CN103296675B - Parallel-connection direct-current power source load distribution circuit and control method thereof - Google Patents

Abstract

The invention belongs to the technical field of power electronics, and in particular relates to a parallel DC power supply load distribution circuit between power supplies when a plurality of DC switching power supplies are connected in parallel to supply power to loads and a control method for the circuit. Parallel DC power supply load distribution circuit, including reference current signal generation circuit, division circuit, bus signal generation circuit, first load distribution bus, second load distribution bus, current sensor, voltage sensor, A/D conversion circuit, central processing unit, Drive circuit and DC power supply main circuit. The invention can realize the control target of reasonably sharing the load according to the size of the capacity. According to the difference in the rated capacity of each DC power supply, the load current borne by each power supply can be reasonably distributed, so that the loading conditions of each power supply are basically the same, and the output current of the small-capacity power supply is too large and the output current of the large-capacity power supply is too small. situation arises, thereby effectively improving the operating efficiency, safety and reliability of DC power supplies operating in parallel.

Description

A parallel DC power supply load distribution circuit and its control method

technical field

The invention belongs to the technical field of power electronics, and in particular relates to a parallel DC power supply load distribution circuit between power supplies when a plurality of DC switching power supplies are connected in parallel to supply power to loads and a control method for the circuit.

Background technique

In the actual use of DC power supply (the DC power supply here and below refers specifically to the DC switching power supply), in order to meet the demand of output power, a scheme of parallel operation of multiple DC power supplies is often adopted. For multiple DC power supplies with the same capacity running in parallel, certain current sharing control measures must be taken to achieve an average distribution of load current, thereby improving the safety of each power supply operation. However, for the parallel operation of multiple DC power supplies with different capacities, there is no better control method to realize the reasonable distribution of load current among the various power supplies.

Contents of the invention

The purpose of the invention is to provide a parallel DC power supply load distribution circuit that can realize the distribution of load current among various power supplies according to the power supply capacity. The invention also provides a control method for the parallel DC power supply load distribution circuit.

The purpose of the present invention is achieved like this:

Parallel DC power supply load distribution circuit, including reference current signal generation circuit, division circuit, bus signal generation circuit, first load distribution bus, second load distribution bus, current sensor, voltage sensor, A/D conversion circuit, central processing unit, The drive circuit and the main circuit of the DC power supply, the output signal I _ref of the reference current signal generating circuit and the output current signal I _out of the DC power supply obtained by the current sensor detecting the main circuit of the DC power supply are used as two input signals of the division circuit, and the output signal of the division circuit is load factor k _L , where is the load current output by the DC power supply, I _N is the rated output current of the DC power supply, A is the amplification factor of the division circuit. The bus signal generation circuit takes the load factor k _L as the input signal, and sends the maximum load factor k _Lmax to the first load distribution bus, and the maximum load factor difference Δk _Lmax is sent to the second load distribution bus, Δk _L =B(k _Lmax -k _L ), B is the magnification of the operational amplifier circuit; the A/D conversion circuit collects the output current I _{out of} the current sensor, the maximum load factor k _Lmax on the first load distribution bus, and the second load The maximum load factor difference Δk _Lmax on the distribution bus, the load factor k _L of the division circuit, and the output voltage U _out obtained by the voltage sensor detecting the main circuit of the DC power supply are converted and sent to the central processing unit to generate a drive signal and sent to the drive circuit to control the DC The power supply main circuit regulates the distribution of power supply capacity.

The bus signal generation circuit consists of two diodes, an operational amplifier, and four resistors: the first resistor and the third resistor are respectively connected to the negative input terminal of the operational amplifier, and the second resistor and the fourth resistor are respectively connected to the positive input terminal of the operational amplifier. The other end of the first resistor is connected to the output end of the division circuit, the other end of the second resistor is connected to the cathode of the first diode, the other end of the third resistor is connected to the output end of the operational amplifier, and the other end of the fourth resistor One end is grounded; the positive pole of the first diode is connected to the output terminal of the division circuit, and the negative pole is connected to the first load distribution bus; the positive pole of the second diode is connected to the output terminal of the operational amplifier, and the negative pole is connected to the second load distribution bus.

The intermediate load factor control method of parallel DC power supply load distribution circuit, the central processing unit of each DC power supply uses the k _Lmax and Δk _Lmax signals to calculate the intermediate load factor k _Lmed , k _Lmed =k _Lmax -Δk _Lmax /2, the central processing The converter compares k _Lmed with the load factor k _L of its own power supply, if k _L is less than k _Lmed , then according to the difference between the two, increase the output voltage given signal of the DC power supply to increase the output voltage and increase the output current , and then the load factor k _L becomes larger until the difference between k _L and k _Lmed meets the error requirement; if k _L is greater than k _Lmed , then according to the difference between the two, reduce the output voltage given signal of the DC power supply, The output voltage is reduced, the output current is reduced, and then the load factor k _L is reduced until the difference between k _L and k _Lmed meets the error requirement.

