A control method for power automatic distribution of a multi-input DC-DC converter

Abstract

The application discloses a control method for power automatic distribution of a multi-input DC-DC converter, and comprises the following steps: a plurality of single-path four-switch Buck-Boost voltage-stabilizing circuits are combined to form a multi-input DC-DC converter circuit; average input power is calculated; output power of each input circuit is adjusted; power distribution loop operation results of circuits in constant-voltage or constant-current output states are calculated; the power distribution loop operation results are superimposed on target values of effective loops of the paths; output results of the effective loops are transmitted to current inner loops to determine duty cycles of the paths; circuits in MPPT (Maximum Power Point Tracking) states run maximum power tracking algorithms to output maximum output power that can be provided by photovoltaic panels of the paths; and if output states of the single-path four-switch Buck-Boost voltage-stabilizing circuits are switched, power is redistributed.

Description

Technical Field

[0001] This invention relates to the field of new energy control technology, specifically to a control method for automatic power distribution in a multi-input DC-DC converter. Background Technology

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

[0003] However, in a combined renewable energy power supply system, each renewable energy generation unit and energy storage unit requires an independent DC-DC converter to convert the electrical energy generated by each energy source into DC output, which is then connected in parallel to a common DC bus. To integrate the system topology and control structure, using a single multi-input DC-DC converter instead of multiple individual DC-DC converters not only simplifies the structure of the combined renewable energy power supply system but also reduces system operating costs. For example, in photovoltaic (PV) system applications, a single multi-input DC-DC converter can replace multiple individual DC-DC converters, still achieving the effect of equipping each PV panel with a power electronic converter that enables maximum power point tracking (MPPT), allowing each PV panel to output maximum power and thus achieving efficient operation of the PV system. However, in parallel systems, current unevenness can easily occur between modules, necessitating appropriate methods to achieve power distribution between modules. Summary of the Invention

[0004] In view of this, it is necessary to provide a control method for automatic power allocation of multi-input DC-DC converters that simplifies the structure of new energy combined power supply systems.

[0005] A control method for automatic power distribution in a multi-input DC-DC converter, the method comprising the following steps:

[0006] Step 1, Circuit Configuration: Combining multiple single-channel four-switch Buck-Boost step-up / step-down circuits into a multi-input DC-DC converter circuit; Connecting the input terminal of each single-channel four-switch Buck-Boost step-up / step-down circuit to an independent photovoltaic panel output circuit;

[0007] Step 2: Calculate the average input power; count the number of all circuits in constant voltage or constant current output state and the total input power of all circuits, divide the total input power by the number of circuits to obtain the average input power;

[0008] Step 3: Adjust the input power of each input circuit; calculate the power distribution loop calculation result of a specific circuit in constant voltage or constant current output state, superimpose the power distribution loop calculation result on the target value of the effective loop of the specific circuit, and transmit the output result of the effective loop to the inner current loop to determine the duty cycle of the specific circuit.

[0009] Step 4: For circuits in MPPT (Maximum Power Point Tracking) mode, run the maximum power point tracking algorithm and output the maximum output power that the photovoltaic panel can provide.

[0010] Step 5: If the output state of each single-channel four-switch Buck-Boost step-up / buck circuit changes, proceed to step 2.

[0011] Preferably, each of the single-channel four-switch Buck-Boost buck-boost circuits includes an output voltage loop VoutLoop, an output current loop IoutLoop, an input voltage loop VinLoop, an inner current loop IcsLoop, and a power sharing loop PinShareLoop.

[0012] Preferably, the specific steps for calculating the average input power in step two include:

[0013] Step 2.1: Determine whether each of the four-switch Buck-Boost step-up / step-down circuits is operating in either an output voltage loop or an output current loop state;

[0014] Step 2.2: Count the number of all circuits in constant voltage or constant current output state;

[0015] Step 2.3: Calculate the total input power of all circuits in constant voltage or constant current output state;

[0016] Step 2.4: Divide the total input power by the number of all circuits in constant voltage or constant current output state to obtain the average input power.

[0017] Preferably, the specific steps for adjusting the input power of each input circuit in step three include:

[0018] Step 3.1: Using the average input power as the target value and the input power of this circuit as the feedback value, perform a power distribution loop operation on the single-channel four-switch Buck-Boost buck-boost circuit of this circuit to obtain the power distribution loop operation result.

[0019] Step 3.2: Superimpose the power distribution loop calculation result onto the target value of the effective loop of the circuit in constant voltage or constant current output state, and obtain the effective loop calculation result after effective loop calculation.

[0020] Step 3.3: 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.

[0021] Preferably, the output power of the circuit in the MPPT (Maximum Power Point Tracking) state in step four depends on the maximum power point tracking algorithm and the characteristics of the photovoltaic panel itself, and does not participate in the power sharing process.

