阅读说明：本技术 一种开关电容型模块化高降压比直流电源及其控制方法 (Switched capacitor type modular high-voltage-reduction-ratio direct-current power supply and control method thereof ) 是由 李楚杉 李武华 任晟道 严辉强 祝琳 盛景 何湘宁 于 2021-08-13 设计创作，主要内容包括：本发明公开了一种开关电容型模块化高降压比直流电源及其控制方法,该电源包括上模块化级联电路组串,下模块化级联电路组串,负载和输入源；其中,上、下模块化级联电路组串分别包含i个上子模块电路和j个下子模块电路,所有子模块电路均为输入与输出电容串联的不隔离三端口开关电容谐振型电路,所述电源通过模块化级联组成高压直流输入、低压直流输出的高降压比直流电源,模块间的组合方式包括：上模块组串级联、下模块组串级联以及上、下模块组串混合级联。本发明可根据电压和功率等级要求进行灵活拓展,无需电压或电流检测装置,成本低,拓扑简单,易于控制,灵活性高,适用于中压或高压直流输入场合下小功率电源应用。(The invention discloses a switched capacitor type modular high-voltage-reduction-ratio direct-current power supply and a control method thereof, wherein the power supply comprises an upper modular cascaded circuit group string, a lower modular cascaded circuit group string, a load and an input source; wherein, the modular cascade circuit group cluster of upper and lower contains i and goes up sub module circuit and j sub module circuit down respectively, and all sub module circuit are the not three-port switch capacitor resonance type circuit of keeping apart that input and output capacitance are established ties, the power is through the modular cascade component high voltage direct current input, the high step-down ratio DC power supply of low pressure DC output, the integrated mode between the module includes: the upper module set is cascaded in series, the lower module set is cascaded in series, and the upper module set and the lower module set are cascaded in series and in a mixed mode. The invention can be flexibly expanded according to the requirements of voltage and power grades, does not need a voltage or current detection device, has low cost, simple topology, easy control and high flexibility, and is suitable for low-power supply application in medium-voltage or high-voltage direct-current input occasions.)

1. A switched capacitor type modular high voltage step-down ratio DC power supply, comprising:

the circuit comprises a load, an input source, an upper modular cascaded circuit group string consisting of i upper sub-module circuits and/or a lower modular cascaded circuit group string consisting of j lower sub-module circuits;

the upper sub-module circuit comprises an upper layer main capacitor, a lower layer main capacitor, an upper switch tube, a lower switch tube, an upper diode, a lower diode, a resonant inductor, an upper layer resonant capacitor, a lower layer resonant capacitor, an auxiliary transformer and three ports; the first port a, the positive electrode of an upper-layer main capacitor and the drain electrode of an upper switch tube are connected in common, the second port b, the negative electrode of the upper-layer main capacitor, the positive electrode of a lower-layer main capacitor, the source electrode of a lower switch tube, one end of a primary winding of an auxiliary transformer and the cathode of an upper diode are connected in common, the third port c, the negative electrode of the lower-layer main capacitor and the anode of a lower diode are connected in common, the source electrode of the upper switch tube, the drain electrode of the lower switch tube and the positive electrode of an upper-layer resonant capacitor are connected in common, one end of the upper-layer resonant capacitor and one end of a resonant inductor are connected in common with the other end of the primary winding of the auxiliary transformer, the anode of the upper diode, the cathode of the lower diode and the negative electrode of the lower-layer resonant capacitor are connected in common, and the other end of the resonant inductor is connected with the positive electrode of the lower-layer resonant capacitor;

the lower sub-module circuit comprises an upper-layer main capacitor, a lower-layer main capacitor, an upper switching tube, a lower switching tube, an upper diode, a lower diode, a resonant inductor, an upper-layer resonant capacitor, a lower-layer resonant capacitor and three output ports; the auxiliary transformer comprises a first port a, an upper-layer main capacitor anode and an upper diode cathode which are connected in common, a second port b, an upper-layer main capacitor cathode, a lower-layer main capacitor anode, a lower diode anode, one end of an auxiliary transformer primary winding and an upper switch tube drain electrode are connected in common, a third port c, a lower-layer main capacitor cathode and a lower switch tube source electrode are connected in common, an upper diode anode, a lower diode cathode and an upper-layer resonant capacitor anode are connected in common, an upper switch tube source electrode, a lower switch tube drain electrode and a lower-layer resonant capacitor cathode are connected in common, an upper-layer resonant capacitor cathode is connected with one end of a resonant inductor, and the other end of the auxiliary transformer primary winding, the other end of the resonant inductor and a lower-layer resonant capacitor anode are connected in common;

the upper modular cascade circuit group string comprises three upper ports, wherein the first upper port is connected with the port a of the first upper sub-module circuit, the second upper port is connected with the port c of the ith upper sub-module circuit, and the third upper port is connected with the port b of the ith upper sub-module circuit; the circuit connection mode of i upper submodules in the string is as follows: a second port b of the kth-1 upper sub-module circuit is connected with a first port a of the kth upper sub-module circuit, a third port c of the kth-1 upper sub-module circuit is connected with a second port b of the kth upper sub-module circuit, wherein k is more than or equal to 2 and less than or equal to i;

the lower modular cascaded circuit group string comprises three lower ports, a first lower port is connected with a port a of a first lower sub-module circuit, a second lower port is connected with a port b of the first lower sub-module circuit, and a third lower port is connected with a port c of a jth lower sub-module circuit; the circuit connection mode of j lower submodules in the string is as follows: the second port b of the kth-1 lower sub-module circuit is connected with the first port a of the kth lower sub-module circuit, the third port c of the kth-1 lower sub-module circuit is connected with the second port b of the kth lower sub-module circuit, and k is more than or equal to 2 and less than or equal to j;