The minimum load factor control method of the parallel DC power supply load distribution circuit calculates the current minimum load factor k _Lmin , k _Lmin =k _Lmax -Δk _Lmax , the central processing unit compares k _Lmin with the load factor k _L of its own power supply, if k _L is greater than k _Lmin , then according to the difference between the two, reduce the output voltage given signal of the DC power supply, so that the output voltage decreases, the output current decreases, and the load factor becomes smaller until the load factor k _L and the minimum load factor k _Lmin The difference meets the requirement of load distribution accuracy.

The maximum load factor control method of parallel DC power supply load distribution circuit, compare k _Lmax with the load factor k _L of its own power supply, if k _L is less than k _Lmax , then increase the output voltage given by the DC power supply according to the difference between the two signal, the output voltage increases, the output current increases, and the load factor increases until the difference between the load factor k _L of the power supply itself and the maximum load factor k _Lmax meets the load distribution accuracy requirements.

The beneficial effects of the present invention are:

Existing load distribution circuits aim at current sharing control on the premise of the same power supply capacity. Therefore, all these load distribution circuits provide information on the output current amplitude, which cannot be used to achieve different capacities. Load sharing control of DC power supplies running in parallel. However, the load distribution circuit of the present invention is designed for the parallel operation of DC power supplies with different capacities. Based on these information, the control objective of reasonably sharing the load according to the capacity can be finally realized. When a plurality of DC power supplies with different capacities are running in parallel, the load distribution circuit and control method proposed by the present invention can be used to rationally distribute the load current borne by each power supply according to the difference in the rated capacity of each DC power supply, so that each power supply The loading conditions of the DC power supplies are basically the same, avoiding the situation that the output current of the small-capacity power supply is too large and the output current of the large-capacity power supply is too small, thereby effectively improving the operating efficiency, safety and reliability of the DC power supplies operating in parallel.

The intermediate load coefficient control method proposed by the present invention can be realized by using a proportional integral link when using the difference between k _Lmed and k _L to adjust the given signal of the output voltage of the DC power supply, so that steady-state load distribution can be realized Control, that is, after the dynamic adjustment process of load distribution, if the power supply and load no longer change, each DC power supply will maintain the current load state and run stably without real-time adjustment. Therefore, this control method has the advantages of high load distribution accuracy and good effect.

The minimum load factor control method and the maximum load factor control method proposed by the present invention can only be realized by using the proportional link when adjusting the output voltage given signal of the DC power supply, so these two control methods can only realize dynamic load distribution Control requires that each DC power supply continuously adjusts the load distribution. But compared with the intermediate load factor control method, these two control methods are relatively simple and easy to implement.

Description of drawings

Figure 1 Structural diagram of load distribution circuit;

Fig. 2 The structure diagram of bus signal generating circuit.

Detailed ways

The present invention will be further described below in conjunction with accompanying drawing:

The DC power supply using the parallel DC power supply load distribution circuit and control method proposed by the present invention, when multiple power supplies are running in parallel, except that the outputs of the main circuits of these power supplies are connected in parallel to supply power to the load, at the same time the control circuits of all these DC power supplies They are also linked together through two common load distribution buses (namely, the first load distribution bus and the second load distribution bus below). Although the capacities of these DC power supplies operating in parallel are different, the load distribution circuits in their control circuits and the control methods for realizing load distribution are completely consistent, as described below.

The parallel DC power supply load distribution circuit proposed by the present invention is shown in Figure 1, and mainly includes a reference current signal generation circuit 1, a division circuit 2, a bus signal generation circuit 3, a first load distribution bus 4, and a second load distribution bus 5. In addition to the above specific circuits, it should also have a current sensor 6, a voltage sensor 7, an A/D conversion circuit 8, a central processing unit 9, a drive circuit 10 and a DC power main circuit 11 that are common to conventional DC power supply control circuits. The operating principle and analysis of the load distribution circuit proposed by the present invention are as follows:

The output signal of the reference current signal generating circuit 1 is I _ref , and the magnitude of I _ref is determined by formula (1).

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; ref</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

formula:

I _out is the DC power supply output current signal provided by the current sensor 6, that is, the load current output by the DC power supply converted by the current sensor 6;

_IL is the load current output by the DC power supply, i.e. the input current of the current sensor 6;

_IN is the rated output current of the DC power supply.

The reference current signal I _ref and the output current signal I _out provided by the current sensor 6 are respectively used as two input signals of the division circuit 2, and the output signal of the division circuit 2 is the load factor k _L whose magnitude is

${\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; A</span>}\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; out</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; ref</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In the formula, A is the magnification of the division circuit, and its size is determined by the specific parameters of the division circuit. An appropriate magnification A can improve the anti-interference ability and load distribution accuracy of the load distribution circuit. The magnification of the dividing circuit should be the same.

