Method for Eliminating Reverse Voltage of Pulse Capacitor Load in Cascade High Voltage Power Supply

Abstract

The present invention provides a method for eliminating the reverse pressure of a pulse capacitor load of a cascade type high voltage power supply, which uses a pulse capacitor with reverse pressure as a virtual stage of the cascade type high voltage power supply, and performs sequential series operation with existing battery groups of various levels, so as to recover the reverse pressure energy of the pulse capacitor to form a positive pressure. When the pulse capacitor has reverse pressure, the thyristor is turned on, and a discharge channel is formed through the bypass diode, thyristor, and loop current limiting inductor of the battery group, so that the reverse pressure on the pulse capacitor can be quickly released through this channel, and while reducing the reverse pressure of the pulse capacitor, the loop will also generate a positive loop current and a positive load voltage. The control system of the power supply detects the size of the loop current and the pulse capacitor voltage in real time, and on this basis, the battery group is connected to the system according to the calculated timing of the battery groups of various levels, and the pulse capacitor is charged again.

Description

Technical Field

[0001] The invention belongs to the field of electricity, and in particular relates to a method for eliminating reverse voltage of a pulse capacitor load of a cascade type high voltage power supply. Background Art

[0002] DC high-voltage charging, as a common charging method for pulse capacitors, started in the last century. The earliest DC high-voltage power supply was to convert AC mains or three-phase electricity into AC high voltage electricity by industrial frequency high-voltage transformer, and then rectified and filtered to obtain DC high voltage electricity. With the practical development of pulse power technology, the power demand of pulse capacitors for high-voltage charging power supplies has reached megawatts. At the same time, the demand for mobility has also put forward higher requirements for the power density index of high-voltage charging power supplies. The high-voltage power supply based on battery cascade has the characteristics of high energy storage density, high power density and good mobility. It is one of the effective engineering implementation solutions for megawatt-level and lightweight high-voltage charging power supplies. However, during field operations, due to various reasons, pulse capacitors will generate hundreds or even thousands of volts of reverse voltage after discharging subsequent loads in a certain working topology. This reverse voltage will have an adverse effect on the system's re-frequency operation status, the energy utilization efficiency of pulse capacitors, and system safety. Therefore, studying how to quickly and reasonably eliminate the reverse voltage on the pulse capacitor is of great significance to the stability of the system and the rapidity of the next charging.

[0003] For the reverse pressure generated by the pulse capacitor after operation, a parallel discharge resistor is often used to release it, but this method takes too long and is not applicable to situations where the capacitor needs to be charged and discharged multiple times in a short period of time. The article "Release Method of Reverse Charging Voltage of Energy Storage Capacitor in Pulse Power Supply" conducts a theoretical analysis of the discharge process of the capacitor energy storage pulse power supply with the commonly used discharge main switch placed in the pulse capacitor branch, and discusses various factors affecting the reverse charging voltage of the pulse capacitor. On this basis, a method for reducing the reverse charging of the pulse capacitor and a way to release the reverse pressure of the pulse capacitor are proposed, that is, a circuit structure in which the discharge main switch is placed in the load branch is used to provide a circuit for the release of the reverse charging voltage of the energy storage capacitor. Although this method can eliminate the reverse pressure of the pulse capacitor, it is only for a specific application scenario, and changes the structure of the commonly used discharge circuit in this application scenario, reducing the discharge efficiency of the pulse capacitor to the load, increasing the loss of the diode and thyristor in the subsequent load, and shortening the device life. Summary of the invention

[0004] The purpose of the present invention is to propose a method for eliminating the reverse pressure of a pulse capacitor load of a cascaded high-voltage power supply. In some specific discharge circuits, after the pulse capacitor is discharged, the pulse capacitor itself will generate a certain reverse pressure, which will have an adverse effect on the system. The method utilizes the charging channel of the cascaded high-voltage power supply to charge the pulse capacitor. Without adding auxiliary design and devices, the reverse pressure can be quickly eliminated by controlling the turn-on time of devices such as thyristors. In addition, while eliminating the reverse pressure of the pulse capacitor, the reverse pressure is also utilized, thereby shortening the charging time and making it easier to realize multiple charge and discharge operations of the pulse capacitor in a short time, greatly improving the operating capacity under heavy-frequency conditions.

