CN-115800704-B - DC active filter device based on square wave modulation

CN115800704BCN 115800704 BCN115800704 BCN 115800704BCN-115800704-B

Abstract

The invention provides a direct current active filter device based on square wave modulation. The device comprises at least one independent direct current active filtering unit, wherein the direct current active filtering units are connected in parallel with two ends of a direct current bus, the direct current active filtering unit comprises a measuring circuit for measuring ripple current of the direct current bus, a control circuit for obtaining each frequency component of the ripple current through calculation and then obtaining a switching signal through square wave modulation, the frequency of the switching signal is equal to the target frequency of the ripple current to be compensated, and a driving circuit sends the switching signal to the main power loop, a switching device in the main power loop acts to generate compensation current, and the ripple current of the target frequency component of the direct current bus is compensated. The problem that ripple suppression effect is poor when the switching frequency of the high-power direct-current active filter is low is solved. The DC active filter is applied to the occasion of MW level power under lower switching frequency, and the DC bus ripple suppression requirement of long-time work of a high-power supply is met.

Inventors

ZHANG MING
ZHANG HONGQI
MA SHAOXIANG
Zhu Bangyou
XU RUIYANG
LI ZHIHENG
GUO GUI
YU KEXUN

Assignees

华中科技大学

Dates

Publication Date: 20260505
Application Date: 20221031

Claims (6)

1. The direct current active filtering device based on square wave modulation is characterized by being connected to a direct current bus and used for compensating ripple current of the direct current bus; the direct current active filtering device comprises at least one independent direct current active filtering unit, wherein the direct current active filtering unit comprises a main power loop, a measuring circuit, a control circuit and a driving circuit, and the direct current active filtering units are all connected in parallel with two ends of the direct current bus; The measuring circuit is used for measuring ripple current of the direct current bus; the control circuit obtains each frequency component of the ripple current through calculation, and then obtains a switching signal through square wave modulation, wherein the frequency of the switching signal is equal to the target frequency of the ripple current to be compensated; The driving circuit sends the switching signal to the main power loop, a switching device in the main power loop acts to generate a compensation current for compensating the ripple current of the target frequency component of the direct current bus, the compensation current is triangular, the phase of the compensation current is the same as the phase of the sine ripple current of the target frequency component by setting the target electrical parameters of the inductor and the capacitor, and the amplitude I tri of the compensation current and the amplitude I Crf of the sine ripple current of the target frequency component satisfy the relation: 。
2. The direct current active filtering device according to claim 1, wherein the number of the direct current active filtering units is equal to the number of frequency components of the ripple current; Each of the dc active filtering units is configured to compensate for a ripple current of one of the frequency components.
3. The direct current active filter device according to claim 2, wherein the main power loop is composed of a power half-bridge, an inductor and a capacitor, two ends of the capacitor are respectively connected to the upper end and the lower end of the power half-bridge, a first end of the inductor is connected with the positive electrode of a direct current bus, a second end of the inductor is connected with the middle point of the power half-bridge, and the lower end of the power half-bridge is connected with the negative electrode of the direct current bus.
4. A dc active arrangement as claimed in claim 3, wherein the power half-bridge is composed of two switching devices which are complementarily turned on or off; when the sine wave phase of the target frequency component of the ripple current is in To the point of When the power half-bridge is in the middle, an upper switching device of the power half-bridge is turned off, a lower switching device of the power half-bridge is turned on, and the output voltage of the power half-bridge is 0; when the sine wave phase of the target frequency component of the ripple current is in To the point of And when the voltage is in the same range, the upper switching device of the power half-bridge is turned on, and the lower switching device of the power half-bridge is turned off, so that the output voltage of the power half-bridge is twice the voltage of the direct current bus.
5. The direct current active filter apparatus according to claim 1, wherein the inductance L f has a calculation formula: Wherein, T rf is the period of the ripple current with frequency f, I Crf is the amplitude of the ripple current, and V dc is the voltage of the DC bus; The calculation formula of the capacitance C f is as follows: Wherein V Cf is the capacitor voltage and C rf % is the voltage ripple ratio of the capacitor.
6. The direct current active filtering device according to claim 1, wherein the ripple current is a difference between an output current i rec of a rectifier and an input current i inv of an inverter on the direct current bus; the rectifier output current i rec is obtained by measuring the current of the filter inductance of the direct current bus, and the input current i inv+ of the inverter is obtained by the following formula: V a ,V b ,V c is a three-phase output voltage of the inverter connected to the dc bus, and i a ,i b ,i c is a three-phase output current of the inverter connected to the dc bus.

