TWI552473B - Parallel system of DC power supply and its control method - Google Patents

Description

DC power supply parallel system and control method thereof

The invention relates to a DC power supply parallel system and a control method thereof, in particular to a power supply parallel system combining the virtual voltage drop method and the master-slave architecture to balance the current sharing and voltage adjusting capability.

In order to ensure the stability and reliability of the power supply system, most power supply systems modularize the power supply and connect the power modules of a specific specification series in series or in parallel. When multiple power modules are connected in parallel, the whole power system can not be completely ensured to work stably and reliably. The prerequisite for stable operation is equalization and current sharing. In terms of current sharing, the main tasks include: when the load changes, The output voltage of each power module changes the same. And the output current of each power module is evenly distributed according to the rated power.

As for the prior art of parallel connection, there are mainly two types, one is the Active Current-Sharing Method, and the other is the Droop Method. The active current sharing method includes the average current method (Average current). Method), Dedicated Master Method and Automatic Master Method. The so-called voltage drop method, as shown in FIG. 3, a plurality of power modules M1 to Mn are connected in parallel with the load to form a parallel system. In theory, each power module M1~Mn should meet the same voltage. Same current, same output Impedance requirements, but the preset value and the actual value are always different, and the above difference will affect the current sharing of the parallel system, taking the first and second power modules M1, M2 as an example, as shown in Figure 4. The vertical axis represents the output voltage Voi, the horizontal axis represents the output current Io, and the power modules M1, M2 have different output voltages Vno1, Vno2, respectively, and the output of the power modules M1, M2 when the steady state power supply is reached. The currents are Io1 and Io2, respectively, and the output current difference in this state is ΔIo. The voltage drop method means that if the output voltages Vno1 and Vno2 of the power modules M1 and M2 are lowered, the output currents of the power modules M1 and M2 are I'o1 and I'o2, respectively, as shown in FIG. The value is reduced to ΔI'o, thereby contributing to the implementation of the current sharing.

In the past, the most straightforward method for implementing the voltage drop method described above is to connect resistors in series with the output terminals of the respective power modules M1 to Mn. As the output impedance is increased, the output voltage is relatively decreased. However, such an approach is bound to increase power consumption and affect power efficiency.

It can be seen from the above that although the conventional voltage drop method contributes to the purpose of current sharing in a parallel power supply system, the voltage drop is generated by increasing the impedance, which causes loss and poor voltage adjustment capability, and therefore needs further review and seeks a feasible solution. Program.

Therefore, the main object of the present invention is to provide a DC power supply parallel system, which is to perform voltage drop in each of the DC power modules connected in parallel in the system to solve the power loss caused by the series resistance; and more than one DC power supply The module simultaneously performs constant voltage control to improve the voltage adjustment capability of the parallel system.

The main technical means to achieve the above objectives is to The parallel power supply system includes a plurality of DC power supply modules, each of the DC power supply modules has a power input end and a power output end, and each of the DC power supply modules is respectively connected to each other by a power input end and a power output end. To form a parallel architecture; each DC power module includes: a power converter connected between the power input end and the power output end, the power converter has a control end; a pulse width modulation controller, The utility model has an input end and an output end, wherein the output end is connected with the control end of the power converter; a voltage controller has two input ends and an output end, the output of the voltage controller and the input of the pulse width modulation controller a voltage feedback unit connected between the power output terminal and an input terminal of the voltage controller; a virtual voltage drop operation unit having a feedback signal input terminal, a reference voltage input terminal, and an adjustment voltage input terminal And a control signal output end, the feedback signal input end and the power output end are connected, the control signal output end and the other input end of the voltage controller The virtual voltage drop computing unit compares the feedback voltage of the power supply output with the reference voltage of the reference voltage input terminal to generate a control signal to the voltage controller to reduce the power converter through the pulse width modulation controller. The voltage is output, and the virtual voltage drop method is performed. The DC power module further includes a voltage adjustment unit having a feedback voltage input terminal, a reference voltage input terminal, and an adjustment voltage output terminal. The voltage input end is connected to the power output end, and the adjustment voltage output end is connected to the adjustment voltage input end of the virtual voltage drop operation unit; the voltage adjustment unit is based on the feedback voltage and a reference After the voltage calculation, an adjusted voltage is generated and sent to the virtual voltage drop computing unit; the parallel system is implemented by the virtual voltage drop method of each of the parallel DC power supply modules by the virtual voltage drop calculation unit according to the feedback voltage and the reference voltage of the power output end. In order to reduce the output current difference and achieve the current sharing purpose, and the execution of the virtual voltage drop method causes the output voltage to drop, the voltage adjustment unit in the DC power supply module can be used to adjust the output voltage to a normal state, thereby taking into account both of the parallel systems. Flow and voltage adjustment capabilities.