Substituting formula (1) into formula (2), we can get

${\mathrm{<span\; class="notranslate">\; k</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; A</span>}\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; L</span>}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; N</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

Formula (3) shows that when the magnification factor A of the dividing circuit remains unchanged, the load factor indicates the ratio of the load current output by the power supply to the rated current, that is, the load operation of the power supply.

The bus signal generating circuit takes the load factor k _L as an input signal, and its two outputs are respectively connected to the first load distribution bus 4 and the second load distribution bus 5 . The specific structure of the bus signal generation circuit is shown in Figure 2, which is composed of diodes D1, D2, operational amplifier A1, resistors R1, R2, R3, and R4: the operational amplifier A1 and resistors R1, R2, R3, and R4 are connected to form an amplifying circuit; the diode The positive pole of D1 is connected to the output of the division circuit 2, and at the same time connected to the negative input terminal of the operational amplifier A1 through the resistor R1, the negative pole of the diode D1 is connected to the first load distribution bus 4, and connected to the positive input terminal of the operational amplifier A1 through the resistor R2 ; The anode of the diode D2 is connected to the output of the operational amplifier A1, and the cathode of the diode D2 is connected to the second load distribution bus 5. The load factor signal k _L is sent to the first load distribution bus 4 through the diode D1, since all DC power supplies operating in parallel send their own load factor signals to the first load distribution bus 4 through the diode, using the one-way conduction characteristic of the diode It can be seen that only the power supply with the largest load factor can transmit its load factor to the first load distribution bus 4, so the signal on the first load distribution bus 4 is the maximum value of the load factors of all DC power supplies operating in parallel , namely the maximum load factor k _Lmax . Operational amplifier A1 and resistors R1, R2, R3, and R4 constitute an operational amplifier circuit. Its input signal is the voltage difference between the two ends of diode D1, and its output signal is the load factor difference Δk _L . The size of Δk _L is

Δk _L =B(k _Lmax -k _L ) (4)

In the formula, B is the magnification of the operational amplifier circuit, and its size is determined by the specific parameters of the resistor. The appropriate magnification B can improve the anti-interference ability and load distribution accuracy of the load distribution circuit. The corresponding operational amplifier circuits of all parallel operating DC power supplies The magnification should be the same. The load factor difference signal Δk _L is sent to the second load distribution bus 5 through the diode D2, since all DC power supplies operating in parallel send their own load factor difference signals to the second load distribution bus 5 through the diode, and the diode is used for one-way conduction It can be seen that only the power supply with the largest load factor difference can transmit its own load factor difference to the second load distribution bus 5, so the signal on the second load distribution bus 5 is the signal of all DC power supplies operating in parallel The maximum value of the load factor difference, that is, the maximum load factor difference Δk _Lmax .

The output current signal _Iout provided by the current sensor 6, the maximum load factor k _Lmax signal on the first load distribution bus 4, the maximum load factor difference Δk _Lmax signal on the second load distribution bus 5, the load factor k _L signal, and the voltage The output voltage signal U _out provided by the sensor 7 is sent to the central processing unit 9 after being converted by the A/D conversion circuit 8, and the central processing unit 9 uses this information to generate a driving signal according to a specific control method, and the driving signal passes through The driving circuit 10 controls the switching states of the power electronic devices in the main circuit 11 of the DC power supply, and then adjusts the magnitude of the output current, and finally realizes the adjustment goal of rationally distributing the load according to the power supply capacity.

The load distribution circuit proposed by the present invention has a unique reference current signal generation circuit, the output signal I _ref of the circuit is proportional to the rated output current I _N of the power supply itself, that is, the size of the I _ref reflects the capacity of the power supply Different, and then provide a reference for the rational distribution of load among multiple power sources with different capacities.

The load distribution circuit proposed by the present invention uses a division circuit to generate a load factor k _L , and the size of k _L directly reflects the proportional relationship between the actual output capacity of the power supply and its rated capacity. If the load of all power supplies operating in parallel can be The coefficients are equal, and the ideal load distribution control is realized. Therefore, the load factor k _L and its generating circuit proposed in the present invention provide credible criteria for the realization of load distribution.

The bus signal generation circuit in the load distribution circuit proposed by the present invention uses the load coefficient k _L of the power supply itself as an input signal, and finally forms different load distribution signals on two different load distribution buses. These two load distribution signals The formation of , provides the necessary calculation basis for the realization of the load distribution control method.

The load distribution circuit proposed by the present invention includes two load distribution buses, and these two load distribution buses can provide the maximum load factor k _Lmax and the maximum load factor difference Δk _Lmax signal for the power supply participating in the load distribution, based on these two signals , the power supply participating in the load distribution can adopt various control methods to realize the final load distribution.

Based on the load distribution circuit proposed by the present invention, different load distribution control methods can be formed, specifically including the following three control methods.

(1) Intermediate load factor control method.