Description

DC active filter device based on square wave modulation Technical Field The invention belongs to the technical field of direct current active filtering, and particularly relates to a direct current active filtering device based on square wave modulation. Background The accelerator power supply (AGPS) of the Neutral Beam Injector (NBI) model machine of the Chinese fusion engineering test pile (CFETR) is a high-voltage power supply with rated voltage of-200 kV/25A, and in order to reduce the divergence degree of neutral beams and improve the heating efficiency of an NBI system, the output voltage ripple of the AGPS needs to be strictly limited. The AGPS dc bus voltage ripple is transferred to the output voltage through the circuit structure, so that the output voltage ripple is increased. Therefore, a low ripple dc bus voltage is essential. In order to reduce ripple on the dc bus voltage of AGPS, a large number of capacitors are used in parallel on the dc bus. These capacitors occupy a large portion of the volume of the power supply, making the power supply more cumbersome. In addition, the capacitor is one of the most likely to fail components in the whole power supply, and the use of a large amount of capacitors reduces the reliability of the power supply. The DC active filter is a novel ripple suppression device, can compensate ripple current in a power supply through switching on and switching off of a switching device, further reduces ripple on DC bus voltage, and has the advantages of small size, good ripple suppression effect and the like. However, in the case of high power supplies, the switching device is limited by the power capacity and the operating frequency cannot be very high (typically tens to tens of kilohertz). The ripple suppression effect of the dc active filter will be significantly deteriorated due to the reduction of the switching frequency, which limits its application in high power applications. In addition, sinusoidal mains voltages are currently introduced in most of the control strategies or improved circuit schemes for dc active filters, which are not suitable for all high-power supplies with dc bus structures. Disclosure of Invention Aiming at the defects and improvement demands of the prior art, the invention provides a direct current active filter device based on square wave modulation, which aims to solve the problem that the ripple suppression effect is poor when the switching frequency of a high-power direct current active filter is low. The key electrical parameters are determined, so that the direct current active filter can be applied to the use occasion of MW-level power under the power capacity of the existing switching device, the direct current bus ripple suppression requirement of a high-power supply for long-time working is greatly met, and the direct current active filter has good market application prospect and application value. In order to achieve the above object, the present invention provides a direct current active filtering device based on square wave modulation, wherein the direct current active filtering device is connected to a direct current bus for compensating ripple current of the direct current bus; The direct current active filtering device comprises a direct current active filter, a measuring circuit, a control circuit and a driving circuit, wherein the direct current active filter comprises at least one independent direct current active filtering unit which is connected in parallel with two ends of the direct current bus; The measuring circuit is used for measuring ripple current of the direct current bus; the control circuit obtains each frequency component of the ripple current through calculation, and then obtains a switching signal through square wave modulation, wherein the frequency of the switching signal is equal to the target frequency of the ripple current to be compensated; The driving circuit sends the switching signal to a direct current active filter, and a switching device in the direct current active filter unit acts to generate compensation current for compensating ripple current of a target frequency component of the direct current bus. Optionally, the number of the direct current active filtering units is equal to the number of the frequency components of the ripple current; Each of the dc active filtering units is configured to compensate for a ripple current of one of the frequency components. Optionally, the direct current active filtering unit is composed of a power half-bridge, an inductor and a capacitor, wherein two ends of the capacitor are respectively connected with the upper end and the lower end of the power half-bridge, a first end of the inductor is connected with the positive electrode of the direct current bus, a second end of the inductor is connected with the middle point of the power half-bridge, and the lower end of the power half-bridge is connected with the negative electrode of the direct current bus. Opt