when i is not equal to 0 and j is not equal to 0, the modular cascaded circuit group string is connected with an input source and a load in a mode that a first upper port of an upper modular cascaded circuit group string is connected with an input source anode, a third lower port of a lower modular cascaded circuit group string is connected with an input source cathode, a third upper port of the upper modular cascaded circuit group string and a first lower port of the lower modular cascaded circuit group string are connected with a load anode in a common mode, and a second upper port of the upper modular cascaded circuit group string and a second lower port of the lower modular cascaded circuit group string are connected with a load cathode in a common mode;

when i is more than or equal to 2 and j is equal to 0, the modular cascaded circuit group string is connected with the input source and the load in a mode that a first upper port of the upper modular cascaded circuit group string is connected with the anode of the input source, a third upper port of the upper modular cascaded circuit group string is connected with the anode of the load, and a second upper port of the upper modular cascaded circuit group string and the cathode of the load are connected with the cathode of the input source;

and when i is 0 and j is not more than 2, the modular cascaded circuit group string is connected with the input source and the load in a mode that a first lower port of the lower modular cascaded circuit group string, a load anode and an input source anode are connected in common, a second lower port of the lower modular cascaded circuit group string is connected with a load cathode, and a third lower port of the lower modular cascaded circuit group string is connected with an input source cathode.

2. The switched capacitor modular high voltage to low ratio dc power supply of claim 1, wherein said power supply has no central controller and further comprises a separate control module within each of the upper and lower sub-module circuits for controlling the switching tubes to be turned on or off.

3. The switched capacitor type modular high buck ratio dc power supply of claim 1, wherein each of the upper and lower sub-module circuits is adapted to provide power to the control module within the sub-module circuit via an auxiliary transformer.

4. The switched capacitor modular high buck ratio DC power supply of claim 1, wherein i + j ≧ 3.

5. The switched capacitor modular high buck ratio dc power supply of claim 4, wherein i ═ j and i ≧ 2, j ≧ 2.

6. The switched capacitor type modular high voltage-reduction ratio direct current power supply as claimed in claim 1, wherein the upper and lower switching transistors are fully-controlled power semiconductor devices.

7. A method for controlling a switched-off capacitor type modular high-voltage-reduction-ratio direct-current power supply as claimed in claim 2,

the control module in each of the upper sub-module circuit and the lower sub-module circuit outputs two complementary PWM signals with the duty ratio of 50 percent, the two PWM signals are respectively used as control signals of an upper switch tube and a lower switch tube in the sub-module circuit to lead the upper switch tube and the lower switch tube in the upper sub-module circuit and the lower sub-module circuit to be alternately conducted,

for the upper submodule, when the driving signal of the upper switch tube is 1, the driving signal of the lower switch tube is 0, the upper switch tube is conducted, the lower switch tube is turned off, the upper main capacitor transmits energy to the upper resonant capacitor, the lower resonant capacitor and the auxiliary transformer, when the driving signal of the upper switch tube is 0, the lower switch tube is driven by 1, the upper switch tube is turned off, the lower switch tube is conducted, the upper resonant capacitor and the lower resonant capacitor transmit energy to the lower main capacitor, and the upper resonant capacitor transmits energy to the auxiliary transformer,

for the lower submodule, when the driving signal of the upper switch tube is 0, the driving signal of the lower switch tube is 1, the upper switch tube is turned off, the lower switch tube is turned on, the lower main capacitor transmits energy to the upper resonant capacitor, the lower resonant capacitor and the auxiliary transformer, when the driving signal of the upper switch tube is 1, the driving signal of the lower switch tube is 0, the upper switch tube is turned on, the lower switch tube is turned off, the upper resonant capacitor and the lower resonant capacitor transmit energy to the upper main capacitor, and the lower resonant capacitor transmits energy to the auxiliary transformer.

8. The off-capacitor modular high buck ratio dc power supply control method of claim 7, wherein the control module does not sample a capacitor voltage or an inductor current in the upper and lower sub-module circuits.

Technical Field

The invention relates to the technical field of power electronics, in particular to a switched capacitor type modular high-voltage-reduction-ratio direct-current power supply and a control method thereof.

Background

For the occasion of directly obtaining auxiliary power supply from the medium-voltage direct-current bus, how to make the auxiliary power supply in the medium-voltage direct-current system realize high voltage reduction ratio work and high voltage isolation in a simple, compact and low-cost mode is a difficult problem in the medium-voltage direct-current system.

The voltage class of the existing commercial power semiconductor device is limited, the highest voltage class is only 6.5kV, and the commercial power semiconductor device cannot be directly used in a medium-voltage direct-current system, so that a power electronic converter directly connected with a medium-voltage direct-current side must use a semiconductor device series connection technology or a modularized power supply cascade connection technology, and the problem of voltage sharing among series devices or series modules is solved.

When the semiconductor devices are directly connected in series, the switching devices must work synchronously by precisely controlling the gate-level driving signals. The literature Gate-control structures for passive operation of devices connected IGBTs (PESC record.27th annular IEEE Power Electronics standards Conference, Baveno, Italy,1996, pp.1739-1742vol.2) proposes a synchronization technique using a delay circuit, which delays all driving signals to enable the switching devices to operate synchronously, but since the series switching devices have certain differences in their parameters, the delay parameters of the respective modules are different, and the isolation requirements of the driving are high, which brings difficulties for the modular design. Generally, the direct series connection scheme of the semiconductor devices has high technical requirements and cost, and the direct series connection scheme of the semiconductor devices is not suitable for application occasions with lower power and sensitive cost.