The central processing unit 9 uses k _Lmax and Δk _Lmax signals to calculate an intermediate load coefficient k _Lmed , and the calculation formula of k _Lmed is

k _Lmed =k _Lmax -Δk _Lmax /2 (5)

The central processing unit 9 compares k _Lmed with the load factor k _L of its own power supply, if k _L is less than k _Lmed , then according to the difference between the two, increase the output voltage given signal of the DC power supply to increase the output voltage and output The current becomes larger, and the load factor k _L becomes larger until the difference between k _L and k _Lmed meets the error requirement. If k _L is greater than k _Lmed , then according to the difference between the two, reduce the output voltage given signal of the DC power supply, so that the output voltage decreases, the output current decreases, and the load factor k _L decreases until k _L and k _Lmed The difference between meet the error requirements. Since all DC power supplies will adjust their own output current according to the above method, the power supply with a large load factor will reduce the output current, and the power supply with a small load factor will increase the output current, so as the adjustment process continues, the second load distribution bus 5 The maximum load factor difference Δk _Lmax is getting smaller and smaller, and the load factor of each power supply will be more and more close to the maximum load factor k _Lmax on the first load distribution bus 4. When all the DC power supplies operating in parallel have completed load distribution After the dynamic adjustment process, the load factor of each DC power supply is approximately equal. According to the meaning of formula (3), at this time, the adjustment purpose of load current distribution according to the rated capacity of the power supply among all parallel running DC power supplies is realized.

Since all DC power supplies will adjust their own output current according to the above method, the power supply with a large load factor will reduce the output current, and the power supply with a small load factor will increase the output current, so as the adjustment process continues, the second load distribution bus The maximum load factor difference Δk _Lmax is getting smaller and smaller, and the load factor of each power supply will be more and more close to the maximum load factor k _Lmax on the first load distribution bus. When all DC power supplies running in parallel complete the load distribution dynamic After the adjustment process, the load factor of each DC power supply is approximately equal, that is, the adjustment purpose of load current distribution according to the rated capacity of the power supply among all parallel running DC power supplies is realized

In this control method, the difference between k _Lmed and k _L can be positive or negative, so the proportional integral link can be used to calculate the adjustment value of the output voltage given signal according to the difference between k _Lmed and k _L. Since the load distribution control is realized by the proportional integral link, this control method can realize steady-state load distribution, that is, when all DC power supplies operating in parallel have completed the dynamic adjustment process of load distribution, if the load and power supply no longer change , the current load distribution status of each DC power supply will always be maintained without real-time adjustment.

(2) Minimum load factor control method.

The central processing unit 9 calculates the current minimum load factor k _Lmin by using the k _Lmax and Δk _Lmax signals, and the calculation formula of k _Lmin is

k _Lmin =k _Lmax -Δk _Lmax (6)

The central processing unit 9 compares k _Lmin with the load factor k _L of its own power supply, if k _L is greater than k _Lmin , then according to the difference between the two, reduce the output voltage given signal of the DC power supply, so that the output voltage is reduced, and the output The current decreases and the load factor becomes smaller. Since all DC power supplies, except the DC power supply whose load factor is equal to k _Lmin (the adjustment value of the given signal of the output voltage of the power supply is zero), will adjust the size of their own output current according to the above method, so as the adjustment process continues , the load factor of each power supply will be closer to the minimum load factor k _Lmin , when the difference between the load factor k _L of the power supply itself and the minimum load factor k _Lmin meets the load distribution accuracy requirements, the power supply will complete the load distribution adjust.

Since all DC power supplies, except the DC power supply whose load factor is equal to k _Lmin (the adjustment value of the given signal of the output voltage of the power supply is zero), will adjust the size of their own output current according to the above method, so as the adjustment process continues , the load factor of each power supply will be closer to the minimum load factor k _Lmin , when the difference between the load factor k _L of the power supply itself and the minimum load factor k _Lmin meets the load distribution accuracy requirements, the power supply will complete the load distribution adjust.

In this control method, k _Lmin is always less than or equal to k _L , so the proportional link can only be used to calculate the adjustment value of the output voltage given signal according to the difference between k _Lmin and k _L. Since the load distribution control is realized by using a proportional link, this control method can only realize dynamic load distribution, that is, each DC power supply is always in the dynamic process of constant adjustment of load distribution during operation, and cannot achieve steady-state load distribution. distribute.

(3) Maximum load factor control method.

In this control method, the central processing unit 9 only needs to use the maximum load coefficient k _Lmax signal on the first load distribution bus 4 . The central processing unit 9 compares k _Lmax with the load factor k _L of its own power supply, if k _L is less than k _Lmax , then according to the difference between the two, increase the output voltage given signal of the DC power supply to increase the output voltage and output The larger the current, the larger the load factor. Since all DC power supplies, except the DC power supply whose load factor is equal to k _Lmax (the adjustment value of the output voltage given signal of the power supply is zero), will adjust their own output current according to the above method, so as the adjustment process continues , the load factor of each power supply will be closer to the maximum load factor k _Lmax on the first load distribution bus 4, when the difference between the load factor k _L of the power supply itself and the maximum load factor k _Lmax meets the load distribution accuracy requirements , the power supply completes the load distribution regulation.

