Control method for automatic power distribution of multi-input DC-DC converter

Abstract

The invention discloses a control method for automatic power distribution of a multi-input DC-DC converter. A plurality of single-path four-switch Buck-Boost buck-boost circuits form a multi-input DC-DC converter circuit; calculating average input power; adjusting the output power of each input circuit; calculating a power distribution loop operation result of a circuit in a constant-voltage or constant-current output state, superposing the power distribution loop operation result on a target value of an effective loop of the circuit, and transmitting an output result of the effective loop to a current inner loop so as to determine the duty ratio of the circuit; the circuit in the MPPT maximum power tracking state runs a maximum power tracking algorithm and outputs the maximum output power which can be provided by the photovoltaic panel of the circuit; and if the output state of each single-path four-switch Buck-Boost circuit is switched, the power is equally divided again.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of new energy control technology, and particularly relates to a control method for power automatic distribution of a multi-input DC-DC converter. BACKGROUND

[0002] With the increasingly serious energy crisis and environmental problems, the development and utilization of new energy has become an inevitable trend. Combining various forms of new energy and energy storage devices to form a new energy combined power supply system can realize efficient utilization of new energy and obtain stable power output.

[0003] However, in the new energy combined power supply system, each new energy generation unit and energy storage unit needs an independent DC-DC converter to convert the electrical energy converted by each energy into a direct current output and be connected in parallel to the common DC bus end. In order to integrate the system topology and control structure, a multi-input DC-DC converter is used to replace multiple individual DC-DC converters, which not only can simplify the structure of the new energy combined power supply system, but also can reduce the system operation cost. For example, in the photovoltaic system application scenario, a multi-input DC-DC converter can be used to replace multiple individual DC-DC converters, and the effect of each photovoltaic panel being equipped with a power electronic converter for realizing maximum power tracking can still be realized, so that each photovoltaic panel can output maximum power, thereby realizing efficient operation of the photovoltaic system. However, in the parallel system, the current between the modules is easy to appear uneven, so it is necessary to take appropriate measures to realize power distribution between the modules. SUMMARY

[0004] Therefore, it is necessary to provide a control method for power automatic distribution of a multi-input DC-DC converter for simplifying the structure of a new energy combined power supply system.

[0005] A control method for power automatic distribution of a multi-input DC-DC converter, the method comprising the following steps: Step one, circuit configuration; a plurality of single four-switch Buck-Boost step-up and step-down circuits are combined to form a multi-input DC-DC converter circuit; the input end of each single four-switch Buck-Boost step-up and step-down circuit is connected to an independent photovoltaic panel output circuit; Step two, calculating average input power; the number of all circuits in a constant voltage or constant current output state and the total input power of all circuits are counted, and the total input power is divided by the number of circuits to obtain the average input power; Step three, adjust the input power of each input circuit; calculate the power distribution loop operation result of the specific circuit in constant voltage or constant current output state, superimpose the power distribution loop operation result on the target value of the effective loop of the specific circuit, and transmit the output result of the effective loop to the current inner loop to determine the duty cycle of the specific circuit; Step four, the circuit in MPPT maximum power tracking state runs the maximum power tracking algorithm, and outputs the maximum output power that the photovoltaic panel can provide. Step five, if the output state of each single four-switch Buck-Boost step-up / down circuit switches, go to step two.

[0006] Preferably, each single four-switch Buck-Boost step-up / down circuit comprises an output voltage loop VoutLoop, an output current loop IoutLoop, an input voltage loop VinLoop, a current inner loop IcsLoop, and a power sharing loop PinShareLoop.

[0007] Preferably, the specific steps of calculating the average input power in step two include: Step 2.1, determine whether each four-switch Buck-Boost step-up / down circuit is in output voltage loop or output current loop running state; Step 2.2, count the number of circuits in constant voltage or constant current output state; Step 2.3, count the total input power of all circuits in constant voltage or constant current output state; Step 2.4, divide the total input power by the number of circuits in constant voltage or constant current output state to obtain the average input power.