[0005] The technical solution adopted by the present invention is: a method for eliminating the reverse pressure of a pulse capacitor load of a cascaded high-voltage power supply, wherein the cascaded high-voltage power supply comprises: a control system, a battery pack cascade module, a thyristor, and a loop current limiting inductor, and its load is a pulse capacitor; the timing of connecting the battery packs at each level in the cascaded high-voltage power supply to the loop is obtained by calculation, and the control system connects the battery packs step by step according to the obtained timing to complete the charging of the pulse capacitor; the method for eliminating the reverse pressure of the pulse capacitor utilizes the charging channel of the cascaded high-voltage power supply to charge the pulse capacitor, and before connecting the battery packs at each level to charge the pulse capacitor, the thyristor is triggered by the control system, so that the pulse capacitor with reverse pressure is charged by the bypass diode, thyristor, and loop current limiting inductor in the battery pack cascade module, thereby quickly completing the release of the reverse pressure. ; The above working process is consistent with the working process of charging the pulse capacitor by connecting the battery groups at each level to the loop. The pulse capacitor with reverse pressure can be regarded as a virtual stage in the cascade high-voltage power supply connected in series with the battery groups at each level, and completes the charging process of the pulse capacitor together with the battery groups at each level; during the working process, the loop current and the pulse capacitor voltage are detected in real time. Due to the effect of the thyristor, there is no oscillation process between the loop current and the pulse capacitor voltage. When the loop current is detected to be 0, the pulse capacitor voltage reaches the maximum value. On this basis, the battery groups at each level are connected in turn according to the calculated new timing to complete the charging of the pulse capacitor; due to the existence of the virtual stage, the pulse capacitor already has a positive initial value when the battery groups at each level are connected, and the reverse pressure energy is completely recovered while eliminating the reverse pressure of the pulse capacitor.

[0006] Beneficial effects:

[0007] The present invention uses a charging channel of a cascaded high-voltage power supply to charge a pulse capacitor without adding any auxiliary design and devices and without changing the discharge structure of the pulse capacitor to the subsequent load. By controlling the opening time of the thyristor and the battery pack cascade module switch tube, the pulse capacitor with reverse pressure is used as a virtual stage in series with the battery pack to quickly eliminate the reverse pressure of the pulse capacitor. In this way, the reverse pressure of the pulse capacitor can be quickly released and the charging speed can be improved to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a schematic diagram of the structure of the cascade type high voltage power supply system on which the present invention is based;

[0009] Figure 2 A circuit topology diagram of a specific embodiment of the present invention;

[0010] Figure 3 The waveforms of capacitor voltage and loop current during the voltage release process of the pulse capacitor with reverse pressure in the present invention;

[0011] Figure 4 The invention eliminates the reverse pressure of the pulse capacitor and the loop current and capacitor voltage waveform during its charging process. DETAILED DESCRIPTION

[0012] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0013] The structure of the cascade type high voltage power supply system in the present invention is as follows: Figure 1As shown, it includes 5 parts: control system 1, battery pack cascade module 2, thyristor 3, loop current limiting inductor 4 and pulse capacitor 5, wherein the pulse capacitor 5 is the load part of the cascade type high voltage power supply; the high voltage output end of the battery pack cascade module 2 is connected to the thyristor 3, the other end of the thyristor 3 is connected to the loop current limiting inductor 4, the other end of the loop current limiting inductor 4 is connected to the high voltage pole of the pulse capacitor 5, and the low voltage pole of the pulse capacitor 5 is connected to the low voltage end of the battery pack cascade module 2. The control system 1 mainly completes four functions, one is to output the control signal of the battery pack cascade module 2, this signal is connected to the control switch driving end in the battery pack cascade module 2, and controls the time when each level of battery pack is connected; the second is to output the opening signal to the thyristor 3, this signal is connected to the gate level of the thyristor 3; the third is to monitor the voltage at both ends of the pulse capacitor 5 in real time through the high voltage divider, and the high voltage divider is connected to both ends of the pulse capacitor 5; the fourth is to detect the loop current through the current transformer, and the current transformer is set in the charging circuit. The battery pack cascade module 2 is composed of a battery pack connected in series with an IGBT and then connected in parallel with a diode. The timing of the battery pack accessing the loop is obtained by calculation, and the control system 1 connects the battery pack step by step according to the obtained timing to complete the charging of the pulse capacitor 5.