[0022] Preferably, the specific steps after the output state of each single-channel four-switch Buck-Boost buck-boost circuit in step five is switched include:

[0023] Step 5.1: After the circuit in the MPPT maximum power tracking state switches from the MPPT tracking state to the constant voltage or constant current output state, the number of circuits participating in power sharing increases. The system repeats steps two and three to redistribute the power among the circuits.

[0024] Step 5.2: After the circuit in constant voltage or constant current output state switches from constant voltage or constant current output state to MPPT tracking state, the number of circuits participating in power sharing decreases. The system repeats steps two and three to redistribute power among the circuits.

[0025] In the aforementioned control method for automatic power distribution in a multi-input DC-DC converter, the average input power of all circuits in constant voltage or constant current output states is calculated. The input power of each input circuit is then adjusted. Under the action of the power sharing loop, the power of circuits with excessive power is reduced, and the power of circuits with insufficient power is increased, ultimately achieving power sharing among all circuits in constant voltage or constant current output states. Since the efficiency of each single-channel four-switch Buck-Boost step-up / step-down circuit varies, the power distribution in this technical solution adjusts the input power of each channel to achieve a balanced output power across all channels. In the application of new energy power generation, this power balancing capability supports coordinated management of energy from different input sources, achieving efficient power transmission and multi-energy complementarity, thus improving system energy utilization. The method of this invention is simple, easy to implement, low in cost, and easy to promote. Attached Figure Description

[0026] Figure 1 This is a circuit diagram of a single-channel four-switch Buck-Boost buck-boost circuit according to an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the circuit structure of a multi-input DC-DC converter according to an embodiment of the present invention.

[0028] Figure 3 This is a power allocation control diagram of the automatic power allocation control method for multi-input DC-DC converters according to an embodiment of the present invention.

[0029] Figure 4 This is a flowchart of the control method for automatic power allocation of a multi-input DC-DC converter according to an embodiment of the present invention. Detailed Implementation

[0030] This embodiment takes the control method of automatic power allocation of a multi-input DC-DC converter as an example. The present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0031] Please see Figure 4 This invention illustrates a control method for automatic power allocation in a multi-input DC-DC converter, comprising the following steps:

[0032] Step S10, circuit configuration: Combine multiple single-channel four-switch Buck-Boost step-up / step-down circuits into a multi-input DC-DC converter circuit.

[0033] Preferably, the multi-input DC-DC converter circuit in step one includes multiple single-channel four-switch Buck-Boost buck-boost circuits, with each single-channel four-switch Buck-Boost buck-boost circuit having an independently configured input terminal, and the output terminals of the multiple single-channel four-switch Buck-Boost buck-boost circuits connected in parallel to the Vout output terminal.

[0034] Specifically, such as Figure 1 As shown, the single-channel four-switch Buck-Boost step-up / step-down circuit includes an input-side half-bridge, an output-side half-bridge, and an inductor L1. The inductor L1 is connected to the intermediate node between the input-side half-bridge and the output-side half-bridge and is used for energy transfer between the input side and the output side.

[0035] Specifically, such as Figure 2 As shown, in this embodiment, four single-channel four-switch Buck-Boost step-up / step-down circuits are arranged in parallel, the input terminals of the four single-channel four-switch Buck-Boost step-up / step-down circuits are independently set, and the output terminals of the four single-channel four-switch Buck-Boost step-up / step-down circuits are connected in parallel to the Vout output terminal, which is equipped with a load RL.

[0036] Specifically, the power distribution control method in this technical solution is not only applicable to Buck-Boost step-up / step-down circuits, but can also be extended to other circuits.

[0037] Preferably, the input terminal of each of the single-channel four-switch Buck-Boost step-up / step-down circuits is connected to an independent photovoltaic panel output circuit; each of the single-channel four-switch Buck-Boost step-up / step-down circuits includes an output voltage loop VoutLoop, an output current loop IoutLoop, an input voltage loop VinLoop, an inner current loop IcsLoop, and a power sharing loop PinShareLoop.

[0038] 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 to achieve power sharing, and the inner current loop IcsLoop ultimately outputs to the duty cycle.

[0039] Step S20, calculate the average input power; please refer to [link / reference]. Figure 3 The number of all circuits in constant voltage or constant current output state and the total input power of all circuits are counted. The total input power is divided by the number of circuits to obtain the average input power.

[0040] The specific steps include:

[0041] Step S21: Determine whether each of the four-switch Buck-Boost step-up / step-down circuits is in operation with either an output voltage loop or an output current loop.

[0042] Step S22: Count the number of all circuits in constant voltage or constant current output state.

[0043] Step S23: Calculate the total input power of all circuits in constant voltage or constant current output state.

[0044] Step S24: Divide the total input power by the number of all circuits in constant voltage or constant current output state to obtain the average input power.