[0008] Preferably, the specific steps of adjusting the input power of each input circuit in step three include: Step 3.1, take the average input power as the target value, take the input power of the circuit as the feedback value, and perform power distribution loop operation on the single four-switch Buck-Boost step-up / down circuit of the circuit to obtain the power distribution loop operation result; Step 3.2, superimpose the power distribution loop operation result on the target value of the effective loop of the circuit in constant voltage or constant current output state, and obtain the effective loop operation result through effective loop calculation; Step 3.3, input the effective loop operation result to the current inner loop, and output to the PWM circuit after current inner loop operation to obtain the adjusted duty cycle.

[0009] Preferably, the output power of the circuit in the MPPT maximum power tracking state in step four depends on the maximum power tracking algorithm and the characteristics of the photovoltaic panel itself, and does not participate in the power sharing process.

[0010] Preferably, the specific steps after the output state of each single four-switch Buck-Boost boost-buck circuit in step five is switched include: Step 5.1, after the circuit in the MPPT maximum power tracking state is switched from the MPPT tracking state to the constant voltage or constant current output state, the number of circuits participating in power sharing is increased, the system repeats steps two and three, and the power sharing among circuits is re-performed; Step 5.2, after the circuit in the constant voltage or constant current output state is switched from the constant voltage or constant current output state to the MPPT tracking state, the number of circuits participating in power sharing is reduced, the system repeats steps two and three, and the power sharing among circuits is re-performed.

[0011] In the above-mentioned control method for power automatic distribution of the multi-input DC-DC converter, the average input power of all circuits in the constant voltage or constant current output state is calculated, the input power of each input circuit is adjusted, under the action of the power sharing loop, the power of the circuit with large power is reduced, and the power of the circuit with small power is increased, so that the power of all circuits in the constant voltage or constant current output state is finally shared. Since the efficiency of the single four-switch Buck-Boost boost-buck circuit of each circuit is different, the power distribution in the technical solution adjusts the input power of each circuit to balance the output power of each circuit. In the application of new energy power generation, the power balance capability supports the coordinated management of energy of different input sources, realizes efficient power transmission and multi-energy complementation, and improves the system energy utilization rate. The method of the present application is simple, easy to implement, low in cost, and convenient to popularize. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is a circuit schematic diagram of the single four-switch Buck-Boost boost-buck circuit of the embodiment of the present application.

[0013] Figure 2 is a circuit structure schematic diagram of the multi-input DC-DC converter of the embodiment of the present application.

[0014] Figure 3 is a power distribution control schematic diagram of the control method for power automatic distribution of the multi-input DC-DC converter of the embodiment of the present application.

[0015] Figure 4 is a flowchart of the control method for power automatic distribution of the multi-input DC-DC converter of the embodiment of the present application. DETAILED DESCRIPTION

[0016] The embodiment takes the control method of power automatic distribution of multi-input DC-DC converter as an example, and the application will be described in detail in combination with specific embodiments and drawings.

[0017] Please refer to Figure 4 , which shows a control method of power automatic distribution of multi-input DC-DC converter provided by the embodiment of the application, and the method comprises the following steps: Step S10, circuit configuration; a plurality of single-channel four-switch Buck-Boost step-up / down circuits are combined to form a multi-input DC-DC converter circuit.

[0018] Preferably, the multi-input DC-DC converter circuit in step one comprises a plurality of single-channel four-switch Buck-Boost step-up / down circuits, and the input end of each single-channel four-switch Buck-Boost step-up / down circuit is independently arranged, and the output ends of the plurality of single-channel four-switch Buck-Boost step-up / down circuits are connected in parallel to the Vout output end.

[0019] Specifically, as shown in Figure 1 , the single-channel four-switch Buck-Boost step-up / down circuit comprises an input-side half-bridge, an output-side half-bridge and an inductor L1, the inductor L1 is connected to the middle node between the input-side half-bridge and the output-side half-bridge, and is used for energy transmission between the input side and the output side.