Since all DC power supplies, except the DC power supply whose load factor is equal to k _Lmax (the adjustment value of the output voltage given signal of the power supply is zero), will adjust their own output current according to the above method, so as the adjustment process continues , the load factor of each power supply will be closer to the maximum load factor k _Lmax on the first load distribution bus, when the difference between the load factor k _L of the power supply itself and the maximum load factor k _Lmax meets the load distribution accuracy requirements , then the power supply completes the load distribution regulation.

In this control method, k _Lmax is always greater than or equal to k _L , so the proportional link can only be used to calculate the adjustment value of the output voltage given signal according to the difference between k _Lmax and k _L. Since the load distribution control is realized by using a proportional link, this control method can only realize dynamic load distribution, that is, each DC power supply is always in the dynamic process of constant adjustment of load distribution during operation, and cannot achieve steady-state load distribution. distribute.

The above three control methods are to adjust the output voltage given signal in the DC power supply control according to the current load distribution state, and then use the output voltage signal U _out provided by the voltage sensor 7 to adjust the output voltage given signal and the output current signal I _out provided by the current sensor 6 form a voltage closed loop or voltage and current double closed loop control, and finally realize the regulation of the load current output by the DC power supply.

In the dynamic process of load distribution adjustment using the above three control algorithms, the load coefficient k _L of each DC power supply, the maximum load coefficient k _Lmax on the first load distribution bus 4, and the maximum load on the second load distribution bus 5 The coefficient difference Δk _Lmax changes in real time, so the A/D conversion circuit 8 is required to have a higher conversion frequency and precision, and the central processing unit 9 is required to have real-time and fast data processing capabilities.

When the load distribution circuit and the minimum load factor control method proposed by the present invention are adopted, through specific control operations, flexible decoupling and flexible parallel control between DC power supplies operating in parallel can also be realized, that is, when the DC power supplies exit or join parallel operation During the process, there is no inrush current in all the main circuits of the DC power supply, or the inrush current is very small and can be controlled within the allowable value range. The specific implementation method is as follows:

(1) Flexible disassembly control method. If a certain power supply wants to exit the parallel operation, the connection between the load distribution circuit of the power supply and the first load distribution bus 4 is disconnected first. At this time, the k _Lmax signal sent to the A/D conversion circuit of the power supply is actually the load factor k _L of the power supply itself, and the maximum load factor difference Δk _Lmax on the second load distribution bus 5 is not zero, according to the minimum load factor The principle of the control method shows that the power supply will continuously reduce its output current, and its load factor k _L will also continue to decrease, while the output current of other normally working DC power supplies will gradually increase, that is, it will bear the burden of the DC power supply that is about to quit operation. When the output current of the DC power supply that is about to quit operation is reduced to zero or reaches the allowable value range, then disconnect the electrical connection between the main circuit of the DC power supply and other main circuits of the DC power supply. The output current of the DC power supply to be exited is already very small, so in the process of disconnecting the main circuit, no inrush current will be brought to other DC power supplies, or the inrush current can be controlled within the allowable range. Finally, the connection between the load distribution circuit of the DC power supply and the second load distribution bus 5 is disconnected to complete the flexible decoupling control.

(2) Flexible parallel control method. If a certain DC power supply is to be added for parallel operation (this power supply is called a standby power supply), firstly connect the load distribution circuit of the standby power supply to the second load distribution bus 5 . At this time, the maximum load factor difference Δk _Lmax on the second load distribution bus 5 is not zero, and the specific size is determined by the DC power supplies currently running in parallel. The k _Lmax signal collected by the A/D conversion circuit of the parallel power supplies is actually Its own load factor k _L , since the power supply to be paralleled is in the no-load state, the value of its output current signal I _out and the load factor k _L are both zero. According to the principle of the minimum load factor control method, the central processing of the power supply to be paralleled The minimum load factor k _Lmin calculated by the controller is less than zero. Under this condition, the central processing unit blocks the driving signal, and the power electronic switching device in the main circuit 11 of the DC power supply is in a cut-off state. At this time, the main circuit 11 of the DC power supply to be paralleled is connected with the main circuits of other parallel operating DC power supplies. Since the power electronic devices in the main circuit 11 of the DC power supply to be paralleled are in an off state, the main circuits connected to the main circuit There will be no inrush current during the process. After completing the connection of the main circuit of the power supply to be paralleled, its load distribution circuit is connected to the first load distribution bus 4, and the power supply to be paralleled is based on the signals on the first load distribution bus 4 and the second load distribution bus 5, Adjust its own output current, and finally complete the parallel access process.

The present invention is characterized in that

(1) When multiple DC power supplies with different capacities are running in parallel, the load distribution circuit and control method proposed by the present invention can be used to rationally distribute the load current borne by each power supply according to the difference in the rated capacity of each DC power supply, so that The loading conditions of each power supply are basically the same, avoiding the situation that the output current of the small-capacity power supply is too large and the output current of the large-capacity power supply is too small, thereby effectively improving the operating efficiency, safety and reliability of the DC power supplies operating in parallel.