[0014] The method for eliminating the reverse pressure of the pulse capacitor 5 uses a cascaded high-voltage power supply to provide a charging channel for the pulse capacitor 5. Before connecting to each level of the battery pack to charge the pulse capacitor 5, the thyristor 3 is triggered by the control system 1, so that the pulse capacitor 5 with reverse pressure passes through the bypass diode in the battery pack cascade module 2, and the thyristor 3 and loop current limiting inductor 4 in the cascaded high-voltage power supply system to charge the pulse capacitor 5, thereby quickly completing the release of the reverse pressure.

[0015] For the single charge and discharge of the pulse capacitor 5, first, the timing of connecting the battery packs at each level is calculated according to the initial values ​​of the pulse capacitor 5 voltage and the loop current being 0, and the battery packs are connected step by step according to the obtained timing to complete the charging of the pulse capacitor 5. Then, the pulse capacitor 5 discharges the subsequent load. After completing a series of work, the pulse capacitor 5 itself will generate a reverse pressure. At this time, the control system 1 monitors the value of the reverse pressure, and turns on the thyristor 3, so that the pulse capacitor 5 forms a reverse pressure release channel through the bypass diode, thyristor 3, and loop current limiting inductor 4 in the battery pack cascade module 2, and discharges quickly. Due to the action of the thyristor 3, the loop current and the voltage across the pulse capacitor 5 will not oscillate. When the detected loop current is 0, the release channel is disconnected. At this time, there will be a certain positive pressure across the pulse capacitor 5, which will be released through the discharge resistor to complete a single charge and discharge operation.

[0016] In the case of multiple charging and discharging of the pulse capacitor 5 in a short period of time, the first charging process is consistent with the single charging process. After the first charging and discharging is completed, the reverse pressure of the pulse capacitor 5 is detected, and the thyristor 3 is opened in advance by the control system 1 before the next charging to release the reverse pressure. Since the working process at this time is consistent with the influence on the loop current and the voltage of the pulse capacitor 5 when the battery pack is connected step by step, it can be used as a virtual stage to work with the battery packs at each level. Since the pulse capacitor 5 has a forward voltage when the current drops to zero, it is necessary to connect the battery packs at each level to the system step by step according to the detected voltage of the pulse capacitor 5 according to the new battery pack connection sequence. When the pulse capacitor 5 is charged to the set value, all switches are closed to complete the second charging. The third, fourth and other charging and discharging processes are similar. At the same time, it should be noted that since the reverse pressure of the pulse capacitor 5 has been eliminated at a certain moment before the current drops to 0, the connection time of the battery pack can be appropriately advanced when the connection of the first-level battery pack does not exceed the system's limiting current, and the new battery connection sequence is obtained by detecting the loop current and capacitor voltage values ​​to complete the rapid charging of the pulse capacitor 5.

[0017] In this way, the reverse pressure of the pulse capacitor 5 can be quickly released and the charging speed can be improved to a certain extent. This working process is consistent with the working process of charging the pulse capacitor 5 by connecting the battery groups at various levels to the loop. Therefore, the pulse capacitor 5 with reverse pressure can be regarded as a virtual stage in the cascade power supply connected in series with the battery groups at various levels, and the charging process of the pulse capacitor 5 is completed together with the battery groups at various levels. During the working process, the loop current and the voltage of the pulse capacitor 5 are detected in real time. Due to the action of the thyristor 3, there is no oscillation process between the loop current and the voltage of the pulse capacitor 5. When the loop current is detected to be 0, the voltage of the pulse capacitor 5 reaches the maximum value. On this basis, the battery groups at various levels are connected in turn according to the corresponding timing obtained by calculation to complete the charging of the pulse capacitor 5. Due to the existence of the virtual stage, the pulse capacitor will have a positive initial value when the battery group starts to be connected to the system. While eliminating the reverse pressure of the pulse capacitor 5, the reverse pressure is also utilized, which speeds up the charging speed, shortens the charging time, and completely recovers the reverse pressure energy, thereby improving the energy utilization rate.