Currently, a common Modular power supply scheme includes an Input-series Output-parallel (ISOP) structure Converter, a Modular Multilevel Converter (MMC) and a cascade structure Converter. The modular multilevel converter adopts a two-stage voltage reduction structure, the front-stage submodule performs primary voltage reduction, the high voltage reduction ratio work is usually realized by a rear-stage converter, and the cascade structure converter obtains the high voltage reduction ratio through an input capacitor series structure and a converter with self voltage-sharing capability.

For the converter with the input series output parallel structure, the voltage unbalance degree among the modules depends on the circuit parameters and the consistency of the working state of the switching tube. The scheme used in the documents High-Voltage-Input, Low-Voltage-Output, Series Connected Converters with Uniform Voltage Distribution (2009IEEE Aerospace reference, Big Sky, MT,2009, pp.1-9) adjusts the operating state of the switching tubes in the modules through Voltage feedback, reducing the requirement for consistency of each module, but also needs a central controller and a Voltage detection device, and the system structure and control are complex. The document Wireless Input-Voltage-Sharing Control string for Input-Series Output-parallel (ISOP) System Based on Positive Output-Voltage Gradient Method (IEEE Transactions on Industrial Electronics, vol.61, No.11, pp.6022-6030, Nov.2014) proposes a Voltage-Sharing Method Based on Positive Output-Voltage Gradient, which still regulates the switching tube operating state by Voltage feedback to achieve Voltage-Sharing, each module has an independent controller, no communication is needed between the controllers, but the effect of Input Voltage-Sharing is related to the difference of Output Voltage gradients between the modules, and the effect of Input Voltage-Sharing is deteriorated as the number of modules increases, and in a System with an Input Series Output parallel structure, the Output isolation requirement of each module is high, and the design of the System is not favorable for the modularization of the System, and the modularization of the System is not favorable for the expansion of the application, in addition, the scheme has contradiction in the aspects of input voltage equalization and output voltage regulation, is not suitable for application occasions with wider input voltage range, and has relatively complex design and voltage equalization control.

Modular multilevel converters are another type of solution in medium and high voltage input scenarios. In the documents of Modular Multilevel Converter With Series and Parallel Module Connectivity, Topology and Control (IEEE Transactions on Power Electronics, vol.30, No.1, pp.203-215, jan.2015) proposes a Modular Multilevel Series-Parallel Converter (MMSPC), which changes the Series-Parallel relationship of the capacitors of each Module by changing the states of the switching tubes of the modules, and further controls the charging State (State of Charge, SOC) of each capacitor to realize input voltage sharing, but each Module includes two full bridges, and thus has a complex structure and high cost. Meanwhile, in the scheme of the modularized multi-level converter, a central controller is required, the sampling cost is high, the control complexity is extremely high, and the scheme is difficult to be used for high-voltage-reduction-ratio conversion with low power and low cost.

A cascaded configuration converter is easy to implement compared to the previous solution. The document "a high voltage drop modular dc power supply and its control method (chinese patent: CN 111740597A)" proposes a converter with a cascade structure, which realizes the voltage equalization of any two adjacent bus capacitors, and further realizes the input voltage equalization of the system, and obtains a high voltage reduction ratio. The drive and output isolation requirements are low, a central controller is not needed, and each module can work independently. However, the bus capacitor in the module needs to be subjected to voltage sampling and closed-loop control, and the control is relatively complex. In a steady state, the voltage borne by the switching tube is higher and is the same as the bus voltage of a single submodule. In addition, all modules work in a hard turn-off state, the loss is large, and the system does not have a self-powered part and cannot supply power for a self-control part, so that the practical application of the system is limited.

Disclosure of Invention

In view of the above, in order to solve the defects of limited applicable voltage level, high requirements on drive and output isolation, complex control strategy, hard turn-off during working and no self-power-taking capability in the prior art, the invention provides a switched capacitor type modular direct current power supply with high voltage reduction ratio, which is obtained by cascade combination of standardized sub-module circuits step by step, wherein two switch tubes in each sub-module circuit are connected in series, the single switch tube has low bearing voltage, the topology of each sub-module circuit is transformed from a basic series resonance circuit, and the power supply can adjust the number of cascade modules according to the input voltage level, and has good flexibility and strong expansibility. The controller of each module unit can work independently, communication and synchronous work are not needed among modules, voltage detection or current detection is not needed when the switch tube is controlled, voltage balance of each input series capacitor of the power supply and soft switching work of the switch tube can be achieved, the structure and control are simple, the power supply self-power-taking capability is achieved, the scheme cost is low, the realization is easy, and the power supply self-power-balancing control circuit is suitable for low-power supply application in medium-voltage or high-voltage direct-current input occasions.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the invention discloses a switch capacitor type modularized high voltage reduction ratio direct current power supply, which comprises:

the load is input source, an upper modular cascade circuit group string composed of i upper sub-module circuits and a lower modular cascade circuit group string composed of j lower sub-module circuits;

the upper sub-module circuit comprises an upper layer main capacitor, a lower layer main capacitor, an upper switch tube, a lower switch tube, an upper diode, a lower diode, a resonant inductor, an upper layer resonant capacitor, a lower layer resonant capacitor, an auxiliary transformer and three ports; the first port a, the positive electrode of an upper-layer main capacitor and the drain electrode of an upper switch tube are connected in common, the second port b, the negative electrode of the upper-layer main capacitor, the positive electrode of a lower-layer main capacitor, the source electrode of a lower switch tube, one end of a primary winding of an auxiliary transformer and the cathode of an upper diode are connected in common, the third port c, the negative electrode of the lower-layer main capacitor and the anode of a lower diode are connected in common, the source electrode of the upper switch tube, the drain electrode of the lower switch tube and the positive electrode of an upper-layer resonant capacitor are connected in common, one end of the upper-layer resonant capacitor and one end of a resonant inductor are connected in common with the other end of the primary winding of the auxiliary transformer, the anode of the upper diode, the cathode of the lower diode and the negative electrode of the lower-layer resonant capacitor are connected in common, and the other end of the resonant inductor is connected with the positive electrode of the lower-layer resonant capacitor;