[0020] Specifically, as shown in Figure 2 , in the embodiment, four single-channel four-switch Buck-Boost step-up / down circuits are arranged side by side, the input ends of the four single-channel four-switch Buck-Boost step-up / down circuits are independently arranged, the output ends of the four single-channel four-switch Buck-Boost step-up / down circuits are connected in parallel to the Vout output end, and the Vout output end is provided with a load RL.

[0021] Specifically, the control mode of power distribution in the technical solution is not only applicable to the Buck-Boost step-up / down circuit, but also can be extended to other circuits.

[0022] Preferably, the input end of each single-channel four-switch Buck-Boost step-up / down circuit is connected to an independent photovoltaic panel output circuit; each single-channel four-switch Buck-Boost step-up / down circuit comprises an output voltage loop VoutLoop, an output current loop IoutLoop, an input voltage loop VinLoop, a current inner loop IcsLoop and a power sharing loop PinShareLoop.

[0023] Specifically, the output voltage loop VoutLoop is used for constant voltage output, the output current loop IoutLoop is used for constant current output, the input voltage loop VinLoop is used for MPPT tracking, the power sharing loop PinShareLoop is used for realizing power sharing, and the current inner loop IcsLoop finally outputs to the duty cycle.

[0024] In step S20, the average input power is calculated. Please refer to Figure 3 The average input power is calculated by dividing the total input power of all circuits in the constant voltage or constant current output state by the number of circuits.

[0025] The specific steps include: In step S21, it is determined whether each four-switch Buck-Boost step-down and step-up circuit is in an output voltage loop or an output current loop operating state.

[0026] In step S22, the number of all circuits in the constant voltage or constant current output state is counted.

[0027] In step S23, the total input power of all circuits in the constant voltage or constant current output state is counted.

[0028] In step S24, the average input power is calculated by dividing the total input power of all circuits in the constant voltage or constant current output state by the number of circuits.

[0029] In step S30, the input power of each input circuit is adjusted. The power sharing loop calculation result of a specific circuit in the constant voltage or constant current output state is calculated, the power sharing loop calculation result is superimposed on the target value of the effective loop of the specific circuit, and the output result of the effective loop is transmitted to the current inner loop to determine the duty cycle of the specific circuit.

[0030] The specific steps include: In step S31, the average input power is used as the target value, the input power of the circuit is used as the feedback value, the power sharing loop calculation of the single four-switch Buck-Boost step-down and step-up circuit of the circuit is performed, and the power sharing loop calculation result is obtained.

[0031] Specifically, the target value of the power sharing loop calculation is the average input power, the feedback value is the input power of the circuit, a conventional PI controller is used for calculation, the power sharing loop calculation result is obtained, and the specific calculation steps are as follows: The power sharing loop error value = target value - feedback value, The target value is the average input power of all circuits in the constant voltage or constant current output state.

[0032] Specifically, the power distribution loop operation result is an adjustment component of the target value of the output voltage loop and the output current loop, and represents the adjustment capability of the output voltage or the output current.

[0033] In step S32, the power distribution loop operation result is superimposed on the target value of the effective loop of the circuit in the constant voltage or constant current output state, and the effective loop calculation is performed to obtain an effective loop operation result.

[0034] Specifically, if the single-channel four-switch Buck-Boost step-down / step-up circuit is in constant voltage output, and the effective loop is an output voltage loop, the power distribution loop operation result is superimposed on the target value of the output voltage loop; if the single-channel four-switch Buck-Boost step-down / step-up circuit is in constant current output, and the effective loop is an output current loop, the power distribution loop operation result is superimposed on the target value of the output current loop.

[0035] Specifically, the effective loop calculation of the circuit in the constant voltage or constant current output state includes output voltage loop operation and output current loop operation, and the operation steps are as follows: In step S32.1, the power distribution loop operation result is superimposed on the output voltage loop, and the calculation process of the output voltage loop result using a PI controller is as follows: Output voltage loop error value = actual output voltage target value - feedback value; wherein the actual output voltage target value = current output voltage target value + power distribution loop operation result; In step S32.2, the power distribution loop operation result is superimposed on the output current loop, and the calculation process of the output current loop result using a PI controller is as follows: Output current loop error value = actual output current target value - feedback value, wherein the actual output current target value = current output current target value + power distribution loop operation result; In step S32.3, the calculation process of the input voltage loop result using a PI controller is as follows: Input voltage loop error value = feedback value - input voltage loop target value, wherein the input voltage loop target value is the actual input voltage of the circuit in the MPPT maximum power tracking state; In step S32.3, the minimum value of all output voltage loop operation results, all output current loop operation results, and all circuit operation results in the MPPT maximum power tracking state is taken, and the minimum value is input into the current inner loop.