It is still another object of the present invention to provide a control method for a DC power supply parallel system that satisfies the current sharing requirement and improves the voltage adjustment capability.

The main technical means for achieving the above object is to make the foregoing control method include the following steps: providing a plurality of DC power supply modules, and making each DC power supply module parallel with each other with its power input end and power output end; The group respectively performs a virtual voltage drop method, which is called a virtual voltage drop method, in which each DC power supply module changes the output signal of the power supply output by changing the feedback signal of the power supply output to simulate the output impedance; The power module performs constant voltage control to adjust the output voltage at the output of the power supply.

In the foregoing method, each DC power supply module is used to change the feedback signal at the output end of the power supply to reduce the output voltage of the power output terminal, thereby achieving the purpose of current sharing; since the current sharing is achieved by reducing the output voltage of the output end of the power supply, the analog output impedance is improved. Not connected in series at the power output Resistance, so there is no problem of power consumption on the resistor; although the voltage drop method is to virtually increase the output impedance, the output voltage is still reduced, so that more than one DC power module performs constant voltage control on the output voltage. Improve the voltage adjustment capability of the parallel system.

10A, 10B~10n‧‧‧DC power supply module

11‧‧‧Power Converter

12‧‧‧ Pulse width modulation controller

13‧‧‧Voltage controller

14‧‧‧Voltage feedback unit

15‧‧‧Virtual voltage drop computing unit

151‧‧‧First Operator

152‧‧‧Secondary

20A, 20B~20n‧‧‧Voltage adjustment unit

21‧‧‧Voltage controller

22‧‧‧Operator

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram of a first preferred embodiment of a parallel system of the present invention.

Figure 2 is a block diagram of a second preferred embodiment of the parallel system of the present invention.

Figure 3 is a schematic diagram of a parallel system known to perform a voltage drop method.

4 is a graph showing the relationship between the output current and the output impedance in the voltage drop method.

The technical means adopted by the present invention for achieving the intended purpose of the invention are further described below in conjunction with the drawings and preferred embodiments of the invention.

For a first preferred embodiment of the parallel system of the present invention, please refer to FIG. 1 , which includes a plurality of DC power modules 10A , 10B 10 10n , each of which has a power input And a power output end, each power input end is connected to each other to jointly connect the input power, and the power output ends of the respective DC power modules 10A, 10B~10n are also connected to each other to be connected to the load in common to form a parallel system.

For the specific structure of each of the DC power modules 10A and 10B to 10n, one of the DC power modules 10A will be described as an example. The other DC power modules 10B to 10n have the same structure, and the DC power supply is not described here. The module 10A includes a power converter 11, a pulse width modulation controller 12, a voltage controller 13, and a voltage feedback unit. 14 and a virtual voltage drop computing unit 15; wherein: the power converter 11 can be an AC to DC converter (AC / DC), or a DC to DC converter (DC / DC), the former is used in the input power It is a place for AC power, and the latter is used when the input power source is a DC voltage source. The power converter 11 is connected between its power input terminal and the power output terminal. The power converter 11 has a control terminal for connecting to the pulse width modulation controller 12.

The pulse width modulation controller 12 has an input end and an output end, the output end of which is connected to the control end of the power converter 11 , and the output voltage of the power converter 11 is adjusted through a modulation pulse width (PWM) mode; The input of the pulse width modulation controller 12 is connected to the voltage controller 13.

The voltage controller 13 has two input terminals and an output terminal, and an output terminal thereof is connected to the input end of the pulse width modulation controller 12, wherein an input terminal is connected through the voltage feedback unit 14 and the power output terminal.

The virtual voltage drop computing unit 15 has a feedback signal input terminal, a reference voltage input terminal Vor, an adjustment voltage input terminal Vc, and a control signal output terminal, and the feedback signal input terminal is connected to the power output terminal, and the control The signal output terminal is connected to the other input end of the voltage controller 13; in this embodiment, the virtual voltage drop operation unit 15 has a first operator 151 and a second operator 152, the first and second operators 151, 152 respectively have a two-parameter end and an output end, a parameter end of the first computing unit 151 is connected to the power output end, and an output end thereof constitutes the aforementioned control signal output end, and is connected to the other input end of the voltage controller 13 The other parameter end of the first operator 151 is connected to the output end of the second operator 152, and the two parameter ends of the second operator 152 respectively form the aforementioned reference voltage input terminal. Vor, the adjustment voltage input terminal Vc: the control signal outputted to the voltage controller 13 is changed by the operation result of the first and second operators 151 and 152, and the power converter 11 is outputted through the pulse width modulation controller 12 The voltage is increased by the output impedance of the virtual DC power supply module 10A to perform a voltage drop method to achieve a current sharing purpose.