the lower sub-module circuit comprises an upper-layer main capacitor, a lower-layer main capacitor, an upper switching tube, a lower switching tube, an upper diode, a lower diode, a resonant inductor, an upper-layer resonant capacitor, a lower-layer resonant capacitor and three output ports; the auxiliary transformer comprises a first port a, an upper-layer main capacitor anode and an upper diode cathode which are connected in common, a second port b, an upper-layer main capacitor cathode, a lower-layer main capacitor anode, a lower diode anode, one end of an auxiliary transformer primary winding and an upper switch tube drain electrode are connected in common, a third port c, a lower-layer main capacitor cathode and a lower switch tube source electrode are connected in common, an upper diode anode, a lower diode cathode and an upper-layer resonant capacitor anode are connected in common, an upper switch tube source electrode, a lower switch tube drain electrode and a lower-layer resonant capacitor cathode are connected in common, an upper-layer resonant capacitor cathode is connected with one end of a resonant inductor, and the other end of the auxiliary transformer primary winding, the other end of the resonant inductor and a lower-layer resonant capacitor anode are connected in common;

the upper modular cascade circuit group string comprises three upper ports, wherein the first upper port is connected with the port a of the first upper sub-module circuit, the second upper port is connected with the port c of the ith upper sub-module circuit, and the third upper port is connected with the port b of the ith upper sub-module circuit; the circuit connection mode of i upper submodules in the string is as follows: a second port b of the kth-1 upper sub-module circuit is connected with a first port a of the kth upper sub-module circuit, a third port c of the kth-1 upper sub-module circuit is connected with a second port b of the kth upper sub-module circuit, wherein k is more than or equal to 2 and less than or equal to i;

the lower modular cascaded circuit group string comprises three lower ports, a first lower port is connected with a port a of a first lower sub-module circuit, a second lower port is connected with a port b of the first lower sub-module circuit, and a third lower port is connected with a port c of a jth lower sub-module circuit; the circuit connection mode of j lower submodules in the string is as follows: the second port b of the kth-1 lower sub-module circuit is connected with the first port a of the kth lower sub-module circuit, the third port c of the kth-1 lower sub-module circuit is connected with the second port b of the kth lower sub-module circuit, and k is more than or equal to 2 and less than or equal to j;

when i is not equal to 0 and j is not equal to 0, the modular cascaded circuit group string is connected with an input source and a load in a mode that a first upper port of an upper modular cascaded circuit group string is connected with an input source anode, a third lower port of a lower modular cascaded circuit group string is connected with an input source cathode, a third upper port of the upper modular cascaded circuit group string and a first lower port of the lower modular cascaded circuit group string are connected with a load anode in a common mode, and a second upper port of the upper modular cascaded circuit group string and a second lower port of the lower modular cascaded circuit group string are connected with a load cathode in a common mode;

when i is more than or equal to 2 and j is equal to 0, the modular cascaded circuit group string is connected with the input source and the load in a mode that a first upper port of the upper modular cascaded circuit group string is connected with the anode of the input source, a third upper port of the upper modular cascaded circuit group string is connected with the anode of the load, and a second upper port of the upper modular cascaded circuit group string and the cathode of the load are connected with the cathode of the input source;

and when i is 0 and j is not more than 2, the modular cascaded circuit group string is connected with the input source and the load in a mode that a first lower port of the lower modular cascaded circuit group string, a load anode and an input source anode are connected in common, a second lower port of the lower modular cascaded circuit group string is connected with a load cathode, and a third lower port of the lower modular cascaded circuit group string is connected with an input source cathode.

In a preferred embodiment of the present invention, the power supply has no central controller, and each of the upper sub-module circuit and the lower sub-module circuit further includes an independent control module.

In a preferred embodiment of the present invention, i + j.gtoreq.3.

In a preferred embodiment of the present invention, i ≧ j and i ≧ 2, j ≧ 2.

In a preferred embodiment of the present invention, the upper switch tube and the lower switch tube may be fully-controlled power semiconductor devices.

The invention also discloses a control method (self-power-taking method) of the off-capacitance type modular high-voltage-reduction-ratio direct-current power supply, which comprises the following steps:

the control module in each of the upper sub-module circuit and the lower sub-module circuit outputs two complementary PWM signals with the duty ratio of 50 percent, the two PWM signals are respectively used as control signals of an upper switch tube and a lower switch tube in the sub-module circuit to lead the upper switch tube and the lower switch tube in the upper sub-module circuit and the lower sub-module circuit to be alternately conducted,

for the upper submodule, when the driving signal of the upper switch tube is 1, the driving signal of the lower switch tube is 0, the upper switch tube is conducted, the lower switch tube is turned off, the upper layer main capacitor transmits energy to the upper layer resonance capacitor and the lower layer resonance capacitor, meanwhile, the upper layer bus capacitor injects energy to the primary side winding of the auxiliary transformer to supply energy to the control module in the upper submodule, when the driving signal of the upper switch tube is 0, the lower switch tube drives signal 1, the upper switch tube is turned off, the lower switch tube is conducted, the upper layer resonance capacitor and the lower layer resonance capacitor transmit energy to the lower layer main capacitor, meanwhile, the upper layer resonance capacitor injects energy to the primary side winding of the auxiliary transformer to supply energy to the control module of the submodule, and in the working process, the turn-off voltage born by the upper switch tube and the lower switch tube is only the terminal voltage of a single main capacitor, namely the general bus voltage of the submodule circuit,

