar system and the platform's power supply system.

[0003] To accommodate the development of all-electric systems on future ships, a high-voltage DC bus power supply architecture is more conducive to system reliability design, significantly reducing the weight of transmission cables and significantly improving power supply system reliability. Therefore, some shipborne platforms use a high-voltage DC bus power supply architecture to provide power to shipborne radars. Radars are critical high-power electronic devices on ships, and distributed architectures are the development trend of radar power systems. The integrated design of power supplies and components allows for peak power design. Since the power consumed by the radar array load transmitting components accounts for the majority of the total power consumption of the radar system, these pulsed loads cause severe power fluctuations during operation, causing the input power on the power supply side to fluctuate between no-load and full-load for long periods of time. This exacerbates power fluctuations on the radar power supply side, severely impacting the stability of the power supply platform and the radar power system. Therefore, power fluctuation suppression measures are necessary to improve the reliability and stability of the entire shipboard power supply system.

[0004] In summary, in order to adapt to the development of future ships and modern electronic equipment, it is necessary to ensure the system stability between the power supply platform and the radar system. Taking power fluctuation suppression measures for radar pulse loads is a relatively effective solution. The key technology for implementing this solution is to configure reasonable energy storage capacitors to meet the needs of power fluctuation suppression and system stability. Therefore, the present invention proposes a method for calculating the energy storage capacitor of a high-voltage DC bus, provides a theoretical calculation method for the capacity of the energy storage capacitor, and lays a theoretical foundation for constructing a high-voltage DC bus system architecture and providing highly reliable and stable electric energy for radar equipment.

[0005] This system architecture was first proposed by the China Electronics Technology Group Corporation 14th Research Institute in the design of phased array radar systems. Currently, there are no very effective technical solutions and theoretical results for this problem at home and abroad. Reference [1] discloses a method of using a bidirectional converter to compensate for the excessive bus current fluctuation caused by the pulse load characteristics, solving the compatibility problem between the pulse load and the power supply. However, there are local peaks in the input current waveform, which is also a limitation of the parallel scheme. In addition, the power of the bidirectional converter required to be configured in the parallel scheme is more than twice the average power of the power supply system. Considering both cost and volume, the parallel scheme is difficult to apply in actual engineering, especially for megawatt-level power supply systems. In addition, the reference only provides experimental and simulation results without providing a theoretical calculation method for energy storage capacitors.

[0006] [1] Zhu Zeyu, Yang Ping. Design and implementation of high-power pulse load power supply with fast dynamic response. New Technology of Electrical Engineering and Energy. 2019, 38(5): 13-20. Summary of the Invention

[0007] To solve the existing technical problems, the present invention provides a method for calculating energy storage capacitors in a high-voltage direct current power supply architecture.

[0008] The specific contents of the present invention are as follows: This technical solution adopts a high-voltage DC bus power supply system architecture to provide stable and reliable power for the radar array pulse load. The power supply system architecture consists of platform DC power, power distribution, primary power supply (with power fluctuation suppression function), energy storage capacitors, array DC / DC (also known as secondary power supply) and array load. The power supply platform provides 500V high-voltage DC power, the primary power supply boosts the 500V DC power to 780V DC power, the transmission cable transmits the 780V DC power to the array, and the array DC / DC converts the 780V DC power to 32V low-voltage DC power to power the pulse load.

[0009] To meet the power supply requirements of the array's pulse load, appropriate capacitors are configured on the pulse load input side to ensure that the pulse load input voltage drop meets the requirements of the pulse transmitter. Under pulse load conditions in a certain operating mode, the DC / DC input power exhibits alternating peak and no-load conditions. Without a primary power supply and energy storage capacitors, this pulsed power directly acts on the power supply platform's generator set. For the power supply system of a megawatt-class radar, power fluctuations of several megawatts can occur, seriously impacting the stability of the power supply platform's generator set.

[0010] The specific calculation steps of the technical solution of the present invention are as follows:

[0011] (1) Determine the basic parameters of the power supply system

[0012] The array DC / DC power supply supplies power to the array pulse load. The pulse load has a duty cycle of T and a duty pulse width of t.L,wd , so the duty cycle satisfies:

[0013]

[0014] Pulse load at a certain pulse width time t L,wd The working current is the peak current I pk , the output voltage of DC / DC is u DC,out , then the peak power P of the pulse load within the pulse width time pk for:

[0015] P pk =u DC,out I pk (2)

[0016] According to the principle of energy conservation, within a pulse load cycle, the working pulse width of DC / DC is t DC,wd satisfy:

[0017] u DC,out I DC,max t DC,wd =u DC,out I pk t L,wd (3)