In order to solve the problem that the voltage adjustment capability of the parallel system realized by the voltage drop method is not good, the present invention further performs constant voltage (CV) control on the parallel system by more than one DC power supply module 10A to improve the voltage adjustment of the parallel system. ability. In this embodiment, one of the DC power modules 10A is provided with a voltage adjusting unit 20A, and the DC power module 10A is used as a main module (Master) to perform constant voltage control on the output voltage, and other DC power modules. 10B~10n is used as a slave module (Slave) to form a master-slave architecture.

The voltage adjustment unit 20A has a feedback voltage input terminal, a reference voltage input terminal Vor and an adjustment voltage output terminal. The feedback voltage input terminal is connected to the power supply output terminal, and the adjustment voltage output terminal and the virtual voltage drop operation unit 15 are connected. Adjusting voltage input terminal Vc is connected; In this embodiment, the voltage adjustment unit 20A includes a voltage controller 21 and an operator 22 having two input terminals respectively connected to the power output terminal and the reference voltage input terminal Vor; the operator 22 The utility model has a two-parameter end and an output end, the output end of which is connected with the adjusting voltage input end of each DC power supply module 10A, 10B~10n, wherein one parameter end is connected with the output end of the voltage controller 21, and another parameter end and reference The voltage input terminal Vor is connected.

Under the foregoing architecture, each DC power module 10A, 10B~10n Although the output voltage is lowered by the operation of the virtual voltage drop operation unit 15, the voltage drop method is performed and the current sharing purpose is achieved. However, the DC power module 10A as the main module performs constant voltage control on the output voltage, and the voltage controller 21 of the voltage adjusting unit 20A is the reference voltage of the reference power output terminal and the reference voltage of the reference voltage input terminal Vor, and The operator 22 generates an adjusted voltage signal and sends it to the virtual voltage drop computing unit 15 of each of the DC power modules 10A, 10B-1010 to participate in the operation of sending a control signal to the voltage controller 13, thus in the parallel system. The output voltage is still available for effective control.

Referring to FIG. 2, the basic composition of each DC power module 10A, 10B~10n is substantially the same as that of the previous embodiment, except that in this embodiment, Each of the DC power modules 10A, 10B~10n is respectively provided with a voltage adjusting unit 20A, 20B~20n, and the adjusting voltage output ends of the voltage adjusting units 20A, 20B~20n respectively pass through a diode and all the DC power modules. The adjustment voltage input terminals of the virtual voltage drop computing unit 15 of 10A, 10B to 10n are connected. In this case, an automatic master-slave control architecture will be constructed. Under the foregoing architecture, each of the DC power modules 10A, 10B~10n is provided with a voltage adjusting unit 20A, 20B~20n for performing control on the output voltage, but actually one DC power module 10A, 10B~10n As the main module for control, it is maneuverable. It mainly depends on which DC power supply module 10A, 10B~10n output the maximum adjustment voltage, that is, the main module qualification is obtained, and other DC power supply modules 10B~10n are used as the slave mode. group.

The same as the previous embodiment is that each DC power supply module 10A, 10B~10n is controlled by its virtual voltage drop operation unit 15. Do not perform a virtual voltage drop method in order to achieve the purpose of current sharing. The control of the output voltage is performed by one of the DC power modules 10A, 10B~10n, and as to which of the DC voltage modules 10A, 10B~10n, the voltage adjusting units 20A, 20B~20n When the output adjustment voltage is the largest, the master control right can be obtained, and the adjustment voltage is output to the virtual voltage drop operation unit 15 of all the DC power supply modules 10A, 10B~10n to participate in the operation of the control signal to improve the adjustment capability of the output voltage.

The foregoing embodiments mainly emphasize that the output current difference of each DC power module is reduced by the virtual voltage drop method to achieve the purpose of current sharing, and then one of the DC power modules performs constant voltage control to improve the output voltage adjustment capability. . In addition, since the present invention adopts the virtual voltage drop method, it can simulate that each DC power supply module has different output impedances. When the output impedance is different, the output current distributed by the DC power supply module is also different, for example, the DC power supply module 10A. The output impedance is twice that of the other DC power module 10B, and the output current to which the DC power module 10A is distributed is one-half of the other DC power module 10B. In this case, it means The present invention can support DC power modules of the same voltage but different currents (capacity) in parallel with each other, and all DC power modules of the existing parallel system must be of the same specification, and DC power modules of different capacities can no longer be utilized. The problem of waste.