for the lower submodule, when the driving signal of the upper switch tube is 0, the driving signal of the lower switch tube is 1, the upper switch tube is turned off, the lower switch tube is turned on, the lower main capacitor transmits energy to the upper resonant capacitor and the lower resonant capacitor, meanwhile, the lower main capacitor injects energy into the primary side winding of the auxiliary transformer to supply energy to a control module inside the submodule, when the driving signal of the upper switch tube is 1, the lower switch tube drives signal 0, the upper switch tube is turned on, the lower switch tube is turned off, the upper resonant capacitor and the lower resonant capacitor transmit energy to the upper main capacitor, meanwhile, the lower resonant capacitor injects energy into the primary side winding of the auxiliary transformer to supply energy to the control module inside the submodule, and in the working process, the turn-off voltage born by the upper switch tube and the lower switch tube is only the terminal voltage of a single main capacitor, namely, half of the bus voltage of the submodule circuit.

In a preferred embodiment of the invention, the control module does not sample the capacitor voltage or the inductor current in the upper and lower submodule circuits.

Based on the technical scheme, compared with the prior art, the invention has the beneficial effects that:

(1) according to the switched capacitor type modular high-voltage-reduction-ratio direct-current power supply, communication and synchronization are not needed among the power supply sub-modules, and the control modules in the power supply sub-modules completely and independently work, so that standardized modular design can be realized, and expansibility is high.

(2) The power supply adopts the standard modules to be directly cascaded, the cascade number can be adjusted according to the input voltage grade, the flexibility is high, and the power supply is suitable for being applied to low-power supplies in medium-voltage or high-voltage direct-current input occasions.

(3) The adopted control scheme is simple, closed-loop feedback control is not required to be carried out through voltage or current sampling, the system can work normally by outputting two complementary driving signals with the duty ratio of 50%, and the method is easy to realize and low in cost.

(4) The switching tube of the non-isolated three-port switch capacitor resonance type circuit adopted by the invention has low voltage stress and simple type selection, and the number of the series modules can be reduced when the same input voltage is applied.

(5) The submodule circuit of the invention has the self-power-taking capability, and the module internal circuit comprises a part for supplying power to the control module.

Drawings

FIG. 1 is a circuit topology diagram of an upper submodule according to an embodiment of the present invention;

FIG. 2 is a block diagram of a control module of the upper sub-module circuit according to an embodiment of the present invention;

FIG. 3 is a circuit topology diagram of a lower submodule according to an embodiment of the present invention;

FIG. 4 is a block diagram of a control module of the lower sub-module circuit according to an embodiment of the present invention;

FIG. 5 is a diagram of the internal connections of the upper modular cascode string of the switched capacitor type high buck ratio DC power supply in accordance with one embodiment of the present invention;

FIG. 6 is a diagram of the internal connection of the lower modular cascode string of the switched capacitor modular high buck ratio DC power supply in accordance with one embodiment of the present invention;

FIG. 7 is a diagram of exemplary system connections for a switched capacitor type modular high voltage to low ratio DC power supply in accordance with one embodiment of the present invention;

FIG. 8 is a diagram of exemplary system connections for a switched capacitor type modular high voltage to low ratio DC power supply in accordance with one embodiment of the present invention;

FIG. 9 is a diagram of exemplary system connections for a switched capacitor type modular high voltage to low ratio DC power supply in accordance with one embodiment of the present invention;

FIG. 10 is a system diagram of a switched capacitor type modular high buck ratio DC power supply in accordance with one embodiment of the present invention;

fig. 11 is a schematic diagram of voltage sharing and self-power-taking processes inside a sub-module circuit of the switched capacitor type modular high-voltage-reduction-ratio dc power supply according to an embodiment of the present invention; the charging circuit is characterized by comprising an upper layer resonance capacitor, a lower layer resonance capacitor, an auxiliary transformer and a charging circuit, wherein (a) is a schematic diagram of the charging circuit when the upper layer main capacitor charges the upper layer resonance capacitor, the lower layer resonance capacitor and the primary side of the auxiliary transformer, and (b) is a schematic diagram of the charging circuit when the upper layer resonance capacitor charges the lower layer main capacitor and the upper layer resonance capacitor charges the primary side of the auxiliary transformer;

fig. 12 is a schematic diagram of voltage-sharing and self-power-taking processes inside a sub-module circuit under the switched capacitor type modular high-voltage-reduction ratio dc power supply according to an embodiment of the invention; the charging circuit is characterized by comprising a charging circuit, a charging circuit and a charging circuit, wherein (a) the charging circuit is a schematic diagram of a charging circuit when a lower-layer main capacitor charges an upper-layer resonance capacitor, a lower-layer resonance capacitor and a primary side of an auxiliary transformer, and (b) the charging circuit is a schematic diagram of the charging circuit when the upper-layer resonance capacitor, the lower-layer resonance capacitor charges the upper-layer main capacitor and the lower-layer resonance capacitor charges the primary side of the auxiliary transformer;

fig. 13(a) - (d) are respectively a driving signal waveform diagram and a resonant inductor current waveform diagram of the upper sub-module 1, the upper sub-module 2, the lower sub-module 1 and the lower sub-module 2 in the example of the switched capacitor type modular high-voltage-reduction ratio dc power supply according to the embodiment of the invention in fig. 10;

fig. 14(a) - (d) are diagrams of waveforms of driving signals of the upper submodule 1, the upper submodule 2, the lower submodule 1 and the lower submodule 2 in fig. 10 and waveforms of primary winding voltages of the auxiliary transformer, respectively, of the switched capacitor type modular high-voltage-reduction-ratio dc power supply according to the embodiment of the present invention;