(2) The intermediate load factor control method proposed by the present invention can be realized by using a proportional integral link when using the difference between k _Lmed and k _L to adjust the given signal of the output voltage of the DC power supply, so that the steady state can be realized Load distribution control, that is, after the dynamic adjustment process of load distribution, if the power supply and load no longer change, each DC power supply will maintain the current load state and run stably, and no real-time adjustment is required. Therefore, this control method has the advantages of high load distribution accuracy and good effect.

(3) The minimum load factor control method and the maximum load factor control method proposed by the present invention can only be realized by using the proportional link when adjusting the output voltage given signal of the DC power supply, so these two control methods can only realize dynamic The load distribution control of the system requires each DC power supply to adjust the load distribution continuously. But compared with the intermediate load factor control method, these two control methods are relatively simple and easy to implement.

(4) The load distribution circuit and control method proposed by the present invention have good fault tolerance. When some faults occur in the load sharing circuit, the DC power supply can still achieve load sharing regulation, for example:

Fault 1, the second load distribution bus 5 is short-circuited to ground. In this fault situation, the maximum load factor difference Δk _Lmax on the second load sharing busbar 5 is zero. If the intermediate load factor control method or the minimum load factor control method is adopted, after a fault occurs, according to the principles of these two control methods, when Δk _Lmax = 0, these two control methods automatically transform into the maximum load factor control method , so all DC sources operating in parallel can still achieve load sharing regulation.

Fault 2, the connection between a load distribution circuit of a DC power supply and the second load distribution bus 5 is disconnected. In such a fault situation, in the load distribution circuit of the faulty DC power supply, the Δk _Lmax signal sent to the A/D conversion circuit actually reflects the difference between the maximum load factor k _Lmax signal and the power supply’s own load factor k _L If the intermediate load factor control method or the maximum load factor control method is adopted, after the fault occurs, the fault power supply will still continue to carry out load distribution adjustment, and will not have adverse effects on other parallel DC power supplies.

(5) When the load distribution circuit and the minimum load factor control method proposed by the present invention are adopted, in the process of paralleling and decoupling of DC power supplies, through specific control operations, the generation of inrush current in the main circuit of the power supply can be effectively suppressed, and further Improve the safety and reliability of DC power supply operation.

The first embodiment of the parallel DC power supply load distribution circuit of the present invention is:

Several DC power supplies operate in parallel, and the control circuit sections of all these power supplies are connected together through two different load sharing buses.

In addition to the hardware circuit structure of the load distribution circuit, it includes the main circuit of the DC power supply, the central processing unit, the drive circuit, the A/D conversion circuit, the current sensor, the voltage sensor, and also has its unique reference current signal generation circuit, division circuit, Bus signal generating circuit, first load distribution bus, second load distribution bus, etc.

The main circuit of the DC power supply can adopt various existing DC switching power supply circuits, such as Buck circuit, Boost circuit, Buck-Boost circuit and the like.

The current sensor can adopt various existing current sensors, such as Hall-type current sensors.

The voltage sensor can adopt various existing voltage sensors, such as Hall-type voltage sensors.

The A/D conversion circuit can be composed of an existing A/D conversion chip supplemented by an input limiter circuit and a filter circuit, or it can directly use some internal A/D conversion circuits of some central processing units.

The central processing unit can adopt digital signal processors (DSP), single-chip microcomputers, computers and other devices and devices with digital signal processing and computing functions.

The driving circuit can adopt the existing various circuits that can convert the level signal output by the central processing unit into the driving signal of the power electronic device.

The first load distribution busbar and the second load distribution busbar adopt cables with shielding layers.

The division circuit can be selected from various existing circuits that can realize the division function, but the magnifications of the division circuits of all parallel operating DC power supplies should be the same.

The reference current signal generation circuit can use the combination of DC power supply and voltage divider resistor, and through the reasonable selection of DC power supply voltage value and voltage divider resistor value, the output signal of the circuit can meet the requirements of formula (1).

Combined with Figure 2, the bus signal generation circuit is composed of diodes D1, D2, operational amplifier A1, resistors R1, R2, R3, and R4: the operational amplifier A1 and resistors R1, R2, R3, and R4 are connected to form an amplifying circuit; the anode of diode D1 is connected to The output of the division circuit is connected to the negative input terminal of the operational amplifier A1 through the resistor R1 at the same time, the negative pole of the diode D1 is connected to the first load distribution bus, and connected to the positive input terminal of the operational amplifier A1 through the resistor R2 at the same time; the positive pole of the diode D2 is connected to the operational amplifier A1 The output of the amplifier A1 and the cathode of the diode D2 are connected to the second load sharing bus. Diodes D1 and D2 use diodes with small forward conduction voltage drop; operational amplifier A1 can use various integrated operational amplifier chips; resistors R1, R2, R3, and R4 use high-precision resistors, and the resistance value is based on the design value of the operational amplification factor to be chosen, but this magnification should be the same for all DC power supplies operating in parallel.