The above is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Although the present invention has been disclosed in the above preferred embodiments, it is not intended to limit the present invention. A person may make some changes or modify the equivalent change when using the technical content disclosed above without departing from the technical solution of the present invention. The invention is not limited to the scope of the technical solutions of the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiments in accordance with the technical spirit of the present invention are not included in the technical scope of the present invention.

10A, 10B, 10n‧‧‧ DC power modules

11‧‧‧Power Converter

12‧‧‧ Pulse width modulation controller

13‧‧‧Voltage controller

14‧‧‧Voltage feedback unit

15‧‧‧Virtual voltage drop computing unit

151‧‧‧First Operator

152‧‧‧Secondary

20A‧‧‧Voltage adjustment unit

21‧‧‧Voltage controller

22‧‧‧Operator

Claims (8)

A DC power supply parallel system includes a plurality of DC power supply modules, each of the DC power supply modules respectively has a power input end and a power output end, and each of the DC power supply modules respectively has its power input end and the power output end respectively Connected to form a parallel architecture; each DC power module includes: a power converter connected between the power input terminal and the power output terminal, the power converter has a control terminal; a pulse width modulation controller , having an input end and an output end, the output end of which is connected with the control end of the power converter; a voltage controller having two input ends and an output end, the output of the voltage controller and the pulse width modulation controller The input terminal is connected; a voltage feedback unit is connected between the power output end and an input end of the voltage controller; a virtual voltage drop operation unit has a feedback signal input end, a reference voltage input end, and an adjustment voltage input And a control signal output end, the feedback signal input end is connected to the power output end, and the control signal output end and the voltage controller are further connected The virtual voltage drop operation unit compares the feedback voltage of the power supply output with the reference voltage of the reference voltage input terminal to generate a control signal to the voltage controller to reduce the power converter through the pulse width modulation controller. The output voltage is a virtual voltage drop method; the DC power module further includes a voltage adjustment unit having a feedback voltage input terminal, a reference voltage input terminal, and an adjustment voltage output terminal. Voltage input and power output The adjustment voltage output terminal is connected to the adjustment voltage input terminal of the virtual voltage drop operation unit; the voltage adjustment unit generates an adjustment voltage according to the feedback voltage and a reference voltage to be sent to the virtual voltage drop operation unit. The DC power supply parallel system according to claim 1, wherein the virtual voltage drop operation unit has a first operator and a second operator, wherein the first and second operators respectively have two parameter ends and an output end, A parameter end of an arithmetic unit is connected to the power output end, and an output end thereof constitutes the aforementioned control signal output end, and is connected to another input end of the voltage controller, another parameter end of the first computing unit and the second computing unit The output ends are connected, and the two parameter ends of the second operator respectively constitute the aforementioned reference voltage input terminal and the adjustment voltage input terminal. The DC power supply parallel system according to claim 2, wherein the voltage adjusting unit comprises a voltage controller and an arithmetic unit, wherein the voltage controller has two input ends respectively connected to the power output end and the reference voltage input end; the voltage adjustment The unit of the unit has two parameter ends and an output end, and the output end is connected with the adjustment voltage input end of each DC power supply module, wherein one parameter end is connected with the output end of the voltage controller, and the other parameter end and the reference voltage input are connected. End connection. A parallel power supply system as claimed in claim 3, the voltage converter being an AC to DC converter. The DC power supply parallel system according to claim 3, wherein the voltage converter is a DC-to-DC converter. The DC power supply parallel system according to any one of claims 1 to 5, wherein each of the DC power supply modules is respectively provided with a voltage adjustment unit, and the adjustment voltage output ends of the respective voltage adjustment units respectively pass through a diode and all the DCs. The adjustment voltage output terminals of the adjustment unit are respectively connected through a diode and the adjustment voltage input terminal of the virtual voltage drop operation unit of all the DC power modules. A control method for a DC power supply parallel system includes: providing a plurality of DC power supply modules, and causing each of the DC power supply modules to be connected in parallel with each other with the power input end and the power output end; respectively, causing each of the DC power supply modules to perform a virtual voltage drop The method, the so-called virtual voltage drop method is to change the output voltage of the power supply output by the DC power supply module by changing the feedback signal of the power supply output, so that more than one DC power supply module performs constant voltage control. To adjust the output voltage at the output of the power supply. According to the control method of the DC power parallel system described in claim 7, each DC power module simulates different output impedances through a virtual voltage drop method, so that DC power modules of different capacities can be connected in parallel with each other.