FIG. 15 is a voltage waveform diagram of each main capacitor in FIG. 10 for an example of a switched capacitor type modular high buck ratio DC power supply in accordance with an embodiment of the present invention;

FIG. 16 is a diagram of voltage waveforms of the main capacitors of the example power supply of FIG. 10 during load shedding in accordance with an embodiment of the present invention;

fig. 17(a) - (d) are graphs of voltage stress waveforms of the upper switching tube in the upper sub-module 1, the upper sub-module 2, the lower sub-module 1, and the lower sub-module 2 in fig. 10, respectively, of the switched capacitor type modular high-voltage-to-low-voltage ratio dc power supply according to the embodiment of the invention.

Detailed Description

To make the above and other features and advantages of the power supply of the present invention more apparent, a detailed description of an embodiment of the power supply will be given with reference to the accompanying drawings. The technical characteristics of the embodiments of the invention can be correspondingly combined on the premise of no mutual conflict.

The invention relates to a switched capacitor type modular high-voltage-reduction-ratio direct-current power supply which comprises a load, an input source, an upper modular cascade circuit group string consisting of i upper sub-module circuits and/or a lower modular cascade circuit group string consisting of j lower sub-module circuits. Each sub-module circuit comprises an independent control module, and the control module generates two paths of complementary PWM waves with the duty ratio of 50 percent as driving signals of the switch tubes in the sub-module circuit to enable the two switch tubes to be conducted complementarily.

Fig. 1 is a circuit topology of an upper sub-module, the upper sub-module circuit includes three output ports a, b, and c and an independent control module, and the circuit connection mode is as follows: port a, upper layer main capacitor C_n-1Positive electrode of (2) and upper switching tube Q_n-1The drain electrodes of the first and second transistors are connected in common, the port b and the upper layer main capacitor C_n-1Negative electrode, lower layer main capacitor C_n-2Positive electrode, lower switch tube Q_n-2Source electrode, upper diode D_n-1And auxiliary transformer T_nOne end of the primary winding is connected in common, a port C and a lower layer main capacitor C_n-2Cathode and lower diode D_n-2Anode of the upper switch tube Q is connected in common_n-1Source electrode, lower switch tube Q_n-2Drain electrode of and upper layer resonance capacitor C_n-3Is connected to the upper diode D_n-1Anode and lower diode D of_n-2Cathode and lower layer resonant capacitor C_n-4Is connected with the negative pole of the resonant inductor L_nOne end of and a lower layer resonance capacitor C_n-4The positive pole of the capacitor is connected with the upper layer resonance capacitor C_n-3Negative pole of (2), auxiliary transformer T_nThe other end of the primary winding and the resonant inductor L_nThe other ends of the two are connected together.

FIG. 2 is a block diagram of a control module of the upper sub-module circuit, which outputs two PWM signals G_n-1And G_n-2The duty ratio of two paths of PWM signals is 50 percentServing as an upper switch tube Q_n-1And a lower switching tube Q_n-2The two switch tubes are conducted complementarily by the control signal.

Fig. 3 is a circuit topology of a lower sub-module, where the lower sub-module circuit includes three output ports a, b, and c and an independent control module, and the circuit connection mode is: port a, upper layer main capacitor C_m-1Anode and upper diode D_m-1The cathode of the capacitor is connected in common, the port b and the upper layer main capacitor C_m-1Negative electrode, lower layer main capacitor C_m-2Anode, lower diode D_m-2Anode of (2), upper switch tube Q_m-1Drain electrode of and auxiliary transformer T_mOne end of the primary winding is connected in common, a port C and a lower layer main capacitor C_m-2Negative electrode of (1) and lower switching tube Q_m-2Is connected to the upper diode D_m-1Anode and lower diode D of_m-1And upper resonant capacitor C_m-3Is connected with the upper switch tube Q_m-1Source electrode, lower switch tube Q_m-2Drain electrode of and lower layer resonance capacitor C_m-4Is connected with the negative pole of the resonant inductor L_mAnother terminal of (1) and a resonant capacitor C_m-3Is connected with the negative pole of the resonant inductor L_mThe other end of (1), an auxiliary transformer T_mThe other end of the primary winding and the lower resonant capacitor C_m-4The positive electrodes of the two electrodes are connected in common.

FIG. 4 is a block diagram of a control module of the lower sub-module circuit, which outputs two complementary PWM signals G_m-1And G_m-2The duty ratios of two paths of PWM signals are both 50 percent and are respectively used as an upper switch tube Q_m-1And a lower switching tube Q_m-2The two switch tubes are conducted complementarily by the control signal.

Fig. 5 is a diagram of internal connections of a modular cascade circuit string on a switched capacitor type modular high-voltage-reduction-ratio dc power supply according to an embodiment of the present invention, where i upper sub-module circuits are depicted in fig. 5, and i > 4. In practical application, i is a natural number greater than 2. The first upper port of the upper modular cascaded circuit group string is connected with the port a of the upper sub-module circuit 1, the second upper port of the upper modular cascaded circuit group string is connected with the port c of the upper sub-module circuit i, and the third upper port of the upper modular cascaded circuit group string is connected with the port b of the upper sub-module circuit 1. The internal connection mode of the modularized cascade circuit group string is as follows: the port b of the upper sub-module circuit k-1 is connected with the port a of the upper sub-module circuit k, the port c of the upper sub-module circuit k-1 is connected with the port b of the upper sub-module circuit k, and k is more than or equal to 2 and less than or equal to i.