[0018]

[0019] In the above formula, I DC,max is the maximum output current of the DC / DC, so

[0020] The working duty cycle of DC / DC is:

[0021]

[0022] Assume that the efficiency of DC / DC is η DC , then the input power of DC / DC is:

[0023]

[0024] Among them, the maximum output power of DC / DC is:

[0025] P DC,max =u DC,out I DC,max (7)

[0026] Then the average DC / DC input power is:

[0027]

[0028] As can be seen from formula (6), the input power of DC / DC is periodic. The primary power supply in this technical solution has the function of suppressing power fluctuations. The energy storage capacitor is connected in parallel after the primary power supply to jointly provide the pulse power required by DC / DC.

[0029] The primary power supply adopts dual closed-loop control of power outer loop and current inner loop. The power control loop filters the feedback voltage to obtain the current command signal, which is the input current command signal of the primary power supply. The calculation method of the filter gain coefficient K1 is:

[0030]

[0031] Among them, P out,N is the rated output power of the primary power supply; u in,N is the rated input voltage; η bt is the efficiency of the primary power supply; u ref is the voltage of the primary power supply when it is unloaded; u out,N It is the rated output voltage of the primary power supply under rated load.

[0032] The energy storage capacitor on the high-voltage DC bus is subject to three constraints. First, the change in the high-voltage DC bus voltage Δu must be guaranteed under pulse load conditions. out Satisfy the constraints; second, the input power fluctuation index (P APR Peak-to-peak power to average power ratio) meets the requirements; third, it must be ensured that the primary power supply has good dynamic characteristics.

[0033] (2) Calculate the energy storage capacitor capacity based on the change in high-voltage DC bus voltage

[0034] In order to meet the high-voltage DC bus voltage variation constraint, within one cycle, the primary power supply provides average power, and during the non-pulse width time of the back-end DC / DC, the energy storage capacitor voltage rises from the minimum value to the maximum value, that is:

[0035]

[0036] By deduction, the relationship between the energy storage capacitor capacity and the DC / DC duty cycle is as follows:

[0037]

[0038] In order to ensure that the bus voltage variation can meet the requirements under various duty cycle conditions, the calculation formula of the energy storage capacitor is:

[0039]

[0040] Where Δu out,maxis the maximum allowable variation of the high-voltage DC bus voltage.

[0041] (3) Calculate the energy storage capacitor capacity according to the power fluctuation index requirements

[0042] Fluctuation index P of primary power input power APR The calculation formula is:

[0043]

[0044] Among them, P max 、P max 、P avg They are the minimum, maximum and average power values respectively.

[0045] The filter transfer function of the primary power control loop is as follows:

[0046]

[0047] Where ω1 is the filter corner frequency, which satisfies the following equation:

[0048]

[0049] Among them, ω L,min Is the minimum operating frequency of the pulse load.

[0050] Under the condition of minimum frequency pulse load, the output voltage of the primary power supply is approximately a triangle wave. Through Fourier analysis, the fundamental amplitude of the current command output by the filter can be obtained as follows:

[0051]

[0052] According to power balance, the average current of primary power input is:

[0053]

[0054] According to equations (16) and (17), the power fluctuation suppression index can be calculated:

[0055]

[0056] The power fluctuation index constraints are as follows:

[0057] P APR ≤P APR,max (19)

[0058] Considering formula (15), the energy storage capacitor capacity C determined by the above constraints is bus,2 for:

[0059]

[0060] (4) Considering the dynamic characteristics of the primary power supply, calculate the capacity of the energy storage capacitor

[0061] According to formula (15), the crossover frequency ω of the primary power control loop is c,u Can be set to

[0062]

[0063] According to the cross-over frequency, the energy storage capacitor capacity can be calculated as:

[0064]

[0065] Among them, η bt is the efficiency of the primary power supply.

[0066] (5) Taking the above three calculation results into consideration, the maximum value of the three is taken as the final result of the energy storage capacitor.

[0067] C bus =max{C bus,1 ,C bus,2 ,C bus,3} (twenty three)

[0068] The above calculation method constitutes the entire calculation process of the high-voltage DC bus energy storage capacitor.

[0069] (6) Establish a simulation model for the power supply system and test the characteristics of the power supply system.