[0045] Step S30: Adjust the input power of each input circuit; calculate the power distribution loop calculation result of a specific circuit in constant voltage or constant current output state, superimpose the power distribution loop calculation result on the target value of the effective loop of the specific circuit, and transmit the output result of the effective loop to the inner current loop to determine the duty cycle of the specific circuit.

[0046] The specific steps include:

[0047] Step S31: Using the average input power as the target value and the input power of this circuit as the feedback value, perform a power distribution loop operation on the single-channel four-switch Buck-Boost step-up / buck circuit of this circuit to obtain the power distribution loop operation result.

[0048] Specifically, the objective value of the power distribution loop operation is the average input power, and the feedback value is the input power of that channel. A conventional PI controller is used for calculation to obtain the power distribution loop operation result. The specific calculation steps are as follows:

[0049] Power distribution loop error value = target value - feedback value

[0050] The target value is the average input power of all circuits in constant voltage or constant current output state.

[0051] Specifically, the power distribution loop calculation result is the adjustment component of the target values ​​of the output voltage loop and the output current loop, representing the ability to regulate the output voltage or output current.

[0052] Step S32: The power distribution loop calculation result is superimposed on the target value of the effective loop of the circuit in constant voltage or constant current output state. After effective loop calculation, the effective loop calculation result is obtained.

[0053] Specifically, if the single-channel four-switch Buck-Boost step-up / step-down circuit is a constant voltage output circuit and the effective loop is the output voltage loop, then the power distribution loop calculation result is superimposed on the target value of the output voltage loop; if the single-channel four-switch Buck-Boost step-up / step-down circuit is a constant current output circuit and the effective loop is the output current loop, then the power distribution loop calculation result is superimposed on the target value of the output current loop.

[0054] Specifically, the effective loop calculation for constant voltage or constant current output includes output voltage loop calculation and output current loop calculation, and the calculation steps are as follows:

[0055] Step S32.1: The power distribution loop calculation result is superimposed on the output voltage loop. The calculation process of using a PI controller to calculate the output voltage loop result is as follows:

[0056] Output voltage loop error value = Actual output voltage target value - Feedback value;

[0057] Wherein, the actual output voltage target value = the current output voltage target value + the power distribution loop calculation result;

[0058] Step S32.2: The power distribution loop calculation result is superimposed on the output current loop. The calculation process of the output current loop result using the PI controller is as follows:

[0059] Output current loop error value = Actual output current target value - Feedback value

[0060] Wherein, the actual output current target value = the current output current target value + the power distribution loop calculation result;

[0061] Step S32.3, the calculation process of the input voltage loop result using the PI controller is as follows:

[0062] Input voltage loop error value = Feedback value - Input voltage loop target value

[0063] The target value for the input voltage loop is the actual input voltage of the circuit in the MPPT (Maximum Power Tracking) state.

[0064] Step S32.3: Take the minimum value among all output voltage loop calculation results, all output current loop calculation results, and all circuit calculation results in MPPT maximum power point tracking state, and input the minimum value into the inner current loop.

[0065] 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.

[0066] 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.

[0067] The specific steps include:

[0068] The calculation process for calculating the inner loop result of the output current using a PI controller is as follows:

[0069] Current inner loop error value = target value - feedback value

[0070] The target value is the minimum value among all output voltage loop calculation results and all output current loop calculation results.

[0071] 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.

[0072] 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.

[0073] 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).

[0074] The basic formula for a PI controller is shown below:

[0075] The mathematical expression for a PI controller in the continuous time domain is as follows:

[0076] μ ( t )= Kp [ e ( t )+1 / Ti ∫ e ( t )dt]

[0077] in:

[0078] μ ( t ): Controller output; Kp : Proportional gain coefficient; Ti Integration time constant; e ( t Error signal (target value - actual value).

[0079] In step S40, the circuit in the MPPT (Maximum Power Point Tracking) state runs the maximum power point tracking algorithm and outputs the maximum output power that the photovoltaic panel can provide.

[0080] Specifically, the output power of the circuit in the MPPT maximum power point tracking state in step S40 depends on the maximum power point tracking algorithm and the characteristics of the photovoltaic panel itself, and does not participate in the power sharing process.

[0081] In step S50, if the output state of each single-channel four-switch Buck-Boost step-up / buck circuit changes, proceed to step S20.

[0082] The specific steps include:

[0083] Step S51: After the circuit in the MPPT maximum power tracking state switches from the MPPT tracking state to the constant voltage or constant current output state, the number of circuits participating in power sharing increases. The system repeats steps S20 and S30 to redistribute power among the circuits.

[0084] In step S52, after the circuit in constant voltage or constant current output state switches from constant voltage or constant current output state to MPPT tracking state, the number of circuits participating in power sharing decreases. The system repeats steps S20 and S30 to redo the power sharing among the circuits.