[0036] Specifically, the output voltage loop, output current loop, and input voltage loop are calculated independently, and the minimum value among them is taken as the target value of the inner current loop. That is, the loop with the smallest loop result is the effective loop.

[0037] Step S33: Input the effective loop calculation result into the inner current loop, and output it to the PWM circuit after the inner current loop calculation to obtain the adjusted duty cycle.

[0038] The specific steps include: The calculation process for calculating the inner loop result of the output current using a PI controller is as follows: Current inner loop error value = target value - feedback value The target value is the minimum value among all output voltage loop calculation results and all output current loop calculation results.

[0039] Specifically, if the input power of a path is too high, the power distribution loop result decreases, the actual duty cycle decreases, and the corresponding input power decreases; if the input power of a path is too low, the power distribution loop result increases, the actual duty cycle increases, and the corresponding input power increases. This allows the input power of the path to eventually reach near the average input power, ultimately enabling all paths in constant voltage or constant current output states to achieve the effect of power equalization.

[0040] Specifically, for branches operating in constant voltage or constant current output mode, under the action of the power sharing loop, the power of the branch with higher power will decrease, and the power of the branch with lower power will increase, ultimately achieving the effect of power sharing among all branches in constant voltage or constant current output mode.

[0041] Specifically, the PI controller in steps S31, S32 and S33 uses a conventional proportional-integral controller for calculation, and achieves precise adjustment of the system by combining the immediate response of the current error (proportional term) and the historical accumulation of the error (integral term).

[0042] The basic formula for a PI controller is shown below: The mathematical expression for a PI controller in the continuous time domain is as follows: μ ( t )= Kp [ e ( t )+1 / Ti ∫ e ( t )dt] in: μ ( t ): Controller output; Kp : Proportional gain coefficient; Ti Integration time constant;e t Error signal (target value - actual value).

[0043] Step S40, the circuit in the MPPT maximum power tracking state, runs the maximum power tracking algorithm, and outputs the maximum output power that the photovoltaic panel can provide.

[0044] Specifically, the output power of the circuit in the MPPT maximum power tracking state in step S40 depends on the maximum power tracking algorithm and the characteristics of the photovoltaic panel itself, and does not participate in the power sharing process.

[0045] Step S50, if the output state of each single four-switch Buck-Boost step-up / down voltage circuit is switched, turn to step S20.

[0046] The specific steps include: Step S51, after the circuit in the MPPT maximum power tracking state is switched from the MPPT tracking state to the constant voltage or constant current output state, the number of circuits participating in power sharing is increased, the system repeatedly runs steps S20 and S30, and the power sharing among circuits is re-performed; Step S52, after the circuit in the constant voltage or constant current output state is switched from the constant voltage or constant current output state to the MPPT tracking state, the number of circuits participating in power sharing is reduced, the system repeatedly runs steps S20 and S30, and the power sharing among circuits is re-performed.

[0047] Specifically, the circuit in the constant voltage or constant current output state realizes power sharing of each circuit under the action of the power sharing loop, and the circuit in the MPPT tracking state outputs the maximum power of the photovoltaic panel under the action of the maximum power tracking algorithm, so the power of all circuits is automatically distributed.