[0070] The present invention solves the theoretical calculation problem of the energy storage capacitor of the power supply system under pulse load conditions, and mainly brings the following benefits: through theoretical calculation results, it is ensured that the change value of the bus voltage meets the index requirements under various working mode pulse loads, which is of positive significance to improving the efficiency and reliability of the array DC / DC power supply; it is ensured that the power fluctuation index of the power supply system meets the requirements under various working mode pulse loads, which is of great significance to improving the fuel economy, reliability and stability of the power supply platform; the energy storage capacitor calculation method proposed in the present invention can ensure that the power supply system has good dynamic performance, the power change is more stable, the interference to the power supply platform is reduced, and the stability of the power supply system is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] The specific embodiments of the present invention will be further explained below with reference to the accompanying drawings.

[0072] Figure 1 Schematic diagram of the high-voltage DC bus power supply architecture;

[0073] Figure 2 This is a flow chart for calculating the energy storage capacitor of the present invention;

[0074] Figure 3Schematic diagram for establishing a simulation model for a pulse load power supply system;

[0075] Figure 4 It is the high-voltage DC bus voltage curve output by the primary power supply;

[0076] Figure 5 It is the output power curve of the power supply platform, and also the fluctuation curve of the primary power input power. DETAILED DESCRIPTION

[0077] Combine Figure 1 and Figure 2 , taking the power supply link of an active sub-array of phased array radar as an example, the following Figure 1 The high-voltage DC bus power supply system architecture shown in the figure has an input voltage of 500V DC, a no-load output voltage of 780V DC for the primary power supply, and an output voltage of 32V DC for the array DC / DC. The calculation process is given below:

[0078] (1) Determine the basic parameters of the power supply system

[0079] The peak power of the pulse load is 10kW, and the capacitance on the array is 0.47F, ensuring that the voltage drop during pulse load operation meets the requirement of ≤10%. The pulse load operating mode is: period T = 30ms, pulse width 6ms, and duty cycle 20%.

[0080] The rated output voltage of the array DC / DC power supply is u DC,out =28V, maximum output current I DC,max =120A, efficiency is 0.95, and the DC / DC duty cycle is calculated according to formula (5):

[0081]

[0082] DC / DC efficiency η DC =0.95, the maximum output power of the DC / DC is:

[0083] P DC,max =u DC,out I DC,max =32×120=3840 (25)

[0084] The primary power supply adopts double closed loop control of power outer loop and current inner loop, and the rated output power P out,N =3kW, efficiency = 0.96, no-load output voltage is u ref =780V, output voltage u under rated load out,N =740V, the filter gain coefficient is calculated according to formula (9):

[0085]

[0086] The following three algorithms are used to calculate the energy storage capacitor:

[0087] (2) Calculate the energy storage capacitor capacity based on the change in high-voltage DC bus voltage

[0088] According to the input requirements of the array DC / DC power supply, the maximum allowable change of the high-voltage DC bus voltage Δu out,max =30V. According to formula (12), the capacitance is calculated as:

[0089]

[0090] (3) Calculate the energy storage capacitor capacity according to the power fluctuation index requirements

[0091] Minimum operating frequency of pulse load ω L,min =2*pi / 0.003=209.4, then the filter's corner frequency is ω1=83.78.

[0092] Fluctuation index P of primary power input power APR,max =0.2, according to formula (20), the energy storage capacitance determined by this index constraint is:

[0093]

[0094] (4) Considering the dynamic characteristics of the primary power supply, calculate the capacity of the energy storage capacitor

[0095] According to formula (22), the energy storage capacitor capacity is calculated as:

[0096]

[0097] (5) Taking the above three calculation results into consideration, the maximum value of the three is taken as the final result of the energy storage capacitor.

[0098] C bus =max{0.0014,0.0022,0.0027}=0.0027F (30)

[0099] (6) Establish a simulation model for the power supply system, such as Figure 3 As shown, the voltage on the high-voltage DC bus energy storage capacitor and the output power of the power supply platform are obtained as follows: Figure 4 and Figure 5 As shown,

[0100] Depend on Figure 4 It can be seen that the minimum value of the energy storage capacitor voltage is 745V, the maximum value is 760V, and the voltage variation is 15V, which meets the constraint condition of less than 30V.

[0101] Depend on Figure 5It can be seen that during the pulse load working period, the maximum output power is 2.28kW, the minimum is 1.94kW, and the average power is 2.11kW. The power fluctuation index P is calculated. APR =0.1611, which satisfies the constraint of being less than 0.2.

[0102] Therefore, the effectiveness of the method proposed in this invention is verified through modeling and simulation.