Fig. 6 is a diagram of internal connections of a modular cascaded circuit string under a switched capacitor type modular high-voltage-reduction-ratio dc power supply according to an embodiment of the present invention, where j lower sub-module circuits are depicted in fig. 6, and j > 4. In practical applications, j is a natural number greater than 2. The first lower port of the lower modular cascaded circuit group string is connected with the port a of the lower sub-module circuit 1, the second lower port of the lower modular cascaded circuit group string is connected with the port b of the lower sub-module circuit 1, and the third lower port of the upper modular cascaded circuit group string is connected with the port c of the lower sub-module circuit j. The internal connection mode of the modularized cascade circuit group string is as follows: the port b of the lower sub-module circuit k-1 is connected with the port a of the upper sub-module circuit k and the port c of the lower sub-module circuit k-1 is connected with the port b of the lower sub-module circuit k, wherein k is more than or equal to 2 and less than or equal to i.

Fig. 7 is a system connection diagram of a switched capacitor type modular high step-down ratio dc power supply according to an embodiment of the present invention, where the number i of upper sub-modules is not equal to 0, and the number j of lower sub-modules is equal to 0. The first upper port of the upper modular cascaded circuit group string is connected with the anode of the input power supply, the second upper port of the upper modular cascaded circuit group string and the cathode of the load are connected with the cathode of the input power supply, and the third upper port of the upper modular cascaded circuit group string is connected with the anode of the load.

Fig. 8 is a system connection diagram of the switched capacitor type modular high step-down ratio dc power supply according to an embodiment of the present invention when the lower module group is cascade-connected, where the number i of the upper sub-modules is 0, and the number j of the lower sub-modules is not 0. The first lower port of the lower modular cascaded circuit group string, the load anode and the input power supply anode are connected together, the second lower port of the lower modular cascaded circuit group string is connected with the load cathode, and the third lower port of the lower modular cascaded circuit group string is connected with the input power supply cathode.

Fig. 9 is a system connection diagram of the switched capacitor type modular high-voltage-reduction-ratio dc power supply according to an embodiment of the present invention, where the upper and lower module strings are mixed and cascaded, and the number of the upper and lower sub-modules is not 0. The first upper port of the upper modular cascaded circuit group string is connected with the anode of an input source, the third lower port of the lower modular cascaded circuit group string is connected with the cathode of the input source, the third upper port of the upper modular cascaded circuit group string and the first lower port of the lower modular cascaded circuit group string are connected with the anode of a load in a sharing mode, and the second upper port of the upper modular cascaded circuit group string and the second lower port of the lower modular cascaded circuit group string are connected with the cathode of the load in a sharing mode.

Taking the number of sub-modules as an example of 4, when the switched capacitor type modular high-voltage-reduction-ratio dc power supply according to an embodiment of the present invention adopts an upper module group cascade connection method, a system connection diagram is shown in fig. 7, where i is 4, and j is 0; when the switched capacitor type modular high step-down ratio dc power supply of an embodiment of the present invention adopts a lower module group cascade connection method, a system connection diagram is shown in fig. 8, where i is 0, and j is 4; when the switched capacitor type modular high step-down ratio dc power supply according to an embodiment of the present invention adopts a hybrid cascade connection method of upper and lower module series, a system connection diagram is shown in fig. 9, where i is 2 and j is 2.

Fig. 10 is a connection diagram of a switched capacitor type modular high step-down ratio dc power supply system according to an embodiment of the present invention, in which an upper module and a lower module are cascaded in a mixed manner, and i ═ j ═ 2, in the following, simulation verification is performed on the power supply of this example, the voltage of the dc power supply used in the verification is 10KV, the load size is 2K Ω, and the power supply of this example has 5 power supplies input to the series capacitors, so the voltage on each capacitor and the output voltage should be 2 KV.

Fig. 13(a) - (d) show waveforms of driving signals and inductive currents of the switching tubes in a period of time in the upper sub-module 1, the upper sub-module 2, the lower sub-module 1, and the lower sub-module 2 of the example of the switched capacitor type modular high-voltage-to-low-voltage ratio dc power supply of the embodiment of the invention in fig. 10. Each waveform diagram is respectively as follows from top to bottom: an upper switch tube driving signal (black solid line) of the sub-module circuit, a lower switch tube driving signal (black dotted line) of the sub-module circuit, and a resonant inductor current (black dotted line) of the sub-module circuit. It can be seen from the figure that the phases of the driving signals of the upper switch tubes in each sub-module are different, so that the operation of the switch tubes of each sub-module is asynchronous. For the circuit of the upper sub-module, when the driving signal of the upper switch tube is 1 and the driving signal of the lower switch tube is 0, the upper switch tube is switched on, the lower switch tube is switched off, the upper layer main capacitor discharges to the resonance branch, when the driving signal of the upper switch tube is 0 and the driving signal of the lower switch tube is 1, the upper switch tube is switched off, the lower switch tube is switched on, and the resonance branch discharges to the lower layer main capacitor. The schematic diagram of the voltage equalizing process of the upper submodule is shown in FIG. 11. For the lower sub-module circuit, when the upper tube driving signal is 0 and the lower tube driving signal is 1, the upper switch tube is turned off, the lower switch tube is turned on, the lower main capacitor discharges to the resonance branch, when the upper tube driving signal is 1 and the lower tube driving signal is 0, the upper switch tube is turned on, the lower switch tube is turned off, and the resonance branch discharges to the upper main capacitor. The schematic diagram of the pressure equalizing process of the lower submodule is shown in figure 12.