[0085] Specifically, circuits in constant voltage or constant current output state achieve power equalization among all circuits under the action of the power sharing loop, while circuits in MPPT tracking state output the maximum power of the photovoltaic panel under the action of the maximum power tracking algorithm. Therefore, automatic power distribution of all circuits is realized.

[0086] In the aforementioned control method for automatic power distribution in a multi-input DC-DC converter, the average input power of all circuits in constant voltage or constant current output states is calculated. The input power of each input circuit is then adjusted. Under the action of the power sharing loop, the power of circuits with excessive power is reduced, and the power of circuits with insufficient power is increased, ultimately achieving power sharing among all circuits in constant voltage or constant current output states. Since the efficiency of each single-channel four-switch Buck-Boost step-up / step-down circuit varies, the power distribution in this technical solution adjusts the input power of each channel to achieve a balanced output power across all channels. In the application of new energy power generation, this power balancing capability supports coordinated management of energy from different input sources, achieving efficient power transmission and multi-energy complementarity, thus improving system energy utilization. The method of this invention is simple, easy to implement, low in cost, and easy to promote.

[0087] It should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can be modified and varied in various ways. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention should be included within the scope of protection of the present invention.

Claims

1. A control method for automatic power distribution in a multi-input DC-DC converter, characterized in that, The method includes the following steps: Step 1, Circuit Configuration: Combine multiple single-channel four-switch Buck-Boost step-up / step-down circuits into a multi-input DC-DC converter circuit; Step 2: Calculate the average input power; count the number of all circuits in constant voltage or constant current output state and the total input power of all circuits in constant voltage or constant current output state, divide the total input power by the number of circuits to obtain the average input power; Step 3: Adjust the input power of each input circuit; calculate the power distribution loop calculation result of each circuit in constant voltage or constant current output state, and superimpose the power distribution loop calculation result on the target value of the effective loop of the circuit. The output result of the effective loop is transmitted to the inner current loop to determine the duty cycle of the circuit. Step 4: For circuits in MPPT (Maximum Power Point Tracking) mode, run the maximum power point tracking algorithm and output the maximum output power that the photovoltaic panel can provide. Step 5: If the output state of each single-channel four-switch Buck-Boost step-up / buck circuit changes, proceed to step 2.

2. The control method for automatic power allocation in a multi-input DC-DC converter as described in claim 1, characterized in that, The input of each of the single-channel four-switch Buck-Boost step-up / step-down circuits is connected to an independent photovoltaic output circuit; each of the single-channel four-switch Buck-Boost step-up / step-down circuits includes an output voltage loop VoutLoop, an output current loop IoutLoop, an input voltage loop VinLoop, an inner current loop IcsLoop, and a power sharing loop PinShareLoop.

3. The control method for automatic power allocation in a multi-input DC-DC converter as described in claim 1, characterized in that, The specific steps for calculating the average input power in step two include: Step 2.1: Determine whether each of the single-channel four-switch Buck-Boost step-up / buck circuits is in the output voltage loop or output current loop operation state; Step 2.2: Count the number of all circuits in constant voltage or constant current output state; Step 2.3: Calculate 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 all circuits in constant voltage or constant current output state to obtain the average input power.

4. The control method for automatic power allocation in a multi-input DC-DC converter as described in claim 1, characterized in that, The specific steps for adjusting the input power of each input circuit in step three include: Step 3.1: Using the average input power as the target value and the input power of the single-channel four-switch Buck-Boost buck-boost circuit as the feedback value, perform a power distribution loop operation on the single-channel four-switch Buck-Boost buck-boost circuit to obtain the power distribution loop operation result. Step 3.2: Superimpose the power distribution loop calculation result onto the target value of the effective loop of the circuit in constant voltage or constant current output state, and obtain the effective loop calculation result after effective loop calculation. Step 3.3: 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.

5. The control method for automatic power allocation in a multi-input DC-DC converter as described in claim 1, characterized in that, The output power of the circuit in the MPPT (Maximum Power Point Tracking) state in step four depends on the maximum power point tracking algorithm and the characteristics of the photovoltaic panel itself, and does not participate in the power sharing process.

6. The control method for automatic power allocation in a multi-input DC-DC converter as described in claim 1, characterized in that, The specific steps after the output state of each single-channel four-switch Buck-Boost buck-boost circuit in step five is switched include: Step 5.1: After the circuit in the MPPT (Maximum Power Tracking) state switches from the MPPT state to the constant voltage or constant current output state, the number of circuits participating in power sharing increases. The system repeats steps two and three to redistribute power among the circuits. Step 5.2: After the circuit in constant voltage or constant current output state switches from constant voltage or constant current output state to MPPT maximum power tracking state, the number of circuits participating in power sharing decreases. The system repeats steps two and three to redistribute power among the circuits.

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