For the load distribution control method, choose any one of the intermediate load factor control method, the minimum load factor control method, and the maximum load factor control method, but all DC power supplies operating in parallel should use the same control method.

The second implementation mode of the parallel DC power supply load distribution circuit of the present invention is:

The existing circuit with unidirectional conduction and no conduction voltage drop is used to replace the diode in the bus signal generating circuit.

Others are the same as the above embodiment.

The third implementation mode of the parallel DC power supply load distribution circuit of the present invention is:

The reference current signal generating circuit is composed of a central processing unit and a D/A conversion circuit, and the central processing unit controls the D/A conversion circuit to output the required reference current signal.

Others are the same as the above embodiment.

The first embodiment of the load distribution control method based on the parallel DC power supply load distribution circuit of the present invention is an intermediate load factor control method.

The central processing unit 9 uses k _Lmax and Δk _Lmax signals to calculate an intermediate load coefficient k _Lmed , k _Lmed = k _Lmax - Δk _Lmax /2. The central processing unit 9 compares k _Lmed with the load factor k _L of its own power supply, if k _L is less than k _Lmed , then according to the difference between the two, increase the output voltage given signal of the DC power supply to increase the output voltage and output The current becomes larger, and the load factor k _L becomes larger until the difference between k _L and k _Lmed meets the error requirement. If k _L is greater than k _Lmed , then according to the difference between the two, reduce the output voltage given signal of the DC power supply, so that the output voltage decreases, the output current decreases, and the load factor k _L decreases until k _L and k _Lmed The difference between meet the error requirements. Since all DC power supplies will adjust their own output current according to the above method, the power supply with a large load factor will reduce the output current, and the power supply with a small load factor will increase the output current, so as the adjustment process continues, the second load distribution bus 5 The maximum load factor difference Δk _Lmax is getting smaller and smaller, and the load factor of each power supply will be more and more close to the maximum load factor k _Lmax on the first load distribution bus 4. When all the DC power supplies operating in parallel have completed load distribution After the dynamic adjustment process, the load factor of each DC power supply is approximately equal. According to the meaning of formula (3), at this time, the adjustment purpose of load current distribution according to the rated capacity of the power supply among all parallel running DC power supplies is realized.

In this control method, the difference between k _Lmed and k _L can be positive or negative, so the proportional integral link can be used to calculate the adjustment value of the output voltage given signal according to the difference between k _Lmed and k _L. Since the load distribution control is realized by the proportional integral link, this control method can realize steady-state load distribution, that is, when all DC power supplies operating in parallel have completed the dynamic adjustment process of load distribution, if the load and power supply no longer change , the current load distribution status of each DC power supply will always be maintained without real-time adjustment.

The second embodiment of the load distribution control method based on the parallel DC power supply load distribution circuit of the present invention is a minimum load factor control method.

The central processing unit 9 uses the k _Lmax and Δk _Lmax signals to calculate the current minimum load factor k _Lmin , k _Lmin =k _Lmax -Δk _Lmax . The central processing unit 9 compares k _Lmin with the load factor k _L of its own power supply, if k _L is greater than k _Lmin , then according to the difference between the two, reduce the output voltage given signal of the DC power supply, so that the output voltage is reduced, and the output The current decreases and the load factor becomes smaller. Since all DC power supplies, except the DC power supply whose load factor is equal to k _Lmin (the adjustment value of the given signal of the output voltage of the power supply is zero), will adjust the size of their own output current according to the above method, so as the adjustment process continues , the load factor of each power supply will be closer to the minimum load factor k _Lmin , when the difference between the load factor k _L of the power supply itself and the minimum load factor k _Lmin meets the load distribution accuracy requirements, the power supply will complete the load distribution adjust.

In this control method, k _Lmin is always less than or equal to k _L , so the proportional link can only be used to calculate the adjustment value of the output voltage given signal according to the difference between k _Lmin and k _L. Since the load distribution control is realized by using a proportional link, this control method can only realize dynamic load distribution, that is, each DC power supply is always in the dynamic process of constant adjustment of load distribution during operation, and cannot achieve steady-state load distribution. distribute.

The third embodiment of the load distribution control method based on the parallel DC power supply load distribution circuit of the present invention is a maximum load factor control method.

In this control method, the central processing unit 9 only needs to use the maximum load coefficient k _Lmax signal on the first load distribution bus 4 . The central processing unit 9 compares k _Lmax with the load factor k _L of its own power supply, if k _L is less than k _Lmax , then according to the difference between the two, increase the output voltage given signal of the DC power supply to increase the output voltage and output The larger the current, the larger the load factor. Since all DC power supplies, except the DC power supply whose load factor is equal to k _Lmax (the adjustment value of the output voltage given signal of the power supply is zero), will adjust their own output current according to the above method, so as the adjustment process continues , the load factor of each power supply will be closer to the maximum load factor k _Lmax on the first load distribution bus 4, when the difference between the load factor k _L of the power supply itself and the maximum load factor k _Lmax meets the load distribution accuracy requirements , the power supply completes the load distribution regulation.