[0103] The present invention solves the problem of calculating energy storage capacitors in the power supply system of shipborne platform radars. In the design of high-power pulse load power supply systems, the energy storage capacitor capacity is a key factor affecting the stability of the power supply system. In engineering applications, it is necessary to minimize the energy storage capacitor capacity while meeting power supply performance, reducing system costs and volume. The energy storage capacitor calculation method proposed in this invention provides a theoretical basis for the rational configuration of energy storage capacitors. At the same time, it can achieve the following purposes:

[0104] 1) Improve the stability and reliability of the radar power supply system under pulse load conditions and reduce the interference of pulse loads on the shipborne platform power station;

[0105] 2) Reduce the demand for energy storage capacitor capacity and accurately configure the energy storage capacitor capacity;

[0106] 3) Under pulse load conditions, the generator set can output average power smoothly, improving the fuel efficiency of the platform generator set.

[0107] In summary, the present invention provides a scientific and effective calculation method for the energy storage capacitor in the high-voltage DC bus radar power system architecture, and provides a theoretical basis for the design of megawatt-level pulse load power supply systems. The present invention can be applied to other power supply systems with pulse loads, which can improve the power supply quality and enhance the stability of the entire power supply system. With the rapid development of new energy, the adoption of this solution can reduce the impact of pulse loads on microgrids and improve the stability of microgrids. Therefore, this method has a wide range of applications.

[0108] In the above description, many specific details are set forth in order to fully understand the present invention. However, the above description is only a preferred embodiment of the present invention. The present invention can be implemented in many other ways different from those described herein, so the present invention is not limited to the specific implementation disclosed above. At the same time, any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A method for calculating energy storage capacitance in a high-voltage direct current power supply architecture, characterized by: Based on the high-voltage DC bus power supply system architecture, the system includes a platform DC device, a power distribution device, a primary power supply, energy storage capacitors, an array DC / DC power supply, and an array pulse load. The primary power supply can suppress power fluctuations. The primary power supply boosts the high-voltage DC power provided by the power supply platform to DC power, transmits the DC power to the array through a transmission cable, and the array DC / DC power supply converts the DC power into low-voltage DC power to power the array pulse load. The calculation method of energy storage capacitor includes the following steps: Step 1: Determine the basic parameters of the power supply system; Step 2: Calculate the energy storage capacitor capacity based on the change in the high-voltage DC bus voltage; Step 3: Calculate the energy storage capacitor capacity according to the power fluctuation index requirements; Step 4: Consider the dynamic characteristics of the primary power supply and calculate the capacity of the energy storage capacitor; Step 5: Comprehensively consider the calculation results of steps 2 to 4 and take the maximum value of the three as the final result of the energy storage capacitor; In step 1, the basic parameters of the power supply system are calculated as follows: The array DC / DC power supply supplies power to the array pulse load. The duty cycle of the pulse load is T, and the working pulse width is , duty cycle for: Pulse load at a certain pulse width time Working within the range, the working current at this time is the peak current , the output voltage of the array DC / DC power supply is , the peak power of the pulse load within the pulse width time for: ， In one pulse load cycle, the working pulse width of the array DC / DC power supply satisfy: in, is the maximum output current of the array DC / DC power supply, The operating duty cycle of the array DC / DC power supply is: The efficiency of the array DC / DC power supply is , then the input power of the array DC / DC power supply is: Among them, the maximum output power of the array DC / DC power supply is: The average input power of the array DC / DC power supply is: The primary power supply adopts a dual closed-loop control of the power outer loop and the current inner loop, in which the power control loop filters the feedback voltage to obtain the current command signal, which is the input current command signal of the primary power supply. The filter gain coefficient The calculation method is: in, is the rated output power of the primary power supply; is the rated input voltage; is the efficiency of the primary power supply; It is the voltage of the primary power supply when it is unloaded; It is the rated output voltage of the primary power supply under rated load; In step 2, the energy storage capacitor capacity is calculated based on the change in the high-voltage DC bus voltage. The calculation formula is: in, is the maximum allowable variation of the high-voltage DC bus voltage; In step 3, calculate the energy storage capacitor capacity according to the power fluctuation index requirements The calculation method is: The power fluctuation index constraint conditions are: Energy storage capacitor capacity for ； In step 4, the method for calculating the energy storage capacitor capacity is as follows: Crossover frequency of the primary power control loop Set to: ， in, is the minimum operating frequency of the pulse load, Energy storage capacitor capacity for: 。 2. The method for calculating energy storage capacitance of a high-voltage direct current power supply architecture according to claim 1, wherein: The method also includes step six, establishing a simulation model for the power supply system and testing the characteristics of the power supply system.

3. The method for calculating energy storage capacitance of a high-voltage direct current power supply architecture according to claim 1, wherein: During the operation of the pulse load, the array DC / DC power supply provides the maximum output current, and the remaining current required by the pulse load is provided by the array energy storage capacitor.

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