[0048] In the above-mentioned control method for power automatic distribution of the multi-input DC-DC converter, the average input power of all circuits in the constant voltage or constant current output state is calculated, the input power of each input circuit is adjusted, under the action of the power sharing loop, the power of the circuit with large power is reduced, and the power of the circuit with small power is increased, so as to finally realize the effect of power sharing of all circuits in the constant voltage or constant current output state. Since there is a difference in the efficiency of the single four-switch Buck-Boost step-up / down voltage circuit of each circuit, the power distribution in the technical solution adjusts the input power of each circuit to achieve the effect of balancing the output power of each circuit. In the application of new energy power generation, the power balance capability supports the coordinated management of energy of different input sources, realizes efficient power transmission and multi-energy complementation, and improves the system energy utilization rate. The method of the application is simple, easy to implement, low in cost, and convenient to popularize.

[0049] ​It should be noted that the above only represents the preferred embodiments of the present application, and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A control method for multiple-input DC-DC converter power automatic distribution, characterized by, The method comprises the following steps: Step one, circuit configuration; a plurality of single-channel four-switch Buck-Boost step-up / down voltage circuits are combined into a multi-input DC-DC converter circuit; the input end of each single-channel four-switch Buck-Boost step-up / down voltage circuit is connected to an independent photovoltaic panel output circuit; Step two, calculating average input power; the number of all circuits in a constant voltage or constant current output state and the total input power of all circuits are counted, and the total input power is divided by the number of circuits to obtain the average input power; Step three, adjusting the input power of each input circuit; the power distribution loop operation result of a specific circuit in a constant voltage or constant current output state is calculated, the power distribution loop operation result is superimposed on the target value of the effective loop of the specific circuit, and the output result of the effective loop is transmitted to the current inner loop to determine the duty cycle of the specific circuit; Step four, the circuit in an MPPT maximum power tracking state runs a maximum power tracking algorithm, and outputs the maximum output power that can be provided by the photovoltaic panel; Step five, if the output state of each single-channel four-switch Buck-Boost step-up / down voltage circuit is switched, step two is turned to.

2. The control method of claim 1, wherein, Each single-channel four-switch Buck-Boost step-up / down voltage circuit comprises an output voltage loop VoutLoop, an output current loop IoutLoop, an input voltage loop VinLoop, a current inner loop IcsLoop and a power sharing loop PinShareLoop.

3. The control method of claim 1, wherein, The specific steps of calculating the average input power in step two comprise: Step 2.1, judging whether each four-switch Buck-Boost step-up / down voltage circuit is in an output voltage loop or an output current loop running state; Step 2.2, counting the number of all circuits in a constant voltage or constant current output state; Step 2.3, counting the total input power of all circuits in a constant voltage or constant current output state; Step 2.4, dividing the total input power by the number of all circuits in a constant voltage or constant current output state to obtain the average input power.

4. The control method of claim 1, wherein, The specific steps of adjusting the input power of each input circuit in step three comprise: Step 3.1, taking the average input power as a target value and the input power of the circuit as a feedback value, performing power distribution loop operation on the single-channel four-switch Buck-Boost step-up / down voltage circuit to obtain a power distribution loop operation result; Step 3.2, superimposing the power distribution loop operation result on the target value of the effective loop of the circuit in a constant voltage or constant current output state, and obtaining an effective loop operation result through effective loop calculation; Step 3.3, inputting the effective loop operation result into the current inner loop, and outputting to the PWM circuit after current inner loop operation to obtain an adjusted duty cycle.

5. The control method of claim 1, wherein, The output power of the circuit in an MPPT maximum power tracking state in step four depends on the maximum power tracking algorithm and the characteristics of the photovoltaic panel, and does not participate in the power sharing process.

6. The control method of claim 1, wherein, The specific steps after the output state of each single-channel four-switch Buck-Boost step-up / down voltage circuit is switched in step five comprise: Step 5.1, after the circuit in MPPT maximum power tracking state is switched from MPPT tracking state to constant voltage or constant current output state, the number of circuits participating in power sharing is increased, the system repeats steps two and three, and the power sharing among circuits is re-performed; Step 5.2, after the circuit in constant voltage or constant current output state is switched from constant voltage or constant current output state to MPPT tracking state, the number of circuits participating in power sharing is reduced, the system repeats steps two and three, and the power sharing among circuits is re-performed.

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