Fig. 14(a) - (d) show waveforms of the driving signal of the switching tube and the voltage at the primary winding end of the auxiliary transformer in a period of time in the upper submodule 1, the upper submodule 2, the lower submodule 1 and the lower submodule 2 of the example of the switched capacitor type modular high-voltage-reduction-ratio dc power supply of the embodiment of the invention. Each waveform diagram is respectively as follows from top to bottom: the voltage control circuit comprises an upper switch tube driving signal (a black solid line) of the sub-module circuit, a lower switch tube driving signal (a black dotted line) of the sub-module circuit and a primary side winding terminal voltage (a black dotted line) of an auxiliary transformer of the sub-module circuit. For an upper sub-module circuit, when an upper switch tube driving signal is 1 and a lower switch tube driving signal is 0, an upper switch tube is switched on, a lower switch tube is switched off, an upper layer main capacitor supplies power to a primary winding of an auxiliary transformer, when the upper switch tube driving signal is 0 and the lower switch tube driving signal is 1, the upper switch tube is switched off, the lower switch tube is switched on, and an upper layer resonant capacitor supplies power to the primary winding of the auxiliary transformer. The process of the upper sub-module supplying power to the primary winding of the auxiliary transformer is shown in fig. 11. For the lower sub-module circuit, when the upper tube driving signal is 0 and the lower tube driving signal is 1, the upper switch tube is turned off, the lower switch tube is turned on, the lower main capacitor supplies power to the primary winding of the auxiliary transformer, when the upper tube driving signal is 1 and the lower tube driving signal is 0, the upper switch tube is turned on, the lower switch tube is turned off, and the lower resonant capacitor supplies power to the primary winding of the auxiliary transformer. The schematic diagram of the process of the lower sub-module supplying power to the primary winding of the auxiliary transformer is shown in fig. 12.

Fig. 15 shows voltage waveforms of the main capacitors in fig. 10 of an example of a switched capacitor type modular high voltage drop ratio dc power supply according to an embodiment of the present invention, where an upper layer main capacitor of an upper sub-module 1 is a main capacitor 1, a lower layer main capacitor of the upper sub-module 1 is connected in parallel with an upper layer main capacitor of an upper sub-module 2 to form an upper layer main capacitor 2, a lower layer main capacitor of the upper sub-module 2 is connected in parallel with an upper layer main capacitor of a lower sub-module 1 to form a main capacitor 3, a lower layer main capacitor of the upper sub-module 1 is connected in parallel with an upper layer main capacitor of a lower sub-module 2 to form a main capacitor 4, a lower layer main capacitor of the lower sub-module 2 is a main capacitor 5, where a terminal voltage of the main capacitor 3 is an output voltage. The waveform diagram shows that the voltage of the main capacitor is well balanced and is consistent with the expectation, and the input voltage equalization is realized.

Fig. 16 shows waveforms of main capacitors in the example power supply when the load of the example dc power supply of fig. 10 suddenly changes according to the embodiment of the present invention. The example power supply input voltage is still 10KV, the load before loading is 2K Ω, the power supply output has reached steady state before t is 0.3s, the circuit is suddenly loaded when t is 0.3s, the load becomes 1K Ω, and the load size is maintained constant during the time period t is [0.3s,0.4s ]. When t is 0.4s, the load is suddenly applied again, the load becomes 666.7 Ω, and the load is maintained for a period of time t [0.4s,0.5s ]. When t is 0.5s, the load is suddenly unloaded, the load is changed back to 2K Ω, and the load is kept unchanged during the time period t [0.5s,0.6s ]. In the whole process, the voltage of each series capacitor is maintained at about 2000V, and the maximum deviation from the expected value is controlled within +/-0.43 percent.

Fig. 17(a) - (d) respectively show voltage stress waveform diagrams of switching tubes of the upper sub-module 1, the upper sub-module 2, the lower sub-module 1, and the lower sub-module 2 in the example of the switched capacitor type modular high-voltage-reduction-ratio dc power supply according to the embodiment of the present invention, where the test condition is still 10KV dc voltage input, and the load size is 2K Ω. Since the voltage stress waveforms of the upper tube and the lower tube in the module are almost consistent in amplitude and only differ in phase by 180 degrees, only the voltage stress waveform of the switching tube on each module is given. It can be seen that the maximum voltage stress borne by the switch tube in the module is the same as the terminal voltage of the main capacitor, and is only half of the bus voltage of the module, namely 2 KV.

In summary, the switched capacitor type modular high-step-down ratio dc power supply according to the embodiment of the invention shown in fig. 10 can realize voltage sharing among main capacitors of the power supply in a state that switching tubes of modules work asynchronously, and when a load suddenly changes, voltages among the main capacitors can be well balanced, and a voltage or current detection device is not needed for feedback control, communication among sub-modules is not needed, so that the scheme is easy to implement and low in cost. According to the input voltage grade, the number of the modules can be flexibly adjusted, and the expansibility is good. The voltage stress born by the switch tube in the sub-module is small and is only half of the module bus voltage, so that the number of the used modules can be less and the model selection of the switch tube is simpler under the condition of the same input voltage grade.

The above examples specifically illustrate and describe exemplary implementations of the present invention, and the above examples are merely illustrative of the technical solutions of the present invention so as to facilitate one of ordinary skill in the art to understand and apply the present invention, and the present invention is not limited to the detailed structures, arrangements, or implementations described herein. It should be noted that it will be readily apparent to those skilled in the art that various modifications can be made to the above-described embodiments, or some or all of the technical features of the present invention can be equally substituted, or the general principles described herein can be applied to other embodiments without the necessity of inventive faculty, and modifications, improvements or equivalents of the technical features of the present invention should fall within the scope of the present invention.