In this control method, k _Lmax is always greater than or equal to k _L , so the proportional link can only be used to calculate the adjustment value of the output voltage given signal according to the difference between k _Lmax and k _L. Since the load distribution control is realized by using a proportional link, this control method can only realize dynamic load distribution, that is, each DC power supply is always in the dynamic process of constant adjustment of load distribution during operation, and cannot achieve steady-state load distribution. distribute.

Claims (5)

1. a parallel-connection direct-current power source load distribution circuit, comprise reference current signal generative circuit (1), division circuit (2), bus signal generating circuit (3), the first sharing of load bus (4), the second sharing of load bus (5), current sensor (6), voltage sensor (7), A/D change-over circuit (8), central processing unit (9), drive circuit (10) and DC power supply main circuit (11), is characterized in that: the output signal I of reference current signal generative circuit _refwith the DC power supply output current signal I that current sensor detection DC power supply main circuit obtains _outas the two-way input signal of division circuit, the output signal of division circuit is load coefficient k _l, wherein i _lfor the load current that DC power supply exports, I _nfor the output-current rating of DC power supply, a is the multiplication factor of division circuit, and bus signal generating circuit is with load coefficient k _lfor input signal, by peak load coefficient k _lmaxdeliver to the first sharing of load bus, peak load coefficient difference Δ k _lmaxdeliver to the second sharing of load bus, Δ k _lmax=B (k _lmax-k _l), B is the multiplication factor of operational amplification circuit; A/D change-over circuit gathers the output current I of current sensor _out, peak load coefficient k on the first sharing of load bus _lmax, peak load coefficient difference Δ k on the second sharing of load bus _lmax, division circuit load coefficient k _l, the output voltage U that obtains of voltage sensor senses DC power supply main circuit _outcarry out changing and send into central processing unit and generate drive singal and send to drive circuit to control the distribution of DC power supply main circuit adjustment power supply capacity.

2. a kind of parallel-connection direct-current power source load distribution circuit according to claim 1, it is characterized in that: described bus signal generating circuit is by two diodes, an operational amplifier (A1), four resistance are formed: the first resistance (R1), 3rd resistance (R3) is connected with the negative input end of operational amplifier respectively, second resistance (R2), 4th resistance (R4) is connected with the positive input terminal of operational amplifier respectively, the other end of the first resistance is connected with division circuit output, the other end of the second resistance is connected with the negative pole of the first diode (D1), the other end of the 3rd resistance is connected with the output of operational amplifier, the other end ground connection of the 4th resistance, the positive pole of the first diode connects the output of division circuit, and negative pole is connected to the first sharing of load bus, the positive pole of the second diode (D2) connects the output of operational amplifier, and negative pole is connected to the second sharing of load bus.

3. the shoulder load coefficient control method of a kind of parallel-connection direct-current power source load distribution circuit according to claim 1, is characterized in that: the central processing unit of each DC power supply utilizes k _lmaxwith Δ k _lmaxsignal, calculates shoulder load coefficient k _lmed, k _lmed=k _lmax-Δ k _lmax/ 2, central processing unit is by k _lmedwith the load coefficient k of own power source _lmake comparisons, if k _lbe less than k _lmed, then according to the difference of the two, increase the output voltage Setting signal of DC power supply, output voltage is raised, output current becomes large, and then load coefficient k _lbecome large, until k _lwith k _lmedbetween difference meet error requirements; If k _lbe greater than k _lmed, then according to the difference of the two, reduce the output voltage Setting signal of DC power supply, output voltage is reduced, output current reduces, and then reduces load coefficient k _l, until k _lwith k _lmedbetween difference meet error requirements.

4. the minimum load coefficient control method of a kind of parallel-connection direct-current power source load distribution circuit according to claim 1, is characterized in that: calculate current minimum load coefficient k _lmin, k _lmin=k _lmax-Δ k _lmax, central processing unit is by k _lminwith the load coefficient k of own power source _lmake comparisons, if k _lbe greater than k _lmin, then according to the difference of the two, reduce the output voltage Setting signal of DC power supply, output voltage is reduced, output current reduces, and load coefficient diminishes until load coefficient k _lwith minimum load coefficient k _lmindifference meet sharing of load required precision.

5. the peak load coefficient control method of a kind of parallel-connection direct-current power source load distribution circuit according to claim 1, is characterized in that: by k _lmaxwith the load coefficient k of own power source _lmake comparisons, if k _lbe less than k _lmax, then according to the difference of the two, increase the output voltage Setting signal of DC power supply, output voltage is raised, output current becomes large, and load coefficient becomes large, until the load coefficient k of power supply self _lwith peak load coefficient k _lmaxdifference meet sharing of load required precision.