[0018] Below Figure 2 The circuit topology shown further illustrates the reverse voltage elimination method of the pulse capacitor 5 . Figure 2In the figure, the battery voltage is 400V, the current limiting inductor is 60mH, the loop resistance is 200mΩ, and the pulse capacitor is 1.3F. The corresponding battery pack access timing is obtained by calculation according to the given data. The control system 1 controls the battery pack to turn on the IGBT access battery pack step by step according to the obtained timing and triggers the thyristor 3 to charge the pulse capacitor 5. After the voltage of the pulse capacitor 5 reaches the set value, all switches are closed to complete a charging, and then the pulse capacitor 5 discharges the subsequent load. Assume that after completing one charge and discharge, the pulse capacitor 5 generates a reverse voltage of 300V. If only one charge and discharge is performed, the control system 1 will directly open the thyristor 3 again after the charge and discharge is completed, so that the pulse capacitor 5, the bypass diode in the battery pack cascade module 2, the thyristor 3, and the loop current limiting inductor 4 form a reverse pressure release channel to complete the release of the reverse pressure. In this process, the loop current will first increase and then decrease to 0. The reverse pressure of the pulse capacitor 5 gradually decreases to 0 and then generates a certain positive pressure. At the same time, due to the action of the thyristor 3, there is no oscillation process between the loop current and the voltage across the pulse capacitor 5. The current waveform 1 and the capacitor voltage waveform 2 during the reverse pressure release process are as follows: Figure 3 When the current is detected to be 0, the discharge resistor is turned on to completely release the remaining voltage. If multiple charge and discharge operations are performed, after completing the first charge and discharge operation of the pulse capacitor 5, before turning on the IGBT in the battery pack cascade module 2 to charge the pulse capacitor 5 for the second time, the thyristor 3 is turned on by the control system 1 to release the reverse voltage of the pulse capacitor 5, as shown in FIG. Figure 4 As shown in stage 1, the collector collects the loop current and the voltage of the pulse capacitor 5 in real time. When the loop current drops to 0, the timing of the new battery pack accessing the system is obtained according to the collected current and voltage values, and the IGBT of the battery pack cascade module 2 is turned on in sequence through the control system 1 according to the new timing, and the battery pack is connected in series step by step to complete the charging, as shown in FIG. Figure 4 As shown in stage 2, the battery pack cascade module can be connected in advance according to actual conditions. After the last discharge operation is completed, the battery pack is no longer connected to charge the pulse capacitor 5. It is only necessary to open the thyristor 3 to complete the release of the reverse voltage, and then the remaining voltage is completely released through the discharge resistor. In the above-mentioned specific embodiment, the method for eliminating the reverse pressure of the pulse capacitor load of the cascade type high-voltage power supply realizes the rapid elimination of the reverse pressure of the pulse capacitor without changing the charging structure and the discharging structure. It is simple to operate and has fast release. It is feasible and practical in situations where the capacitor needs to be charged and discharged multiple times in a short period of time, that is, under heavy frequency conditions.

[0019] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for eliminating reverse voltage of a pulse capacitor load of a cascade type high voltage power supply, the cascade type high voltage power supply comprising: Control system, battery pack cascade module, thyristor, loop current limiting inductor, and its load is pulse capacitor; The timing of connecting the battery groups of each level of the cascaded high-voltage power supply to the circuit is obtained by calculation, and the control system connects the battery groups step by step according to the obtained timing to complete the charging of the pulse capacitor; The method for eliminating reverse voltage of the pulse capacitor is characterized in that the charging channel of the pulse capacitor is charged by using a cascaded high-voltage power supply, and the triggering of the thyristor is controlled by a control system before connecting the battery packs at various levels to charge the pulse capacitor, so that the pulse capacitor with reverse voltage is charged by the bypass diode, thyristor and loop current limiting inductor in the battery pack cascade module, thereby quickly completing the release of reverse voltage; The above working process is consistent with the working process of charging the pulse capacitor by connecting the battery groups at each level to the loop. The pulse capacitor with reverse pressure can be regarded as a virtual stage in the cascade high-voltage power supply connected in series with the battery groups at each level, and completes the charging of the pulse capacitor together with the battery groups at each level; during the working process, the loop current and the pulse capacitor voltage are detected in real time. Due to the action of the thyristor, there is no oscillation process in the loop current and the pulse capacitor voltage. When the loop current is detected to be 0, the pulse capacitor voltage reaches the maximum value. On this basis, the battery groups at each level are connected in turn according to the corresponding calculated timing to complete the charging of the pulse capacitor; due to the existence of the virtual stage, the pulse capacitor already has a positive initial value when the battery group is connected, and the reverse pressure energy is completely recovered while eliminating the reverse pressure of the pulse capacitor.

Images